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61.
We correlate an X-ray determination of the molecular and crystal structures of 2-tert-butylanthracene and 2-tert-butylanthraquinone reported here with the previously reported dynamical nuclear magnetic resonance determination of the motions of the tert-butyl groups and their resident methyl groups in the solid state [P.A. Beckmann, K.S. Burbank, M.M.W. Lau, J.N. Ree, T.L. Weber, Chem. Phys. 290 (2003) 241]. 相似文献
62.
《中国颗粒学报》2008,6(6)
A two-dimensional discrete element model (DEM) simulation of cohesive polygonal particles has been developed to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The particle-particle interaction model used is based on a multi-contact principle.The first part of the study investigated particle discharge under gravity without vibration to determine the critical orifice size (Be) to just sustain flow as a function of particle shape. It is shown that polygonal-shaped particles need a larger orifice than circular particles. It is also shown that Be decreases as the number of particle vertices increases. Addition of circular particles promotes flow of polygons in a linear manner.The second part of the study showed that vibration could enhance flow, effectively reducing Be. The model demonstrated the importance of vibrator location (height), consistent with previous continuum model results, and vibration amplitude in enhancing flow. 相似文献
63.
Summary The structure and substructure changes in Al and dispersion-hardened Al alloy are studied after rapid deformation by explosion
and slow conventional deformation (cross-rolling and compression) using X-ray diffraction analysis and transmission electron
microscopy. Shock wave deformation generates a small dislocation density which does not produce any significant change in
the microstructure as well as in the texture of Al and Al alloy containing a different concentration of Al2O3 particles (4 and 7%). After slow conventional deformation, in particular after cross-rolling, significant variations are
observed due to the nonuniformly distributed high dislocation densities. 相似文献
64.
A. Šimůnek J. Vackář K. Kunc J. Hutter 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):245-249
A soft, norm-conserving pseudopotential for carbon is presented and its performance tested by calculations on atomic states
and on diamond: electronic energy levels of different atomic configurations, equilibrium lattice constant, bulk modulus, and
the TA(X) frozen-phonon frequency are accurately reproduced. Convergence of the total energy of diamond with the size of the
plane-wave basis set is compared for several frequently used pseudopotentials, and it is shown that calculations with the
reported pseudopotential can be performed at considerably lower cost than with the other norm-conserving pseudopotentials,
without loosing the accuracy of the latter in predicting structural and dynamical properties. The rapid convergence of the
results with the plane-wave cutoff is comparable to the performance of the Vanderbilt's ultrasoft pseudopotentials. The transferability
of the pseudopotential to other electronic configurations is discussed.
Received 8 September 1999 相似文献
65.
Jeroen Schillewaert 《Designs, Codes and Cryptography》2008,47(1-3):165-175
This work is inspired by a paper of Hertel and Pott on maximum non-linear functions (Hertel and Pott, A characterization of
a class of maximum non-linear functions. Preprint, 2006). Geometrically, these functions correspond with quasi-quadrics; objects
introduced in De Clerck et al. (Australas J Combin 22:151–166, 2000). Hertel and Pott obtain a characterization of some binary
quasi-quadrics in affine spaces by their intersection numbers with hyperplanes and spaces of codimension 2. We obtain a similar
characterization for quadrics in projective spaces by intersection numbers with low-dimensional spaces. Ferri and Tallini
(Rend Mat Appl 11(1): 15–21, 1991) characterized the non-singular quadric Q(4,q) by its intersection numbers with planes and solids. We prove a corollary of this theorem for Q(4,q) and then extend this corollary to all quadrics in PG(n,q),n ≥ 4. The only exceptions occur for q even, where we can have an oval or an ovoid as intersection with our point set in the non-singular part.
相似文献
66.
67.
D. Meyer W. Nolting 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):385-395
We compare different approximation schemes for investigating ferromagnetism in the periodic Anderson model. The use of several
approximations allows for a detailed analysis of the implications of the respective methods, and also of the mechanisms driving
the ferromagnetic transition. For the Kondo limit, our results confirm a previously proposed mechanism leading to ferromagnetic
order, namely an RKKY exchange mediated via the formation of Kondo screening clouds in the conduction band. The contrary case is found in the intermediate-valence regime.
Here, the bandshift correction ensuring a correct high-energy expansion of the self-energy is essential. Inclusion of damping
effects reduces stability of the ferromagnetic phase.
Received 5 June 2000 and Received in final form 3 August 2000 相似文献
68.
M. Manekar S. B. Roy 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(1):19-25
We investigate the electronic structure of
Sr2FeMoO6/SrTiO3 (SFMO/STO) multilayers using the
ab initio Full Potential Linearized Augmented Plane Wave
method in order to study their properties within the GGA and GGA+U methods. We examin more especially the role of the interface
on the magnetic and transport properties of these multilayers taking into account a possible Fe deficiency at the interface
and we show that bulk behaviour is rapidly recovered due to the strong localization of
the interfacial perturbation. For perfect interfaces, the whole structure is found half-metallic within the GGA+U method;
the situation
being ambiguous within the GGA method where SFMO is at the limit of being half-metallic depending on the structural deformation
induced by the STO layer. This leads us to the conclusion that such a system could be used as injection electrode and tunnel
barrier in magnetic tunnel junctions with a fully spin polarized injected current.
For Fe deficient interfaces, we show that the interfacial densities of states are nearly unpolarized showing that this kind
of
imperfection has potentially a strong impact on the properties
of the multilayers. 相似文献
69.
70.
Anna Bosi 《Meccanica》2007,42(5):477-485
A wavelet-based methodology for detecting critical events in displacement and temperature histories, obtained by monitoring
in-situ thermoelastic structures, is proposed. It is based on the wavelet analysis of thermoelastic potentials furnishing
also the possibility to detect separately cases in which sudden jumps occur in the displacement history from those in which
they occur on temperature history. 相似文献