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   426903篇
  免费   6497篇
  国内免费   2426篇
化学   215445篇
晶体学   6133篇
力学   20322篇
综合类   74篇
数学   61369篇
物理学   132483篇
  2021年   2232篇
  2020年   2639篇
  2019年   2523篇
  2018年   11460篇
  2017年   12256篇
  2016年   8574篇
  2015年   4873篇
  2014年   5288篇
  2013年   15213篇
  2012年   16241篇
  2011年   26818篇
  2010年   16318篇
  2009年   16280篇
  2008年   23666篇
  2007年   27089篇
  2006年   13133篇
  2005年   18960篇
  2004年   14085篇
  2003年   12605篇
  2002年   10468篇
  2001年   10576篇
  2000年   8284篇
  1999年   6475篇
  1998年   5173篇
  1997年   4967篇
  1996年   5164篇
  1995年   4657篇
  1994年   4377篇
  1993年   4170篇
  1992年   4633篇
  1991年   4490篇
  1990年   4185篇
  1989年   4004篇
  1988年   4300篇
  1987年   3952篇
  1986年   3812篇
  1985年   5495篇
  1984年   5569篇
  1983年   4505篇
  1982年   4878篇
  1981年   4921篇
  1980年   4675篇
  1979年   4792篇
  1978年   4803篇
  1977年   4706篇
  1976年   4688篇
  1975年   4590篇
  1974年   4435篇
  1973年   4622篇
  1972年   2605篇
排序方式: 共有10000条查询结果,搜索用时 173 毫秒
71.
72.
73.
74.
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   
75.
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   
76.
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   
77.
For the orthosymplectic Lie superalgebra ◂⋅▸OSP(2,2), we choose a set of basis matrices. A linear combination of those basis matrices presents a spatial spectral matrix. The compatible condition of the spatial part and the corresponding temporal parts of the spectral problem leads to a generalized super AKNS (GSAKNS) hierarchy. By making use of the supertrace identity, the obtained GSAKNS hierarchy can be written as the super bi-Hamiltonian structures.  相似文献   
78.
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   
79.
80.
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field.  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