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461.
A. Freyn G. Vasseur P. Schmitteckert D. Weinmann G.-L. Ingold R. A. Jalabert J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):253-266
We investigate the relationship between persistent currents in multi-channel
rings containing an embedded scatterer and the conductance through the same
scatterer attached to leads. The case of two uncoupled channels corresponds to
a Hubbard chain, for which the one-dimensional embedding method is readily
generalized. Various tests are carried out to validate this new procedure, and
the conductance of short one-dimensional Hubbard chains attached to perfect
leads is computed for different system sizes and interaction strengths.
In the case of two coupled channels the conductance can be obtained from a
statistical analysis of the persistent current or by reducing the
multi-channel scattering problem to several single-channel setups. 相似文献
462.
Fluid flow and heat and mass transfer induced by double-diffusive natural convection in a horizontal porous layer subjected
to vertical gradients of temperature and concentration are studied analytically and numerically using the Brinkman-extended
Darcy model. Both cases of rigid and free horizontal boundaries are examined in the present study. The parameters governing
the problem are the Rayleigh number RT, the Lewis number Le, the buoyancy ratio N, the Darcy number Da and the aspect ratio Ar. The analytical solution is based on the parallel flow approximation. The critical
Rayleigh number corresponding to the onset of the parallel flow in this system is determined analytically as a function of
Le, N and Da. For sufficiently small Da, both free and rigid boundaries yield results which are identical to those predicted by
the Darcy model. The present investigation shows that there exists a region in the plane (N, Le) where the convective flow is not possible in the layer regardless of the Rayleigh and Darcy numbers considered.
Received on 21 December 1998 相似文献
463.
Mohamed Amine Berkal Quentin Palas Estelle Ricard Christine Lartigau-Dagron Luisa Ronga Jean-Jacques Toulmé Corinne Parat Corinne Nardin 《Macromolecular bioscience》2023,23(8):2200508
N-phosphonomethyle-glycine (glyphosate) is the most widely used pesticide worldwide due to its effectiveness in killing weeds at a moderate cost, bringing significant economic benefits. However, owing to its massive use, glyphosate and its residues contaminate surface waters. On site, fast monitoring of contamination is therefore urgently needed to alert local authorities and raise population awareness. Here the hindrance of the activity of two enzymes, the exonuclease I (Exo I) and the T5 exonuclease (T5 Exo) by glyphosate, is reported. These two enzymes digest oligonucleotides into shorter sequences, down to single nucleotides. The presence of glyphosate in the reaction medium hampers the activity of both enzymes, slowing down enzymatic digestion. It is shown by fluorescence spectroscopy that the inhibition of ExoI enzymatic activity is specific to glyphosate, paving the way for the development of a biosensor to detect this pollutant in drinking water at suitable detection limits, i.e., 0.6 nm . 相似文献
464.
The structure of the intercalates in which poly(ethylene oxide), PEO, is the host component and para-disubstituted benzenes are the guest molecules is completely elucidated by X-ray diffractometry, polarized FTIR spectrography, and calorimetry. It is shown that the association of these molecules results from the adaptation of the shape of their external surfaces. On this basis the possibility of formation of structure involving PEO and small molecules is discussed. 相似文献
465.
Lahoucine Hajji Ramiro Guerrero Santos Grard Joseph Beinert Jean-Edouard Herz Andr Bieber Jean-Jacques Andr 《Macromolecular theory and simulations》1995,4(6):1105-1126
Hemibenzopinacolate radicals may be incorporated in a polymer chain and the latter used as a macromolecular initiator. Kinetics of polymerization are strongly dependent on the substitution of the pinacolate. A large family of substituted (CH3)3SiOC(C6H5)2 radicals has been synthesized and studied by electron spin resonance (ESR) and semiempirical molecular orbital calculations. ESR spectra are well resolved and, except for one derivative, allow an unambiguous determination of the hyperfine coupling splitting (HFS) constants. The ground state properties have been calculated within different approximations, namely MNDO, AM1 and PM3 for the geometry optimization and INDO for spin density. Geometries obtained within AM1 and PM3 approximations are satisfactory. The HFS constants evaluated using McConnell type relations and spin densities are in a quite good agreement with the experimental ones. It turns out that the effect of substitution on kinetics of polymerization cannot be attributed to any drastic change in the charge distribution. 相似文献
466.