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**排序方式：**共有4564条查询结果，搜索用时 0 毫秒

1.

《Communications in Nonlinear Science & Numerical Simulation》2007,12(5):784-793

We consider the dynamical behavior of the strongly damped wave equations under homogeneous Neumann boundary condition. By the property of limit set of asymptotic autonomous differential equations, we prove that in certain parameter region, the system has a one-dimensional global attractor, which is a periodic horizontal curve. 相似文献

2.

《Communications in Nonlinear Science & Numerical Simulation》2007,12(3):243-253

Navier–Stokes equations (NS) admit transformations which transform a solution to another solution (galilean transformation, scaling transformation, …). They also admit viscosity dependent transformations which transform a solution to a solution of another NS with different viscosity. These particular transformations are called symmetries of NS. Each of them has a physical role (such as conservation laws, …). A consistent turbulence model should then remain invariant under these symmetry transformations. Unfortunately, this is not the case of several models.In this article, a class of subgrid-scale models preserving the symmetries of NS is built. This class is then refined such that the models respect the second law of thermodynamics. One of the simplest models of the class is tested to the flow in a ventilated room. Better results than those provided by Smagorinsky and dynamic models are obtained. 相似文献

3.

Jie-Fang Zhang 《Acta Mechanica Solida Sinica》1991,4(2):139-151

Based on D'Alembert's principle of a mechanical system relative to non-inertial frame and by introducing the concept of the generalized inertial potential, new forms of differential equations of motion of a mechanical system with holonomic and the non-holonomic constraints relative to the non-inertial frame are obtained. The merits and demerits between our method and the Newtonian dynamic method as well as the analytic dynamic method are discussed comparatively. Finally, two examples are given to illustrate the application of the motive differential equations in the new forms. 相似文献

4.

《Nonlinear Analysis: Theory, Methods & Applications》2005,60(3):429-442

In this paper, we combine the monotone iterative technique with fixed point theory to investigate the extremal solutions of nonlinear integro-differential equations on time scales. Several important lemmas and existence criteria are obtained. 相似文献

5.

《Communications in Nonlinear Science & Numerical Simulation》2006,11(3):376-390

The Boussinesq system is investigated by using the tanh method and the sine–cosine method. A variety of exact travelling wave solutions with compact and noncompact structures are formally obtained. The study shows that each method gives distinct solutions and one method complements the other. 相似文献

6.

Theoretical and Mathematical Physics - The initial-boundary value problems for the matrix Lakshmanan–Porsezian–Daniel system are studied by utilizing the Fokas unified transform... 相似文献

7.

《The Journal of chemical thermodynamics》2006,38(1):20-33

The apparent molar volumes of l-alanine, dl-serine, dl-threonine, l-histidine, glycine, and glycylglycine in water and in the aqueous solutions of NaCl and DMSO with various concentrations at

*T*= 298.15 K have been measured by the precise vibrating-tube digital densimeter. The calculated partial molar volumes at infinite dilution have been used to obtain corresponding transfer volumes from water to various solutions. The experimental results show that the standard partial molar volumes of the above amino acids and peptide at the dilute DMSO aqueous solutions are very close to those in water. However, the volumes show several types of variations with the increase of the concentrations of DMSO due to different types of side chain of amino acids, which should be discussed specifically. The NaCl changes considerably the infinite dilution standard partial molar volumes of the above amino acids and peptide in the aqueous solutions. The infinite dilution standard partial molar volumes of the each amino acids and peptide increase with the concentrations of NaCl. The experimental results have been rationalized by a cosphere overlap model. 相似文献8.

《Fluid Phase Equilibria》2005,227(2):267-274

A stability analysis of a widely used model of the Gibbs energy of fluid mixtures is presented. In that model, the solutes and the solvent are treated differently (asymmetric normalization). For the solutes, an infinitely dilute reference state is used, the ideal solution is defined using molalities, and a virial expansion in molalities is used for describing the Gibbs excess energy

*G*^{E}. That model is identical with the well-known Pitzer model if only uncharged molecular species are present. An unusual stability behavior of that model is observed. Instability is predicted for a wide range of concentrations in an important range of model parameters. Despite this, for principal reasons, that model does not allow determining the concentrations in coexisting phases in a physically meaningful way. For example, for binary systems it always predicts that only the pure components are globally stable. To illustrate those findings, the system hydrogen sulfide–water is discussed, for which the Pitzer model is often used in practice. For comparison with the Pitzer model the well-known Margules*G*^{E}-model is used that shows no unexpected stability behavior. Conversion rules are presented that allow finding parameters for the well-behaved Margules model from those of the Pitzer model. The application is again demonstrated using the system hydrogen sulfide–water. 相似文献9.

《Tetrahedron: Asymmetry》2005,16(6):1085-1089

Ytterbium trifluoromethanesulfonate promoted radical atom-transfer addition of 3-bromoacetyl-2-oxazolidinones to norbornadiene afforded stereoselectively the corresponding 5-

*exo*-3-bromo-5-nortricycleneacetic acid derivatives in good yields. Following clean tri(trimethylsilyl)silane reduction of the bromides, 3-*exo*-nortricycleneacetic acid derivatives were obtained with excellent diastereoselectivities (90–96% de) when using the chiral 4-isopropyl- and 4-benzyl-substituted 2-oxazolidinone auxiliaries. The stereochemistry of the studied compounds was investigated by 1D and 2D NMR spectroscopy. 相似文献10.

《Polyhedron》1987,6(6):1313-1317

Nickel(II) perchlorate and nitrate complexes containing dimethyl, di-

*n*-propyl, di-*n*-butyl, di-*i*-butyl and di-*t*-butyl sulfoxides have been synthesized and characterized by IR and electronic spectroscopies, magnetic-susceptibility and electrolytic-conductance measurements. In the complexes containing perchlorate, the metal: sulfoxide molar ratio is 1:6 and the perchlorate groups are ionic. In the nitrate compounds, the molar ratio decreases from 1:6 to 1:2 according to the increase in the steric bulk of the alkyl group from methyl to*t*-butyl. The nitrate group may either be non-coordinating or behave as a monodentate or bidentate ligand. All the complexes contain O-bonded sulfoxide molecules and are characterized as high-spin, with an octahedral or distorted octahedral geometry. The dialkyl sulfoxides studied in this work fall in the same position as dimethyl sulfoxide in the spectrochemical and nephelauxetic series. Electrolytic conductivities suggest that the compounds containing ionic nitrate exhibit sulfoxide—nitrate exchange in nitromethane solutions. 相似文献