全文获取类型
收费全文 | 10404篇 |
免费 | 980篇 |
国内免费 | 865篇 |
专业分类
化学 | 3695篇 |
晶体学 | 57篇 |
力学 | 345篇 |
综合类 | 114篇 |
数学 | 5821篇 |
物理学 | 2217篇 |
出版年
2024年 | 9篇 |
2023年 | 95篇 |
2022年 | 174篇 |
2021年 | 264篇 |
2020年 | 288篇 |
2019年 | 285篇 |
2018年 | 241篇 |
2017年 | 343篇 |
2016年 | 388篇 |
2015年 | 310篇 |
2014年 | 521篇 |
2013年 | 940篇 |
2012年 | 540篇 |
2011年 | 586篇 |
2010年 | 520篇 |
2009年 | 635篇 |
2008年 | 704篇 |
2007年 | 718篇 |
2006年 | 536篇 |
2005年 | 479篇 |
2004年 | 382篇 |
2003年 | 392篇 |
2002年 | 393篇 |
2001年 | 356篇 |
2000年 | 309篇 |
1999年 | 274篇 |
1998年 | 211篇 |
1997年 | 195篇 |
1996年 | 138篇 |
1995年 | 133篇 |
1994年 | 132篇 |
1993年 | 104篇 |
1992年 | 101篇 |
1991年 | 91篇 |
1990年 | 39篇 |
1989年 | 53篇 |
1988年 | 50篇 |
1987年 | 39篇 |
1986年 | 30篇 |
1985年 | 45篇 |
1984年 | 37篇 |
1983年 | 21篇 |
1982年 | 28篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 25篇 |
1978年 | 16篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 734 毫秒
11.
We give a sheaf theoretic interpretation of Potts models with external magnetic field, in terms of constructible sheaves and their Euler characteristics. We show that the polynomial countability question for the hypersurfaces defined by the vanishing of the partition function is affected by changes in the magnetic field: elementary examples suffice to see non-polynomially countable cases that become polynomially countable after a perturbation of the magnetic field. The same recursive formula for the Grothendieck classes, under edge-doubling operations, holds as in the case without magnetic field, but the closed formulae for specific examples like banana graphs differ in the presence of magnetic field. We give examples of computation of the Euler characteristic with compact support, for the set of real zeros, and find a similar exponential growth with the size of the graph. This can be viewed as a measure of topological and algorithmic complexity. We also consider the computational complexity question for evaluations of the polynomial, and show both tractable and NP-hard examples, using dynamic programming. 相似文献
12.
Mitsuki Yamashita Yuna Kawasumi Yuki Tachibana Dr. Shinnosuke Horiuchi Dr. Koji Yamamoto Prof. Tetsuro Murahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(5):1212-1216
Although small cyclic- and open-chain unsaturated hydrocarbon anions such as cyclopentadienide and open-chain pentadienide are used as the strongly electron-donating auxiliary ligands for metal complexes, more extended π-conjugated unsaturated hydrocarbon anions have rarely been used in coordination chemistry, despite their potential ability to serve as the multiply bridging π-ligands for metal clusters. This work reports isolation of metal chain clusters bearing the multi-dentate, open-chain extended unsaturated hydrocarbon anion ligands. The extended open-chain π-conjugated polyenyl ligands could effectively stabilize oxidized palladium chains, including an unprecedented [Pd4]4+ chain. 相似文献
13.
14.
Lu Chuanrong 《数学年刊B辑(英文版)》1997,18(1):71-78
Let $\{\xi_{\bold t}, {\bold t}
\in {\bold Z}^d\}$ be a nonuniform $\varphi$-mixing strictly stationary
real random field with
$E\xi_{\bold 0}=0, E|\xi_{\bold 0}|^{2+\delta}<\infty$ for some
$0<\delta<1$. A sufficient
condition is given for the sequence of partial sum set-indexed process
$\{Z_n(A),\ A\in \Cal A\}$ to converge to Brownian motion. By a direct
calculation, the author shows
that the result holds for a more general class of set index ${\Cal A}$, where
${\Cal A}$ is assumed only to have the metric entropy exponent $r, 0相似文献
15.
A profit-maximizing supply chain network design model with demand choice flexibility 总被引:1,自引:0,他引:1
Zuo-Jun Max Shen 《Operations Research Letters》2006,34(6):673-682
We present a profit-maximizing supply chain design model in which a company has flexibility in determining which customers to serve. The company may lose a customer to competition if the price it charges is too high. We show the problem formulation and solution algorithm, and discuss computational results. 相似文献
16.
利用射影几何方法在小缺陷码中,NMDS码是链条件码;给出k维NμMDS(0μk-2)码满足链条件的一个充要条件与一些易判断的充分条件. 相似文献
17.
L. Aggoun 《Mathematical and Computer Modelling》2002,36(11-13)
In this paper, finite-dimensional recursive filters for space-time Markov random fields are derived. These filters can be used with the expectation maximization (EM) algorithm to yield maximum likelihood estimates of the parameters of the model. 相似文献
18.
19.
The annealing algorithm (Ref. 1) is modified to allow for noisy or imprecise measurements of the energy cost function. This is important when the energy cannot be measured exactly or when it is computationally expensive to do so. Under suitable conditions on the noise/imprecision, it is shown that the modified algorithm exhibits the same convergence in probability to the globally minimum energy states as the annealing algorithm (Ref. 2). Since the annealing algorithm will typically enter and exit the minimum energy states infinitely often with probability one, the minimum energy state visited by the annealing algorithm is usually tracked. The effect of using noisy or imprecise energy measurements on tracking the minimum energy state visited by the modified algorithms is examined.The research reported here has been supported under Contracts AFOSR-85-0227, DAAG-29-84-K-0005, and DAAL-03-86-K-0171 and a Purdue Research Initiation Grant. 相似文献
20.