全文获取类型
收费全文 | 3524篇 |
免费 | 206篇 |
国内免费 | 155篇 |
专业分类
化学 | 126篇 |
晶体学 | 3篇 |
力学 | 73篇 |
综合类 | 34篇 |
数学 | 3229篇 |
物理学 | 420篇 |
出版年
2024年 | 13篇 |
2023年 | 61篇 |
2022年 | 86篇 |
2021年 | 62篇 |
2020年 | 122篇 |
2019年 | 115篇 |
2018年 | 119篇 |
2017年 | 111篇 |
2016年 | 81篇 |
2015年 | 87篇 |
2014年 | 136篇 |
2013年 | 308篇 |
2012年 | 120篇 |
2011年 | 191篇 |
2010年 | 187篇 |
2009年 | 331篇 |
2008年 | 269篇 |
2007年 | 217篇 |
2006年 | 196篇 |
2005年 | 133篇 |
2004年 | 123篇 |
2003年 | 116篇 |
2002年 | 107篇 |
2001年 | 88篇 |
2000年 | 83篇 |
1999年 | 71篇 |
1998年 | 71篇 |
1997年 | 60篇 |
1996年 | 39篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 14篇 |
1991年 | 8篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1970年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有3885条查询结果,搜索用时 78 毫秒
131.
Let (X, d, μ) be a metric measure space with non-negative Ricci curvature. This paper is concerned with the boundary behavior of harmonic function on the (open) upper half-space . We derive that a function f of bounded mean oscillation (BMO) is the trace of harmonic function on , whenever u satisfies the following Carleson measure condition where denotes the total gradient and denotes the (open) ball centered at with radius . Conversely, the above condition characterizes all the harmonic functions whose traces are in BMO space. 相似文献
132.
Yongtao LIU 《Frontiers of Mathematics in China》2021,16(3):783
By using the perpetual cutoff method, we prove two discrete versions of gradient estimates for bounded Laplacian on locally finite graphs with exception sets under the condition of (K,N). This generalizes a main result of F. Münch who considers the case of CD(K, ) curvature. Hence, we answer a question raised by Münch. For that purpose, we characterize some basic properties of radical form of the perpetual cutoff semigroup and give a weak commutation relation between bounded Laplacian and perpetual cutoff semigroup in our setting. 相似文献
133.
The book-embedding problem arises in several area, such as very large scale integration (VLSI) design and routing multilayer printed circuit boards (PCBs). It can be used into various practical application fields. A book embedding of a graph G is an embedding of its vertices along the spine of a book, and an embedding of its edges to the pages such that edges embedded on the same page do not intersect. The minimum number of pages in which a graph G can be embedded is called the pagenumber or book-thickness of the graph G. It is an important measure of the quality for book-embedding. It is NP-hard to research the pagenumber of book-embedding for a graph G. This paper summarizes the studies on the book-embedding of planar graphs in recent years. 相似文献
134.
Models based on sparse graphs are of interest to many communities: they appear as basic models in combinatorics, probability theory, optimization, statistical physics, information theory, and more applied fields of social sciences and economics. Different notions of similarity (and hence convergence) of sparse graphs are of interest in different communities. In probability theory and combinatorics, the notion of Benjamini‐Schramm convergence, also known as left‐convergence, is used quite frequently. Statistical physicists are interested in the the existence of the thermodynamic limit of free energies, which leads naturally to the notion of right‐convergence. Combinatorial optimization problems naturally lead to so‐called partition convergence, which relates to the convergence of optimal values of a variety of constraint satisfaction problems. The relationship between these different notions of similarity and convergence is, however, poorly understood. In this paper we introduce a new notion of convergence of sparse graphs, which we call Large Deviations or LD‐convergence, and which is based on the theory of large deviations. The notion is introduced by “decorating” the nodes of the graph with random uniform i.i.d. weights and constructing corresponding random measures on and . A graph sequence is defined to be converging if the corresponding sequence of random measures satisfies the Large Deviations Principle with respect to the topology of weak convergence on bounded measures on . The corresponding large deviations rate function can be interpreted as the limit object of the sparse graph sequence. In particular, we can express the limiting free energies in terms of this limit object. We then establish that LD‐convergence implies the other three notions of convergence discussed above, and at the same time establish several previously unknown relationships between the other notions of convergence. In particular, we show that partition‐convergence does not imply left‐ or right‐convergence, and that right‐convergence does not imply partition‐convergence. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 51, 52–89, 2017 相似文献
135.
Let G be a connected regular graph. Denoted by t(G) and Kf(G) the total graph and Kirchhoff index of G, respectively. This paper is to point out that Theorem 3.7 and Corollary 3.8 from “Kirchhoff index in line, subdivision and total graphs of a regular graph” [X. Gao, Y.F. Luo, W.W. Liu, Kirchhoff index in line, subdivision and total graphs of a regular graph, Discrete Appl. Math. 160(2012) 560–565] are incorrect, since the conclusion of a lemma is essentially wrong. Moreover, we first show the Laplacian characteristic polynomial of t(G), where G is a regular graph. Consequently, by using Kf(G), we give an expression on Kf(t(G)) and a lower bound on Kf(t(G)) of a regular graph G, which correct Theorem 3.7 and Corollary 3.8 in Gao et al. (2012) [2]. 相似文献
136.
137.
It is considered the class of Riemann surfaces with dimT1 = 0, where T1 is a subclass of exact harmonic forms which is one of the factors in the orthogonal decomposition of the spaceΩH of harmonic forms of the surface, namely The surfaces in the class OHD and the class of planar surfaces satisfy dimT1 = 0. A.Pfluger posed the question whether there might exist other surfaces outside those two classes. Here it is shown that in the case of finite genus g, we should look for a surface S with dimT1 = 0 among the surfaces of the form Sg\K , where Sg is a closed surface of genus g and K a compact set of positive harmonic measure with perfect components and very irregular boundary. 相似文献
138.
一类特殊分块矩阵为循环矩阵的循环分块矩阵的几个性质 总被引:3,自引:0,他引:3
本文给出一类特殊分块矩阵为循环矩阵的循环分块矩阵的几个性质。 相似文献
139.
140.