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   661172篇
  免费   8210篇
  国内免费   2516篇
电工技术   12217篇
综合类   869篇
化学工业   95798篇
金属工艺   29464篇
机械仪表   22728篇
建筑科学   14542篇
矿业工程   3807篇
能源动力   17074篇
轻工业   46621篇
水利工程   7258篇
石油天然气   12923篇
武器工业   56篇
无线电   78033篇
一般工业技术   136055篇
冶金工业   119164篇
原子能技术   14967篇
自动化技术   60322篇
  2021年   5343篇
  2020年   4077篇
  2019年   5215篇
  2018年   14289篇
  2017年   14576篇
  2016年   12656篇
  2015年   6438篇
  2014年   10246篇
  2013年   28851篇
  2012年   18032篇
  2011年   27652篇
  2010年   22934篇
  2009年   24484篇
  2008年   24990篇
  2007年   26134篇
  2006年   18087篇
  2005年   18694篇
  2004年   17084篇
  2003年   16650篇
  2002年   15319篇
  2001年   14820篇
  2000年   14013篇
  1999年   14644篇
  1998年   37040篇
  1997年   25824篇
  1996年   19844篇
  1995年   14950篇
  1994年   13107篇
  1993年   13218篇
  1992年   9466篇
  1991年   8961篇
  1990年   8807篇
  1989年   8504篇
  1988年   7998篇
  1987年   7066篇
  1986年   7015篇
  1985年   7803篇
  1984年   7149篇
  1983年   6541篇
  1982年   6060篇
  1981年   6158篇
  1980年   5900篇
  1979年   5593篇
  1978年   5593篇
  1977年   6329篇
  1976年   8301篇
  1975年   4750篇
  1974年   4566篇
  1973年   4673篇
  1972年   3919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.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state....  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.
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.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  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.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  相似文献   
10.

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.

  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