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   430193篇
  免费   7023篇
  国内免费   1373篇
电工技术   7752篇
综合类   331篇
化学工业   65355篇
金属工艺   16948篇
机械仪表   14043篇
建筑科学   9133篇
矿业工程   2215篇
能源动力   12051篇
轻工业   33030篇
水利工程   4516篇
石油天然气   8012篇
武器工业   22篇
无线电   50225篇
一般工业技术   87539篇
冶金工业   81162篇
原子能技术   9293篇
自动化技术   36962篇
  2022年   2848篇
  2021年   4562篇
  2020年   3514篇
  2019年   4467篇
  2018年   7579篇
  2017年   7507篇
  2016年   8034篇
  2015年   5147篇
  2014年   8132篇
  2013年   22145篇
  2012年   12960篇
  2011年   16733篇
  2010年   13372篇
  2009年   14818篇
  2008年   15131篇
  2007年   14777篇
  2006年   13079篇
  2005年   11675篇
  2004年   11069篇
  2003年   10913篇
  2002年   10285篇
  2001年   10060篇
  2000年   9462篇
  1999年   9874篇
  1998年   26086篇
  1997年   17959篇
  1996年   13594篇
  1995年   10003篇
  1994年   8752篇
  1993年   8845篇
  1992年   6226篇
  1991年   5867篇
  1990年   5810篇
  1989年   5451篇
  1988年   5181篇
  1987年   4539篇
  1986年   4399篇
  1985年   4931篇
  1984年   4529篇
  1983年   4079篇
  1982年   3766篇
  1981年   3860篇
  1980年   3559篇
  1979年   3394篇
  1978年   3405篇
  1977年   3999篇
  1976年   5399篇
  1975年   2894篇
  1974年   2710篇
  1973年   2789篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
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.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
10.
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in...  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