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   427728篇
  免费   1692篇
  国内免费   657篇
电工技术   7814篇
综合类   253篇
化学工业   62800篇
金属工艺   21119篇
机械仪表   14781篇
建筑科学   7923篇
矿业工程   4241篇
能源动力   8330篇
轻工业   23289篇
水利工程   5654篇
石油天然气   14528篇
武器工业   35篇
无线电   45482篇
一般工业技术   94937篇
冶金工业   74490篇
原子能技术   14123篇
自动化技术   30278篇
  2021年   3875篇
  2019年   3982篇
  2018年   7047篇
  2017年   7298篇
  2016年   7782篇
  2015年   4348篇
  2014年   7472篇
  2013年   17139篇
  2012年   11067篇
  2011年   14244篇
  2010年   11531篇
  2009年   13080篇
  2008年   13604篇
  2007年   13257篇
  2006年   11358篇
  2005年   10310篇
  2004年   10198篇
  2003年   9863篇
  2002年   9634篇
  2001年   9745篇
  2000年   9374篇
  1999年   9260篇
  1998年   22162篇
  1997年   15593篇
  1996年   11926篇
  1995年   9097篇
  1994年   8129篇
  1993年   8280篇
  1992年   6279篇
  1991年   6239篇
  1990年   6339篇
  1989年   6059篇
  1988年   5685篇
  1987年   5166篇
  1986年   5132篇
  1985年   5576篇
  1984年   5231篇
  1983年   4888篇
  1982年   4608篇
  1981年   4789篇
  1980年   4573篇
  1979年   4668篇
  1978年   4854篇
  1977年   5164篇
  1976年   6338篇
  1975年   4350篇
  1974年   4382篇
  1973年   4387篇
  1972年   3851篇
  1971年   3482篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
A new formula for solving the Krylov problem on the basis of band matrices is proposed. Properties of the obtained formula are studied for problems of analysis and synthesis of linear controlled systems.  相似文献   
994.
In catalytic cracking of vacuum gasoils, the yields of products are correlated with their hydrogen content. A correlation that allows predicting the yields of products of this process was elaborated based on the results of cracking of 11 gasoils of different origin and data on their density, refractive index, and 50% distillation temperature. However, it is not possible to predict the octane number of the naphtha obtained in cracking with the group hydrocarbon composition of the feedstock. __________ Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 31–34, July–August, 2007.  相似文献   
995.
996.
This paper discusses the results of a survey conducted by a team of researchers from Ashridge Business School that aimed to determine how managers and management practices have changed over the last 10 years. The survey considered a range of issues related to three broad themes, namely, organizational challenges, individual challenges, and the challenges of learning and development. The survey found that for the vast majority of managers in all industry sectors, the pressures of running an organization that is profitable, growing and competitive have not gone away. However, evidence suggests that these issues are perhaps slightly less dominant on the management agenda than in 1994. The survey concluded that there is a good deal that organizations might do to create a better working environment.  相似文献   
997.
The directivity characteristic of a normal probe with a circular piezoelectric plate has been calculated with allowance for pressure (elastic stress) oscillations within both the excitation region (the surface of the electrodes applied to the piezoelectric plate) and the plate itself, whose dimensions exceed those of the excitation region. It is established that, in the first and second cases, the directivity characteristics are somewhat wider and narrower, respectively, than those used in the conventional stepwise approximation of the pressure applied from a transmitting probe to the surface of a tested article. The effective piezoelectric-plate size is estimated.  相似文献   
998.
A chamber for X-ray diffractometry of gas-hydrate samples designed for operation at pressures of up to 700 atm and low temperatures is described. The leakproof character of the chamber at temperatures down to ?150°C is ensured by an Amaga-type seal with a fluoroplastic gasket pressed by disk springs. The chamber was used to study double hydrates using a synchrotron radiation source and a pressure generator based on a thermal multiplier.  相似文献   
999.
1000.
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