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   29807篇
  免费   2243篇
  国内免费   1082篇
电工技术   1460篇
技术理论   2篇
综合类   1699篇
化学工业   5104篇
金属工艺   1832篇
机械仪表   1984篇
建筑科学   2326篇
矿业工程   987篇
能源动力   794篇
轻工业   1720篇
水利工程   524篇
石油天然气   2022篇
武器工业   213篇
无线电   3177篇
一般工业技术   3655篇
冶金工业   1570篇
原子能技术   354篇
自动化技术   3709篇
  2024年   93篇
  2023年   515篇
  2022年   796篇
  2021年   1221篇
  2020年   998篇
  2019年   750篇
  2018年   944篇
  2017年   945篇
  2016年   905篇
  2015年   1127篇
  2014年   1423篇
  2013年   1771篇
  2012年   1878篇
  2011年   1908篇
  2010年   1715篇
  2009年   1679篇
  2008年   1571篇
  2007年   1550篇
  2006年   1654篇
  2005年   1375篇
  2004年   883篇
  2003年   842篇
  2002年   747篇
  2001年   626篇
  2000年   672篇
  1999年   803篇
  1998年   687篇
  1997年   615篇
  1996年   550篇
  1995年   457篇
  1994年   349篇
  1993年   263篇
  1992年   196篇
  1991年   152篇
  1990年   113篇
  1989年   96篇
  1988年   78篇
  1987年   48篇
  1986年   49篇
  1985年   22篇
  1984年   18篇
  1983年   14篇
  1982年   16篇
  1981年   9篇
  1980年   7篇
  1979年   1篇
  1966年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
972.
The preparation and characterization of a new cyclometalated iridium complex with 2-(1-naphthalene) pyridine ligand were reported. An electrophosphorescent device was fabricated by using this new iridium complex as guest and poly-(cyano-paraphenylene) as host. Red electrophosphorescence was observed with an emission peak at approximately 600 nm. An external quantum efficiency of 1.3% was achieved in this electrophosphorescent polymer light-emitting devices.  相似文献   
973.
世界经济在经历争夺市场、争夺资源之后,人才成为各国、各企业争夺的焦点,人才资源以更快的速度呈现国际化趋势.实施有效的人本管理可以使企业吸引和留住人才.  相似文献   
974.
曹勇 《陕西电力》2004,32(5):56-58
10 kV真空断路器在我国已经大量地生产和使用.本文以ZW27-12为例,简要说明真空断路器的原理与维修.  相似文献   
975.
曹敏 《云南电力技术》2004,32(3):7-9,18
介绍了几种方法 ,用以消除或减小计量方式和谐波对电能量的计量方面带来的负面影响 ,使电能计量更加准确、公正和合理  相似文献   
976.
A study on roll gap profile (strip profile) control was accomplished in a 1700 mm single-stand temper mill. Some critical problems such as the deviation of work roll contour caused by grinding and wear, the effectiveness of work roll bending were discussed. Using a finite element model, the effects of roll contours (ground and wear) on strip profile were investigated. The roll bending effect on strip thickness was also analyzed. It is pointed out that there are some special features of flatness control in the temper mill: during temper rolling, roll deformation is slight due to small rolling load, and the loaded roll gap profile mainly depends on work roll contour, while the backup roll has a little effect on gap crown; the effect of bending force on gauge can not be ignored due to the coupling between flatness control and gauge control. A new roll contour arrangement adaptable to the mill was presented and has been put into practical production. The application of the new set of rolls showed some good results: larger crown control range of work roll bender, higher rolling stability, better strip profile and flatness quality.  相似文献   
977.
    
γ-alkoxy-propylamines, C12H25O(CH2)3NH2, C14H29O(CH2)3NH2, C16H33O(CH2)3NH2, C18H37O(CH2)3NH2 were synthesized from aliphatic alcohol and acrylonitrile. The flotation tests of kaolinite, pyrophyllite and illite were conducted. The flotation mechanisms were explained in view of the structures of reagents and aluminium silicate minerals, zeta potential and Fourier transform infrared spectrum measurements. The results show that the synthesized r-alkoxy-propylamines are more effective than dodecyl amine for flotation of kaolinite, pyrophyllite and illite. For flotation kaolinite and illite, the collecting ability is in the order of C18H37O(CH2)3NH2>C16H33O(CH2)3NH2> C14H29O(CH2)3NH2>C12H25O(CH2)3NH2, but the r-alkoxy-propylamines types of collectors have almost the same collecting ability on pyrophyllite, which demonstrating that γ-alkoxy-propylamines are new selective collectors for reverse floatation to remove aluminium silicate minerals from bauxite. Foundation item: Project (G1999064901) supported by the National Key Fundamental Research and Development Program of China; project (59925412) supported by the National Science Foundation for Distinguished Scholar  相似文献   
978.
串联式混合动力城市公交车车载数据采集系统开发   总被引:4,自引:1,他引:4  
根据串联式混合动力系统的特点 ,研制开发了串联式混合动力城市公交车车载数据采集系统。该系统能够对串联式混合动力城市公交车准确记录所需各种信息 ,且能根据采集的数据对串联式混合动力城市公交车进行性能评价  相似文献   
979.
The mechanisms responsible for the nucleation, growth and coarsening of Al2O3 particles in dilute Cu–Al alloys during internal oxidation have been investigated, and the alumina morphologies produced have been studied by electron microscopy using two-stage preshadowed carbon replica method. The alumina particle size has been observed to increase with increasing temperature of oxidation, with increasing time of oxidation, and with decreasing oxygen resource coefficient over the experimental range. These results indicate that the alumina particle size is determined by a competition between the rate of nucleation as the internal oxidation front passes and the subsequent growth and coarsening rates of the particles.  相似文献   
980.
Duetoincreasingcropyieldsandimprovingcropquality ,REammoniumhydrogencarbonatecomplexfertilizerwereappliedwidelyinsoils ,whichacceler atetheaccumulationofREinsoilsafteragriculturalapplication[1,2 ] .Previousstudieshavereportedaccu mulationofREsinsoilissignificantafter 3monthsofagriculturalapplication[3] ,andREhardlymigratedownward[4 ] .Itiscertaintythatagriculturalapplica tionofREcanresultREaccumulationinsoilandmayhaveaneffectonsoilmicrobialactivities .Soilmicro bialbiomassisamarkerofthemi…  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