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991.
A. Nezakati 《随机分析与应用》2013,31(3):558-564
The expected number of real zeros of polynomials a 0 + a 1 x + a 2 x 2 +…+a n?1 x n?1 with random coefficients is well studied. For n large and for the normal zero mean independent coefficients, irrespective of the distribution of coefficients, this expected number is known to be asymptotic to (2/π)log n. For the dependent cases studied so far it is shown that this asymptotic value remains O(log n). In this article, we show that when cov(a i , a j ) = 1 ? |i ? j|/n, for i = 0,…, n ? 1 and j = 0,…, n ? 1, the above expected number of real zeros reduces significantly to O(log n)1/2. 相似文献
992.
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
993.
994.
Victor M. Kruglov 《随机分析与应用》2013,31(4):674-683
Kolmogorov's weak law of large numbers for i.i.d. random variables is generalized to a larger class distributions and to a wide class of normalizing sequences. The result is extended to maximal sums of negatively associated identically distributed random variables. 相似文献
995.
L. Chen L. Wu S. Zhu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(3):405-409
Synchronization in networks of complex topologies using couplings of
time-varying strength is numerically investigated. The
time-dependencies of coupling strengths are coupled to the dynamics
of the nodes in a way to enhance synchronization. By time-varying
couplings, oscillators are found to take quite a short time to reach
synchronization state when the couplings are relatively strong. Even
when a nearly regular networks of large-size with few shortcuts is
difficult to be synchronized by fixed couplings, the time-varying
couplings can easily enhance the emergence of synchronization. 相似文献
996.
We investigate the delocalization transition appearing in an exclusion process with two internal states, respectively on two
parallel lanes. At the transition, delocalized domain walls form in the density profiles of both internal states, in agreement
with a mean-field approach. Remarkably, the topology of the system’s phase diagram allows for the delocalization of a (localized)
domain wall when approaching the transition. We quantify the domain wall’s delocalization close to the transition by analytic
results obtained within the framework of the domain wall picture. Power law dependences of the domain wall width on the distance
to the delocalization transition as well as on the system size are uncovered, they agree with numerical results. 相似文献
997.
A. Fiasconaro W. Ebeling E. Gudowska-Nowak 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):403-414
We give an overview over recent studies on the model of Active Brownian Motion (ABM) coupled to reservoirs providing free
energy which may be converted into kinetic energy of motion. First, we present an introduction to a general concept of active
Brownian particles which are capable to take up energy from the source and transform part of it in order to perform various
activities. In the second part of our presentation we consider applications of ABM to ratchet systems with different forms
of differentiable potentials. Both analytical and numerical evaluations are discussed for three cases of sinusoidal, staircaselike
and Mateos ratchet potentials, also with the additional loads modelled by tilted potential structure. In addition, stochastic
character of the kinetics is investigated by considering perturbation by Gaussian white noise which is shown to be responsible
for driving the directionality of the asymptotic flux in the ratchet. This stochastically driven directionality effect is visualized as a strong nonmonotonic dependence of the statistics of the right versus left trajectories of motion
leading to a net current of particles. Possible applications of the ratchet systems to molecular motors are also briefly discussed. 相似文献
998.
When the processive motor protein kinesin walks along the biopolymer microtubule it can occasionally make a backward step.
Recent single molecule experiments on moving kinesin have revealed that the forward-to-backward step ratio decreases exponentially
with the load force. Carter and Cross (Nature 435, 308-312, 2005) found that this ratio tightly followed 802 × exp[−0.95F], where F is the load force in piconewtons. A straightforward analysis of a Brownian step leads to L/(2k
B
T) as the factor in front of the load force, where L is the 8 nm stepsize, k
B
is the Boltzmann constant, and T is the temperature. The factor L/(2k
B
T) does indeed equal 0.95 pN−1. The same analysis shows how the 802 prefactor derives from the power stroke energy G as exp[G/(2k
B
T)]. There are indications that the power stroke derives from the entropically driven coiling of the 30 amino acid neck linker
that connects the two kinesin heads. This idea is examined and consequences are deduced. 相似文献
999.
V. Schwämmle F. D. Nobre C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(4):537-546
The stability of q-Gaussian distributions as particular solutions of the
linear diffusion equation and its generalized nonlinear form, , the porous-medium equation, is investigated through both numerical
and analytical approaches. An analysis of the kurtosis of the distributions strongly suggests that an initial q-Gaussian, characterized by an index qi, approaches asymptotically the
final, analytic solution of the porous-medium equation, characterized by an index q, in such a way that the relaxation rule for
the kurtosis evolves in time according to a q-exponential, with a relaxation index qrel ≡qrel(q). In some cases, particularly when one attempts to transform an infinite-variance distribution (qi ≥ 5/3) into a finite-variance
one (q < 5/3), the relaxation towards the asymptotic solution may occur very slowly in time. This fact might shed some light
on the slow relaxation, for some long-range-interacting many-body Hamiltonian systems, from long-standing quasi-stationary
states to the ultimate thermal equilibrium
state. 相似文献
1000.
A. Shabunin A. Efimov 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):387-393
A spatio-temporal process in the Lattice Lotka Volterra (LLV) model, when realized on low dimensional support, is studied.
It is shown that the introduction of a long-range mixing causes a drastic change in the system’s behavior, which transits
from small random-like fluctuations to global oscillations when the mixing rate transcends above a critical point. The amplitude
of the induced oscillations is well defined by the mixing rate and is insensitive to the initial conditions and the lattice
size variations. The observed behavior essentially differs from that predicted by the Mean-Field model which is conservative.
The oscillations are of limit-cycle type and appear as a stochastic analog of a Hopf bifurcation. 相似文献