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   75560篇
  免费   14963篇
  国内免费   979篇
电工技术   2236篇
技术理论   4篇
综合类   1570篇
化学工业   22861篇
金属工艺   1960篇
机械仪表   2550篇
建筑科学   3425篇
矿业工程   772篇
能源动力   2148篇
轻工业   9227篇
水利工程   732篇
石油天然气   1074篇
武器工业   146篇
无线电   12530篇
一般工业技术   16285篇
冶金工业   3715篇
原子能技术   425篇
自动化技术   9842篇
  2024年   244篇
  2023年   504篇
  2022年   949篇
  2021年   1489篇
  2020年   2336篇
  2019年   3838篇
  2018年   3888篇
  2017年   4273篇
  2016年   4633篇
  2015年   4894篇
  2014年   5180篇
  2013年   6990篇
  2012年   4691篇
  2011年   4762篇
  2010年   4538篇
  2009年   4489篇
  2008年   4053篇
  2007年   3705篇
  2006年   3262篇
  2005年   2673篇
  2004年   2476篇
  2003年   2536篇
  2002年   2670篇
  2001年   2305篇
  2000年   1869篇
  1999年   1179篇
  1998年   1193篇
  1997年   852篇
  1996年   703篇
  1995年   562篇
  1994年   486篇
  1993年   421篇
  1992年   308篇
  1991年   265篇
  1990年   268篇
  1989年   235篇
  1988年   206篇
  1987年   177篇
  1986年   150篇
  1985年   143篇
  1984年   127篇
  1983年   87篇
  1982年   87篇
  1981年   64篇
  1980年   93篇
  1979年   67篇
  1978年   73篇
  1977年   70篇
  1976年   85篇
  1975年   52篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
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   
103.
104.
105.
106.
107.
Imperfection in information can be considered a crosscutting concern that manifests itself in diverse kinds of imprecision, uncertainty, or inconsistency in the data models of a software system. The extension of existing programming and querying interfaces for the different aspects of information imperfection requires a proper modularization of the different concerns of numerical imprecision handling, so that the extensions do not interfere with existing programming practices and do not obscure the original design. Aspect‐oriented design (AOD) enables such a form of nonintrusive extensions to be added to existing software libraries, clearly separating fuzziness or other imperfections in data as a differentiated concern that can be considered from the early phases of development. In this article, a general framework for aspect‐based extension of data models and fuzzy databases is described, and some design and implementation issues of such AOD‐based extensions on OJB database libraries are described as a case study. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 1199–1216, 2006.  相似文献   
108.
The objective of this study is to determine the chemical kinetics of desulphurization of Thai limestone in an atmospheric fluidized bed combustor (AFBC). The experiments, which employed the batch technique using the limestone samples from six major sources in Thailand, were performed in a laboratory‐scale AFBC. The results obtained were analysed and correlated in the form of apparent reaction rate and deactivation rate constants as a function of operating conditions of the furnace and their properties, respectively. The formulae derived from these correlations were kept as general as possible in order that they could be used as input parameters for the selected mathematical model of desulphurization in an AFBC that is suitable for practical use. The predicted results were in good agreement with the experimental data reported in the literature. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
109.
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   
110.
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