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   263122篇
  免费   3302篇
  国内免费   823篇
电工技术   5153篇
综合类   331篇
化学工业   37839篇
金属工艺   10279篇
机械仪表   8509篇
建筑科学   6253篇
矿业工程   1080篇
能源动力   6437篇
轻工业   23309篇
水利工程   2599篇
石油天然气   3918篇
武器工业   68篇
无线电   34831篇
一般工业技术   50416篇
冶金工业   47547篇
原子能技术   5425篇
自动化技术   23253篇
  2021年   2140篇
  2019年   2095篇
  2018年   3545篇
  2017年   3598篇
  2016年   3815篇
  2015年   2371篇
  2014年   4131篇
  2013年   11472篇
  2012年   6696篇
  2011年   9070篇
  2010年   7135篇
  2009年   8002篇
  2008年   8835篇
  2007年   8767篇
  2006年   7929篇
  2005年   7264篇
  2004年   6964篇
  2003年   6813篇
  2002年   6456篇
  2001年   6532篇
  2000年   6220篇
  1999年   6308篇
  1998年   14282篇
  1997年   10308篇
  1996年   8162篇
  1995年   6454篇
  1994年   5755篇
  1993年   5624篇
  1992年   4589篇
  1991年   4224篇
  1990年   4080篇
  1989年   3812篇
  1988年   3657篇
  1987年   3192篇
  1986年   3090篇
  1985年   3633篇
  1984年   3405篇
  1983年   3051篇
  1982年   2868篇
  1981年   2973篇
  1980年   2771篇
  1979年   2662篇
  1978年   2515篇
  1977年   2952篇
  1976年   3561篇
  1975年   2328篇
  1974年   2319篇
  1973年   2323篇
  1972年   1856篇
  1971年   1747篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
A new 3-D sidewall flash EPROM cell has been implemented in a novel memory array. The sidewall cell is a single-transistor stacked gate cell built on the sidewalls of a silicon pillar. The gates surround the pillar and current flows vertically from top to bottom of the pillar. The cell size approaches the square of the minimum pitch and is less than 40% of that of the conventional NOR-type structure. The cell and array architecture promise to be highly scalable  相似文献   
952.
Three coupling strategies in matching the Ritz-Galerkin method and the finite element method are introduced for general elliptic equations, and useful numerical techniques are provided. Numerical experiments have been carried out for solving the typical, singular Motz problem, which shows that optimal convergence rates of numerical solutions can be achieved by using the combined methods and techniques provided in this paper.  相似文献   
953.
954.
The involvement of mental health professionals in determinations of dangerousness is both common and controversial. Among the various contexts for these evaluations, the release of potentially violent forensic patients from maximum security facilities evokes justified concern from involved experts and apprehension to outrage from the immediate community. We sought to examine how conclusions are reached on dangerousness at two sequential stages: clinical recommendations and Manifest Dangerousness Hearings decisions. In an archival study of 245 patients, we found that lack of progress in the institution and physical assaultiveness were the strongest correlates with dangerousness. In contrast, experts and review boards appeared to be relatively less influenced by diagnosis, types of treatment, and sociodemographic variables.  相似文献   
955.
956.
957.
BACKGROUND: The precise sites and mechanisms of action of volatile anesthetics remain unknown. Recently, several integral membrane proteins have been suggested as potential targets to which anesthetics can bind at hydrophobic regions. Impairment of cell Ca2+ homeostasis has been postulated as one of the possible mechanisms of anesthetic action. To test these hypotheses, the authors selected the human erythrocyte Ca(2+)-ATPase as a model membrane protein. This enzyme is an integral membrane protein that is instrumental in maintaining Ca2+ homeostasis in the cell in which it is the sole Ca(2+)-transporting system. Thus, any functional alteration of the Ca(2+)-ATPase by anesthetics may lead to serious perturbations in Ca(2+)-regulated processes in the cell. METHODS: The Ca(2+)-ATPase activity was measured as a function of increased concentration of four volatile anesthetics: halothane, isoflurane, enflurane, and desflurane. RESULTS: All four anesthetics significantly inhibited the Ca(2+)-ATPase activity in a dose-dependent manner. The half-maximal inhibition occurred at anesthetic concentrations from 0.3 to 0.7 vol% at 37 degrees C, which, except for desflurane, is a clinically relevant concentration range. The greater the clinical potency of the volatile anesthetics studied, the less was the concentration required to inhibit the Ca(2+)-ATPase activity. The inhibition was less at 25 degrees C than at 37 degrees C, which is consistent with direct interactions of the nonpolar interfaces of the enzyme with the nonpolar of the portions of the anesthetics. CONCLUSIONS: The authors' findings indicate that the Ca(2+)-ATPase is a suitable model for investigating the mechanism of action of volatile anesthetics on the integral membrane protein, and that this inhibition may be specific.  相似文献   
958.
Numerical simulation based on the scalar beam propagation method, was used to investigate the performance of waveguide electrooptic beam deflectors. The deflectors under investigation consist of a stack of electrooptically controlled prisms in a waveguide. The results were compared to earlier simplified analysis. It was found that for given overall device dimensions, the number of interfaces between prisms in a prism-type electrooptic deflector has significant influence on the device performance when it is small. To avoid wavefront distortion, unwanted reflection from the interfaces, and asymmetry in the deflection angles caused by small number of interfaces, one should use more than about ten interfaces in a typical deflector. Additional insights of device operation and design issues are discussed  相似文献   
959.
960.
In this article we introduce an extension of Zadeh's compositional rule of inference in terms of the general rule of inference using a triangular norm extended to n arguments. Using this extension, all inferences schemes, crisp as well as fuzzy, based on the compositional rule of inference can be obtained in a uniform way. © 1993 John Wiley & Sons, Inc.  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