全文获取类型
收费全文 | 641篇 |
免费 | 18篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 28篇 |
综合类 | 1篇 |
化学工业 | 129篇 |
金属工艺 | 10篇 |
机械仪表 | 3篇 |
建筑科学 | 30篇 |
能源动力 | 32篇 |
轻工业 | 29篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 78篇 |
一般工业技术 | 128篇 |
冶金工业 | 136篇 |
原子能技术 | 8篇 |
自动化技术 | 53篇 |
出版年
2022年 | 9篇 |
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 5篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 28篇 |
2012年 | 17篇 |
2011年 | 30篇 |
2010年 | 14篇 |
2009年 | 30篇 |
2008年 | 36篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 12篇 |
2004年 | 19篇 |
2003年 | 16篇 |
2002年 | 18篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 20篇 |
1998年 | 43篇 |
1997年 | 34篇 |
1996年 | 22篇 |
1995年 | 15篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有670条查询结果,搜索用时 15 毫秒
1.
K Sudo Y Matsumoto M Matsushima M Fujiwara K Konno K Shimotohno S Shigeta T Yokota 《Canadian Metallurgical Quarterly》1997,238(2):643-647
This study evaluated the inhibitory effects of thiazolidine derivatives on hepatitis C virus (HCV) protease and other human serine proteases. The inhibition efficacy was tested with a reversed-phase high-performance liquid chromatography (HPLC) assay system using a NS3-NS4A fusion protein as the HCV protease and a synthetic peptide substrate that mimics the NS5A-5B junction. Nine thiazolidine derivatives showed more than 50% inhibition at 50 microg/ml. The most potent derivative was RD4-6250, with 50% inhibition at a concentration of 2.3 microg/ml; this concentration was lower than those of other protease inhibitors reported previously. The most selective derivative was RD4-6205, with 50% inhibition at a concentration of 6.4 microg/ml, a lower concentration than those on other serine proteases (chymotrypsin, trypsin, plasmin, and elastase). These results suggest that the RD4-6205 skeleton is an important structure for inhibitory activity on the HCV protease NS3-NS4A. 相似文献
2.
Optical and electronic properties of cobalt-doped zinc oxide films prepared by the sputtering method
In-doped ZnO, Co-doped ZnO and Li-doped NiO are successively deposited on quartz by the sputtering method. A current versus voltage curve of the three-layer device, in which the Indoped ZnO and Li-doped NiO are used as electrodes, reveals that the In-doped ZnO is an ohmic electrode and the Li-doped NiO is a blocking electrode with respect to electron injection. In photocurrent spectra of the three-layer device, there are two distinct peaks around 410 and 640 nm. The former is ascribed to the photoionization caused by the electric-dipole transition from the ground states,4A2(F), to the conduction band, and the latter to the thermal emission from electronic excited states of Co2+,4T1(P). 相似文献
3.
Takashi Ishikawa Sunao Sugimoto Masamichi Matsushima Yoichi Hayashi 《Composites Science and Technology》1995,55(4):349-363
Compression-after-impact (CAI) tests have been conducted for quasi-isotropic thick plates with 48 plies by using the NASA method and on plates with 32 plies by using the SACMA method. Specimens are made of CF/PEEK (APC-2) and conventional CF/epoxy for the NASA plates and CF/epoxy for the SACMA plates. In the NASA CAI tests, the sequence of delamination buckling and its propagation is clearly revealed through various experimental techniques. One major technique is moiré topography, and the other is thermo-mechanical stress analysis with a high-accuracy infrared sensor. The arrest of delamination propagation just before catastrophic failure due to high fracture toughness is clearly captured by the moiré camera. This behavior provides good CAI values of CF/PEEK. The initial buckling properties of the delaminated region by the impact are then extensively discussed. Numerical predictions of initial buckling stress have been obtained by modelled geometry of the delaminated region simplified from its precise structure clarified by ultrasonic C-scanning. They agree fairly well with the experimental results. The in-plane stress distribution in the delaminated region before initial buckling is measured by an infrared stress graphic system. This compared favorably with finite element predictions. Two types of symmetric buckling modes with respect to the central plate surface, twin and single peak ones, are experimentally captured. 相似文献
4.
Starting from an effective action for the order parameter field, we derive a coupled set of generalized hydrodynamic equations
for a Bose condensate in an optical lattice at finite temperatures. Using the linearized hydrodynamic equations, we study
the microscopic mechanism of the Landau instability due to the collisional damping process between the condensate and noncondensate
atoms. It is shown that the Landau criterion for the stability of a superfluid in a uniform system is modified due to the
presence of the periodic optical lattice potential. 相似文献
5.
P Morell CV Barrett JL Mason AD Toews JD Hostettler GW Knapp GK Matsushima 《Canadian Metallurgical Quarterly》1998,12(4-5):220-227
When C57BL/6J mice, 8 weeks of age, received 0.2% Cuprizone in their diet, extensive demyelination in corpus callosum was detectable after 3 weeks, and there was massive demyelination by 4 weeks. As expected, the accumulation of phagocytically active microglia/macrophages correlated closely with demyelination. When Cuprizone was removed from the diet, remyelination was soon initiated; after 6 weeks of recovery, myelin levels were near-normal and phagocytic cells were no longer prominent. Steady-state levels of mRNA for myelin-associated glycoprotein, myelin basic protein, and ceramide galactosyltransferase were already profoundly depressed after 1 week of Cuprizone exposure and were only 10-20% of control values after 2 weeks. Unexpectedly, upregulation of mRNA for these myelin genes did not correlate with initiation of remyelination but rather with accumulation of microglia/macrophages. After 6 weeks of exposure to Cuprizone, mRNA levels were at control levels or higher-in the face of massive demyelination. This suggests that in addition to effecting myelin removal, microglia/macrophages may simultaneously push surviving oligodendroglia or their progenitors toward myelination. 相似文献
6.
Masato Sakaguchi Tetsuro Yokono Yuzo Sanada Junkichi Shoma Hisatsugu Kashiwabara 《Fuel》1981,60(2):136-138
The ball-milling of coal with methylmethacrylate monomer was carried out under vacuum at 77 K and at room temperature and in air. The e.s.r. and i.r. spectra of ball-milled material showed that a copolymer of coal and methylmethacrylate was formed on the surfaces of coal created by ball-mining. Oxygen is an inhibitor to this process. 相似文献
7.
This study examines further the phenomena of the modification of coal carbonizations by organic additives. Anthracene, pyrene and chrysene modify the carbonization in a closed system of coking coals as observed from increases in the size of optical textures of resultant cokes. Weakly caking coals are unaffected. Chrysene is the most efficient modifier probably because of its lowest calculated free valence. The co-additives tetralin and hydrogenated anthracene oil further enhance the modification processes so obviating the necessity to use hydrogenated additives. Co-carbonizations of oxidized coking and caking coals with decacyclene are effective in removing the effects of mild oxidation. Increased rates of carbonization enhance the sizes of optical textures of resultant cokes. 相似文献
8.
Hisao Ichijo Tetsuro Suehiro Aizo Yamauchi Shigeo Ogawa Masanori Sakurai Nobuo Fujii 《应用聚合物科学杂志》1982,27(5):1665-1674
A poly(vinyl alcohol) (PVA) fiber support incorporating various aminoacetal functional groups has been developed for immobilizing enzymes. The aminated PVA fiber seems to adsorb enzymes with electrostatic force of attraction; thus the immobilization procedure is simple. By the use of this fiber having immobilized enzymes, the reaction between enzymes and substrates is nearly independent of the size of subtstrates. This newly developed type of fiber, which is formed by a mass superfine fibers (SFF), each measuring 1 μm or less in diameter, permits much more increased surface area than the conventional enzyme immobilization supports. Our studies of the properties of the fiber for immobilization of enzymes show the following results: (1) SFF has a greater ability for the immobilization of invertase than ordinary fibers; (2) dimethyl-aminated SFF has the best performance for the immobilization of invertase. From these results, it is concluded that the dimethyl-aminated SFF is an excellent support for the immobilization of invertase. 相似文献
9.
High temperature, high pressure e.s.r. measurements of the hydrogenation reaction of Taiheiyo coal in the presence of catalysts were carried out to understand the stabilization of thermally and/or catalytically induced free radicals. A decrease in free radical concentration with increasing temperature was observed for ZnCl2 and SnCl2 · 2H2O catalysts at 10MPa under hydrogen gas. High pressure modified single-cell d.t.a. and p.d.a. equipment augmented the uniquely designed high temperature, high pressure e.s.r. cell. The hydrogenation reaction was monitored under the same experimental conditions as for e.s.r. From the results of the combination of high temperature, high pressure e.s.r. with high pressure d.t.a. and p.d.a., it was established that H2 molecules can react efficiently with free radicals from coal molecules created by the presence of ZnCl2 and SnCl2 · 2H2O catalysts. 相似文献
10.
Preparation of zinc ferrite in the presence of carbon material and its application to hot-gas cleaning 总被引:3,自引:0,他引:3
In order to develop an efficient absorbent of H2S in coal gasification, zinc ferrite (ZnFe2O4) was prepared in the presence of carbon materials such as activated carbon (AC), activated carbon fiber (ACF), and Yallourn coal (YL). The absorption behavior of absorbents for H2S was examined using a fixed-bed flow type reactor equipped with a quadrupole mass spectrometer.Carbon material-supported ZnFe2O4 exhibited larger desulfurization capacity for H2S than unsupported ferrites. They could efficiently remove H2S from 4000 ppm levels in a simulated coal gasification gas to less than 1 ppm at 500 °C. The absorption capacity of H2S with ZnFe2O4/AC, ZnFe2O4/ACF, and ZnFe2O4/YL exhibited nearly 100% of stoichiometric amount of loaded metal species. They could be regenerated by an air oxidation in O2-Ar (50 vol%) at 450 °C for 30 min. The regenerated ferrite can be used for repeated absorption of H2S with a very slight decrease in the absorption capacity. 相似文献