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   553435篇
  免费   7336篇
  国内免费   1793篇
电工技术   10120篇
综合类   432篇
化学工业   82198篇
金属工艺   23706篇
机械仪表   18241篇
建筑科学   11620篇
矿业工程   3846篇
能源动力   14822篇
轻工业   38529篇
水利工程   6417篇
石油天然气   13070篇
武器工业   34篇
无线电   64257篇
一般工业技术   115099篇
冶金工业   101960篇
原子能技术   13377篇
自动化技术   44836篇
  2021年   5239篇
  2020年   4008篇
  2019年   5115篇
  2018年   8766篇
  2017年   8827篇
  2016年   9446篇
  2015年   5861篇
  2014年   9706篇
  2013年   26278篇
  2012年   15268篇
  2011年   20331篇
  2010年   16231篇
  2009年   18290篇
  2008年   18742篇
  2007年   18450篇
  2006年   16340篇
  2005年   14719篇
  2004年   13861篇
  2003年   13739篇
  2002年   13044篇
  2001年   13002篇
  2000年   12172篇
  1999年   12552篇
  1998年   32203篇
  1997年   22270篇
  1996年   17091篇
  1995年   12691篇
  1994年   11189篇
  1993年   11390篇
  1992年   8278篇
  1991年   7909篇
  1990年   7767篇
  1989年   7450篇
  1988年   7216篇
  1987年   6298篇
  1986年   6214篇
  1985年   6987篇
  1984年   6472篇
  1983年   5936篇
  1982年   5381篇
  1981年   5439篇
  1980年   5192篇
  1979年   5121篇
  1978年   5149篇
  1977年   5738篇
  1976年   7237篇
  1975年   4523篇
  1974年   4287篇
  1973年   4414篇
  1972年   3769篇
排序方式: 共有10000条查询结果,搜索用时 218 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.
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   
7.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  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.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
10.
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   
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