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   486130篇
  免费   6473篇
  国内免费   1769篇
电工技术   8333篇
综合类   2632篇
化学工业   71278篇
金属工艺   21063篇
机械仪表   16502篇
建筑科学   10537篇
矿业工程   2703篇
能源动力   12929篇
轻工业   32200篇
水利工程   5495篇
石油天然气   8283篇
武器工业   19篇
无线电   58486篇
一般工业技术   98613篇
冶金工业   77869篇
原子能技术   9417篇
自动化技术   58013篇
  2022年   2726篇
  2021年   4094篇
  2020年   3134篇
  2019年   3968篇
  2018年   20378篇
  2017年   19295篇
  2016年   16560篇
  2015年   5000篇
  2014年   7504篇
  2013年   20510篇
  2012年   14488篇
  2011年   24312篇
  2010年   20092篇
  2009年   19083篇
  2008年   20602篇
  2007年   21270篇
  2006年   12604篇
  2005年   12290篇
  2004年   11578篇
  2003年   11542篇
  2002年   10369篇
  2001年   9846篇
  2000年   9333篇
  1999年   9612篇
  1998年   24522篇
  1997年   16831篇
  1996年   12931篇
  1995年   9588篇
  1994年   8434篇
  1993年   8439篇
  1992年   6098篇
  1991年   5750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   3765篇
  1980年   3467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 31 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