全文获取类型
收费全文 | 7350篇 |
免费 | 781篇 |
国内免费 | 685篇 |
专业分类
化学 | 871篇 |
晶体学 | 34篇 |
力学 | 906篇 |
综合类 | 141篇 |
数学 | 4800篇 |
物理学 | 2064篇 |
出版年
2024年 | 9篇 |
2023年 | 93篇 |
2022年 | 191篇 |
2021年 | 166篇 |
2020年 | 242篇 |
2019年 | 225篇 |
2018年 | 220篇 |
2017年 | 267篇 |
2016年 | 240篇 |
2015年 | 172篇 |
2014年 | 303篇 |
2013年 | 574篇 |
2012年 | 353篇 |
2011年 | 454篇 |
2010年 | 387篇 |
2009年 | 550篇 |
2008年 | 533篇 |
2007年 | 497篇 |
2006年 | 433篇 |
2005年 | 404篇 |
2004年 | 330篇 |
2003年 | 304篇 |
2002年 | 266篇 |
2001年 | 223篇 |
2000年 | 207篇 |
1999年 | 192篇 |
1998年 | 206篇 |
1997年 | 155篇 |
1996年 | 118篇 |
1995年 | 72篇 |
1994年 | 62篇 |
1993年 | 50篇 |
1992年 | 50篇 |
1991年 | 42篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有8816条查询结果,搜索用时 15 毫秒
91.
Lingsheng Shi 《Journal of Graph Theory》2005,50(3):175-185
The Ramsey number R(G1,G2) of two graphs G1 and G2 is the least integer p so that either a graph G of order p contains a copy of G1 or its complement Gc contains a copy of G2. In 1973, Burr and Erd?s offered a total of $25 for settling the conjecture that there is a constant c = c(d) so that R(G,G)≤ c|V(G)| for all d‐degenerate graphs G, i.e., the Ramsey numbers grow linearly for d‐degenerate graphs. We show in this paper that the Ramsey numbers grow linearly for degenerate graphs versus some sparser graphs, arrangeable graphs, and crowns for example. This implies that the Ramsey numbers grow linearly for degenerate graphs versus graphs with bounded maximum degree, planar graphs, or graphs without containing any topological minor of a fixed clique, etc. © 2005 Wiley Periodicals, Inc. J Graph Theory 相似文献
92.
ZHANG Shu-min 《数学季刊》2004,(2)
In the paper, we prove that the complement of Tm(1,4,m - 6)(m > 10) is chromatically unique if and only if m ≠5k(k ≥ 2). 相似文献
93.
研究无原子布氏代数的计算复杂性 .得到了下面的新定理 :定理 1 无原子布氏代数理论Δ具有完全的量词消去法 ,也就是说每一个式子都Δ等价于一个开式子 .定理 2 无原子布氏代数的初等型Γ (x1,… ,xn)是由型内的不含量词的全体开式子所唯一决定 .定理 3 无原子布氏代数的一个长度为 n的语句的判断过程所消耗的 Turing时间和空间都是属于 2 2 cn指数级 . 相似文献
94.
R. Schuster H. Hajak M. Reinwald W. Wegscheider D. Schuh M. Bichler G. Abstreiter 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):236
The confinement energy of T-shaped quantum wires (QWRs), which were fabricated by the cleaved edge overgrowth technique in a way that the QWRs form at the intersection of In0.2Al0.8As stressor layers and the overgrown (1 1 0) GaAs quantum well (QW), is examined using micro-photoluminescence spectroscopy. Photoluminescence (PL) signals from individual QWRs can be spatially resolved, since the strained films are separated by 1 μm wide Al0.3Ga0.7As layers. We find that due to the tensile strain being transmitted to the QW, the confinement energy of the QWRs rises systematically up to 40 meV with increasing thickness of the stressor layers. By reducing the excitation power to 0.1 μW the QWR PL emission occurs 48 meV redshifted with respect to the QW. All QWR peaks exhibit smooth lineshapes, indicating the absence of pronounced exciton localization. 相似文献
95.
Let G = (V,E) be a graph or digraph and r : V → Z+. An r‐detachment of G is a graph H obtained by ‘splitting’ each vertex ν ∈ V into r(ν) vertices. The vertices ν1,…,νr(ν) obtained by splitting ν are called the pieces of ν in H. Every edge uν ∈ E corresponds to an edge of H connecting some piece of u to some piece of ν. Crispin Nash‐Williams 9 gave necessary and sufficient conditions for a graph to have a k‐edge‐connected r‐detachment. He also solved the version where the degrees of all the pieces are specified. In this paper, we solve the same problems for directed graphs. We also give a simple and self‐contained new proof for the undirected result. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 67–77, 2003 相似文献
96.
97.
利用第一类Chebyshev多项式的性质以及其与Lucas数的关系得到了关于Lucas数立方的一些恒等式. 相似文献
98.
99.
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
100.