全文获取类型
收费全文 | 6441篇 |
免费 | 545篇 |
国内免费 | 919篇 |
专业分类
化学 | 2690篇 |
晶体学 | 26篇 |
力学 | 470篇 |
综合类 | 85篇 |
数学 | 3553篇 |
物理学 | 1081篇 |
出版年
2024年 | 12篇 |
2023年 | 79篇 |
2022年 | 114篇 |
2021年 | 152篇 |
2020年 | 173篇 |
2019年 | 198篇 |
2018年 | 180篇 |
2017年 | 186篇 |
2016年 | 208篇 |
2015年 | 186篇 |
2014年 | 301篇 |
2013年 | 490篇 |
2012年 | 286篇 |
2011年 | 327篇 |
2010年 | 296篇 |
2009年 | 410篇 |
2008年 | 446篇 |
2007年 | 442篇 |
2006年 | 420篇 |
2005年 | 346篇 |
2004年 | 332篇 |
2003年 | 305篇 |
2002年 | 292篇 |
2001年 | 240篇 |
2000年 | 267篇 |
1999年 | 165篇 |
1998年 | 176篇 |
1997年 | 143篇 |
1996年 | 130篇 |
1995年 | 124篇 |
1994年 | 90篇 |
1993年 | 75篇 |
1992年 | 61篇 |
1991年 | 51篇 |
1990年 | 32篇 |
1989年 | 16篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有7905条查询结果,搜索用时 46 毫秒
41.
Thomas Wanner 《Transactions of the American Mathematical Society》2004,356(6):2251-2279
Many interesting and complicated patterns in the applied sciences are formed through transient pattern formation processes. In this paper we concentrate on the phenomenon of spinodal decomposition in metal alloys as described by the Cahn-Hilliard equation. This model depends on a small parameter, and one is generally interested in establishing sharp lower bounds on the amplitudes of the patterns as the parameter approaches zero. Recent results on spinodal decomposition have produced such lower bounds. Unfortunately, for higher-dimensional base domains these bounds are orders of magnitude smaller than what one would expect from simulations and experiments. The bounds exhibit a dependence on the dimension of the domain, which from a theoretical point of view seemed unavoidable, but which could not be observed in practice.
In this paper we resolve this apparent paradox. By employing probabilistic methods, we can improve the lower bounds for certain domains and remove the dimension dependence. We thereby obtain optimal results which close the gap between analytical methods and numerical observations, and provide more insight into the nature of the decomposition process. We also indicate how our results can be adapted to other situations.
42.
本文主要讨论了当非负位势 V(x)属于某逆Holder类时,由一致椭圆算子L=-div(A(x))+V(x)所定义的 Riesz变换在 Lp空间的有界性。 相似文献
43.
Lá szló L. Stachó Borut Zalar 《Proceedings of the American Mathematical Society》2004,132(10):3019-3025
We prove that every JB* triple with rank one bicircular projection is a direct sum of two ideals, one of which is isometrically isomorphic to a Hilbert space.
44.
代数$A$ 称为不可分解的,如果 $A$ 不能分解成理想的直和.文中将证明满足$C(L_{\bar{0}})=C(L)=\{0\}$的限制李超代数能够分解成不可分解限制理想的直和,这种分解在不计理想次序的前提下是唯一的.而且还证明了限制李超代数的一些结果. 相似文献
45.
S. Mentus Dijana Jelić Veselinka Grudić 《Journal of Thermal Analysis and Calorimetry》2007,90(2):393-397
Thermal decomposition of lanthanum nitrate to lanthanum oxide was carried out by both temperature programmed heating (TPH)
and citrate-gel combustion. The temperature programmed heating was carried out under flow of oxidizing (air), neutral (nitrogen)
and reducing (25 vol.% hydrogen+argone mixture) gases, and the processes were controlled by simultaneous thermogravimetry
and differential thermal analysis. It was shown that hydrogen atmosphere helps to reduce temperatures of all decomposition
steps. The results of TPH were utilized to check the nature of residues in the products of lanthanum nitrate-to-oxide conversion
performed via citrate-gel combustion technique. 相似文献
46.
Idealization of a decomposition theorem 总被引:1,自引:1,他引:0
In 1986, Tong [13] proved that a function f : (X,τ)→(Y,φ) is continuous if and only if it is α-continuous and A-continuous. We extend this decomposition of continuity in terms of ideals. First, we introduce the notions of regular-I-closed sets, A
I-sets and A
I -continuous functions in ideal topological spaces and investigate their properties. Then, we show that a function f : (X,τ,I)→(Y, φ) is continuous if and only if it is α-I-continuous and A
I-continuous.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
47.
Eric Flauraud Frdric Nataf Isabelle Faille Roland Masson 《Comptes Rendus Mecanique》2003,331(12):849-855
We present in this paper a domain decomposition method to treat faults in geological basin modeling. The particularity of this model is that the faults whose widths are very small in comparison with the basin size, are not characterized as subdomains any more but as interfaces between sedimentary blocks. The originality of this work lies in the formulation of this new fault model and in the definition and the computation of the interface conditions between the subdomains. To cite this article: E. Flauraud et al., C. R. Mecanique 331 (2003). 相似文献
48.
Tsuyoshi Katayama 《Queueing Systems》1992,11(3):299-306
This paper derives a conservation law for mean waiting times in a single-server multi-class service queueing system (M
X/G/1 type queue) with setup times which may be dependent on multiple customer classes and its arrival batch size by using the work decomposition property in the queueing system with vacations. 相似文献
49.
Jesús M. Velásquez Bermúdez 《Annals of Operations Research》2002,117(1-4):21-31
This document presents theoretical considerations about the solution of dynamic optimization problems integrating the Benders Theory, the Dynamic Programming approach and the concepts of Control Theory. The so called Generalized Dual Dynamic Programming Theory (GDDP) can be considered as an extension of two previous approaches known as Dual Dynamic Programming (DDP): The first is the work developed by Pereira and Pinto [3–5], which was revised by Velásquez and others [8,9]. The second is the work developed by Read and others [2,6,7]. 相似文献
50.
In this paper various ensemble learning methods from machine learning and statistics are considered and applied to the customer choice modeling problem. The application of ensemble learning usually improves the prediction quality of flexible models like decision trees and thus leads to improved predictions. We give experimental results for two real-life marketing datasets using decision trees, ensemble versions of decision trees and the logistic regression model, which is a standard approach for this problem. The ensemble models are found to improve upon individual decision trees and outperform logistic regression. 相似文献