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1.
2.
A new approach to identify the independent amplitudes along with their partial wave multipole expansions, for photo-and electro-production
is suggested, which is generally applicable to mesons with arbitrary spin-parity. These amplitudes facilitate direct identification
of different resonance contributions.
相似文献
3.
Almost thirty years ago, Penny G. Estabrooks asked “Where and what are the scalar mesons?” (P. Estabrooks, Phys. Rev. D 19, 2678 (1979)). The first part of her question can now be confidently responded (E. van Beveren et al., Z. Phys. C 30, 615 (1986)). However, with respect to the “What” many puzzles remain unanswered. Scalar and axial-vector mesons form part
of a large family of mesons. Consequently, though it is useful to pay them some extra attention, there is no point in discussing
them as isolated phenomena. The particularity of structures in the scattering of --basically-- pions and kaons with zero angular
momentum is the absence of the centrifugal barrier, which allows us to “see” strong interactions at short distances. Experimentally
observed differences and similarities between scalar and axial-vector mesons on the one hand, and other mesons on the other
hand, are very instructive for further studies. Nowadays, there exists an abundance of theoretical approaches towards the
mesonic spectrum, ranging from confinement models of all kinds, i.e., glueballs, and quark-antiquark, multiquark and hybrid configurations, to models in which only mesonic degrees of freedom
are taken into account. Nature seems to come out somewhere in the middle, neither preferring pure bound states, nor effective
meson-meson physics with only coupling constants and possibly form factors. As a matter of fact, apart from a few exceptions,
like pions and kaons, Nature does not allow us to study mesonic bound states of any kind, which is equivalent to saying that
such states do not really exist. Hence, instead of extrapolating from pions and kaons to the remainder of the meson family,
it is more democratic to consider pions and kaons mesonic resonances that happen to come out below the lowest threshold for
strong decay. Nevertheless, confinement is an important ingredient for understanding the many regularities observed in mesonic
spectra. Therefore, excluding quark degrees of freedom is also not the most obvious way of describing mesons in general, and
scalars and axial-vectors in particular. 相似文献
4.
A relativistic model of independent quarks based on Dirac equation with an equally mixed scalar-vector square root confining
potential is used to compute the quark core contributions to the static properties like magnetic moments, charge radii and
axial vector coupling constant ratios of the baryon octet. The results obtained with appropriate corrections due to centre-of-mass
motion agree fairly well with experimental values. The model is also extended to the study of magnetic moments of the quark
core of baryons in the charmed andb-flavoured sectors and the overall predictions so obtained compare well with other model predictions. 相似文献
5.
Yeinzon?RodríguezEmail author Carlos?QuimbayEmail author 《Foundations of Physics Letters》2005,18(7):581-602
No Heading Several works analyzing the new physics contributions from the Left-Right Symmetric Model to the CP violation phenomena in
the neutral B mesons can be found in the literature. These works exhibit interesting and experimentally sensible deviations
from the Standard Model predictions but at the expense of considering a low right scale υR around 1 TeV. However, when we stick to the more conservative estimates for υR, which say that it must be at least 107 GeV, no experimentally sensible deviations from the Standard Model appear for indirect CP violation. This estimate for υR arises when the generation of neutrino masses is considered. In spite of the fact that this scenario is much less interesting
and says nothing new about both the CP violation phenomenon and the structure of the Left-Right Symmetric Model, this possibility
must be taken into account for the sake of completeness and when considering the see-saw mechanism that provides masses to
the neutrino sector.
1 Associate researcher of the Centro Internacional de Física, Ciudad
Universitaria, Bogotá D.C., Colombia. 相似文献
6.
A.?N.?IvanovEmail author M.?Cargnelli M.?Faber H.?Fuhrmann V.?A.?Ivanova J.?Marton N.?I.?Troitskaya J.?Zmeskal 《The European Physical Journal A - Hadrons and Nuclei》2005,25(3):329-338
We argue that due to isospin and U-spin invariance of strong low-energy interactions the S-wave scattering lengths a
0
0 and a
1
0 of ˉN scattering with isospin I = 0 and I = 1 satisfy the low-energy theorem a
0
0 +3a
1
0 = 0 valid to leading order in chiral expansion. In the model of strong low-energy ˉN interactions at threshold (Eur. Phys. J. A 21, 11 (2004)) we revisit the contribution of the Σ(1750) resonance, which does not saturate the low-energy theorem a
0
0 +3a
1
0 = 0, and replace it by the baryon background with properties of an SU(3) octet. We calculate the S-wave scattering amplitudes of K-N and K-d scattering at threshold. We calculate the energy level displacements of the ground states of kaonic hydrogen and deuterium.
The result obtained for kaonic hydrogen agrees well with recent experimental data by the DEAR Collaboration. We analyse the
cross-sections for elastic and inelastic K-p scattering for laboratory momenta 70MeV/c < p
K < 150MeV/c of the incident K--meson. The theoretical results agree with the available experimental data within two standard deviations. 相似文献
7.
G. Pancheri O. Shekhovtsova G. Venanzoni 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):458-460
Effects due to the non-pointlike behaviour of pions in the process e
+
e
-→π
+
π
-
γ can arise for hard photons in the final state. By means of a Monte Carlo event generator, which also includes the contribution
of the direct decay φ→π
+
π
-
γ, we estimate these effects in the framework of the resonance perturbation theory. We consider angular cuts used in the KLOE
analysis of the pion form factor at threshold. A method to reveal the effects of the non-pointlike behaviour of pions in a
model-independent way is proposed. 相似文献
8.
用振幅比之方法计算了中性粲介子衰变到CP本征态的CP不对称性. 计算了时间相关和时间积分的CP不对称性. 结果表明, 时间积分的CP不对称参数约为千分之一的量级. 还讨论了在BESⅢ和B工厂上实验检验的可能性. 相似文献
9.
D. Gotta K. Rashid B. Fricke P. Indelicato L. M. Simons 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):11-26
The onset of antiprotonic X-ray transitions at high principal quantum numbers and the occurrence of electronic X-rays in antiprotonic
argon, krypton, and xenon has been analyzed with the help of Multiconfiguration Dirac-Fock calculations. The shell-by-shell
ionisation by Auger electron emission, characterised by appearance and disappearance of X-ray lines, is followed through the
antiprotonic cascade by considering transition and binding energies of both the antiproton and the remaining electrons. Electronic
lines could be attributed partly to specific states of the antiprotonic atom de-excitation. 相似文献
10.
Possible structures and properties of some excited states of Λc+ dynamically generated in the coupled-channel P-wave meson-baryon scattering are studied by solving the Bethe-Salpeter(BS) equation in the framework of the Chiral Unitary Approach. It is shown that both Λc+(2765) and Λc+(2940) could be generated dynamically and could be compound states with multi-configuration molecular-like structures. The couplings of the generated states to various reaction channels are also calculated. Moreover, two highly excited states, Λc+(3024) and Λc+(3134), are predicted. 相似文献