全文获取类型
收费全文 | 23213篇 |
免费 | 1786篇 |
国内免费 | 1522篇 |
专业分类
化学 | 8120篇 |
晶体学 | 237篇 |
力学 | 1529篇 |
综合类 | 251篇 |
数学 | 7707篇 |
物理学 | 8677篇 |
出版年
2023年 | 185篇 |
2022年 | 535篇 |
2021年 | 469篇 |
2020年 | 463篇 |
2019年 | 467篇 |
2018年 | 421篇 |
2017年 | 478篇 |
2016年 | 515篇 |
2015年 | 469篇 |
2014年 | 735篇 |
2013年 | 1453篇 |
2012年 | 854篇 |
2011年 | 941篇 |
2010年 | 925篇 |
2009年 | 1677篇 |
2008年 | 1740篇 |
2007年 | 1665篇 |
2006年 | 1501篇 |
2005年 | 1051篇 |
2004年 | 888篇 |
2003年 | 903篇 |
2002年 | 971篇 |
2001年 | 795篇 |
2000年 | 707篇 |
1999年 | 659篇 |
1998年 | 634篇 |
1997年 | 430篇 |
1996年 | 310篇 |
1995年 | 286篇 |
1994年 | 284篇 |
1993年 | 236篇 |
1992年 | 312篇 |
1991年 | 197篇 |
1990年 | 153篇 |
1989年 | 127篇 |
1988年 | 143篇 |
1987年 | 132篇 |
1986年 | 120篇 |
1985年 | 120篇 |
1984年 | 114篇 |
1983年 | 68篇 |
1982年 | 135篇 |
1981年 | 194篇 |
1980年 | 194篇 |
1979年 | 196篇 |
1978年 | 182篇 |
1977年 | 122篇 |
1976年 | 127篇 |
1973年 | 83篇 |
1972年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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
62.
Alessandro Conflitti 《Finite Fields and Their Applications》2003,9(4):423-431
We propose a probabilistic algorithm to reduce computing the greatest common divisor of m polynomials over a finite field (which requires computing m−1 pairwise greatest common divisors) to computing the greatest common divisor of two polynomials over the same field. 相似文献
63.
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
64.
A locally convex space is said to be a Gateaux differentiability space (GDS)provided every continuous convex function defined on a nonempty convex open subset D of the space is densely Gateaux differentiable in D.This paper shows that the product of a GDS and a family of separable Frechet spaces is a GDS,and that the product of a GDS and an arbitrary locally convex space endowed with the weak topology is a GDS. 相似文献
65.
Burn‐in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, we consider the problem of determining the optimal burn‐in time and optimal work size maximizing the long‐run average amount of work saved per time unit in the computer applications. Assuming that the underlying lifetime distribution of the computer has an initially decreasing or/and eventually increasing failure rate function, an upper bound for the optimal burn‐in time is derived for each fixed work size and a uniform (with respect to the burn‐in time) upper bound for the optimal work size is also obtained. Furthermore, it is shown that a non‐trivial lower bound for the optimal burn‐in time can be derived if the underlying lifetime distribution has a large initial failure rate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
66.
Kurt Majewski 《Queueing Systems》2005,50(2-3):199-230
We consider multiclass feedforward queueing networks under first in first out and priority service disciplines driven by long-range dependent arrival and service time processes. We show that in critical loading the normalized workload, queue length and sojourn time processes can converge to a multi-dimensional reflected fractional Brownian motion. This weak heavy traffic approximation is deduced from a deterministic pathwise approximation of the network behavior close to constant critical load in terms of the solution of a Skorokhod problem. Since we model the doubly infinite time interval, our results directly cover the stationary case.AMS subject classification: primary 90B15, secondary 60K25, 68M20 相似文献
67.
有限循环群的Fuzzy子群的等价类数 总被引:4,自引:2,他引:2
有限循环群G的F子群可以有无数个.但是.若当两个F子群的水平集构成的集合相等就称其等价的话,那么其等价类数是有限的。通过研究群的合成群列、商群列以及数的因数列和极大因数列找出了有限循环群的极大F子群和F子群的等价类数的求解公式.并给出二者之间的关系式. 相似文献
68.
Christopher J. Nichols 《Tetrahedron letters》2004,45(40):7469-7473
A number of new functionalised bridged indolocarbazole systems have been prepared by ring-opening reactions of a key cyclic sulfate intermediate, prepared from the corresponding diol by the action of sulfuryl diimidazole and DBU. The same cyclic sulfate also undergoes an unprecedented asymmetric rearrangement to a chiral ketone, on treatment with a chiral lithium amide base. 相似文献
69.
Twenty-five years ago, we introduced the phenomenon of negative luminescence (NL) into semiconductor physics. This paper provides an overview of work conducted to develop this fundamental concept. Initially, we consider the first-principle approach to radiation interaction with basic matter and the major properties of NL. Then we describe the problems of NL direct measurements in homogeneous materials and structures. Finally, we emphasize the use of NL approach in applications involving devices for infrared (IR) wavelength (3–12 μm) high-temperature (300–400 K) optoelectronics. Our subjects will include NL IR emitting diodes, radiative coolers, IR dynamic scene simulators, light up-conversion devices, and the Stealth effect in IR. 相似文献
70.
The problem of investigation of the amplitude and phase structure of a time-varying probing optical signal and the structure of time-varying inhomogeneities of a substance tested by this signal is considered. The analysis is concerned, in particular, with determination of the structure of signals and processes with resolution in the pico- and femtosecond range. The scheme used for the analysis is based on registration of four spatially separated spectra of the studied radiation. The spectra are formed in a four-channel scheme with a twin-wave Michelson interferometer and a spectral device. Modulators based on electrooptical crystals (perovskites) are placed in the channels. The sum spectra are formed: without modulators, with the effect of either of the modulators, and with both of them affecting the radiation. The effect of the studied substance implies either modulating the radiation (in this case it is described by multiplication) or redistributing the radiation (then it is described by convolution). 相似文献