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   1096篇
  免费   23篇
电工技术   20篇
化学工业   238篇
金属工艺   28篇
机械仪表   22篇
建筑科学   48篇
矿业工程   23篇
能源动力   12篇
轻工业   108篇
水利工程   20篇
石油天然气   3篇
无线电   88篇
一般工业技术   194篇
冶金工业   159篇
原子能技术   9篇
自动化技术   147篇
  2022年   18篇
  2021年   20篇
  2020年   22篇
  2019年   16篇
  2018年   14篇
  2017年   15篇
  2016年   33篇
  2015年   19篇
  2014年   33篇
  2013年   51篇
  2012年   56篇
  2011年   59篇
  2010年   45篇
  2009年   45篇
  2008年   46篇
  2007年   45篇
  2006年   32篇
  2005年   28篇
  2004年   33篇
  2003年   22篇
  2002年   35篇
  2001年   14篇
  2000年   22篇
  1999年   24篇
  1998年   25篇
  1997年   25篇
  1996年   14篇
  1995年   15篇
  1994年   14篇
  1993年   12篇
  1992年   14篇
  1991年   16篇
  1990年   9篇
  1989年   8篇
  1988年   15篇
  1987年   20篇
  1985年   10篇
  1984年   11篇
  1983年   12篇
  1982年   8篇
  1981年   8篇
  1980年   10篇
  1979年   9篇
  1978年   7篇
  1977年   13篇
  1975年   10篇
  1974年   7篇
  1972年   9篇
  1971年   7篇
  1970年   7篇
排序方式: 共有1119条查询结果,搜索用时 0 毫秒
1.
2.
3.
An axisymmetrical model of a rapid nonisobaric heavily laden gas‐particle jet is developed. The model is based on the general functions for both axial and radial pressure distributions, which were discovered by a numerical study of rapid gas‐particle jets by the CFD code. The model equations were solved analytically. The results obtained by the model developed are in good agreement with those computed by the CFD code for a wide range of flow parameters.  相似文献   
4.
5.
MAN is but a part of the universe; his capabilities make him a significant link, in the cycle of life. To ensure this life, man must live in harmony with his environment. Recently, a disharmony has been discovered which could have grave effects upon the existence of man. It appears that man in his great thrust forward is destroying his own environment. The gravity of this threat to man's own existence carries some intrinsic problems of its own: man must allow his reason rather than his emotion to take command.  相似文献   
6.
Water vapor absorption at 161 wavelengths, from 9.2 to 11.9 micron, of the 12C1602, 13C1602, and 14CI602 lasers was measured using a resonant optoacoustic spectrometer. Results were obtained at several precisely determined vapor concentrations in a flow of pure air at a total pressure of 1 atm. Since the same apparatus and methodology were used for all measurements, a reliable assessment can be made of the relative merits of the three lasers in applications such as atmospheric propagation and ranging.  相似文献   
7.
8.
Increased amyloid beta (Aβ) levels and mitochondrial dysfunction (MD) in the human brain characterize Alzheimer disease (AD). Folic acid, magnesium and vitamin B6 are essential micro-nutrients that may provide neuroprotection. Bioenergetic parameters and amyloid precursor protein (APP) processing products were investigated in vitro in human neuroblastoma SH-SY5Y-APP695 cells, expressing neuronal APP, and in vivo, in the invertebrate Caenorhabditis elegans (CL2006 & GMC101) expressing muscular APP. Model organisms were incubated with either folic acid and magnesium-orotate (ID63) or folic acid, magnesium-orotate and vitamin B6 (ID64) in different concentrations. ID63 and ID64 reduced Aβ, soluble alpha APP (sAPPα), and lactate levels in SH-SY5Y-APP695 cells. The latter might be explained by enhanced expression of lactate dehydrogenase (LDHA). Micronutrient combinations had no effects on mitochondrial parameters in SH-SY5Y-APP695 cells. ID64 showed a significant life-prolonging effect in C. elegans CL2006. Incubation of GMC101 with ID63 significantly lowered Aβ aggregation. Both combinations significantly reduced paralysis and thus improved the phenotype in GMC101. Thus, the combinations of the tested biofactors are effective in pre-clinical models of AD by interfering with Aβ related pathways and glycolysis.  相似文献   
9.
10.
Resin flow into dry reinforcement regions is the main microstructural change during the processing of out-of-autoclave prepregs and influences air evacuation and void suppression. Such impregnation flow was investigated experimentally during the processing of a second-generation out-of-autoclave prepreg. First, laminates were partially processed to different stages of a simple cure cycle. Then, samples from each laminate were scanned using X-ray microtomography (micro-CT) to obtain 3D microstructural data. This data was used to investigate the initial microstructure of the material and measure the extent of impregnation at each processing stage, the rate of impregnation, and the evolution of macro-porosity within the material.  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