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   466025篇
  免费   3903篇
  国内免费   1625篇
化学   229897篇
晶体学   6889篇
力学   23920篇
综合类   63篇
数学   63330篇
物理学   147454篇
  2020年   4649篇
  2019年   5402篇
  2018年   7686篇
  2017年   7873篇
  2016年   10314篇
  2015年   5360篇
  2014年   9356篇
  2013年   19049篇
  2012年   16037篇
  2011年   19171篇
  2010年   14865篇
  2009年   14856篇
  2008年   18234篇
  2007年   18045篇
  2006年   16532篇
  2005年   14680篇
  2004年   13674篇
  2003年   12407篇
  2002年   12544篇
  2001年   12922篇
  2000年   10033篇
  1999年   7391篇
  1998年   6606篇
  1997年   6474篇
  1996年   6092篇
  1995年   5353篇
  1994年   5506篇
  1993年   5389篇
  1992年   5637篇
  1991年   5997篇
  1990年   5805篇
  1989年   5720篇
  1988年   5457篇
  1987年   5399篇
  1986年   5177篇
  1985年   6443篇
  1984年   6693篇
  1983年   5671篇
  1982年   6011篇
  1981年   5575篇
  1980年   5153篇
  1979年   5767篇
  1978年   5972篇
  1977年   6140篇
  1976年   6258篇
  1975年   5798篇
  1974年   5736篇
  1973年   5944篇
  1972年   4827篇
  1971年   4161篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
122.
The thermal and dielectric behaviors of poly(vinylidene fluoride-trifluoroethylene) copolymers near the ferroelectric-to-paraelectric phase transition are investigated for samples with 20, 25, 30, and 40 mol% trifluoroethylene (TrFE). The data suggest that the transition becomes continuous for a particular composition near 50 mol% TrFE. Experimental data are sensitive to thermal history (kinetics of crystallization, and kinetics and cycling over the structural transition). It is found that several anomalies are present at the structural change, and in particular the 30 mol% TrFE sample shows the most marked anomalies. These phenomena can be attributed to defects, but another possibility would be the existence of an intemediate supplementary phase. Both hypotheses are discussed.  相似文献   
123.
Proceedings of the Steklov Institute of Mathematics -  相似文献   
124.
125.
126.
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants.  相似文献   
127.
A standard model Lagrangian is constructed making the pseudo-Finsleroid generalization of the Yang-Mills field equation by the conformal method. The Higgs field potential is suggested that ensures generation of particle masses caused by the spontaneous symmetry breaking. After transition to the conformal coordinates, the expressions obtained assume the standard form that in many cases allows the results of pseudo-Euclidean theory to be used in calculations of the Feynman diagrams. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–51, April, 2006.  相似文献   
128.
129.
In the past 6 years changes have occurred in GCE A-levels. Inparticular, there have been several major changes in A-levelMathematics courses. As engineering students are usually requiredto have studied A-level Mathematics, or its equivalent, thesechanges have had an effect on their prior mathematical knowledge.Moreover, engineering students traditionally obtained a goodgrounding in mechanics as part of their A-level Mathematicsqualification. However, mechanics, which was once included inthe core syllabus, is now optional. This article investigatesthe current availability and uptake of mechanics modules withinA-level Mathematics courses in schools. Comparisons are drawnbetween these results and results of a survey of schools in2004 and surveys of first year engineering students conductedin 2004 and 2005. It is found that there is a decline in theavailability of mechanics modules and the uptake of more thanone mechanics module has also decreased. The implications ofthese findings for engineering educators are discussed.  相似文献   
130.
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied.  相似文献   
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