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   407611篇
  免费   4756篇
  国内免费   1223篇
电工技术   6671篇
综合类   305篇
化学工业   61913篇
金属工艺   17253篇
机械仪表   12625篇
建筑科学   9480篇
矿业工程   2404篇
能源动力   9560篇
轻工业   35698篇
水利工程   4729篇
石油天然气   10489篇
武器工业   17篇
无线电   46078篇
一般工业技术   81867篇
冶金工业   72015篇
原子能技术   10080篇
自动化技术   32406篇
  2021年   3240篇
  2019年   3148篇
  2018年   5378篇
  2017年   5528篇
  2016年   6072篇
  2015年   3732篇
  2014年   6415篇
  2013年   17688篇
  2012年   10644篇
  2011年   14507篇
  2010年   11433篇
  2009年   12800篇
  2008年   13310篇
  2007年   13238篇
  2006年   11927篇
  2005年   10848篇
  2004年   10436篇
  2003年   10231篇
  2002年   9699篇
  2001年   10106篇
  2000年   9324篇
  1999年   9656篇
  1998年   22419篇
  1997年   15840篇
  1996年   11936篇
  1995年   9156篇
  1994年   8047篇
  1993年   8039篇
  1992年   6088篇
  1991年   5906篇
  1990年   5809篇
  1989年   5544篇
  1988年   5443篇
  1987年   4677篇
  1986年   4646篇
  1985年   5338篇
  1984年   4901篇
  1983年   4590篇
  1982年   4245篇
  1981年   4492篇
  1980年   4183篇
  1979年   4243篇
  1978年   4237篇
  1977年   4533篇
  1976年   5735篇
  1975年   3775篇
  1974年   3737篇
  1973年   3850篇
  1972年   3256篇
  1971年   2919篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
112.
113.
114.
115.
116.
117.
We have designed, developed, and tested a very promising thermal image analysis method for polygraph testing. The method achieved a correct classification rate of CCR= 84% on the test population to our avail. This method, once refined, can serve as an additional channel for increasing the reliability and accuracy of traditional polygraph examination. We extract subtle facial temperature fluctuation patterns through nonlinear heat transfer modeling. The modeling transforms raw thermal data to blood flow rate information. Then, we use the slope of the average periorbital blood flow rate as the feature of a binary classification scheme. The results come to support our previous laboratory findings about the importance of periorbital blood flow in anxious states.  相似文献   
118.
We examine the symmetry-breaking transitions in equilibrium shapes of coherent precipitates in two-dimensional (2-D) systems under a plane-strain condition with the principal misfit strain components ε* xx and ε* yy . For systems with cubic elastic moduli, we first show all the shape transitions associated with different values of t=ε* yy /ε* xx . We also characterize each of these transitions, by studying its dependence on elastic anisotropy and inhomogeneity. For systems with dilatational misfit (t=1) and those with pure shear misfit (t=−1), the transition is from an equiaxed shape to an elongated shape, resulting in a break in rotational symmetry. For systems with nondilatational misfit (−1<t<1; t ≠ 0), the transition involves a break in mirror symmetries normal to the x- and y-axes. The transition is continuous in all cases, except when 0<t<1. For systems which allow an invariant line (−1≤t<0), the critical size increases with an increase in the particle stiffness. However, for systems which do not allow an invariant line (0<t≤1), the critical size first decreases, reaches a minimum, and then starts increasing with increasing particle stiffness; moreover, the transition is also forbidden when the particle stiffness is greater than a critical value.  相似文献   
119.
Phase transformations in particles of ultrafine powders of graphite, hexagonal boron nitride, and quartz during rapid heating and cooling by passage through a laser beam were investigated. A continuous infrared laser with a wavelength of 10.6 μm was used as a heat source through which the powders were recycled several times. Methods of concentrating the product phases are described. Particles of diamond, carbides, cubic boron nitride, koesite and stishovite were obtained in the mixed products.  相似文献   
120.
Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples.  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