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   845800篇
  免费   11473篇
  国内免费   2549篇
电工技术   15847篇
综合类   1052篇
化学工业   125218篇
金属工艺   33102篇
机械仪表   27784篇
建筑科学   20263篇
矿业工程   3744篇
能源动力   22689篇
轻工业   70630篇
水利工程   8157篇
石油天然气   12668篇
武器工业   29篇
无线电   102118篇
一般工业技术   164900篇
冶金工业   156841篇
原子能技术   15504篇
自动化技术   79276篇
  2021年   6643篇
  2020年   5068篇
  2019年   6316篇
  2018年   15699篇
  2017年   15892篇
  2016年   14181篇
  2015年   7861篇
  2014年   12559篇
  2013年   38499篇
  2012年   22283篇
  2011年   33791篇
  2010年   27702篇
  2009年   29832篇
  2008年   30683篇
  2007年   31744篇
  2006年   23569篇
  2005年   23687篇
  2004年   21804篇
  2003年   21319篇
  2002年   19711篇
  2001年   19527篇
  2000年   18368篇
  1999年   19496篇
  1998年   48439篇
  1997年   34042篇
  1996年   26245篇
  1995年   19872篇
  1994年   17602篇
  1993年   17434篇
  1992年   12539篇
  1991年   11904篇
  1990年   11720篇
  1989年   11267篇
  1988年   10799篇
  1987年   9295篇
  1986年   9183篇
  1985年   10734篇
  1984年   9732篇
  1983年   8912篇
  1982年   8176篇
  1981年   8391篇
  1980年   7828篇
  1979年   7515篇
  1978年   7192篇
  1977年   8530篇
  1976年   11029篇
  1975年   6291篇
  1974年   5945篇
  1973年   6035篇
  1972年   4931篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Materials Science -  相似文献   
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.
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   
8.
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   
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.
Engineering new glass compositions have experienced a sturdy tendency to move forward from (educated) trial-and-error to data- and simulation-driven strategies. In this work, we developed a computer program that combines data-driven predictive models (in this case, neural networks) with a genetic algorithm to design glass compositions with desired combinations of properties. First, we induced predictive models for the glass transition temperature (Tg) using a dataset of 45,302 compositions with 39 different chemical elements, and for the refractive index (nd) using a dataset of 41,225 compositions with 38 different chemical elements. Then, we searched for relevant glass compositions using a genetic algorithm informed by a design trend of glasses having high nd (1.7 or more) and low Tg (500 °C or less). Two candidate compositions suggested by the combined algorithms were selected and produced in the laboratory. These compositions are significantly different from those in the datasets used to induce the predictive models, showing that the used method is indeed capable of exploration. Both glasses met the constraints of the work, which supports the proposed framework. Therefore, this new tool can be immediately used for accelerating the design of new glasses. These results are a stepping stone in the pathway of machine learning-guided design of novel glasses.  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