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   307733篇
  免费   25436篇
  国内免费   16184篇
电工技术   21933篇
技术理论   57篇
综合类   42172篇
化学工业   32061篇
金属工艺   10682篇
机械仪表   16430篇
建筑科学   43736篇
矿业工程   17129篇
能源动力   9656篇
轻工业   18770篇
水利工程   16740篇
石油天然气   13828篇
武器工业   3119篇
无线电   20404篇
一般工业技术   21938篇
冶金工业   17519篇
原子能技术   3050篇
自动化技术   40129篇
  2024年   1065篇
  2023年   3174篇
  2022年   6224篇
  2021年   7412篇
  2020年   7874篇
  2019年   6602篇
  2018年   6289篇
  2017年   7580篇
  2016年   8970篇
  2015年   9717篇
  2014年   17550篇
  2013年   16315篇
  2012年   20760篇
  2011年   22083篇
  2010年   17381篇
  2009年   18084篇
  2008年   16985篇
  2007年   22037篇
  2006年   20718篇
  2005年   17885篇
  2004年   15087篇
  2003年   13519篇
  2002年   11036篇
  2001年   9316篇
  2000年   7821篇
  1999年   6400篇
  1998年   4850篇
  1997年   4240篇
  1996年   3880篇
  1995年   3312篇
  1994年   2933篇
  1993年   2185篇
  1992年   1926篇
  1991年   1443篇
  1990年   1243篇
  1989年   1105篇
  1988年   887篇
  1987年   586篇
  1986年   457篇
  1985年   362篇
  1984年   354篇
  1983年   258篇
  1982年   232篇
  1981年   170篇
  1980年   138篇
  1979年   126篇
  1978年   63篇
  1977年   74篇
  1976年   57篇
  1975年   60篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
《数字电路》是中职电类专业的一门专业基础课程。结合目前中职学校教学现状中存在的问题,如何让学生把这门课学好,笔者从精选教材、课堂导入、教学手段、考核评价等方面进行了探讨。指出了只有充分激发起学生的学习兴趣和学习积极性,才是提高教学质量的关键。  相似文献   
992.
新的现代化技术服务于教育是高职院校现代教育发展的必然趋势,文章系统地叙述了高职院校为进一步推动物联网在教育与教学设备监控的应用,做了不断的探索和实践,以期对高职院校的教育与教学设备监控建设工作提供一些借鉴。  相似文献   
993.
结合项目部合作开发报表生成及查询的实际需要,按照公司报表系统通用要求,全力开发易操作且高效率的报表系统。详细阐述报表系统所应用的软硬件环境、系统特点、系统操作说明及在实际工作中应用的优点综述。  相似文献   
994.
航空火警控制盒测试设备是一套主要用于火警控制盒、火警探测器、主告警控制盒、告警控制盒等的校验、故障诊断的设备。介绍了一种基于LabVIEW的航空火警控制盒测试设备的方法,利用PC机中的LabVIEW图形化编程软件采用随机数读取并且显示,再对信号进行分析,对超限信号起到报警功能。  相似文献   
995.
The thermal conductivity, , is one of the few transport coefficients which shows a relatively small change at the solid-liquid phase transition, and hence it is a property that can be used in comparing dynamic properties of both ordered and disordered systems. Although the discontinuity in can be accounted for largely by the difference in density, , of solid and liquid at the phase transition, its volume dependence is examined more closely. The thermal diffusivity, which is known to dominate the dynamic structure factor of liquid argon, has been determined around the phase transition also; the sound velocity has been considered in addition. The results are discussed and a comparison is made with these properties in solid and liquid benzene and cyclohexane.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.  相似文献   
996.
Two experiments, with 80 undergraduates, replicated and extended research by R. T. Croyle and J. Cooper (see record 1984-11595-001) indicating that cognitive dissonance involves physiological arousal. In Exp I, Ss wrote counterattitudinal essays under conditions of high or low choice and, to assess arousal effects owing to effort, with or without a list of arguments provided by the experimenter. In high-choice conditions only and regardless of effort, Ss showed both arousal (heightened galvanic skin response) and attitude change. Arousal, however, did not decline following attitude change. The more effortful task (no arguments provided) produced increased arousal but not greater attitude change. In Exp II, the opportunity to change one's attitude following a freely chosen counterattitudinal essay was manipulated. As in Exp I, arousal increased following the essay but did not decline following a postessay attitude change opportunity. When Ss were not given an attitude change opportunity, however, arousal did decline. It is suggested that if dissonance is a drive state, drive reduction typically may be accomplished through gradual cognitive change or forgetting. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
997.
Compared 2 motivational bases for not contributing to a public good, desire to "free ride" (or greed) and fear of being a "sucker," among 110 Japanese undergraduates. It was hypothesized that these 2 types of motivation would be activated under different situations. When a public good was provided conjunctively, fear would have a strong effect but greed would not; when a public good was disjunctively provided, greed would have a strong effect but fear would not. In addition, it was predicted that the greater mutual trust existing among friends would make them contribute more than strangers would in the conjunctive condition but would make no difference in the disjunctive condition. Three types of production rules, in which a public good was conjunctively, disjunctively, or additively produced on the basis of members' contributions, were experimentally created. Half of the groups in each condition consisted of total strangers, and the other half consisted of friends. The hypotheses were supported when the size of the public good (bonus points) was relatively large. Also, Ss responded similarly in the conjunctive condition and in the additive condition. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
998.
Iron-chromium-cobalt alloys possess attractive magnetic properties combined with good formability and hence are identified as technologically important magnetic materials. Alloys with compositions Fe-28·9 Cr-15·6 Co and Fe-28·4 Cr-20·1Co (weight percent) have been studied. Heat-treatment parameters during thermomagnetic treatment viz temperature, time and external magnetic field were optimized with reference to magnetic properties. The fully treated anisotropic alloys develop remanence=11·5–12·0 kilo Gauss, coercivity=600–650 Oersted and energy product=4–4·5 million Gauss Oersted. Electron microscopic and Mössbauer spectroscopic techniques were used to identify the original and transformed phases. During the various stages of the development of the alloy, the changes in mechanical hardness were correlated with magnetic hardness.  相似文献   
999.
1000.
A faster divide-and-conquer algorithm for constructing delaunay triangulations   总被引:15,自引:0,他引:15  
Rex A. Dwyer 《Algorithmica》1987,2(1):137-151
An easily implemented modification to the divide-and-conquer algorithm for computing the Delaunay triangulation ofn sites in the plane is presented. The change reduces its (n logn) expected running time toO(n log logn) for a large class of distributions that includes the uniform distribution in the unit square. Experimental evidence presented demonstrates that the modified algorithm performs very well forn216, the range of the experiments. It is conjectured that the average number of edges it creates—a good measure of its efficiency—is no more than twice optimal forn less than seven trillion. The improvement is shown to extend to the computation of the Delaunay triangulation in theL p metric for 1<p.This research was supported by National Science Foundation Grants DCR-8352081 and DCR-8416190.  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