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   615395篇
  免费   8327篇
  国内免费   2555篇
电工技术   11211篇
综合类   880篇
化学工业   90121篇
金属工艺   24815篇
机械仪表   19467篇
建筑科学   13627篇
矿业工程   3391篇
能源动力   16780篇
轻工业   46022篇
水利工程   6591篇
石油天然气   12182篇
武器工业   71篇
无线电   74197篇
一般工业技术   124550篇
冶金工业   115938篇
原子能技术   14418篇
自动化技术   52016篇
  2021年   5590篇
  2020年   4230篇
  2019年   5357篇
  2018年   9033篇
  2017年   9056篇
  2016年   9677篇
  2015年   6243篇
  2014年   10337篇
  2013年   29024篇
  2012年   16494篇
  2011年   22328篇
  2010年   17677篇
  2009年   20226篇
  2008年   20644篇
  2007年   20468篇
  2006年   18150篇
  2005年   16431篇
  2004年   15907篇
  2003年   15642篇
  2002年   14927篇
  2001年   14826篇
  2000年   13945篇
  1999年   14653篇
  1998年   37087篇
  1997年   25848篇
  1996年   19840篇
  1995年   14963篇
  1994年   13107篇
  1993年   13229篇
  1992年   9475篇
  1991年   8957篇
  1990年   8818篇
  1989年   8512篇
  1988年   8000篇
  1987年   7077篇
  1986年   7021篇
  1985年   7802篇
  1984年   7150篇
  1983年   6537篇
  1982年   6068篇
  1981年   6164篇
  1980年   5909篇
  1979年   5598篇
  1978年   5594篇
  1977年   6334篇
  1976年   8315篇
  1975年   4749篇
  1974年   4568篇
  1973年   4676篇
  1972年   3921篇
排序方式: 共有10000条查询结果,搜索用时 375 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