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   647242篇
  免费   8293篇
  国内免费   1392篇
电工技术   11270篇
综合类   2784篇
化学工业   100932篇
金属工艺   27914篇
机械仪表   21537篇
建筑科学   14780篇
矿业工程   4855篇
能源动力   15792篇
轻工业   49740篇
水利工程   8129篇
石油天然气   15293篇
武器工业   42篇
无线电   69132篇
一般工业技术   131530篇
冶金工业   97982篇
原子能技术   14939篇
自动化技术   70276篇
  2021年   5670篇
  2020年   4179篇
  2019年   5414篇
  2018年   23039篇
  2017年   22141篇
  2016年   19491篇
  2015年   6734篇
  2014年   10663篇
  2013年   26826篇
  2012年   18889篇
  2011年   30031篇
  2010年   24858篇
  2009年   24226篇
  2008年   25546篇
  2007年   26129篇
  2006年   16465篇
  2005年   15865篇
  2004年   15071篇
  2003年   14792篇
  2002年   13775篇
  2001年   12971篇
  2000年   12509篇
  1999年   12071篇
  1998年   27708篇
  1997年   20067篇
  1996年   15669篇
  1995年   12015篇
  1994年   10873篇
  1993年   10622篇
  1992年   8342篇
  1991年   8125篇
  1990年   7996篇
  1989年   7767篇
  1988年   7489篇
  1987年   6747篇
  1986年   6533篇
  1985年   7392篇
  1984年   6703篇
  1983年   6438篇
  1982年   5776篇
  1981年   5898篇
  1980年   5631篇
  1979年   5734篇
  1978年   5664篇
  1977年   6178篇
  1976年   7687篇
  1975年   5109篇
  1974年   4904篇
  1973年   4980篇
  1972年   4280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.
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.
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   
6.
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   
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.
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   
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.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  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