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   1593120篇
  免费   25002篇
  国内免费   7041篇
电工技术   34559篇
综合类   6530篇
化学工业   274974篇
金属工艺   65187篇
机械仪表   44729篇
建筑科学   48423篇
矿业工程   11494篇
能源动力   50445篇
轻工业   125826篇
水利工程   16120篇
石油天然气   37572篇
武器工业   136篇
无线电   198304篇
一般工业技术   299137篇
冶金工业   203467篇
原子能技术   33998篇
自动化技术   174262篇
  2021年   15685篇
  2019年   14757篇
  2018年   16127篇
  2017年   15380篇
  2016年   21787篇
  2015年   17542篇
  2014年   28950篇
  2013年   88276篇
  2012年   37927篇
  2011年   51260篇
  2010年   43566篇
  2009年   51462篇
  2008年   47563篇
  2007年   45149篇
  2006年   47015篇
  2005年   41479篇
  2004年   43807篇
  2003年   43537篇
  2002年   42407篇
  2001年   39683篇
  2000年   37746篇
  1999年   37322篇
  1998年   56998篇
  1997年   46682篇
  1996年   40455篇
  1995年   33945篇
  1994年   31551篇
  1993年   31054篇
  1992年   27171篇
  1991年   24442篇
  1990年   24607篇
  1989年   23704篇
  1988年   22281篇
  1987年   20380篇
  1986年   19955篇
  1985年   23341篇
  1984年   23069篇
  1983年   21010篇
  1982年   19710篇
  1981年   19844篇
  1980年   18480篇
  1979年   19053篇
  1978年   18180篇
  1977年   18854篇
  1976年   21421篇
  1975年   16322篇
  1974年   15851篇
  1973年   15924篇
  1972年   13415篇
  1971年   11994篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Haug  K. Maloberti  F. Temes  G.C. 《Electronics letters》1985,21(24):1156-1157
Compensated SC integrator stages are analysed and compared with respect to their sensitivities to finite amplifier gain effects. Simple single-stage amplifiers may be used in such circuits even in highly selective filtering applications. This may allow an extension of the present frequency range of SC circuits.  相似文献   
992.
The paper presents the results of research in the convection drying of unidirectional glass fibre bobbins on the basis of which the relations are suggested required to calculate the process of drying in the design of drying equipment.  相似文献   
993.
994.
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   
995.
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   
996.
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   
997.
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   
998.
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   
999.
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   
1000.
Naphthalene-2,3-dicarboxaldehyde (NDA) has been investigated as a new derivatizing reagent for the electrochemical detection of tagged amino acids. Gradient elution allowed for the separation of 18 NDA-derivatized amino acids on an open tubular liquid chromatography column in less than 50 min. Gradient elution and electrochemical detection were found to be compatible. A detection limit of 36 amol was obtained for the asparagine-NDA derivative. The usefulness of this technique for quantitation was demonstrated by the analysis of the NDA-tagged hydrolysis products from bovine chymotrypsinogen.  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