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   479035篇
  免费   6947篇
  国内免费   1480篇
化学   259331篇
晶体学   5905篇
力学   19928篇
综合类   18篇
数学   59059篇
物理学   143221篇
  2021年   4165篇
  2020年   4753篇
  2019年   5032篇
  2018年   6429篇
  2017年   6272篇
  2016年   9959篇
  2015年   6525篇
  2014年   9606篇
  2013年   22699篇
  2012年   17791篇
  2011年   21695篇
  2010年   14969篇
  2009年   14668篇
  2008年   19842篇
  2007年   19689篇
  2006年   18285篇
  2005年   16452篇
  2004年   15197篇
  2003年   13281篇
  2002年   12955篇
  2001年   14163篇
  2000年   10753篇
  1999年   8399篇
  1998年   7054篇
  1997年   6835篇
  1996年   6724篇
  1995年   5967篇
  1994年   5974篇
  1993年   5763篇
  1992年   6401篇
  1991年   6223篇
  1990年   5941篇
  1989年   5780篇
  1988年   5803篇
  1987年   5679篇
  1986年   5353篇
  1985年   7049篇
  1984年   7212篇
  1983年   5673篇
  1982年   5902篇
  1981年   5868篇
  1980年   5430篇
  1979年   5846篇
  1978年   5975篇
  1977年   5872篇
  1976年   5819篇
  1975年   5361篇
  1974年   5302篇
  1973年   5253篇
  1972年   3671篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Journal of Thermal Analysis and Calorimetry - In the present study, numerical simulations have been carried out on thermal characteristics and second-law analysis of turbulent Cu–H2O...  相似文献   
122.
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course.  相似文献   
123.
124.
125.
126.
127.
128.
129.
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   
130.
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   
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