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   83663篇
  免费   952篇
  国内免费   406篇
电工技术   773篇
综合类   2316篇
化学工业   11403篇
金属工艺   4784篇
机械仪表   3017篇
建筑科学   2159篇
矿业工程   562篇
能源动力   1108篇
轻工业   3591篇
水利工程   1268篇
石油天然气   343篇
无线电   9228篇
一般工业技术   16275篇
冶金工业   2627篇
原子能技术   253篇
自动化技术   25314篇
  2020年   7篇
  2019年   8篇
  2018年   14450篇
  2017年   13378篇
  2016年   9962篇
  2015年   601篇
  2014年   224篇
  2013年   194篇
  2012年   3135篇
  2011年   9399篇
  2010年   8277篇
  2009年   5548篇
  2008年   6770篇
  2007年   7777篇
  2006年   115篇
  2005年   1208篇
  2004年   1125篇
  2003年   1169篇
  2002年   536篇
  2001年   94篇
  2000年   175篇
  1999年   60篇
  1998年   51篇
  1997年   28篇
  1996年   45篇
  1995年   10篇
  1994年   11篇
  1993年   11篇
  1992年   11篇
  1991年   23篇
  1988年   9篇
  1969年   24篇
  1968年   43篇
  1967年   33篇
  1966年   42篇
  1965年   44篇
  1964年   11篇
  1963年   28篇
  1962年   22篇
  1961年   18篇
  1960年   30篇
  1959年   35篇
  1958年   37篇
  1957年   36篇
  1956年   34篇
  1955年   63篇
  1954年   68篇
  1952年   6篇
  1950年   6篇
  1949年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
In this paper, we argue that successful integration of knowledge across work domains in the short-term can mask the generation of long-term consequences. We explore a setting, the introduction of environmental considerations into semiconductor manufacturing, where the eventual adoption of common measurement artifacts and associated practices enabled knowledge integration, but failed to address significant underlying consequences. Drawing from observational, interview, and archival data we develop an understanding of the work practices of the Tech and EnviroTech groups as structured by the material world and broader collective conventions. We introduce the concept of knowledge regime to outline the differences in knowledge across these work domains. More specifically, we find that differences in the causal specificity and developmental time horizon of knowledge and the measurement artifacts that result contribute to the relative power of one knowledge regime over another. Understanding these sources of incompatibility provides insight into the design requirements of information systems as boundary objects for knowledge integration, but also specifies the potential limits to any design effort.  相似文献   
85.
86.
87.
88.
Understanding consumer behaviour is of vital importance to consumer-oriented e-business models today. In this paper, we study the relationships between consumer perceptions of risk and trust and the attitude towards purchasing at a consumer-to-consumer electronic marketplace (EM). Typical for EM settings is that consumer behaviour is subject to perceptions of the selling party as well as of the institutional structures of the intermediary that is operating the EM. Building upon the well-established literature of trust, we consider the concepts of intermediary trust and seller trust. We extend this categorisation by introducing the concepts of intermediary risk and seller risk. We developed measurement instruments for intermediary risk and seller risk. All measurement scales have acceptable alphas and are unidimensional. An empirical study is conducted to explore the relationships between the risk and trust types and consumer purchase attitude. The results reveal significant, direct effects of seller trust and seller risk. Second-order effects of intermediary trust and intermediary risk are investigated and reported. The paper concludes with general observations and recommendations for research and practice.  相似文献   
89.
90.
DC resistivity, dielectric constant, dielectric loss and positron annihilation spectra of (Ba1−x Ho x )TiO3 ceramics have been measured as a function of holmium concentration x. It has been found that the DC resistivity of (Ba1−x Ho x )TiO3 is strongly dependent on the Ho content: it decreases three orders of magnitude and reaches a minimum at x = 0.4%. Doping with 0.6% holmium increases the permittivity of BaTiO3 by approximately three times (from ∼1,300 to ∼4,000), with only a slight increase in the corresponding dielectric loss. The local electron density and defect concentration estimated using positron annihilation technique conforms well to the features found in the dielectric and resistivity measurements. The results have been discussed in terms of a mixed compensation model.  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