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   900803篇
  免费   11730篇
  国内免费   2444篇
电工技术   15951篇
综合类   2985篇
化学工业   133881篇
金属工艺   37509篇
机械仪表   29196篇
建筑科学   20506篇
矿业工程   5935篇
能源动力   23487篇
轻工业   66819篇
水利工程   10649篇
石油天然气   18417篇
武器工业   46篇
无线电   101400篇
一般工业技术   181839篇
冶金工业   153067篇
原子能技术   19340篇
自动化技术   93950篇
  2021年   7603篇
  2020年   5788篇
  2019年   7384篇
  2018年   25684篇
  2017年   24756篇
  2016年   22475篇
  2015年   9115篇
  2014年   14511篇
  2013年   39379篇
  2012年   25297篇
  2011年   39096篇
  2010年   31915篇
  2009年   32527篇
  2008年   34182篇
  2007年   34588篇
  2006年   24388篇
  2005年   22967篇
  2004年   21892篇
  2003年   21720篇
  2002年   20174篇
  2001年   19386篇
  2000年   18483篇
  1999年   18670篇
  1998年   45705篇
  1997年   32264篇
  1996年   24131篇
  1995年   18804篇
  1994年   16815篇
  1993年   16623篇
  1992年   12397篇
  1991年   11814篇
  1990年   11686篇
  1989年   11224篇
  1988年   10672篇
  1987年   9635篇
  1986年   9274篇
  1985年   10627篇
  1984年   9661篇
  1983年   9013篇
  1982年   8211篇
  1981年   8375篇
  1980年   7846篇
  1979年   7911篇
  1978年   7759篇
  1977年   8783篇
  1976年   11193篇
  1975年   6868篇
  1974年   6583篇
  1973年   6682篇
  1972年   5656篇
排序方式: 共有10000条查询结果,搜索用时 484 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