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   861545篇
  免费   11647篇
  国内免费   2239篇
电工技术   15875篇
综合类   1324篇
化学工业   130465篇
金属工艺   33780篇
机械仪表   27396篇
建筑科学   19351篇
矿业工程   5806篇
能源动力   22828篇
轻工业   65937篇
水利工程   9984篇
石油天然气   18233篇
武器工业   50篇
无线电   94660篇
一般工业技术   171175篇
冶金工业   163433篇
原子能技术   19268篇
自动化技术   75866篇
  2021年   7715篇
  2020年   5786篇
  2019年   7409篇
  2018年   13103篇
  2017年   13396篇
  2016年   14365篇
  2015年   9312篇
  2014年   14695篇
  2013年   39525篇
  2012年   24313篇
  2011年   32801篇
  2010年   25105篇
  2009年   28195篇
  2008年   28541篇
  2007年   28155篇
  2006年   24720篇
  2005年   25291篇
  2004年   23494篇
  2003年   22705篇
  2002年   20440篇
  2001年   19947篇
  2000年   18544篇
  1999年   18952篇
  1998年   48852篇
  1997年   34349篇
  1996年   26507篇
  1995年   19791篇
  1994年   17542篇
  1993年   17393篇
  1992年   12649篇
  1991年   12072篇
  1990年   11940篇
  1989年   11516篇
  1988年   10966篇
  1987年   9882篇
  1986年   9490篇
  1985年   10816篇
  1984年   9779篇
  1983年   9152篇
  1982年   8376篇
  1981年   8586篇
  1980年   8024篇
  1979年   8003篇
  1978年   7867篇
  1977年   9291篇
  1976年   12211篇
  1975年   6970篇
  1974年   6647篇
  1973年   6756篇
  1972年   5716篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
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   
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.
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   
10.
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   
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