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   702440篇
  免费   17913篇
  国内免费   7065篇
电工技术   18598篇
技术理论   9篇
综合类   9169篇
化学工业   112357篇
金属工艺   30982篇
机械仪表   26816篇
建筑科学   22014篇
矿业工程   7834篇
能源动力   17881篇
轻工业   54973篇
水利工程   9621篇
石油天然气   22234篇
武器工业   1084篇
无线电   75270篇
一般工业技术   134910篇
冶金工业   102844篇
原子能技术   17225篇
自动化技术   63597篇
  2022年   8041篇
  2021年   11208篇
  2020年   8297篇
  2019年   8785篇
  2018年   13269篇
  2017年   13876篇
  2016年   13799篇
  2015年   11136篇
  2014年   16640篇
  2013年   33749篇
  2012年   24223篇
  2011年   30074篇
  2010年   24625篇
  2009年   26252篇
  2008年   26431篇
  2007年   25630篇
  2006年   22880篇
  2005年   20363篇
  2004年   18153篇
  2003年   17817篇
  2002年   17457篇
  2001年   16651篇
  2000年   15506篇
  1999年   14944篇
  1998年   29906篇
  1997年   21865篇
  1996年   17278篇
  1995年   13498篇
  1994年   12056篇
  1993年   11551篇
  1992年   9195篇
  1991年   8805篇
  1990年   8609篇
  1989年   8332篇
  1988年   7967篇
  1987年   7181篇
  1986年   6889篇
  1985年   7706篇
  1984年   6995篇
  1983年   6699篇
  1982年   6067篇
  1981年   6188篇
  1980年   5902篇
  1979年   6046篇
  1978年   5993篇
  1977年   6480篇
  1976年   8016篇
  1975年   5426篇
  1974年   5202篇
  1973年   5291篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
Translated from Atomnaya Énergiya, Vol. 67, No. 2, pp. 111–113, August, 1989.  相似文献   
112.
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 2, pp. 14–15, February, 1989.  相似文献   
113.
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   
114.
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   
115.
The properties of the solutions of optimal parametric filtration equations and an adaptive variant of the problem with regard for time-drift of the unknown parameters of the system are studied. Along with the Kalman interpretation of the optimal adaptive nonlinear filter, the Bayes approach to applying the respective a posteriori densities is also studied.  相似文献   
116.
117.
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   
118.
119.
120.
The paper describes new experimental evidence on the effects of fast neutron irradiation on the nucleation of bubbles in superheated demineralized water during sudden depressurization. The experimental range covered strating pressures of (0.33–6.0) MPa. It was shown that fast neutron irradiation causes significant increases in the bubble formation for specified conditions of pressure, temperature and rate of blowdown. A mechanistic interpretation of the measurements based on a thermodynamic model was included, and comparison was made, in terms of void fraction, with the experimental results.  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