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   524825篇
  免费   6504篇
  国内免费   1762篇
电工技术   9388篇
综合类   2642篇
化学工业   75150篇
金属工艺   25151篇
机械仪表   20175篇
建筑科学   11231篇
矿业工程   3208篇
能源动力   13291篇
轻工业   32360篇
水利工程   5973篇
石油天然气   9166篇
武器工业   19篇
无线电   61801篇
一般工业技术   109195篇
冶金工业   81091篇
原子能技术   10046篇
自动化技术   63204篇
  2022年   2473篇
  2021年   4094篇
  2020年   3144篇
  2019年   3975篇
  2018年   24165篇
  2017年   23571篇
  2016年   18496篇
  2015年   5286篇
  2014年   7567篇
  2013年   20569篇
  2012年   15792篇
  2011年   28702篇
  2010年   24393篇
  2009年   23040篇
  2008年   24190篇
  2007年   26041篇
  2006年   12643篇
  2005年   14689篇
  2004年   12761篇
  2003年   12504篇
  2002年   10775篇
  2001年   9887篇
  2000年   9412篇
  1999年   9621篇
  1998年   24525篇
  1997年   16833篇
  1996年   12937篇
  1995年   9598篇
  1994年   8451篇
  1993年   8457篇
  1992年   6110篇
  1991年   5771篇
  1990年   5708篇
  1989年   5356篇
  1988年   5082篇
  1987年   4445篇
  1986年   4339篇
  1985年   4862篇
  1984年   4454篇
  1983年   4029篇
  1982年   3688篇
  1981年   3764篇
  1980年   3466篇
  1979年   3355篇
  1978年   3354篇
  1977年   3780篇
  1976年   4880篇
  1975年   2861篇
  1974年   2682篇
  1973年   2742篇
排序方式: 共有10000条查询结果,搜索用时 419 毫秒
1.
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   
2.
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   
3.
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   
4.
5.
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   
6.
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   
7.
Wireless Personal Communications - In the present scenario, there is a boom in the demand of the users to achieve increased capacity, high data, low latency, and high-performance rates. 5G New...  相似文献   
8.
Telecommunication Systems - Energy saving in User Equipment (UE) is one of the important issues for limited sources of power in the device. It is critical for the UE to maximize its energy...  相似文献   
9.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
10.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  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