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   769334篇
  免费   10776篇
  国内免费   2332篇
电工技术   13902篇
综合类   2916篇
化学工业   109578篇
金属工艺   32940篇
机械仪表   25612篇
建筑科学   18223篇
矿业工程   3839篇
能源动力   19243篇
轻工业   58702篇
水利工程   8039篇
石油天然气   12256篇
武器工业   43篇
无线电   89889篇
一般工业技术   151125篇
冶金工业   138996篇
原子能技术   13627篇
自动化技术   83512篇
  2021年   5870篇
  2020年   4322篇
  2019年   5581篇
  2018年   26106篇
  2017年   25337篇
  2016年   20511篇
  2015年   7467篇
  2014年   11335篇
  2013年   30168篇
  2012年   21581篇
  2011年   36859篇
  2010年   30659篇
  2009年   30422篇
  2008年   31595篇
  2007年   33331篇
  2006年   19368篇
  2005年   20956篇
  2004年   19208篇
  2003年   18706篇
  2002年   16785篇
  2001年   16312篇
  2000年   15347篇
  1999年   16264篇
  1998年   42514篇
  1997年   29476篇
  1996年   22719篇
  1995年   16960篇
  1994年   14720篇
  1993年   14449篇
  1992年   10261篇
  1991年   9638篇
  1990年   9430篇
  1989年   9016篇
  1988年   8364篇
  1987年   7256篇
  1986年   7189篇
  1985年   8141篇
  1984年   7517篇
  1983年   6630篇
  1982年   6193篇
  1981年   6416篇
  1980年   5997篇
  1979年   5801篇
  1978年   5577篇
  1977年   6788篇
  1976年   8957篇
  1975年   4833篇
  1974年   4549篇
  1973年   4615篇
  1972年   3813篇
排序方式: 共有10000条查询结果,搜索用时 175 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