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   391908篇
  免费   5685篇
  国内免费   1152篇
电工技术   7429篇
综合类   306篇
化学工业   58016篇
金属工艺   17003篇
机械仪表   12121篇
建筑科学   8375篇
矿业工程   2815篇
能源动力   9012篇
轻工业   27956篇
水利工程   4450篇
石油天然气   9539篇
武器工业   29篇
无线电   46368篇
一般工业技术   81465篇
冶金工业   73932篇
原子能技术   9620篇
自动化技术   30309篇
  2021年   3449篇
  2020年   2672篇
  2019年   3350篇
  2018年   5976篇
  2017年   6028篇
  2016年   6407篇
  2015年   4053篇
  2014年   6655篇
  2013年   17065篇
  2012年   10256篇
  2011年   13414篇
  2010年   10898篇
  2009年   12212篇
  2008年   12750篇
  2007年   12645篇
  2006年   11037篇
  2005年   10156篇
  2004年   9604篇
  2003年   9401篇
  2002年   9074篇
  2001年   9330篇
  2000年   8751篇
  1999年   9140篇
  1998年   23673篇
  1997年   16218篇
  1996年   12651篇
  1995年   9373篇
  1994年   8159篇
  1993年   8308篇
  1992年   6014篇
  1991年   5917篇
  1990年   5761篇
  1989年   5540篇
  1988年   5304篇
  1987年   4502篇
  1986年   4597篇
  1985年   5245篇
  1984年   4819篇
  1983年   4382篇
  1982年   4010篇
  1981年   4142篇
  1980年   3958篇
  1979年   3862篇
  1978年   3877篇
  1977年   4306篇
  1976年   5308篇
  1975年   3453篇
  1974年   3286篇
  1973年   3322篇
  1972年   2908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.
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   
6.
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   
7.
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   
8.
Multimedia Tools and Applications - Endometriosis is a common gynecologic condition typically treated via laparoscopic surgery. Its visual versatility makes it hard to identify for non-specialized...  相似文献   
9.
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   
10.
Forschung im Ingenieurwesen - Das Arbeitsmittel in Wärmepumpen unterliegt einer Vielzahl von Anforderungen, welche für einen effizienten und sicheren Betrieb eingehalten werden...  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