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   408189篇
  免费   5693篇
  国内免费   1368篇
电工技术   7628篇
综合类   324篇
化学工业   60529篇
金属工艺   16617篇
机械仪表   13785篇
建筑科学   8459篇
矿业工程   2155篇
能源动力   11764篇
轻工业   28908篇
水利工程   4265篇
石油天然气   7922篇
武器工业   17篇
无线电   50392篇
一般工业技术   84043篇
冶金工业   75359篇
原子能技术   9249篇
自动化技术   33834篇
  2022年   2347篇
  2021年   4029篇
  2020年   3030篇
  2019年   3923篇
  2018年   6646篇
  2017年   6618篇
  2016年   7104篇
  2015年   4467篇
  2014年   7360篇
  2013年   20452篇
  2012年   11767篇
  2011年   15705篇
  2010年   12435篇
  2009年   14056篇
  2008年   14336篇
  2007年   14033篇
  2006年   12599篇
  2005年   11312篇
  2004年   10650篇
  2003年   10568篇
  2002年   9967篇
  2001年   9840篇
  2000年   9235篇
  1999年   9617篇
  1998年   24532篇
  1997年   16815篇
  1996年   12905篇
  1995年   9615篇
  1994年   8424篇
  1993年   8442篇
  1992年   6096篇
  1991年   5732篇
  1990年   5714篇
  1989年   5347篇
  1988年   5070篇
  1987年   4442篇
  1986年   4320篇
  1985年   4825篇
  1984年   4437篇
  1983年   4010篇
  1982年   3672篇
  1981年   3737篇
  1980年   3438篇
  1979年   3330篇
  1978年   3338篇
  1977年   3758篇
  1976年   4858篇
  1975年   2854篇
  1974年   2668篇
  1973年   2734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.
6.
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   
7.
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   
8.
International Journal of Information Security - This paper deals with a well-known problem in the area of the smudge attacks: when a user draws a pattern to unlock the pattern lock on a smartphone...  相似文献   
9.
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex...  相似文献   
10.
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   
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