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   622826篇
  免费   8250篇
  国内免费   1910篇
电工技术   11401篇
综合类   459篇
化学工业   94137篇
金属工艺   25098篇
机械仪表   19623篇
建筑科学   14042篇
矿业工程   3583篇
能源动力   16779篇
轻工业   49266篇
水利工程   6656篇
石油天然气   12860篇
武器工业   28篇
无线电   72489篇
一般工业技术   125126篇
冶金工业   116227篇
原子能技术   14225篇
自动化技术   50987篇
  2021年   5379篇
  2020年   4181篇
  2019年   5225篇
  2018年   9013篇
  2017年   8926篇
  2016年   9645篇
  2015年   6131篇
  2014年   10151篇
  2013年   29183篇
  2012年   16277篇
  2011年   22069篇
  2010年   17678篇
  2009年   20117篇
  2008年   20607篇
  2007年   20278篇
  2006年   18074篇
  2005年   16438篇
  2004年   15496篇
  2003年   15335篇
  2002年   14773篇
  2001年   14565篇
  2000年   13744篇
  1999年   14216篇
  1998年   35881篇
  1997年   25402篇
  1996年   19610篇
  1995年   14684篇
  1994年   13053篇
  1993年   12946篇
  1992年   9522篇
  1991年   9087篇
  1990年   8988篇
  1989年   8722篇
  1988年   8443篇
  1987年   7224篇
  1986年   7186篇
  1985年   8145篇
  1984年   7586篇
  1983年   6908篇
  1982年   6458篇
  1981年   6577篇
  1980年   6192篇
  1979年   6042篇
  1978年   6163篇
  1977年   7036篇
  1976年   9078篇
  1975年   5404篇
  1974年   5077篇
  1973年   5220篇
  1972年   4432篇
排序方式: 共有10000条查询结果,搜索用时 65 毫秒
1.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the...  相似文献   
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.
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical...  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.
Engineering new glass compositions have experienced a sturdy tendency to move forward from (educated) trial-and-error to data- and simulation-driven strategies. In this work, we developed a computer program that combines data-driven predictive models (in this case, neural networks) with a genetic algorithm to design glass compositions with desired combinations of properties. First, we induced predictive models for the glass transition temperature (Tg) using a dataset of 45,302 compositions with 39 different chemical elements, and for the refractive index (nd) using a dataset of 41,225 compositions with 38 different chemical elements. Then, we searched for relevant glass compositions using a genetic algorithm informed by a design trend of glasses having high nd (1.7 or more) and low Tg (500 °C or less). Two candidate compositions suggested by the combined algorithms were selected and produced in the laboratory. These compositions are significantly different from those in the datasets used to induce the predictive models, showing that the used method is indeed capable of exploration. Both glasses met the constraints of the work, which supports the proposed framework. Therefore, this new tool can be immediately used for accelerating the design of new glasses. These results are a stepping stone in the pathway of machine learning-guided design of novel glasses.  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