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921.
A mass transfer model originally proposed for the permeation of zinc and l-phenylalanine was slightly modified and used for calculating the mass transfer resistances in lactic acid permeation (using the secondary amine Amberlite LA-2 as a carrier) and l-leucine permeation (using the quaternary ammoniumchloride Aliquat 336 as a carrier). The results show that under optimized conditions lactic acid permeation is controlled by the rate of reaction and that l-leucine permeation is controlled by the rate of reaction and the diffusion through the emulsion globule. The model results were compared with batch experiments separating lactic acid and l-leucine from real fermentation broths. The comparison shows that the separation rate is affected by co-transport of pH regulating agents and to a smaller extent by the co-transport of water. 相似文献
922.
J. Suhonen J. Toivanen A. S. Barabash I. A. Vanushin V. I. Umatov R. Gurriarán F. Hubert Ph. Hubert 《Zeitschrift für Physik A Hadrons and Nuclei》1997,358(3):297-301
We apply the self-consistent renormalized proton-neutron QRPA (RQRPA) method to calculate the two-neutrino double beta (2νββ) decay matrix elements associated with the ground-state and excited-state transitions of the 82Se → 82Kr decay. The RQRPA method is an extension of the pnQRPA method and promotes the Pauli exclusion principle violated by the pnQRPA ground state and yields more stable nuclear matrix elements with increasing strength of the proton-neutron interaction. In the present work the RQRPA wave functions are also used to evaluate 2νββ-decay rates to excited final states. The resulting theoretical half lives are compared with the new stringent experimental limits obtained by using a HPGe detector and external sources of enriched selenium. 相似文献
923.
P. Karamian‐Surville J. Sanchez‐Hubert E. Sanchez Palencia 《Mathematical Methods in the Applied Sciences》2003,26(17):1451-1485
We consider problems of statics of thin elastic shells with hyperbolic middle surface subjected to boundary conditions ensuring the geometric rigidity of the surface. The asymptotic behaviour of the solutions when the relative thickness tends to zero is then given by the membrane approximation. It is a hyperbolic problem propagating singularities along the characteristics. We address here the reflection phenomena when the propagated singularities arrive to a boundary. As the boundary conditions are not the classical ones for a hyperbolic system, there are various cases of reflection. Roughly speaking, singularities provoked elsewhere are not reflected at all at a free boundary, whereas at a fixed (or clamped) boundary the reflected singularity is less singular than the incident one. Reflection of singularities provoked along a non‐characteristic curve C are also considered. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
924.
Claude Gabrielli Patrick Hemery Pierre Letellier Michele Masure Hubert Perrot Marie-Isabelle Rahmi Mireille Turmine 《Journal of Electroanalytical Chemistry》2004,570(2):275-289
Models of an ion selective electrode involving an ionophore and mobile sites in a membrane are proposed. The first model, called the phase boundary potential model, supposed thermodynamic equilibrium; it allows the concentrations of the various species to be calculated. Then, a kinetic model, which takes into account the ionic transfer at the membrane|solution interfaces, was derived. The impedance of the membrane was calculated. It shows that a membrane with nernstian behavior shows only one capacitive loop in the impedance diagram, which is related to the conductivity and dielectric properties of the material of the membrane. Non-nernstian behavior is related to slow ionic transfer at the membrane|solution interfaces or/and transport limitation of the species in the membrane. Finite rate constants of the ionic transfer lead to a capacitive loop in the middle frequency range, whereas finite rate transport leads to a diffusional impedance in the low frequency range. 相似文献
925.
926.
927.
Preparation and Properties of Phosphane-Boranes Derived from Polyfunctional Phosphanes; Crystal Structures of Bis(boranatodiphenylphosphonio)methane and Tetrakis[(boranato-diphenylphosphonio)methyl]methane Bis(boranatodiphenylphosphonio)methane has been prepared in pure form from Ph2PCH2PPh2 (dppm) via two synthetic routes and its crystal structure determined. The molecule adopts a conformation very similar to that of the parent dppm ligand, which reflects the influences of the repulsive charges in the functional groups. Analogous phosphine-boranes were obtained from 1,1,1-tris(diphenylphosphinomethyl)ethane and tetrakis(diphenylphosphinomethyl)methane. The crystal structure has also been determined for the tetra-borylated derivative of the latter. A highly symmetrical arrangement has been found which corresponds to a relaxed conformation of the four dipolar groups. From C(CH2PPh2)4 and H2BBr · SMe2 an ionic, spirobicyclic Product was obtained, which resembles the monocyclic analogues previously described in its Properties and spectroscopic data. 相似文献
928.
The kinetic model of column chromatography is revisited to explicitly show that this approach yields, when neglecting axial dispersion, a rather simple analytical expression depending only on two dimensionless parameters, namely a dimensionless kinetic retention parameter and a dimensionless time parameter. An expression for the time corresponding to the maximum of the peak is also proposed. 相似文献
929.
Hubert Delange 《Monatshefte für Mathematik》1988,106(2):115-138
We show how are located the positive roots of the Euler polynomiale
n
of degreen. We give an upper bound and a lower bound for the greatest root. This permits to determine an integerv
(n) such that the number of positive roots ofE
n
is eitherv
(n)
orv
(n)
+2. We also study the behaviour of ther-th positive root ofE
n
asn tends to infinity. 相似文献
930.