全文获取类型
收费全文 | 6104篇 |
免费 | 252篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 87篇 |
综合类 | 30篇 |
化学工业 | 1705篇 |
金属工艺 | 166篇 |
机械仪表 | 111篇 |
建筑科学 | 351篇 |
矿业工程 | 24篇 |
能源动力 | 137篇 |
轻工业 | 494篇 |
水利工程 | 36篇 |
石油天然气 | 4篇 |
无线电 | 390篇 |
一般工业技术 | 1229篇 |
冶金工业 | 744篇 |
原子能技术 | 54篇 |
自动化技术 | 807篇 |
出版年
2023年 | 42篇 |
2022年 | 52篇 |
2021年 | 95篇 |
2020年 | 84篇 |
2019年 | 81篇 |
2018年 | 98篇 |
2017年 | 112篇 |
2016年 | 170篇 |
2015年 | 110篇 |
2014年 | 182篇 |
2013年 | 290篇 |
2012年 | 256篇 |
2011年 | 368篇 |
2010年 | 276篇 |
2009年 | 284篇 |
2008年 | 294篇 |
2007年 | 263篇 |
2006年 | 256篇 |
2005年 | 216篇 |
2004年 | 204篇 |
2003年 | 154篇 |
2002年 | 131篇 |
2001年 | 104篇 |
2000年 | 110篇 |
1999年 | 127篇 |
1998年 | 202篇 |
1997年 | 128篇 |
1996年 | 119篇 |
1995年 | 106篇 |
1994年 | 100篇 |
1993年 | 95篇 |
1992年 | 83篇 |
1991年 | 64篇 |
1990年 | 73篇 |
1989年 | 66篇 |
1988年 | 69篇 |
1987年 | 68篇 |
1986年 | 56篇 |
1985年 | 60篇 |
1984年 | 60篇 |
1983年 | 46篇 |
1982年 | 55篇 |
1981年 | 53篇 |
1980年 | 36篇 |
1979年 | 40篇 |
1978年 | 40篇 |
1977年 | 38篇 |
1976年 | 47篇 |
1975年 | 39篇 |
1973年 | 37篇 |
排序方式: 共有6369条查询结果,搜索用时 31 毫秒
61.
Wolfgang Schmid und Werner Grosch 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1986,182(5):407-412
Zusammenfassung Die Aromastoffe wurden aus Kirschsaft isoliert durch simultane Destillation/Extraktion (Extrakt I) und durch Destillation in Vakuum mit anschließender Extraktion des Destillates (Extrakt II). Die beiden Extrakte wurden entsäuert, fraktioniert und durch HRGC analysiert. Die chemischen Strukturen wurden nur von den Aromastoffen analysiert, die im Sniffing-port nach der HRGC-Trennung zu erkennen waren. Identifiziert wurden 28 Aromastoffe im Extrakt I und 18 im Extrakt II; 16 davon enthielt auch Extrakt I. Beim Abriechen der schrittweise verdünnten Extrakte im Sniffing-port wurden in beiden Extrakten dieselben sieben Verbindungen mit den höchsten Aromawerten gefunden: Benzaldehyd, Linalool, Hexanal, 2(E)-Hexanal, Phenylacetaldehyd, 2(E),6(Z)-Nonadienal und Eugenol. Extrakt I enthielt zusätzlich einen fruchtigen Aromastoff unbekannter Struktur mit hohem Aromawert.
Identification of highly aromatic volatile flavour compounds from cherries (Prunus cerasus L.)
Summary The flavour compounds were isolated from cherry juice by simultaneous distillation/extraction (extract I) and also by vacuum distillation followed by extraction of the condensate (extract II). Both extracts were freed from the acids, fractionated and then analyzed by HRGC. The chemical structures of only the flavour compounds detectable at the sniffing-port of the HRGC-effluent were determined. 28 Flavour compounds were identified in extract I; 18 in extract II of which 16 occurred also in extract I. Sniffing the stepwise diluted extracts I and II revealed the same seven compounds with the highest aroma values: benzaldehyde, linalool, hexanal, 2(E)-hexanal, phenylacetaldehyde, 2(E),6(Z)-nonadienal and eugenol. Extract I contained in addition a flavour compound of high aroma value, whose structure is unknown.相似文献
62.
Wolfgang Schmid und Werner Grosch 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1986,183(1):39-44
Zusammenfassung Sieben Aromastoffe, isoliert durch Destillation im Vakuum aus Sauer- und Süßkirschprodukten, wurden vergleichend analysiert. In den frisch gepreßten Säften aus je fünf Sorten Sauer- und Süßkirschen wurden große Konzentrationsunterschiede (gm/l) gefunden: Benzaldehyd (18–393), Linalool (0,5–1,7), Hexanal (0,3–54,7), 2(E)-Hexenal (2,4220), 2(E),6(Z)-Nonadienal (0,1–2,4), Phenylacetaldehyd (2,1–5,6) und Eugenol (1,0–22,2). Die Benzaldehydkonzentration zeigte die höchste Korrelation zur Erkennungsschwelle für den Kirschgeruch der Säfte. Bei der Herstellung von Konfitüren veränderte sich die Zusammensetzung der Aromastoffe: Benzaldehyd und Linalool nahmen um den Faktor 7 bzw. 13 zu; Hexanal, 2(E)-Hexenal sowie Phenylacetaldehyd nahmen stark ab. Der Anstieg von Benzaldehyd und Linalool, der auch bei der simultanen Destillation/Extraktion der Säfte auftrat, beruht auf einer Hydrolyse entsprechender Glykoside, die durch eine Hitzebehandlung stark beschleunigt wird.
Quantitative analysis of the volatile flavour compounds having high aroma values from sour (Prunus cerasus L.) and sweet (Prunus apium L.) cherry juices and jams
Summary The analysis results for seven of the aroma compounds obtained by vacuum distillation from sweet and sour cherry products were compared. The freshly pressed juices from 5 varieties of sour and 5 varieties of sweet cherries showed great differences in concentrations (g/1): benzaldehyde (18–393), linalool (0.5–1.7), hexanal (0.3–54.7), 2(E)-hexenal (2.4–220), 2(E),6(Z)-nonadienal (0.1–2.4), phenylacetaldehyde (2.1–5.6) and eugenol (1.0–22.2). The benzaldehyde content of the juices showed the highest correlation to the recognition threshold of the cherry aroma note. The cherry jam showed a drastic change in the aroma composition: benzaldehyde and linalool increased greatly (7 and 13-times, respectively), while hexanal, 2(E)-hexenal and phenylacetaldehyde strongly decreased. The increase in benzaldehyde and linalool, which was also observed during simultaneous distillation/extraction of the juices, is caused by the hydrolysis of the corresponding glycosides during the heat treatments.相似文献
63.
Oliver Schmutzler Sebastian Graf Nils Behm Wael Y. Mansour Florian Blumendorf Theresa Staufer Christian Krnig Dina Salah Yanan Kang Jan N. Peters Yang Liu Neus Feliu Wolfgang J. Parak Anja Burkhardt Elisabetta Gargioni Sabrina Gennis Sharah Chandralingam Finn Heg Wolfgang Maison Kai Rothkamm Florian Schulz Florian Grüner 《International journal of molecular sciences》2021,22(7)
Quantitative cellular in vitro nanoparticle uptake measurements are possible with a large number of different techniques, however, all have their respective restrictions. Here, we demonstrate the application of synchrotron-based X-ray fluorescence imaging (XFI) on prostate tumor cells, which have internalized differently functionalized gold nanoparticles. Total nanoparticle uptake on the order of a few hundred picograms could be conveniently observed with microsamples consisting of only a few hundreds of cells. A comparison with mass spectroscopy quantification is provided, experimental results are both supported and sensitivity limits of this XFI approach extrapolated by Monte-Carlo simulations, yielding a minimum detectable nanoparticle mass of just 5 pg. This study demonstrates the high sensitivity level of XFI, allowing non-destructive uptake measurements with very small microsamples within just seconds of irradiation time. 相似文献
64.
65.
Luis Fernando Crdoba Wolfgang M.H. Sachtler Consuelo Montes de Correa 《Applied catalysis. B, Environmental》2005,56(4):269-277
A series of sulfated zirconia supported Pd/Co catalysts was synthesized by the sol–gel method and examined for NOx reduction by methane. The NO conversion increased up to a Co/S ratio of 0.43, and then decreased at a higher Co loading (Co/S = 0.95). Sulfate content was also essential for obtaining high selectivity to molecular nitrogen. A catalyst loaded with 0.06 wt.% Pd, 2.1 wt.% Co and 2.1 wt.% S (Pd/Co-SZ-2) exhibited remarkable performance under lean conditions and displayed stability in a long-term durability test using a synthetic reaction mixture containing 10% water vapor. This catalyst exhibited the highest sulfur retention most probably as cobalt sulfide. Besides, the catalytic oxidation of NO to NOy groups was confirmed by FT-IR, in agreement with the general mechanism for the SCR of NO by hydrocarbons. In the absence of oxygen in the feed stream, the catalyst was highly active for NO reduction with methane. IR stretching bands assigned to N2O and adsorbed nitro groups were identified upon adsorbing NO on Pd/Co-SZ-2. This indicates that under rich conditions disproportionation of NO to N2O and NO2 occurs and confirms that the formation of NO2 species is an essential step for NO reduction by CH4. 相似文献
66.
The effect of specific β‐nucleation on morphology and mechanical behavior of isotactic polypropylene
The commercial grade of isotactic polypropylene was modified by a specific β‐nucleating agent in a broad concentration range. The supermolecular structure of the specimens prepared by injection molding was characterized by X‐ray scattering and correlated with mechanical behavior. It was found that at a critical nucleant concentration of 0.03 wt % the content of the β‐modification virtually reaches a saturation level. With further addition of the nucleant, the β‐phase content increases only slightly. The long period passes through a distinct maximum at the same nucleant concentration. This singularity in structure remarkably correlates with a minimum of the yield stress and maxima of strain at break and fracture toughness. Such general behavior is also reflected in the correlation between the β‐phase concentration and fracture toughness profiles along the injection‐molded bars. It is suggested that in the critically nucleated material an optimum thickness of the amorphous interlayer with connecting chains between the β‐crystallites is established, rendering the material the highest possible ductility and toughness. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1174–1184, 2002 相似文献
67.
Starlike macromers were prepared from hydroxypropyl organosolv lignin by reaction with propylene oxide, and they were analyzed by a combination of conventional analysis techniques. The average number of arms per macromer was controlled by partial capping with an alkoxy group; and the average length of arms by the degree of chain extension with propylene oxide. Analysis methods included treatment with hydriodic acid followed by gas chromatographic separation of alkyl iodides (HI/GC), UV spectroscopy, H-NMR spectroscopy, and thermal analysis. The results were consistent with a hypothetical pentameric model structure having between two and six radiating arms, each with a length of between 1 and 4 propylene oxide units. The UV method was best qualified to determine degree of chain extension, while HI/GC was best suited for analyzing average number of arms per macromer fragment. The synthesis and analysis of starlike macromers from lignin is viewed as an important stepping stone for the formulation of lignin-based engineering plastics and multiphase materials. 相似文献
68.
A series of polyurethane (PU) films was prepared from chain-extended hydroxypropyl lignins (CEHPL). In appearance, these films ranged from brittle and dark brown to rubbery and bronze. The thermal, mechanical, and network properties of these PUs were investigated by DMTA and DSC analysis. All films exhibited single Tg's which varied between ?53° and 101°C, depending on lignin content. From swelling experiments, molecular weight between crosslinks (M c) was determined and found to vary over 2.5 orders of magnitude. The M c's were related to the change in Tg that accompanied network formation. Stress–strain experiments showed a variation in Young's modulus between 7 and 1300 MPa. Most of the variation in material properties was related to lignin content and to a lesser extent to diisocyanate type, hexamethylene diisocyanate, or toluene diisocyanate. The source of the CEHPL had no effect on the observed properties. From these results it was concluded that the properties of PUs can be controlled and engineered for a wide variety of practical uses. 相似文献
69.
70.
The use of hypochlorite, formed in situ by anodic oxidation of sodium chloride solution, for bleaching indigo-dyed denim has been studied at room temperature and at 50 °C. A direct relationship between the charge flow applied and the bleaching effect was observed. This enables consistent oxidative bleaching to be achieved by controlling the electrochemical process. The use of mixed anolytes containing small concentrations of bromide ions enhanced the bleaching effect considerably, even after lowering the temperature to room temperature. The molar concentration of bromide ions required was much lower than that of chloride in the anolyte. 相似文献