全文获取类型
收费全文 | 3898篇 |
免费 | 133篇 |
国内免费 | 215篇 |
专业分类
化学 | 285篇 |
晶体学 | 2篇 |
力学 | 189篇 |
综合类 | 26篇 |
数学 | 2681篇 |
物理学 | 1063篇 |
出版年
2024年 | 5篇 |
2023年 | 31篇 |
2022年 | 70篇 |
2021年 | 55篇 |
2020年 | 94篇 |
2019年 | 101篇 |
2018年 | 99篇 |
2017年 | 88篇 |
2016年 | 79篇 |
2015年 | 54篇 |
2014年 | 194篇 |
2013年 | 323篇 |
2012年 | 122篇 |
2011年 | 203篇 |
2010年 | 185篇 |
2009年 | 270篇 |
2008年 | 304篇 |
2007年 | 252篇 |
2006年 | 193篇 |
2005年 | 148篇 |
2004年 | 115篇 |
2003年 | 126篇 |
2002年 | 117篇 |
2001年 | 81篇 |
2000年 | 84篇 |
1999年 | 87篇 |
1998年 | 92篇 |
1997年 | 83篇 |
1996年 | 74篇 |
1995年 | 46篇 |
1994年 | 50篇 |
1993年 | 36篇 |
1992年 | 42篇 |
1991年 | 37篇 |
1990年 | 24篇 |
1989年 | 36篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 30篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1973年 | 6篇 |
排序方式: 共有4246条查询结果,搜索用时 31 毫秒
1.
2.
Multi-sensor data fusion is an evolving technology whereby data from multiple sensor inputs are processed and combined. The data derived from multiple sensors can, however, be uncertain, imperfect, and conflicting. The present study is undertaken to help contribute to the continuous search for viable approaches to overcome the problems associated with data conflict and imperfection. Sensor readings, represented by belief functions, have to be fused according to their corresponding weights. Previous studies have often estimated the weights of sensor readings based on a single criterion. Mono-criteria approaches for the assessment of sensor reading weights are, however, often unreliable and inadequate for the reflection of reality. Accordingly, this work opts for the use of a multi-criteria decision aid. A modified Analytical Hierarchy Process (AHP) that incorporates several criteria is proposed to determine the weights of a sensor reading set. The approach relies on the automation of pairwise comparisons to eliminate subjectivity and reduce inconsistency. It assesses the weight of each sensor reading, and fuses the weighed readings obtained using a modified average combination rule. The efficiency of this approach is evaluated in a target recognition context. Several tests, sensitivity analysis, and comparisons with other approaches available in the literature are described. 相似文献
3.
Lu Chuanrong 《数学年刊B辑(英文版)》1997,18(1):71-78
Let $\{\xi_{\bold t}, {\bold t}
\in {\bold Z}^d\}$ be a nonuniform $\varphi$-mixing strictly stationary
real random field with
$E\xi_{\bold 0}=0, E|\xi_{\bold 0}|^{2+\delta}<\infty$ for some
$0<\delta<1$. A sufficient
condition is given for the sequence of partial sum set-indexed process
$\{Z_n(A),\ A\in \Cal A\}$ to converge to Brownian motion. By a direct
calculation, the author shows
that the result holds for a more general class of set index ${\Cal A}$, where
${\Cal A}$ is assumed only to have the metric entropy exponent $r, 0相似文献
4.
Agnieszka Kaamajska 《Mathematical Methods in the Applied Sciences》2006,29(11):1307-1325
The weak limits of sequences {f(uν)}ν∈? where uν's are vector‐valued µ‐measurable functions defined on a compact set Ω and f is (possibly) discontinuous are investigated. As shown by the author (J. Conv. Anal. (to appear)), they are described in terms of integral formulae involving parametrized measures independent of f, similarly as in the classical theorem by Young and its generalization due to DiPerna and Majda. In the present paper we describe the supports of the involved parametrized measures. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
5.
6.
We study the induced measure obtained from a 1-step Markov measure, supported by a topological Markov chain, after the mapping of the original alphabet onto another one. We give sufficient conditions for the induced measure to be a Gibbs measure (in the sense of Bowen) when the factor system is again a topological Markov chain. This amounts to constructing, when it does exist, the induced potential and proving its Hölder continuity. This is achieved through a matrix method. We provide examples and counterexamples to illustrate our results. 相似文献
7.
On the average complexity of 3D-Voronoi diagrams of random points on convex polytopes 总被引:1,自引:0,他引:1
It is well known that the complexity, i.e. the number of vertices, edges and faces, of the 3-dimensional Voronoi diagram of n points can be as bad as Θ(n2). It is also known that if the points are chosen Independently Identically Distributed uniformly from a 3-dimensional region such as a cube or sphere, then the expected complexity falls to O(n). In this paper we introduce the problem of analyzing what occurs if the points are chosen from a 2-dimensional region in 3-dimensional space. As an example, we examine the situation when the points are drawn from a Poisson distribution with rate n on the surface of a convex polytope. We prove that, in this case, the expected complexity of the resulting Voronoi diagram is O(n). 相似文献
8.
Abstract. We propose a general approach to deal with nonlinear, nonconvex variational problems based on a reformulation of the problem
resulting in an optimization problem with linear cost functional and convex constraints. As a first step we explicitly explore
these ideas to some one-dimensional variational problems and obtain specific conclusions of an analytical and numerical nature. 相似文献
9.
Random copolymers of poly{(methacrylamide)-co-(vinyl trimethoxysilane)} and poly{(methacrylic acid)-co-(vinyl trimethoxysilane)} were synthesized via a free radical polymerization reaction. Acid catalyzed sol-gel process of tetraethylorthosilicate (TEOS) with aforementioned polymers in the presence of methyl xanthine class of alkaloid like caffeine resulted in the formation of highly transparent monoliths. Solvent extraction of the template leaves behind the recognition sites intact with high selectivity towards the print molecule. The ionic and non-specific adsorptions, which are considered to be the main disadvantages of the molecularly imprinted polymers (MIP), are prevented to a considerable extent by the end capping of surface silanol groups. The template binding efficiencies of MIP were determined by HPLC analysis. 相似文献
10.
Hans TRIEBEL 《应用数学学报(英文版)》2004,(4)
The paper deals with multifractal quantities for some types of Radon measures,especiallyself-similar probability measures,and their relations to Besov spaces. 相似文献