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   416249篇
  免费   6377篇
  国内免费   1462篇
电工技术   7766篇
综合类   394篇
化学工业   62944篇
金属工艺   16781篇
机械仪表   13987篇
建筑科学   8847篇
矿业工程   2173篇
能源动力   12500篇
轻工业   29767篇
水利工程   4450篇
石油天然气   8124篇
武器工业   21篇
无线电   50616篇
一般工业技术   85486篇
冶金工业   75467篇
原子能技术   9275篇
自动化技术   35490篇
  2022年   2849篇
  2021年   4800篇
  2020年   3735篇
  2019年   4637篇
  2018年   7443篇
  2017年   7342篇
  2016年   7746篇
  2015年   4805篇
  2014年   7916篇
  2013年   21384篇
  2012年   12321篇
  2011年   16195篇
  2010年   12792篇
  2009年   14286篇
  2008年   14434篇
  2007年   14154篇
  2006年   12705篇
  2005年   11291篇
  2004年   10674篇
  2003年   10563篇
  2002年   9946篇
  2001年   9818篇
  2000年   9213篇
  1999年   9596篇
  1998年   24454篇
  1997年   16827篇
  1996年   12890篇
  1995年   9581篇
  1994年   8413篇
  1993年   8440篇
  1992年   6103篇
  1991年   5732篇
  1990年   5712篇
  1989年   5355篇
  1988年   5076篇
  1987年   4447篇
  1986年   4334篇
  1985年   4833篇
  1984年   4443篇
  1983年   4020篇
  1982年   3678篇
  1981年   3746篇
  1980年   3445篇
  1979年   3341篇
  1978年   3351篇
  1977年   3768篇
  1976年   4868篇
  1975年   2862篇
  1974年   2674篇
  1973年   2734篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
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.
Journal of Materials Science - Chitosan is one of the natural cationic polymers with unique properties such as non-toxicity, biodegradability, biocompatibility, environmentally friendly that has...  相似文献   
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.
Journal of Inorganic and Organometallic Polymers and Materials - Immobility of copper on magnetic nanoparticles was performed using surface rectification of Fe3O4 with Agar. The magnetic...  相似文献   
9.
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   
10.
International Journal of Control, Automation and Systems - In this paper, a new controllable simulator is proposed and modeled by which, experimental tests of the aircraft’s models can be...  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