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   41351篇
  免费   2233篇
  国内免费   22篇
电工技术   1639篇
综合类   419篇
化学工业   13312篇
金属工艺   612篇
机械仪表   876篇
建筑科学   2529篇
矿业工程   218篇
能源动力   866篇
轻工业   4092篇
水利工程   287篇
石油天然气   167篇
武器工业   1篇
无线电   2417篇
一般工业技术   6748篇
冶金工业   3382篇
原子能技术   264篇
自动化技术   5777篇
  2023年   962篇
  2022年   744篇
  2021年   1581篇
  2020年   1485篇
  2019年   1254篇
  2018年   1095篇
  2017年   894篇
  2016年   1295篇
  2015年   1346篇
  2014年   1563篇
  2013年   2798篇
  2012年   1702篇
  2011年   1883篇
  2010年   1747篇
  2009年   1936篇
  2008年   1469篇
  2007年   1345篇
  2006年   1120篇
  2005年   966篇
  2004年   818篇
  2003年   733篇
  2002年   624篇
  2001年   450篇
  2000年   437篇
  1999年   483篇
  1998年   969篇
  1997年   658篇
  1996年   630篇
  1995年   499篇
  1994年   450篇
  1993年   516篇
  1992年   355篇
  1991年   298篇
  1990年   308篇
  1989年   339篇
  1988年   273篇
  1987年   293篇
  1986年   311篇
  1985年   321篇
  1984年   317篇
  1983年   299篇
  1981年   315篇
  1980年   261篇
  1979年   269篇
  1977年   266篇
  1976年   291篇
  1975年   284篇
  1974年   260篇
  1973年   425篇
  1972年   263篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Our emphasis in this paper has been on the knowledge-based and cognitive issues pertinent for improved interactions between workers and manufacturing computer systems. We believe that these techniques are as necessary and applicable to manufacturing as to any other vocation, especially as the difference in collar color of shop people becomes less noticeable in their increasing role as knowledge workers.  相似文献   
32.
In this paper we present a general approach to the automatic content-based organization and visualization of large digital music collections. The general methodology consists in extracting musically and perceptually relevant patterns (‘features’) from the given audio recordings (e.g., mp3 files), using topology-preserving data projection methods to map the entire music collection onto two-dimensional visualization planes (possibly in a hierarchical fashion), and using a new display metaphor (the ‘Islands of Music’) to display the inherent structure of the music collection to the user. It is shown how arbitrary meta-data can be integrated into the visualization process, and how similarity according to different viewpoints can be defined and exploited. The basic methodology is briefly described, three prototype systems are presented, and a general discussion of the practical application possibilities of such technologies is offered.  相似文献   
33.
Many organisations suspect that their internal security threat is more pressing than their external security threat. The internal threat is predominantly the result of poor user security behaviour. Yet, despite that, security awareness programmes often seem more likely to put users to sleep than to improve their behaviour. This article discusses the influences that affect a user's security behaviour and outlines how a well structured approach focused on improving behaviour could be an excellent way to take security slack out of an organisation and to achieve a high return for a modest, low-risk investment.  相似文献   
34.
Helium leak test devices for the quality inspection of housings for vacuum compressors The well‐known and wide‐spread helium leak test method is a safe and fast quality testing method for construction units of any kind. Due to its safe examination and the short time of examination it is predominantly inserted into automated production lines as e.g. in the automobile supporting industry up to the examination by Airbags and rims of wheel. Likewise in addition, for the construction units, machines and devices of the vacuum engineering. From this the demand results simple and in particular economical devices for the helium leak test of construction units with small numbers of items of under 200 pieces per day. For these manufacturing profiles economical ways for the helium leak test are pointed out.  相似文献   
35.
36.
Failure analysis of hollow glasses The failure analysis is very important to clarify damages of hollow glasses. Damages of glass bottle through over pressure are very often linked with damages to persons. This is the reason why the causal research is from particular importance. Different surface characteristics of glass fragments as well as the fracture pattern give hints to the direction of the crack, the stress just before breakage and the reason of stress. A reconstruction of the bottle is a further helpful instrument for cause studies. The difference of the various characteristics of the surface will be explained. Further on there will be discussed different reasons and mechanism of fracture.  相似文献   
37.
Polycrystalline A1N thin films were deposited by RF reactive magnetron sputtering on Pt(111)/Ti electrode films. The substrates were tilted by an angle ranging from 40 degrees to 70 degrees with respect to the target normal. A low deposition temperature and a high sputter gas pressure were found ideal for tilted growth. The resulting grain tilt angle amounts to about half the substrate tilt angle. For coupling evaluation, 5 GHz solidly mounted resonator structures have been realized. The tilted grain A1N films exhibited a permittivity in the 9.5-10.5 range and loss tangent of 0.3%. Two shear modes as well as the longitudinal mode could be clearly identified. The coupling coefficient k2(eff) of the fundamental thickness shear mode (TS0) was found to be about 0.5%, which is compatible with a c-axis tilt of about 6 degrees.  相似文献   
38.
39.
Summary We introduce a very simple model for thermally activated atomic migration on a lattice, and several techniques to handle it. For thermodynamical systems, the model can be used for simulating decomposition paths taking into account relevant metallurgical features. Close to equilibrium, the simplest mean-field approximation of the model can be linearized with respect to the departure from equilibrium; one then gets a microscopic interpretation of classical phenomenological coefficients, such as mobility, interfacial transfer coefficient, rate constants for the coupled relaxation of concentration and order fields. Further away from the equilibrium, the nonlinearities can be taken into account in a consistent way. For driven alloys, i.e. alloys submitted to external forcing, forced atomic migration is added to the model and new features emerge: the model is supported by several experimental results some of which confirmed its predictions a posteriori.  相似文献   
40.
The use of small alternators, other than for standby purposes, is increasing and this has focused attention on the reliability and utility of the parameters normally quoted for such machines. Test procedures are described and methods used for parameter estimation discussed, with particular emphasis on the difficulties presented by small brushless machines  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