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351.
352.
353.
Conformational polymorphism of the PrP106-126 peptide in different environments: a molecular dynamics study 总被引:1,自引:0,他引:1
Villa A Mark AE Saracino GA Cosentino U Pitea D Moro G Salmona M 《The journal of physical chemistry. B》2006,110(3):1423-1428
Extensive molecular dynamic simulations (approximately 240 ns) have been used to investigate the conformational behavior of PrP106-126 prion peptide in four different environments (water, dimethyl sulfoxide, hexane, and trifluoroethanol) and under both neutral and acidic conditions. The conformational polymorphism of PrP106-126 in solution observed in the simulations supports the role of this fragment in the structural transition of the native to the abnormal form of prion protein in response to changes in the local environmental conditions. The peptide in solution is primarily unstructured. The simulations show an increased presence of helical structure in an apolar solvent, in agreement with the results from circular dichroism spectroscopy. In water solution, beta-sheet elements were observed between residues 108-112 and either residues 115-121 or 121-126. An alpha-beta transition was observed under neutral conditions. In DMSO, the peptide adopted an extended conformation, in agreement with nuclear magnetic resonance experiments. 相似文献
354.
Jacques Bros Henri Epstein Ugo Moschella 《Communications in Mathematical Physics》2002,231(3):481-528
We propose a general framework for studying quantum field theory on the anti-de-Sitter space-time, based on the assumption
of positivity of the spectrum of the possible energy operators. In this framework we show that the n-point functions are analytic in suitable domains of the complex AdS manifold, that it is possible to Wick rotate to the Euclidean
manifold and come back, and that it is meaningful to restrict AdS quantum fields to Poincaré branes. We give also a complete
characterization of two-point functions which are the simplest example of our theory. Finally we prove the existence of the
AdS-Unruh effect for uniformly accelerated observers on trajectories crossing the boundary of AdS at infinity, while that
effect does not exist for all the other uniformly accelerated trajectories.
Received: 3 December 2001 / Accepted: 26 July 2002 Published online: 21 October 2002 相似文献
355.
This paper considers the behaviour of a mechanical oscillator with cubic non-linearity subjected to a forcing excitation whose
frequency remains constant while the amplitude is ramped, growing until it reaches a predetermined value. We concentrate on
the nature of the basins of attraction whose size indicates the stability of the system, in a structural sense. The reduced
level of forecing at the initial stages of ramping produces a delay in bifurcational events when compared to the constant
sinusoidally forced counterpart. Preliminary results show that for some parameter values the area of basin does not increase
monotonically as the length of ramping is varied.
A preliminary version was presented at BIFCHAOS '92, Workshop held at L'Aquila, Italy, on 20–21 May 1992. 相似文献
356.
Dr. Ugo Jacovella Corentin Rossi Dr. Claire Romanzin Dr. Christian Alcaraz Dr. Roland Thissen 《Chemphyschem》2022,23(5):e202100871
Mass spectrometry is a powerful tool but when used on its own, without specific activation of ions, the ion mass is the single observable and the structural information is absent. One way of retrieving this information is by using ion–molecule reactions. We propose a general method to disentangle isomeric structures by combining mass spectrometry, tunable synchrotron light source, and quantum-chemistry calculations. We use reactive chemical monitoring technique, which consists in tracking reactivity changes as a function of photoionization energy i. e. the ionic structure. We illustrate the power of this technique with charge transfer reactions of C6H4+. isomers with allene and propyne and discuss its universal applicability. Furthermore, we emphasize the special reactivity characteristics of distonic ions, where strong charge transfer reactivity but very limited reactivity involving bond formation and following cleavages were observed and attributed to the unconventional ortho-benzyne distonic cation. 相似文献
357.
Renato Buzio Andrea Toma Francesco Buatier de Mongeot Ugo Valbusa 《Surface science》2007,601(13):2735-2739
We report for the first time on muscovite mica surfaces nanostructured by a low-energy defocused Ar ion beam: ripple structures self-organize on macroscopic areas, with wavelength and roughness in the range 40-140 nm and 0.5-15 nm respectively, according to ions dose. In detail we address structural and chemical variations of the surface layer induced by sputtering. X-ray Photoelectron Spectroscopy (XPS) survey spectra reveal selective sputtering and Al surface enrichment whereas Atomic Force Microscopy (AFM) force-spectroscopy experiments indicate reduced charging of irradiated specimens under aqueous electrolyte solutions. Such experimental evidences contribute to clarify the chemical and physical properties of nanostructured mica samples, in view of their potential use as templates for aligned deposition of organic molecules and investigations on nanolubrication phenomena. 相似文献
358.
359.
We study the structure of a modified Fukaya category ?(X) associated with a K3 surface X, and prove that whenever $X$ is an elliptic K3 surface with a section, the derived category of ?(X) is equivalent to a subcategory of the derived category of coherent sheaves on the mirror K3 surface .
Received: 20 October 1998 / Accepted: 15 March 1999 相似文献
360.
We show that the existence of a connection on a super vector bundle or on a principal super fibre bundle is equivalent to the vanishing of a cohomological invariant of the superbundle. This invariant is proved to vanish in the case of a De Witt base supermanifold. Finally, some examples are discussed. 相似文献