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   314074篇
  免费   2971篇
  国内免费   843篇
电工技术   5546篇
综合类   304篇
化学工业   49845篇
金属工艺   15024篇
机械仪表   10396篇
建筑科学   7291篇
矿业工程   2255篇
能源动力   6477篇
轻工业   25442篇
水利工程   3813篇
石油天然气   9285篇
武器工业   17篇
无线电   33892篇
一般工业技术   65671篇
冶金工业   50705篇
原子能技术   9131篇
自动化技术   22794篇
  2019年   2370篇
  2018年   4013篇
  2017年   4170篇
  2016年   4550篇
  2015年   2694篇
  2014年   4680篇
  2013年   12667篇
  2012年   7340篇
  2011年   9791篇
  2010年   7835篇
  2009年   8844篇
  2008年   9373篇
  2007年   9516篇
  2006年   8268篇
  2005年   7711篇
  2004年   7450篇
  2003年   7234篇
  2002年   7183篇
  2001年   7221篇
  2000年   6912篇
  1999年   6704篇
  1998年   13367篇
  1997年   10126篇
  1996年   8063篇
  1995年   6479篇
  1994年   5818篇
  1993年   5769篇
  1992年   4928篇
  1991年   4874篇
  1990年   4933篇
  1989年   4844篇
  1988年   4668篇
  1987年   4267篇
  1986年   4304篇
  1985年   4777篇
  1984年   4459篇
  1983年   4252篇
  1982年   3975篇
  1981年   4116篇
  1980年   3857篇
  1979年   4076篇
  1978年   4144篇
  1977年   4451篇
  1976年   5582篇
  1975年   3772篇
  1974年   3704篇
  1973年   3762篇
  1972年   3301篇
  1971年   2998篇
  1970年   2630篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
74.
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   
75.
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   
76.
The last dozen years have produced almost 50 English language articles on the synthesis of separation systems [1]. Most work has considered separating a single relatively ideal mixture into sharply split, usually pure-component products using systems of single-feed, two-product distillation columns. Of late, the work has considered heat-integrating these columns to reduce energy consumption. Present research will very likely produce valuable results for nonsharp separations.Earlier approaches developed both algorithmic- and heuristic-based tree search algorithms for discovering the better systems of non-heat-integrated columns. New results permit the design of heat-integrated systems.The paper highlights the above developments.  相似文献   
77.
Modifications of solid water and their transitions are described as they relate to cryo electron microscopy. In particular, the various amorphous states (amorphous polymorphs) as they exist below 100 K are extensively investigated. The “high-density” midification exhibits a lower viscosity than the “low-density” form. Differences are also observed in the mechanism of void formation due to electron irradiation: in the high-density form, voids are formed — not, however, in the low-density form. Together with the reaction to radiation damage, the physical properties of amorphous solid water are discussed with respect to embedding of organic specimens. Finally, the conditions and pitfalls associated with preparation of thin and entirely vitrified ice layers by shock-freezing are described.  相似文献   
78.
79.
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   
80.
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