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   661668篇
  免费   11539篇
  国内免费   3065篇
电工技术   12664篇
技术理论   5篇
综合类   2066篇
化学工业   100845篇
金属工艺   25536篇
机械仪表   20648篇
建筑科学   15280篇
矿业工程   3999篇
能源动力   16640篇
轻工业   53908篇
水利工程   7165篇
石油天然气   12361篇
武器工业   268篇
无线电   72595篇
一般工业技术   126881篇
冶金工业   132762篇
原子能技术   13278篇
自动化技术   59371篇
  2021年   6444篇
  2020年   4738篇
  2019年   5947篇
  2018年   10565篇
  2017年   10605篇
  2016年   11605篇
  2015年   8000篇
  2014年   11802篇
  2013年   31038篇
  2012年   20310篇
  2011年   26389篇
  2010年   20082篇
  2009年   21942篇
  2008年   22681篇
  2007年   22514篇
  2006年   19918篇
  2005年   20743篇
  2004年   18624篇
  2003年   17494篇
  2002年   15661篇
  2001年   15422篇
  2000年   14140篇
  1999年   14700篇
  1998年   39507篇
  1997年   27524篇
  1996年   20839篇
  1995年   15227篇
  1994年   13388篇
  1993年   13442篇
  1992年   9395篇
  1991年   8879篇
  1990年   8924篇
  1989年   8635篇
  1988年   8150篇
  1987年   7090篇
  1986年   6996篇
  1985年   7782篇
  1984年   7202篇
  1983年   6575篇
  1982年   6021篇
  1981年   6336篇
  1980年   5843篇
  1979年   5774篇
  1978年   5654篇
  1977年   6768篇
  1976年   9410篇
  1975年   4940篇
  1974年   4582篇
  1973年   4680篇
  1972年   3904篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
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.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
10.
While protein medications are promising for treatment of cancer and autoimmune diseases, challenges persist in terms of development and injection stability of high-concentration formulations. Here, the extensional flow properties of protein-excipient solutions are examined via dripping-onto-substrate extensional rheology, using a model ovalbumin (OVA) protein and biocompatible excipients polysorbate 20 (PS20) and 80 (PS80). Despite similar PS structures, differences in extensional flow are observed based on PS identity in two regimes: at moderate total concentrations where surface tension differences drive changes in extensional flow behavior, and at small PS:OVA ratios, which impact the onset of weakly elastic flow behavior. Undesirable elasticity is observed in ultra-concentrated formulations, independent of PS identity; higher PS contents are required to observe these effects than in analogous polymeric excipient solutions. These studies reveal novel extensional flow behaviors in protein-excipient solutions, and provide a straightforward methodology for assessing the extensional flow stability of new protein-excipient formulations.  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