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41.
We show that diversity, in the form of quenched noise, can have a constructive effect in the dynamics of extended systems.
We first consider a bistable φ4 model composed by many coupled units and show that the global response to an external periodic forcing is enhanced under
the presence of the right amount of diversity (measured as the dispersion in one of the parameters defining the model). As
a second example, we consider a system of active-rotators and show that while they are at rest in the homogeneous case, the
disorder introduced by the diversity suffices to trigger the appearance of common firings or pulses. Both effects require
very simple ingredients and we expect the results presented here to be of interest in similar models. 相似文献
42.
M. Pineda R. Toral E. Hernández-García 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,62(1):109-117
We study the effects of diffusing opinions on the Deffuant et al. model for continuous
opinion dynamics. Individuals are given the opportunity to change their opinion, with a
given probability, to a randomly selected opinion inside an interval centered around the
present opinion. We show that diffusion induces an order-disorder transition. In the
disordered state the opinion distribution tends to be uniform, while for the ordered state
a set of well defined opinion clusters are formed, although with some opinion spread
inside them. If the diffusion jumps are not large, clusters coalesce, so that weak
diffusion favors opinion consensus. A master equation for the process described above is
presented. We find that the master equation and the Monte Carlo simulations do not always
agree due to finite-size induced fluctuations. Using a linear stability analysis we can
derive approximate conditions for the transition between opinion clusters and the
disordered state. The linear stability analysis is compared with Monte Carlo simulations.
Novel interesting phenomena are analyzed. 相似文献
43.
C. J. Tessone R. Toral 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,71(4):549-555
We perform a computational study of a variant of the “train” model for earthquakes [Phys. Rev. A 46, 6288 (1992)], where we assume a static friction that is a stochastic function of position rather than being velocity dependent.
The model consists of an array of blocks coupled by springs, with the forces between neighbouring blocks balanced by static
friction. We calculate the probability, P(s), of the occurrence of avalanches with a size s or greater, finding that our results
are consistent with the phenomenology and also with previous models which exhibit a power law over a wide range. We show that
the train model may be mapped onto a stochastic sandpile model and study a variant of the latter for non-spherical grains.
We show that, in this case, the model has critical behaviour only for grains with large aspect ratio, as was already shown
in experiments with real ricepiles. We also demonstrate a way to introduce randomness in a physically motivated manner into
the model. 相似文献
44.
We present conclusive evidence showing that different sources of diversity, such as those represented by quenched disorder or noise, can induce a resonant collective behavior in an ensemble of coupled bistable or excitable systems. Our analytical and numerical results show that when such systems are subjected to an external subthreshold signal, their response is optimized for an intermediate value of the diversity. These findings show that intrinsic diversity might have a constructive role and suggest that natural systems might profit from their diversity in order to optimize the response to an external stimulus. 相似文献
45.
We study the effect that the injection of a common source of noise has on the trajectories of chaotic systems, addressing some contradictory results present in the literature. We present particular examples of one-dimensional maps and the Lorenz system, both in the chaotic region, and give numerical evidence showing that the addition of a common noise to different trajectories, which start from different initial conditions, leads eventually to their perfect synchronization. When synchronization occurs, the largest Lyapunov exponent becomes negative. For a simple map we are able to show this phenomenon analytically. Finally, we analyze the structural stability of the phenomenon. (c) 2001 American Institute of Physics. 相似文献
46.
47.
It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixture is substantially narrowed when the fluid is confined in an aerogel with a high degree of porosity (e.g., of the order of 95 to 99%). A Hamiltonian model for this system has recently been introduced [1]. We have performed Monte-Carlo simulations for this model to obtain the phase diagram for the model. We use a periodic fractal structure constructed by diffusion-limited cluster-cluster aggregation (DLCA) method to simulate a realistic gel environment. The phase diagram obtained is qualitatively similar to that observed experimentally. We also have observed some metastable branches in the phase diagram which have not been seen in experiments yet. These branches, however, might be important in the context of recent theoretical predictions and other simulations. 相似文献
48.
Mayol Catalina Toral Raúl Wio Horacio S. 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(6):1-20
The European Physical Journal B - Understanding and controlling the magnetization dynamics on the femtosecond timescale is becoming indispensable both at the fundamental level and to develop future... 相似文献
49.
R. Salazar A.R. Plastino R. Toral 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):679-688
We introduce a new nonextensive entropic measure that grows like , where N is the size of the system under consideration. This kind of nonextensivity arises in a natural way in some N-body systems endowed with long-range interactions described by interparticle potentials. The power law (weakly nonextensive) behavior exhibited by is intermediate between (1) the linear (extensive) regime characterizing the standard Boltzmann-Gibbs entropy and (2) the
exponential law (strongly nonextensive) behavior associated with the Tsallis generalized q-entropies. The functional is parametrized by the real number in such a way that the standard logarithmic entropy is recovered when . We study the mathematical properties of the new entropy, showing that the basic requirements for a well behaved entropy
functional are verified, i.e., possesses the usual properties of positivity, equiprobability, concavity and irreversibility and verifies Khinchin axioms
except the one related to additivity since is nonextensive. For , the entropy becomes superadditive in the thermodynamic limit. The present formalism is illustrated by a numerical study of the thermodynamic
scaling laws of a ferromagnetic Ising model with long-range interactions.
Received 24 May 2000 相似文献
50.