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   655321篇
  免费   10133篇
  国内免费   1938篇
电工技术   11603篇
综合类   486篇
化学工业   100500篇
金属工艺   25647篇
机械仪表   20208篇
建筑科学   14986篇
矿业工程   3666篇
能源动力   17354篇
轻工业   54628篇
水利工程   6965篇
石油天然气   12969篇
武器工业   35篇
无线电   73560篇
一般工业技术   130022篇
冶金工业   124902篇
原子能技术   14324篇
自动化技术   55537篇
  2021年   6144篇
  2020年   4804篇
  2019年   5996篇
  2018年   10224篇
  2017年   10111篇
  2016年   10935篇
  2015年   7093篇
  2014年   11321篇
  2013年   31595篇
  2012年   18068篇
  2011年   23683篇
  2010年   19078篇
  2009年   21396篇
  2008年   21862篇
  2007年   21389篇
  2006年   18825篇
  2005年   17090篇
  2004年   16146篇
  2003年   15910篇
  2002年   15285篇
  2001年   14927篇
  2000年   14094篇
  1999年   14657篇
  1998年   38390篇
  1997年   27014篇
  1996年   20676篇
  1995年   15308篇
  1994年   13549篇
  1993年   13582篇
  1992年   9700篇
  1991年   9284篇
  1990年   9146篇
  1989年   8866篇
  1988年   8602篇
  1987年   7369篇
  1986年   7314篇
  1985年   8299篇
  1984年   7699篇
  1983年   6995篇
  1982年   6582篇
  1981年   6732篇
  1980年   6351篇
  1979年   6102篇
  1978年   6230篇
  1977年   7348篇
  1976年   9725篇
  1975年   5444篇
  1974年   5120篇
  1973年   5264篇
  1972年   4444篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the...  相似文献   
2.
3.
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   
4.
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   
5.
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   
6.
7.
8.
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   
9.
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical...  相似文献   
10.
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   
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