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   547886篇
  免费   7246篇
  国内免费   1789篇
电工技术   10070篇
综合类   433篇
化学工业   81612篇
金属工艺   23619篇
机械仪表   18098篇
建筑科学   11421篇
矿业工程   3795篇
能源动力   14734篇
轻工业   38048篇
水利工程   6386篇
石油天然气   13056篇
武器工业   34篇
无线电   63845篇
一般工业技术   114262篇
冶金工业   99908篇
原子能技术   13318篇
自动化技术   44282篇
  2021年   5218篇
  2020年   3997篇
  2019年   5101篇
  2018年   8741篇
  2017年   8787篇
  2016年   9409篇
  2015年   5816篇
  2014年   9661篇
  2013年   26028篇
  2012年   15143篇
  2011年   20174篇
  2010年   16049篇
  2009年   18138篇
  2008年   18562篇
  2007年   18276篇
  2006年   16201篇
  2005年   14565篇
  2004年   13748篇
  2003年   13628篇
  2002年   12914篇
  2001年   12902篇
  2000年   12062篇
  1999年   12463篇
  1998年   31658篇
  1997年   21884篇
  1996年   16839篇
  1995年   12489篇
  1994年   11014篇
  1993年   11188篇
  1992年   8196篇
  1991年   7845篇
  1990年   7690篇
  1989年   7359篇
  1988年   7138篇
  1987年   6241篇
  1986年   6155篇
  1985年   6910篇
  1984年   6392篇
  1983年   5865篇
  1982年   5323篇
  1981年   5385篇
  1980年   5124篇
  1979年   5056篇
  1978年   5079篇
  1977年   5628篇
  1976年   7047篇
  1975年   4472篇
  1974年   4231篇
  1973年   4364篇
  1972年   3733篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
Wireless Personal Communications - In the present scenario, there is a boom in the demand of the users to achieve increased capacity, high data, low latency, and high-performance rates. 5G New...  相似文献   
10.
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   
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