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   450791篇
  免费   5934篇
  国内免费   1584篇
化学   248779篇
晶体学   5050篇
力学   18916篇
综合类   11篇
数学   51533篇
物理学   134020篇
  2018年   2974篇
  2016年   5681篇
  2015年   4524篇
  2014年   6253篇
  2013年   19929篇
  2012年   14372篇
  2011年   17995篇
  2010年   11465篇
  2009年   11329篇
  2008年   16528篇
  2007年   16881篇
  2006年   16216篇
  2005年   14813篇
  2004年   13399篇
  2003年   11881篇
  2002年   11693篇
  2001年   13830篇
  2000年   10612篇
  1999年   8503篇
  1998年   6789篇
  1997年   6509篇
  1996年   6040篇
  1995年   5903篇
  1994年   5660篇
  1993年   5355篇
  1992年   6212篇
  1991年   5945篇
  1990年   5637篇
  1989年   5540篇
  1988年   5749篇
  1987年   5479篇
  1986年   5255篇
  1985年   7520篇
  1984年   7648篇
  1983年   6214篇
  1982年   6654篇
  1981年   6697篇
  1980年   6308篇
  1979年   6631篇
  1978年   6827篇
  1977年   6703篇
  1976年   6630篇
  1975年   6386篇
  1974年   6204篇
  1973年   6400篇
  1972年   3848篇
  1971年   2969篇
  1968年   3369篇
  1967年   3274篇
  1966年   2990篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
86.
87.
In the last decade, catalytic chemical vapor deposition (CVD) has been intensively explored for the growth of single-layer graphene (SLG). Despite the scattering of guidelines and procedures, variables such as the surface texture/chemistry of catalyst metal foils, carbon feedstock, and growth process parameters have been well-scrutinized. Still, questions remain on how best to standardize the growth procedure. The possible correlation of procedures between different CVD setups is an example. Here, two thermal CVD reactors were explored to grow graphene on Cu foil. The design of these setups was entirely distinct, one being a “showerhead” cold-wall type, whereas the other represented the popular “tubular” hot-wall type. Upon standardizing the Cu foil surface, it was possible to develop a procedure for cm2-scale SLG growth that differed only by the carrier gas flow rate used in the two reactors.  相似文献   
88.
Journal of Solid State Electrochemistry - In this work, the use of neodymium electrodes as a basis for the immobilization of magnetite nanoparticles has been carried out. The sensitivity and...  相似文献   
89.
The influenza virus is a global threat to human health causing unpredictable yet recurring pandemics, the last four emerging over the course of a hundred years. As our knowledge of influenza virus evolution, distribution, and transmission has increased, paths to pandemic preparedness have become apparent. In the 1950s, the World Health Organization (WHO) established a global influenza surveillance network that is now composed of institutions in 122 member states. This and other surveillance networks monitor circulating influenza strains in humans and animal reservoirs and are primed to detect influenza strains with pandemic potential. Both the United States Centers for Disease Control and Prevention and the WHO have also developed pandemic risk assessment tools that evaluate specific aspects of emerging influenza strains to develop a systematic process of determining research and funding priorities according to the risk of emergence and potential impact. Here, we review the history of influenza pandemic preparedness and the current state of preparedness, and we propose additional measures for improvement. We also comment on the intersection between the influenza pandemic preparedness network and the current SARS-CoV-2 crisis. We must continually evaluate and revise our risk assessment and pandemic preparedness plans and incorporate new information gathered from research and global crises.Subject terms: Influenza virus, Infectious diseases  相似文献   
90.
High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE.  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