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   313573篇
  免费   4291篇
  国内免费   1080篇
化学   170406篇
晶体学   4440篇
力学   13031篇
综合类   7篇
数学   36272篇
物理学   94788篇
  2020年   1985篇
  2019年   1956篇
  2018年   1966篇
  2017年   1875篇
  2016年   3859篇
  2015年   3235篇
  2014年   4428篇
  2013年   13979篇
  2012年   10735篇
  2011年   13370篇
  2010年   8274篇
  2009年   8260篇
  2008年   12350篇
  2007年   12586篇
  2006年   12223篇
  2005年   11169篇
  2004年   10042篇
  2003年   8856篇
  2002年   8704篇
  2001年   10109篇
  2000年   7711篇
  1999年   6117篇
  1998年   4895篇
  1997年   4733篇
  1996年   4774篇
  1995年   4364篇
  1994年   4115篇
  1993年   3941篇
  1992年   4433篇
  1991年   4293篇
  1990年   4011篇
  1989年   3830篇
  1988年   4122篇
  1987年   3784篇
  1986年   3677篇
  1985年   5317篇
  1984年   5397篇
  1983年   4379篇
  1982年   4755篇
  1981年   4796篇
  1980年   4545篇
  1979年   4665篇
  1978年   4666篇
  1977年   4647篇
  1976年   4597篇
  1975年   4509篇
  1974年   4356篇
  1973年   4524篇
  1972年   2569篇
  1971年   1840篇
排序方式: 共有10000条查询结果,搜索用时 15 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