全文获取类型
收费全文 | 6125篇 |
免费 | 718篇 |
国内免费 | 639篇 |
专业分类
化学 | 1443篇 |
晶体学 | 40篇 |
力学 | 348篇 |
综合类 | 130篇 |
数学 | 3461篇 |
物理学 | 2060篇 |
出版年
2024年 | 14篇 |
2023年 | 87篇 |
2022年 | 148篇 |
2021年 | 166篇 |
2020年 | 208篇 |
2019年 | 182篇 |
2018年 | 191篇 |
2017年 | 205篇 |
2016年 | 236篇 |
2015年 | 155篇 |
2014年 | 288篇 |
2013年 | 527篇 |
2012年 | 280篇 |
2011年 | 365篇 |
2010年 | 305篇 |
2009年 | 346篇 |
2008年 | 383篇 |
2007年 | 428篇 |
2006年 | 336篇 |
2005年 | 320篇 |
2004年 | 261篇 |
2003年 | 262篇 |
2002年 | 276篇 |
2001年 | 215篇 |
2000年 | 199篇 |
1999年 | 174篇 |
1998年 | 168篇 |
1997年 | 123篇 |
1996年 | 109篇 |
1995年 | 96篇 |
1994年 | 85篇 |
1993年 | 63篇 |
1992年 | 48篇 |
1991年 | 28篇 |
1990年 | 34篇 |
1989年 | 26篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 22篇 |
1985年 | 23篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有7482条查询结果,搜索用时 15 毫秒
71.
Norman Biggs 《Journal of Combinatorial Theory, Series B》2004,92(2):359
An explicit formula for the chromatic polynomials of certain families of graphs, called bracelets', is obtained. The terms correspond to irreducible representations of symmetric groups. The theory is developed using the standard bases for the Specht modules of representation theory, and leads to an effective means of calculation. 相似文献
72.
Richard Arratia Bla Bollobs Gregory B. Sorkin 《Journal of Combinatorial Theory, Series B》2004,92(2):199-233
Motivated by circle graphs, and the enumeration of Euler circuits, we define a one-variable “interlace polynomial” for any graph. The polynomial satisfies a beautiful and unexpected reduction relation, quite different from the cut and fuse reduction characterizing the Tutte polynomial.It emerges that the interlace graph polynomial may be viewed as a special case of the Martin polynomial of an isotropic system, which underlies its connections with the circuit partition polynomial and the Kauffman brackets of a link diagram. The graph polynomial, in addition to being perhaps more broadly accessible than the Martin polynomial for isotropic systems, also has a two-variable generalization that is unknown for the Martin polynomial. We consider extremal properties of the interlace polynomial, its values for various special graphs, and evaluations which relate to basic graph properties such as the component and independence numbers. 相似文献
73.
Wenping Deng Gang Xu Lei Wan Anwen Liu Bo Gao Junhe Du Shuiming Hu Yang Chen 《Acta Physico》2008,24(8):1329-1334
Apparatus integrating a Fourier transform-infrared (FT-IR) spectrometer and a mid-infrared difference frequency generation (DFG) laser spectrometer was built for the study of the matrix isolation spectrum in solid molecular hydrogen. A 3-cm-long molecular hydrogen crystal was grown in a liquid-helium Dewar, and its infrared absorption spectrum in the 1-5 μm region was recorded to test the system. The W0(0) (ν=0←0, J=6←0) line around 2410 cm−1 of solid hydrogen was investigated with the DFG laser spectroscopy. High-resolution matrix isolation spectrum of CO2 co-deposited with hydrogen on a BaF2 cold plate at liquid-helium temperature was studied. 相似文献
74.
Ioan Tomescu 《Journal of Graph Theory》2003,43(3):210-222
In the set of graphs of order n and chromatic number k the following partial order relation is defined. One says that a graph G is less than a graph H if ci(G) ≤ ci(H) holds for every i, k ≤ i ≤ n and at least one inequality is strict, where ci(G) denotes the number of i‐color partitions of G. In this paper the first ? n/2 ? levels of the diagram of the partially ordered set of connected 3‐chromatic graphs of order n are described. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 210–222, 2003 相似文献
75.
Summary By employing a novel idea and simple techniques, we substantially generalize the Turán type inequality for rational functions
with real zeros and prescribed poles established by Min [5] to include Lpspaces for 1≤p≤∞<span style='font-size:10.0pt'>while loosing the restriction ρ > 2 at the same time. 相似文献
76.
77.
SINGLE MACHINE SCHEDULING WITH CONTROLLABLE PROCESSING TIMES AND COMPRESSION COSTS (PART I:EQUAL TIMES AND COSTS) 总被引:1,自引:0,他引:1
Most papers in scheduling research have treated individual job processing times as fixed parameters. However, in many practical situations, a manager may control processing time by realloeating resources. In this paper, authors consider a machine scheduling problemwith controllable processing times. In the first part of this paper, a special case where the pro-cessing times and compression costs are uniform among jobs is discussed. Theoretical results are derived that aid in developing an O(n^2) algorithm to slove the problem optimally. In the second part of this paper, authors generalize the discussion to general case, An effective heuristic to the genera/ problem will be presented. 相似文献
78.
卢琳璋 《高等学校计算数学学报(英文版)》1994,(1)
The unit circle problem is the problem of finding the number of eigenvalues of a non-Hermitian matrix inside and outside the unit circle . To reduce the cost of computing eigenvalues for the problem, a direct method, which is analogous to that given in [5], is proposed in this paper. 相似文献
79.
Numerous versions of the Lanczos τ-methods have been extensively used to produce polynomial approximations for functions verifying
a linear differential equation with polynomial coefficients. In the case of an initial-value problem, an adapted τ-method
based on Chebyshev series and the use of symbolic computation lead to a rational approximation of the solution on a region
of the complex plane. Numerical examples show that the simplicity of the method does not prevent a high accuracy of results.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
80.
Pierre L'Ecuyer 《Annals of Operations Research》1994,53(1):77-120
In typical stochastic simulations, randomness is produced by generating a sequence of independent uniform variates (usually real-valued between 0 and 1, or integer-valued in some interval) and transforming them in an appropriate way. In this paper, we examine practical ways of generating (deterministic approximations to) such uniform variates on a computer. We compare them in terms of ease of implementation, efficiency, theoretical support, and statistical robustness. We look in particular at several classes of generators, such as linear congruential, multiple recursive, digital multistep, Tausworthe, lagged-Fibonacci, generalized feedback shift register, matrix, linear congruential over fields of formal series, and combined generators, and show how all of them can be analyzed in terms of their lattice structure. We also mention other classes of generators, like non-linear generators, discuss other kinds of theoretical and empirical statistical tests, and give a bibliographic survey of recent papers on the subject. 相似文献