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   661525篇
  免费   9999篇
  国内免费   1929篇
电工技术   12316篇
综合类   635篇
化学工业   97854篇
金属工艺   25116篇
机械仪表   18978篇
建筑科学   15845篇
矿业工程   2863篇
能源动力   17847篇
轻工业   56603篇
水利工程   6368篇
石油天然气   11166篇
武器工业   43篇
无线电   78129篇
一般工业技术   128167篇
冶金工业   133507篇
原子能技术   12856篇
自动化技术   55160篇
  2021年   5790篇
  2020年   4223篇
  2019年   5489篇
  2018年   9334篇
  2017年   9113篇
  2016年   9552篇
  2015年   6692篇
  2014年   11142篇
  2013年   30120篇
  2012年   17660篇
  2011年   24337篇
  2010年   19304篇
  2009年   21711篇
  2008年   22341篇
  2007年   22028篇
  2006年   19327篇
  2005年   17824篇
  2004年   17193篇
  2003年   16860篇
  2002年   16031篇
  2001年   16226篇
  2000年   15166篇
  1999年   16255篇
  1998年   42429篇
  1997年   29469篇
  1996年   22684篇
  1995年   16931篇
  1994年   14710篇
  1993年   14421篇
  1992年   10252篇
  1991年   9738篇
  1990年   9513篇
  1989年   9181篇
  1988年   8488篇
  1987年   7386篇
  1986年   7306篇
  1985年   8288篇
  1984年   7621篇
  1983年   6727篇
  1982年   6303篇
  1981年   6505篇
  1980年   6080篇
  1979年   5880篇
  1978年   5658篇
  1977年   6852篇
  1976年   9032篇
  1975年   4895篇
  1974年   4620篇
  1973年   4676篇
  1972年   3852篇
排序方式: 共有10000条查询结果,搜索用时 15 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