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991.
The nucleon electromagnetic form factorsG
E
P
(q2),G
M
P
(q2) and the axial-vector form factor GA(q2) are studied in a relativistic model of independent quarks confined by an equally mixed scalar-vector square root potentialV
q(r)=1/2(1+γ
0)(ar
1/2+ν
0) taking into account the appropriate centre-of-mass corrections. The respective root-mean-square radii associated withG
E
P
(q2) and G
A
(q2) come out as [〈r
2〉
E
P
]1/2=0.86 fm and 〈r
A
2
〉1/2=0.88 fm. Restoration of chiral symmetry in this model is discussed to derive the pion-nucleon form factorG
πNN(q2) and consequently the pion-nucleon coupling constant is obtained asg
πNN(q2)=12.81 as compared tog
πNN(q2)exp⋍13. 相似文献
992.
废水中铜银的分离和银的回收研究黄秀山(四川三峡学院化学系万县634000)关键词分解电压,还原电势,回收一、引言本实验采用电解还原的方法回收贵金属银。目前此法主要用于回收废水中的铬、汞等,对银的研究很少。曾有人进行过自然渗析还原法回收银的研究。用自然... 相似文献
993.
T. D. J. Perkins J. E. J. Mills P. M. Dean 《Journal of computer-aided molecular design》1995,9(6):479-490
Summary Steric complementarity is a prerequisite for ligand-receptor recognition; this implies that drugs with a common receptor binding site should possess sterically similar binding surfaces. This principle is used as the basis for an automatic and unbiased method that superposes molecules. One molecule is rotated and translated to maximize the overlap between the two molecular surface volumes. A fast grid-based method is used to determine the extent of this overlap, and this is optimized using simulated annealing. Matches with high steric similarity scores are then sorted on the basis of both hydrogen-bond and electrostatic similarity between the matched molecules. Flexible molecules are treated as a set of rigid representative conformers. The algorithm has correctly predicted superpositions between a number of pairs of molecules, according to crystallographic data from ligands that have been co-crystallized at common enzyme binding sites. 相似文献
994.
995.
996.
Solutions of the Fokker-Planck (Kramers) equation in position-velocity space for the double-well potentiald
2x2/2+d4x4/4 in terms of matrix continued fractions are derived. It is shown that the method is also applicable to a Boltzmann equation with a BGK collision operator. Results of eigenvalues and of the Fourier transform of correlation functions are presented explicitly. The lowest nonzero eigenvalue is compared with the escape rate in the weak noise limit for various damping constants and the susceptibility is compared with the zero-friction-limit result. 相似文献
997.
Using the perturbation theory of Weekset al the first order quantum correction to the free energy of a simple fluid characterised by a double Yukawa potential function
has been expressed in a simple closed analytical form which allows numerical calculation simply on a desk calculator. 相似文献
998.
A novel formulation of the method of fundamental solutions for the numerical solution of plane biharmonic problems, based on the simple layer potential representation of Fichera, is presented. The applicability and accuracy of the method are demonstrated by examining its performance on a set of practical problems arising in Stokes fluid flow. 相似文献
999.
Experiments with heavy ions at moderate energies show the importance of deformation in heavy ion collisions. A deformation
model which takes deformation dynamically into account is developed. Having described fusion and deep inelastic collision
for a very heavy system (Xe + Bi) and a medium heavy system (Ar + Th) at various energies successfully, we turn to some comparatively
lighter heavy ions where fusion is the most dominant feature. Fusion cross-sections for six pairs of lighter systems (35Cl +116Sn,58Ni+62Ni,35Cl+62Ni,32S+24Mg,24Mg+24Mg and12C+27Al) have been obtained using our deformation model which agree well with experiment. The two-slope-behaviour of fusion excitation
function which is an important feature of light ion fusion systematics is also obtained, in our model calculations for all
the systems studied. 相似文献
1000.
B. H. Lavenda 《Foundations of Physics Letters》1988,1(4):333-341
Einstein's radiation mechanism is generalized to account for the possibility of population inversion by placing a nonlinear bound on the growth of an unstable perturbation. The nonstationary linear mechanism of relaxation to blackbody radiation below threshold is studied. The nonstationary photon distribution is the negative binomial distribution, and casting it as a law of error, for which the most probable value is the mean value, gives the expression for the statistical entropy. The second law yields a nonequilibrium generalization of Planck's radiation law. The nonlinear mechanism leading to the transformation from the negative binomial probability distribution, for chaotic light, to a Poisson probability distribution, for coherent light, is then analyzed. A criterion for lasing is given in terms of the chemical potential of radiation which is compared to the inequality for the transition from quantum to classical statistics. 相似文献