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   1553586篇
  免费   31285篇
  国内免费   10898篇
电工技术   39489篇
技术理论   2篇
综合类   12035篇
化学工业   280925篇
金属工艺   68183篇
机械仪表   45579篇
建筑科学   51541篇
矿业工程   13133篇
能源动力   52432篇
轻工业   113168篇
水利工程   16437篇
石油天然气   41078篇
武器工业   805篇
无线电   205046篇
一般工业技术   285778篇
冶金工业   157294篇
原子能技术   34707篇
自动化技术   178137篇
  2021年   18864篇
  2020年   14084篇
  2019年   16451篇
  2018年   16695篇
  2017年   16469篇
  2016年   22843篇
  2015年   20388篇
  2014年   32683篇
  2013年   92755篇
  2012年   39753篇
  2011年   51728篇
  2010年   46662篇
  2009年   55157篇
  2008年   47955篇
  2007年   44608篇
  2006年   48137篇
  2005年   41724篇
  2004年   42964篇
  2003年   42406篇
  2002年   41735篇
  2001年   38374篇
  2000年   36801篇
  1999年   35841篇
  1998年   43983篇
  1997年   38756篇
  1996年   35296篇
  1995年   30983篇
  1994年   28927篇
  1993年   28697篇
  1992年   26280篇
  1991年   23215篇
  1990年   23562篇
  1989年   22543篇
  1988年   20957篇
  1987年   19224篇
  1986年   18567篇
  1985年   21908篇
  1984年   22228篇
  1983年   20136篇
  1982年   19199篇
  1981年   19294篇
  1980年   17817篇
  1979年   18395篇
  1978年   17657篇
  1977年   17187篇
  1976年   17805篇
  1975年   15904篇
  1974年   15432篇
  1973年   15480篇
  1972年   12984篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
The Six Sigma approach is one of the more recent initiatives adopted by organisations who seek to make a paradigm shift in performance improvement (attacking at least one of the cost, quality, delivery measurements for improved competitiveness). Is there anything new about Six Sigma, does it offer improvements that other approaches cannot, or is it just a clever delivery of repackaged goods? The author investigates the above questions related to the Six Sigma approach  相似文献   
992.
展成式精密电火花加工机床   总被引:1,自引:0,他引:1  
研制了一种展成式精密电火花加工机床,它含有3个回转机构和4个直线移动机构,工件苡轴,工具电极苡轴和转台均可按需要回转,坐标工作台可作纵向和横向移动,工件头架可作轴向和竖向移动。可设置成多种复合运动方式和相应的结构布局,具有很丰富的加工功能,加工精度能达到微米级并实现电火花镜面加工。  相似文献   
993.
994.
995.
This study, which is based on responses from over 300 individuals in England and Wales, explores how a willingness to use a water-recycling system of specific configuration varies against a number of factors which are linked to system design, system scale, system context, and water-conservation behaviour. Findings show that there is broad willingness to accept in-house water recycling provided that public health is not compromised.  相似文献   
996.
Anguilla is a UK overseas (non-independent) territory in the Caribbean. It is a small middle-income island with a population of 13 000, and recent statistics indicate that it is more dependent on tourism than any other country or territory in the world. Rapid population growth and development have placed more emphasis on the need for human health and environmental protection. For the first time, a systematic water-quality monitoring programme has been developed, based on the realities of the local situation, e.g. low resource base, limited capabilities, dependence on household rainwater catchment, storage cisterns, and a poor water-supply network. Development of the programme incorporated the key themes of pragmatic, realistic, incremental, responsive, and consultative approaches.  相似文献   
997.
Cables to moving parts on a linear actuator in production machines, such as pick-and-place machines, are a source of unreliability owing to the possible breaking of a cable. They further reduce the positioning precision of the actuator owing to additional forces. Slotted waveguide systems for rail vehicles based on 2.4 GHz transmission frequency are well known, but transmitters/receivers and waveguides are bulky. The paper reports on the reduction in size of the equipment, adapted to 5.8 GHz using a commercial off-the-shelf RadioLan communication module. Further, the efficient termination of the wave-guide and a new way to reduce standing-wave effects is also discussed.  相似文献   
998.
We present uniaxial tensile test results for 30–50 nm thick freestanding aluminum films. Young’s modulus and ductility were found to decrease monotonically with grain size. Reverse Hall–Petch behavior was observed with no appreciable room temperature creep. Non-linear elasticity with small irreversible deformation was observed for 50 nm thick specimens.  相似文献   
999.
本文分析了目前制约我国城市可持续发展的最主要因素是低效率的土地利用方式 ,若使地上、地面、地下空间协调发展 ,合理科学的规划好地下空间 ,珍惜地下空间资源 ,健全地下空间法律法规 ,统一地下空间管理机构 ,则可高效率的利用土地。  相似文献   
1000.
Following up on recent studies of the Zn-rich corners of the Zn-Fe-Ni and Zn-Fe-Si ternary systems, a 450 °C isothermal section of the Zn-Fe-Ni-Si quaternary phase diagram with the Zn composition being fixed at 93 at.% was determined experimentally using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS), and x-ray diffractometry (XRD). FeSi was found to be in equilibrium with almost all phases in the section, including the T, ζ, Ni-δ, NiSi2, and FeSi2 phases, as well as the liquid phase (L). Silicon solubilities in the T, ζ, and Ni-δ phases were rather limited. However, the solubilities of Fe and Zn in the NiSi2 phase, at 4.5 at.% and 7.2 at.%, respectively, were appreciable. The existence of the (L+NiSi2+Ni-δ) three-phase equilibrium state apparently prevents other Ni-Si compounds from entering equilibrium with the liquid at 450 °C. No true quaternary compound was found in the study.  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