全文获取类型
收费全文 | 9445篇 |
免费 | 965篇 |
国内免费 | 680篇 |
专业分类
化学 | 1655篇 |
晶体学 | 14篇 |
力学 | 710篇 |
综合类 | 338篇 |
数学 | 5761篇 |
物理学 | 2612篇 |
出版年
2024年 | 21篇 |
2023年 | 69篇 |
2022年 | 157篇 |
2021年 | 214篇 |
2020年 | 250篇 |
2019年 | 240篇 |
2018年 | 207篇 |
2017年 | 285篇 |
2016年 | 306篇 |
2015年 | 239篇 |
2014年 | 365篇 |
2013年 | 717篇 |
2012年 | 406篇 |
2011年 | 468篇 |
2010年 | 384篇 |
2009年 | 500篇 |
2008年 | 566篇 |
2007年 | 583篇 |
2006年 | 506篇 |
2005年 | 445篇 |
2004年 | 439篇 |
2003年 | 449篇 |
2002年 | 428篇 |
2001年 | 374篇 |
2000年 | 343篇 |
1999年 | 305篇 |
1998年 | 276篇 |
1997年 | 223篇 |
1996年 | 177篇 |
1995年 | 116篇 |
1994年 | 137篇 |
1993年 | 91篇 |
1992年 | 95篇 |
1991年 | 94篇 |
1990年 | 82篇 |
1989年 | 71篇 |
1988年 | 64篇 |
1987年 | 44篇 |
1986年 | 39篇 |
1985年 | 46篇 |
1984年 | 62篇 |
1983年 | 29篇 |
1982年 | 25篇 |
1981年 | 36篇 |
1980年 | 17篇 |
1979年 | 21篇 |
1978年 | 17篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
讨论了顾客到达时间和服务时间与等待队列队长有关的排队系统模拟,顾客服务次数不止1次即出现循环的复杂排队系统,引入到达因子、服务台因子和循环因子,在串并联多服务台情形下建立了4类计算机模拟模型,给出该复杂循环排队系统在进程调度中的应用并进行了计算机模拟. 相似文献
22.
Miklós Csörgő 《Periodica Mathematica Hungarica》2005,50(1-2):1-27
Summary This article provides a glimpse of some of the highlights of the joint work of Endre Csáki and Pál Révész since 1979. The topics of this short exploration of the rich stochastic milieu of this inspiring collaboration revolve around Brownian motion, random walks and their long excursions, local times and additive functionals, iterated processes, almost sure local and global central limit theorems, integral functionals of geometric stochastic processes, favourite sites--favourite values and jump sizes for random walk and Brownian motion, random walking in a random scenery, and large void zones and occupation times for coalescing random walks. 相似文献
23.
林正炎 《数学物理学报(B辑英文版)》2003,23(3)
Let {X_n, n≥1} be a strictly stationary sequence of random variables, whichare either associated or negatively associated, f(·) be their common density. In this paper,the author shows a central limit theorem for a kernel estimate of f(·) under certain regularconditions. 相似文献
24.
25.
本对于全局优化问题提出一个改进的进化规划算法,该算法以概率p接收基于电磁理论求出合力方向作为随机搜索方向,以概率1-p接收按正态分布产生的随机搜索方向。改进算法不仅克服了传统进化规划算法随机搜索的盲目性,而且保留了传统进化规划算法全局搜索性。本算法应用于几个典型例题,数值结果表明本算法是可行的,有效的。 相似文献
26.
Shirin J. Handjani 《Journal of Theoretical Probability》2003,16(2):325-338
We establish conditions for survival and extinction of types of one-dimensional voter models, and show that increasing the flip rates at a finite number of sites typically does not affect survival, unless the flipping mechanism is altered. We provide an example of a modified voter model that does not survive but can be made to survive simply by altering the flip mechanism at one site. We also show that a rather general class of such models have clustering behavior. 相似文献
27.
Fukuji Higashi Kanako Sugishita 《Journal of polymer science. Part A, Polymer chemistry》2004,42(1):44-51
A two‐stage co‐oligomerization of the oligomers initially formed from an equimolar mixture of isophthalic acid (IPA) and terephthalic acid (TPA) and 2,2‐bis(4‐hydroxyphenyl)propane (BPA, 50 mol %) with bisphenols (BPs, 20 mol %) was carried out using a tosyl chloride/dimethylformamide/pyridine condensing agent. The distributions of the resulting oligomers (nx‐mers), which were quenched with methanol, were determined by a combination of gel permeation chromatography (GPC) and NMR. These distributions (presented by molar percentage) were conveniently calculated with the equation nx (mol %) = nx (% mol by GPC) × n0 (mol % by NMR)/n0 (% mol by GPC), where nx (% mol) = nx (wt % by GPC)/its molecular weight. The results showed the distributions of the preformed IPA/TPA‐BPA oligomers to be in fairly good accord with those obtained directly from GPC and to be supported by the NMR results. The calculation was applied to the co‐oligomers prepared up to a reaction of 0.7, at which there was an increase in the number of higher oligomers indivisible by GPC and the distributions could no longer be determined by molar percentage. The calculated distributions are discussed in relation to the results of copolycondensation. The sequence distributions in the resulting co‐oligomers, which were also examined by NMR, are compared with those in the copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 44–51, 2004 相似文献
28.
29.
Lahcne Mezrag 《Mathematische Nachrichten》2004,266(1):60-67
In [5], it is proved that a bounded linear operator u, from a Banach space Y into an Lp(S, ν) factors through Lp1 (S, ν) for some p1 > 1, if Y* is of finite cotype; (S, ν) is a probability space for p = 0, and any measure space for 0 < p < 1. In this paper, we generalize this result to uv, where u : Y → Lp(S, ν) and v : X → Y are linear operators such that v* is of finite Ka?in cotype. This result gives also a new proof of Grothendieck's theorem. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
30.
Shea-Ming Oon 《Periodica Mathematica Hungarica》2004,49(2):107-118
In this paper we study some pseudo-random properties related to the prime factors of integers. We prove some results concerning the well distribution of the greatest prime factor modulo 4, and give some computational insight on the correlations, which seem to be beyond reach of proof. 相似文献