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   1338768篇
  免费   29123篇
  国内免费   7678篇
化学   659492篇
晶体学   20824篇
力学   75585篇
综合类   102篇
数学   244532篇
物理学   375034篇
  2021年   13464篇
  2020年   15904篇
  2019年   16025篇
  2018年   15155篇
  2017年   13844篇
  2016年   28901篇
  2015年   21075篇
  2014年   30407篇
  2013年   74301篇
  2012年   37815篇
  2011年   35967篇
  2010年   38655篇
  2009年   41249篇
  2008年   35276篇
  2007年   31491篇
  2006年   34253篇
  2005年   29312篇
  2004年   29602篇
  2003年   27834篇
  2002年   28320篇
  2001年   26139篇
  2000年   23324篇
  1999年   21812篇
  1998年   20790篇
  1997年   20784篇
  1996年   21006篇
  1995年   19072篇
  1994年   18548篇
  1993年   18062篇
  1992年   17675篇
  1991年   18045篇
  1990年   17242篇
  1989年   17357篇
  1988年   16890篇
  1987年   16936篇
  1986年   15766篇
  1985年   22251篇
  1984年   23597篇
  1983年   19843篇
  1982年   21572篇
  1981年   20820篇
  1980年   20143篇
  1979年   20209篇
  1978年   21618篇
  1977年   21182篇
  1976年   20829篇
  1975年   19520篇
  1974年   19145篇
  1973年   19617篇
  1972年   14116篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
153.
154.
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   
155.
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   
156.
157.
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   
158.
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   
159.
160.
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