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231.
M. S. Sisodia A. D. Shukla K. M. Suthar R. R. Mahajan S. V. S. Murty P. N. Shukla N. Bhandari R. Natarajan 《Meteoritics & planetary science》2001,36(11):1457-1466
Abstract— The Lohawat meteorite is a texturally heterogeneous breccia having a variety of mineral and lithic fragments. Among mineral fragments, pyroxenes show a wide range of composition (Wo0.011–0.17En0.37–0.78Fs0.21–0.60) whereas plagioclase is anorthitic (An0.92Ab0.07Or0.007). Abundant rounded “chondrule‐like” objects ranging in size up to ~7 mm, some with concentric layering, have been observed. Petrographic features, trace element composition and rare earth element patterns show the presence of eucritic and diogenitic components confirming that it is a typical howardite. Cosmogenic tracks, rare gases (He, Ne, and Ar) and radionuclides (22Na and 26Al) were measured. Track density in olivine and plagioclase varies between 0.7 to 6 times 106/cm2. 38Ar exposure age is estimated to be ~110 Ma, being the highest among howardites. The track production rates correspond to ablation of 9 to 15 cm, implying a radius for its preatmospheric size of ~27 cm. 22Na/26Al ~ 1, as expected from the production models and solar modulation of galactic cosmic‐ray fluxes before its fall, suggesting that the meteoroid did not undergo any fragmentation during the past ~2 Ma in interplanetary space. The radiogenic age based on K‐Ar method is 4.3 Ga while the U‐Th‐4He age is 3.3 Ga indicating partial loss of He. 相似文献
232.
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235.
A. S. N. Murty H. C. Tewari Prakash Kumar P. R. Reddy 《Pure and Applied Geophysics》2005,162(12):2409-2431
A 2-D subcrustal velocity model for the central Indian continental lithosphere has been derived by travel time and relative
amplitude modeling of a digitally normalized analog seismic record section of the Hirapur-Mandla DSS profile, using a ray-tracing
technique. Some prominent wave groups with apparent velocities slightly higher than the Moho reflection phase (PMP) are identified on the normalized record sections assembled with a reduction velocity of 6 km s−1. We interpret these phases as the wide-angle reflections from subcrustal lithospheric boundaries. Comparison of synthetic
seismograms with the observed record section shows that the observed phases cannot be explained either by multiples or by
the P-to-S converted phase (PMS) from the Moho. Subcrustal velocity models either with a velocity increase or with a single low velocity layer (LVL) also
do not provide a satisfactory fit. We infer that a subcrustal velocity model with two alternate LVLs (velocity 7.2 km s−1), separated by a 6-km thick high velocity layer (velocity 8.1 km s−1), can satisfy both the observed travel times and amplitudes. The prominent reflection phases are modeled at depths of 49,
51, 57 and 60 km. It is inferred that the subcrustal lithosphere in the central Indian region has a lamellar structure with
varying structural and mechanical properties. The alternating LVLs, occurring at relatively shallow depths below Moho, may
be associated with the zones of weakness and lower viscosity suggesting continued mobility, with a possible thermal source
in the upper mantle. This explains the source of observed high heat flow values in the central Indian region. 相似文献
236.
High resolution aicraft observations of temperature were made in cloud-air and clear-air at different heights in the lower atmosphere over the Deccan Plateu, India, during the summer monsoon season (June–September) of 1976. Temperature fluctuations in the horizontal at each flight level were utilised for computing the temperature structure parameter (C
T
2
) at that level for studying the hieght dependence ofC
T
2
. The results were found to be in agreement with those obtained by other investigators. Also, the height variations ofC
T
2
in cloud-air and clear-air during active and weak monsoon conditions are studied. Marked differences were noticed in the behaviour ofC
T
2
during active and weak monsoon conditions. 相似文献
237.
Summary The values of evaporation for several months from the sea at Waltair, are computed from climatic means of observations made at a near-shore station at Waltair. The simplified equation of evaporation
, has been used in the computations. 相似文献
238.
G. S. Murty 《Pure and Applied Geophysics》1971,90(1):96-108
Summary An infinite cylinder with a small ridge on the surface parallel to the axis is assumed to be excited by an embedded periodic line source radiating compressional waves. The line source is also assumed to lie parallel to the axis, and the frequency of radiation is small enough so that the corresponding wavelength is large compared to the dimension of the ridge on the surface of the cylinder. Considering the effect of the ridge as a small perturbation, the wave equations are solved and the amplitudes of the potential fields are expressed in terms of a set of inhomogeneous algebraic equations in which the solution of the problem without the ridge supplies the source term for the first order perturbation in potential fields. 相似文献
239.
Summary Studies upon the changes of bottom topography in the vicinity of Godavari point and Kakinada Bay indicates recession of contours towards the shore as a result of net loss of sediment since the formation of Kakinada Bay. The sand spit has been growing in the north-westerly direction reducing the width of the opening between the Kakinada Bay and the open Ocean. The currents across the opening strengthen resulting rapid erosion of the bottom of the Bay. The beach to the north of the Kakinada Bay entrance channel is building up. In the present investigation, the authors made an attempt to explain the shore line changes and changes in bottom topography in the Kakinada Bay from the currents measured under different tidal conditions around the sand spit (Godavari Point.) 相似文献