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   414286篇
  免费   4779篇
  国内免费   1520篇
化学   206633篇
晶体学   5948篇
力学   19646篇
综合类   52篇
数学   59789篇
物理学   128517篇
  2020年   2113篇
  2019年   2055篇
  2018年   11075篇
  2017年   11957篇
  2016年   8045篇
  2015年   4277篇
  2014年   4718篇
  2013年   14307篇
  2012年   15225篇
  2011年   25893篇
  2010年   15705篇
  2009年   15630篇
  2008年   22912篇
  2007年   26465篇
  2006年   12536篇
  2005年   18375篇
  2004年   13658篇
  2003年   12240篇
  2002年   10112篇
  2001年   10319篇
  2000年   8030篇
  1999年   6214篇
  1998年   4992篇
  1997年   4799篇
  1996年   4961篇
  1995年   4499篇
  1994年   4237篇
  1993年   4051篇
  1992年   4538篇
  1991年   4392篇
  1990年   4110篇
  1989年   3928篇
  1988年   4224篇
  1987年   3891篇
  1986年   3758篇
  1985年   5408篇
  1984年   5492篇
  1983年   4460篇
  1982年   4835篇
  1981年   4871篇
  1980年   4627篇
  1979年   4756篇
  1978年   4763篇
  1977年   4672篇
  1976年   4653篇
  1975年   4555篇
  1974年   4400篇
  1973年   4603篇
  1972年   2594篇
  1971年   1896篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
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   
72.
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   
73.
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   
74.
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   
75.
Journal of Solid State Electrochemistry - Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct...  相似文献   
76.
Methodology and Computing in Applied Probability - The problem of optimally controlling one-dimensional diffusion processes until they enter a given stopping set is extended to include Markov...  相似文献   
77.
78.
Ding  Q.  Yao  M.  Wu  Sh.  Zeng  M.  Xue  N.  Wu  D.  Xu  J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the...  相似文献   
79.
Xu  H. J.  Zhang  Q. G.  Debenest  G. 《Transport in Porous Media》2021,140(3):625-627
Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the...  相似文献   
80.
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