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   537175篇
  免费   7614篇
  国内免费   1821篇
电工技术   8726篇
综合类   2756篇
化学工业   81670篇
金属工艺   21094篇
机械仪表   16646篇
建筑科学   13554篇
矿业工程   2435篇
能源动力   12686篇
轻工业   51396篇
水利工程   5483篇
石油天然气   7158篇
武器工业   37篇
无线电   62715篇
一般工业技术   99693篇
冶金工业   88324篇
原子能技术   8906篇
自动化技术   63331篇
  2021年   3655篇
  2019年   3451篇
  2018年   19514篇
  2017年   18431篇
  2016年   15695篇
  2015年   4667篇
  2014年   7249篇
  2013年   20923篇
  2012年   14852篇
  2011年   25509篇
  2010年   20794篇
  2009年   19772篇
  2008年   21569篇
  2007年   22629篇
  2006年   14114篇
  2005年   13609篇
  2004年   13079篇
  2003年   12841篇
  2002年   11876篇
  2001年   11629篇
  2000年   10967篇
  1999年   11278篇
  1998年   26785篇
  1997年   18773篇
  1996年   14333篇
  1995年   10979篇
  1994年   9699篇
  1993年   9518篇
  1992年   7137篇
  1991年   6660篇
  1990年   6662篇
  1989年   6367篇
  1988年   6156篇
  1987年   5149篇
  1986年   5109篇
  1985年   6104篇
  1984年   5630篇
  1983年   5119篇
  1982年   4780篇
  1981年   4922篇
  1980年   4639篇
  1979年   4411篇
  1978年   4303篇
  1977年   4831篇
  1976年   6176篇
  1975年   3714篇
  1974年   3504篇
  1973年   3711篇
  1972年   2914篇
  1971年   2720篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
41.
The price of cobalt has increased by some 450% in the past two years, mainly due to increasing demand for lithium–ion batteries. With an official 2017 production of 64 kt, the Democratic Republic of Congo produces more than half of the world’s cobalt. African Copperbelt operations have traditionally focused on copper production; however, it has now become imperative to also consider cobalt recovery from these ores. A plethora of processing routes is possible. Most hydrometallurgical flowsheets recover cobalt from the raffinate of the low-grade copper solvent-extraction circuit. Downstream purification processes include sequential precipitation with a variety of reagents, solvent extraction, and ion exchange. Product choices include hydroxide, carbonate, sulfate, and metal cathode. This study assesses technical and economic advantages and limitations of various approaches to the hydrometallurgical processing of cobalt in an African context.  相似文献   
42.
The bromodomain and extra terminal (BET) family of bromodomain-containing proteins (BCPs) have been the subject of extensive research over the past decade, resulting in a plethora of high-quality chemical probes for their tandem bromodomains. In turn, these chemical probes have helped reveal the profound biological role of the BET bromodomains and their role in disease, ultimately leading to a number of molecules in active clinical development. However, the BET subfamily represents just 8/61 of the known human bromodomains, and attention has now expanded to the biological role of the remaining 53 non-BET bromodomains. Rapid growth of this research area has been accompanied by a greater understanding of the requirements for an effective bromodomain chemical probe and has led to a number of new non-BET bromodomain chemical probes being developed. Advances since December 2015 are discussed, highlighting the strengths/caveats of each molecule, and the value they add toward validating the non-BET bromodomains as tractable therapeutic targets.  相似文献   
43.
Theoretical Foundations of Chemical Engineering - The extraction of nitric and oxalic acids by neutral compounds TBP, DBBP, and TBPO have been studied. The optimal conditions of their separation...  相似文献   
44.
Journal of Communications Technology and Electronics - Abstract—The article presents a rigorous numerical solution, using the Wiener–Hopf method, to the problem of plane wave...  相似文献   
45.
Photonic Network Communications - Optical packet switching is a prominent technology proposing not only a reduction in the energy consumption by the elimination of numerous...  相似文献   
46.
47.
48.
49.
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.  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