全文获取类型
收费全文 | 16404篇 |
免费 | 1333篇 |
国内免费 | 794篇 |
专业分类
化学 | 445篇 |
晶体学 | 10篇 |
力学 | 2267篇 |
综合类 | 108篇 |
数学 | 12750篇 |
物理学 | 2951篇 |
出版年
2024年 | 37篇 |
2023年 | 174篇 |
2022年 | 145篇 |
2021年 | 246篇 |
2020年 | 454篇 |
2019年 | 445篇 |
2018年 | 451篇 |
2017年 | 438篇 |
2016年 | 428篇 |
2015年 | 392篇 |
2014年 | 685篇 |
2013年 | 1784篇 |
2012年 | 633篇 |
2011年 | 951篇 |
2010年 | 763篇 |
2009年 | 1061篇 |
2008年 | 1039篇 |
2007年 | 967篇 |
2006年 | 888篇 |
2005年 | 687篇 |
2004年 | 619篇 |
2003年 | 612篇 |
2002年 | 609篇 |
2001年 | 488篇 |
2000年 | 494篇 |
1999年 | 450篇 |
1998年 | 374篇 |
1997年 | 358篇 |
1996年 | 263篇 |
1995年 | 186篇 |
1994年 | 172篇 |
1993年 | 141篇 |
1992年 | 104篇 |
1991年 | 92篇 |
1990年 | 83篇 |
1989年 | 61篇 |
1988年 | 46篇 |
1987年 | 51篇 |
1986年 | 38篇 |
1985年 | 65篇 |
1984年 | 104篇 |
1983年 | 51篇 |
1982年 | 67篇 |
1981年 | 64篇 |
1980年 | 59篇 |
1979年 | 56篇 |
1978年 | 54篇 |
1977年 | 33篇 |
1976年 | 27篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
M. Amar D. Andreucci R. Gianni C. Timofte 《Journal of Mathematical Analysis and Applications》2021,493(2):124533
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation. 相似文献
3.
Bifurcation analysis of visual angle model with anticipated time and stabilizing driving behavior
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xueyi Guan 《中国物理 B》2022,31(7):70507-070507
In the light of the visual angle model (VAM), an improved car-following model considering driver's visual angle, anticipated time and stabilizing driving behavior is proposed so as to investigate how the driver's behavior factors affect the stability of the traffic flow. Based on the model, linear stability analysis is performed together with bifurcation analysis, whose corresponding stability condition is highly fit to the results of the linear analysis. Furthermore, the time-dependent Ginzburg-Landau (TDGL) equation and the modified Korteweg-de Vries (mKdV) equation are derived by nonlinear analysis, and we obtain the relationship of the two equations through the comparison. Finally, parameter calibration and numerical simulation are conducted to verify the validity of the theoretical analysis, whose results are highly consistent with the theoretical analysis. 相似文献
4.
5.
《Studies in Applied Mathematics》2018,141(3):399-417
We extend our previous results characterizing the loading properties of a diffusing passive scalar advected by a laminar shear flow in ducts and channels to more general cross‐sectional shapes, including regular polygons and smoothed corner ducts originating from deformations of ellipses. For the case of the triangle and localized, cross‐wise uniform initial distributions, short‐time skewness is calculated exactly to be positive, while long‐time asymptotics shows it to be negative. Monte Carlo simulations confirm these predictions, and document the timescale for sign change. The equilateral triangle appears to be the only regular polygon with this property—all others possess positive skewness at all times. Alternatively, closed‐form flow solutions can be constructed for smooth deformations of ellipses, and illustrate how both nonzero short‐time skewness and the possibility of multiple sign switching in time is unrelated to domain corners. Exact conditions relating the median and the skewness to the mean are developed which guarantee when the sign for the skewness implies front (more mass to the right of the mean) or back (more mass to the left of the mean) “loading” properties of the evolving tracer distribution along the pipe. Short‐ and long‐time asymptotics confirm this condition, and Monte Carlo simulations verify this at all times. The simulations are also used to examine the role of corners and boundaries on the distribution for short‐time evolution of point source , as opposed to cross‐wise uniform, initial data. 相似文献
6.
Erosion and sediments transport processes have a great impact on industrial structures and on water quality. Despite its limitations, the Saint‐Venant‐Exner system is still (and for sure for some years) widely used in industrial codes to model the bedload sediment transport. In practice, its numerical resolution is mostly handled by a splitting technique that allows a weak coupling between hydraulic and morphodynamic distinct softwares but may suffer from important stability issues. In recent works, many authors proposed alternative methods based on a strong coupling that cure this problem but are not so trivial to implement in an industrial context. In this work, we then pursue 2 objectives. First, we propose a very simple scheme based on an approximate Riemann solver, respecting the strong coupling framework, and we demonstrate its stability and accuracy through a number of numerical test cases. However, second, we reinterpret our scheme as a splitting technique and we extend the purpose to propose what should be the minimal coupling that ensures the stability of the global numerical process in industrial codes, at least, when dealing with collocated finite volume method. The resulting splitting method is, up to our knowledge, the only one for which stability properties are fully demonstrated. 相似文献
7.
8.
9.
AbstractRealistic stochastic modeling is increasingly requiring the use of bounded noises. In this work, properties and relationships of commonly employed bounded stochastic processes are investigated within a solid mathematical ground. Four families are object of investigation: the Sine-Wiener (SW), the Doering–Cai–Lin (DCL), the Tsallis–Stariolo–Borland (TSB), and the Kessler–Sørensen (KS) families. We address mathematical questions on existence and uniqueness of the processes defined through Stochastic Differential Equations, which often conceal non-obvious behavior, and we explore the behavior of the solutions near the boundaries of the state space. The expression of the time-dependent probability density of the Sine-Wiener noise is provided in closed form, and a close connection with the Doering–Cai–Lin noise is shown. Further relationships among the different families are explored, pathwise and in distribution. Finally, we illustrate an analogy between the Kessler–Sørensen family and Bessel processes, which allows to relate the respective local times at the boundaries. 相似文献
10.