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   1831752篇
  免费   54196篇
  国内免费   21931篇
电工技术   54438篇
技术理论   45篇
综合类   31143篇
化学工业   323514篇
金属工艺   83213篇
机械仪表   63411篇
建筑科学   72353篇
矿业工程   22786篇
能源动力   59198篇
轻工业   132677篇
水利工程   21681篇
石油天然气   58954篇
武器工业   2930篇
无线电   230971篇
一般工业技术   316505篇
冶金工业   185802篇
原子能技术   37330篇
自动化技术   210928篇
  2022年   17728篇
  2021年   28605篇
  2020年   21544篇
  2019年   22370篇
  2018年   24516篇
  2017年   25029篇
  2016年   30304篇
  2015年   30400篇
  2014年   45242篇
  2013年   107140篇
  2012年   56814篇
  2011年   71062篇
  2010年   63380篇
  2009年   70470篇
  2008年   63684篇
  2007年   59824篇
  2006年   63232篇
  2005年   55409篇
  2004年   51961篇
  2003年   50763篇
  2002年   49082篇
  2001年   45383篇
  2000年   43799篇
  1999年   43713篇
  1998年   53643篇
  1997年   45728篇
  1996年   41466篇
  1995年   35580篇
  1994年   32776篇
  1993年   31338篇
  1992年   27924篇
  1991年   24693篇
  1990年   24741篇
  1989年   23564篇
  1988年   21900篇
  1987年   19863篇
  1986年   19151篇
  1985年   22224篇
  1984年   22405篇
  1983年   20326篇
  1982年   19380篇
  1981年   19443篇
  1980年   18044篇
  1979年   18494篇
  1978年   17710篇
  1977年   17508篇
  1976年   18666篇
  1975年   15963篇
  1974年   15454篇
  1973年   15535篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
61.
Wireless Personal Communications - Despite its various benefits, the Mobile Ad-hoc Network (MANET) has a number of obstacles due to its mobility, unstable topology, energy efficiency, and other...  相似文献   
62.
Wireless Personal Communications - Besides anti-malware usage for the eradication of malicious attacks, researchers have developed epidemic models in order to gain more insights into the spread...  相似文献   
63.
Telecommunication Systems - Energy saving in User Equipment (UE) is one of the important issues for limited sources of power in the device. It is critical for the UE to maximize its energy...  相似文献   
64.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
65.
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically...  相似文献   
66.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is...  相似文献   
67.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  相似文献   
68.
Mobile Networks and Applications - Project MindCatcher is an art/research project which has the intention to explore the potential of interactive artistic environments for measuring and a better...  相似文献   
69.
Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface.  相似文献   
70.
In this investigation, low-cement castables were prepared using 70% alumina grog aggregates obtained from crushed alumina brick waste. The aggregates were thermally treated at 1550 °C for 3 h. Four types of low-cement castables were prepared with various types of aggregates (alumina grog with or without thermal treatment) and fillers (with or without zircon addition), and they were evaluated in terms of their physical, thermal, and chemical properties. Microstructural analysis via scanning electron microscopy (SEM) was performed on the castables before and after slag attack. Compared to the other fabricated castables, the thermally treated alumina grog castables with zircon showed better physical properties, such as a higher bulk density, cold crushing strength, and modulus of rupture and a lower apparent porosity and water absorption. In addition, they had a higher positive linear thermal expansion, refractoriness under load, permanent linear change, and hot modulus of rupture. The results of the SEM with energy dispersive X-ray analysis of the prepared castables confirmed that the mullite and anorthite phases were predominant when zircon was not added and the zircon–mullite phase additionally appeared upon the incorporation of zircon. A quantitative elemental analysis via X-ray fluorescence spectroscopy was employed to determine the composition of the castables. X-ray diffraction analysis showed that the alumina grog castables had a high mullite and low anorthite content, and the thermally treated alumina grog had a high anorthite, low mullite, and high zircon content. The improvement in the mechanical and thermo-mechanical properties of the castables with thermally treated alumina grog and added zircon can be attributed to the formation of the zircon–mullite phase with a low mullite phase content.  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