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   538032篇
  免费   9136篇
  国内免费   1819篇
电工技术   8763篇
综合类   2666篇
化学工业   81632篇
金属工艺   21986篇
机械仪表   17572篇
建筑科学   12959篇
矿业工程   2856篇
能源动力   14032篇
轻工业   38540篇
水利工程   6021篇
石油天然气   8443篇
武器工业   26篇
无线电   60934篇
一般工业技术   107220篇
冶金工业   89193篇
原子能技术   9743篇
自动化技术   66401篇
  2022年   3201篇
  2021年   5126篇
  2020年   3902篇
  2019年   4995篇
  2018年   21497篇
  2017年   20355篇
  2016年   17956篇
  2015年   6347篇
  2014年   9211篇
  2013年   24374篇
  2012年   17199篇
  2011年   27048篇
  2010年   22339篇
  2009年   21232篇
  2008年   22895篇
  2007年   23414篇
  2006年   14580篇
  2005年   14013篇
  2004年   13089篇
  2003年   12923篇
  2002年   11676篇
  2001年   10769篇
  2000年   10117篇
  1999年   10454篇
  1998年   26622篇
  1997年   18487篇
  1996年   14112篇
  1995年   10517篇
  1994年   9215篇
  1993年   9292篇
  1992年   6679篇
  1991年   6150篇
  1990年   6187篇
  1989年   5796篇
  1988年   5483篇
  1987年   4850篇
  1986年   4676篇
  1985年   5306篇
  1984年   4902篇
  1983年   4374篇
  1982年   4024篇
  1981年   4114篇
  1980年   3812篇
  1979年   3632篇
  1978年   3629篇
  1977年   4204篇
  1976年   5585篇
  1975年   3072篇
  1974年   2870篇
  1973年   2942篇
排序方式: 共有10000条查询结果,搜索用时 15 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