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   618928篇
  免费   9229篇
  国内免费   2512篇
电工技术   11128篇
综合类   799篇
化学工业   89439篇
金属工艺   25055篇
机械仪表   20050篇
建筑科学   13596篇
矿业工程   3341篇
能源动力   17576篇
轻工业   46060篇
水利工程   6564篇
石油天然气   12145篇
武器工业   56篇
无线电   75514篇
一般工业技术   125863篇
冶金工业   116266篇
原子能技术   14520篇
自动化技术   52697篇
  2021年   5661篇
  2020年   4328篇
  2019年   5522篇
  2018年   9220篇
  2017年   9314篇
  2016年   9959篇
  2015年   6468篇
  2014年   10692篇
  2013年   29528篇
  2012年   17130篇
  2011年   23043篇
  2010年   18323篇
  2009年   20908篇
  2008年   21314篇
  2007年   20972篇
  2006年   18443篇
  2005年   16706篇
  2004年   16160篇
  2003年   15858篇
  2002年   15165篇
  2001年   15001篇
  2000年   14098篇
  1999年   14809篇
  1998年   37255篇
  1997年   25311篇
  1996年   19180篇
  1995年   14918篇
  1994年   13051篇
  1993年   13147篇
  1992年   9417篇
  1991年   8896篇
  1990年   8764篇
  1989年   8443篇
  1988年   7904篇
  1987年   7016篇
  1986年   6947篇
  1985年   7736篇
  1984年   7078篇
  1983年   6456篇
  1982年   5999篇
  1981年   6089篇
  1980年   5840篇
  1979年   5543篇
  1978年   5541篇
  1977年   6284篇
  1976年   8263篇
  1975年   4727篇
  1974年   4528篇
  1973年   4632篇
  1972年   3896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.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state....  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.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  相似文献   
9.
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   
10.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  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