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   182850篇
  免费   2128篇
  国内免费   557篇
化学   101462篇
晶体学   2329篇
力学   7137篇
综合类   13篇
数学   20238篇
物理学   54356篇
  2021年   1519篇
  2020年   1577篇
  2019年   1723篇
  2018年   2017篇
  2017年   1974篇
  2016年   3384篇
  2015年   2376篇
  2014年   3348篇
  2013年   8061篇
  2012年   6627篇
  2011年   8246篇
  2010年   5565篇
  2009年   5492篇
  2008年   7390篇
  2007年   7327篇
  2006年   6909篇
  2005年   6321篇
  2004年   5501篇
  2003年   4778篇
  2002年   4695篇
  2001年   4888篇
  2000年   3822篇
  1999年   3023篇
  1998年   2587篇
  1997年   2519篇
  1996年   2409篇
  1995年   2211篇
  1994年   2215篇
  1993年   2040篇
  1992年   2276篇
  1991年   2357篇
  1990年   2153篇
  1989年   2105篇
  1988年   2021篇
  1987年   1937篇
  1986年   1861篇
  1985年   2411篇
  1984年   2554篇
  1983年   2070篇
  1982年   2264篇
  1981年   2129篇
  1980年   2052篇
  1979年   2173篇
  1978年   2325篇
  1977年   2215篇
  1976年   2256篇
  1975年   2139篇
  1974年   2166篇
  1973年   2170篇
  1972年   1438篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Ohne Zusammenfassung
Trace analysis of lead, cadmium and manganese in honey and sugar

Wir danken dem Fonds der Chemischen Industrie für finanzielle Unterstützung.  相似文献   
73.
A survey of results on a number of problems of the geometric theory of invariants of groups generated by orthogonal and skew reflections is given. The paper is a continuation of the author's surveys published in 1980 and 1984.Translated from Itogi Nauki i Tekhniki, Seriya Problemy Geometrii, Vol. 21, pp. 155–208, 1989.  相似文献   
74.
We prove that for every fixed k and ? ≥ 5 and for sufficiently large n, every edge coloring of the hypercube Qn with k colors contains a monochromatic cycle of length 2 ?. This answers an open question of Chung. Our techniques provide also a characterization of all subgraphs H of the hypercube which are Ramsey, that is, have the property that for every k, any k‐edge coloring of a sufficiently large Qn contains a monochromatic copy of H. © 2006 Wiley Periodicals, Inc. J Graph Theory 53: 196–208, 2006  相似文献   
75.
76.
We give sufficient conditions for a sequence to have theQ-order and/or theR-order of convergence greater than one. If an additional condition is satisfied, then the sequence has an exactQ-order of convergence. We show that our results are sharp and we compare them with older results.This work was supported in part by the National Science Foundation under Grant No. DMS-85-03365. The author wishes to thank J. E. Dennis and R. A. Tapia for helpful comments, and the referee for pointing out a number of typographical and mathematical errors in the original version of this paper.  相似文献   
77.
An upper bound for the number of components of the numerical range of matrix polynomials is established. We also establish a necessary condition and a sufficient condition for the connectedness of the numerical range of a quadratic selfadjoint matrix polynomial. The boundary of the numerical range of linear matrix polynomials is also considered.  相似文献   
78.
In the present work, a quantitative analysis of the phase compositions by Mössbauer effect spectroscopy of solid and conventional hydrogen disproportionated Pr13.7Fe80.3B6.0 and Pr13.7Fe63.5Co16.7Zr0.1B6.0 alloys was carried out. Significant amounts of intermediate borides t-Fe3B and Pr(Fe, Co)12B6 were detected after solid hydrogen disproportionation treatment in Pr13.7Fe80.3B6.0 and Pr13.7Fe63.5Co16.7Zr0.1B6.0 alloys, respectively. After conventional hydrogenation–disproportionation–desorption–recombination treatment these phases were not detected and in no case residual Pr2Fe14B-phase was found. It was observed that the amount of intermediate borides after disproportionation can be correlated with the degree of texture after recombination at various temperatures.  相似文献   
79.
We have investigated the low-lying collective states and electromagnetic transitions in 94Mo within the framework of the interacting boson model. The influence of model parameters on the energy levels and electromagnetic properties has been investigated. The analysis of the obtained results and the parameter values predict that the 23+state is the lowest mixed symmetry state with pure F = Fmax - 1 in this nucleus. The calculated results predicate that the 25+ (two-Q-phonon) mixed symmetry state is closed to the J = 2+ at 2.870 MeV in the experimental data, and the 2.965 MeV state is the lowest mixed symmetry with J = 3+.  相似文献   
80.
Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 41, No. 8, pp. 1054–1058, August, 1989.  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