全文获取类型
收费全文 | 15633篇 |
免费 | 1739篇 |
国内免费 | 1213篇 |
专业分类
化学 | 3374篇 |
晶体学 | 71篇 |
力学 | 1440篇 |
综合类 | 350篇 |
数学 | 8529篇 |
物理学 | 4821篇 |
出版年
2024年 | 38篇 |
2023年 | 143篇 |
2022年 | 277篇 |
2021年 | 333篇 |
2020年 | 439篇 |
2019年 | 444篇 |
2018年 | 412篇 |
2017年 | 463篇 |
2016年 | 600篇 |
2015年 | 427篇 |
2014年 | 733篇 |
2013年 | 1381篇 |
2012年 | 740篇 |
2011年 | 911篇 |
2010年 | 815篇 |
2009年 | 956篇 |
2008年 | 952篇 |
2007年 | 974篇 |
2006年 | 877篇 |
2005年 | 848篇 |
2004年 | 726篇 |
2003年 | 700篇 |
2002年 | 650篇 |
2001年 | 507篇 |
2000年 | 487篇 |
1999年 | 397篇 |
1998年 | 365篇 |
1997年 | 321篇 |
1996年 | 252篇 |
1995年 | 229篇 |
1994年 | 172篇 |
1993年 | 153篇 |
1992年 | 136篇 |
1991年 | 127篇 |
1990年 | 74篇 |
1989年 | 76篇 |
1988年 | 61篇 |
1987年 | 40篇 |
1986年 | 53篇 |
1985年 | 49篇 |
1984年 | 40篇 |
1983年 | 18篇 |
1982年 | 35篇 |
1981年 | 26篇 |
1980年 | 21篇 |
1979年 | 27篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 12篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
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
4.
V. V. Sagaradze N. V. Kataeva V. A. Zavalishin K. A. Kozlov V. V. Makarov A. R. Kuznetsov 《哲学杂志》2020,100(14):1868-1879
ABSTRACT The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti. 相似文献
5.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation with the critical situation that on g and p, where , is periodic and is bounded. 相似文献
6.
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
7.
对由一类非线性抛物型变分不等方程所描述的无穷维动力系统,给出了存在全局吸引子及弱近似惯性流形的充分条件. 相似文献
8.
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
9.
10.
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