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   517334篇
  免费   3273篇
  国内免费   966篇
化学   242857篇
晶体学   7361篇
力学   28738篇
综合类   20篇
数学   80800篇
物理学   161797篇
  2020年   4657篇
  2019年   5533篇
  2018年   12669篇
  2017年   13083篇
  2016年   13056篇
  2015年   5795篇
  2014年   9585篇
  2013年   19495篇
  2012年   17949篇
  2011年   25368篇
  2010年   18236篇
  2009年   18461篇
  2008年   23662篇
  2007年   25674篇
  2006年   15946篇
  2005年   16991篇
  2004年   14486篇
  2003年   13912篇
  2002年   12939篇
  2001年   12143篇
  2000年   10013篇
  1999年   7284篇
  1998年   6648篇
  1997年   6553篇
  1996年   6114篇
  1995年   5234篇
  1994年   5344篇
  1993年   5320篇
  1992年   5510篇
  1991年   5894篇
  1990年   5766篇
  1989年   5800篇
  1988年   5513篇
  1987年   5526篇
  1986年   5236篇
  1985年   6382篇
  1984年   6745篇
  1983年   5630篇
  1982年   6030篇
  1981年   5614篇
  1980年   5253篇
  1979年   5874篇
  1978年   6127篇
  1977年   6182篇
  1976年   6256篇
  1975年   5866篇
  1974年   5734篇
  1973年   6051篇
  1972年   4665篇
  1971年   4182篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Russian Journal of General Chemistry - A method was developed for the synthesis of an organofluorine derivative of β-D-ribofuranoside. Biological tests revealed high insecticidal activity and...  相似文献   
142.
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   
143.
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   
144.
ABSTRACT

By applying the geometric models and the theoretical equation, the surface tension, the molar volume and the density were studied. The empirical calculations were carried out in temperature range 623?K?≤?T?≤?1123?K. Only few thermophysical properties were estimated for eight quinary alloys: Sn3.55Ag0.5Cu3Bi3Sb, Sn3.48Ag0.5Cu3Bi5Sb, Sn3.48 Ag0.5Cu5Bi3Sb, Sn3.40 Ag0.5Cu5Bi5Sb, Sn3.53Ag1Cu3Bi3Sb, Sn3.46Ag1Cu3Bi5Sb, Sn3.46Ag1Cu5Bi3Sb, Sn3.38Ag1Cu5Bi5Sb. The results show that surface tension and density have a linear appearance for all temperatures. We have also studied the influence of the composition and temperature in the studied alloys. The obtained theoretical results are compared with the experimental ones and with the conventional Pb–Sn welds.  相似文献   
145.
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   
146.
147.
148.
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   
149.
150.
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