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   86722篇
  免费   11489篇
  国内免费   8391篇
电工技术   7715篇
技术理论   7篇
综合类   6787篇
化学工业   4280篇
金属工艺   1277篇
机械仪表   4897篇
建筑科学   3296篇
矿业工程   1194篇
能源动力   1758篇
轻工业   4805篇
水利工程   805篇
石油天然气   1299篇
武器工业   939篇
无线电   13823篇
一般工业技术   6156篇
冶金工业   1706篇
原子能技术   624篇
自动化技术   45234篇
  2024年   699篇
  2023年   2094篇
  2022年   2880篇
  2021年   3345篇
  2020年   3548篇
  2019年   3060篇
  2018年   2702篇
  2017年   3522篇
  2016年   3747篇
  2015年   3911篇
  2014年   6203篇
  2013年   6806篇
  2012年   5971篇
  2011年   6643篇
  2010年   4920篇
  2009年   5355篇
  2008年   5422篇
  2007年   5682篇
  2006年   4709篇
  2005年   4054篇
  2004年   3178篇
  2003年   2777篇
  2002年   2278篇
  2001年   1705篇
  2000年   1570篇
  1999年   1342篇
  1998年   1181篇
  1997年   983篇
  1996年   916篇
  1995年   748篇
  1994年   628篇
  1993年   594篇
  1992年   478篇
  1991年   445篇
  1990年   353篇
  1989年   253篇
  1988年   231篇
  1987年   188篇
  1986年   166篇
  1985年   204篇
  1984年   212篇
  1983年   188篇
  1982年   162篇
  1981年   115篇
  1980年   87篇
  1979年   92篇
  1978年   67篇
  1977年   70篇
  1976年   23篇
  1975年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Intelligent SQL     
Intelligent SQL is an intelligent database engine interface language which incorporates object-oriented, inferencing, and multi-media constructs. It is intended to be a powerful extension of existing SQL dialects. It also provides querying capabilities for object-oriented databases. Intelligent SQL was prototyped at Ashton-Tate. This paper discusses the main features of Intelligent SQL.  相似文献   
82.
A significant part of the theory of one-dimensional linear shift-invariant systems is based on the concept of weighting function (or impulse response): the output is the convolution of the weighting function with the input. This paper introduces the concept of linear translation-invariant systems and uses this notion in studying impulse response, z-transforms, and transfer functions for multidimensional systems.  相似文献   
83.
In this paper we generalize the Vidyasagar's well known theorem on the local stabilizability problem of nonlinear systems using state detection [11]. Our purpose is to prove that if a system is weakly detectable and stabilizable by means of a continuous state feedback u = γ(x), for which no differentiability assumption is imposed, then the system is also stabilized by the law u = γ(z), where z is the output of a weak detector for the state x. The result above is applicable to several cases not covered by other works.  相似文献   
84.
Parity space approach and H2 approach are two important fault detection approaches. This paper studies the relationship between these two approaches, which reveals frequency domain characteristics of the optimal solution of the parity space approach on the one side and provides a numerical solution of the H2-optimal design of residual generators on the other side.  相似文献   
85.
The author suggests a technological approach relevant to the optimization of toothpaste compositions with regard to the easy release of the therapeutic ingredients under shear deformation. It is based on the comparative assessment of the steady‐state viscous behaviour of placebo samples (mixtures containing all the components except the therapeutic ingredients) and the final products. It is presumed that the maximum beneficial effect of the toothpastes, as therapeutic agents, is achieved if the final products and the placebo blends display similar shear‐thinning characteristics.  相似文献   
86.
Evaluating the design of flexible manufacturing systems is complex. Developing a measure of performance useful for evaluating alternate designs continues to be interesting. Here, total productivity of the system is proposed as an appropriate measure. Specification of parameters based upon strategic considerations for this measure are discussed. Finally, the usefulness of the measure is demonstrated through an example.  相似文献   
87.
Predicates that preserve their values on a larger (extended) body of data are called equitone. An algebra of such predicates is constructed, a system of its generators is specified, and a complete system of transformations of identities is defined. The results obtained are used for construction and investigation of complete classes of compositions of various types and levels of abstractions that are used in logics of partial predicates.  相似文献   
88.
This paper reports the findings of a detailed study of Web-based systems design (WBSD) practices in Ireland based on data collected over a 3-year period (2002–2005), the objectives of which were to (1) contribute towards a richer understanding of the current “real-world” context of WBSD by characterising the profile of a typical project (team size, timeframe, nature of requirements, etc.) and identifying the key challenges, constraints, and imperatives (i.e. “mediating factors”) faced by Web-based system designers, and (2) understand how those contextual parameters and mediating factors influence the activity of WBSD as regards the selection and enactment of whatever design practices are therefore engaged (i.e. the use of methods, procedures, etc.). Data was gathered through a survey which yielded 165 usable responses, and later through a series of semi-structured qualitative interviews. Using grounded theory, an explanatory conceptual framework is derived, based on an extension of the “method-in-action” model, the application of which to WBSD has not been previously investigated in depth. It is proposed that this framework of WBSD issues is valuable in a number of ways to educators, researchers, practitioners, and method engineers.  相似文献   
89.
A new image analysis technique has been developed which allows maceral analysis of coal to be carried out. The technique is able to separate the liptinite component from the background resin by using two separate images of the surface captured with different camera exposure times. At normal exposure, the liptinite has a similar grey scale value to the surrounding resin, but at a higher exposure time, the resin remains black whilst the liptinite grey scale increases significantly enough to distinguish it from the resin. The method has been tested for repeatability and reproducibility and found to be within the ISO Standard requirements.  相似文献   
90.
Backlash is one of the most important non-linearities that limit the performance of speed and position control in industrial, robotics, automotive, automation and other applications. The control of systems with backlash has been the subject of study since the 1940s. This survey reveals that surprisingly few control innovations have been presented since the early path breaking papers that introduced the describing function analysis of systems with backlash. Promising developments are however taking place using adaptive and non-linear control strategies.  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