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   1053702篇
  免费   15038篇
  国内免费   3199篇
电工技术   19880篇
综合类   1384篇
化学工业   159328篇
金属工艺   38913篇
机械仪表   30212篇
建筑科学   26841篇
矿业工程   4253篇
能源动力   28716篇
轻工业   91728篇
水利工程   9606篇
石油天然气   15145篇
武器工业   61篇
无线电   126019篇
一般工业技术   200072篇
冶金工业   207934篇
原子能技术   19140篇
自动化技术   92707篇
  2021年   8569篇
  2020年   6463篇
  2019年   8085篇
  2018年   13399篇
  2017年   13208篇
  2016年   13972篇
  2015年   9750篇
  2014年   16276篇
  2013年   48683篇
  2012年   25953篇
  2011年   36479篇
  2010年   28980篇
  2009年   32835篇
  2008年   33971篇
  2007年   33589篇
  2006年   29738篇
  2005年   27183篇
  2004年   26396篇
  2003年   26155篇
  2002年   25102篇
  2001年   25141篇
  2000年   23693篇
  1999年   25186篇
  1998年   63090篇
  1997年   44756篇
  1996年   34932篇
  1995年   26609篇
  1994年   23693篇
  1993年   23250篇
  1992年   16901篇
  1991年   16132篇
  1990年   15837篇
  1989年   15363篇
  1988年   14596篇
  1987年   12744篇
  1986年   12743篇
  1985年   14480篇
  1984年   13261篇
  1983年   12228篇
  1982年   11420篇
  1981年   11599篇
  1980年   10923篇
  1979年   10587篇
  1978年   9997篇
  1977年   12320篇
  1976年   16329篇
  1975年   8745篇
  1974年   8365篇
  1973年   8416篇
  1972年   7028篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
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   
6.
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   
7.
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   
8.
The effect of microwave roasting parameters (300, 450 and 600 W; 5, 10 and 15 min) on acrylamide content in sorghum grain was determined using High Pressure Liquid Chromatography (HPLC)-photo diode array (PDA) detector coupled with C-18 column. Samples roasted at 300 and 450 W did not possess acrylamide, whereas 600 W (15 min) favoured formation of 2740.19 µg/kg of acrylamide, levels far exceeding the defined European Union (EU) limits. The chronic daily intake (CDI) for acrylamide through consumption of such grain flour was 3.25–9.5-fold higher to Joint FAO/WHO Expert Committee on Food Additives (JECFA) defined high exposure limits. The margin of exposure (MOE) values ranged from 4.3 to 12.76 and from 11.07 to 32.27 for neoplastic and neurological effects, respectively, demonstrating high exposure and serious health concerns associated with dietary intake of this toxicant. This study assesses the risk for the Indian population and highlights the importance of optimising process parameters for food product to minimise such exposure risks.  相似文献   
9.
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   
10.
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   
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