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   523946篇
  免费   6272篇
  国内免费   1956篇
化学   271953篇
晶体学   5957篇
力学   25185篇
综合类   11篇
数学   81187篇
物理学   147881篇
  2018年   12832篇
  2017年   12571篇
  2016年   11371篇
  2015年   5311篇
  2014年   6501篇
  2013年   20169篇
  2012年   17802篇
  2011年   27577篇
  2010年   16623篇
  2009年   16793篇
  2008年   22476篇
  2007年   24777篇
  2006年   16383篇
  2005年   15977篇
  2004年   14784篇
  2003年   13684篇
  2002年   12575篇
  2001年   14016篇
  2000年   10835篇
  1999年   8609篇
  1998年   6928篇
  1997年   6767篇
  1996年   6873篇
  1995年   6231篇
  1994年   5939篇
  1993年   5648篇
  1992年   6277篇
  1991年   6006篇
  1990年   5691篇
  1989年   5604篇
  1988年   5809篇
  1987年   5538篇
  1986年   5312篇
  1985年   7571篇
  1984年   7690篇
  1983年   6253篇
  1982年   6694篇
  1981年   6741篇
  1980年   6359篇
  1979年   6675篇
  1978年   6866篇
  1977年   6724篇
  1976年   6652篇
  1975年   6406篇
  1974年   6220篇
  1973年   6430篇
  1972年   3864篇
  1968年   3379篇
  1967年   3286篇
  1966年   3007篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
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   
94.
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   
95.
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   
96.
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   
97.
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   
98.
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   
99.
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed.  相似文献   
100.
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