全文获取类型
收费全文 | 1928篇 |
免费 | 65篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 60篇 |
综合类 | 5篇 |
化学工业 | 453篇 |
金属工艺 | 63篇 |
机械仪表 | 34篇 |
建筑科学 | 95篇 |
矿业工程 | 18篇 |
能源动力 | 49篇 |
轻工业 | 299篇 |
水利工程 | 14篇 |
石油天然气 | 3篇 |
无线电 | 82篇 |
一般工业技术 | 292篇 |
冶金工业 | 280篇 |
原子能技术 | 13篇 |
自动化技术 | 235篇 |
出版年
2022年 | 28篇 |
2021年 | 36篇 |
2020年 | 18篇 |
2019年 | 20篇 |
2018年 | 40篇 |
2017年 | 24篇 |
2016年 | 48篇 |
2015年 | 46篇 |
2014年 | 45篇 |
2013年 | 70篇 |
2012年 | 56篇 |
2011年 | 87篇 |
2010年 | 73篇 |
2009年 | 66篇 |
2008年 | 64篇 |
2007年 | 81篇 |
2006年 | 44篇 |
2005年 | 53篇 |
2004年 | 41篇 |
2003年 | 43篇 |
2002年 | 40篇 |
2001年 | 32篇 |
2000年 | 27篇 |
1999年 | 37篇 |
1998年 | 61篇 |
1997年 | 47篇 |
1996年 | 37篇 |
1995年 | 34篇 |
1994年 | 28篇 |
1993年 | 33篇 |
1992年 | 30篇 |
1991年 | 29篇 |
1990年 | 28篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 26篇 |
1976年 | 21篇 |
1975年 | 26篇 |
1974年 | 15篇 |
1973年 | 15篇 |
排序方式: 共有1995条查询结果,搜索用时 15 毫秒
161.
Mirjam Frischknecht Theodorus H.E. Meuwissen Beat Bapst Franz R. Seefried Christine Flury Dorian Garrick Heidi Signer-Hasler Christian Stricker Anna Bieber Ruedi Fries Ingolf Russ Johann Sölkner Alessandro Bagnato Birgit Gredler-Grandl 《Journal of dairy science》2018,101(2):1292-1296
The accuracy of genomic prediction determines response to selection. It has been hypothesized that accuracy of genomic breeding values can be increased by a higher density of variants. We used imputed whole-genome sequence data and various single nucleotide polymorphism (SNP) selection criteria to estimate genomic breeding values in Brown Swiss cattle. The extreme scenarios were 50K SNP chip data and whole-genome sequence data with intermediate scenarios using linkage disequilibrium-pruned whole-genome sequence variants, only variants predicted to be missense, or the top 50K variants from genome-wide association studies. We estimated genomic breeding values for 3 traits (somatic cell score, nonreturn rate in heifers, and stature) and found differences in accuracy levels between traits. However, among different SNP sets, accuracy was very similar. In our analyses, sequence data led to a marginal increase in accuracy for 1 trait and was lower than 50K for the other traits. We concluded that the inclusion of imputed whole-genome sequence data does not lead to increased accuracy of genomic prediction with the methods. 相似文献
162.
Dr. Inguna Goba Dr. David Goricanec Dominik Schum Dr. Matthias Hillenbrand Prof. Andreas Plückthun Prof. Dr. Franz Hagn 《Chembiochem : a European journal of chemical biology》2021,22(1):139-146
G protein-coupled receptors (GPCRs) are key players in mediating signal transduction across the cell membrane. However, due to their intrinsic instability, many GPCRs are not suitable for structural investigations. Various approaches have been developed in recent years to remedy this situation, ranging from the use of more native membrane mimetics to protein-stabilization methods. The latter approach typically results in GPCRs that contain various numbers of mutations. However, probing the functionality of such variants by in vitro and in vivo assays is often time consuming. In addition, to validate the suitability of such GPCRs for structural investigations, an assessment of their conformation state is required. NMR spectroscopy has been proven to be suitable to probe the conformation state of GPCRs in solution. Here, by using chemical labeling with an isotope-labeled methyl probe, we show that the activity and the conformation state of stabilized neurotensin receptor 1 variants obtained from directed evolution can be efficiently assayed in 2D NMR experiments. This strategy enables the quantification of the active and inactive conformation states and the derivation of an estimation of the basal as well as agonist-induced activity of the receptor. Furthermore, this assay can be used as a readout when re-introducing agonist-dependent signaling into a highly stabilized, and thus rigidified, receptor by mutagenesis. This approach will be useful in cases where low production yields do not permit the addition of labeled compounds to the growth medium and where 1D NMR spectra of selectively 19F-labeled receptors are not sufficient to resolve signal overlap for a more detailed analysis. 相似文献
163.
Heat transport and void fraction in granulated debris 总被引:1,自引:0,他引:1
The paper discusses the boiling heat transfer from a porous bed with internal heat sources and refers to the configuration in a nuclear reactor after a partial core melt. The flow of coolant, the temperature and the local liquid/vapor distribution were investigated in a two-dimensional configuration. Experiments were conducted using monodisperse beds as well as a mixture of two different particle sizes with a total porosity below 20%. In some tests the bed was supported by a shell of porous material to create a gap along the bottom of the test container. Water was used for tests up to 9% of the critical pressure, while other tests were made with R134a up to 44% of the critical pressure. The maximum heating rate realized inductively was 730 kW/m2. The experiments have been compared to analytical results with a one-dimensional approach.It is shown that in contrary to the situation in small cylindrical configurations the heat transfer was increased by large buoyancy driven convective flows. If there was a gap along the container bottom an additional flow of liquid improved the coolability of the bottom region even if the upper part of the particle bed was already overheated. In case of high density ratios (water at low pressure), the measurements indicated a strong enhancement of the coolant flow above a certain minimum heating rate resulting in decreasing vapor fraction values which were nearly independent of the system pressure. This was assumed to be caused by the appearance of vertical channels through which the vapor could flow through the particle bed. 相似文献
164.
Karlheinz Schaub Knut Berg Gabriele Winter Rolf Ellegast Ulrich Glitsch Hans Jürgen Ottersbach Matthias Jger Gerhard Franz 《International Journal of Industrial Ergonomics》2007,37(11-12):883
Increasingly in the recent years, passengers’ services are extended into the ascent and descent flight phases on short distance flights. Trolleys containing the required meal and beverage items are used for these service operations and pushed or pulled along the aisles of the aircraft. Flight attendants reported about increased musculo-skeletal disorders and had been complaining about high physical workload from handling trolleys. In order to ensure acceptable load levels for pushing or pulling operations of trolleys, the physical capabilities of the collective “flight attendants” had been investigated by means of force measurements at maximum voluntary contraction (MVC) level and associated relevant anthropometrical and biometrical data. CEN and ISO standards as well as international and national German methods were used to derive recommended force limits for pushing/pulling operations with respect to the physical capabilities of the target group “flight attendants”. Comparing these recommended limits with the force requirements per shift under various conditions of trolley handlings (inclination of the floor, type and weight of trolley, mode of handling, frequency of operation) showed that especially for higher floor inclinations and trolley weights, flight attendants work (substantially) above recommended limits. It became also apparent that the handling of half-size trolleys is unexpectedly high demanding due to high vertical force components, caused by the unfavorable location of their center of gravity.
Relevance to industry
On short-distance flights, passengers’ services are performed by means of trolleys from the ascent to the descent flight phases. Flight attendants had been complaining about high physical workload. This study offers recommendations on maximum force limits for the handling of trolleys with respect to the muscular capacities and work situations of flight attendants on short-distance flights. 相似文献165.
Galen R. Hatfield Beili Li Willis B. Hammond Franz Reidinger John Yamanis 《Journal of Materials Science》1990,25(9):4032-4035
Lanthanum silicon nitride (LaSi3N5) powder has been prepared under the relatively mild conditions of 1400 ° C and 1 atm nitrogen. Chemical, X-ray diffraction, solid state nuclear magnetic resonance spectra and morphological information on this powder is presented. The X-ray diffraction data and previously published information have been used to develop a more complete specification of the unit cell dimensions.29Si magic-angle spinning nuclear magnetic resonance spectra of LaSi3N5 show two chemical shifts at –64.5 and –56.5 p.p.m. These shifts reflect two electronically different types of silicon which have been attributed to the effects of quadrupolar139La nuclei and their spatial arrangements around silicon atoms. 相似文献
166.
Labuda R Parich A Berthiller F Tancinová D 《International journal of food microbiology》2005,105(1):19-25
A total of 50 samples of poultry feed mixtures of Slovakian origin were analyzed for eight toxicologically significant Fusarium mycotoxins, namely zearalenone (ZON), A-trichothecenes: diacetoxyscirpenol (DAS), T-2 toxin (T-2) and HT-2 toxin (HT-2) and B-trichothecenes: deoxynivalenol (DON), 3-acetyl-deoxynivalenol (3-ADON), 15-acetyl-deoxynivalenol (15-ADON) and nivalenol (NIV). The A-trichothecenes and the B-trichothecenes were detected by means of high pressure liquid chromatography with tandem mass spectrometry detection (HPLC-MS/MS) and gas chromatography electron capture detection (GC-ECD), respectively. Reversed phase-high performance liquid chromatography with a fluorescence detector (RP-HPLC-FLD) was used for ZON detection. The most frequent mycotoxin detected was T-2, which was found in 45 samples (90%) in relatively low concentrations ranging from 1 to 130 microg kg(-1) (average 13 microg kg(-1)), followed by ZON that was found in 44 samples (88%) in concentrations ranging from 3 to 86 microg kg(-1) (average 21 microg kg(-1)). HT-2 and DON were detected in 38 (76%) and 28 (56%) samples, respectively, in concentrations of 2 to 173 (average 18 microg kg(-1)) for HT-2 and 64 to 1230 microg kg(-1) sample (average 303 microg kg(-1)) for DON. The acetyl-derivatives of DON were in just four samples, while NIV was not detected in any of the samples investigated. In as many as 22 samples (44%), a combination of four simultaneously co-occurring mycotoxins, i.e. T-2, HT-2, ZON and DON, was revealed. Despite the limited number of samples investigated during this study poultry feed mixtures may represent a risk from a toxicological point of view and should be regarded as a potential source of the Fusarium mycotoxins in Central Europe. This is the first reported study dealing with zearalenone and trichothecene contamination of poultry mixed feeds from Slovakia. 相似文献
167.
Translating the impact of knowledge management into knowledge‐based innovation: The neglected and mediating role of knowledge‐worker satisfaction 下载免费PDF全文
Muhammad Shujahat Bakhtiar Ali Faisal Nawaz Susanne Durst Aino Kianto 《人机工程学与制造业中的人性因素》2018,28(4):200-212
The purpose of knowledge management is innovation. However, this study proposes that the existence of knowledge management in the knowledge‐worker's work environment can nurture the overall satisfaction of knowledge worker. As the ultimate purpose of knowledge management is innovation performance, therefore, the satisfaction of knowledge worker as an outcome of knowledge management should be greater innovation performance. Consequently, the purpose of this study is to test the mediating role of satisfaction of knowledge worker between knowledge management and innovation. The study collected the data from 306 knowledge workers (engineers and managers) of software houses from Pakistan. The SmartPLS 3 Version 2.7 software that uses the PLS‐SEM (Partial Least Square‐Structural Equation Modelling) technique was used. The results indicate that satisfaction of knowledge worker mediates between two knowledge management processes (knowledge creation and knowledge sharing) and innovation significantly. However, it does not mediate between knowledge utilization and innovation significantly. 相似文献
168.
169.
Hans Michael Egon Pabst Franz Ledl und Hans-Dieter Belitz 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1985,181(5):386-390
Summary In addition to the mono- and dipyrrolidinohexosereductones described recently (Z Lebensm Unters Forsch (1984) 178:356) two further bittertasting compounds were isolated from heated mixtures of proline and sucrose (molar ratio 3: 1, 190 °C, 30 min) and also synthesized, namely 2,3-bis-(1-pyrrolidinyl)2-cyclopenten-l-one and 2,3-bis(1-pyrrolidinyl)-5methyliden-2-cyclopenten-l-one. The recognition thresholds (mmol/1) are 0.15–0.25 and 0.06–0.12 respectively. Both compounds have a burning bitter taste character. From a maltose-proline reaction mixture 2--glucosyl-5-hydroxy-5-methyl-4-piperidinyl-2-cyclopenten-1-one was isolated. When the dihydroxypyranone VI was heated with proline, 2,5-dihydroxy-5-methyl-4-prohnyl-2-cyclopenten-1-one and the cyclopent(b)azepinones XI and XII were among the compounds formed. These compounds also have a bitter taste character.Zusammenfassung Zusätzlich zu den kürzlich beschriebenen Mono- and Dipyrrolidinohexosereduktionen (Z Lebensm Unters Forsch (1984) 178:356) wurden zwei weitere bittere Verbindungen aus erhitzten Mischungen von Prolin and Saccharose (Molverhältnis 3:1, 190 °C, 30 min) isoliert and synthetisiert. Es handelt sich um 2,3-Bis-(1-Pyrrolidinyl)-2-cyclopenten-1-on und 2,3-Bis-(1-Pyrrolidinyl)-5-methyliden-2-cyclopenten-1-on. Die Erkennungsschwellenwerte (mmol/1) sind 0,15-0,25 and 0,06-0,12. Beide Verbindungen haben einen brennend-bitteren Geschmack. Aus einem Maltose-Prolin-Umsetzungsgemisch gelang die Isolierung des 2--Glucosyl-5-hydroxy-5-methyl-4-piperidinyl-2-cyclopenten-1-ons. Bei der Reaktion des Dihydropyranons VI mit Prolin wurden u. a. das 2,5-Dihydroxy-5-methyl-4-prolinyl2-cyclopenten-1-on sowie die Cyclopent(b)azepinone XI and XII gebildet. Diese Verbindungen sind ebenfalls mehr oder weniger stark bitter. 相似文献
170.
Comprehensive proteomic analyses require new methodologies to accelerate the correlation of gene sequence with protein function. Key tools for such efforts include biophysical probes that integrate into the covalent architecture of proteins. Lanthanide-binding tags (LBTs) are expressible, multitasking fusion partners that are optimized to bind lanthanide ions and have several desirable attributes, which include long-lived luminescence, excellent X-ray scattering power for phase determination, and magnetic properties to facilitate NMR spectroscopic structure elucidation. Herein, we present peptide sequences with a 40-fold higher affinity for Tb(3+) ions and significantly brighter luminescence intensity compared with existing peptides. Incorporation of an LBT onto ubiquitin as a prototype fusion protein allows the use of powerful protein-visualization techniques, which include rapid luminescence detection of LBT-tagged proteins in SDS-PAGE gels, as well as determination of protein concentrations in complex mixtures. The LBT strategy is a new alternative for expressing fluorescent fusion proteins by routine molecular biological techniques. 相似文献