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   1557291篇
  免费   24523篇
  国内免费   7047篇
电工技术   35175篇
综合类   6444篇
化学工业   275094篇
金属工艺   65885篇
机械仪表   45629篇
建筑科学   47227篇
矿业工程   11832篇
能源动力   50400篇
轻工业   118155篇
水利工程   15832篇
石油天然气   38358篇
武器工业   147篇
无线电   199206篇
一般工业技术   294368篇
冶金工业   178266篇
原子能技术   34622篇
自动化技术   172221篇
  2021年   15560篇
  2020年   11870篇
  2019年   14652篇
  2018年   18496篇
  2017年   18294篇
  2016年   22631篇
  2015年   17513篇
  2014年   28640篇
  2013年   87914篇
  2012年   37203篇
  2011年   51884篇
  2010年   45340篇
  2009年   53323篇
  2008年   47730篇
  2007年   45590篇
  2006年   45783篇
  2005年   41624篇
  2004年   42933篇
  2003年   42622篇
  2002年   41424篇
  2001年   37968篇
  2000年   36334篇
  1999年   35448篇
  1998年   49173篇
  1997年   41940篇
  1996年   37005篇
  1995年   31750篇
  1994年   29571篇
  1993年   29407篇
  1992年   26442篇
  1991年   23604篇
  1990年   23952篇
  1989年   23040篇
  1988年   21543篇
  1987年   19791篇
  1986年   19150篇
  1985年   22499篇
  1984年   22488篇
  1983年   20481篇
  1982年   19386篇
  1981年   19458篇
  1980年   18097篇
  1979年   18610篇
  1978年   17840篇
  1977年   17798篇
  1976年   18961篇
  1975年   16091篇
  1974年   15567篇
  1973年   15682篇
  1972年   13147篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
The dynamic and equilibrium swelling behavior of polystyrene microparticles crosslinked with divinyl benzene was investigated in methyl ethyl ketone and cyclohexane. The dynamic studies gave new information about the mechanism of penetrant transport in this polymer. The equilibrium studies were used to determine important parameters of the crosslinked structure of these systems, including the average molecular weight between crosslinks, M?c  相似文献   
952.
Field surveys of a series of conjugated diunsaturated straight-chain primary alcohols, acetates, and aldehydes (dienes), including the 3,5-dode-cadienyl, 8,10-dodecadienyl, 3,5-tetradecadienyl, 8,10-tetradecadienyl, 9,11-tetradecadienyl, and 10,12-tetradecadienyl primary alcohols, acetates, and most aldehydes, and the related monounsaturated straight-chain primary alcohols, acetates, and aldehydes (monoenes), including the 3-dodecadienyl alcohol and acetates, attracted the following species from the title families. Diene attractants have been demonstrated for at least onePhyllonorycter sp.,Chionodes lugubrella (Fabr.),Leptostales ferruminaria (Zell.),Drepana bilineata (Pack.),Pyrausta fodinalis (Led.),Notocelia purpurissatana Heinr.,Phaneta alterana Heinr. Monoene attractants were demonstrated forHedya separatana (Kft.),Cydia fletcherana (Kft.),Barbara mappana Free.,Ancylis burgessiana (Zell.),Ancylis nubeculana Clem.,Evippe prunifoliella Cham.,Phlyctaenia coronata tertialis (Gn.), aChionodes sp., a Gelechiidae sp., and an unidentifiedPhyllonorycter sp. Replicated field experiments showed attraction-inhibition relationships for most species. Electroantennagram data are presented forLeptostales ferruminaria andDrepana bilineata.  相似文献   
953.
Summary Starting with Z-2, 3-diamino-2-butenedinitrile as diamine component the synthesis of the low molecular N,N,O,O-chelate 3.Co and its ligand 3 is optimized. An easy synthesis of the chelate 8.Co covalently bound on macroreticular resins is presented. The chelates 8.Co are the most active heterogenous catalysts for the valence isomerization of quadricyclane to norbornadiene today.  相似文献   
954.
For the past three decades, IS managers have been faced with the tasks of honing their craft, improving productivity, and serving as the keepers of information technology for the corporation. For the most part, they have done a commendable job. However, the rules of the game are changing. Old solutions are no longer extensible to current problems, and today's problems are unlike any faced in the past. This article takes a fresh look at what the top priorities for IS managers should be in the coming years.  相似文献   
955.
The survey focuses on algebraic-grammatical models of parallel processes, representation of knowledge about classes of algorithms in terms of a variety of production systems (structured design grammars), and program generation tools.Translated from Kibernetika i Sistemnyi Analiz, No. 5, pp. 5–13, September–October, 1991.  相似文献   
956.
An efficient algorithm to remove redundant dependences in simple loops with constant dependences is presented. Dependences constrain the parallel execution of programs and are typically enforced by synchronization instructions. The synchronization instructions represent a significant part of the overhead in the parallel execution of a program. Some program dependences are redundant because they are covered by other dependences. It is shown that unlike with single loops, in the case of nested loops, a particular dependence may be redundant at some iterations but not redundant at others, so that the redundancy of a dependence may not be uniform over the entire iteration space. A sufficient condition for the uniformity of redundancy in a doubly nested loop is developed  相似文献   
957.
Translated from Atomnaya Énergiya, Vol. 66, No. 6, pp. 423–424, June, 1989.  相似文献   
958.
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989.  相似文献   
959.
960.
Geomechanical aspects of the storage of radioactive waste in salt formations have been studied extensively using finite element methods over the last 20 years. In consequence a range of computer programs and associated modelling techniques have been assembled. The paper is based on a benchmark exercise to compare the predictive abilities of a number of these programs and highlights the difficulties of making reliable a-priori estimates of long term behaviour.  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