全文获取类型
收费全文 | 13486篇 |
免费 | 820篇 |
国内免费 | 839篇 |
专业分类
化学 | 6548篇 |
晶体学 | 84篇 |
力学 | 763篇 |
综合类 | 146篇 |
数学 | 3101篇 |
物理学 | 4503篇 |
出版年
2023年 | 134篇 |
2022年 | 355篇 |
2021年 | 345篇 |
2020年 | 297篇 |
2019年 | 317篇 |
2018年 | 277篇 |
2017年 | 302篇 |
2016年 | 333篇 |
2015年 | 306篇 |
2014年 | 442篇 |
2013年 | 833篇 |
2012年 | 490篇 |
2011年 | 506篇 |
2010年 | 461篇 |
2009年 | 730篇 |
2008年 | 808篇 |
2007年 | 840篇 |
2006年 | 727篇 |
2005年 | 521篇 |
2004年 | 482篇 |
2003年 | 484篇 |
2002年 | 506篇 |
2001年 | 439篇 |
2000年 | 402篇 |
1999年 | 359篇 |
1998年 | 338篇 |
1997年 | 219篇 |
1996年 | 165篇 |
1995年 | 163篇 |
1994年 | 157篇 |
1993年 | 169篇 |
1992年 | 243篇 |
1991年 | 133篇 |
1990年 | 103篇 |
1989年 | 82篇 |
1988年 | 95篇 |
1987年 | 97篇 |
1986年 | 80篇 |
1985年 | 76篇 |
1984年 | 76篇 |
1983年 | 46篇 |
1982年 | 93篇 |
1981年 | 168篇 |
1980年 | 182篇 |
1979年 | 179篇 |
1978年 | 165篇 |
1977年 | 102篇 |
1976年 | 108篇 |
1973年 | 77篇 |
1972年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Fillmore在[1]中得到一个定理:设A,T是Banach空间X上的线性变换,A有界,若Lat(A) Lat(T)且AT=TA,则T是A的多项式.在本文里,以此作为引理,讨论了Banach空间上可逆线性变换A在什么情况下,A-1可表示为A的多项式.本文最主要的结论是定理3.4:设X是Banach空间,A是X上的有界线性变换,且可逆,则A-1是A的多项式当且仅当A-1是A的局部多项式. 相似文献
12.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
13.
Karl Gustafson 《Numerical Linear Algebra with Applications》2004,11(7):649-659
Given the operator product BA in which both A and B are symmetric positive‐definite operators, for which symmetric positive‐definite operators C is BA symmetric positive‐definite in the C inner product 〈x, y〉C? This question arises naturally in preconditioned iterative solution methods, and will be answered completely here. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
14.
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
15.
近年来,决定椭圆型方程系数反问题在地磁、地球物理、冶金和生物等实际问题上有着广泛的应用.本文讨论了二维的决定椭圆型方程系数反问题的数值求解方法.由误差平方和最小原则,这个反问题可化为一个变分问题,并进一步离散化为一个最优化问题,其目标函数依赖于要决定的方程系数.本文着重考察非线性共轭梯度法在此最优化问题数值计算中的表现,并与拟牛顿法作为对比.为了提高算法的效率我们适当选择加快收敛速度的预处理矩阵.同时还考察了线搜索方法的不同对优化算法的影响.数值实验的结果表明,非线性共轭梯度法在这类大规模优化问题中相对于拟牛顿法更有效. 相似文献
16.
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
17.
18.
Lahcne Mezrag 《Mathematische Nachrichten》2004,266(1):60-67
In [5], it is proved that a bounded linear operator u, from a Banach space Y into an Lp(S, ν) factors through Lp1 (S, ν) for some p1 > 1, if Y* is of finite cotype; (S, ν) is a probability space for p = 0, and any measure space for 0 < p < 1. In this paper, we generalize this result to uv, where u : Y → Lp(S, ν) and v : X → Y are linear operators such that v* is of finite Ka?in cotype. This result gives also a new proof of Grothendieck's theorem. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
A carousel is a dynamical system that describes the movement of an equilateral linkage in which the midpoint of each rod travels parallel to it. They are closely related to the floating body problem. We prove, using the work of Auerbach, that any figure that floats in equilibrium in every position is drawn by a carousel. Of special interest are such figures with rational perimetral density of the floating chords, which are then drawn by carousels. In particular, we prove that for some perimetral densities the only such figure is the circle, as the problem suggests. 相似文献
20.
胡迪鹤 《数学物理学报(B辑英文版)》2005,25(1):23-29
This paper is a continuation of [8]. In Section 1, three kinds of communication are introdnced for two states and the relations among them are investigated. In Section 2, two kinds of period of a state are introdnced and it is obtained that the period is a “class property” ,i.e. two states x and y belong to same class implies the period of x is equal to the period of y. 相似文献