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   5230篇
  免费   832篇
  国内免费   430篇
化学   690篇
晶体学   17篇
力学   318篇
综合类   110篇
数学   2668篇
物理学   2689篇
  2024年   14篇
  2023年   42篇
  2022年   405篇
  2021年   413篇
  2020年   201篇
  2019年   147篇
  2018年   153篇
  2017年   166篇
  2016年   228篇
  2015年   151篇
  2014年   254篇
  2013年   337篇
  2012年   256篇
  2011年   261篇
  2010年   241篇
  2009年   285篇
  2008年   339篇
  2007年   305篇
  2006年   276篇
  2005年   273篇
  2004年   212篇
  2003年   216篇
  2002年   221篇
  2001年   159篇
  2000年   130篇
  1999年   122篇
  1998年   89篇
  1997年   103篇
  1996年   60篇
  1995年   46篇
  1994年   55篇
  1993年   31篇
  1992年   44篇
  1991年   29篇
  1990年   24篇
  1989年   32篇
  1988年   27篇
  1987年   27篇
  1986年   9篇
  1985年   20篇
  1984年   13篇
  1983年   5篇
  1982年   12篇
  1981年   11篇
  1980年   13篇
  1979年   8篇
  1978年   4篇
  1977年   5篇
  1973年   3篇
  1969年   4篇
排序方式: 共有6492条查询结果,搜索用时 0 毫秒
1.
Space-time directional Lyapunov exponents are introduced. They describe the maximal velocity of propagation to the right or to the left of fronts of perturbations in a frame moving with a given velocity. The continuity of these exponents as function of the velocity and an inequality relating them to the directional entropy is proved.  相似文献   
2.
A particular case of initial data for the two-dimensional Euler equations is studied numerically. The results show that the Godunov method does not always converge to the physical solution, at least not on feasible grids. Moreover, they suggest that entropy solutions (in the weak entropy inequality sense) are not well posed.

  相似文献   

3.
NA列加权乘积和的完全收敛性   总被引:4,自引:0,他引:4  
本文讨论了NA和几类加权部分和及加权乘积和的完全收敛性,其中部分结果要优于iid列的已知结论。  相似文献   
4.
We formulate an elementary statistical game which captures the essence of some fundamental quantum experiments such as photon polarization and spin measurement. We explore and compare the significance of the principle of maximum Shannon entropy and the principle of minimum Fisher information in solving such a game. The solution based on the principle of minimum Fisher information coincides with the solution based on an invariance principle, and provides an informational explanation of Malus' law for photon polarization. There is no solution based on the principle of maximum Shannon entropy. The result demonstrates the merits of Fisher information, and the demerits of Shannon entropy, in treating some fundamental quantum problems. It also provides a quantitative example in support of a general philosophy: Nature intends to hide Fisher information, while obeying some simple rules.  相似文献   
5.
We analyze the functioning of Gibbs-type entropy functionals in the time domain, with emphasis on Shannon and Kullback-Leibler entropies of time-dependent continuous probability distributions. The Shannon entropy validity is extended to probability distributions inferred from L 2(R n ) quantum wave packets. In contrast to the von Neumann entropy which simply vanishes on pure states, the differential entropy quantifies the degree of probability (de)localization and its time development. The associated dynamics of the Fisher information functional quantifies nontrivial power transfer processes in the mean, both in dissipative and quantum mechanical cases. PACS NUMBERS: 05.45.+b, 02.50.-r, 03.65.Ta, 03.67.-a  相似文献   
6.
This short note summarizes the circumstances of the birth of free probability theory andsome of the recent achievements.  相似文献   
7.
A localH-theorem is derived for a recently proposed extension of Enskog kinetic theory to a dense model fluid composed of particles with interactions extending beyond a hard core.On leave from: Katedra Fizyki, Uniwersytetu Szczecinskiego, 70-451 Szczecin, Poland.  相似文献   
8.
M. D. Srinivas 《Pramana》2003,60(6):1137-1152
We derive an optimal bound on the sum of entropic uncertainties of two or more observables when they are sequentially measured on the same ensemble of systems. This optimal bound is shown to be greater than or equal to the bounds derived in the literature on the sum of entropie uncertainties of two observables which are measured on distinct but identically prepared ensembles of systems. In the case of a two-dimensional Hilbert space, the optimum bound for successive measurements of two-spin components, is seen to be strictly greater than the optimal bound for the case when they are measured on distinct ensembles, except when the spin components are mutually parallel or perpendicular  相似文献   
9.
This paper gives the weighted Lp convergence rate estimations of the Gruenwald interpolatory polynomials based on the zeros of Chebyshev polymomials of the first kind,and proves that the order of the estimations is optimal for p≥1.  相似文献   
10.
通过对非饱和土非线性本构方程和场方程的线性化,推导出了非饱和土的线性本构方程和场方程,把线性方程表示为与Biot饱和多孔介质方程相似的形式;证明了Darcy定律对非饱和土的适用性;说明了Biot饱和多孔介质方程是这些线性方程的特征。所有这些都表明用混合理论处理非饱和土本构问题的正确性。  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