全文获取类型
收费全文 | 4055篇 |
免费 | 685篇 |
国内免费 | 453篇 |
专业分类
化学 | 164篇 |
晶体学 | 1篇 |
力学 | 95篇 |
综合类 | 66篇 |
数学 | 2956篇 |
物理学 | 1911篇 |
出版年
2024年 | 8篇 |
2023年 | 39篇 |
2022年 | 48篇 |
2021年 | 101篇 |
2020年 | 110篇 |
2019年 | 106篇 |
2018年 | 119篇 |
2017年 | 98篇 |
2016年 | 135篇 |
2015年 | 76篇 |
2014年 | 255篇 |
2013年 | 309篇 |
2012年 | 231篇 |
2011年 | 252篇 |
2010年 | 274篇 |
2009年 | 314篇 |
2008年 | 375篇 |
2007年 | 349篇 |
2006年 | 298篇 |
2005年 | 234篇 |
2004年 | 173篇 |
2003年 | 210篇 |
2002年 | 161篇 |
2001年 | 146篇 |
2000年 | 122篇 |
1999年 | 107篇 |
1998年 | 104篇 |
1997年 | 81篇 |
1996年 | 70篇 |
1995年 | 34篇 |
1994年 | 34篇 |
1993年 | 22篇 |
1992年 | 22篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 17篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 4篇 |
排序方式: 共有5193条查询结果,搜索用时 140 毫秒
1.
2.
3.
Immanuel Albrecht 《Discrete Mathematics》2021,344(1):112157
We show that every gammoid has special digraph representations, such that a representation of the dual of the gammoid may be easily obtained by reversing all arcs. In an informal sense, the duality notion of a poset applied to the digraph of a special representation of a gammoid commutes with the operation of forming the dual of that gammoid. We use these special representations in order to define a complexity measure for gammoids, such that the classes of gammoids with bounded complexity are closed under duality, minors, and direct sums. 相似文献
4.
5.
6.
Palle E.T. Jorgensen Erin P.J. Pearse 《Journal of Mathematical Analysis and Applications》2019,469(2):765-807
Motivated by applications to machine learning, we construct a reversible and irreducible Markov chain whose state space is a certain collection of measurable sets of a chosen l.c.h. space . We study the resulting network (connected undirected graph), including transience, Royden and Riesz decompositions, and kernel factorization. We describe a construction for Hilbert spaces of signed measures which comes equipped with a new notion of reproducing kernels and there is a unique solution to a regularized optimization problem involving the approximation of functions by functions of finite energy. The latter has applications to machine learning (for Markov random fields, for example). 相似文献
7.
本文给出对数K-Carleson测度的一个新特征,并以此为工具研究QK空间的乘子代数M(QK),给出乘子代数M(QK)的某些特征描述.利用对数K-Carleson测度及QK空间的一个新特征,建立乘子代数M(QK)上的Corona定理和Wolff定理. 相似文献
8.
This paper is our attempt, on the basis of physical theory, to bring more clarification on the question “What is life?” formulated in the well-known book of Schrödinger in 1944. According to Schrödinger, the main distinguishing feature of a biosystem’s functioning is the ability to preserve its order structure or, in mathematical terms, to prevent increasing of entropy. However, Schrödinger’s analysis shows that the classical theory is not able to adequately describe the order-stability in a biosystem. Schrödinger also appealed to the ambiguous notion of negative entropy. We apply quantum theory. As is well-known, behaviour of the quantum von Neumann entropy crucially differs from behaviour of classical entropy. We consider a complex biosystem S composed of many subsystems, say proteins, cells, or neural networks in the brain, that is, We study the following problem: whether the compound system S can maintain “global order” in the situation of an increase of local disorder and if S can preserve the low entropy while other increase their entropies (may be essentially). We show that the entropy of a system as a whole can be constant, while the entropies of its parts rising. For classical systems, this is impossible, because the entropy of S cannot be less than the entropy of its subsystem . And if a subsystems’s entropy increases, then a system’s entropy should also increase, by at least the same amount. However, within the quantum information theory, the answer is positive. The significant role is played by the entanglement of a subsystems’ states. In the absence of entanglement, the increasing of local disorder implies an increasing disorder in the compound system S (as in the classical regime). In this note, we proceed within a quantum-like approach to mathematical modeling of information processing by biosystems—respecting the quantum laws need not be based on genuine quantum physical processes in biosystems. Recently, such modeling found numerous applications in molecular biology, genetics, evolution theory, cognition, psychology and decision making. The quantum-like model of order stability can be applied not only in biology, but also in social science and artificial intelligence. 相似文献
9.
多组份纠缠是量子信息处理的重要资源,它的产生通常涉及到许多复杂的线性和非线性过程.本文从理论上提出了一种利用两个独立的四波混频过程和线性分束器产生真正的四组份纠缠的方案,其中,线性分束器的作用是将两个独立的四波混频过程联系起来.首先应用部分转置正定判据研究了强度增益对四组份纠缠的影响,结果表明,在整个增益区域内都存在真正的四组份纠缠,并且随着强度增益的增加,纠缠也在增强.然后研究了线性分束器的透射率对四组份纠缠的影响,发现只要线性分束器的透射率不为0或1,该系统也可以产生真正的四组份纠缠.最后,通过研究该系统可能存在的三组份纠缠和两组份纠缠来揭示该系统的纠缠结构.本文理论结果为实验上利用原子系综四波混频过程产生真正的四组份纠缠提供了可靠的方案. 相似文献
10.
设(χ,d,μ)是一个同时满足上双倍条件和几何双倍条件的非齐度量测度空间,对于引进的一类非齐度量测度空间上的Morrey-Herz空间,利用非齐度量测度空间的特征,证明了广义分数次积分算子及其交换子在非齐度量测度空间上MorreyHerz空间的有界性. 相似文献