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841.
An apparatus is described which provides for the investigation of viscoelasticity/anelasticity in geologic and related materials under conditions of high pressure and temperature. Cylindrical specimens are tested in torsion—a geometry particularly well suited to shear mode observations at the low strain amplitudes of the linear regine. Forced oscillation experiments allow the measurement of disperision and attenuation at the low frequencies of teleseismic wave propagation. The conduct of complementary forced oscillation and creep tests allows recoverble anelastic strains to be distinguished from those of permanent viscous deformation. It has been demonstrated that robust measurements can be made at strain amplitudes below 10–5 and frequencies of 1 mHz–1 Hz, underP-T conditions to 300 MPa and 1200°C. The prospects for further development of this facility are outlined. 相似文献
842.
843.
844.
波浪非线性弥散关系及其应用 总被引:3,自引:0,他引:3
针对Hedges及Kirby等对Kirby和Dahymple的非线性弥散关系的修正关系,在小波陡时中等水深范围存在较大偏差的问题,给出了一个新的非线性弥散关系。比较可知,新的关系在小波陡时减小了中等水深范围内50%的误差,而在大波陡时能够保持其单调性,且形式上更为简练。将其应用于含弱非线性效应的缓坡方程进行数值验证,结果表明,采用新的非线性弥散关系得到的计算结果与实测结果更为吻合。 相似文献
845.
利用地形地貌资料确定Nash模型参数的研究 总被引:8,自引:0,他引:8
基于近代关于流域汇流机理是地貌和水动力扩散作用的新观点,导出了根据霍顿(Horton)地貌参数计算n和根据地形资料计算K的公式,并用实例作了检验。本文将有助于深化无资料情况下汇流计算方法的研究。 相似文献
846.
浅论油气藏的逸散史与油气化探异常模式 总被引:3,自引:0,他引:3
根据不同油气藏上方的异常发育特征.指出了各类异常模式差异的原因可能是油气藏逸散阶段不同的结果,分析了油气藏不同逸散阶段各指标异常的变化特征,建立了不同逸散阶段的理想异常模式。 相似文献
847.
Footprint Analysis: A Closed Analytical Solution Based On Height-Dependent Profiles Of Wind Speed And Eddy Viscosity 总被引:5,自引:0,他引:5
Based on the theoretical background of existing models for the crosswind-integrated footprint, a new model is presented, which, in contrast to the existing models, describes the normalized footprint by a closed analytical formula. This was made possible by using well-known power profiles for wind speed and eddy viscosity instead of Monin–Obukhov based profiles at a certain stage of model development. However, the major difference between the new model and the existing models is that the so-called shape parameter of vertical plume dispersion, a function of upwind distance in the existing models, is set constant in the new model in order to circumvent a formal inconsistency found in the derivation of the existing models. Due to this inconsistency, the existing models do not generally satisfy the fundamental condition that the cumulative normalized footprint must approach unity for the upwind distance tending towards infinity. 相似文献
848.
Modelling adsorptive solute transport in soils needs a number of parameters to describe its reaction kinetics and the values of these parameters are usually determined from batch and displacement experiments. Some experimental results reveal that when describing the adsorption as first-order kinetics, its associated reaction rates are not constants but vary with pore water velocity. Explanation of this varies but an independent verification of each explanation is difficult because simultaneously measuring the spatiotemporal distributions of dissolved and adsorbed solutes in soils is formidable. Pore-scale modelling could play an important role to address this gap and has received increased attention over the past few years. This paper investigated the transport of adsorptive solute in a simple porous medium using pore-scale modelling. Fluid flow through the void space of the medium was assumed to be laminar and in saturated condition, and solute transport consisted of advection and molecular diffusion; the sorption and desorption occurring at the fluid–solid interface were modelled as linear first-order kinetics. Based on the simulated spatiotemporal distribution of dissolved and adsorbed solutes at pore scale, volumetric-average reaction kinetics at macroscopic scale and its associated reactive parameters were measured. Both homogeneous adsorption where the reaction rates at microscopic scale are constant, and heterogeneous adsorption where the reaction rates vary from site to site, were investigated. The results indicate that, in contrast to previously thought, the macroscopic reaction rates directly measured from the pore-scale simulations do not change with pore velocity under both homogeneous and heterogeneous adsorptions. In particular, we found that for the homogeneous adsorption, the macroscopic adsorption remains first-order kinetic and can be described by constant reaction rates, regardless of flow rate; whilst for the heterogeneous adsorption, the macroscopic adsorption kinetics continues not to be affected by flow rate but is no longer first-order kinetics that can be described by constant reaction rates. We discuss how these findings could help explain some contrary literature reports over the dependence of reaction rates on pore water velocity. 相似文献
849.
850.
Non-stationary spatial covariance structure estimation in oversampled domains by cluster differences scaling with spatial constraints 总被引:2,自引:2,他引:0
J. F. Vera R. Macías J. M. Angulo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(1):95-106
In the analysis of spatiotemporal processes underlying environmental studies, the estimation of the non-stationary spatial
covariance structure is a well known issue in which multidimensional scaling (MDS) provides an important methodological approach
(Sampson and Guttorp in J Am Stat Assoc 87:108–119, 1992). It is also well known that approximating dispersion by a non-metric
MDS procedure offers, in general, low precision when accurate differences in spatial dispersion are needed for interpolation
purposes, specially if a low dimensional configuration is employed besides a high number of stations in oversampled domains.
This paper presents a modification, consisting of including geographical spatial constraints, of Heiser and Groenen’s (Psychometrika
62:63–83, 1997) cluster differences scaling algorithm by which not the original stations but the cluster centres can be represented,
while the stations and clusters retain their spatial relationships. A decomposition of the sum of squared dissimilarities
into contributions from several sources of variation can be employed for an exploratory diagnosis of the model. Real data
are analyzed and differences between several cluster-MDS strategies are discussed. 相似文献