首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2900篇
  免费   125篇
  国内免费   1篇
电工技术   29篇
综合类   2篇
化学工业   804篇
金属工艺   61篇
机械仪表   65篇
建筑科学   94篇
矿业工程   4篇
能源动力   93篇
轻工业   174篇
水利工程   15篇
石油天然气   7篇
无线电   275篇
一般工业技术   587篇
冶金工业   419篇
原子能技术   12篇
自动化技术   385篇
  2023年   23篇
  2022年   51篇
  2021年   84篇
  2020年   61篇
  2019年   66篇
  2018年   72篇
  2017年   57篇
  2016年   88篇
  2015年   57篇
  2014年   72篇
  2013年   156篇
  2012年   143篇
  2011年   158篇
  2010年   132篇
  2009年   110篇
  2008年   147篇
  2007年   133篇
  2006年   106篇
  2005年   97篇
  2004年   93篇
  2003年   68篇
  2002年   72篇
  2001年   57篇
  2000年   58篇
  1999年   42篇
  1998年   84篇
  1997年   55篇
  1996年   54篇
  1995年   53篇
  1994年   44篇
  1993年   41篇
  1992年   32篇
  1991年   24篇
  1990年   28篇
  1989年   24篇
  1988年   22篇
  1987年   24篇
  1986年   21篇
  1985年   19篇
  1984年   23篇
  1983年   27篇
  1982年   17篇
  1981年   21篇
  1979年   13篇
  1978年   24篇
  1977年   21篇
  1976年   25篇
  1975年   17篇
  1974年   18篇
  1973年   15篇
排序方式: 共有3026条查询结果,搜索用时 15 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.
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.
7.
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   
8.
9.
10.
In future broadband communication networks the interest for purely photonic switches is due to the bandwidth mismatch between optical transmission networks and electronic switching nodes. Photonic ATM switching fabrics mainly based on wavelength-switching stages are therefore being studied, to implement high capacity switches with also concentration, multiplexing and demultiplexing functions, using state-of-the-art photonic technology. The architecture of an ATM photonic access concentrator is described in this paper, illustrating the design and implementation of its basic subsystems, the traffic concentrator and the cell multiplexer. The design guidelines are outlined in detail referring to an example, where 128 user lines at 622 Mb/s are given access to 4 outlets at 2.488 Gb/s. The corresponding implementation, based on the systematic use of cell wavelength encoding, makes use either of well-known photonic components, such as Fabry-Perot filters, fiber delay lines, splitters and combiners, either of recently developed devices, like high-speed optical gates and tunable filters and lasers. Finally, the system feasibility is demonstrated presenting the results obtained on a reduced size and speed experimental setup of the cell multiplexer  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号