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   469557篇
  免费   20117篇
  国内免费   1384篇
电工技术   8479篇
综合类   338篇
化学工业   81499篇
金属工艺   17253篇
机械仪表   14808篇
建筑科学   11011篇
矿业工程   2234篇
能源动力   12910篇
轻工业   40009篇
水利工程   4808篇
石油天然气   8058篇
武器工业   22篇
无线电   56958篇
一般工业技术   98855篇
冶金工业   82154篇
原子能技术   9311篇
自动化技术   42351篇
  2022年   2651篇
  2021年   4953篇
  2020年   5041篇
  2019年   7607篇
  2018年   10471篇
  2017年   10641篇
  2016年   11722篇
  2015年   8792篇
  2014年   11822篇
  2013年   27174篇
  2012年   15938篇
  2011年   19292篇
  2010年   15975篇
  2009年   17334篇
  2008年   17297篇
  2007年   16655篇
  2006年   14785篇
  2005年   13052篇
  2004年   12460篇
  2003年   12212篇
  2002年   11545篇
  2001年   11148篇
  2000年   10514篇
  1999年   10369篇
  1998年   26222篇
  1997年   18076篇
  1996年   13677篇
  1995年   10074篇
  1994年   8832篇
  1993年   8895篇
  1992年   6261篇
  1991年   5908篇
  1990年   5833篇
  1989年   5476篇
  1988年   5206篇
  1987年   4557篇
  1986年   4427篇
  1985年   4954篇
  1984年   4553篇
  1983年   4097篇
  1982年   3785篇
  1981年   3886篇
  1980年   3576篇
  1979年   3419篇
  1978年   3417篇
  1977年   4010篇
  1976年   5412篇
  1975年   2902篇
  1974年   2719篇
  1973年   2800篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
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   
3.
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   
4.
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   
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.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
10.
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in...  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