全文获取类型
收费全文 | 5505篇 |
免费 | 653篇 |
国内免费 | 307篇 |
专业分类
化学 | 366篇 |
晶体学 | 5篇 |
力学 | 551篇 |
综合类 | 145篇 |
数学 | 3571篇 |
物理学 | 1827篇 |
出版年
2024年 | 15篇 |
2023年 | 39篇 |
2022年 | 39篇 |
2021年 | 119篇 |
2020年 | 149篇 |
2019年 | 144篇 |
2018年 | 122篇 |
2017年 | 166篇 |
2016年 | 171篇 |
2015年 | 130篇 |
2014年 | 198篇 |
2013年 | 384篇 |
2012年 | 238篇 |
2011年 | 248篇 |
2010年 | 202篇 |
2009年 | 252篇 |
2008年 | 304篇 |
2007年 | 314篇 |
2006年 | 299篇 |
2005年 | 246篇 |
2004年 | 230篇 |
2003年 | 256篇 |
2002年 | 268篇 |
2001年 | 246篇 |
2000年 | 249篇 |
1999年 | 190篇 |
1998年 | 172篇 |
1997年 | 121篇 |
1996年 | 115篇 |
1995年 | 70篇 |
1994年 | 90篇 |
1993年 | 64篇 |
1992年 | 67篇 |
1991年 | 72篇 |
1990年 | 55篇 |
1989年 | 46篇 |
1988年 | 49篇 |
1987年 | 38篇 |
1986年 | 27篇 |
1985年 | 38篇 |
1984年 | 52篇 |
1983年 | 25篇 |
1982年 | 21篇 |
1981年 | 30篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 16篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1973年 | 6篇 |
排序方式: 共有6465条查询结果,搜索用时 31 毫秒
91.
给出了随机环境中马氏链的特征数和状态的定义,讨论了状态间的传递性,自反性,对称性,是经典马氏链相应结果的一般化.并运用位势方法研究了状态间的关系,它们在极限理论的研究中非常有用. 相似文献
92.
We estimate the concentration functions of n-fold convolutions of one-dimensional probability measures. The Kolmogorov–Rogozin inequality implies that for nondegenerate distributions these functions decrease at least as O(n
–1/2). On the other hand, Esseen(3) has shown that this rate is o(n
–1/2) iff the distribution has an infinite second moment. This statement was sharpened by Morozova.(9) Theorem 1 of this paper provides an improvement of Morozova's result. Moreover, we present more general estimates which imply the rates o(n
–1/2). 相似文献
93.
Probabilistic characteristics of a sliding structure is investigated by using new versions of stochastic linearization technique. The structure is composed of base part and upper part, which are connected to each other in a spring-damping system. Coulomb friction between the base structure and earth ground is considered. Two alternative versions of stochastic linearization approach, suggested by X. Zhang and I. Elishakoff, respectively, are applied to such a sliding structure to evaluate its statistical properties. Compared with the results of Monte Carlo simulation, the two new approaches are performing much better than the conventional one in their applications to the sliding structure. Moreover, numerical results indicate that the criterion proposed by Elishakoff turns out to be superior to all other versions in the problem under study. Numerical results also suggest that the entire structure may be replaced by the rigid body in the sliding problem as long as the difference of velocity responses are considered less important than those of displacement responses. 相似文献
94.
Let (Ω, Σ) be a measurable space, X a Banach space whose characteristic of noncompact convexity is less than 1, C a bounded closed convex subset of X, KC(C) the family of all compact convex subsets of C. We prove that a set-valued nonexpansive mapping T: C → KC(C) has a fixed point. Furthermore, if X is separable then we also prove that a set-valued nonexpansive operator T: Ω × C → KC(C) has a random fixed point. 相似文献
95.
基于任意形状颗粒集合的二值图像,提出了估计其体积(或质量)的方法.首先利用发光背景台面获取的颗粒灰度图像变换为相应的二值图像,得到颗粒的边界轮廓.然后再基于其边界信息,定义与颗粒形状特征相关的描述量,并将其无量纲化.将由此定义的无量纲参变量作为回归变量建立一个多元线性回归(multiple linear regression)模型用以估计颗粒集合的扁平度,进而估算颗粒体积.回归变量的系数由随机采样的501个样本颗粒(尺寸范围为4.75~25 mm)用误差最小平方和求得.将模型应用于由具有相似统计分布特征的其他颗粒集合,并将得到的体积估计值与其体积真实值相比较,实验结果显示模型的相对误差在±2%以内. 相似文献
96.
The kink of cellular automaton rule 18 performs a random walk 总被引:1,自引:0,他引:1
We give an exact characterization of the movement of a single kink in the elementary cellular automaton Rule 18. It is a random walk with independent increments as well as independent delay times. Its statistical parameters are computed to confirm the earlier simulation results by Grassberger. 相似文献
97.
Pierre L'Ecuyer 《Annals of Operations Research》1994,53(1):77-120
In typical stochastic simulations, randomness is produced by generating a sequence of independent uniform variates (usually real-valued between 0 and 1, or integer-valued in some interval) and transforming them in an appropriate way. In this paper, we examine practical ways of generating (deterministic approximations to) such uniform variates on a computer. We compare them in terms of ease of implementation, efficiency, theoretical support, and statistical robustness. We look in particular at several classes of generators, such as linear congruential, multiple recursive, digital multistep, Tausworthe, lagged-Fibonacci, generalized feedback shift register, matrix, linear congruential over fields of formal series, and combined generators, and show how all of them can be analyzed in terms of their lattice structure. We also mention other classes of generators, like non-linear generators, discuss other kinds of theoretical and empirical statistical tests, and give a bibliographic survey of recent papers on the subject. 相似文献
98.
99.
通过构造随机变量的方法,并结合凸函数的性质,证明了数学分析中的一些著名不等式,证明方法简明、独特. 相似文献
100.
ZHU Hai-Xia YAN Shi-Lei 《理论物理通讯》2004,42(11)
We study the ferromagnetic properties of spin-1 system, which is considered in the frame of the bond dilution and random positive or negative anisotropy Blume-Capel model in the effective field theory and a cutting approximation. The investigation of phase diagrams displays some rich properties of the trajectory of tricritical point, reentrant henomena at low temperatures. Under certain both bond concentrations and random negative anisotropy, there are new transition lines of double tricritical points. So special emphasis is placed on the influence of the bond dilution and random anisotropy on phase diagrams. The magnetizations of the system are also discussed. Some results have not been evealed in previous reports. 相似文献