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   311552篇
  免费   4151篇
  国内免费   938篇
电工技术   5455篇
综合类   392篇
化学工业   49533篇
金属工艺   12557篇
机械仪表   9149篇
建筑科学   7516篇
矿业工程   1955篇
能源动力   7123篇
轻工业   28946篇
水利工程   3365篇
石油天然气   7208篇
武器工业   26篇
无线电   32790篇
一般工业技术   61132篇
冶金工业   57335篇
原子能技术   7676篇
自动化技术   24483篇
  2021年   2624篇
  2019年   2315篇
  2018年   4369篇
  2017年   4240篇
  2016年   4599篇
  2015年   3120篇
  2014年   4984篇
  2013年   13354篇
  2012年   7886篇
  2011年   10320篇
  2010年   8504篇
  2009年   9544篇
  2008年   9945篇
  2007年   9770篇
  2006年   8537篇
  2005年   7876篇
  2004年   7224篇
  2003年   6937篇
  2002年   6978篇
  2001年   6797篇
  2000年   6450篇
  1999年   6619篇
  1998年   16513篇
  1997年   12133篇
  1996年   9335篇
  1995年   7015篇
  1994年   6321篇
  1993年   6172篇
  1992年   4642篇
  1991年   4584篇
  1990年   4414篇
  1989年   4442篇
  1988年   4382篇
  1987年   3736篇
  1986年   3733篇
  1985年   4359篇
  1984年   4145篇
  1983年   3761篇
  1982年   3543篇
  1981年   3712篇
  1980年   3579篇
  1979年   3485篇
  1978年   3556篇
  1977年   4142篇
  1976年   5437篇
  1975年   3246篇
  1974年   3090篇
  1973年   3122篇
  1972年   2704篇
  1971年   2518篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
With the creation of balancing authorities by the North American Reliability Council that span large portions of the North American interconnection, and stringent requirements for real time monitoring of power system evolution, faster and more accurate state estimation algorithms that can efficiently handle systems of very large sizes are needed in the present environment. This paper presents a distributed state estimation algorithm suitable for large-scale power systems. Synchronized phasor measurements are applied to aggregate the voltage phase angles of each decomposed subsystem in the distributed state estimation solution. The aggregated state estimation solution is obtained from the distributed solution using a sensitivity analysis based update at chosen boundary buses. Placement of synchronized phasor measurements in the decomposed subsystems is also investigated in this paper. Test results on the IEEE 118-bus test bed are provided  相似文献   
83.
84.
Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry  相似文献   
85.
The latest developments and in particular important synthetic aspects for the preparation of modern poly(styrene‐divinylbenzene) (PS‐DVB) based liquid chromatography (LC) supports are reviewed. In this context, the chemistry of particular porous and nonporous, functionalized, monolithic, coated silica and more specialized mixed organic PS‐DVB media is covered. Special consideration is given to modern approaches such as micro‐(μ)‐HPLC and coating techniques and their most important applications. Synthetic particularities relevant to the corresponding applications are outlined.  相似文献   
86.
87.
The purpose of this paper is to provide an analysis of the alternative modelling systems for office information systems. More specifically, we are interested in identifying the current research trends of merging office modelling ideas together with concepts that owe their origin to the object-oriented paradigm and to artificial intelligence. In this respect an office model is defined as encompassing three domains: passive office objects; dynamically defined and manipulated office procedures; and goal-directed office tasks. Following this definition we exploit the potential of using the object-oriented and knowledge representation techniques for modelling each of the three domains using evidence from real-world applications.  相似文献   
88.
89.
90.
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