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   491012篇
  免费   6019篇
  国内免费   1772篇
化学   259965篇
晶体学   7498篇
力学   21820篇
综合类   8篇
数学   58616篇
物理学   150896篇
  2020年   3504篇
  2019年   3737篇
  2018年   4420篇
  2017年   4241篇
  2016年   7207篇
  2015年   5191篇
  2014年   7770篇
  2013年   21878篇
  2012年   16547篇
  2011年   20478篇
  2010年   13549篇
  2009年   13457篇
  2008年   18824篇
  2007年   19063篇
  2006年   18274篇
  2005年   16572篇
  2004年   15069篇
  2003年   13358篇
  2002年   13173篇
  2001年   14840篇
  2000年   11387篇
  1999年   9126篇
  1998年   7493篇
  1997年   7350篇
  1996年   7228篇
  1995年   6586篇
  1994年   6327篇
  1993年   6254篇
  1992年   6741篇
  1991年   6747篇
  1990年   6301篇
  1989年   6101篇
  1988年   6447篇
  1987年   6016篇
  1986年   5749篇
  1985年   8143篇
  1984年   8326篇
  1983年   6860篇
  1982年   7273篇
  1981年   7235篇
  1980年   6919篇
  1979年   7202篇
  1978年   7246篇
  1977年   7210篇
  1976年   7198篇
  1975年   6871篇
  1974年   6784篇
  1973年   6957篇
  1972年   4446篇
  1971年   3492篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
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   
102.
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   
103.
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   
104.
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   
105.
Algebras and Representation Theory - We introduce and study the category of twisted modules over a triangular differential graded bocs. We show that in this category idempotents split, that it...  相似文献   
106.
Annals of Operations Research - The vehicle routing problem is a traditional combinatorial problem with practical relevance for a wide range of industries. In the literature, several specificities...  相似文献   
107.
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   
108.
Popel  S. I.  Golub’  A. P. 《JETP Letters》2022,115(10):596-601
JETP Letters - One of the main features of the dusty plasma compared to the conventional plasma (without charged dust particles is anomalous dissipation that is caused by the charging of dust...  相似文献   
109.
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an...  相似文献   
110.
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   
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