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91.
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1Preface Todescribeoceanicintermediatewatermasses,itis necessarytohaveawell definedstudyframeorsurfacebecauseofthefluctuationnatureofintermediatewa ters.Itiswellunderstoodthatoceanicwater mass mixingdoesnotalignwitheitheraconstantgeopoten tialdepthorapropertysurfacesuchastemperature,salinity,pressureanddensitysurfacesbutfollowsa neutraldensitysurface.Thisisbecauseawaterparcelmovesasmalldistanceisentropicallyandadiabaticallyontheneutraldensitysurfacewithoutdoingworka gainstabuoyantrestoringforc… 相似文献
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《The Australian geographer》1991,22(2):178-184
Significant elements of the Australian landscape date from Mesozoic or earlier times. Australia did not separate completely from other Gondwanan components until Early Tertiary times and these Mesozoic and older elements can therefore be regarded as Gondwanan. During the separation and northern drift of the continent and particularly in Late Jurassic and earlier Cretaceous times the sea invaded and spread across much of the erstwhile landmass. The associated sediments not only covered and preserved much of the pre‐existing land surface, but they also augmented the effects of thalassostatic loading of the basins, causing further subsidence. Hinge lines developed near the coastal zones of the times, so that subsidence of the basins caused adjacent land masses to rise. Many old land surfaces have been re‐exposed at the former oceanic margins, but epigene forms are preserved high in the relief on the uplifted blocks. They survive partly because, as Crickmay (1976) suggested, rivers effectively erode at and near their channels; the divides remain untouched. A reinforcement effect also operates because the valleys are wet sites, the interfluves dry. Hence weathering and erosion proceed apace in the former while the latter are stable, allowing palaeoforms to survive. 相似文献
95.
A differential approach to map comparison and integration is presented utilizing the variance-covariance matrices of polynomial trend surfaces. The approach is based on the statistics presented in the trend-surface computer program, CORSURF. Examples in south-central Kansas and the Maracaibo Basin in Venezuela are presented to show how the technique could be used in basinanalysis studies. 相似文献
96.
Rachel Mundeli Murekatete 《International journal of geographical information science》2018,32(11):2169-2188
Planners who are involved in locational decision-making often use raster-based geographic information systems to quantify the value of land in terms of suitability or cost for a certain use. From a computational point of view, this process can be seen as a transformation of one or more sets of values associated with a grid of cells into another set of such values through a function reflecting one or more criteria. While it is generally anticipated that different transformations lead to different ‘best’ locations, little has been known on how such differences arise (or do not arise). The paper attempts to answer this question in the context of path planning through a series of computational experiments using a number of random landscape grids with a variety of spatial and nonspatial structures. In the experiments, we generated least-cost paths on a number of cost grids transformed from the landscape grids using a variety of transformation parameters and analyzed the locations and (weighted) lengths of those paths. Results show that the same pair of terminal cells may well be connected by different least-cost paths on different cost grids though derived from the same landscape grid and that the variation among those paths is affected by how given values are distributed in the landscape grid as well as by how derived values are distributed in the cost grids. Most significantly, the variation tends to be smaller when the landscape grid contains more distinct patches of cells potentially attracting or distracting cost-saving passage or when the cost grid contains a smaller number of low-cost cells. 相似文献
97.
In this article we treat the 'Extended Sitnikov Problem' where three bodies of equal masses stay always in the Sitnikov configuration.
One of the bodies is confined to a motion perpendicular to the instantaneous plane of motion of the two other bodies (called
the primaries), which are always equally far away from the barycenter of the system (and from the third body). In contrary
to the Sitnikov Problem with one mass less body the primaries are not moving on Keplerian orbits. After a qualitative analysis
of possible motions in the 'Extended Sitnikov Problem' we explore the structure of phase space with the aid of properly chosen
surfaces of section. It turns out that for very small energies H the motion is possible only in small region of phase space and only thin layers of chaos appear in this region of mostly
regular motion. We have chosen the plane (
) as surface of section, where r is the distance between the primaries; we plot the respective points when the three bodies are 'aligned'. The fixed point
which corresponds to the 1 : 2 resonant orbit between the primaries' period and the period of motion of the third mass is
in the middle of the region of motion. For low energies this fixed point is stable, then for an increased value of the energy
splits into an unstable and two stable fixed points. The unstable fixed point splits again for larger energies into a stable
and two unstable ones. For energies close toH = 0 the stable center splits one more time into an unstable and two stable ones. With increasing energy more and more of
the phase space is filled with chaotic orbits with very long intermediate time intervals in between two crossings of the surface
of section. We also checked the rotation numbers for some specific orbits.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Xingong Li Shuhua Zhang Yaning Chen 《International journal of geographical information science》2016,30(10):2032-2049
Two grid-based diffuse solar radiation models, ESRI’s Solar Analyst (SA) and Kumar’s model (KM), were assessed using a data-independent approach where each model’s numerical results of clear sky diffuse radiation on V/U-shaped surfaces were compared with analytical results derived using each model’s assumptions. SA and KM consistently underestimate and overestimate, respectively, diffuse radiation at daily, seasonal, and annual scale relative to the analytical results based on each model’s parameterizations. Overall, SA performs better than KM in modeling diffuse radiation at most timescales. While SA and KM have similar error in calculating diffuse radiation on a horizontal surface, SA models sky view factor much better than KM, with mean absolute relative differences of 0.76% and 17.02%, respectively. KM has a large error in sky view factor as it does not consider the shading effect from surrounding terrain. Sky view factor error in SA is small and use of more zenith divisions can further reduce the error. Based on our previous study, model performance on clear sky global solar radiation was also evaluated. Overall, KM performs better than SA in global radiation as KM performs better than SA in modeling direct radiation which is the major component of global radiation. 相似文献
100.