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   296704篇
  免费   1825篇
  国内免费   454篇
化学   136265篇
晶体学   4403篇
力学   17003篇
综合类   10篇
数学   46544篇
物理学   94758篇
  2021年   2066篇
  2020年   2171篇
  2019年   2770篇
  2018年   11297篇
  2017年   11989篇
  2016年   8828篇
  2015年   3380篇
  2014年   4848篇
  2013年   9495篇
  2012年   11149篇
  2011年   19501篇
  2010年   12989篇
  2009年   13257篇
  2008年   17464篇
  2007年   20487篇
  2006年   7225篇
  2005年   11748篇
  2004年   8702篇
  2003年   8428篇
  2002年   6650篇
  2001年   5890篇
  2000年   4576篇
  1999年   3257篇
  1998年   2828篇
  1997年   2839篇
  1996年   2788篇
  1995年   2383篇
  1994年   2467篇
  1993年   2352篇
  1992年   2656篇
  1991年   2787篇
  1990年   2683篇
  1989年   2768篇
  1988年   2688篇
  1987年   2709篇
  1986年   2558篇
  1985年   3213篇
  1984年   3295篇
  1983年   2747篇
  1982年   2701篇
  1981年   2679篇
  1980年   2470篇
  1979年   2872篇
  1978年   2832篇
  1977年   2942篇
  1976年   2973篇
  1975年   2759篇
  1974年   2693篇
  1973年   2839篇
  1972年   2137篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
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   
85.
Journal of Analytical Chemistry - Studies on the separation of the Se and Te trace components from Co, Ni, Cu, Fe, Cr, Mo, and W macrocomponents for their determination by inductively coupled...  相似文献   
86.
ABSTRACT

The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti.  相似文献   
87.
88.
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field.  相似文献   
89.
Journal of Experimental and Theoretical Physics - The nature of the training effect in exchange-biased compounds is studied. This effect consists in a decrease in the exchange bias field (HEB)...  相似文献   
90.
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