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   319628篇
  免费   4643篇
  国内免费   1111篇
化学   174827篇
晶体学   4497篇
力学   13186篇
综合类   20篇
数学   37001篇
物理学   95851篇
  2020年   2122篇
  2019年   2077篇
  2018年   2102篇
  2017年   2000篇
  2016年   4148篇
  2015年   3452篇
  2014年   4652篇
  2013年   14422篇
  2012年   11177篇
  2011年   13855篇
  2010年   8503篇
  2009年   8450篇
  2008年   12767篇
  2007年   12967篇
  2006年   12552篇
  2005年   11472篇
  2004年   10263篇
  2003年   9070篇
  2002年   8916篇
  2001年   10200篇
  2000年   7814篇
  1999年   6182篇
  1998年   4941篇
  1997年   4779篇
  1996年   4842篇
  1995年   4411篇
  1994年   4158篇
  1993年   4020篇
  1992年   4491篇
  1991年   4328篇
  1990年   4037篇
  1989年   3854篇
  1988年   4135篇
  1987年   3806篇
  1986年   3691篇
  1985年   5356篇
  1984年   5422篇
  1983年   4399篇
  1982年   4771篇
  1981年   4806篇
  1980年   4557篇
  1979年   4669篇
  1978年   4675篇
  1977年   4653篇
  1976年   4605篇
  1975年   4520篇
  1974年   4366篇
  1973年   4526篇
  1972年   2572篇
  1971年   1882篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
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   
62.
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   
63.
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   
64.
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   
65.
The metallacarborane [3,3′‐Co(1,2‐closo‐C2B9H11)2]? has been synthesized. This species allows the formation of redox couples in which both partners are negatively charged. The E1/2 potential can be tuned by adjusting the nature and number of substituents on B and C. The octaiodinated species [3,3′‐Co(1,2‐closo‐C2B9H7I4)2]? is the most favorable, as it is isolatable and stable in air. A DFT study on stability and redox potentials of complexes has been performed.  相似文献   
66.
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   
67.
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   
68.
69.
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   
70.
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   
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