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   291761篇
  免费   2981篇
  国内免费   733篇
电工技术   5386篇
综合类   288篇
化学工业   42768篇
金属工艺   17056篇
机械仪表   12140篇
建筑科学   5674篇
矿业工程   2816篇
能源动力   5739篇
轻工业   15773篇
水利工程   4034篇
石油天然气   8794篇
武器工业   23篇
无线电   29831篇
一般工业技术   65671篇
冶金工业   45050篇
原子能技术   7796篇
自动化技术   26636篇
  2021年   2243篇
  2019年   2182篇
  2018年   11135篇
  2017年   11590篇
  2016年   8460篇
  2015年   2879篇
  2014年   4202篇
  2013年   9634篇
  2012年   8420篇
  2011年   15099篇
  2010年   13339篇
  2009年   12906篇
  2008年   13073篇
  2007年   14716篇
  2006年   6229篇
  2005年   8788篇
  2004年   6940篇
  2003年   6647篇
  2002年   5624篇
  2001年   5156篇
  2000年   4891篇
  1999年   4786篇
  1998年   12239篇
  1997年   8519篇
  1996年   6490篇
  1995年   4818篇
  1994年   4219篇
  1993年   4469篇
  1992年   3337篇
  1991年   3325篇
  1990年   3217篇
  1989年   3178篇
  1988年   3146篇
  1987年   2764篇
  1986年   2796篇
  1985年   3126篇
  1984年   2894篇
  1983年   2751篇
  1982年   2463篇
  1981年   2474篇
  1980年   2544篇
  1979年   2519篇
  1978年   2522篇
  1977年   2756篇
  1976年   3244篇
  1975年   2305篇
  1974年   2175篇
  1973年   2276篇
  1972年   2024篇
  1971年   1826篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
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   
4.
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   
5.
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   
6.
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   
7.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
8.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  相似文献   
9.
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability.  相似文献   
10.
Automation and Remote Control - A linear-quadratic positional differential game of three persons is considered. Coefficient criteria are established under which there is no Nash equilibrium...  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