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   630433篇
  免费   10627篇
  国内免费   2089篇
电工技术   11615篇
综合类   695篇
化学工业   95019篇
金属工艺   24147篇
机械仪表   19545篇
建筑科学   14523篇
矿业工程   2993篇
能源动力   17421篇
轻工业   51157篇
水利工程   6268篇
石油天然气   10300篇
武器工业   44篇
无线电   75355篇
一般工业技术   125449篇
冶金工业   120904篇
原子能技术   12701篇
自动化技术   55013篇
  2022年   3976篇
  2021年   6490篇
  2020年   5036篇
  2019年   6089篇
  2018年   10441篇
  2017年   10296篇
  2016年   11000篇
  2015年   7367篇
  2014年   11560篇
  2013年   31475篇
  2012年   18064篇
  2011年   23510篇
  2010年   18966篇
  2009年   21016篇
  2008年   21785篇
  2007年   21357篇
  2006年   18688篇
  2005年   16651篇
  2004年   15755篇
  2003年   15705篇
  2002年   14735篇
  2001年   14760篇
  2000年   13798篇
  1999年   14614篇
  1998年   38746篇
  1997年   26796篇
  1996年   20496篇
  1995年   15177篇
  1994年   13336篇
  1993年   13314篇
  1992年   9339篇
  1991年   8920篇
  1990年   8759篇
  1989年   8297篇
  1988年   7972篇
  1987年   6931篇
  1986年   6728篇
  1985年   7504篇
  1984年   6859篇
  1983年   6346篇
  1982年   5852篇
  1981年   5906篇
  1980年   5571篇
  1979年   5259篇
  1978年   5099篇
  1977年   6171篇
  1976年   8604篇
  1975年   4363篇
  1974年   4152篇
  1973年   4215篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
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   
10.
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   
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