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   594023篇
  免费   7357篇
  国内免费   1824篇
电工技术   11084篇
综合类   503篇
化学工业   86839篇
金属工艺   28300篇
机械仪表   21156篇
建筑科学   12337篇
矿业工程   4225篇
能源动力   15105篇
轻工业   38921篇
水利工程   7071篇
石油天然气   13664篇
武器工业   35篇
无线电   67992篇
一般工业技术   126035篇
冶金工业   103119篇
原子能技术   13837篇
自动化技术   52981篇
  2021年   5204篇
  2020年   3983篇
  2019年   5074篇
  2018年   13889篇
  2017年   14224篇
  2016年   12535篇
  2015年   6122篇
  2014年   9707篇
  2013年   26037篇
  2012年   16762篇
  2011年   25403篇
  2010年   21187篇
  2009年   22326篇
  2008年   22875篇
  2007年   23886篇
  2006年   16243篇
  2005年   16703篇
  2004年   14973篇
  2003年   14674篇
  2002年   13381篇
  2001年   12939篇
  2000年   12166篇
  1999年   12468篇
  1998年   31664篇
  1997年   21895篇
  1996年   16848篇
  1995年   12500篇
  1994年   11034篇
  1993年   11206篇
  1992年   8207篇
  1991年   7861篇
  1990年   7692篇
  1989年   7356篇
  1988年   7143篇
  1987年   6240篇
  1986年   6155篇
  1985年   6911篇
  1984年   6392篇
  1983年   5864篇
  1982年   5324篇
  1981年   5384篇
  1980年   5124篇
  1979年   5057篇
  1978年   5082篇
  1977年   5632篇
  1976年   7055篇
  1975年   4476篇
  1974年   4234篇
  1973年   4365篇
  1972年   3734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.
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.
Telecommunication Systems - Energy saving in User Equipment (UE) is one of the important issues for limited sources of power in the device. It is critical for the UE to maximize its energy...  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