全文获取类型
收费全文 | 2825篇 |
免费 | 377篇 |
国内免费 | 417篇 |
专业分类
化学 | 304篇 |
晶体学 | 19篇 |
力学 | 350篇 |
综合类 | 79篇 |
数学 | 1903篇 |
物理学 | 964篇 |
出版年
2024年 | 5篇 |
2023年 | 20篇 |
2022年 | 32篇 |
2021年 | 53篇 |
2020年 | 57篇 |
2019年 | 55篇 |
2018年 | 57篇 |
2017年 | 70篇 |
2016年 | 68篇 |
2015年 | 65篇 |
2014年 | 97篇 |
2013年 | 303篇 |
2012年 | 114篇 |
2011年 | 140篇 |
2010年 | 122篇 |
2009年 | 134篇 |
2008年 | 190篇 |
2007年 | 196篇 |
2006年 | 184篇 |
2005年 | 144篇 |
2004年 | 148篇 |
2003年 | 170篇 |
2002年 | 147篇 |
2001年 | 148篇 |
2000年 | 141篇 |
1999年 | 117篇 |
1998年 | 135篇 |
1997年 | 92篇 |
1996年 | 79篇 |
1995年 | 61篇 |
1994年 | 66篇 |
1993年 | 34篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 28篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 3篇 |
1984年 | 23篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1959年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有3619条查询结果,搜索用时 234 毫秒
61.
Vladimir E. Bondarenko 《Complexity》2005,11(2):39-52
Information processing and two types of memory in an analog neural network model with time delay that produces chaos similar to the human and animal EEGs are considered. There are two levels of information processing in this neural network: the level of individual neurons and the level of the neural network. Similar to the state of brain, the state of chaotic neural network is defined. It is characterized by two types of memories (memory I and memory II) and correlation structure between the neurons. In normal (unperturbed) state, the neural network generates chaotic patterns of averaged neuronal activities (memory I) and patterns of oscillation amplitudes (memory II). In the presence of external stimulation, the activity patterns change, showing changes in both types of memory. As in experiments on stimulation of the brain, the neural network model shows synchronization of neuronal activities due to stimulus measured by Pearson's correlation coefficient. An increase in neural network asymmetry (increase of the neural network excitability) leads to the phenomenon similar to the epilepsy. Modeling of brain injury, Parkinson's disease, and dementia is performed by removing and weakening interneuron connections. In all cases, the chaotic neural network shows a decrease of the degree of chaos and changes in both types of memory similar to those observed in experiments with healthy human subjects and patients with Parkinson's disease and dementia. © 2005 Wiley Periodicals, Inc. Complexity 11:39–52, 2005 相似文献
62.
Chen Yongnian 《模糊系统与数学》1995,(1)
ANTIFUZZYVECTORSPACES(Ⅱ)ChenYongnian(DepartmentofMathematics,XinjiangNormalUniversity,830054,Xinjiang,P.R.China)ANTIFUZZYVECT... 相似文献
63.
Dong Sheng WU Yi Min XIAO 《数学学报(英文版)》2007,23(4):613-622
Let B^α = {B^α(t),t E R^N} be an (N,d)-fractional Brownian motion with Hurst index α∈ (0, 1). By applying the strong local nondeterminism of B^α, we prove certain forms of uniform Hausdorff dimension results for the images of B^α when N 〉 αd. Our results extend those of Kaufman for one-dimensional Brownian motion. 相似文献
64.
The leading logarithmic corrections to the critical behavior of a dilute uniaxial (Ising) ferromagnet in the disordered phase are derived using renormalization group methods. The values of the exponents in the logarithmic terms differ from those given by previous authors. 相似文献
65.
The famous 1960's construction of Golod and Shafarevich yields infinite dimensional nil, but not nilpotent, algebras. However, these algebras have exponential growth. Here, we construct an infinite dimensional nil, but not locally nilpotent, algebra which has polynomially bounded growth.
66.
在研究小波变换及布朗分形模型的基础上,定义了水平分维数,垂直分维数,对角分维数,并将它们作为纹理特征量来实现纹理的分割.实验结果表明,这些特征量能够很好地反映纹理特征,从而分割时不需有关图象中纹理类别的先验信息,较以往方法在准确度和计算复杂程度上都有很大提高. 相似文献
67.
Let X(t) be an N parameter generalized Lévy sheet taking values in ℝd with a lower index α, ℜ = {(s, t] = ∏
i=1
N
(s
i, t
i], s
i < t
i}, E(x, Q) = {t ∈ Q: X(t) = x}, Q ∈ ℜ be the level set of X at x and X(Q) = {x: ∃t ∈ Q such that X(t) = x} be the image of X on Q. In this paper, the problems of the existence and increment size of the local times for X(t) are studied. In addition, the Hausdorff dimension of E(x, Q) and the upper bound of a uniform dimension for X(Q) are also established. 相似文献
68.
Arun Mundkur 《Algebras and Representation Theory》2002,5(1):3-55
This article provides an introduction to A. Bak's theory of group-valued functors on categories with structure and dimension and applies this theory to the algebraic K-theory functors nonstable K
1 and K
2. 相似文献
69.
We show that the problem of deciding whether anN-free ordered set has dimension at most 3 is NP-complete.Both authors supported by Office of Naval Research contract N00014-85K-0494. 相似文献
70.
We define a classical probability analogue of Voiculescu's free entropy dimension that we shall call the classical probability entropy dimension of a probability measure on Rn. We show that the classical probability entropy dimension of a measure is related with diverse other notions of dimension. First, it can be viewed as a kind of fractal dimension. Second, if one extends Bochner's inequalities to a measure by requiring that microstates around this measure asymptotically satisfy the classical Bochner's inequalities, then we show that the classical probability entropy dimension controls the rate of increase of optimal constants in Bochner's inequality for a measure regularized by convolution with the Gaussian law as the regularization is removed. We introduce a free analogue of the Bochner inequality and study the related free entropy dimension quantity. We show that it is greater or equal to the non-microstates free entropy dimension. 相似文献