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   1054820篇
  免费   15002篇
  国内免费   3729篇
电工技术   20009篇
技术理论   5篇
综合类   1959篇
化学工业   162668篇
金属工艺   43585篇
机械仪表   33042篇
建筑科学   24810篇
矿业工程   7554篇
能源动力   27404篇
轻工业   82685篇
水利工程   12461篇
石油天然气   23739篇
武器工业   308篇
无线电   114523篇
一般工业技术   212538篇
冶金工业   190191篇
原子能技术   23993篇
自动化技术   92077篇
  2021年   9964篇
  2020年   7449篇
  2019年   9205篇
  2018年   15491篇
  2017年   15516篇
  2016年   16477篇
  2015年   11169篇
  2014年   18189篇
  2013年   49248篇
  2012年   28873篇
  2011年   39125篇
  2010年   31390篇
  2009年   34884篇
  2008年   35831篇
  2007年   35623篇
  2006年   31174篇
  2005年   27782篇
  2004年   26214篇
  2003年   25730篇
  2002年   24753篇
  2001年   24261篇
  2000年   23046篇
  1999年   23319篇
  1998年   55870篇
  1997年   39992篇
  1996年   31031篇
  1995年   23444篇
  1994年   21265篇
  1993年   20902篇
  1992年   15710篇
  1991年   14933篇
  1990年   14846篇
  1989年   14416篇
  1988年   13644篇
  1987年   12390篇
  1986年   11995篇
  1985年   13685篇
  1984年   12601篇
  1983年   11816篇
  1982年   10768篇
  1981年   11056篇
  1980年   10377篇
  1979年   10695篇
  1978年   10412篇
  1977年   11743篇
  1976年   14854篇
  1975年   9293篇
  1974年   8999篇
  1973年   9035篇
  1972年   7739篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
1.
2.
3.
Grachev  A. I. 《Semiconductors》2022,56(2):67-70
Semiconductors - In this work, we discuss for the first time the principle of rotation in the constant electric field of a conducting particle with participation of the Lorentz force, which ensures...  相似文献   
4.
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   
5.
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   
6.
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   
7.
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   
8.
9.
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   
10.
Journal of Computer and Systems Sciences International - It is shown that the Lyapunov theorem on the distribution properties of the sum of random variables with different distribution densities...  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