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   635517篇
  免费   10640篇
  国内免费   1983篇
电工技术   11591篇
综合类   630篇
化学工业   94119篇
金属工艺   24490篇
机械仪表   20147篇
建筑科学   14488篇
矿业工程   3053篇
能源动力   17063篇
轻工业   52157篇
水利工程   6551篇
石油天然气   10715篇
武器工业   86篇
无线电   76043篇
一般工业技术   125738篇
冶金工业   120657篇
原子能技术   13010篇
自动化技术   57602篇
  2021年   6265篇
  2020年   4871篇
  2019年   6110篇
  2018年   10357篇
  2017年   10355篇
  2016年   11076篇
  2015年   7204篇
  2014年   11416篇
  2013年   31514篇
  2012年   18278篇
  2011年   23841篇
  2010年   19051篇
  2009年   21066篇
  2008年   21939篇
  2007年   21505篇
  2006年   19052篇
  2005年   17056篇
  2004年   16290篇
  2003年   16124篇
  2002年   15245篇
  2001年   14907篇
  2000年   14138篇
  1999年   14754篇
  1998年   37719篇
  1997年   26305篇
  1996年   20080篇
  1995年   15006篇
  1994年   13208篇
  1993年   13245篇
  1992年   9670篇
  1991年   9076篇
  1990年   8885篇
  1989年   8361篇
  1988年   8030篇
  1987年   7085篇
  1986年   6897篇
  1985年   7841篇
  1984年   7209篇
  1983年   6443篇
  1982年   6042篇
  1981年   6231篇
  1980年   5825篇
  1979年   5573篇
  1978年   5418篇
  1977年   6472篇
  1976年   8440篇
  1975年   4826篇
  1974年   4636篇
  1973年   4691篇
  1972年   3811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.
7.
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   
8.
Virtual Reality - It is generally accepted that natural environments reduce stress and improve mood. Since access to natural environments is sometimes limited, virtual natural environments,...  相似文献   
9.
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   
10.
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   
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