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   556930篇
  免费   7708篇
  国内免费   1843篇
电工技术   10245篇
综合类   446篇
化学工业   83294篇
金属工艺   23813篇
机械仪表   18318篇
建筑科学   11545篇
矿业工程   3819篇
能源动力   15775篇
轻工业   38922篇
水利工程   6524篇
石油天然气   13109篇
武器工业   34篇
无线电   64990篇
一般工业技术   115854篇
冶金工业   100948篇
原子能技术   13443篇
自动化技术   45402篇
  2022年   3899篇
  2021年   5646篇
  2020年   4346篇
  2019年   5438篇
  2018年   9167篇
  2017年   9200篇
  2016年   9768篇
  2015年   6017篇
  2014年   9986篇
  2013年   26573篇
  2012年   15537篇
  2011年   20628篇
  2010年   16517篇
  2009年   18562篇
  2008年   19027篇
  2007年   18653篇
  2006年   16409篇
  2005年   14728篇
  2004年   13902篇
  2003年   13747篇
  2002年   13014篇
  2001年   12972篇
  2000年   12132篇
  1999年   12547篇
  1998年   31869篇
  1997年   22006篇
  1996年   16999篇
  1995年   12620篇
  1994年   11120篇
  1993年   11287篇
  1992年   8273篇
  1991年   7927篇
  1990年   7752篇
  1989年   7415篇
  1988年   7213篇
  1987年   6307篇
  1986年   6208篇
  1985年   6980篇
  1984年   6434篇
  1983年   5922篇
  1982年   5375篇
  1981年   5436篇
  1980年   5169篇
  1979年   5090篇
  1978年   5106篇
  1977年   5667篇
  1976年   7100篇
  1975年   4493篇
  1974年   4245篇
  1973年   4381篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a...  相似文献   
3.
Koroteev  A. S. 《Atomic Energy》2021,130(4):202-208
Atomic Energy - The history and direction of further development of space nuclear energetics are examined. The functional diagram and principle of operation of a promising, powerful,...  相似文献   
4.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
5.
6.
7.
8.
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   
9.
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   
10.
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   
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