全文获取类型
收费全文 | 3609篇 |
免费 | 138篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 65篇 |
综合类 | 3篇 |
化学工业 | 652篇 |
金属工艺 | 118篇 |
机械仪表 | 79篇 |
建筑科学 | 151篇 |
矿业工程 | 12篇 |
能源动力 | 64篇 |
轻工业 | 405篇 |
水利工程 | 25篇 |
石油天然气 | 8篇 |
无线电 | 266篇 |
一般工业技术 | 649篇 |
冶金工业 | 785篇 |
原子能技术 | 23篇 |
自动化技术 | 451篇 |
出版年
2023年 | 29篇 |
2022年 | 20篇 |
2021年 | 51篇 |
2020年 | 54篇 |
2019年 | 28篇 |
2018年 | 88篇 |
2017年 | 99篇 |
2016年 | 92篇 |
2015年 | 82篇 |
2014年 | 122篇 |
2013年 | 197篇 |
2012年 | 173篇 |
2011年 | 183篇 |
2010年 | 157篇 |
2009年 | 143篇 |
2008年 | 147篇 |
2007年 | 123篇 |
2006年 | 104篇 |
2005年 | 108篇 |
2004年 | 91篇 |
2003年 | 80篇 |
2002年 | 93篇 |
2001年 | 68篇 |
2000年 | 71篇 |
1999年 | 59篇 |
1998年 | 236篇 |
1997年 | 147篇 |
1996年 | 95篇 |
1995年 | 80篇 |
1994年 | 66篇 |
1993年 | 63篇 |
1992年 | 36篇 |
1991年 | 31篇 |
1990年 | 29篇 |
1989年 | 24篇 |
1988年 | 26篇 |
1987年 | 34篇 |
1986年 | 26篇 |
1985年 | 23篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1980年 | 23篇 |
1979年 | 16篇 |
1977年 | 19篇 |
1976年 | 60篇 |
1975年 | 26篇 |
1974年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有3756条查询结果,搜索用时 15 毫秒
71.
Anne Stöbener Mario Fabuel Ortega Christoph J. Bolten Edwin Ananta Shantha Nalur Andreas Liese 《International Journal of Food Science & Technology》2020,55(3):1265-1271
Partial glycerides are widely used ingredients in confectionery products that can be produced from natural fats. In a biocatalytic partial hydrolysis of cocoa butter and palm oil fractions, a product mixture containing 1.5% monoglycerides and 5.5% diglycerides intended for the use in confectionery products was created. This study is a proof of principle that shows the feasibility of monitoring the biocatalytic partial hydrolysis of these two natural fats in situ with ATR-FTIR spectroscopy. An economic approach was utilised for calibration since partial glyceride calibration standards are costly and poorly available. The released compounds were quantified by means of chemometric modelling, and the model was validated with gas chromatography. Resulting root mean square errors were in the low per cent range. Additionally, the results indicate that distinction of the released free fatty acids is possible with ATR-FTIR spectroscopy. 相似文献
72.
Cliff K. Riley Andrew O. Wheatley Ishmael Hassan Mohammed H. Ahmad Errol Y. St. A. Morrison Helen N. Asemota 《Starch - St?rke》2004,56(2):69-73
Starch granules from Round leaf yellow yam, Negro yam, Sweet yam, Bitter yam and Chinese yam grown in Jamaica were isolated and characterized. The amylose content, granular size, crystallinity, and digestibility by α‐amylase were determined. The granules obtained were of three crystalline types. Round leaf yellow yam, Negro yam and Sweet yam were found to be type‐B, while Chinese yam and Bitter yam were type‐C and type‐A, respectively. Round leaf yellow yam had the highest amylose content (26.5%) while Chinese yam had the lowest (11.1%). The granule size varied between 1–3 μm for Chinese yam and 16–42 μm for Round leaf yellow yam. Significant variations in digestibility of the granules were observed. Raw starches from Chinese yam and Bitter yam were the most susceptible to α‐amylase digestion (porcine pancreatic α‐amylase, pH 5.5, 0.02% CaCl2, 40°C, 24 h) with 21.27 ± 0.01% and 18.11 ± 0.02% degradation, respectively, while Round leaf yellow yam, Negro yam and Sweet yam starches were the least susceptible, with 13.74 ± 0.03%, 14.98 ± 0.08%, and 15.32 ± 0.04% enzymatic degradation, respectively. 相似文献
73.
Mihaela Turturică Nicoleta Stănciuc Gabriela Bahrim Gabriela Râpeanu 《Food and Bioprocess Technology》2016,9(10):1706-1715
Five anthocyanins were detected in the sweet cherry extract as follows: cyanidin 3-rutinoside, cyanidin 3-glucoside, peonidin 3-rutinoside, peonidin 3-glucoside, and pelargonidin 3-rutinoside, whereas the cyanidin 3-rutinoside was found to be in the highest amount. The effect of thermal treatment on the degradation of the polyphenolic compounds in sweet cherry extract was investigated in the range of 70–120 °C by means of fluorescence spectroscopy and spectrophotometric techniques. The fluorescence spectra were dominated by emission bands with maximum ranging from 356 nm at 25 °C to 350 nm at 110 °C. The heating of sweet cherry extract resulted in structural changes that led to a significant decrease in fluorescence intensity when increasing temperature. Degradation rate constants were estimated using a fractional conversion kinetic model. The activation energy values revealed a higher-temperature dependence of antioxidant activity, followed by anthocyanins, total polyphenols, and total flavonoids. 相似文献
74.
Vasilis P. Valdramidis Claudine Péroval Stéphane Portanguen Anke J. Verhulst Jan F. M. Van Impe Annemie H. Geeraerd Alain Kondjoyan 《Food and Bioprocess Technology》2008,1(3):285-296
Surface pasteurization is one of the decontamination treatments that can contribute to better preservation of meat products retaining most of their quality characteristics relatively intact if compared with the raw products. The current research compares the kinetics of free-floating and surface attached Listeria innocua cells by using integrated microbial and heat transfer modelling approaches. Surface pasteurization treatments are applied on a (abiotic) Teflon® model system in a novel steam surface decontamination rig. The experimental set-up prevented following four technological aspects to occur, (1) cold purge migration to the surface during the heating process, (2) inactivation kinetics of a cocktail of microbes, (3) protective effect of food components, and (4) physical distribution of bacteria throughout the depth of the product skin. Microbial load predictions are performed based on the inactivation parameters obtained during free-floating cell experiments. These predictions, when compared with the microbial data of the surface treatments, prove that the surface attached cells were much more heat resistant, despite the experimental set-up preventing the aforementioned (technological) events to occur. Indeed, surface attached cells can have different physiological/phenotypical/genetical characteristics, such as cell aggregations, colony formations, presence of flagella. In a final step, three techniques are implemented to evaluate mathematically the kinetics of the surface attached cells. Overall, this research’s significance is lying in the quantitative assessment of microbial heat resistance. The technological reasons underlying the increased microbial heat resistance on biotic and abiotic surfaces should be reevaluated, taking into account possible physiological/phenotypical/genetical characteristics. 相似文献
75.
Elvis Maujean Stéphane Desobry Guillaume Gillet Nicolas Poupard Isabelle Desjardins-Lavisse Sylvie Desobry-Banon 《International Journal of Food Science & Technology》2021,56(5):2443-2451
In this study, preservation of spirulina using the new pressurised cryogenic nitrogen technology (PCN) was compared to classical methods used in laboratories and industry. Spirulina morphology was better preserved by PCN compared to unpressurised cryogeny and classical freezing at −20 °C that led to cells fragmentation. A 25% loss of Phycocyanin-C content against 60% were measured after 98 days storage for 6-Bar PCN process and frozen samples, respectively. The Total AntiOxidant Power (PAOT Liquid Technology®) was used for determination of total antioxidant and oxidant power of spirulina extracts. PAOT value of PCN samples was 50% higher than the frozen sample. From ABTS measurements on PCN spirulina fractions sonicated or not, it was suggested that pressurisation at 6 bars allowed a better preservation of free antioxidants (outside the cells) due to replacement of oxygen by nitrogen in the frozen beads. After dehydration, phycocyanin-C content variation during storage at 20 °C and 33% RH showed higher loss for freeze-dried spirulina treated at 0 compared to 6 Bars. 相似文献
76.
St Rehbein W. Haupt R. Schm?schke und H. Rosigkeit 《Zeitschrift für Jagdwissenschaft》1993,39(1):1-14
Zusammenfassung An 24 natürlich infizierten Damhirschen (Alter 9–15 Monate) wurde die anthelminthische Wirksamkeit von dermal appliziertem
Ivermectin (0,5 mg/kg KM) gegenüber Magen-Darm-Nematoden und Lungenwürmern geprüft. Die Tiere der Gruppe I (n=8) wurden 4mal
im Abstand von jeweils 6 Wochen, die der Gruppe II (n=8) 2mal im Abstand von jeweils 12 Wochen behandelt. 8 Tiere (Gruppe
III) blieben unbehandelt. Zu den Behandlungsterminen sind alle Tiere gefangen, gewogen und koprologisch untersucht sowie 9
Wochen nach der letzten Behandung der Gruppe I get?tet und gewogen worden. Die Magen-Darm-Kan?le und die Lungen wurden vollst?ndig
parasitologisch untersucht. Durch die dermale Verabreichung von Ivermectin im Abstand von 6 Wochen (Gruppe I) lie? sich die
Ausscheidung vonDictyocaulus-Larven und Haarwurm-Eiern im gesamten Untersuchungszeitraum vollst?ndig unterdrücken. Bei Ausdehnung des Dosierungsintervalls
auf 12 Wochen (Gruppe II) konnten bei einigen TierenCapillaria-Eier, nicht jedoch Lungenwurm-Larven, im Kot nachgewiesen werden (Tabelle 2). Eine Beurteilung der Wirksamkeit von Ivermectin
gegenüber Magen-Darm-Strongylida anhand des koprologischen Befundes war aufgrund einer zu geringen Eiausscheidung nicht m?glich.
Die nach der T?tung der Tiere ermittelten Befallsintensit?ten des Magen-Darm-Kanals und der Lunge mit Helminthen (Tabelle
3) ergaben keine signifikanten Unterschiede zwischen den Spie?ern der behandelten Gruppen I und II sowie der unbehandelten
Gruppe III. Die Ergebnisse der parasitologischen Teilsektion und der Kontrollw?gungen zeigen, da? ein geringgradiger Befall
mit Helminthen keinen me?baren Einflu? auf K?rpermasseentwicklung, Schlachtk?rperwarmmasse sowie Schlachtausbeute der Tiere
hat (Tabelle 4).
Das Erscheinen der Abhandlung in dem vorliegenden Umfang war durch Einsatz eines Druckkostenzuschusses des Deutschen Jagdschutz-Verbandes m?glich, für dessen Gew?hrung verbindlich gedankt wird. — Die Schriftleitung 相似文献
Investigation on the efficacy of IVOMEC? pour-on against lungworms and gastrointestinal nematodes in enclosed fallow deer and influence of regular anthelmintic treatment on performance
Summary A trial was conducted to determine the anthelminthic efficacy of topically administered ivermectin at 0,5 mg/kg b.w. in 24 male fallow deer (9 to 15 months old) against gastrointestinal nematodes and lungworms. Eight deer (Group I) received the topical treatment 4 times at six week intervals and 8 deer (Group II) 2 times at twelve week intervals. Group III (8 deer) was the control group. On the treatment days all deer were weighed, faecal samples were collected per rectum and examined. Nine weeks after the last treatment of Gr. I all animals were killed and weighed. Gastrointestinal tracts and lungs were removed and total worm counts were carried out. At treatment intervals of 6 weeks (Gr. I) faecal counts forDictyocaulus larvae and eggs ofCapillaria were undetectable. At dosing intervals of 12 weeks few animals showed an egg output ofCapillaria bovis but larvae of lungworms were not observed in their faeces (Tab. 2). The small egg output of gastrointestinal Strongylida in this trial prevented true estimates of the efficacy of ivermectin. Nine weeks after the last treatment the total worm counts of the gastrointestinal tracts and lungs showed no significant differences between treated Groups I and II and untreated controls (Tab. 3). The results of the parasitological examination at slaughter and the weighing showed that a light worm burden has no measurable effects on body carcass weights (Tab. 4).
De l'efficacité de l'IVOMEC? — Pour-On contre les vers pulmonaires et les vers gastro-intestinaux chez le Daim en enclos
Résumé Sur 24 daims males agés de 9 à 15 mois, naturellement infectés, on a testé l'efficacité anthelminthique de l'lvermectine (0,5 mg/kg de MC) contre les nématodes gastro-intestinaux et les vers pulmonaires. Les animaux du groupe 1 (n=8) furent traités à 4 reprises à 6 semaines d'intervalle, ceux du groupe II (n=8) à 2 reprises à 12 semaines d'intervalle. 8 animaux (Graphique III) ne furent pas traités. Au moment du traitement, tous les animaux ont été capturés, pesés et soumis à une analyse coprologique; 9 semaines après le dernier traitement du groupe I, ils furent tués et pesés. Les conduits gastrointestinaux ainsi que les poumons furent soumis à un examen parasitologique complet. L'administration par voie cutanée d'lvermectine de 6 en 6 semaines (Groupe I) permit un arrêt complet de l'expulsion de larves deDictyocaulus et d'œufs de strongles tout au long de la période expérimentale. En espa?ant les applications de 12 en 12 semaines (Groupe II), on put déceler, dans les fèces de quelques animaux, des œufs deCapillaria mais non des larves de vers pulmonaires (Tableau 2). Une appréciation de l'efficacité de l'lvermectine vis-à-vis des strongles gastro-intestinaux ne fut pas possible. Les degrés de contamination par des Helminthes ne donnèrent pas lieu à des différences significatives post mortem au niveau du conduit gastro-intestinal et des poumons (Tableau 3), tant parmi les daguets des groupes traités l et il que parmi les sujets non traités du Groupe III. Les résultats des examens parasitologiques ainsi que les pesées de contr?le montrent qu'une atteinte modérée par les Helminthes n'exerce pas une influence significative sur le développement de la masse corporelle, sur les mesures de carcasse de même que sur le rendement à l'abattage des animaux (Tableau 4).
Das Erscheinen der Abhandlung in dem vorliegenden Umfang war durch Einsatz eines Druckkostenzuschusses des Deutschen Jagdschutz-Verbandes m?glich, für dessen Gew?hrung verbindlich gedankt wird. — Die Schriftleitung 相似文献
77.
Vergleich der Extrakte und des Lignins aus frischem und gelagertem Kiefernholz (Pinus sylvestris L.)
The degradation processes of the extractives of pine wood caused by aging are only noticeable in the heartwood. In seasoned sapwood the percentages of the water extracts and the cyclohexane-ethanol extract increase compared with the green sample; the alkali extracts, however, do not vary. The contents of acid lignin as well as the UV and IR spectra of MWL do not show differences. The amount of OCH3/C9 is in all samples 0.96, but the degree of oxidation is higher in the seasoned wood than in the green one. 相似文献
78.
The capabilities of Rapid Scan, a system of automated reflectance microscopy, has been extended to the actual mapping of petrographic variation across polished coal surfaces. This is accomplished through computer control of a microscope stepping stage and the storage of binary reflectance data on disc in a matrix form which permits the proper spatial arrangement of values to be re-created. The maps depict lithotype variation, and the distribution of mineral occurrences, cracks and cleat. An image processor can be employed in further map analysis such as the compilation of reflectance profiles from selected areas. 相似文献
79.
Corbière Morot-Bizot S Leroy S Talon R 《International journal of food microbiology》2006,108(2):210-217
The level and the diversity of the staphylococcal community occurring in the environment and meat products of a small unit manufacturing traditional dry fermented sausages were investigated at two seasons: winter and spring. Gram-positive cocci were enumerated and a collection of 412 Staphylococcus isolates was made. Multiplex PCR, pulse-field gel electrophoresis (PFGE) and sequencing of the sodA gene were used to identify and characterize the isolates. High counts of Staphylococcus were found in final traditional sausages, reaching about 6 log CFU/g in winter and about 8 log CFU/g in spring. In the environment, the counts varied from 2 log to 7 log/100 cm(2), the higher colonisation being observed on the surface of the drying and cold rooms, cutting tables and the butcher's block. The combination of the three methods allowed the identification of seven species of Staphylococcus in spring and five in winter. S. equorum and S. succinus dominated both in environment and in meat products, 49% and 33% of the isolates, respectively. The other identified species were in decreasing order S. saprophyticus (6%), S. xylosus (5%), S. carnosus (5%), S. simulans (1%) and S. warneri (1%). The two species S. xylosus and S. carnosus were sporadically isolated during the spring. PFGE allowed the assignment of S. equorum to eight pulsotypes showing a wide diversity among this species. But the entire environment and the meat products were dominated by one pulsotype. For S. succinus, three pulsotypes were found with one dominant mainly isolated during the spring sampling. This study highlighted the diversity of staphylococci isolated in the environment and the meat products of a small processing unit manufacturing traditional dry fermented sausages. The S. equorum and S. succinus species rarely described in meat products and never in the environment had great capacity to colonise the entire small processing unit and the meat products. 相似文献
80.
Bastviken D Sandén P Svensson T Ståhlberg AC Magounakis M Oberg G 《Environmental science & technology》2006,40(9):2977-2982
The common assumption that chloride (Cl-) is conservative in soils and can be used as a groundwater tracer is currently being questioned, and an increasing number of studies indicate that Cl- can be retained in soils. We performed lysimeter experiments with soil from a coniferous forest in southeast Sweden to determine whether pore water residence time and nitrogen and Cl- loads affected Cl- retention. Over the first 42 days there was a net retention of Cl- with retention rates averaging 3.1 mg CI- m(-2) d(-1) (68% of the added Cl- retained over 42 days). Thereafter, a net release of Cl- at similar rates was observed for the remaining experimental period (85 d). Longer soil water residence time and higher Cl- load gave higher initial retention and subsequent release rates than shorter residence time and lower Cl- load did. Nitrogen load did not affect Cl transformation rates. This study indicates that simultaneous retention and release of Cl- can occur in soils, and that rates may be considerable relative to the load. The retention of Cl- observed was probably due to chlorination of soil organic matter or ion exchange. The cause of the shift between net retention and net release is unclear, but we hypothesize that the presence of O2 or the presence of microbially available organic matter regulates Cl- retention and release rates. 相似文献