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   201653篇
  免费   1468篇
  国内免费   419篇
化学   104129篇
晶体学   2814篇
力学   10259篇
综合类   10篇
数学   21829篇
物理学   64499篇
  2021年   1963篇
  2020年   2008篇
  2019年   2569篇
  2018年   3657篇
  2017年   3668篇
  2016年   4808篇
  2015年   2346篇
  2014年   4298篇
  2013年   8587篇
  2012年   6841篇
  2011年   8057篇
  2010年   6462篇
  2009年   6644篇
  2008年   7646篇
  2007年   7612篇
  2006年   6704篇
  2005年   5928篇
  2004年   5650篇
  2003年   5165篇
  2002年   5159篇
  2001年   5607篇
  2000年   4144篇
  1999年   3134篇
  1998年   2699篇
  1997年   2720篇
  1996年   2415篇
  1995年   2153篇
  1994年   2271篇
  1993年   2189篇
  1992年   2473篇
  1991年   2601篇
  1990年   2508篇
  1989年   2566篇
  1988年   2499篇
  1987年   2506篇
  1986年   2364篇
  1985年   2992篇
  1984年   3064篇
  1983年   2571篇
  1982年   2531篇
  1981年   2503篇
  1980年   2301篇
  1979年   2692篇
  1978年   2648篇
  1977年   2856篇
  1976年   2856篇
  1975年   2649篇
  1974年   2586篇
  1973年   2694篇
  1972年   2074篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
71.
72.
73.
74.
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   
75.
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   
76.
Davydov  V. V.  Myazin  N. S.  Makeev  S. S.  Dudkin  V. I. 《Technical Physics》2020,65(8):1327-1332
Technical Physics - A need to study the structure of the NMR signals detected with the aid of the modulation method is substantiated. Specific features of the detection of the NMR signals using the...  相似文献   
77.
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   
78.
79.
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   
80.
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