首页 | 官方网站   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   426512篇
  免费   6999篇
  国内免费   1370篇
工业技术   434881篇
  2021年   4449篇
  2020年   3477篇
  2019年   4408篇
  2018年   7569篇
  2017年   7501篇
  2016年   8020篇
  2015年   5133篇
  2014年   8101篇
  2013年   22100篇
  2012年   12899篇
  2011年   16627篇
  2010年   13305篇
  2009年   14727篇
  2008年   15054篇
  2007年   14723篇
  2006年   13010篇
  2005年   11636篇
  2004年   11026篇
  2003年   10866篇
  2002年   10250篇
  2001年   10041篇
  2000年   9435篇
  1999年   9849篇
  1998年   26073篇
  1997年   17893篇
  1996年   13088篇
  1995年   9913篇
  1994年   8664篇
  1993年   8764篇
  1992年   6165篇
  1991年   5814篇
  1990年   5756篇
  1989年   5386篇
  1988年   5112篇
  1987年   4487篇
  1986年   4350篇
  1985年   4885篇
  1984年   4482篇
  1983年   4028篇
  1982年   3718篇
  1981年   3806篇
  1980年   3528篇
  1979年   3369篇
  1978年   3372篇
  1977年   3967篇
  1976年   5375篇
  1975年   2880篇
  1974年   2684篇
  1973年   2764篇
  1972年   2286篇
排序方式: 共有10000条查询结果,搜索用时 500 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-23

京公网安备 11010802026262号