全文获取类型
收费全文 | 16902篇 |
免费 | 1609篇 |
国内免费 | 1233篇 |
专业分类
化学 | 4349篇 |
晶体学 | 51篇 |
力学 | 1470篇 |
综合类 | 327篇 |
数学 | 9335篇 |
物理学 | 4212篇 |
出版年
2024年 | 35篇 |
2023年 | 165篇 |
2022年 | 255篇 |
2021年 | 321篇 |
2020年 | 427篇 |
2019年 | 437篇 |
2018年 | 405篇 |
2017年 | 491篇 |
2016年 | 578篇 |
2015年 | 421篇 |
2014年 | 738篇 |
2013年 | 1270篇 |
2012年 | 693篇 |
2011年 | 890篇 |
2010年 | 856篇 |
2009年 | 959篇 |
2008年 | 1059篇 |
2007年 | 1113篇 |
2006年 | 968篇 |
2005年 | 890篇 |
2004年 | 720篇 |
2003年 | 727篇 |
2002年 | 776篇 |
2001年 | 587篇 |
2000年 | 521篇 |
1999年 | 452篇 |
1998年 | 454篇 |
1997年 | 340篇 |
1996年 | 344篇 |
1995年 | 288篇 |
1994年 | 210篇 |
1993年 | 204篇 |
1992年 | 169篇 |
1991年 | 153篇 |
1990年 | 86篇 |
1989年 | 88篇 |
1988年 | 75篇 |
1987年 | 62篇 |
1986年 | 68篇 |
1985年 | 69篇 |
1984年 | 55篇 |
1983年 | 32篇 |
1982年 | 52篇 |
1981年 | 58篇 |
1980年 | 38篇 |
1979年 | 43篇 |
1978年 | 31篇 |
1977年 | 19篇 |
1976年 | 16篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
11.
曾六川 《高等学校计算数学学报(英文版)》2003,12(1)
The purpose of this paper is to investigate the problem of approximating fixed points of non-Lipschitizian asymptotically pseudocontractive mappings in an arbitrary real Banach space by the modified Ishikawa iterative sequences with errors. 相似文献
12.
We derive a test problem for evaluating the ability of time-steppingmethods to preserve the statistical properties of systems inmolecular dynamics. We consider a family of deterministic systemsconsisting of a finite number of particles interacting on acompact interval. The particles are given random initial conditionsand interact through instantaneous energy- and momentum-conservingcollisions. As the number of particles, the particle density,and the mean particle speed go to infinity, the trajectory ofa tracer particle is shown to converge to a stationary Gaussianstochastic process. We approximate this system by one describedby a system of ordinary differential equations and provide numericalevidence that it converges to the same stochastic process. Wesimulate the latter system with a variety of numerical integrators,including the symplectic Euler method, a fourth-order Runge-Kuttamethod, and an energyconserving step-and-project method. Weassess the methods' ability to recapture the system's limitingstatistics and observe that symplectic Euler performs significantlybetter than the others for comparable computational expense. 相似文献
13.
14.
In this paper, we study the stability conditions of the MMAP[K]/G[K]/1/LCFS preemptive repeat queue. We introduce an embedded Markov chain of matrix M/G/1 type with a tree structure and identify conditions for the Markov chain to be ergodic. First, we present three conventional methods for the stability problem of the queueing system of interest. These methods are either computationally demanding or do not provide accurate information for system stability. Then we introduce a novel approach that develops two linear programs whose solutions provide sufficient conditions for stability or instability of the queueing system. The new approach is numerically efficient. The advantages and disadvantages of the methods introduced in this paper are analyzed both theoretically and numerically. 相似文献
15.
Mean value in invexity analysis 总被引:1,自引:0,他引:1
In this paper, a generalization of the mean value theorem is considered in the case of functions defined on an invex set with respect to η (which is not necessarily connected). 相似文献
16.
反对称正交对称矩阵反问题 总被引:6,自引:0,他引:6
本文讨论一类反对称正交对称矩阵反问题及其最佳逼近.研究了这类矩阵的一些性质,利用这些性质给出了反问题解存在的一些条件和解的一般表达式,不仅证明了最佳逼近解的存在唯一性,而且给出了此解的具体表达式. 相似文献
17.
Yao Ping HOU 《数学学报(英文版)》2005,21(4):955-960
A signed graph is a graph with a sign attached to each edge. This paper extends some fundamental concepts of the Laplacian matrices from graphs to signed graphs. In particular, the relationships between the least Laplacian eigenvalue and the unbalancedness of a signed graph are investigated. 相似文献
18.
The projective method for solving linear matrix inequalities 总被引:2,自引:0,他引:2
Numerous problems in control and systems theory can be formulated in terms of linear matrix inequalities (LMI). Since solving
an LMI amounts to a convex optimization problem, such formulations are known to be numerically tractable. However, the interest
in LMI-based design techniques has really surged with the introduction of efficient interior-point methods for solving LMIs
with a polynomial-time complexity. This paper describes one particular method called the Projective Method. Simple geometrical
arguments are used to clarify the strategy and convergence mechanism of the Projective algorithm. A complexity analysis is
provided, and applications to two generic LMI problems (feasibility and linear objective minimization) are discussed. 相似文献
19.
20.
The phase behavior of binary blends of poly(ether ether ketone) (PEEK), sulfonated PEEK, and sulfamidated PEEK with aromatic polyimides is reported. PEEK was determined to be immiscible with a poly(amide imide) (TORLON 4000T). Blends of sulfonated and sulfamidated PEEK with this poly(amide imide), however, are reported here to be miscible in all proportions. Blends of sulfonated PEEK and a poly(ether imide) (ULTEM 1000) are also reported to be miscible. Spectroscopic investigations of the intermolecular interactions suggest that formation of electron donoracceptor complexes between the sulfonated/sulfamidated phenylene rings of the PEEKs and the n-phenylene units of the polyimides are responsible for this miscibility. © 1993 John Wiley & Sons, Inc. 相似文献