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781.
782.
Michel Bouchon 《Pure and Applied Geophysics》1996,148(1-2):3-20
We review the application of the discrete wave number method to problems of scattering of seismic waves formulated in terms of boundary integral equation and boundary element methods. The approach is based on the representation of the diffracting surfaces and interfaces of the medium by surface distributions of sources or by boundary source elements, the radiation from which is equivalent to the scattered wave field produced by the diffracting boundaries. The Green's functions are evaluated by the discrete wave number method, and the boundary conditions yield a linear system of equations. The inversion of this system allows the calculation of the full wave field in the medium. We investigate the accuracy of the method and we present applications to the simulation of surface seismic surveys, to the diffraction of elastic waves by fractures, to regional crustal wave propagation and to topographic scattering. 相似文献
783.
Wei Mozheng 《大气科学进展》1997,14(3):355-368
We develop the finite-mode model for a two-dimensional Euler system on the sphere based on Hopped’s discovery in group theory. This model strives to keep as many invariants of the original Euler equation as possible. Theoretically, the number of invariants in this model is limited only by computing power. At present, almost all the popular numerical models in weather and climate researches such as numerical weather prediction models and general circulation models (GCMs) use spectral method. However all these spectrally truncated models do not keep all the invariants except for the energy and the enstrophy. By using this model one is able to study the influence from some other lost invariants. The result from this model is expected to be closer to that of the original Euler equations than from ordinary spectrally truncated models. The relevant fundamental equations and important formulas for this model are given explicitly. 相似文献
784.
A BFG model for calculation of tidal current and diffusion of pollutants in nearshore areas 总被引:4,自引:0,他引:4
ABFGmodelforcalculationoftidalcurrentanddiffusionofpollutantsinnearshoreareas¥ShiFengyan;andZheng;Lianyuan(StateKeyLaboratory... 相似文献
785.
The assumption that the East and North deck slopes of a pitch–roll buoy respond to East and North sea slopes as simple harmonic oscillators is routinely made by the National Data Buoy Center (NDBC) and others producing directional wave data. Although directional wave data derived with this assumption usually appear to be of good quality, the validity of the assumption has not previously been more directly demonstrated. In this paper, a method is proposed to judge the validity of the assumption for any set of time series records of buoy angular motion. The proposed method is applied to 200 record sets taken by an NDBC buoy located at ocean station 46024, and to five record sets taken by another NDBC buoy at 46051. For the 46024 data, it was demonstrated that the simple harmonic oscillator assumption was near perfectly valid. For the smaller 46051 data set, the simple harmonic oscillator assumption was shown to be slightly less valid. 相似文献
786.
In this paper we use an industrial Navier–Stokes (NS) solver to model high amplitude internal waves. The model simulates a fluid with a shallow upper layer with linear stratification and a deep lower layer with constant density, relevant to conditions in the ocean at several locations. Waves are generated by trapping a volume of light water behind a gate in one end of the numerical wave tank. The velocity and vorticity fields predicted by the model agree well with experiment. The high amplitude waves produced by the NS solver experience an upper bound on the velocity and a broadening in agreement with experiment. These effects have not previously been captured by theoretical models. 相似文献
787.
788.
Tidal elevation data are presented for places along the length of the Fleet, which is a tidal lagoon behind Chesil Beach on the south coast of England. Harmonic analysis of the data is not able to represent the observations adequately, particularly at the inner end of the lagoon. However, careful inspection of the data shows that the tidal regime is capable of being understood in terms of the non-linear propagation of long waves in very shallow water. Distortion of the tidal wave by unequal progression speeds of high and low water, and the set-up of mean level by frictional effects, are shown to be the important physical mechanisms controlling the observed water level fluctuations. A one-dimensional numerical model which incorporates these processes is able to reproduce the observations satisfactorily. Whilst the model predicts strong effects of wind stress, the meteorological influences in the observed data appear to be largely due to external surges in the English Channel which propagate into the lagoon through its entrance. 相似文献
789.
Fengyan Shi Robert A. Dalrymple James T. Kirby Qin Chen Andrew Kennedy 《Coastal Engineering》2001,42(4):258
Based on the fully nonlinear Boussinesq equations in Cartesian coordinates, the equations in generalized coordinates are derived to adapt computations to irregularly shaped shorelines, such as harbors, bays and tidal inlets, and to make computations more efficient in large near-shore regions. Contravariant components of velocity vectors are employed in the derivation instead of the normal components in curvilinear coordinates or original components in Cartesian coordinates, which greatly simplifies the equations in generalized curvilinear coordinates. A high-order finite difference scheme with staggered grids in the image domain is adopted in the numerical model. The model is applied to five examples involving curvilinear coordinate systems. The results of these cases are in good agreement with analytical results, experimental data, and the results from the uniform grid model, which shows that the model has good accuracy and efficiency in dealing with the computations of nonlinear surface gravity waves in domains with complicated geometries. 相似文献
790.
Based on the classical Boussinesq model by Peregrine [Peregrine, D.H., 1967. Long waves on a beach. J. Fluid Mech. 27 (4), 815–827], two parameters are introduced to improve dispersion and linear shoaling characteristics. The higher order non-linear terms are added to the modified Boussinesq equations. The non-linearity of the Boussinesq model is analyzed. A parameter related to h/L0 is used to improve the quadratic transfer function in relatively deep water. Since the dispersion characteristic of the modified Boussinesq equations with two parameters is only equal to the second-order Padé expansion of the linear dispersion relation, further improvement is done by introducing a new velocity vector to replace the depth-averaged one in the modified Boussinesq equations. The dispersion characteristic of the further modified Boussinesq equations is accurate to the fourth-order Padé approximation of the linear dispersion relation. Compared to the modified Boussinesq equations, the accuracy of quadratic transfer functions is improved and the shoaling characteristic of the equations has higher accuracy from shallow water to deep water. 相似文献