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   521854篇
  免费   8902篇
  国内免费   1851篇
电工技术   8847篇
综合类   2674篇
化学工业   79026篇
金属工艺   22358篇
机械仪表   18963篇
建筑科学   11406篇
矿业工程   2711篇
能源动力   14484篇
轻工业   35064篇
水利工程   5582篇
石油天然气   8301篇
武器工业   19篇
无线电   64491篇
一般工业技术   106529篇
冶金工业   80458篇
原子能技术   9925篇
自动化技术   61769篇
  2022年   2943篇
  2021年   5298篇
  2020年   3971篇
  2019年   4933篇
  2018年   21156篇
  2017年   20107篇
  2016年   17750篇
  2015年   6081篇
  2014年   9301篇
  2013年   22930篇
  2012年   17204篇
  2011年   27302篇
  2010年   22155篇
  2009年   21348篇
  2008年   22626篇
  2007年   22730篇
  2006年   14218篇
  2005年   13601篇
  2004年   12755篇
  2003年   12681篇
  2002年   11403篇
  2001年   10727篇
  2000年   10082篇
  1999年   10336篇
  1998年   25661篇
  1997年   17545篇
  1996年   13499篇
  1995年   9964篇
  1994年   8748篇
  1993年   8697篇
  1992年   6284篇
  1991年   5924篇
  1990年   5876篇
  1989年   5520篇
  1988年   5218篇
  1987年   4553篇
  1986年   4397篇
  1985年   4900篇
  1984年   4493篇
  1983年   4041篇
  1982年   3683篇
  1981年   3753篇
  1980年   3452篇
  1979年   3352篇
  1978年   3352篇
  1977年   3776篇
  1976年   4899篇
  1975年   2863篇
  1974年   2676篇
  1973年   2742篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a...  相似文献   
2.
Koroteev  A. S. 《Atomic Energy》2021,130(4):202-208
Atomic Energy - The history and direction of further development of space nuclear energetics are examined. The functional diagram and principle of operation of a promising, powerful,...  相似文献   
3.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
4.
5.
6.
7.
Garzan oil field is located at the south east of Turkey. It is a mature oil field and the reservoir is fractured carbonate reservoir. After producing about 1% original oil in place (OOIP) reservoir pressure started to decline. Waterflooding was started in order to support reservoir pressure and also to enhance oil production in 1960. Waterflooding improved the oil recovery but after years of flooding water breakthrough at the production wells was observed. This increased the water/oil ratio at the production wells. In order to enhance oil recovery again different techniques were investigated. Chemical enhanced oil recovery (EOR) methods are gaining attention all over the world for oil recovery. Surfactant injection is an effective way for interfacial tension (IFT) reduction and wettability reversal. In this study, 31 different types of chemicals were studied to specify the effects on oil production. This paper presents solubility of surfactants in brine, IFT and contact angle measurements, imbibition tests, and lastly core flooding experiments. Most of the chemicals were incompatible with Garzan formation water, which has high divalent ion concentration. In this case, the usage of 2-propanol as co-surfactant yielded successful results for stability of the selected chemical solutions. The results of the wettability test indicated that both tested cationic and anionic surfactants altered the wettability of the carbonate rock from oil-wet to intermediate-wet. The maximum oil recovery by imbibition test was reached when core was exposed 1-ethly ionic liquid after imbibition in formation water. Also, after core flooding test, it is concluded that considerable amount of oil can be recovered from Garzan reservoir by waterflooding alone if adverse effects of natural fractures could be eliminated.  相似文献   
8.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...  相似文献   
9.
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   
10.
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   
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