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   468680篇
  免费   5841篇
  国内免费   1599篇
化学   249234篇
晶体学   6849篇
力学   20487篇
综合类   11篇
数学   56192篇
物理学   143347篇
  2021年   3151篇
  2020年   3566篇
  2019年   3784篇
  2018年   4416篇
  2017年   4228篇
  2016年   7141篇
  2015年   5146篇
  2014年   7471篇
  2013年   21239篇
  2012年   16300篇
  2011年   20121篇
  2010年   13053篇
  2009年   12966篇
  2008年   18294篇
  2007年   18671篇
  2006年   17999篇
  2005年   16194篇
  2004年   14806篇
  2003年   13094篇
  2002年   12824篇
  2001年   14388篇
  2000年   11108篇
  1999年   8801篇
  1998年   7081篇
  1997年   6993篇
  1996年   6834篇
  1995年   6240篇
  1994年   5910篇
  1993年   5706篇
  1992年   6374篇
  1991年   6239篇
  1990年   5968篇
  1989年   5641篇
  1988年   5906篇
  1987年   5658篇
  1986年   5342篇
  1985年   7539篇
  1984年   7779篇
  1983年   6321篇
  1982年   6827篇
  1981年   6817篇
  1980年   6487篇
  1979年   6617篇
  1978年   6793篇
  1977年   6785篇
  1976年   6737篇
  1975年   6423篇
  1974年   6320篇
  1973年   6518篇
  1972年   3947篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
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   
104.
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   
105.
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   
106.
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   
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.
Luyen  D. T. 《Mathematical Notes》2022,112(1-2):239-250
Mathematical Notes - We study the multiplicity of weak solutions to the boundary-value problem $$\begin{alignedat}{2} - M\biggl(\iint_{\mathbb R^{2N}}|u(x)-u(y)|^2 K(x-y)\,d x\,d y\biggr)\mathscr...  相似文献   
109.
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   
110.
Sargsyan  A.  Vartanyan  T. A.  Sarkisyan  D. 《Optics and Spectroscopy》2021,129(11):1173-1178
Optics and Spectroscopy - A cell with a submicron thickness was used to measure the broadening and shift of the D1 and D2 lines of Rb atoms by neon. The resolution of hypefine components...  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