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   567486篇
  免费   6227篇
  国内免费   1004篇
电工技术   10521篇
综合类   466篇
化学工业   90200篇
金属工艺   23349篇
机械仪表   18511篇
建筑科学   12537篇
矿业工程   4312篇
能源动力   14464篇
轻工业   45806篇
水利工程   6941篇
石油天然气   14962篇
武器工业   39篇
无线电   60325篇
一般工业技术   116344篇
冶金工业   95765篇
原子能技术   14705篇
自动化技术   45470篇
  2021年   5495篇
  2019年   5270篇
  2018年   9213篇
  2017年   9413篇
  2016年   9838篇
  2015年   6029篇
  2014年   10252篇
  2013年   26126篇
  2012年   15810篇
  2011年   21149篇
  2010年   16996篇
  2009年   18833篇
  2008年   19096篇
  2007年   18793篇
  2006年   16309篇
  2005年   14757篇
  2004年   14025篇
  2003年   13703篇
  2002年   13268篇
  2001年   12856篇
  2000年   12339篇
  1999年   12025篇
  1998年   27746篇
  1997年   20088篇
  1996年   15653篇
  1995年   12026篇
  1994年   10875篇
  1993年   10626篇
  1992年   8341篇
  1991年   8109篇
  1990年   8002篇
  1989年   7773篇
  1988年   7484篇
  1987年   6750篇
  1986年   6541篇
  1985年   7395篇
  1984年   6704篇
  1983年   6445篇
  1982年   5780篇
  1981年   5902篇
  1980年   5633篇
  1979年   5733篇
  1978年   5667篇
  1977年   6183篇
  1976年   7693篇
  1975年   5111篇
  1974年   4903篇
  1973年   4981篇
  1972年   4280篇
  1971年   4041篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
A microprocessor-based system with 32 A/D, 24 D/A, and 16 ac load controllers, has been designed and built to monitor and control an ion beam thin-film deposition system. The A/D and D/A channels have electrical isolation of 7.5 kV between channels and between input and output. The microprocessor system keeps the ion beam deposition parameters stable for extended periods of operation and it is proposed as a means to greatly simplify switching from one deposition species to another to grow thin multilayer or alloy films.  相似文献   
93.
94.
Translated from Atomnaya Énergiya, Vol. 67, No. 2, pp. 111–113, August, 1989.  相似文献   
95.
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 2, pp. 14–15, February, 1989.  相似文献   
96.
We investigate the saturation effects of power broadening, Stark shifting, and population transfer on Stokes conversion in stimulated Raman scattering. We do not make the usual rotating wave approximation because the detuning from the next electronic state is assumed to be in the optical regime. Retaining the counter-rotating terms allows an exact determination of the pump and Stokes indexes of refraction. Steady-state solutions for the Stokes intensity and phase are obtained and the effects of making the rotating wave approximation (RWA) are discussed. Finally, we examine the behavior of these solutions for Stokes conversion in hydrogen gas when geometric propagation is appropriate.  相似文献   
97.
The usefulness of selected PCR-protocols for the detection of Salmonella in 117 samples of animal origin (17 raw minced meat, 27 raw chicken meat, 8 raw sausages, and 25 egg samples, as well as 18 poultry faecal, and caecal swabs samples) and DNA-fingerprinting typing is shown. To establish an accurate PCR-procedure for Salmonella detection the following parameters were evaluated: two pre-PCR concentration procedures, centrifugation and immunomagnetic separation (IMS) using Dynabeads anti- Salmonella; the specificity and sensitivity of 10 sets of primers; and different conditions of the amplification reaction. In light of the results obtained from the use of PCR-based procedures alone or in combination with conventional methods, the following findings can be underlined: First, IMS is more efficient than centrifugation in the recovery of Salmonella. Second, the selected IMS/PCR-detection protocol is less time-consuming (45 h) than the IMS/culture procedure (90 h), and a good concordance between them was found when the Kappa coefficient was calculated (0·87). Third, PCR-ribotyping technique showed a very low discrimination power, being able to differentiate only three profiles. Fourth, RAPD technique using specific primers supports previous works in which it was proposed as a simple and useful tool for discriminating isolates between and within serotypes. Fifth, The efficiency, rapidity, and flexibility of the PCR-protocols applied were high, and they can be performed using two PCR-programs and the same basic equipment.  相似文献   
98.
99.
Consideration was given to the decision making procedures based on the fuzzy messages of experts whose preferences on the set of collective decisions can also be fuzzy.  相似文献   
100.
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