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   313808篇
  免费   4317篇
  国内免费   1094篇
化学   170564篇
晶体学   4361篇
力学   13078篇
综合类   7篇
数学   36344篇
物理学   94865篇
  2020年   2009篇
  2019年   1984篇
  2018年   1993篇
  2017年   1908篇
  2016年   3896篇
  2015年   3256篇
  2014年   4462篇
  2013年   14047篇
  2012年   10785篇
  2011年   13410篇
  2010年   8309篇
  2009年   8277篇
  2008年   12347篇
  2007年   12591篇
  2006年   12222篇
  2005年   11157篇
  2004年   10036篇
  2003年   8850篇
  2002年   8701篇
  2001年   10113篇
  2000年   7711篇
  1999年   6115篇
  1998年   4893篇
  1997年   4734篇
  1996年   4774篇
  1995年   4364篇
  1994年   4114篇
  1993年   3942篇
  1992年   4431篇
  1991年   4293篇
  1990年   4011篇
  1989年   3830篇
  1988年   4121篇
  1987年   3785篇
  1986年   3677篇
  1985年   5319篇
  1984年   5396篇
  1983年   4378篇
  1982年   4754篇
  1981年   4793篇
  1980年   4548篇
  1979年   4665篇
  1978年   4665篇
  1977年   4649篇
  1976年   4599篇
  1975年   4511篇
  1974年   4324篇
  1973年   4486篇
  1972年   2533篇
  1971年   1839篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
53.
54.
55.
56.
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   
57.
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   
58.
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   
59.
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   
60.
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   
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