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   658650篇
  免费   8523篇
  国内免费   1955篇
电工技术   12238篇
综合类   621篇
化学工业   97443篇
金属工艺   25039篇
机械仪表   18896篇
建筑科学   15593篇
矿业工程   2836篇
能源动力   17823篇
轻工业   55857篇
水利工程   6356篇
石油天然气   11160篇
武器工业   44篇
无线电   77858篇
一般工业技术   126792篇
冶金工业   133432篇
原子能技术   12815篇
自动化技术   54325篇
  2021年   5708篇
  2020年   4139篇
  2019年   5415篇
  2018年   9144篇
  2017年   8916篇
  2016年   9314篇
  2015年   6527篇
  2014年   10941篇
  2013年   29764篇
  2012年   17420篇
  2011年   24069篇
  2010年   19077篇
  2009年   21469篇
  2008年   22075篇
  2007年   21777篇
  2006年   19148篇
  2005年   17668篇
  2004年   17085篇
  2003年   16752篇
  2002年   15930篇
  2001年   16172篇
  2000年   15109篇
  1999年   16203篇
  1998年   42385篇
  1997年   29418篇
  1996年   22655篇
  1995年   16910篇
  1994年   14686篇
  1993年   14414篇
  1992年   10234篇
  1991年   9725篇
  1990年   9507篇
  1989年   9164篇
  1988年   8475篇
  1987年   7375篇
  1986年   7282篇
  1985年   8217篇
  1984年   7581篇
  1983年   6710篇
  1982年   6276篇
  1981年   6479篇
  1980年   6049篇
  1979年   5857篇
  1978年   5631篇
  1977年   6838篇
  1976年   9015篇
  1975年   4884篇
  1974年   4603篇
  1973年   4655篇
  1972年   3843篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Abstract This article presents a study of a large scale incorporation of one data acquisitionsystem into physics teaching in Israel. By 1994 about 30% of the schools throughout the country used the V-scope, a 3-D multibody motion tracing system, in their lab programme. The views and reactions of post-training teachers, experienced teachers and students on various aspects of using the system are described, analysed and compared.  相似文献   
103.
Gilbenclamide, a widely used potent hypoglycaemic agent was solubllized using β -Cyclodextrin and β -Cyclodextrin derivatives. Complexes were prepared by kneading method in a molar ratio of 1:1 of the drug and the cyclodextrlns respectively. The Glibenclamide β -Cyelocextrin complex was characterized and evaluated by I.R. studies, Differential Scanning Calorimotry 6 X-ray diffractometry. The in-vitro dissolution rates of drug from inclusion complexes of β Cyclodextrins and its derivatives were compared. A significant Improvement In dissolution lor, rates of Gllbenclamide was observed with Inclusion complexes of all the Cyclodextrins. However, the solubilizing effect was more in case of β-Cyclodextrin derivatives.  相似文献   
104.
105.
106.
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   
107.
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989.  相似文献   
108.
109.
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing.  相似文献   
110.
An all-optical multiplexing technique using wavelength division multiplexing (WDM)-time division multiplexing (TDM) conversion with an electroabsorption wavelength converter has been proposed and demonstrated. The effectiveness of this WDM-TDM conversion technique for various pulsewidth settings was experimentally investigated. The fluctuation of the signal performance, which was inevitably caused by the coherent crosstalk between adjacent pulses in the conventional optical time division multiplexing (OTDM) technique, were successfully suppressed, even in the case of wide pulse duration. High Q-factor performance has been maintained for a wide range of duty ration from 36% to 74%. By introducing this technique to the optical time division multiplexer, a highly stable and high-quality 40-Gb/s optical signal can be effectively produced without generating the short pulse or setting two tributaries at orthogonal polarization states, and without introducing high-speed electronics for signal multiplexing. The WDM-TDM conversion with an electroabsorption wavelength converter was extended to 60-Gb/s operation by using three 20-Gb/s tributaries. A clear eye opening was confirmed for a waveform after the WDM-TDM conversion of the 60-Gb/s signal  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