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121.
Coastal cliffs and shore platforms are important geomorphic features of coastal areas of Saurashtra. These features are composed
of medium to coarse grained carbonate sand and are designated as “Miliolitic limestones” that range in age from Middle to
Late Pleistocene. Significant jointing has been observed in the Middle Pleistocene Miliolite Formation as well as in the younger
shell limestone that comprises Chaya Formation of Late Pleistocene. Along with NE-SW trend which is the direction of maximum
horizontal compressive stress [SHmax] for Indian sub-continent, other trends recorded are NNE-SSW, N-S, NW-SE and E-W. When compared with other regional studies,
neotectonic episode in Saurashtra peninsula appears to be younger than at least 125ky. The present study on joint sets also
indicates that they are important to understand stresses associated with anticlockwise rotation of the Indian plate. 相似文献
122.
In this study we investigated the effects of external trigger on the characteristics of young stellar objects (YSOs) associated with cometary globules (CGs). We made optical spectroscopy of stars associated with star-forming CGs. We find that the masses of the most massive stars associated with CGs are correlated with the masses of the parent cloud but they are systematically larger than expected for clouds of similar mass from the relation M max-star=0.33M cl 0.43 given by Larson (Mon. Not. R. Astron. Soc. 200:159, 1982). We have also estimated the luminosities of the IRAS sources found associated with CGs as a function of cloud mass and then compared them with those of the IRAS sources found associated with isolated opacity class 6 clouds (isolated and relatively away from large star forming regions). We find that the luminosities of IRAS sources associated with CGs are larger than those of the opacity class 6 clouds. These findings support results from recent simulations in which it was shown that the Radiation Driven Implosion (RDI) process, believed to be responsible for the cometary morphology and star formation, can increase the luminosity 1–2 orders of magnitudes higher than those of protostars formed without external triggering due to an increase in accretion rates. Thus implying that the massive stars can have profound influence on the star formation in clouds located in their vicinity. 相似文献
123.
Satish J. Patel Jaquilin K. Joseph Nishith Y. Bhatt 《Journal of the Geological Society of India》2014,84(2):129-154
The middle Jurassic Goradongar Formation exposed in Goradongar hill represents a mixed siliciclasticcarbonate succession with shales and limestones. They contain a large number of well preserved trace fossils. Total 44 ichnospecies of 31 ichnogenera; representing diverse ethology, were grouped in five ichnoassemblages (Planolites, Palaeophycus, Gyrochorte, Rhizocorallium and Arenicolites assemblage). These recurring ichnoassemblages represent the Cruziana ichnofacies and occasionally a mixed Skolithos-Cruziana ichnofacies. Patterns of diversity and density of the trace fossils reveal changes in bathymetry, oxygen level, trophic level and the sub-strate conditions at the time of deposition. These paleoenvironment and palaeo-oceanography changes are co-relatable to world-wide Bathonian-Callovian (middle Jurassic) deposits. 相似文献
124.
Manish A. Mamtani V. Abhijith Sivaji Lahiri Virendra Rana Sandeep Bhatt Shalini Goswami A. R. Renjith 《Journal of the Geological Society of India》2017,89(1):5-11
Salem-Attur shear zone in the Southern Granulite Terrane demarcates the tectonic boundary between Archaean granulites of Dharwar craton and the Palaeoproterozoic granulites of Salem area. The shear zone marks a low angle thrust which has been steepened at places due to late stage folding. Static recrystallisation during late stage folding has removed the strain marker of mylonites to large extent. However, in a few places S-C angle and porphyroclasts are preserved and have been used to compute the strain. The strain shows apparent flattening by simple shear deformation with 35 % volume loss. A minimum displacement along the thrust has been computed to be 2.7 km. The strain k values increases with r suggesting the strain approaching towards prolate field with increase in strain intensity. The above study suggests the Salem-Attur shear zone is a thrust with low to moderate deformation and volume loss. 相似文献