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   572347篇
  免费   6492篇
  国内免费   1040篇
电工技术   10667篇
综合类   486篇
化学工业   91191篇
金属工艺   23437篇
机械仪表   18611篇
建筑科学   12724篇
矿业工程   4317篇
能源动力   14796篇
轻工业   46311篇
水利工程   7015篇
石油天然气   15028篇
武器工业   43篇
无线电   60987篇
一般工业技术   117158篇
冶金工业   95893篇
原子能技术   14743篇
自动化技术   46472篇
  2021年   5860篇
  2020年   4283篇
  2019年   5551篇
  2018年   9567篇
  2017年   9673篇
  2016年   10131篇
  2015年   6185篇
  2014年   10506篇
  2013年   26526篇
  2012年   16073篇
  2011年   21437篇
  2010年   17187篇
  2009年   19000篇
  2008年   19230篇
  2007年   18925篇
  2006年   16412篇
  2005年   14852篇
  2004年   14102篇
  2003年   13764篇
  2002年   13334篇
  2001年   12885篇
  2000年   12377篇
  1999年   12062篇
  1998年   27732篇
  1997年   20110篇
  1996年   15680篇
  1995年   12062篇
  1994年   10892篇
  1993年   10642篇
  1992年   8354篇
  1991年   8111篇
  1990年   8006篇
  1989年   7787篇
  1988年   7506篇
  1987年   6766篇
  1986年   6548篇
  1985年   7416篇
  1984年   6735篇
  1983年   6464篇
  1982年   5791篇
  1981年   5912篇
  1980年   5654篇
  1979年   5744篇
  1978年   5676篇
  1977年   6197篇
  1976年   7706篇
  1975年   5121篇
  1974年   4918篇
  1973年   4991篇
  1972年   4286篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Unsatisfactory conditions of storage of decontamination waste (DW) in the storages formed in the territory of Belarus after the Chernobyl accident require the evaluation of the level of protection of the environment and population. The potential hazard of the decontamination waste burial grounds (DWBGs) has been evaluated based on the use of a generalized multichamber model that was verified by comparing the calculation results and the results obtained by the American (GW SCREEN) model. The characteristics of the 24 largest and most hazardous DWBGs are given and the evaluations of their safety are presented. The zones of influence of these storages, whose size varies from 100 to 330 m, have been determined. The reliability of the prediction evaluation of a possible hazardous radioactive contamination of water near the storages has been verified using the Dudichi DWBG as an example.  相似文献   
992.
The high-temperature operation of a silicon carbide gate turn-off thyristor is evaluated for use in inductively loaded switching circuits. Compared to purely resistive load elements, inductive loads subject the switching device to higher internal power dissipation. The ability of silicon carbide components to operate at elevated temperatures and high power dissipations are important factors for their use in future power conversion/control systems. In this work, a maximum current density of 540 A/cm2 at 600 V was switched at a frequency of 2 kHz and at several case temperatures up to 150°C. The turn-off and turn-on characteristics of the thyristor are discussed  相似文献   
993.
There are several psychiatric illnesses that are difficult to treat with drugs. Among these are schizophrenia, manic depression, and profound depression; many of these may involve a tendency to suicide. In 1938 U. Cerletti conducted convulsive experiments on pigs using power-line current applied to electrodes at various sites. The effect of current duration was also investigated. As yet it is not known which areas in the brain are the optimum targets for the therapeutic use of cranially applied current to treat psychiatric illnesses, although the frontal lobes appear to be the best targets.  相似文献   
994.
995.
Writing project reports is an important part of the engineering curriculum at Singapore universities. One important section of the formal report is the literature review. Most universities around the world provide guidelines on writing reviews, emphasizing that plagiarism is unethical. However, these guidelines do not offer explicit training on how to avoid plagiarism. In order to write academically acceptable reviews while avoiding copying from source materials, students face a major challenge and resort to employing various strategies to cope with the task. In this study, we examined the literature review sections of final year project reports to find out how engineering undergraduates in a Singapore university cope with writing reviews and to suggest ways in which they can extend their skills to improve their literature reviews.  相似文献   
996.
997.
998.
This paper describes the work done by the Autonomous Systems Lab of Ecole Polytechnique Federale de Lausanne (EPFL) on the global design of an unmanned solar airplane that can fly continuously over days and night. Part of the Sky-Sailor Project, a first prototype was designed and demonstrated to have very good flight characteristics. The prototype achieved an autonomous flight of five hours with its energy only from the sun. A lightweight control and navigation system was also designed for the aircraft.  相似文献   
999.
1000.
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