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   52095篇
  免费   3052篇
  国内免费   155篇
电工技术   750篇
综合类   72篇
化学工业   11196篇
金属工艺   2243篇
机械仪表   3476篇
建筑科学   1141篇
矿业工程   25篇
能源动力   2284篇
轻工业   4143篇
水利工程   276篇
石油天然气   88篇
武器工业   2篇
无线电   8258篇
一般工业技术   11333篇
冶金工业   4008篇
原子能技术   706篇
自动化技术   5301篇
  2024年   24篇
  2023年   558篇
  2022年   690篇
  2021年   1547篇
  2020年   1135篇
  2019年   1268篇
  2018年   1546篇
  2017年   1518篇
  2016年   1889篇
  2015年   1425篇
  2014年   2261篇
  2013年   3237篇
  2012年   3481篇
  2011年   4158篇
  2010年   3002篇
  2009年   3109篇
  2008年   2967篇
  2007年   2321篇
  2006年   2148篇
  2005年   1811篇
  2004年   1658篇
  2003年   1603篇
  2002年   1417篇
  2001年   1211篇
  2000年   1079篇
  1999年   1005篇
  1998年   1617篇
  1997年   1014篇
  1996年   832篇
  1995年   579篇
  1994年   479篇
  1993年   421篇
  1992年   307篇
  1991年   284篇
  1990年   266篇
  1989年   254篇
  1988年   213篇
  1987年   173篇
  1986年   125篇
  1985年   117篇
  1984年   95篇
  1983年   66篇
  1982年   38篇
  1981年   41篇
  1980年   32篇
  1979年   31篇
  1978年   30篇
  1977年   40篇
  1976年   64篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
Machine Learning - We consider the problem of learning a binary classifier from only positive and unlabeled observations (called PU learning). Recent studies in PU learning have shown superior...  相似文献   
35.
Microsystem Technologies - A color-laser printing system consisting of a tandem laser scanning unit uses four laser diodes and a single polygonal mirror (PM) to expose light onto four...  相似文献   
36.
37.
38.
39.
While exercise training (ET) is an efficient strategy to manage obesity, it is recommended with a dietary plan to maximize the antiobesity functions owing to a compensational increase in energy intake. Capsiate is a notable bioactive compound for managing obesity owing to its capacity to increase energy expenditure. We aimed to examine whether the antiobesity effects of ET can be further enhanced by capsiate intake (CI) and determine its effects on resting energy expenditure and metabolic molecules. Mice were randomly divided into four groups (n = 8 per group) and fed high-fat diet. Mild-intensity treadmill ET was conducted five times/week; capsiate (10 mg/kg) was orally administered daily. After 8 weeks, resting metabolic rate and metabolic molecules were analyzed. ET with CI additively reduced the abdominal fat rate by 18% and solely upregulated beta-3-adrenoceptors in adipose tissue (p = 0.013) but did not affect the metabolic molecules in skeletal muscles. Surprisingly, CI without ET significantly increased the abdominal fat rate (p = 0.001) and reduced energy expenditure by 9%. Therefore, capsiate could be a candidate compound for maximizing the antiobesity effects of ET by upregulating beta-3-adrenoceptors in adipose tissue, but CI without ET may not be beneficial in managing obesity.  相似文献   
40.
With superior properties of Mg such as high hydrogen storage capacity (7.6 wt% H/MgH2), low price, and low density, Mg has been widely studied as a promising candidate for solid-state hydrogen storage systems. However, a harsh activation procedure, slow hydrogenation/dehydrogenation process, and a high temperature for dehydrogenation prevent the use of Mg-based metal hydrides for practical applications. For these reasons, Mg-based alloys for hydrogen storage systems are generally alloyed with other elements to improve hydrogen sorption properties. In this article, we have added Na to cast Mg–La alloys and achieved a significant improvement in hydrogen absorption kinetics during the first activation cycle. The role of Na in Mg–La has been discussed based on the findings from microstructural observations, crystallography, and first principles calculations based on density functional theory. From our results in this study, we have found that the Na doped surface of Mg–La alloy systems have a lower adsorption energy for H2 compared to Na-free surfaces which facilitates adsorption and dissociation of hydrogen molecules leading to improvement of absorption kinetic. The effect of Na on the microstructure of these alloys, such as eutectic refinement and a density of twins is not highly correlated with absorption kinetics.  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