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   2922篇
  免费   125篇
  国内免费   1篇
电工技术   30篇
综合类   2篇
化学工业   799篇
金属工艺   64篇
机械仪表   62篇
建筑科学   95篇
矿业工程   4篇
能源动力   97篇
轻工业   175篇
水利工程   15篇
石油天然气   7篇
无线电   287篇
一般工业技术   591篇
冶金工业   412篇
原子能技术   13篇
自动化技术   395篇
  2023年   23篇
  2022年   51篇
  2021年   86篇
  2020年   62篇
  2019年   65篇
  2018年   72篇
  2017年   57篇
  2016年   86篇
  2015年   58篇
  2014年   73篇
  2013年   158篇
  2012年   145篇
  2011年   159篇
  2010年   131篇
  2009年   107篇
  2008年   146篇
  2007年   133篇
  2006年   106篇
  2005年   96篇
  2004年   94篇
  2003年   68篇
  2002年   74篇
  2001年   60篇
  2000年   58篇
  1999年   44篇
  1998年   81篇
  1997年   54篇
  1996年   51篇
  1995年   53篇
  1994年   42篇
  1993年   42篇
  1992年   33篇
  1991年   26篇
  1990年   29篇
  1989年   24篇
  1988年   26篇
  1987年   28篇
  1986年   21篇
  1985年   19篇
  1984年   23篇
  1983年   29篇
  1982年   17篇
  1981年   23篇
  1980年   14篇
  1978年   24篇
  1977年   23篇
  1976年   24篇
  1975年   18篇
  1974年   19篇
  1973年   16篇
排序方式: 共有3048条查询结果,搜索用时 15 毫秒
1.
2.
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   
3.
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   
4.
5.
6.
7.
8.
We report herein the phenotypic and functional analysis of human bone marrow and thymus derived early T cells. Commitment to T cell lineage is acquired during CD7 antigen expression by CD34+ precursors in human bone marrow and before thymus colonization. Early thymocytes show similar phenotypic characteristics as bone marrow T cells. They rapidly acquire CD4 before the dual expression of CD4 and CD8. Their expansion and differentiation is regulated by two major factors: thymic stroma and cytokines produced by these stroma cells or by thymocytes themselves. Among cytokines, IL1 and sCD23 produced by thymic epithelial cells support in vitro early T cell development.  相似文献   
9.
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   
10.
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