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   172091篇
  免费   12340篇
  国内免费   6168篇
电工技术   8799篇
技术理论   9篇
综合类   8805篇
化学工业   28708篇
金属工艺   10181篇
机械仪表   10421篇
建筑科学   9911篇
矿业工程   3971篇
能源动力   3936篇
轻工业   9740篇
水利工程   3172篇
石油天然气   9632篇
武器工业   1061篇
无线电   18338篇
一般工业技术   27828篇
冶金工业   11249篇
原子能技术   4876篇
自动化技术   19962篇
  2024年   726篇
  2023年   2388篇
  2022年   4699篇
  2021年   6403篇
  2020年   4849篇
  2019年   4191篇
  2018年   5320篇
  2017年   5790篇
  2016年   5343篇
  2015年   5835篇
  2014年   7593篇
  2013年   9261篇
  2012年   9897篇
  2011年   10656篇
  2010年   9047篇
  2009年   8865篇
  2008年   8741篇
  2007年   8093篇
  2006年   7517篇
  2005年   6458篇
  2004年   4960篇
  2003年   4878篇
  2002年   4875篇
  2001年   4442篇
  2000年   3843篇
  1999年   3438篇
  1998年   2711篇
  1997年   2281篇
  1996年   2049篇
  1995年   1779篇
  1994年   1517篇
  1993年   1266篇
  1992年   1238篇
  1991年   1098篇
  1990年   1107篇
  1989年   1031篇
  1988年   902篇
  1987年   849篇
  1986年   767篇
  1985年   721篇
  1984年   710篇
  1981年   673篇
  1979年   740篇
  1978年   781篇
  1977年   742篇
  1976年   755篇
  1975年   713篇
  1974年   719篇
  1973年   726篇
  1972年   707篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches.  相似文献   
82.
83.
The kinetics of glycidyl methacrylate block polymerization to high conversion was experimentally investigated with variations of the photoinitiator concentration, temperature, and power of UV illumination. The kinetic curves of this polymerization process contain three characterized sections of coordinates of “conversion–time,” namely: The first one is practically linear to a conversion of ≈0.5, the second represents, by itself, the autoacceleration process, and the third presents the autodecelation process. An additional peculiarity of such a polymerization process is poor reproduction of the kinetic measurements. This reproduction does not correspond to instrumental error. Derivation of a kinetic model for block linear polymerization was done. This model is, quantitatively, in good agreement with all the data of the experimental material. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3556–3569, 2002  相似文献   
84.
The effect of turbulizing asperities positioned on one of the walls of a plane channel on the intensity of exchange processes near a smooth wall with injection of different working media is studied experimentally. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 404–408, 1997.  相似文献   
85.
86.
Scientific-Technical Center “Atomtekhénergo.” Leningrad Nuclear Power Plant. N. V. Sultanov Institute of Nuclear Reactors, Russian Scientific Center “Kurchatovskii institut.” Translated from Atomnaya énergiya, Vol. 76, No. 6, pp. 470–473, June, 1994.  相似文献   
87.
88.
89.
Analytical solution of a system of nonlinear measuring equations of a 12-pole microwave reflectometer was obtained. Criteria for selecting a true solution in the general case were developed and the analysis was conducted for a number of particular cases that may generate practical interest.  相似文献   
90.
The formation specifics of the structure and phase composition of densely sintered ceramics based on a low-melting argillaceous material from Belarus together with a combined flux and a grog additive are investigated. The correlation between the physicochemical properties, structure, phase composition, and the time-temperature firing schedules of the developed materials are investigated. Electron probe microanalysis makes it possible to monitor variations in the chemical composition at various local sites and compare it with the estimated composition of the mixture. The optimum regimes for the heat treatment of articles are determined. __________ Translated from Steklo i Keramika, No. 6, pp. 32 – 36, June, 2005.  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