全文获取类型
收费全文 | 63501篇 |
免费 | 6591篇 |
国内免费 | 3647篇 |
专业分类
电工技术 | 2541篇 |
综合类 | 4921篇 |
化学工业 | 15331篇 |
金属工艺 | 3166篇 |
机械仪表 | 4561篇 |
建筑科学 | 6003篇 |
矿业工程 | 5426篇 |
能源动力 | 3297篇 |
轻工业 | 4587篇 |
水利工程 | 2212篇 |
石油天然气 | 8190篇 |
武器工业 | 579篇 |
无线电 | 1560篇 |
一般工业技术 | 5616篇 |
冶金工业 | 2647篇 |
原子能技术 | 1129篇 |
自动化技术 | 1973篇 |
出版年
2024年 | 253篇 |
2023年 | 801篇 |
2022年 | 1694篇 |
2021年 | 2130篇 |
2020年 | 2275篇 |
2019年 | 1907篇 |
2018年 | 1840篇 |
2017年 | 2194篇 |
2016年 | 2402篇 |
2015年 | 2404篇 |
2014年 | 3947篇 |
2013年 | 4162篇 |
2012年 | 5256篇 |
2011年 | 5046篇 |
2010年 | 3592篇 |
2009年 | 3524篇 |
2008年 | 2945篇 |
2007年 | 3886篇 |
2006年 | 3784篇 |
2005年 | 3050篇 |
2004年 | 2757篇 |
2003年 | 2255篇 |
2002年 | 1947篇 |
2001年 | 1665篇 |
2000年 | 1465篇 |
1999年 | 1170篇 |
1998年 | 987篇 |
1997年 | 836篇 |
1996年 | 680篇 |
1995年 | 586篇 |
1994年 | 562篇 |
1993年 | 318篇 |
1992年 | 280篇 |
1991年 | 227篇 |
1990年 | 164篇 |
1989年 | 146篇 |
1988年 | 112篇 |
1987年 | 104篇 |
1986年 | 66篇 |
1985年 | 78篇 |
1984年 | 40篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 22篇 |
1980年 | 25篇 |
1979年 | 22篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1959年 | 17篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The synthesis of super-microporous aluminosilicate with a pore diameter of 14.6 Å has been achieved, by means of synthesis under specified conditions with a skeletal material comprising TMOS and a small quantity of sodium aluminate, and a conventional alkyl-trimethylammonium halide (C10TMABr) as a template. This super-microporous aluminosilicate has an adsorption capacity of 0.2 ml/g at a relative water vapor pressure of 0.2, and thus is promising as an adsorbent for an adsorption heat-pump. 相似文献
62.
63.
Douglas D. Frey 《Chemical Engineering Communications》1992,117(1):143-162
A local equilibrium theory for nonisothermal gas adsorption is developed which accounts for variations in interstitial gas velocity induced by adsorption. Also presented are expressions describing the entropy admissibility criterion. A solution is developed for a Riemann's problem involving adiabatic gas-phase adsorption where there is no inert diluent and where Langmuir isotherms apply. 相似文献
64.
A fast and simple 1H NMR spectroscopic method was developed for the concentration measurement of aromatic, olefinic and aliphatic fractions in gasoline samples. Simultaneously, individual components such as benzene, methyl tert-butyl ether and several dienes could be determined. The method relies on only a few, well-established assumptions about the molecular compositions and is therefore applicable to a broad range of gasolines. It is well suited for laboratories with high sample throughput since measurement time is short and all concentrations are determined within one NMR experiment. The method was applied to commercial gasolines and samples used in European round robin tests. Comparisons of NMR and round robin test results showed excellent agreement. 相似文献
65.
The recent formulation of the preferential adsorption coefficient, λ, which takes into account differences in molecular contact surface and in free volume, is tested by comparing theoretical with experimental values of λ from the literature. Seven different systems containing polystyrene and poly(methyl methacrylate) are considered. Agreement between theory and experiment is reached by treating the contact surface of the polymer as a fitting parameters, s. The adjusted values of s are: (a) systematically higher than the ones calculated from chain geometry; (b) largest in systems containing specific interactions (methanol). The connection between this enhanced apparent contact surface of the polymer and the ternary interaction parameter of the classical theory of λ, is analysed. 相似文献
66.
大压差减温减压是能的严重贬值。根据公司供热现状,分析了热电联产的可行性,利用蒸汽余压发电后,再供生产系统各热用户,这样既节约了能源又缓解了集团公司用电紧张的局面,而且有相当可观的经济效益。 相似文献
67.
This paper reports adsorption measurements that show molecular sieve effects in amorphous hydrogenated carbon (a-C : H) films deposited by d.c. magnetron discharge decomposition of acetylene. Adsorption of organic gases on the films is studied by using a quartz crystal microbalance technique. The sieve effect in this material depends on both deposition and annealing conditions. Films having significant molecular sieve effects are found to be typically microporous and to have a very small characteristic micropore dimension. It is suggested that the d.c. sputtered a-C : H film may be useful as a molecular sieve material in selective adsorption and gas permeation studies. 相似文献
68.
Viscosimetric measurements were obtained with the ternary systems polystyrene/dioxane/methanol, polystyrene/benzene/methanol and poly(methyl methacrylate)/dioxane/cyclohexane, changing the solvent mixture composition at constant temperature. The polystyrene and poly(methyl methacrylate) systems exhibit a transition phenomenon with solvent-mixture composition in which the polymer is just above the theta condition. In the case where two theta conditions occur ((θ-intra, θ-inter) the transition point is closely related to the intramolecular theta conditions. Moreover the intramolecular theta conditions vary with the molecular weight in the region of molecular weights where the preferential adsorption also varies. This variation induces a variation of the transition point with molecular weight which obeys a formula analogous to that giving the variation of the preferential adsorption with molecular weight. 相似文献
69.
针对吸附系统内除湿剂硅胶频繁破碎现象进行优化。在找出硅胶破碎原因的基础上,通过吸附塔直径放大18.3%,引出部分尾气,使床层流速降低。在吸附塔进口管处,安装雾沫分离器;在硅胶前沿填充部分耐水硅胶以减少液态水的冲击。再生蒸汽加热管上加调节阀防止硅胶过分干燥。使A塔硅胶使用了540d,B塔硅胶使用了630d。 相似文献
70.
In order to understand the change rules of stress-displacement in surrounding rocks of dynamic pressure roadways in deep mines and to obtain a theoretical basis for analyses of roadway stability and designs of support,we established a coupling equation of adjacent rock strength,mining stress and supporting resistance on the basis of an elastic-plastic theory of mechanics.We obtained an analytical solution for stress and displacement distribution of elastic and plastic regions in surrounding rock of dynamic pressure roadway..Based on this theory,we have analyzed the changes in stress-displacement in elastic and plastic regions of surrounding rocks of dynamic pressure roadways in the Haizi Coal Mine.The results show that:1) radial and tangential stress change violently within the first 4 m from the inner surface of a roadway after excavation;radial stress increases while tangential stress decreases within a range of about 6 m from the inner surface of the roadway as a function of q3;2) radial and tangential stress increase with an increase in the mining pressure coefficient k;the increase in the rate of tangential stress is greater than that of radial stress;3) the radial displacement of the inner surface of roadways decreases with an increase in q3,provided that k remains unchanged. 相似文献