全文获取类型
收费全文 | 4378篇 |
免费 | 136篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 67篇 |
综合类 | 29篇 |
化学工业 | 1335篇 |
金属工艺 | 105篇 |
机械仪表 | 84篇 |
建筑科学 | 265篇 |
矿业工程 | 8篇 |
能源动力 | 73篇 |
轻工业 | 348篇 |
水利工程 | 25篇 |
石油天然气 | 1篇 |
无线电 | 256篇 |
一般工业技术 | 806篇 |
冶金工业 | 584篇 |
原子能技术 | 38篇 |
自动化技术 | 500篇 |
出版年
2022年 | 48篇 |
2021年 | 56篇 |
2020年 | 46篇 |
2019年 | 57篇 |
2018年 | 65篇 |
2017年 | 55篇 |
2016年 | 94篇 |
2015年 | 82篇 |
2014年 | 112篇 |
2013年 | 205篇 |
2012年 | 170篇 |
2011年 | 254篇 |
2010年 | 185篇 |
2009年 | 164篇 |
2008年 | 194篇 |
2007年 | 185篇 |
2006年 | 132篇 |
2005年 | 157篇 |
2004年 | 132篇 |
2003年 | 103篇 |
2002年 | 85篇 |
2001年 | 83篇 |
2000年 | 85篇 |
1999年 | 88篇 |
1998年 | 106篇 |
1997年 | 87篇 |
1996年 | 72篇 |
1995年 | 76篇 |
1994年 | 70篇 |
1993年 | 74篇 |
1992年 | 70篇 |
1991年 | 49篇 |
1990年 | 74篇 |
1989年 | 46篇 |
1988年 | 45篇 |
1987年 | 53篇 |
1986年 | 42篇 |
1985年 | 60篇 |
1984年 | 54篇 |
1983年 | 47篇 |
1982年 | 51篇 |
1981年 | 43篇 |
1979年 | 43篇 |
1978年 | 44篇 |
1977年 | 65篇 |
1976年 | 43篇 |
1975年 | 42篇 |
1974年 | 56篇 |
1972年 | 41篇 |
1970年 | 40篇 |
排序方式: 共有4524条查询结果,搜索用时 0 毫秒
991.
Martin Hundt Norman Engel Michael G. Schnitzlein Prof. Dr.‐Ing. Klaus Schnitzlein 《化学,工程师,技术》2013,85(5):758-763
The utilization of lignocellulose as renewable feedstock for the chemical industry necessitates the development of sustainable pulping processes. A new process is introduced enabling the effective fractionation not only of annual fiber plants or hardwood but also of more resistant softwoods. The resulting ultrapure pulp is free of inhibiting degradation products and can be almost completely enzymatically hydrolyzed. 相似文献
992.
993.
Summary Poly(1,3-dihydroxy-2-(4-ethynylphenyl)-4,4,5,5-tetramethylimidazolidine), poly(2-(4-ethynylphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-oxide), poly(4-(4-ethynylbenzylideneamino)-2,2,6,6-tetramethylpiperidine) and poly(4-(4-ethynylbenzylideneamino)-2,2,6,6-tetramethylpiperidine-1-oxyl) were prepared from poly(4-ethynyl-benzaldehyde). The products were characterized spectroscopically (IR, UV, 1H and 13C NMR) and with respect to the magnetic susceptibility. The polyradicals (1-oxyl compounds) showed paramagnetic properties obeying Curie's law. 相似文献
994.
Thomas Vorderwülbecke Matthias Epple Heiko Karl Cammenga Sabine Petersen Klaus Kieslich 《Journal of the American Oil Chemists' Society》1992,69(8):797-801
A new method was developed to obtain lactones from butterfat. The application of lipases and capillary gas-liquid chromatography
with chiral phases for the separation of γ-lactone enantiomers resulted in elucidation of the racemic composition of γ-lactones
from butterfat. The seasonal distribution of lactones in butterfat was determined. 相似文献
995.
Amit Das Klaus Werner Stöckelhuber René Jurk Dieter Jehnichen Gert Heinrich 《Applied Clay Science》2011,51(1-2):117-125
The effect of stearic acid on the properties of different rubbers/montmorillonite composites was studied. We used alkyl quaternary ammonium modified montmorillonite (organo-montmorillonite), which was additionally modified with stearic acid. Premixed with the montmorillonite, the stearic acid expanded the clay mineral layers, thus permitting the rubber molecules to be more easily intercalated into the montmorillonite. We used several kinds of rubbers with different polarities and molecular structures. Both the X-ray diffraction and infrared spectroscopy studies indicated that the stearic acid propped up interlayer space allowing the intercalation of the rubber chains. Measurement of the physical and dynamic mechanical properties, along with studies of the composite morphology by transmission electron microscopy, very clearly showed that mixing the montmorillonite clay with stearic acid yielded various rubber nanocomposites with a high amount of intercalated and exfoliated montmorillonite particles. Either complete intercalation or increased nanostructure formation yielded as compared to the standard rubber–clay mineral composites prepared with a normal dose (2 parts per hundred of rubber) of stearic acid, can be achieved by adding a large amount of stearic acid (10 parts per hundred of rubber in our case) to non-polar rubbers (e.g. natural rubber (NR), ethylene propylene rubber (EPDM), etc.) that are not known to form totally exfoliated structures by simple melt mixing of montmorillonite and rubber. 相似文献
996.
997.
998.
Arunjunai Raj Mahendran Nicolai Aust Klaus Lederer 《Polymer-Plastics Technology and Engineering》2013,52(11):1142-1146
The partial degradation of high-density polyethylene was done in an internal mixer for different residence time. The oxidative thermomechanical degradation resulted in the formation of carbonyl groups in the polymer. The carbonyl index values estimated from the FTIR studies indicate the increase of carbonyl groups without any induction time. The common phenomenon during oxidative degradation of polyethylene is the increase in trans-vinylene groups and decrease in vinyl groups and these phenomena are observed in the current investigation. Owing to the chain scission occurring during the mixing at processing temperature, the change in morphology was studied by the amount of crystallinity estimated through DSC. The variation in the molar mass of the material was followed by SEC method. 相似文献
999.
Tengfei Chen Boris Reznik Dagmar Gerthsen Weigang Zhang Klaus Hüttinger 《Carbon》2005,43(15):3088-3098
The microstructure of carbon/carbon composites obtained by isothermal, isobaric chemical vapor infiltration (CVI) of carbon fiber preforms consisting of aligned fiber bundles separated by fiber fleeces was studied comparatively by polarized light microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED). Deposition rate as well as matrix microstructure do not differ in the aligned fiber bundles and fiber fleeces exhibiting different local surface area/volume ratios. The matrices which are homogeneously textured according to PLM exhibit pronounced spatial texture gradients at the sub-μm-scale if investigated by SAED. The texture gradients appear to be independent on the infiltration time, distance between fibers but evidently depend on the total methane pressure. TEM and SEM observations show a thin high-textured layer between the fiber and the medium-textured transitional layer below the high-textured matrix layer containing columnar grains. This thin layer replicates the surface unevenness of the fiber surface while it is absent at the initial carbon fiber surface before infiltration. 相似文献