全文获取类型
收费全文 | 100506篇 |
免费 | 8498篇 |
国内免费 | 6632篇 |
专业分类
化学 | 25571篇 |
晶体学 | 330篇 |
力学 | 7221篇 |
综合类 | 1565篇 |
数学 | 58752篇 |
物理学 | 22197篇 |
出版年
2024年 | 121篇 |
2023年 | 862篇 |
2022年 | 1071篇 |
2021年 | 2388篇 |
2020年 | 2354篇 |
2019年 | 2576篇 |
2018年 | 2238篇 |
2017年 | 2416篇 |
2016年 | 2709篇 |
2015年 | 2383篇 |
2014年 | 4076篇 |
2013年 | 7631篇 |
2012年 | 4367篇 |
2011年 | 5190篇 |
2010年 | 4860篇 |
2009年 | 6029篇 |
2008年 | 6411篇 |
2007年 | 6516篇 |
2006年 | 5381篇 |
2005年 | 4493篇 |
2004年 | 3941篇 |
2003年 | 3981篇 |
2002年 | 6201篇 |
2001年 | 3309篇 |
2000年 | 2804篇 |
1999年 | 2516篇 |
1998年 | 2359篇 |
1997年 | 2006篇 |
1996年 | 1563篇 |
1995年 | 1260篇 |
1994年 | 1144篇 |
1993年 | 996篇 |
1992年 | 949篇 |
1991年 | 760篇 |
1990年 | 617篇 |
1989年 | 462篇 |
1988年 | 478篇 |
1987年 | 414篇 |
1986年 | 419篇 |
1985年 | 595篇 |
1984年 | 488篇 |
1983年 | 290篇 |
1982年 | 493篇 |
1981年 | 647篇 |
1980年 | 569篇 |
1979年 | 613篇 |
1978年 | 481篇 |
1977年 | 363篇 |
1976年 | 316篇 |
1973年 | 181篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
We consider the problem of solving the integral form of the radiative transfer equation in an atmosphere with optical thickness τ0?1. We propose two methods transforming this problem to a finite set of the independent problems of the same type set in an atmosphere with optical thickness much less then τ0. The error estimates are derived. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
942.
We give a competitive algorithm to identify all d defective edges in a hypergraph with d unknown. Damaschke did the d=1 case for 2-graphs, Triesch extended the d=1 case to r-graphs, and Johann did the general d case for 2-graphs. So ours is the first attempt to solve the searching for defective edges problem in its full generality. Further, all the above three papers assumed d known. We give a competitive algorithm where d is unknown. 相似文献
943.
S?awomir Solecki 《Topology and its Applications》2007,154(12):2462-2464
Let I0 be the σ-ideal of subsets of a Polish group generated by Borel sets which have perfectly many pairwise disjoint translates. We prove that a Fubini-type theorem holds between I0 and the σ-ideals of Haar measure zero sets and of meager sets. We use this result to give a simple proof of a generalization of a theorem of Balcerzak-Ros?anowski-Shelah stating that I0 on N2 strongly violates the countable chain condition. 相似文献
944.
Let G(x,y) and GD(x,y) be the Green functions of rotationally invariant symmetric α-stable process in Rd and in an open set D, respectively, where 0<α<2. The inequality GD(x,y)GD(y,z)/GD(x,z)?c(G(x,y)+G(y,z)) is a very useful tool in studying (local) Schrödinger operators. When the above inequality is true with c=c(D)∈(0,∞), then we say that the 3G theorem holds in D. In this paper, we establish a generalized version of 3G theorem when D is a bounded κ-fat open set, which includes a bounded John domain. The 3G we consider is of the form GD(x,y)GD(z,w)/GD(x,w), where y may be different from z. When y=z, we recover the usual 3G. The 3G form GD(x,y)GD(z,w)/GD(x,w) appears in non-local Schrödinger operator theory. Using our generalized 3G theorem, we give a concrete class of functions belonging to the non-local Kato class, introduced by Chen and Song, on κ-fat open sets. As an application, we discuss relativistic α-stable processes (relativistic Hamiltonian when α=1) in κ-fat open sets. We identify the Martin boundary and the minimal Martin boundary with the Euclidean boundary for relativistic α-stable processes in κ-fat open sets. Furthermore, we show that relative Fatou type theorem is true for relativistic stable processes in κ-fat open sets. The main results of this paper hold for a large class of symmetric Markov processes, as are illustrated in the last section of this paper. We also discuss the generalized 3G theorem for a large class of symmetric stable Lévy processes. 相似文献
945.
带干扰的Erlang(2)风险模型的不破产概率 总被引:1,自引:0,他引:1
本文讨论了带干扰的Erlang(2)风险模型,通过构造一个延迟更新过程,我们得到了不破产概率满足的积分-微分方程,进而得到了不破产概率的明确表达式. 相似文献
946.
For linear statistical ill-posed problems in Hilbert spaces we introduce an adaptive procedure to recover the unknown solution from indirect discrete and noisy data. This procedure is shown to be order optimal for a large class of problems. Smoothness of the solution is measured in terms of general source conditions. The concept of operator monotone functions turns out to be an important tool for the analysis.
947.
This paper studies the stability and boundedness of the solutions of Volterra integral differential equations with infinite delay in the phase space (Ch, |·|h), the h-uniform stability, h-uniformly asymptotic stability and h-boundedness of solutions are obtained. 相似文献
948.
Wengu Chen Yixin Lai 《分析论及其应用》2006,22(2):195-200
Let μ be a Borel measure on Rd which may be non doubling. The only condition that μ must satisfy is μ(Q) ≤ col(Q)n for any cube Q () Rd with sides parallel to the coordinate axes and for some fixed n with 0 < n ≤ d. The purpose of this paper is to obtain a boundedness property of fractional integrals in Hardy spaces H1 (μ). 相似文献
949.
Blow Up of Solutions to Semilinear Wave Equations with Critical Exponent in High Dimensions 总被引:5,自引:2,他引:3 下载免费PDF全文
Yi ZHOU 《数学年刊B辑(英文版)》2007,28(2):205-212
In this paper, the author considers the Cauchy problem for semilinear wave equations with critical exponent in n≥4 space dimensions. Under some positivity conditions on the initial data, it is proved that there can be no global solutions no matter how small the initial data are. 相似文献
950.
The category of small covariant functors from simplicial sets to simplicial sets supports the projective model structure [B. Chorny, W.G. Dwyer, Homotopy theory of small diagrams over large categories, preprint, 2005]. In this paper we construct various localizations of the projective model structure and also give a variant for functors from simplicial sets to spectra. We apply these model categories in the study of calculus of functors, namely for a classification of polynomial and homogeneous functors. In the n-homogeneous model structure, the nth derivative is a Quillen functor to the category of spectra with Σn-action. After taking into account only finitary functors—which may be done in two different ways—the above Quillen map becomes a Quillen equivalence. This improves the classification of finitary homogeneous functors by T.G. Goodwillie [T.G. Goodwillie, Calculus. III. Taylor series, Geom. Topol. 7 (2003) 645-711 (electronic)]. 相似文献