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   490172篇
  免费   6289篇
  国内免费   2358篇
电工技术   9657篇
技术理论   5篇
综合类   1372篇
化学工业   74905篇
金属工艺   24554篇
机械仪表   17571篇
建筑科学   11038篇
矿业工程   4039篇
能源动力   10303篇
轻工业   37182篇
水利工程   6116篇
石油天然气   12693篇
武器工业   262篇
无线电   51438篇
一般工业技术   101567篇
冶金工业   81126篇
原子能技术   11544篇
自动化技术   43447篇
  2021年   4211篇
  2019年   3814篇
  2018年   12853篇
  2017年   13187篇
  2016年   10723篇
  2015年   5099篇
  2014年   7804篇
  2013年   18942篇
  2012年   14385篇
  2011年   22480篇
  2010年   19085篇
  2009年   19187篇
  2008年   20082篇
  2007年   21561篇
  2006年   13192篇
  2005年   14256篇
  2004年   12092篇
  2003年   11381篇
  2002年   10463篇
  2001年   10163篇
  2000年   9553篇
  1999年   9476篇
  1998年   21932篇
  1997年   15837篇
  1996年   12151篇
  1995年   9187篇
  1994年   8251篇
  1993年   8338篇
  1992年   6462篇
  1991年   6238篇
  1990年   6220篇
  1989年   6123篇
  1988年   5831篇
  1987年   5074篇
  1986年   5147篇
  1985年   5760篇
  1984年   5524篇
  1983年   5162篇
  1982年   4623篇
  1981年   4740篇
  1980年   4547篇
  1979年   4727篇
  1978年   4663篇
  1977年   4881篇
  1976年   6111篇
  1975年   4208篇
  1974年   3929篇
  1973年   4094篇
  1972年   3560篇
  1971年   3172篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
The catalytic activity of a wide range of transition metal oxides in oxidation of sulphide ions by air in aqueous medium was studied. Some specific features of the reaction mechanism on some of the studied oxides were considered. The transition metal oxides are promising catalysts for practical application. Some of these oxides will allow the preparation of catalysts possessing activity comparable to that of the cobalt phthalocyanine based catalysts, popular in industrial practice.  相似文献   
995.
Business process redesign (BPR) has been widely touted as a means for leveraging the power of information technology to change business processes radically, resulting in substantial improvements in organizational effectiveness and efficiency. This study represents an early attempt at examining the strategic nature of the phenomenon. Because BPR is radical change and has the ability to alter both the competitive and operational nature of the corporation, it is critical that BPR be coordinated with corporate strategy. Through a survey of information system executives, the relationships between corporate competitive strategy and three types of BPR – intrafunctional, interfunctional and interorganizational – were examined. It was found that organizations following a cost strategy tended to do more BPR projects on interfunctional processes. Furthermore, the positive effect of a cost strategy on interfunctional BPR was found to be strengthened by the degree of integration of IS and business planning. It was also found that while interorganizational BPR was not related to a specific strategy, it was strongly related directly with IS–business planning integration.  相似文献   
996.
997.
998.
999.
1000.
Using a large database, this study examined 3 refinements of validity generalization procedures: (1) a more accurate procedure for correcting the residual standard deviation (SD) for range restriction to estimate SDp, (2) use of r? instead of study-observed rs in the formula for sampling error variance, and (3) removal of non-Pearson rs. The 1st procedure does not affect the amount of variance accounted for by artifacts. The addition of the 2nd and 3rd procedures increased the mean percentage of validity variance accounted for by artifacts from 70 to 82%, a 17% increase. The cumulative addition of all 3 procedures decreased the mean SDp estimate from .150 to .106, a 29% decrease. Six additional variance-producing artifacts were identified that could not be corrected for. In light of these it was concluded that the obtained estimates of mean SDp and mean validity variance accounted for were consistent with the hypothesis that the true mean SDp value is close to zero. These findings provide further evidence against the situational specificity hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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