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131.
132.
Claesson PM Kjellin M Rojas OJ Stubenrauch C 《Physical chemistry chemical physics : PCCP》2006,8(47):5501-5514
Short-range interactions between surfactant and lipid layers are of great importance in technical applications in complex fluids such as foams, dispersions and emulsions, as well as in the formulation and performance of dispersants, detergents and flocculants. It is also of utmost importance in biological systems where interactions between biomembranes influence a range of processes. The field of short-range interactions has been thoroughly investigated during the past 30 years, following the emergence of a number of techniques to measure interaction forces. Thus, our understanding has increased considerably and it is timely to summarize relevant knowledge accumulated in this area. In this review we focus on the nature of short-range interactions between non-ionic and zwitterionic surfactant and lipid layers exposing their polar groups to the surrounding medium. We discuss the complex interplay of short-range (van der Waals, hydration, steric and other) forces based on recent theoretical and experimental results. 相似文献
133.
Orlando R Torres FJ Pascale F Ugliengo P Zicovich-Wilson C Dovesi R 《The journal of physical chemistry. B》2006,110(2):692-701
The vibrational spectrum of the Si-free katoite hydrogarnet (116 atoms in the unit cell) has been calculated at the periodic ab initio quantum mechanical level with the CRYSTAL program, by using a Gaussian type basis set and the hybrid B3LYP Hamiltonian. The harmonic frequencies at the Gamma point have been obtained by diagonalizing the mass-weighted Hessian matrix, that is evaluated by numerical differentiation of the analytical first derivatives of the energy with respect to the atomic Cartesian coordinates. The parameters controlling the numerical differentiation, as well as the numerical integration of the exchange-correlation functional for the self-consistent field (SCF) calculation, are shown to affect the obtained frequencies by less than 3 cm-1. Before diagonalization, the dynamical matrix is transformed to a block diagonal form according to the irreducible representations of the point group, so that the 345 vibrational modes are automatically classified by symmetry. Various tools are adopted (graphical representation, isotopic substitution, "freezing" part of the unit cell) that permit a complete classification of normal modes and, in particular, an analysis of the modes in terms of simple models (octahedra modes, Ca modes, H stretching, bending, rotations). The harmonic OH stretching band (48 modes) is quite narrow (20 cm-1), indicating that the interaction among OH groups is very weak. As the OH stretching modes are known to be totally separable from the other modes and strongly anharmonic, the one-dimensional Schroedinger equation for the anharmonic oscillator is solved numerically for the two extreme situations, corresponding to the vibration of one decoupled OH and of all 48 OH groups moving in phase. The anharmonic frequencies are 3682 and 3673 cm-1, respectively, in good agreement with IR experiments (a single band at 3661 cm-1 with a width at half band height of 33 cm-1) and confirming that the interaction between OH groups is extremely weak. 相似文献
134.
Pavone M Sillanpää A Cimino P Crescenzi O Barone V 《The journal of physical chemistry. B》2006,110(33):16189-16192
This letter presents the results of a thorough computational investigation of two prototypical nitroxide spin probes in two different protic solvents, namely water and methanol, based on the combined use of Car-Parrinello molecular dynamic simulations and static cluster/continuum quantum chemical computations. Remarkable changes in solvation networks were found on going from aqueous to methanolic solutions. Moreover, despite their structural similarity, the two nitroxide probes display quite different behaviors in water. This provides a rationalization of indirect experimentally available indications. Eventually, the combination of static and dynamical ab initio methods exploited in the present study allows to dissect many subtle features of the nitroxide-solvent interaction, and also allows for an analysis of solvent effects on magnetic parameters (hyperfine coupling constants and g-tensor shift). 相似文献
135.
Salvatore Capozziello Orlando Luongo 《International Journal of Theoretical Physics》2013,52(8):2698-2704
We show that quantum decoherence, in the context of observational cosmology, can be connected to the cosmic dark energy. The decoherence signature could be characterized by the existence of quantum entanglement between cosmological eras. As a consequence, the Von Neumann entropy related to the entanglement process, can be compared to the thermodynamical entropy in a homogeneous and isotropic universe. The corresponding cosmological models are compatible with the current observational bounds being able to reproduce viable equations of state without introducing a priori any cosmological constant. In doing so, we investigate two cases, corresponding to two suitable cosmic volumes, V∝a 3 and V∝H ?3, and find two models which fairly well approximate the current cosmic speed up. The existence of dark energy can be therefore reinterpreted as a quantum signature of entanglement, showing that the cosmological constant represents a limiting case of a more complicated model derived from the quantum decoherence. 相似文献
136.
The “supercell” scheme is applied to the study of local defects in MgO (Ca substitution, cation and anion vacancies) and bulk silicon (carbon substitution). The trend of the quantities of interest (defect formation energy, geometrical relaxation, charge distribution around the defect) as a function of the supercell size is explored; when neutral defects are considered, supercells containing 50 to 100 atoms are large enough to allow for most of the nuclear and electronic relaxation and to produce a negligible interaction between defects in different cells. These conclusions apply both to ionic and covalent host crystals. Present day ab initio quantum mechanical periodic computer programs can handle cells of such a size at a relatively low cost and high numerical accuracy. When charged defects are considered (vacancies in MgO), the supercell scheme must be modified in order to avoid Coulomb divergencies, but the usually adopted correction, which consists in introducing a compensating uniform background of charge, generates spurious higher order electrostatic interactions, which are far from being negligible. The resulting defect formation energies show very slow, if any, convergence trends and “a posteriori” semiclassical corrections proposed in the literature do not represent a general solution to the problem. On the other hand, other properties, such as atom relaxation and charge distribution, show a much faster convergence than energy with respect to the cell size. 相似文献
137.
The thorny issue of relating information theory to cosmology is here addressed by assuming a possible connection between quantum entanglement measures and observable universe. In particular, we propose a cosmological toy model, where the equation of state of the cosmological fluid, which drives the today observed cosmic acceleration, can be inferred from quantum entanglement between different cosmological epochs. In such a way the dynamical dark energy results as byproduct of quantum entanglement. 相似文献
138.
The lateral Casimir-Polder force between an atom and a corrugated surface should allow one to study experimentally nontrivial geometrical effects in the electromagnetic quantum vacuum. Here, we derive the theoretical expression of this force in the scattering approach. We show that large corrections to the "proximity force approximation" could be measured using present-day technology with a Bose-Einstein condensate used as a vacuum field sensor. 相似文献
139.
E. Cappelli C. Scilletta G. Mattei V. Valentini S. Orlando M. Servidori 《Applied Physics A: Materials Science & Processing》2008,93(3):751-758
The structure of thin films deposited by pulsed laser ablation (PLD) is strongly dependent on experimental conditions, like
laser wavelength and fluence, substrate temperature and pressure. Depending on these parameters we obtained various kinds
of carbon materials varying from dense, mainly tetrahedral amorphous carbon (ta-C), to less compact vertically oriented graphene
nano-particles.
Thin carbon films were grown by PLD on n-Si 〈100〉 substrates, at temperatures ranging from RT to 800°C, from a rotating graphite target operating in vacuum. The laser ablation of the graphite target was performed by a UV pulsed ArF excimer laser (λ=193 nm) and a pulsed Nd:YAG laser, operating in the near IR (λ=1064 nm).
The film structure and texturing, characterised by X-ray diffraction analysis, performed at grazing incidence (GI-XRD), and
the film density, evaluated by X-ray reflectivity measurements, are strongly affected both by laser wavelength and fluence
and by substrate temperature.
Micro-Raman and GI-XRD analysis established the progressive formation of aromatic clusters and cluster condensation into vertically
oriented nano-sized graphene structures as a direct function of increasing laser wavelength and deposition temperature. The
film density, negatively affected by substrate temperature and laser wavelength and fluence, in turn, results in a porous
bulk configuration and a high macroscopic surface roughness as shown by SEM characterisation. These structural property modifications
induce a relevant variation also on the emission properties of carbon nano-structures, as evidenced by field emission measurements.
This work is dedicated to our friend Giorgio who passed away 20th August. 相似文献
140.
Giustino Orlando Annalisa Chiavaroli Sabrina Adorisio Domenico V. Delfino Luigi Brunetti Lucia Recinella Sheila Leone Gokhan Zengin Alessandra Acquaviva Paola Angelini Giancarlo Angeles Flores Roberto Venanzoni Simonetta Cristina Di Simone Francesca Di Corpo Andrei Mocan Luigi Menghini Claudio Ferrante 《Molecules (Basel, Switzerland)》2021,26(15)
Prunus mahaleb L. fruit has long been used in the production of traditional liqueurs. The fruit also displayed scavenging and reducing activity, in vitro. The present study focused on unravelling peripheral and central protective effects, antimicrobial but also anti-COVID-19 properties exerted by the water extract of P. mahaleb. Anti-inflammatory effects were studied in isolated mouse colons exposed to lipopolysaccharide. Neuroprotection, measured as a blunting effect on hydrogen-peroxide-induced dopamine turnover, was investigated in hypothalamic HypoE22 cells. Antimicrobial effects were tested against different Gram+ and Gram- bacterial strains. Whereas anti-COVID-19 activity was studied in lung adenocarcinoma H1299 cells, where the gene expression of ACE2 and TMPRSS2 was measured after extract treatment. The bacteriostatic effects induced on Gram+ and Gram- strains, together with the inhibition of COX-2, TNFα, HIF1α, and VEGFA in the colon, suggest the potential of P. mahaleb water extract in contrasting the clinical symptoms related to ulcerative colitis. The inhibition of the hydrogen peroxide-induced DOPAC/DA ratio indicates promising neuroprotective effects. Finally, the downregulation of the gene expression of ACE2 and TMPRSS2 in H1299 cells, suggests the potential to inhibit SARS-CoV-2 virus entry in the human host. Overall, the results support the valorization of the local cultivation of P. mahaleb. 相似文献