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   96098篇
  免费   1786篇
  国内免费   510篇
电工技术   960篇
综合类   2375篇
化学工业   14695篇
金属工艺   5081篇
机械仪表   3462篇
建筑科学   2644篇
矿业工程   579篇
能源动力   2029篇
轻工业   4776篇
水利工程   1409篇
石油天然气   555篇
武器工业   4篇
无线电   10471篇
一般工业技术   18575篇
冶金工业   3087篇
原子能技术   340篇
自动化技术   27352篇
  2024年   70篇
  2023年   268篇
  2022年   587篇
  2021年   892篇
  2020年   753篇
  2019年   815篇
  2018年   15087篇
  2017年   13942篇
  2016年   10615篇
  2015年   1066篇
  2014年   964篇
  2013年   1543篇
  2012年   3969篇
  2011年   10237篇
  2010年   8834篇
  2009年   6090篇
  2008年   7143篇
  2007年   8077篇
  2006年   407篇
  2005年   1391篇
  2004年   1292篇
  2003年   1316篇
  2002年   650篇
  2001年   184篇
  2000年   263篇
  1999年   135篇
  1998年   186篇
  1997年   140篇
  1996年   139篇
  1995年   76篇
  1994年   62篇
  1993年   67篇
  1992年   57篇
  1991年   60篇
  1990年   40篇
  1989年   32篇
  1988年   34篇
  1986年   34篇
  1968年   45篇
  1967年   34篇
  1966年   42篇
  1965年   44篇
  1963年   28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
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
105.
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   
106.
The philosophy of group technology (GT) is an important concept in the design of flexible manufacturing systems and manufacturing cells. Group technology is a manufacturing philosophy that identifies similar parts and groups them into families. Beside assigning unique codes to these parts, group technology developers intend to take advantage of part similarities during design and manufacturing processes. GT is not the answer to all manufacturing problems, but it is a good management technique with which to standardize efforts and eliminate duplication. Group technology classifies parts by assigning them to different families based on their similarities in: (1) design attributes (physical shape and size), and/or (2) manufacturing attributes (processing sequence). The manufacturing industry today is process focused; departments and sub units are no longer independent but are interdependent. If the product development process is to be optimized, engineering and manufacturing cannot remain independent any more: they must be coordinated. Each sub-system is a critical component within an integrated manufacturing framework. The coding and classification system is the basis of CAPP and the functioning and reliability of CAPP depends on the robustness of the coding system. The proposed coding system is considered superior to the previously proposed coding systems, in that it has the capability to migrate into multiple manufacturing environments. This article presents the design of a coding and classification system and the supporting database for manufacturing processes based on both design and manufacturing attributes of parts. An interface with the spreadsheet will calculate the machine operation costs for various processes. This menu-driven interactive package is implemented using dBASE-IV. Part Family formation is achieved using a KAMCELL package developed in TURBO Pascal.  相似文献   
107.
For a structure formed from two thin-walled open members connected at 90°, torsion applied to one member can result in torsion as well as flexure in the second member, with the magnitude and direction of this torsion as well as flexure in the second member being determined by the type of joint used. Conventional structural analysis would normally assume the presence of only flexure in the second member. The results from a finite element study of structures formed from thin-walled channel sections connected by box, mitre and stiffened mitre joints is presented and an explanation for the behaviour of the different joint types is given. It is shown that for the box joint the warping deformation of the loaded member is the dominant factor in determining the magnitude and direction of the twisting of the second member, whilst this is determined for the stiffened mitre joint primarily by the St Venant rotation deformation of the loaded member. For the unstiffened joint it is shown that the warping and St Venant rotation deformation effects tend to cancel each other out.  相似文献   
108.
109.
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