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   3022篇
  免费   66篇
  国内免费   9篇
电工技术   38篇
综合类   3篇
化学工业   387篇
金属工艺   46篇
机械仪表   51篇
建筑科学   35篇
矿业工程   3篇
能源动力   94篇
轻工业   92篇
水利工程   6篇
石油天然气   16篇
无线电   332篇
一般工业技术   450篇
冶金工业   1300篇
原子能技术   20篇
自动化技术   224篇
  2023年   16篇
  2022年   31篇
  2021年   53篇
  2020年   43篇
  2019年   40篇
  2018年   66篇
  2017年   58篇
  2016年   51篇
  2015年   33篇
  2014年   69篇
  2013年   139篇
  2012年   93篇
  2011年   91篇
  2010年   63篇
  2009年   75篇
  2008年   71篇
  2007年   84篇
  2006年   64篇
  2005年   42篇
  2004年   46篇
  2003年   49篇
  2002年   51篇
  2001年   32篇
  2000年   31篇
  1999年   69篇
  1998年   355篇
  1997年   227篇
  1996年   174篇
  1995年   114篇
  1994年   95篇
  1993年   93篇
  1992年   39篇
  1991年   43篇
  1990年   41篇
  1989年   34篇
  1988年   52篇
  1987年   31篇
  1986年   31篇
  1985年   29篇
  1984年   16篇
  1983年   16篇
  1982年   16篇
  1981年   23篇
  1980年   15篇
  1979年   17篇
  1978年   19篇
  1977年   36篇
  1976年   81篇
  1975年   9篇
  1973年   11篇
排序方式: 共有3097条查询结果,搜索用时 15 毫秒
1.
The current work explores the usage of novel synthesized Deep Eutectic Solvent (DES) as a catalyst cum solvent media for the thermal dehydrogenation of chemical hydrides, namely Ammonia Borane (AB) and Ethylene diamine bisborane (EDAB). In the first instance, the quantum chemistry based COSMO-SAC (COnductor like Screening MOdel Segment Activity Coefficient) model was used for the selection of the pertinent solvent. 1-Butyl-3-methylimidazolium methanesulfonate: Imidazole ([BMIM][MeSO3]:[Im]) turned out to be an ideal eutectic mixture with the highest predicted solubility with amine boranes. The DES was synthesized by combining the Hydrogen Bond Acceptor (HBA), namely 1-Butyl-3-methylimidazolium methanesulfonate and Imidazole as Hydrogen Bond Donor (HBD) at a molar ratio of 1:2 and T = 70 °C. The formation of DES was confirmed by recording the NMR spectra. Further, the thermal dehydrogenation study was performed at a vacuum of 4 × 10?2 mbar (gauge pressure) of AB/DES and EDAB/DES systems at 105 °C, where a hydrogen equivalent of 1.40 and 2.55 was produced, respectively. The residual samples were further analyzed through 1H NMR analysis for the reaction mechanism and to confirm the role of Ionic Liquid-based DES as catalyst cum solvent media.  相似文献   
2.
Proficiency on underlying mechanism of rubber-metal adhesion has been increased significantly in the last few decades. Researchers have investigated the effect of various ingredients, such as hexamethoxymethyl melamine, resorcinol, cobalt stearate, and silica, on rubber-metal interface. The role of each ingredient on rubber-metal interfacial adhesion is still a subject of scrutiny. In this article, a typical belt skim compound of truck radial tire is selected and the effect of each adhesive ingredient on adhesion strength is explored. Out of these ingredients, the effect of cobalt stearate is found noteworthy. It has improved adhesion strength by 12% (without aging) and by 11% (humid-aged), respectively, over control compound. For detailed understanding of the effect of cobalt stearate on adhesion, scanning electron microscopy and energy dispersive spectroscopy are utilized to ascertain the rubber coverage and distribution of elements. X-ray photoelectron spectroscopy results helped us to understand the impact of CuXS layer depth on rubber-metal adhesion. The depth profile of the CuXS layer was found to be one of the dominant factors of rubber-metal adhesion retention. Thus, this study has made an attempt to find the impact of different adhesive ingredients on the formation of CuXS layer depth at rubber-metal interface and establish a correlation with adhesion strength simultaneously.  相似文献   
3.
4.
To determine whether there is any correlation between sudden decrease in barometric pressure and onset of labor, a non-experimental, retrospective study at a 948-bed tertiary care hospital was done. Pregnant patients of 36 weeks gestation or more who presented with spontaneous onset of labor during the 48 hours surrounding the 12 occurrences of significant drop in barometric pressure in 1992 were included in the study. Significantly more occurrences of onset of labor were identified in the 24 hours after a drop in barometric pressure than were identified in the 24 hours prior to the drop in barometric pressure (P < 0.05). Therefore, the overall number of labor onsets increased in the 24 hours following a significant drop in barometric pressure.  相似文献   
5.
6.
Vascular injuries may occur as complications of elbow dislocation and usually involve the brachial artery. A case report is presented in which only the radial artery was compromised as a result of the dislocation.  相似文献   
7.
8.
9.
10.
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