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   18236篇
  免费   2183篇
  国内免费   10篇
电工技术   1531篇
综合类   414篇
化学工业   8693篇
金属工艺   306篇
机械仪表   419篇
建筑科学   710篇
矿业工程   240篇
能源动力   118篇
轻工业   1791篇
水利工程   120篇
石油天然气   68篇
无线电   419篇
一般工业技术   3154篇
冶金工业   254篇
原子能技术   33篇
自动化技术   2159篇
  2023年   623篇
  2022年   322篇
  2021年   704篇
  2020年   668篇
  2019年   581篇
  2018年   567篇
  2017年   395篇
  2016年   621篇
  2015年   807篇
  2014年   853篇
  2013年   1469篇
  2012年   586篇
  2011年   463篇
  2010年   797篇
  2009年   962篇
  2008年   467篇
  2007年   430篇
  2006年   302篇
  2005年   312篇
  2004年   242篇
  2003年   236篇
  1998年   208篇
  1997年   153篇
  1996年   214篇
  1995年   207篇
  1994年   170篇
  1993年   238篇
  1992年   164篇
  1991年   138篇
  1990年   164篇
  1989年   186篇
  1988年   141篇
  1987年   174篇
  1986年   192篇
  1985年   182篇
  1984年   178篇
  1983年   181篇
  1982年   164篇
  1981年   218篇
  1980年   176篇
  1979年   181篇
  1977年   158篇
  1976年   167篇
  1975年   209篇
  1974年   205篇
  1973年   396篇
  1972年   218篇
  1971年   157篇
  1970年   146篇
  1968年   168篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Zusammenfassung Eine einfache Formel zur n?herungsweisen Berechnung der Axialspannungen eines Rohres infolge der von einer Temperaturschichtung im Rohrinnern hervorgerufenen Temperaturfelder wird vorgestellt. Die Formel basiert auf der konventionellen Balkentheorie. Durch Vergleiche der von der N?herungsformel gelieferten Axialspannungen mit den Axialspannungen, die mit Hilfe von Finite-Elemente-Rechnungen erhalten werden, wird gezeigt, da? die N?herungsformel die maximalen Axialspannungen ausreichend genau wiedergibt.  相似文献   
42.
Thermodynamic properties of aqueous solutions of both native and modified legumin of broad beans (Vicia faba L.) have been examined. A restricted trypsin-induced proteolysis was used to modify protein structure. Evaluation of protein affinity to ficoll in aqueous solutions showed that modified protein possessed higher hydrophilicity. Thermodynamic properties of diluted solutions were used to predict the phase behaviour in concentrated systems containing protein and ficoll. At specific concentrations of native legumin, the system can separate in two phases, whereas in the case of modified protein the single-phase behaviour of the system was predicted for any concentrations of both components. The experimental data obtained in concentrated systems confirmed predictions of thermodynamic analysis of diluted solutions.  相似文献   
43.
44.
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   
45.
The transition from basic automation to flexible manufacturing is an expensive and tedious procedure. It requires meticulous planning and almost clairvoyant forecasting to insure that the initial flexibility obtained is sufficient to allow growth and expansion in the future. This paper will suggest a systematic and methodological approach to achieve optimal flexibility and describe the present results of its application to an ongoing system transformation.

Conclusions based on existing levels of completion are presented along with identification of critical and non critical flexibility requirements. The considerations and steps taken are summarized in a procedural format which may then be applied to a wide variety of system transformations.  相似文献   

46.
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   
47.
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   
48.
Hydrogen free amorphous carbon coatings ‐ deposited with plasma‐activated high‐rate evaporation By using the technology of the plasmaactivated electron beam evaporation we deposited hydrogen free amorphous carbon coatings with deposition rates of up to 100 μm/h. The results of the mechanical and tribological investigations show the potential of these layers for the use in case of wear resistance. Hardnesses of up to 16GPa were proved. The actual state of the characterisation of the coatings is described and the outlook onto possibilities of further optimisation is given.  相似文献   
49.
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   
50.
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