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   947篇
  免费   7篇
  国内免费   1篇
化学工业   20篇
金属工艺   2篇
机械仪表   4篇
能源动力   4篇
轻工业   13篇
水利工程   2篇
石油天然气   2篇
无线电   9篇
一般工业技术   38篇
冶金工业   839篇
原子能技术   3篇
自动化技术   19篇
  2024年   1篇
  2022年   2篇
  2021年   7篇
  2020年   4篇
  2019年   3篇
  2018年   1篇
  2017年   4篇
  2016年   8篇
  2015年   3篇
  2014年   11篇
  2013年   5篇
  2012年   7篇
  2011年   11篇
  2010年   5篇
  2009年   7篇
  2008年   7篇
  2007年   6篇
  2006年   3篇
  2005年   2篇
  2004年   3篇
  2003年   3篇
  2002年   2篇
  2001年   2篇
  1999年   22篇
  1998年   237篇
  1997年   146篇
  1996年   101篇
  1995年   49篇
  1994年   35篇
  1993年   45篇
  1992年   4篇
  1991年   10篇
  1990年   3篇
  1989年   10篇
  1988年   11篇
  1987年   5篇
  1986年   11篇
  1985年   14篇
  1983年   1篇
  1982年   10篇
  1981年   7篇
  1980年   8篇
  1979年   1篇
  1978年   3篇
  1977年   25篇
  1976年   89篇
  1955年   1篇
排序方式: 共有955条查询结果,搜索用时 15 毫秒
41.
42.
Increased vascular permeability of synovium induced by experimental haemarthrosis was studied in the stifle joint of the rat. Abnormal permeability was detected by injecting animals intravenously with colloidal carbon and examining the synovial vessels for intramural deposits of carbon. Both fresh and heparinized whole blood injected into the joint induced a marked permeability response of synovial venules which persisted for 18 hours. Platelets suspended in heparinized Tyrode solution induced a similar response, but one lasting only 12 hours. The permeability effects of suspensions of leucocytes and erythrocytes on the synovial vasculature were relatively mild and were maximal 5 and 12 h respectively after intra-articular injection. Heparinized platelet-free plasma had no significant permeability effects. These results indicate that platelets may play an important role in the pathogenesis of synovial inflammation in haemarthrosis.  相似文献   
43.
H Norström  S Berg  LP Andersson 《Vacuum》1977,27(3):99-101
The reliable pressure readings with a capacitance manometer are the basis for a new type of instrument designed for accurate and rapid measurements of capillary volumes. The basic measuring principle is based on expansion of air atmospheric pressure enclosed in a known volume into a pre-evacuated cylinder so that the enclosed volume will cause a reduced pressure in the cyllinder. The same is done with the air in an unknown volume into another identical pre-evacuated cylinder. A differential capacitance manometer is then used to measure the difference in pressure between the two cylinders with a high degree of accuracy. This difference in pressure is shown to be ainear function of the difference in volume between the unknown and the known volume. The accuracy and repeatability of the instrument is better than 0.5%.  相似文献   
44.
45.
46.
47.
Stock market automated investing is an area of strong interest for the academia, casual, and professional investors. In addition to conventional market methods, various sophisticated techniques have been employed to deal with such a problem, such as ARCH/GARCH predictors, artificial neural networks, fuzzy logic, etc. A computational system that combines a conventional market method (technical analysis), genetic programming, and multiobjective optimization is proposed in this work. This system was tested in six historical time series of representative assets from Brazil stock exchange market (BOVESPA). The proposed method led to profits considerably higher than the variation of the assets in the period. The financial return was positive even in situations in which the share lost market value.  相似文献   
48.
49.
50.
In this article, we make use of recently developed spectral nodal methods for anisotropically scattering media and we derive mathematical conditions for the diffuse reflection and transmission of radiation in the discrete ordinates formulation of particle transport theory for plane-parallel applications. The conditions arise from a suitable reformulation of spatially discretized equations defined on the boundary layers of a multislab domain. As a result, the boundary layers can be removed from the radiation transport calculations and replaced with exact and numerically stable equivalent conditions. In order to illustrate the applicability and computational merit of our discrete ordinates conditions for diffuse reflection and transmission in radiation transport calculations, we perform numerical experiments with atmospheric radiative transfer and nuclear reactor core models.  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