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   469982篇
  免费   4633篇
  国内免费   1042篇
电工技术   8403篇
综合类   415篇
化学工业   71318篇
金属工艺   23226篇
机械仪表   16635篇
建筑科学   9766篇
矿业工程   4446篇
能源动力   9688篇
轻工业   30903篇
水利工程   6138篇
石油天然气   14912篇
武器工业   91篇
无线电   50573篇
一般工业技术   103627篇
冶金工业   73432篇
原子能技术   14673篇
自动化技术   37411篇
  2021年   4199篇
  2019年   4170篇
  2018年   7789篇
  2017年   8072篇
  2016年   8526篇
  2015年   4817篇
  2014年   8337篇
  2013年   19638篇
  2012年   12514篇
  2011年   16300篇
  2010年   13057篇
  2009年   14602篇
  2008年   15449篇
  2007年   15171篇
  2006年   13044篇
  2005年   11757篇
  2004年   11411篇
  2003年   11202篇
  2002年   10719篇
  2001年   10621篇
  2000年   10339篇
  1999年   9853篇
  1998年   20248篇
  1997年   15233篇
  1996年   11924篇
  1995年   9545篇
  1994年   8665篇
  1993年   8718篇
  1992年   7274篇
  1991年   7077篇
  1990年   7036篇
  1989年   6714篇
  1988年   6444篇
  1987年   6027篇
  1986年   5878篇
  1985年   6485篇
  1984年   6218篇
  1983年   5753篇
  1982年   5453篇
  1981年   5566篇
  1980年   5403篇
  1979年   5485篇
  1978年   5542篇
  1977年   5910篇
  1976年   6958篇
  1975年   5105篇
  1974年   5146篇
  1973年   5228篇
  1972年   4467篇
  1971年   4108篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
The evolution of investigations into glass properties is described with the use of the SciGlass information system on the basis of an analysis of the world literature on glass from the end of the 19th century to the present day. Variations in the total amount of published data, in the interest of researchers in certain glass components and their properties, in the specific features of forming research groups, and in the general quality of publications are considered. Measures are proposed that can prevent a further decline in the quality of published experimental results.  相似文献   
993.
As the wave of globalization washes over geographical boundaries, the world steps into the era of a new knowledge-based economy with governments striving to encourage innovation in industry especially through national systems of innovation. A national system of innovation (NSI) is considered important because how a nation utilizes and exploits its NSI will determine whether it can compete and ride the wave of globalization or be carried by it and thrashed onto the shores of the new economy. This paper seeks to highlight the linkages developed for enabling communication among the various NSI stakeholders for achieving goals in one such effort, viz. the Multimedia Super Corridor (MSC) Cluster of Malaysia. The MSC offers a vision to create a global multimedia climate through an integrated environment of interlinked elements and attributes. The government of Malaysia, realising the significance of the NSI as a way to better utilize, exploit, and enhance systems, is making efforts to this effect. The efforts include bringing together various stakeholder organizations under the "Multimedia Flagship Applications" to develop flagship applications. This is for the development of information technology applications to pave the way toward a knowledge-based economy. The MSC Cluster is presented here as a physical manifestation of the NSI, and it gives an idea as to how policy makers can design linkages for communication among the various stakeholders to further national innovative performance and competitiveness in general.  相似文献   
994.
To improve a company's 'chopping' power it is necessary to apply systems engineering principles to 'project systems' and take the time to plan effectively, to reflect upon what it is that is being done and thereby improve the way things are done. This article takes a systems view of the project and applies systems engineering principles to project management. Projects (complex systems) are needed to create deliverables (which are also complex systems) and investing in the former will be more than paid back in the latter. It is our aim here to clear up some misunderstandings about systems engineering and its role within a complex project and to highlight the need for businesses to take time to improve their processes in the context of good systems engineering practice.  相似文献   
995.
Strain endurance experiments on a filled elastomer were performed at several temperatures. It was found that superimposed prestraining accelerated the ageing process. This process was caused by microstructural changes in the elastomer. In order to evaluate the mechanical properties of a filled elastomer it is necessary to take into consideration not only the ageing effects but also the loading history.  相似文献   
996.
997.
Problems associated with different calibration techniques and some instrumental effects that can determine instrumental accuracy are discussed. It is shown how transmission effects can be observed and used to generate a correction curve for refracted near-field instruments. High-quality fiber slices needed for axial interferometry were used to obtain refractive index differences on suitable fibers to ±1% with the measurements traceable to national standards. Interferometry was used to calibrate a multiple-step fiber which is available in 10-m lengths with a certificate of calibration. The limitations of the technique are discussed, and preliminary results of a study on the effects of residual stress and stress relief on measurements are given. Comparisons are made between measurements made by axial interferometry and refracted near field on a range of fibers. It is shown that commercial profilers can produce reliable measurements of refractive index difference, absolute refractive index, profile shape, and numerical aperture that agree well with measurements by other techniques  相似文献   
998.
Discrete‐time model reference adaptive control (MRAC) is considered with both least squares and projection algorithm parameter identification. For both cases complete Lyapunov proofs are given for stability and convergence. The results extend the approach of Johansson (Int. J. Control 1989; 50 (3):859–869) to include Lyapunov stability for MRAC when the normalized projection algorithm is used for parameter identification. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
999.
1000.
Recently, a direct method for outer solution of linear parametric systems has been suggested for the general case where the elements of the system are nonlinear functions of independent interval parameters. In this paper, an improvement of the method is introduced which may lead to a narrower outer solution.  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