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41.
All video streams consist of highly compressed coded data. A video stream must be decoded to identify a video. It is impossible to decode and identify a video fragment without knowing the correct video format. Therefore, the first issue that must be addressed is classification of video formats. Although several methods exist for classifying file formats, a technology that specifically classifies the formats of video fragments has not been developed. In this paper, we present a novel approach to classify the formats of small fragments of video streams. Our classification procedure involves construction of high-dimensional feature vectors by combining synchronization patterns extracted from training fragments. The feature vectors are classified using optimized discriminative subspace clustering (ODiSC). The experimental results show a minimum classification error rate of 4.2%, and the precision of identification of the formats was greater than 91% for the four video formats whose fragment size was 256 KB. 相似文献
42.
Sidney W. Graham 《Discrete Applied Mathematics》2008,156(16):3150-3154
We show that using character sum estimates due to H. Iwaniec leads to an improvement of recent results about the distribution and finding RSA moduli M=pl, where p and l are primes, with prescribed bit patterns. We are now able to specify about n bits instead of about n/2 bits as in the previous work. We also show that the same result of H. Iwaniec can be used to obtain an unconditional version of a combinatorial result of W. de Launey and D. Gordon that was originally derived under the Extended Riemann Hypothesis. 相似文献
43.
At EuroCrypt '99 Paillier proposed a new encryption scheme based on higher residuosity classes. The new scheme was proven
to be one-way under the assumption that computing
N -residuosity classes in Z
N2
*
is hard. Similarly the scheme can be proven to be semantically secure under a much stronger decisional assumption: given w ∈ Z
N2
*
it is impossible to decide if w is an N -residue or not.
In this paper we examine the bit security of Paillier's scheme. We prove that if computing residuosity classes is hard, then
given a random w it is impossible to predict the least significant bit of its class significantly better than at random. This immediately
yields a way to obtain semantic security without relying on the decisional assumption (at the cost of several invocations
of Paillier's original function).
In order to improve efficiency we then turn to the problem of simultaneous security of many bits. We prove that Paillier's
scheme hides n-b (up to O(n) ) bits if one assumes that computing the class c of a random w remains hard even when we are told that c<2
b
. We thoroughly examine the security of this stronger version of the intractability of the class problem.
An important theoretical implication of our result is the construction of the first trapdoor function that hides super-logarithmically
(up to O(n) ) many bits. We generalize our techniques to provide sufficient conditions for a trapdoor function to have this property. 相似文献
44.
Bernhard Schweizer 《Nonlinear dynamics》2009,57(4):509-532
High-speed rotors are often supported in floating ring bearings because of their good damping behavior. In contrast to conventional
hydrodynamic bearings with a single oil film, full-floating ring bearings consist of two oil films: An inner and an outer
oil film. As single oil-film bearings, full-floating ring bearings also show the typical fluid-film-induced instabilities
(self-excited vibrations). Both inner and outer oil films can become unstable and exhibit oil whirl/whip instabilities.
The paper at hand considers a Laval (Jeffcott) rotor, which is symmetrically supported in full-floating ring bearings, and
investigates the occurring oil whirl/whip effects by means of run-up simulations. It is shown that the inner oil film, which usually becomes unstable first, gives
rise to a limit-cycle oscillation with an exactly circular rotor orbit, if gravity and imbalance are neglected. Interesting
is the instability generated by the outer oil film. The calculations demonstrate that instability in the outer oil film does
not lead to a simple circular limit-cycle orbit. Whirl/whip-induced limit-cycle oscillations generated by the outer oil film are more complex and entail a coupled circumferential and
radial motion, although the mechanical problem is radially symmetric, if gravity and imbalance are neglected. Thus, whirl/whip instability in the outer fluid film may be interpreted as symmetry breaking.
Finally, a further kind of bifurcation/instability occurring in rotors supported in full-floating ring bearings—called Total Instability in this paper—is analyzed. It is shown that Total Instability is caused by synchronization of two limit cycles, namely synchronization of the inner and outer oil whirl/whip. Total Instability is of practical interest and observed in real technical rotor systems, and frequently leads to complete rotor damage. 相似文献
45.
P. M. Gleiser D. H. Zanette 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(2):233-238
We analyze the interplay of synchronization and structure
evolution in an evolving network of phase oscillators. An initially
random network is adaptively rewired according to the dynamical
coherence of the oscillators, in order to enhance their mutual
synchronization. We show that the evolving network reaches a
small-world structure. Its clustering coefficient attains a maximum
for an intermediate intensity of the coupling between oscillators,
where a rich diversity of synchronized oscillator groups is
observed. In the stationary state, these synchronized groups are
directly associated with network clusters. 相似文献
46.
47.
A. Pluchino V. Latora A. Rapisarda 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):169-176
We discuss two models of opinion dynamics. We first present a brief review of
the Hegselmann and Krause (HK) compromise model in two dimensions,
showing that it is possible to simulate the dynamics
in the limit of an infinite number of agents by solving numerically a rate equation for
a continuum distribution of opinions. Then, we discuss the Opinion Changing Rate (OCR) model,
which allows to study under which conditions a group of agents with a
different natural tendency (rate) to change opinion can find the
agreement. In the context of the this model, consensus is viewed as a synchronization
process. 相似文献
48.
This work presents chaos synchronization between two different hyperchaotic systems using adaptive control. The sufficient conditions for achieving synchronization of two high dimensional chaotic systems are derived based on Lyapunov stability theory, and an adaptive control law and a parameter update rule for unknown parameters are given such that generalized Henon–Heiles system is controlled to be hyperchaotic Chen system. Theoretical analysis and numerical simulations are shown to verify the results. 相似文献
49.
Alexander E. HramovAlexey A. Koronovskii Maria K. KurovskayaOlga I. Moskalenko 《Physics letters. A》2011,375(15):1646-1652
In this Letter we compare the characteristics of two types of the intermittent behavior (type-I intermittency in the presence of noise and eyelet intermittency taking place in the vicinity of the chaotic phase synchronization boundary) supposed hitherto to be different phenomena. We show that these effects are the same type of dynamics observed under different conditions. The correctness of our conclusion is confirmed by the consideration of different sample systems, such as quadratic map, Van der Pol oscillator and Rössler system. Consideration of the problem concerning the upper boundary of the intermittent behavior also confirms the validity of the statement on the equivalence of type-I intermittency in the presence of noise and eyelet intermittency observed in the onset of phase synchronization. 相似文献
50.
We study the cross-correlations of buy and sell volumes on the Korean stock market in high frequency. We observe that the pulling effects of volumes are as small as that of returns. The properties of the correlations of buy and sell volumes differ. They are explained by the degree of synchronization of stock volumes. Further, the pulling effects on the minimal spanning tree are studied. In minimal spanning trees with directed links, the large pulling effects are clustered at the center, not uniformly distributed. The Epps effect of buy and sell volumes are observed. The reversal of the cross-correlations of buy and sell volumes is also detected. 相似文献