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891.
Simulation of Fully Nonlinear 3-D Numerical Wave Tank 总被引:6,自引:0,他引:6
A fully nonlinear numerical wave tank (NWT) has been simulated by use of a three-dimensional higher order bouodary element method (HOBEM) in the time domain. Within the frame of potential flow and the adoption of simply Rankine source, the resulting boundary integral equation is repeatedly solved at each time step and the fully nonlinear free surface boundary conditions are integrated with time to update its position and boundary values. A smooth technique is also adopted in order to eliminate the possible saw-tooth numerical instabilities. The incident wave at the uptank is given as theoretical wave in this paper. The outgoing waves are absorbed inside a damping zone by spatially varying artificial damping on the free surface at the wave tank end. The numerical results show that the NWT developed by these approaches has a high accuracy and good numerical stability. 相似文献
892.
Active Absorption Wave Maker System for Irregular Waves 总被引:2,自引:0,他引:2
1 .IntroductionThephysicalmodeltestisoneofthemainmethodstostudyvariousproblemsassociatedwiththedesignofcoastalstructures .Thecommonlyusedwavemakeristhepiston typewavemaker .Becausethewavemakerishighlyreflective ,akeyproblemisthewavemultiplereflectionsbetweenthewavemakerandthetestedstructuresinthewaveflume .There reflectedwavesfromthewavemakerarespuriouswavesrelativetotheincidentwavestothestructures .Howtopreventthere reflectedwavesfromthewavemakerbecomesacriticalproblemforaccurateexperimental… 相似文献
893.
An Improved Nearshore Wave Breaking Model Based on the Fully Nonlinear Boussinesq Equations 总被引:1,自引:2,他引:1
This paper aims to propose an improved numerical model for wave breaking in the nearshore region based on the fully nonlinear form of Boussinesq equations. The model uses the k equation turbulence scheme to determine the eddy viscosity in the Boussinesq equations. To calculate the turbulence production term in the equation, a new formula is derived based on the concept of surface roller. By use of this formula, the turbulence production in the one-equation turbulence scheme is directly related to the difference between the water portide velocity and the wave celerity. The model is verified by Hansen and Svendsen‘s experimental data (1979) in terms of wave height and setup and sctdown. The comparison between the model and experimental results of wave height and setup and setdown shows satisfactory agreement. The modeled turbulence energy decreases as waves attenuate in the surf zone. The modeled production term peaks at the breaking point and decreases as waves propagate shoreward. It is also suggested that both convection and diffusion play their important roles in the transport of turbulence energy immediately after wave breaking. When waves approach to the shoreline, the production and dissipation of turbulence energy are almost balanced. By use of the slot technique for the simulation of the movable shoreline boundary, wave ranup in the swash zone is well simulated by the present model. 相似文献
894.
Summary The concept of comet orbit activity sphere as introduced byD'Alembert and developed byLaplace is modified and applied to the Sun-Earth-Moon system, leading to a new approximate relationship between astronomical constants usually regarded as independent quantities. When Sun-Earth mass ratio, the astronomic unit, and Earth-Moon separation distance are taken as known, an elementary algebraic formula gives the Earth-Moon mass ratio in terms of these. Despite the inherently imprecise character of this type of calculation, surprisingly close numerical agreement with independently determined values is obtained. The great simplicity and directness of the result contrast with ardous orthodox inference procedures for the lunar mass, suggesting that newer methods of general dynamic analysis are required in the study of asymptotic states of the three-body problem. 相似文献
895.
Three Dimensional Baroclinic Numerical Model for Simulating Fresh and Salt Water Mixing in the Yangtze Estuary 总被引:1,自引:5,他引:1
For simulating fresh and salt water mixing in estuaries, a three dimensional nonlinear baroclinic numerical model is developed, in which the gradients of horizontal pressure contain the gradient of barotropic pressure arising from the gradi-ent of tidal level and the gradient of baroclinic pressure due to the gradient of salinity. The Eulerian-Lagrangian method is employed to descretize both the momentum equations of tidal motion and the equation of salt water diffusion so as to im-prove the computational stability and accuracy. The methods to provide the boundary conditions and the initial conditions are proposed, and the criterion for computational stability of the salinity fields is presented. The present model is used for modeling fresh and salt water mixing in the Yangtze Estuary. Computations show that the salinity distribution has the characteristics of partial mixing pattern, and that the present model is suitable for simulalion of fresh and salt waler mixing in ihe Yanglze Esluary. 相似文献
896.
897.
The element stiffness matrix of the equivalent beam or pipe element of the deformed leg of the platform is derived by the finite element method. The stresses and displacements of some damaged components are calculated, and the numeri-cal solutions agree well with those obtained by the fine mesh finite element method. Finally, as an application of this method, the stresses of some platform structures are calculated and analyzed. 相似文献
898.
Effect of Sample Disturbance on Unconfined Compression Strength of Natural Marine Clays 总被引:7,自引:0,他引:7
1 .IntroductionCoastalstructuresoftenencountersettlementandstabilityproblemsofsoftmarinefoundation (Liuetal.,1 999;Zhouetal.,2 0 0 0 ;Liuetal.,2 0 0 3) .Manyresearchershaveillustratedthatnaturalmarineclaysaregenerallysubjectedtotheeffectsofsoilstructureduringtheirdepositionalandpost depositionalprocesses (Zhangetal.,1 995;Hongetal.,2 0 0 3a ;2 0 0 3b) .Thesoilstructureofnat uralmarineclaysiseasilydamagedduringsamplingandhandlingbecausenaturalmarineclaysgeneral lyhavehighwatercontentandlowsti… 相似文献
899.
Physical Investigation of Directional Wave Focusing and Breaking Waves in Wave Basin 总被引:3,自引:1,他引:3
An experimental scheme for the generation of directional focusing waves in a wave basin is established in this paper. The effects of the directional range, frequency width and center frequency on the wave focusing are studied. The distrihution of maximum amplitude and the evolution of time series and spectra during wave packet propagation and the variation of water surface parameters are extensively investigated. The results reveal that the characteristics of focusing waves are significantly influenced hy wave directionality and that that breaking criteria for directional waves are distinctly different from those for unidirectional waves. 相似文献
900.
Extensive oedometer tests and physical tests have been conducted on remoldod and reconstituted marine soils with different initial water contents and liquid limits. The oedometer test data can be well fitted with a straight line in the bilogarithmin In(1 e)∽lg p plot. The initial effective stress corresponding to the initial void ratio is determined by extrapolation of the bilogarithmic compression line. This new way of extrapolating oedometer test data to the initial void ratio overcomes the difficulty of measuring the residual effective stress of soils in the remolded state. The initial stable compression line of ocean floor deposits under different deposition environments corresponds to the compression line at the sensitivity equal to one. This initial stable compression line obtained in this study is consistent with the available compression line at the sensitivity equal to one which is proposed based on the experimental data of remolded undrained strength and the theoretical concept of Cam-clay critical state line. 相似文献