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   656839篇
  免费   9609篇
  国内免费   1928篇
电工技术   12225篇
综合类   614篇
化学工业   96833篇
金属工艺   25015篇
机械仪表   18878篇
建筑科学   15593篇
矿业工程   2836篇
能源动力   17786篇
轻工业   55871篇
水利工程   6345篇
石油天然气   11165篇
武器工业   43篇
无线电   77736篇
一般工业技术   126745篇
冶金工业   133615篇
原子能技术   12815篇
自动化技术   54261篇
  2021年   5682篇
  2020年   4132篇
  2019年   5413篇
  2018年   9134篇
  2017年   8912篇
  2016年   9306篇
  2015年   6523篇
  2014年   10925篇
  2013年   29720篇
  2012年   17413篇
  2011年   24060篇
  2010年   19054篇
  2009年   21445篇
  2008年   22061篇
  2007年   21775篇
  2006年   19143篇
  2005年   17662篇
  2004年   17070篇
  2003年   16736篇
  2002年   15935篇
  2001年   16164篇
  2000年   15108篇
  1999年   16197篇
  1998年   42428篇
  1997年   29433篇
  1996年   22667篇
  1995年   16913篇
  1994年   14695篇
  1993年   14411篇
  1992年   10232篇
  1991年   9721篇
  1990年   9498篇
  1989年   9162篇
  1988年   8471篇
  1987年   7376篇
  1986年   7281篇
  1985年   8218篇
  1984年   7581篇
  1983年   6704篇
  1982年   6275篇
  1981年   6483篇
  1980年   6051篇
  1979年   5856篇
  1978年   5634篇
  1977年   6840篇
  1976年   9019篇
  1975年   4887篇
  1974年   4604篇
  1973年   4656篇
  1972年   3846篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
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   
5.
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   
6.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast...  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.
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   
9.
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   
10.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  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