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   450830篇
  免费   6473篇
  国内免费   1645篇
电工技术   8740篇
综合类   1392篇
化学工业   68227篇
金属工艺   18491篇
机械仪表   15255篇
建筑科学   10282篇
矿业工程   2742篇
能源动力   12287篇
轻工业   31190篇
水利工程   4861篇
石油天然气   9035篇
武器工业   30篇
无线电   55039篇
一般工业技术   91152篇
冶金工业   79990篇
原子能技术   9597篇
自动化技术   40638篇
  2022年   4755篇
  2021年   6929篇
  2020年   5231篇
  2019年   6466篇
  2018年   7714篇
  2017年   7406篇
  2016年   7661篇
  2015年   4974篇
  2014年   7943篇
  2013年   21532篇
  2012年   12666篇
  2011年   17623篇
  2010年   13935篇
  2009年   15575篇
  2008年   15293篇
  2007年   15059篇
  2006年   13594篇
  2005年   12326篇
  2004年   12529篇
  2003年   12311篇
  2002年   11738篇
  2001年   11186篇
  2000年   10217篇
  1999年   10420篇
  1998年   25172篇
  1997年   17443篇
  1996年   13360篇
  1995年   10004篇
  1994年   8972篇
  1993年   8852篇
  1992年   6485篇
  1991年   5990篇
  1990年   6034篇
  1989年   5750篇
  1988年   5414篇
  1987年   4721篇
  1986年   4689篇
  1985年   5164篇
  1984年   4675篇
  1983年   4298篇
  1982年   3953篇
  1981年   3977篇
  1980年   3608篇
  1979年   3493篇
  1978年   3573篇
  1977年   4032篇
  1976年   5068篇
  1975年   3079篇
  1974年   2836篇
  1973年   2854篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the...  相似文献   
2.
3.
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   
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.
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.
9.
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   
10.
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   
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