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   5951篇
  免费   507篇
  国内免费   460篇
化学   729篇
晶体学   21篇
力学   1434篇
综合类   81篇
数学   2857篇
物理学   1796篇
  2024年   21篇
  2023年   61篇
  2022年   111篇
  2021年   123篇
  2020年   161篇
  2019年   146篇
  2018年   168篇
  2017年   157篇
  2016年   185篇
  2015年   192篇
  2014年   287篇
  2013年   405篇
  2012年   269篇
  2011年   307篇
  2010年   275篇
  2009年   314篇
  2008年   300篇
  2007年   339篇
  2006年   342篇
  2005年   295篇
  2004年   239篇
  2003年   255篇
  2002年   222篇
  2001年   188篇
  2000年   182篇
  1999年   179篇
  1998年   127篇
  1997年   146篇
  1996年   102篇
  1995年   108篇
  1994年   94篇
  1993年   88篇
  1992年   74篇
  1991年   80篇
  1990年   57篇
  1989年   36篇
  1988年   40篇
  1987年   27篇
  1986年   23篇
  1985年   27篇
  1984年   26篇
  1983年   13篇
  1982年   23篇
  1981年   13篇
  1980年   18篇
  1979年   22篇
  1978年   8篇
  1977年   10篇
  1976年   12篇
  1974年   7篇
排序方式: 共有6918条查询结果,搜索用时 15 毫秒
41.
This paper deals with a class of nonlinear elliptic equations involving a critical power-nonlinearity as well as a potential featuring multiple inverse square singularities. When the poles form a symmetric structure, it is natural we wonder how the symmetry affects such mutual interaction. The present paper means to study this aspect from the point of view of the existence of solutions inheriting the same symmetry properties as the set of singularities. Mathematics Subject Classification (2000) 35J60, 35J20, 35B33  相似文献   
42.
The quantum action (dynamical) principle is exploited to investigate the nature and origin of the Faddeev–Popov (FP) factor in gauge theories without recourse to path integrals. Gauge invariant as well as gauge non-invariant interactions are considered to show that the FP factor needs to be modified in more general cases and expressions for these modifications are derived. In particular we show that a gauge invariant theory does not necessarily imply the familiar FP factor for proper quantization. PACS numbers: 11.15.-q; 12.10.-g; 12.15.-y; 12.38.-t  相似文献   
43.
In this paper we give some new results concerning solvability of the 1-dimensional differential equation y′ = f(x, y) with initial conditions. We study the basic theorem due to Picard. First we prove that the existence and uniqueness result remains true if f is a Lipschitz function with respect to the first argument. In the second part we give a contractive method for the proof of Picard theorem. These considerations allow us to develop two new methods for finding an approximation sequence for the solution. Finally, some applications are given.  相似文献   
44.
It is proved that if μ and v be finite measures on a measurable space (X,S) and v is absolutely continuous with respect to v, then it is holds that L(^*S,^*v) C L(^*S,^*v), while L(^*S,^*v) and L(^*S,^*v) are the Loeb algebras with respect to measure spaces (X,S,μ) and(X,S,μ).  相似文献   
45.
This paper investigates the periodic boundary value problems for a class of second order functional differential equations. The monotone iterative technique and the maximum principle are applied to obtain the existence of maximal and minimal solutions.  相似文献   
46.
Using the full-potential linearized augmented plane wave (FP-LAPW) method, we have studied the effect of chemistry on the average intercalation voltage (AIV) caused by the Na ions intercalating into transition metal oxides. The effect of transition metal was systematically studied by varying M=Co, Ni and Mn in NaMO2 and fixing the α-NaFeO2 layered structure. The effect of the guest atoms into the host material is discussed in terms of the structural and electronic properties. Comparatively to Li intercalation, a significant electron transfer towards transition metal was found. This observation suggests that the transition metal contribute to the AIV determination and confirms the common assumption that intercalated electron reduces M4+ to M3+.  相似文献   
47.
We give a verification theorem by employing Arrow's generalization of the Mangasarian sufficient condition to a general jump diffusion setting and show the connections of adjoint processes to dynamic programming. The result is applied to financial optimization problems.  相似文献   
48.
This note generalizes André's reflection principle to give a new combinatorial proof of a formula for the number of lattice paths lying within certain trapezoids.  相似文献   
49.
The authors establish the Hilbertian invariance principle for the empirical process of a stationary Markov process, by extending the forward-backward martingale decomposition of Lyons-Meyer-Zheng to the Hilbert space valued additive functionals associated with general non-reversible Markov processes.  相似文献   
50.
给出一类较广泛的ρ-混合序列 ,并证明了在一定的矩条件下 ,ρ-混合序列的不变原理成立  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