全文获取类型
收费全文 | 3285篇 |
免费 | 138篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 34篇 |
综合类 | 4篇 |
化学工业 | 846篇 |
金属工艺 | 66篇 |
机械仪表 | 68篇 |
建筑科学 | 111篇 |
矿业工程 | 6篇 |
能源动力 | 116篇 |
轻工业 | 179篇 |
水利工程 | 17篇 |
石油天然气 | 7篇 |
无线电 | 333篇 |
一般工业技术 | 647篇 |
冶金工业 | 570篇 |
原子能技术 | 24篇 |
自动化技术 | 396篇 |
出版年
2023年 | 25篇 |
2022年 | 54篇 |
2021年 | 90篇 |
2020年 | 67篇 |
2019年 | 70篇 |
2018年 | 81篇 |
2017年 | 60篇 |
2016年 | 95篇 |
2015年 | 61篇 |
2014年 | 75篇 |
2013年 | 166篇 |
2012年 | 155篇 |
2011年 | 169篇 |
2010年 | 138篇 |
2009年 | 117篇 |
2008年 | 162篇 |
2007年 | 142篇 |
2006年 | 115篇 |
2005年 | 103篇 |
2004年 | 104篇 |
2003年 | 78篇 |
2002年 | 79篇 |
2001年 | 64篇 |
2000年 | 63篇 |
1999年 | 53篇 |
1998年 | 121篇 |
1997年 | 80篇 |
1996年 | 65篇 |
1995年 | 57篇 |
1994年 | 60篇 |
1993年 | 62篇 |
1992年 | 41篇 |
1991年 | 32篇 |
1990年 | 32篇 |
1989年 | 31篇 |
1988年 | 28篇 |
1987年 | 32篇 |
1986年 | 34篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 30篇 |
1982年 | 22篇 |
1981年 | 26篇 |
1980年 | 19篇 |
1978年 | 26篇 |
1977年 | 29篇 |
1976年 | 27篇 |
1975年 | 17篇 |
1974年 | 19篇 |
1973年 | 16篇 |
排序方式: 共有3424条查询结果,搜索用时 0 毫秒
1.
A micromechanics analysis is performed for the determination of the five independent elastic moduli of unidirectional fiber composites. By considering viscoelastic phases and by using the correspondence principle and the inversion of the Laplace transform, the five time-dependent functions which characterize the effective behavior of viscoelastic composites are established. The predicted time-dependent behavior is applied for the analysis of viscoelastic laminated plates. The resulting viscoelastic effects are shown, and comparison between the results obtained within the classical laminated plate theory and the first-order shear deformation theory is discussed. 相似文献
2.
Jacob Hooker David Hinks Gerardo Montero Christopher Conlee 《Coloration Technology》2002,118(6):273-276
The synthesis of azo dyes via a conventional aqueous-based diazotisation and coupling reaction requires the use of relatively high concentrations of mineral acids, which leads to high electrolyte concentrations in wastewater. Reported in this paper is an environmentally benign one-pot method for the synthesis of a nonionic azo dye, N,N -diethyl- N -{4-[( E )-(4-nitrophenyl)diazenyl]phenyl}amine, in supercritical carbon dioxide without using a mineral acid. The product yield increased significantly with temperature, with 91% theoretical yield afforded at 80 °C. The pressure of the system had little influence on product yield. 相似文献
3.
4.
5.
6.
The synthesis of hydrocarbons via hydrogenation of carbon monoxide was investigated over cobalt—nickel—zirconia catalysts of various compositions in combination with zeolite HZSM-5 in “mixed bed” and “follow bed” arrangements. These combinations resulted in the formation of aromatics in amounts as high as 30-35 wt% under relatively mild operating conditions (1 atm, 250–280°C). Although the olefinicity of C2 and C3 fractions in the product stream was higher in the mixed bed compared to the follow bed arrangement, the selectivities to aromatics were comparable in the two bed arrangements. The aromatic selectivity was found to be sensitive to operating conditions. The formation of aromatics was favored at high HZSM-5/metal catalyst ratios, low space velocities and high reaction temperatures. The product distributions obtained using various metal/zeolite bifunctional catalysts have been discussed. 相似文献
7.
Thermally fractionated components of an oil prepared by the liquefaction of aspen poplar wood have been upgraded using a HZSM-5 zeolite catalyst to yield products rich in benzene, toluene, xylenes and higher molecular weight aromatics. The effect of reactor temperatures on the relative abundance of these products has been studied. 相似文献
8.
9.
F F?ndrich AM Waaga J Schr?der E Schweizer A Schmid S Jacob HH Wacker P Schroeder 《Canadian Metallurgical Quarterly》1995,27(2):1553-1554
10.
This study addressed the issue of adjustment among Holocaust survivors by multidimensional assessment of subjective well-being (SWB). Participants were Israeli Holocaust survivors incidentally included in a life-span study (Group 1; n?=?466) or purposely approached for studying Holocaust survivors (Group 2; n?=?178). Comparison participants had immigrated to Israel before World War II, with their parents either undergoing (Group 3; n?=?270) or not undergoing the Holocaust (Group 4; n?=?388); other comparison participants had immigrated after the war with parents not undergoing the Holocaust (Group 5; n?=?166). Results showed that Group 1 scored lower than Group 2, mainly in positive affect. Group 1 scored lower than Group 4, and to a lesser extent also lower than Groups 3 and 5, mainly in aging-related themes of SWB. The study suggests that long-term effects of the Holocaust on the survivors' SWB are traceable but require a differential approach to the study groups and to the facets of SWB. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献