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61.
The influence of El Nio-Southern Oscillation (ENSO) on the convectively coupled Kelvin waves over the tropical Pacific is investigated by comparing the Kelvin wave activity in the eastern Pacific (EP) El Nio, central Pacific (CP) El Nio, and La Nia years, respectively, to 30-yr (1982-2011) mean statistics. The convectively coupled Kelvin waves in this study are represented by the two leading modes of empirical orthogonal function (EOF) of 2-25-day band-pass filtered daily outgoing longwave radiation (OLR), with the estimated zonal wavenumber of 3 or 4, period of 8 days, and eastward propagating speed of 17 ms-1 . The most significant impact of ENSO on the Kelvin wave activity is the intensification of the Kelvin waves during the EP El Nios. The impact of La Nia on the reduction of the Kelvin wave intensity is relatively weaker, reflecting the nonlinearity of tropical deep convection and the associated Kelvin waves in response to ENSO sea surface temperature (SST) anomalies. The impact of the CP El Nio on the Kelvin waves is less significant due to relatively weaker SST anomalies and smaller spatial coverage. ENSO may also alter the frequency, wavelength, and phase speed of the Kelvin waves. This study demonstrates that low-frequency ENSO SST anomalies modulate high-frequency tropical disturbances, an example of weather-climate linkage. 相似文献
62.
O. S. R. U. BHANU KUMAR 《水文科学杂志》2013,58(5):515-525
Abstract This paper presents the relationship between Indian summer monsoon total rainfall and two parameters from Eurasian snow cover, one being the winter snow cover extent and the other the area of spring snowmelt. Satellite-derived Eurasian snow cover extent and Indian monsoon rainfall data were obtained from the NOAA/NESDIS and the India Meteorological Department (IMD) for the period 1966–1985. Seasonal cyclic variations of snow cover showed a higher swing in both the winter and the spring seasons of the cycle as compared to the remaining seasons of the year in the lower region of the cycle. The established inverse relation between winter snow cover and monsoon rainfall during June to September is further extended. Winter snow cover is very strongly correlated with spring snowmelt over Eurasia. Spring snowmelt area is obtained by subtracting the May snow cover extent from that of the previous February. The variations of spring snowmelt were also compared with Indian total monsoon rainfall. The detected correlation is stronger between snowmelt and monsoon rainfall than between the winter snow cover and the monsoon rainfall. There is also a significant multiple correlation among winter snow cover, spring snowmelt and monsoon rainfall. Lastly, a significant multiple correlation suggested a multiple regression equation which might improve the climatic prediction of monsoon rainfall over India. 相似文献
63.
This paper presents an efficient algorithm, FDA2DMT (Free Decay Analysis for 2D Magnetotellurics (MT)), based on eigenmode
approach to solve the relevant partial differential equation, for forward computation of two-dimensional (2D) responses. The
main advantage of this approach lies in the fact that only a small subset of eigenvalues and corresponding eigenvectors are
required for satisfactory results. This small subset (pre-specified number) of eigenmodes are obtained using shift and invert
implementation of Implicitly Restarted Lanczos Method (IRLM). It has been established by experimentation that only 15–20%
smallest eigenvalue and corresponding eigenvectors are sufficient to secure the acceptable accuracy. Once the single frequency
response is computed using eigenmode approach, the responses for subsequent frequencies can be obtained in negligible time.
Experiment design results for validation of FDA2DMT are presented by considering two synthetic models from COMMEMI report,
Brewitt-Taylor and Weaver (1976) model and a field data based model from Garhwal Himalaya. 相似文献
64.
R T RATHEESH KUMAR TANMAY K MAJI SURESH CH KANDPAL D SENGUPTA RAJESH R NAIR 《Journal of Earth System Science》2011,120(3):447-458
Global estimates of the elastic thickness (Te) of the structure of passive continental margins show wide and varying results
owing to the use of different methodologies. Earlier estimates of the elastic thickness of the North Atlantic passive continental
margins that used flexural modelling yielded a Te value of ~20–100 km. Here, we compare these estimates with the Te value
obtained using orthonormalized Hermite multitaper recovered isostatic coherence functions. We discuss how Te is correlated
with heat flow distribution and depth of necking. The E–W segment in the southern study region comprising Nova Scotia and
the Southern Grand Banks show low Te values, while the zones comprising the NE–SW zones, viz., Western Greenland, Labrador,
Orphan Basin and the Northern Grand Bank show comparatively high Te values. As expected, Te broadly reflects the depth of
the 200–400°C isotherm below the weak surface sediment layer at the time of loading, and at the margins most of the loading
occurred during rifting. We infer that these low Te measurements indicate Te frozen into the lithosphere. This could be due
to the passive nature of the margin when the loads were emplaced during the continental break-up process at high temperature
gradients. 相似文献
65.
A set of large deformation experiments are presented to simulate folding pattern at various energy states during formation.
In order to numerically simulate this phenomenon, a rectangular layer of shale is generated and compressed at various strain
rates. The results reveal the variation in distribution of stress along the length of the bed. The stress distribution during
elastic behaviour of shale bed at low compression rate and the change in stress distribution leading to rupture at high compression
rates is discussed. Wavelength, limb length, bulk shortening, stress distribution, displacement of particles along the length
of the bed is considered for comparative study of the fold pattern generated at various compression rates. The nature and
position of crack generated during the formation of fold is also explained. After rupture in shale bed, the generation of
fault and stress distribution in limbs of fold sliding over one another is also described. 相似文献
66.
Some analytical solutions of one-dimensional advection–diffusion equation (ADE) with variable dispersion coefficient and velocity are obtained using Green’s function method (GFM). The variability attributes to the heterogeneity of hydro-geological media like river bed or aquifer in more general ways than that in the previous works. Dispersion coefficient is considered temporally dependent, while velocity is considered spatially and temporally dependent. The spatial dependence is considered to be linear and temporal dependence is considered to be of linear, exponential and asymptotic. The spatio-temporal dependence of velocity is considered in three ways. Results of previous works are also derived validating the results of the present work. To use GFM, a moving coordinate transformation is developed through which this ADE is reduced into a form, whose analytical solution is already known. Analytical solutions are obtained for the pollutant’s mass dispersion from an instantaneous point source as well as from a continuous point source in a heterogeneous medium. The effect of such dependence on the mass transport is explained through the illustrations of the analytical solutions. 相似文献
67.
Comments on: 'Petrogenesis of Proterozoic Lamproites and Kimberlites from the Cuddapah Basin and Dharwar Craton, Southern India' 总被引:1,自引:1,他引:0
Kimberlites intrude the late Archaean eastern Dharwar Cratonin two spatially separate fields (150 km apart, near Mahbubnagarin the north and Anantapur in the south) to the west of theProterozoic Cuddapah Basin in southern India. Two lamproitebodies intrude the thick Cuddapah Basin sediments near Chelimaand Zangamarajupalle, and a third occurs just outside the presentNE margin of the basin near Ramannapeta. Chalapathi Rao et al.(2004) have studied this spatially, and possibly temporally,close association of kimberlites and lamproites to provide insightsinto their genesis and genetic relationship. Although the mainemphasis of their paper is the petrochemical characterizationof these two suites of rocks, they also report SrNd isotopedata for a small subset of samples, which they use to provideconstraints on the nature of the mantle source regions. Of some 相似文献
68.
69.
The allowance for the influence of a vertical contact is evaluated on Wenner resistivity sounding curves, which are graphically constructed on bilogarithmic paper over simple composite earth models consisting of a vertical contact separating two- or three layered earth on one side and a homogeneous medium on the other side. The error incurred in the graphical constructions is explored. Finally, the use of these graphically constructed sounding curves is shown in the interpretation of two Wenner field soundings measured in a complex geologic area. 相似文献
70.
Investigating the immobilization of CO2, previous basalt-water-CO2 interaction studies revealed the formation of carbonates over a short period, but with the extensive formation of secondary silicates (SS). The mechanisms involved in these processes remain unresolved, so the present study was undertaken to understand secondary mineral formation mechanisms. XRPD and Rietveld refinement data for neo-formed minerals show a drastic decrease in the Ca-O bond length, with the calcite structure degenerating after 80 h (hours). However, SEM images and EDS data revealed that a longer interaction time resulted in the formation of chlorite and smectite, adjacent to basalt grains which prevent basalt-water-CO2 interaction to form carbonates, thus restricting carbonate formation. As a result of this, the CO2 mineralization rate is initially high (till 80 h), but it later reduces drastically. It is evident that, for such temperature-controlled transformations, low temperature is conducive to minimizing SS surface coating at the time of mineral carbonation. 相似文献