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   1526481篇
  免费   30605篇
  国内免费   9761篇
电工技术   37741篇
技术理论   7篇
综合类   9818篇
化学工业   278613篇
金属工艺   66844篇
机械仪表   44850篇
建筑科学   49258篇
矿业工程   13058篇
能源动力   51471篇
轻工业   115005篇
水利工程   15570篇
石油天然气   40605篇
武器工业   700篇
无线电   201400篇
一般工业技术   284912篇
冶金工业   148405篇
原子能技术   34367篇
自动化技术   174223篇
  2021年   18066篇
  2020年   13559篇
  2019年   16145篇
  2018年   16673篇
  2017年   16006篇
  2016年   22518篇
  2015年   19551篇
  2014年   31240篇
  2013年   90852篇
  2012年   38377篇
  2011年   50900篇
  2010年   45270篇
  2009年   53536篇
  2008年   47247篇
  2007年   44203篇
  2006年   47366篇
  2005年   41166篇
  2004年   42347篇
  2003年   42052篇
  2002年   41307篇
  2001年   37707篇
  2000年   36321篇
  1999年   34960篇
  1998年   39874篇
  1997年   36481篇
  1996年   33621篇
  1995年   29814篇
  1994年   28085篇
  1993年   27811篇
  1992年   26173篇
  1991年   23111篇
  1990年   23457篇
  1989年   22506篇
  1988年   21015篇
  1987年   19264篇
  1986年   18576篇
  1985年   21912篇
  1984年   22286篇
  1983年   20216篇
  1982年   19198篇
  1981年   19295篇
  1980年   17860篇
  1979年   18486篇
  1978年   17696篇
  1977年   17122篇
  1976年   17755篇
  1975年   15964篇
  1974年   15513篇
  1973年   15557篇
  1972年   13044篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Zhao  Jiandong  Lei  Wei  Li  Zijian  Zhao  Dongfeng  Han  Mingmin  Hou  Xiaoqing 《Multimedia Tools and Applications》2022,81(4):4753-4780
Multimedia Tools and Applications - The crowding in bus is an important factor affecting passenger satisfaction and bus dispatching level. However, how to use video images to detect crowding...  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.
4.
5.
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   
6.
Journal of Computer and Systems Sciences International - It is shown that the Lyapunov theorem on the distribution properties of the sum of random variables with different distribution densities...  相似文献   
7.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  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.
Multimedia Tools and Applications - Recently, many concepts in technology has been changed. According to the digital transformation trends, Internet of Things (IoT) represents an interested...  相似文献   
10.
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell.  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