全文获取类型
收费全文 | 1865篇 |
免费 | 101篇 |
国内免费 | 116篇 |
专业分类
化学 | 163篇 |
晶体学 | 2篇 |
力学 | 178篇 |
综合类 | 11篇 |
数学 | 1443篇 |
物理学 | 285篇 |
出版年
2024年 | 2篇 |
2023年 | 16篇 |
2022年 | 16篇 |
2021年 | 22篇 |
2020年 | 34篇 |
2019年 | 58篇 |
2018年 | 37篇 |
2017年 | 30篇 |
2016年 | 24篇 |
2015年 | 35篇 |
2014年 | 81篇 |
2013年 | 182篇 |
2012年 | 76篇 |
2011年 | 107篇 |
2010年 | 125篇 |
2009年 | 144篇 |
2008年 | 143篇 |
2007年 | 149篇 |
2006年 | 127篇 |
2005年 | 77篇 |
2004年 | 83篇 |
2003年 | 66篇 |
2002年 | 60篇 |
2001年 | 40篇 |
2000年 | 51篇 |
1999年 | 57篇 |
1998年 | 47篇 |
1997年 | 30篇 |
1996年 | 30篇 |
1995年 | 26篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1974年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有2082条查询结果,搜索用时 125 毫秒
101.
We consider Schrödinger operators with periodic potentials on periodic discrete graphs. The spectrum of the Schrödinger operator consists of an absolutely continuous part (a union of a finite number of non-degenerated bands) plus a finite number of flat bands, i.e., eigenvalues of infinite multiplicity. We obtain estimates of the Lebesgue measure of the spectrum in terms of geometric parameters of the graph and show that they become identities for some class of graphs. Moreover, we obtain stability estimates and show the existence and positions of large number of flat bands for specific graphs. The proof is based on the Floquet theory and the precise representation of fiber Schrödinger operators, constructed in the paper. 相似文献
102.
The dual model with diffusion is appropriate for companies with continuous expenses that are offset by stochastic and irregular gains. Examples include research-based or commission-based companies. In this context, Bayraktar et al. (2013a) show that a dividend barrier strategy is optimal when dividend decisions are made continuously. In practice, however, companies that are capable of issuing dividends make dividend decisions on a periodic (rather than continuous) basis.In this paper, we consider a periodic dividend strategy with exponential inter-dividend-decision times and continuous monitoring of solvency. Assuming hyperexponential gains, we show that a periodic barrier dividend strategy is the periodic strategy that maximizes the expected present value of dividends paid until ruin. Interestingly, a ‘liquidation-at-first-opportunity’ strategy is optimal in some cases where the surplus process has a positive drift. Results are illustrated. 相似文献
103.
104.
XU Yan-cong GENG Feng-jie 《高校应用数学学报(英文版)》2014,29(1):108-118
In this paper, the complicated dynamics is studied near a double homoclinic loops with bellows configuration for general systems. For the non-twisted multiple homoclinics, the existence of periodic orbit with the specified route and the existence of shift-invariant curve sequences defined on the cross sections of multiple homoclinics corresponding to any specified one-side infinite sequences are given. In addition, the existence regions are also located. 相似文献
105.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(9):2974-2982
For some abstract classes of nonlinear non-autonomous systems with variable and state-dependent delays existence, non-existence and multiplicity of periodic solutions are discussed. To illustrate the efficiency of the method, we obtain some well-known results for applied systems as corollaries of our existence theorems. 相似文献
106.
107.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(4):1088-1096
The dependence of stochastic resonance in the feed-forward-loop neuronal network motifs on the noise and time delay are studied in this paper. By computational modeling, Izhikevich neuron model with the chemical coupling is used to build the triple-neuron feed-forward-loop motifs with all possible motif types. Numerical results show that the correlation between the periodic subthreshold signal’s frequency and the dynamical response of the network motifs is resonantly dependent on the intensity of additive spatiotemporal noise. Interestingly, the excitatory intermediate neuron could induce intermittent stochastic resonance, whereas the inhibitory one weakens its influence on the intermittent mode. More importantly, it is found that the increasing delays can induce the intermittent appearance of regions of stochastic resonance. Based on the effects of the time delay on the stochastic resonance, the reasons and conditions of such intermittent resonance phenomenon are analyzed. 相似文献
108.
The classical problem of heat conduction in one dimension on a composite ring is examined. The problem is formulated using the heat equation with periodic boundary conditions. We provide an explicit solution of this problem using the Method of Fokas. The location of the interfaces is known, but neither temperature nor heat flux are prescribed there. Instead, the physical assumption of continuity at the interface is imposed. 相似文献
109.
《Journal of Pure and Applied Algebra》2022,226(4):106886
We describe the structure and properties of the finite-dimensional symmetric algebras over an algebraically closed field K which are socle equivalent to the general weighted surface algebras of triangulated surfaces, investigated in [11]. In particular, we prove that all these algebras are tame periodic algebras of period 4. The main results of this paper form an essential step towards a classification of all symmetric tame periodic algebras of period 4. 相似文献
110.