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   1412511篇
  免费   29633篇
  国内免费   7776篇
化学   712079篇
晶体学   20981篇
力学   76579篇
综合类   114篇
数学   247565篇
物理学   392602篇
  2021年   13554篇
  2020年   15954篇
  2019年   16059篇
  2018年   16204篇
  2017年   14900篇
  2016年   29443篇
  2015年   21112篇
  2014年   30408篇
  2013年   74353篇
  2012年   42002篇
  2011年   43041篇
  2010年   40330篇
  2009年   42116篇
  2008年   41117篇
  2007年   38112篇
  2006年   39817篇
  2005年   34988篇
  2004年   34416篇
  2003年   31435篇
  2002年   31701篇
  2001年   30958篇
  2000年   26318篇
  1999年   23254篇
  1998年   21306篇
  1997年   21199篇
  1996年   21230篇
  1995年   19216篇
  1994年   18693篇
  1993年   18248篇
  1992年   18446篇
  1991年   18698篇
  1990年   17896篇
  1989年   17932篇
  1988年   17582篇
  1987年   17465篇
  1986年   16367篇
  1985年   22766篇
  1984年   23953篇
  1983年   20138篇
  1982年   21710篇
  1981年   20935篇
  1980年   20272篇
  1979年   20579篇
  1978年   21832篇
  1977年   21444篇
  1976年   21164篇
  1975年   19899篇
  1974年   19558篇
  1973年   20020篇
  1972年   14515篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
162.
163.
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   
164.
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   
165.
166.
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture.  相似文献   
167.
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   
168.
169.
170.
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