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   295935篇
  免费   22807篇
  国内免费   14552篇
电工技术   18965篇
技术理论   59篇
综合类   42302篇
化学工业   30911篇
金属工艺   10841篇
机械仪表   16266篇
建筑科学   43383篇
矿业工程   16753篇
能源动力   8630篇
轻工业   16619篇
水利工程   16323篇
石油天然气   12468篇
武器工业   2726篇
无线电   19427篇
一般工业技术   20157篇
冶金工业   16835篇
原子能技术   2791篇
自动化技术   37838篇
  2024年   897篇
  2023年   2718篇
  2022年   5324篇
  2021年   6296篇
  2020年   6720篇
  2019年   5579篇
  2018年   5278篇
  2017年   6593篇
  2016年   7824篇
  2015年   8989篇
  2014年   17461篇
  2013年   15052篇
  2012年   19640篇
  2011年   21002篇
  2010年   16710篇
  2009年   17630篇
  2008年   16433篇
  2007年   21521篇
  2006年   20409篇
  2005年   17713篇
  2004年   14912篇
  2003年   13433篇
  2002年   11001篇
  2001年   9302篇
  2000年   7840篇
  1999年   6344篇
  1998年   4703篇
  1997年   4090篇
  1996年   3796篇
  1995年   3193篇
  1994年   2853篇
  1993年   2147篇
  1992年   1881篇
  1991年   1399篇
  1990年   1231篇
  1989年   1084篇
  1988年   869篇
  1987年   588篇
  1986年   447篇
  1985年   367篇
  1984年   347篇
  1983年   252篇
  1982年   218篇
  1981年   181篇
  1980年   145篇
  1979年   118篇
  1978年   69篇
  1977年   75篇
  1976年   57篇
  1975年   64篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
从理论上探讨了磁阻率效应,叙述了精密角位移传感器的工作原理及结构设计。传感器的分辨率已达0.01°,通过可靠性寿命试验,传感器的失效率λ(t)<1×10-7/h。  相似文献   
192.
S Chattopadhyay  P P Das 《Sadhana》1993,18(2):349-364
Reconstruction of an original continuous curve and the estimation of its parameters from the digitized version of the curve is a challenging problem, as quantization always causes some loss of information. In this paper, we have developed a scheme for reconstruction which is applicable to a class of curves having at the most two parameters. The class of curves for which the scheme works has also been characterized. We have shown that for one-parameter curves the exact domain of values of the parameter can be obtained. But in the two-parameter case, only the smallest rectangle containing the domain can be realised. The distinctive feature of our scheme is that it provides a unified approach to solve the reconstruction and the domain-finding problem for a class of curves.  相似文献   
193.
王冰 《水力发电》1994,(10):27-31
随着GIS的工作电压不断提高和发展,一系列新的现象和问题也同时出现。从国外一些科研,设计,制造部门所研究发表的内容看,大致有隔离开关操作和高速瞬变过程,粒子影响和对干扰定位的技术,元件的监督,现场试验等课题,本文对以上问题加以综合介绍。  相似文献   
194.
Editorial.     
With this volume, the 47-year old Canadian Journal of Psychology takes a new name and makes a renewed commitment. In retitling the journal the Canadian Journal of Experimental Psychology, the intention is to reflect more clearly what has always been the major goal of the journal--to publish the best new research in experimental psychology, both Canadian and international, in both French and English. I am honoured to become the tenth editor of the major journal for experimental psychology in Canada. CJP has served the field very well; my primary goal is to ensure that CJEP continues to do so. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
195.
Sensitivity analysis is used to show how uncertainties in basic factors, such as heat transfer, pressure drop, compressor efficiency, and thermophysical properties, influence the result of heat pump cycle performance estimations. By comparing the results of this analysis with uncertainty levels of estimations and experimental determinations, it is established to what extent improvements in accuracy are needed. The investigation was carried out for several different applications and, as working fluids, both pure substances and non-azeotropic mixtures were examined. It was found that evaporation heat transfer and compressor efficiency are two areas where improvements are needed. It is also shown that estimates using very accurate, substance-specific, equations of state differ from those using more general types by up to 1 % for COP and 2% for capacity.  相似文献   
196.
A semi-analytic boundary element method for parabolic problems   总被引:1,自引:0,他引:1  
A new semi-analytic solution method is proposed for solving linear parabolic problems using the boundary element method. This method constructs a solution as an eigenfunction expansion using separation of variables. The eigenfunctions are determined using the dual reciprocity boundary element method. This separation of variables-dual reciprocity method (SOV-DRM) allows a solution to be determined without requiring either time-stepping or domain discretisation. The accuracy and computational efficiency of the SOV-DRM is found to improve as time increases. These properties make the SOV-DRM an attractive technique for solving parabolic problems.  相似文献   
197.
198.
中等职业学校一般开设VB、VC及数据库等涉及程序设计的计算机课程。本文拟就程序设计中一题多解的教学方法进行探讨。  相似文献   
199.
In order to control a project, construction management requires project information. This is obtained through accounting, estimating, cost management and scheduling functions which produce project reports. These reports are best obtained by subdividing the project into small parts. The ways in which each of these functions subdivides a project in order to produce its reports is discussed, together with a means of interrelating this information with a technique known as the work breakdown structure.  相似文献   
200.
应用现代可靠性理论,从设计、工艺、技术等方面对油田集输系统进行了可靠性探讨,提出了增强系统可靠性的措施。  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