全文获取类型
收费全文 | 13303篇 |
免费 | 1406篇 |
国内免费 | 458篇 |
专业分类
化学 | 5737篇 |
晶体学 | 70篇 |
力学 | 1117篇 |
综合类 | 47篇 |
数学 | 5297篇 |
物理学 | 2899篇 |
出版年
2023年 | 153篇 |
2022年 | 132篇 |
2021年 | 228篇 |
2020年 | 415篇 |
2019年 | 299篇 |
2018年 | 277篇 |
2017年 | 255篇 |
2016年 | 470篇 |
2015年 | 481篇 |
2014年 | 604篇 |
2013年 | 1023篇 |
2012年 | 676篇 |
2011年 | 704篇 |
2010年 | 500篇 |
2009年 | 898篇 |
2008年 | 846篇 |
2007年 | 851篇 |
2006年 | 738篇 |
2005年 | 565篇 |
2004年 | 571篇 |
2003年 | 522篇 |
2002年 | 428篇 |
2001年 | 414篇 |
2000年 | 396篇 |
1999年 | 361篇 |
1998年 | 322篇 |
1997年 | 243篇 |
1996年 | 259篇 |
1995年 | 183篇 |
1994年 | 160篇 |
1993年 | 149篇 |
1992年 | 121篇 |
1991年 | 105篇 |
1990年 | 80篇 |
1989年 | 68篇 |
1988年 | 68篇 |
1987年 | 54篇 |
1986年 | 66篇 |
1985年 | 46篇 |
1984年 | 58篇 |
1983年 | 21篇 |
1982年 | 37篇 |
1981年 | 40篇 |
1980年 | 32篇 |
1979年 | 33篇 |
1978年 | 48篇 |
1977年 | 48篇 |
1976年 | 46篇 |
1975年 | 17篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
M. Sainath K. Venkataramaniah P. C. Sood 《The European Physical Journal A - Hadrons and Nuclei》2007,31(2):135-140
Low-lying two-quasiparticle bandhead energies for the Z = 99 odd-odd nucleus 254Es are evaluated using a simple phenomenological model with the inclusion of the residual p-n interaction. Configurations of the intrinsic levels directly fed in 254Es from the parent 258Md are discussed in the light of this model. Our analysis predicts the occurrence of ten K≤5 bandheads in 254Es with excitation energies E
x≤300keV. Structures of these as yet unidentified low-lying intrinsic levels and their expected locations are discussed in
the light of available experimental information. 相似文献
992.
S. Ansumali S. Arcidiacono S. S. Chikatamarla N. I. Prasianakis A. N. Gorban I. V. Karlin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(2):135-139
A general lattice Boltzmann method for simulation of
fluids with tailored transport coefficients is presented. It is
based on the recently introduced quasi-equilibrium kinetic models,
and a general lattice Boltzmann implementation is developed.
Lattice Boltzmann models for isothermal binary mixtures with a
given Schmidt number, and for a weakly compressible flow with a
given Prandtl number are derived and validated. 相似文献
993.
The Geant4 CHIPS model simulates both decay and nuclear capture of negative muons. In hadron level models the muon is captured
by a proton, p(μ,νμ)n , and the neutron transfers to the nucleus only 5MeV, which is not enough to split a nucleon from the nucleus, while the
measured spectra of emitted nucleons reach 80MeV. In CHIPS, which considers asymptotically free quark-partons, the muon can
be captured by a quark, u(μ,νμ)d , and transfers 52MeV to the nucleus. This capture mechanism fits the main part of the nucleon spectra, while the high-energy
part of the spectra is not fitted. A precise fit of the high-energy part of the nucleon spectra can be made if the muon decay
μ → dˉνμ is taken into account. 相似文献
994.
B. Dybiec L. Schimansky-Geier 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):313-320
We study the stationary probability density of a Brownian particle in a potential with a single-well subject to the purely
additive thermal and dichotomous noise sources. We find situations where bimodality of stationary densities emerges due to
presence of dichotomous noise. The solutions are constructed using stochastic dynamics (Langevin equation) or by discretization
of the corresponding Fokker-Planck equations. We find that in models with both noises being additive the potential has to
grow faster than |x| in order to obtain bimodality. For potentials ∝|x| stationary solutions are always of the double exponential
form. 相似文献
995.
996.
Lu‐Feng Zou Kuang Shen Yao Fu Qing‐Xiang Guo 《Journal of Physical Organic Chemistry》2007,20(10):754-763
Experimental studies showed that sulfur radicals play the vital role in petroleum formation. 1 Sulfur‐ centered radicals also exhibit activities in antioxidant functions. Here we conduct a theoretical investigation of their precursor‐disulfides. By investigation into substituent effect on sulfur? sulfur bond dissociation enthalpies (S? S BDEs), we would like to find the most effective provider for sulfur radicals. In the present work, 50 alpha‐substituted disulfides and 16 para‐substituted aryl disulfides are studied systematically, with the general formula XS‐SX or HS‐SX. The substituent effect on S? S BDEs is found to be very eminent, ranging from 33.2 to 75.0 kcal/mol for alpha‐substituted disulfide, and from 43.7 to 59.7 kcal/mol for para‐substituted phenyl disulfides. We also evaluate the performance of 44 density functional methods to get an accurate prediction. A further study indicates that substituents play a major role in radical energies, instead of molecule energies, which is substantiated by the good linearity between XS‐SX bond dissociation enthalpy (BDE) and HS‐SX BDE. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
997.
Escort distributions are a well established but (for physicists) a relatively new concept that is rapidly gaining wide acceptance in world. In this work we wish to revisit the concept within the strictures of the celebrated semiclassical Husimi distributions (HDs) and thereby investigate the possibility of extracting new semiclassical information contained, not in the HD themselves, but in their associated escort Husimi distributions. We will also establish relations, for various information measures, between their deformed versions [J. Naudts, Physica A 316 (2002) 323] and those built up with escort HDs. Bounds on the concomitant power exponents will be determined. 相似文献
998.
In a recent paper [T. Wada, A.M. Scarfone, Phys. Lett. A 335 (2005) 351] the authors discussed the equivalence among the various probability distribution functions of a system in equilibrium in the Tsallis entropy framework. In the present letter we extend these results to a system which is out of equilibrium and evolves to a stationary state according to a nonlinear Fokker-Planck equation (NFPE). By means of time-scale conversion, it is shown that there exists a “correspondence” among the self-similar solutions of the NFPEs associated with the different Tsallis formalisms. The time-scale conversion is related to the corresponding Lyapunov functions of the respective NFPEs. 相似文献
999.
Considerable advances in automatic speech recognition have been made in the last decades, thanks specially to the use of hidden Markov models. In the field of speech signal analysis, different techniques have been developed. However, deterioration in the performance of the speech recognizers has been observed when they are trained with clean signal and tested with noisy signals. This is still an open problem in this field. Continuous multiresolution entropy has been shown to be robust to additive noise in applications to different physiological signals. In previous works we have included Shannon and Tsallis entropies, and their corresponding divergences, in different speech analysis and recognition systems. In this paper we present an extension of the continuous multiresolution entropy to different divergences and we propose them as new dimensions for the pre-processing stage of a speech recognition system. This approach takes into account information about changes in the dynamics of speech signal at different scales. The methods proposed here are tested with speech signals corrupted with babble and white noise. Their performance is compared with classical mel cepstral parametrization. The results suggest that these continuous multiresolution entropy related measures provide valuable information to the speech recognition system and that they could be considered to be included as an extra component in the pre-processing stage. 相似文献
1000.