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   21722篇
  免费   1184篇
  国内免费   17篇
电工技术   359篇
综合类   55篇
化学工业   4745篇
金属工艺   619篇
机械仪表   523篇
建筑科学   946篇
矿业工程   131篇
能源动力   462篇
轻工业   2881篇
水利工程   161篇
石油天然气   53篇
无线电   1294篇
一般工业技术   5353篇
冶金工业   1758篇
原子能技术   198篇
自动化技术   3385篇
  2023年   264篇
  2022年   236篇
  2021年   501篇
  2020年   406篇
  2019年   378篇
  2018年   714篇
  2017年   731篇
  2016年   804篇
  2015年   646篇
  2014年   915篇
  2013年   1636篇
  2012年   1016篇
  2011年   1225篇
  2010年   1062篇
  2009年   952篇
  2008年   1052篇
  2007年   1045篇
  2006年   750篇
  2005年   618篇
  2004年   524篇
  2003年   506篇
  2002年   503篇
  2001年   411篇
  2000年   366篇
  1999年   296篇
  1998年   617篇
  1997年   424篇
  1996年   346篇
  1995年   279篇
  1994年   213篇
  1993年   202篇
  1992年   147篇
  1991年   125篇
  1990年   112篇
  1989年   98篇
  1988年   106篇
  1987年   85篇
  1986年   74篇
  1985年   178篇
  1984年   180篇
  1983年   115篇
  1982年   122篇
  1981年   150篇
  1980年   118篇
  1979年   94篇
  1978年   95篇
  1977年   106篇
  1976年   151篇
  1975年   89篇
  1974年   75篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Service life planning comprises a model for the determination of a reasonable expected service life for buildings and components, and it establishes a routine for the assessment of design alternatives. A design option is considered reasonable when it meets or exceeds performance requirements over time that have been drawn up specifically for the specific project. Due to this assessment reference, there is a very evident link to the concept of performance-based building. Any stakeholder involved in the value chain or in the design process of the building, as well as regulators and building users, can express performance requirements. Identified requirements, both in relevance and in quality, will vary with the stakeholder and his/her perspective of interest. As building sector manufacturers develop most products with reference to standards rather than with reference to specific requirements, there is no direct link from user requirements to the product design. Instead, the building designer has the responsibility to ensure performance requirements are met by the performance of products integrated into the design. As these design decisions also have to be made at the material and component level, a performance-based building would benefit from an established rationale that enables the communication of performance requirements across the relevant system levels in the relevant design processes. A path for the connection of the established concepts of service life planning and performance-based building is presented. The aim is to identify key elements that need to be developed for the successful linkage of performance-based building with service life planning.  相似文献   
24.
25.
An experimental investigation of heat transfer and pressure drop from a new type of corrugated channels is presented. The investigation has been carried out for Reynolds numbers in the range of 800 < Re < 5000 for one corrugated and one smooth channel. It is found that the heat transfer from the corrugated channel is up to 3.5 times higher than for the smooth one. The pressure drop is however large (5 – 6 times the value of a smooth channel) and it is suggested that the corrugation height and length should be altered in order to balance the increases in heat transfer and pressure drop.  相似文献   
26.
27.
28.
29.
The meat quality of M. longissimus muscle was evaluated in 851 pigs by using the Fibre Optic Probe (FOP) at three sites in the muscle and in both halves of the carcass. A systematic difference between sites was found, with the lowest light scattering (indicating the best meat quality) in the mid-part of the muscle and higher light scattering in the anterior and posterior parts. A non-systematic variation was also observed, with the opposite pattern in some animals, even though it was not frequent. A negative influence of the shackling was found, yielding higher FOP values in the shackled half.

Drip loss measurements in the Longissimus muscle, taken from another 100 pig carcasses, were evaluated using three methods. Drip loss, too, showed a considerable variation along the Longissimus muscle, with minimum losses around the last rib. Repeatability estimates, calculated from two non-consecutive pieces of the Longissimus dorsi muscle from each carcass, varied from 0·4 when keeping samples vacuum packed for 2 days, to 0·5 when the samples were either kept in plain plastic bags for 2 days or in a meat container with a squared inset for 1 or 2 days.  相似文献   

30.
Metallurgical and Materials Transactions A - Co-based superalloys have been developed as candidate materials to replace Ni-based superalloys in hot sections of turbine engines, however, their...  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