全文获取类型
收费全文 | 404篇 |
免费 | 15篇 |
国内免费 | 24篇 |
专业分类
化学 | 64篇 |
晶体学 | 2篇 |
力学 | 41篇 |
数学 | 109篇 |
物理学 | 227篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 46篇 |
2012年 | 36篇 |
2011年 | 31篇 |
2010年 | 27篇 |
2009年 | 30篇 |
2008年 | 30篇 |
2007年 | 27篇 |
2006年 | 27篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 12篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有443条查询结果,搜索用时 552 毫秒
71.
We focus here on the scaling properties of small interspecies differences between red cone opsin transmembrane proteins, using a hydropathic elastic roughening tool previously applied to the rhodopsin rod transmembrane proteins. This tool is based on a non-Euclidean hydropathic metric realistically rooted in the atomic coordinates of 5526 protein segments, which thereby encapsulates universal non-Euclidean long-range differential geometrical features of water films enveloping globular proteins in the Protein Data Bank. Whereas the rhodopsin blue rod water films are smoothest in humans, the red cone opsins’ water films are optimized for smoothness in cats and elephants, consistent with protein species landscapes that evolve differently in different contexts. We also analyze red cone opsins in the chromatophore-containing family of chameleons, snakes, zebrafish and goldfish, where short- and long-range (BLAST and hydropathic) amino acid (aa) correlations are found with values as large as 97%–99%. We use hydropathic aa optimization to estimate the maximum number Nmax of color shades that the human eye can discriminate, and obtain 106<Nmax<107, in good agreement with experiment. 相似文献
72.
73.
Abstract We introduce a new self-interacting random walk on the integers in a dynamic random environment and show that it converges to a pure diffusion in the scaling limit. We also find a lower bound on the diffusion coefficient in some special cases. With minor changes the same argument can be used to prove the scaling limit of the corresponding walk in ? d . 相似文献
74.
Gi-Ren Liu 《随机分析与应用》2013,31(3):505-522
Let X = {X(x, t), x ? R n , t ? R +} be the R 2-valued spatial-temporal random field X = (u, v) arising from a certain two-equation system of parabolic linear partial differential equations with a given random initial condition X 0 = (u 0, v 0). We discuss the scaling limit of X under suitable conditions on X 0. Since the component fields u, v are dependent, even when the initial data u 0, v 0 are independent, the scaling limit is not readily reduced to the known single equation case. The correlated structure of random vector (u(x, t), v(x′, t′)) and the Hermite expansion associated with (u 0, v 0) play the essential roles in our study. The work shows, in particular, the non-Gaussian scenario proposed by Anh and Leonenko [2] for the single heat equation can be discussed for the two-equation system, in a significant way. 相似文献
75.
Laurent Duvernet 《随机分析与应用》2013,31(5):763-792
Some asymptotic properties of a Brownian motion in multifractal time, also called multifractal random walk, are established. We show the almost sure and L 1 convergence of its structure function. This is an issue directly connected to the scale invariance and multifractal property of the sample paths. We place ourselves in a mixed asymptotic setting where both the observation length and the sampling frequency may go together to infinity at different rates. The results we obtain are similar to the ones that were given by Ossiander and Waymire [19] and Bacry et al. [1] in the simpler framework of Mandelbrot cascades. 相似文献
76.
Field amplified sample stacking (FASS) uses differential electrophoretic velocity of analyte ions in the high‐conductivity background electrolyte zone and low conductivity sample zone for increasing the analyte concentration. The stacking rate of analyte ions in FASS is limited by molecular diffusion and convective dispersion due to nonuniform electroosmotic flow (EOF). We present a theoretical scaling analysis of stacking dynamics in FASS and its validation with a large set of on‐chip sample stacking experiments and numerical simulations. Through scaling analysis, we have identified two stacking regimes that are relevant for on‐chip FASS, depending upon whether the broadening of the stacked peak is dominated by axial diffusion or convective dispersion. We show that these two regimes are characterized by distinct length and time scales, based on which we obtain simplified nondimensional relations for the temporal growth of peak concentration and width in FASS. We first verify the theoretical scaling behavior in diffusion‐ and convection‐dominated regimes using numerical simulations. Thereafter, we show that the experimental data of temporal growth of peak concentration and width at varying electric fields, conductivity gradients, and EOF exhibit the theoretically predicted scaling behavior. The scaling behavior described in this work provides insights into the effect of varying experimental parameters, such as electric field, conductivity gradient, electroosmotic mobility, and electrophoretic mobility of the analyte on the dynamics of on‐chip FASS. 相似文献
77.
Pulak Ranjan Giri 《International Journal of Theoretical Physics》2008,47(10):2583-2590
We argue that it is possible to bind neutral atom (NA) to the ferromagnetic wire (FW) by inequivalent quantization of the
Hamiltonian. We follow the well known von Neumann’s method of self-adjoint extensions (SAE) to get this inequivalent quantization,
which is characterized by a parameter Σ∈ℝ(mod2π). There exists a single bound state for the coupling constant η
2∈[0,1). Although this bound state should not occur due to the existence of classical scale symmetry in the problem. But since
quantization procedure breaks this classical symmetry, bound state comes out as a scale in the problem leading to scaling
anomaly. We also discuss the strong coupling region η
2<0, which supports bound state making the problem re-normalizable. 相似文献
78.
Hideki Funamizu 《Optics Communications》2008,281(4):543-549
It is known that speckle patterns with fractal properties, called fractal speckles, are produced by illuminating a diffuser with the coherent light having the intensity distribution obeying a negative power law. One of key properties of fractal speckles is the spatial correlation function obeying a negative power law, which implies that such speckles have scaling properties. In detecting fractal speckles, the effect of the spatial integration is inevitable in most cases since they have speckle grains of various scales including very fine ones. To evaluate this effect, in this paper, the contrast of spatially integrated intensity distributions is investigated theoretically and experimentally for fractal speckles. The results show that the contrast reduction with the size of the detector aperture obeys a negative power function related with the exponent of the intensity correlation coefficient of fractal speckles. 相似文献
79.
80.
《Stochastic Processes and their Applications》2020,130(7):4358-4391
We consider a critical superprocess with general spatial motion and spatially dependent stable branching mechanism with lowest stable index . We first show that, under some conditions, converges to 0 as and is regularly varying with index . Then we show that, for a large class of non-negative testing functions , the distribution of , after appropriate rescaling, converges weakly to a positive random variable with Laplace transform 相似文献