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   476478篇
  免费   6455篇
  国内免费   1805篇
电工技术   9118篇
综合类   1976篇
化学工业   70251篇
金属工艺   18785篇
机械仪表   15809篇
建筑科学   10524篇
矿业工程   3095篇
能源动力   12243篇
轻工业   32105篇
水利工程   5295篇
石油天然气   9030篇
武器工业   34篇
无线电   55931篇
一般工业技术   92001篇
冶金工业   95431篇
原子能技术   9663篇
自动化技术   43447篇
  2022年   4900篇
  2021年   6587篇
  2020年   4947篇
  2019年   6195篇
  2018年   7787篇
  2017年   7709篇
  2016年   8247篇
  2015年   5365篇
  2014年   7879篇
  2013年   21071篇
  2012年   13814篇
  2011年   18909篇
  2010年   13918篇
  2009年   15684篇
  2008年   15231篇
  2007年   15016篇
  2006年   13653篇
  2005年   15058篇
  2004年   14680篇
  2003年   13960篇
  2002年   12297篇
  2001年   11724篇
  2000年   10335篇
  1999年   10733篇
  1998年   29725篇
  1997年   20236篇
  1996年   15251篇
  1995年   11024篇
  1994年   9710篇
  1993年   9631篇
  1992年   6597篇
  1991年   6184篇
  1990年   6187篇
  1989年   5884篇
  1988年   5596篇
  1987年   4836篇
  1986年   4769篇
  1985年   5241篇
  1984年   4653篇
  1983年   4309篇
  1982年   3981篇
  1981年   4069篇
  1980年   3710篇
  1979年   3492篇
  1978年   3612篇
  1977年   4521篇
  1976年   6212篇
  1975年   3126篇
  1974年   2844篇
  1973年   2870篇
排序方式: 共有10000条查询结果,搜索用时 0 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.
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.
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   
10.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  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