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   527626篇
  免费   8298篇
  国内免费   1485篇
电工技术   9624篇
综合类   531篇
化学工业   79540篇
金属工艺   20042篇
机械仪表   15260篇
建筑科学   12797篇
矿业工程   2275篇
能源动力   14696篇
轻工业   47423篇
水利工程   5252篇
石油天然气   9360篇
武器工业   37篇
无线电   60243篇
一般工业技术   102315篇
冶金工业   103731篇
原子能技术   10581篇
自动化技术   43702篇
  2022年   3250篇
  2021年   5015篇
  2020年   3581篇
  2019年   4696篇
  2018年   7998篇
  2017年   7763篇
  2016年   8084篇
  2015年   5673篇
  2014年   9372篇
  2013年   24362篇
  2012年   14790篇
  2011年   20356篇
  2010年   15966篇
  2009年   17859篇
  2008年   18231篇
  2007年   17891篇
  2006年   15621篇
  2005年   14285篇
  2004年   13678篇
  2003年   13479篇
  2002年   12695篇
  2001年   12882篇
  2000年   11919篇
  1999年   12634篇
  1998年   32885篇
  1997年   22928篇
  1996年   17483篇
  1995年   13054篇
  1994年   11303篇
  1993年   10991篇
  1992年   7925篇
  1991年   7430篇
  1990年   7271篇
  1989年   7027篇
  1988年   6482篇
  1987年   5789篇
  1986年   5665篇
  1985年   6274篇
  1984年   5914篇
  1983年   5185篇
  1982年   4908篇
  1981年   4980篇
  1980年   4719篇
  1979年   4613篇
  1978年   4419篇
  1977年   5348篇
  1976年   6982篇
  1975年   3808篇
  1974年   3556篇
  1973年   3677篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
K-winner networks.   总被引:2,自引:0,他引:2  
A special class of mutually inhibitory networks is analyzed, and parameters for reliable K-winner performance are presented. The network dynamics are modeled using interactive activation, and results are compared with the sigmoid model. For equal external inputs, network parameters that select the units with the larger initial activations (the network converges to the nearest stable state) are derived. Conversely, for equal initial activations, networks that select the units with larger external inputs (the network converges to the lowest energy stable state) are derived. When initial activations are mixed with external inputs, anomalous behavior results. These discrepancies are analyzed with several examples. Restrictions on initial states are derived which ensure accurate K-winner performance when unequal external inputs are used.  相似文献   
992.
Conclusions This comparison of two ways of making99Mo shows that there is good scope for making it in any area. If there is a thermal reactor having a high flux, one can make99Mo from98Mo, and in that case, even irradiation in a high flux makes it favorable to use highly enriched98Mo and unblocked targets, which raises the specific activity and thus increases the working life in the99mTc generator.If there is a thermal reactor with low flux or if there is a fast reactor it is best to make99Mo from uranium fission products. The target can be highly enriched235U, which if necessary can be reused, or low-enriched uranium.There are no essential constraints on making99Mo, and the production is mainly based on technological tasks.Translated from Atomnaya Énergiya, Vol. 67, No. 2, pp. 104–108, August, 1989.  相似文献   
993.
994.
995.
996.
997.
Depending on the spectal width of the source illuminating an interferometer, measurement procedures can utilize either the whole interferogram, or only the fringe envelope, or only the fringe quick oscillations. With an ultraband spectrum source, a simplified adaptation of the methods of Fourier transform spectroscopy yields the variations of the test-fiber propagation constant over the whole wavelength-interval of the source. Chromatic dispersion can then be computed from a single interferogram. With narrower spectrum sources, only the fringe envelopes are utilized and yield measurements of mode delay, with application to chromatic and polarization mode dispersion. In this case, however, interferograms at several wavelengths are necessary. With even narrower spectrum sources, the fringe quick oscillations provide measurements of phase shifts, related to changes in the mode propagation constant, when outside perturbations are applied to the test fiber. A direct method for measuring the third-order nonlinear susceptibilities is discussed. In this case the outside perturbation is an intense pump laser field  相似文献   
998.
Kumar  A. Sodha  M.S. 《Electronics letters》1987,23(6):275-276
A general formalism for the study of nonlinear pulse propagation in optical fibres is presented. It is then applied to study the time evolution of a Gaussian laser pulse in a fibre with cubic and fifth-order nonlinearity in the index of refraction. The results are presented and discussed.  相似文献   
999.
We report on the Langmuir-Blodgett film deposition and plasma etching of cadmium distearate on n-Gao.47Ino.53As to form a high-barrier-height Schottky barrier. Using this technique to form the gate electrode, we fabricated a 1?m-gate-length inverted InP-GalnAs modulation-doped field-effect transistor (MODFET) with an extrinsic transconductance of 170mS/mm and a cutoff frequencyfT of 19 GHz.  相似文献   
1000.
By using integral transform methods, an approach is developed to the solution of a problem on the temprature distribution in multilayer structures heated by cw scanning laser radiation, with phase transitions in the layers taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 6, pp. 1000–1010, December, 1987.  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