全文获取类型
收费全文 | 10583篇 |
免费 | 1057篇 |
国内免费 | 779篇 |
专业分类
化学 | 2152篇 |
晶体学 | 27篇 |
力学 | 810篇 |
综合类 | 236篇 |
数学 | 6599篇 |
物理学 | 2595篇 |
出版年
2024年 | 20篇 |
2023年 | 114篇 |
2022年 | 166篇 |
2021年 | 228篇 |
2020年 | 282篇 |
2019年 | 288篇 |
2018年 | 266篇 |
2017年 | 319篇 |
2016年 | 417篇 |
2015年 | 266篇 |
2014年 | 506篇 |
2013年 | 933篇 |
2012年 | 455篇 |
2011年 | 627篇 |
2010年 | 566篇 |
2009年 | 629篇 |
2008年 | 655篇 |
2007年 | 689篇 |
2006年 | 593篇 |
2005年 | 557篇 |
2004年 | 484篇 |
2003年 | 472篇 |
2002年 | 433篇 |
2001年 | 347篇 |
2000年 | 321篇 |
1999年 | 272篇 |
1998年 | 259篇 |
1997年 | 198篇 |
1996年 | 183篇 |
1995年 | 148篇 |
1994年 | 100篇 |
1993年 | 93篇 |
1992年 | 85篇 |
1991年 | 81篇 |
1990年 | 41篇 |
1989年 | 46篇 |
1988年 | 34篇 |
1987年 | 22篇 |
1986年 | 32篇 |
1985年 | 30篇 |
1984年 | 25篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 7篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
G. Peruginelli 《代数通讯》2018,46(11):4724-4738
We classify the maximal subrings of the ring of n×n matrices over a finite field, and show that these subrings may be divided into three types. We also describe all of the maximal subrings of a finite semisimple ring, and categorize them into two classes. As an application of these results, we calculate the covering number of a finite semisimple ring. 相似文献
3.
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
4.
Recent Progress in the $L_p$ Theory for Elliptic and Parabolic Equations with Discontinuous Coefficients
下载免费PDF全文
![点击此处可从《分析论及其应用》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hongjie Dong 《分析论及其应用》2020,36(2):161-199
In this paper, we review some results over the last 10-15 years on elliptic and parabolic equations with discontinuous coefficients. We begin with an approach given by N. V. Krylov to parabolic equations in the whole space with $\rm{VMO}_x$ coefficients. We then discuss some subsequent development including elliptic and parabolic equations with coefficients which are allowed to be merely measurable in one or two space directions, weighted $L_p$estimates with Muckenhoupt ($A_p$) weights, non-local elliptic and parabolic equations, as well as fully nonlinear elliptic and parabolic equations. 相似文献
5.
In this paper, we study the existence of the uniformly minimum risk equivariant (UMRE) estimators of parameters in a class
of normal linear models, which include the normal variance components model, the growth curve model, the extended growth curve
model, and the seemingly unrelated regression equations model, and so on. The necessary and sufficient conditions are given
for the existence of UMRE estimators of the estimable linear functions of regression coefficients, the covariance matrixV and (trV)α, where α > 0 is known, in the models under an affine group of transformations for quadratic losses and matrix losses, respectively.
Under the (extended) growth curve model and the seemingly unrelated regression equations model, the conclusions given in literature
for estimating regression coefficients can be derived by applying the general results in this paper, and the sufficient conditions
for non-existence of UMRE estimators ofV and tr(V) are expanded to be necessary and sufficient conditions. In addition, the necessary and sufficient conditions that there
exist UMRE estimators of parameters in the variance components model are obtained for the first time. 相似文献
6.
施国勇 《宁波大学学报(理工版)》1998,(2)
提出了一个线性双向联想存储器的模型,一组有限个向量对由一线性算子建立起双向联想关系,此线性算于是一个网络的联结权重矩阵。该权矩阵由最小二乘法决定。由权矩阵的解导出一特殊类型的Lyapunov矩阵方程.本文提供了这种Lyapunov矩阵方程的解。 相似文献
7.
本文是文[1-7]的继续,研究变权综合问题,从确定变权的经验公式入手引出了变权原理,给出了变权的公理化定义,讨论了与之有关的均衡函数及其梯度向量。 相似文献
8.
9.
Algebra matrix and similarity classification of operators 总被引:1,自引:0,他引:1
ZHANG Zilong & LI Yucheng Department of Mathematics Hebei Normal University Shijiazhuang China 《中国科学A辑(英文版)》2006,49(3):398-409
In this paper, by the Gelfand representation theory and the Silov idempotents theorem, we first obtain a central decomposition theorem related to a unital semi-simple n-homogeneous Banach algebra, and then give a similarity classification of two strongly irreducible Cowen-Douglas operators using this theorem. 相似文献
10.