全文获取类型
收费全文 | 11345篇 |
免费 | 657篇 |
国内免费 | 901篇 |
专业分类
化学 | 246篇 |
力学 | 527篇 |
综合类 | 118篇 |
数学 | 10678篇 |
物理学 | 1334篇 |
出版年
2024年 | 16篇 |
2023年 | 135篇 |
2022年 | 154篇 |
2021年 | 148篇 |
2020年 | 253篇 |
2019年 | 294篇 |
2018年 | 246篇 |
2017年 | 288篇 |
2016年 | 248篇 |
2015年 | 241篇 |
2014年 | 525篇 |
2013年 | 1017篇 |
2012年 | 473篇 |
2011年 | 645篇 |
2010年 | 561篇 |
2009年 | 785篇 |
2008年 | 848篇 |
2007年 | 800篇 |
2006年 | 664篇 |
2005年 | 598篇 |
2004年 | 474篇 |
2003年 | 500篇 |
2002年 | 369篇 |
2001年 | 334篇 |
2000年 | 293篇 |
1999年 | 289篇 |
1998年 | 274篇 |
1997年 | 272篇 |
1996年 | 195篇 |
1995年 | 126篇 |
1994年 | 115篇 |
1993年 | 80篇 |
1992年 | 75篇 |
1991年 | 67篇 |
1990年 | 39篇 |
1989年 | 35篇 |
1988年 | 38篇 |
1987年 | 21篇 |
1986年 | 32篇 |
1985年 | 56篇 |
1984年 | 33篇 |
1983年 | 26篇 |
1982年 | 30篇 |
1981年 | 38篇 |
1980年 | 30篇 |
1979年 | 29篇 |
1978年 | 28篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
无界区域R1上推广的B-BBM方程的整体吸引子 总被引:4,自引:0,他引:4
本文研究了无界区域R^1上推广的B—BBM方程的长时间动力学行为,证明了该方程整体吸引子的存在性. 相似文献
82.
利用集值映射不动点定理及最优化问题与变分不等式的关系给出线性G^↑ateaux可微的锥凸映射的广义有效点的一个存在性定理。 相似文献
83.
Several sophisticated methods to solution of symmetry specified enumeration problems are available in the modern literature.
In this paper we propose a simple technique that allows one to manually compute the exact numbers of fixed-symmetry derivatives
for a given structure either with inclusion or ignoring the substitution patterns. The basic idea of the method suggested
consists in the derivation of Pólya-like cycle indices for the automorphism groups of specially constructed orbit partition
graphs; the expansion of these indices and subsequent simple calculations result in the desired numbers of substituted derivatives
with achiral substituents. Limitations of the new technique (and a method suggested earlier) depend on the relevance of the
orbit partitions for particular subgroups of the point symmetry group. For illustration purposes, the results obtained for
the prismane (D
3h
) and adamantane (T
d
) structures are discussed. In the former case the numbers of substituted derivatives can be found for all subgroups of the
D
3h
group, whereas in the latter case these numbers can be determined for eight out of eleven subgroups of the T
d
point symmetry group.
This work is based on the text of the lecture presented by the authors at the 5th All-Russia Conference on Molecular Modeling
(Moscow, April 2007). The paper deals with the methodology and detailed treatment of applied aspects related to solution of
enumeration problems for substituted derivatives with prescribed symmetry groups. Unlike the known methods of symmetry specified
enumeration, the technique suggested is simple enough and may be regarded as generalization of the Pólya methodology, which
is widely used by chemists.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 227–245, February, 2008. 相似文献
84.
Enrique Casanovas 《Mathematical Logic Quarterly》2003,49(5):475-478
We prove a property of generic homogeneity of tuples starting an infinite indiscernible sequence in a simple theory and we use it to give a shorter proof of the Independence Theorem for Lascar strong types. We also characterize the relation of starting an infinite indiscernible sequence in terms of coheirs. 相似文献
85.
The authors establish the Hilbertian invariance principle for the empirical process of a stationary Markov process, by extending the forward-backward martingale decomposition of Lyons-Meyer-Zheng to the Hilbert space valued additive functionals associated with general non-reversible Markov processes. 相似文献
86.
Eero Immonen 《Journal of Mathematical Analysis and Applications》2004,300(1):79-101
In this article, we study the effect of the chosen representation of a point value (and point evaluation) on the class of periodic signals realizable using a certain type of infinite-dimensional linear system. By suitably representing the point evaluation at the origin in a Hilbert space, we are able to give a complete characterization of its extensions. These extensions involve a new concept called δ-sequence, the use of which as an observation operator of an infinite-dimensional linear system is studied in this article. In particular, we consider their use in the realization of periodic signals. We also investigate how the use of δ-sequences affects the convergence properties of such realizations; we consider the rate and character of convergence and the removal of the Gibbs phenomenon. As still a further demonstration of the significance of the chosen concept of a point value, we discuss the use of distributional point values in the realization of periodic distributions. The possible applications of this work lie in regulator problems of infinite-dimensional control theory, as is indicated by the well-known internal model principle. 相似文献
87.
Johan van Benthem 《Logica Universalis》2007,1(1):125-138
We prove new Lindstr?m theorems for the basic modal propositional language, and for some related fragments of first-order
logic. We find difficulties with such results for modal languages without a finite-depth property, high-lighting the difference
between abstract model theory for fragments and for extensions of first-order logic. In addition we discuss new connections
with interpolation properties, and the modal invariance theorem.
Mathematics Subject Classification (2000): Primary 03B45; Secondary 03C95 相似文献
88.
本文讨论了在区域提纯过程中,研究液态金属流的表面张力时提出的一个带有非负参数Q的两点边值问题.利用上、下解方法和Schauder不动点定理,证明了当0Q851时,该问题至少有一个解,对已有结果0Q<1进行了重要的改进. 相似文献
89.
90.
Pedro J. Torres 《Journal of Differential Equations》2007,232(1):277-284
In a periodically forced semilinear differential equation with a singular nonlinearity, a weak force condition enables the achievement of new existence criteria through a basic application of Schauder's fixed point theorem. The originality of the arguments relies in that, contrary to the customary situation in the available references, a weak singularity facilitates the arguments of the proofs. 相似文献