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981.
We propose a model of boundary interaction, with three-dimensional target space, and the boundary values of the field X∈R3 constrained to lay on a two-dimensional surface of the “pillow” shape. We argue that the model is integrable, and suggest that its exact solution is described in terms of certain linear ordinary differential equation. 相似文献
982.
Alberto Mittone Fabien Baldacci Alberto Bravin Emmanuel Brun François Delaire Claudio Ferrero Sergei Gasilov Nicolas Freud Jean Michel Létang David Sarrut François Smekens Paola Coan 《Journal of synchrotron radiation》2013,20(5):785-792
Medical imaging and radiation therapy are widely used synchrotron‐based techniques which have one thing in common: a significant dose delivery to typically biological samples. Among the ways to provide the experimenters with image guidance techniques indicating optimization strategies, Monte Carlo simulation has become the gold standard for accurately predicting radiation dose levels under specific irradiation conditions. A highly important hampering factor of this method is, however, its slow statistical convergence. A track length estimator (TLE) module has been coded and implemented for the first time in the open‐source Monte Carlo code GATE/Geant4. Results obtained with the module and the procedures used to validate them are presented. A database of energy‐absorption coefficients was also generated, which is used by the TLE calculations and is now also included in GATE/Geant4. The validation was carried out by comparing the TLE‐simulated doses with experimental data in a synchrotron radiation computed tomography experiment. The TLE technique shows good agreement versus both experimental measurements and the results of a classical Monte Carlo simulation. Compared with the latter, it is possible to reach a pre‐defined statistical uncertainty in about two to three orders of magnitude less time for complex geometries without loss of accuracy. 相似文献
983.
Rimma I. Samoilova Alexander T. Taguchi Patrick J. O’Malley Sergei A. Dikanov Johan Lugtenburg 《Applied magnetic resonance》2014,45(9):941-953
The anion radicals of ubiquinones-10 13C chemically labeled at the C5 or C6 ring positions in alcohol have been studied by 1D and 2D ESEEM to define the hyperfine interaction tensors with the 13C nuclei. Analysis of the cross-peak line shapes and simulations of the spectra allowed us to conclude that the hyperfine tensors are characterized by an anisotropic component T ~6 MHz and an isotropic coupling a ~?3 MHz with support from DFT calculations. However, these values were found to be inconsistent with the shift of the sum combination harmonic in the four-pulse ESEEM spectra. Simulations resolve this apparent discrepancy by showing that the shift of the sum combination to lower frequency and its broadening can be accounted for by a distribution of the hyperfine couplings. A spread of the methoxy group conformations, as supported by previous experimental observations, is suggested as the mechanism influencing the distribution of the hyperfine couplings for the ring carbons. 相似文献
984.
Sergei M. Pimenov Andrey A. Khomich Igor I. Vlasov Evgeny V. Zavedeev Alexander V. Khomich Beat Neuenschwander Beat Jäggi Valerio Romano 《Applied Physics A: Materials Science & Processing》2014,116(2):545-554
In this paper, we report on the bulk modifications of type IIa single-crystal diamond with visible 10-ps pulses (at λ = 532 nm) and microstructural changes characterized by the appearance of several ‘unidentifiable’ vibrational modes in the frequency range of 1000–1400 cm?1 in the Raman spectra of laser-modified diamond. It is found that the new Raman modes are strongly pronounced in the spectra of high-stress regions in immediate proximity to the bulk microstructures in the absence of the G mode at ~1580 cm?1 characteristic of the sp2 phase. The high internal stresses are determined from the splitting of the triply degenerate diamond Raman line. The revealed structure transformation is localized within a narrow bulk layer near the bulk microstructures formed, and the stress relaxation is found to result in disappearance of the detected vibrational modes in the spectra. It is suggested that the formation of bulk regions with a sp3 carbon structure consisting of Z-carbon and hexagonal diamond is responsible for the appearance of new Raman modes in the spectra of laser-modified diamond. These findings evidence that the stress-assisted formation of novel metastable carbon phases or defect structures occur in the course of bulk modification of diamond with ps-laser pulses. In addition, we report the results of simulations of internal stresses in the system ‘graphitized cylinder-in-diamond’ to show (1) the effect of the mechanical properties of laser-modified diamond on the resulting stresses and (2) formation of bulk microscopic regions with high stresses of >10 GPa, i.e., the conditions at which various sp3 carbon allotropes and defect structures become more stable than graphite. 相似文献
985.
Iver Brevik Olesya Gorbunova Shin’ichi Nojiri Sergei D. Odintsov 《The European Physical Journal C - Particles and Fields》2011,71(4):1629
As a first part of this work, experimental information about the decay of isotropic turbulence in ordinary hydrodynamics,
[`(u2(t))] μ t-6/5\overline{\mathbf{u}^{2}(t)}\propto t^{-6/5}, is used as input in FRW equations in order to investigate how an initial fraction f of turbulent kinetic energy in the cosmic fluid influences the cosmological development in the late, quintessence/phantom,
universe. First order perturbative theory to the first order in f is employed. It turns out that both in the Hubble factor and in the energy density, the influence from the turbulence fades
away at late times. The divergences in these quantities near the Big Rip behave essentially as in a non-turbulent fluid. However,
for the scale factor, the turbulence modification turns out to diverge logarithmically. As a second part of our work, we consider
the full FRW equation in which the turbulent part of the dark energy is accounted for by a separate term. It is demonstrated
that turbulence occurrence may change the future universe evolution due to dissipation of dark energy. For instance, the phantom-dominated
universe becomes asymptotically a de Sitter one in the future, thus avoiding the Big Rip singularity. 相似文献
986.
987.
Golovanov Aleksander А. Dan’kov Sergei А. Sokov Sergey А. Melnikov Pavel А. Ukolov Anton I. Voronova Evgeniya D. Vologzhanina Anna V. Bunev Aleksander S. 《Chemistry of Heterocyclic Compounds》2019,55(1):93-96
Chemistry of Heterocyclic Compounds - 5-Aryl-2-carboxy-5-(pyridin-1-ium-1-yl)penta-2,4-dienoates, previously unknown pyridine betaines, were formed in 32–70% yields as a result of the... 相似文献
988.
Artyom V. Astashenok Shinʼichi Nojiri Sergei D. Odintsov Robert J. Scherrer 《Physics letters. [Part B]》2012
Dark energy models with various scenarios of evolution are considered from the viewpoint of the formalism for the equation of state. It is shown that these models are compatible with current astronomical data. Some of the models presented here evolve arbitrarily close to ΛCDM up to the present, but diverge in the future into a number of different possible asymptotic states, including asymptotic de Sitter (pseudo-rip) evolution, little rips with disintegration of bound structures, and various forms of finite-time future singularities. Therefore it is impossible from observational data to determine whether the universe will end in a future singularity or not. We demonstrate that the models under consideration are stable for a long period of time (billions of years) before entering a Little Rip/Pseudo-Rip induced dissolution of bound structures or before entering a soft finite-time future singularity. Finally, the physical consequences of Little Rip, Types II, III and Big Crush singularities are briefly compared. 相似文献
989.
Nonlinear Dynamics - In this paper, a new simple oscillator model is considered describing ice-induced vibrations of upstanding, water-surrounded, and bottom-founded offshore structures. Existing... 相似文献