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   442907篇
  免费   5800篇
  国内免费   1636篇
电工技术   8678篇
综合类   1356篇
化学工业   66803篇
金属工艺   18338篇
机械仪表   15076篇
建筑科学   9976篇
矿业工程   2711篇
能源动力   11950篇
轻工业   30539篇
水利工程   4796篇
石油天然气   8995篇
武器工业   32篇
无线电   54378篇
一般工业技术   89403篇
冶金工业   79034篇
原子能技术   9531篇
自动化技术   38747篇
  2022年   4821篇
  2021年   6527篇
  2020年   4953篇
  2019年   6212篇
  2018年   7354篇
  2017年   7068篇
  2016年   7262篇
  2015年   4647篇
  2014年   7525篇
  2013年   20870篇
  2012年   12005篇
  2011年   16884篇
  2010年   13437篇
  2009年   15118篇
  2008年   14866篇
  2007年   14611篇
  2006年   13297篇
  2005年   12072篇
  2004年   12381篇
  2003年   12127篇
  2002年   11596篇
  2001年   11091篇
  2000年   10125篇
  1999年   10318篇
  1998年   25074篇
  1997年   17350篇
  1996年   13284篇
  1995年   9939篇
  1994年   8923篇
  1993年   8803篇
  1992年   6457篇
  1991年   5990篇
  1990年   5995篇
  1989年   5729篇
  1988年   5398篇
  1987年   4695篇
  1986年   4674篇
  1985年   5157篇
  1984年   4659篇
  1983年   4311篇
  1982年   3941篇
  1981年   3976篇
  1980年   3609篇
  1979年   3493篇
  1978年   3570篇
  1977年   4019篇
  1976年   5057篇
  1975年   3087篇
  1974年   2841篇
  1973年   2869篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
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.
5.
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   
6.
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.
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   
10.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast...  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