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21.
In this paper we have made an attempt to define hierarchy of distribution functions for the simultaneous velocity and magnetic fields. Various properties of the constructed functions such as reduction property, separation property, coincidence properties have been discussed, and equations for the evaluation of one- and two-point bivariate distribution functions have been derived. 相似文献
22.
Dewashish Upadhyay Kamal Lochan Pruseth 《Contributions to Mineralogy and Petrology》2012,164(2):303-316
Primary igneous monazite from the Polokongka La granite of the Tso Morari complex in the western Himalayas has been partially replaced by a three-layered corona of metamorphic fluor-apatite, allanite + U- and Th-bearing phases (huttonite + brabantite), and epidote. The alteration is related to high-pressure amphibolite-facies (10–11 kbar and 587–695 °C) fluid-induced retrogression of the ultra-high-pressure granite during exhumation after India–Asia collision. The corona textures can be explained by pseudomorphic partial replacement of the original monazite to apatite and allanite via a fluid-mediated coupled dissolution–reprecipitation process. Mass balance calculations using the volume proportions and compositions of coronal minerals show that the REE, U, Th, Pb, Ba and P were conserved and not transported outside the alteration corona. The formation of fluor-apatite, allanite, huttonite and coffinite from monazite and the immobility of REE, U and Th require an influx of alkali- and F-bearing, Ca-rich fluid having high Ca/Na into the corona. We are aware of only two other occurrences of such alteration textures, and these have several similarities in terms of geodynamic setting and P–T histories of the host rocks. We suggest that there may be a common mechanism of exhumation style, and source and composition of fluids during retrogression of granitoid rocks in collisional orogens and that such breakdown textures can be used to identify metagranites that have experienced high-P metamorphism in continental collision zones, which is otherwise difficult to constrain due to the high variance of the mineral assemblages in these rocks. 相似文献
23.
Precambrian iron ores of the Singhbhum-North Orissa region occur in eastern India as part of the Iron Ore Group (IOG) within the broad horse-shoe shaped synclinorium. More than 50% of Indian iron ore reserves occur in this region. Massive-hard, flaky-friable, blue dust and lateritic varieties of iron ores are the major ore types, associated with banded hematite, jasper and shales. These ores could have formed as a result of supergene enrichment through gradual but extensive removal of silica, alumina and phosphorus from banded iron formations and ferruginous shale. Attempts for optimal utilization of these resources led to various ore characterization studies using chemical analysis, ore and mineral petrography, XRD analysis, SEM and electron probe micro analysis (EPMA). The ore chemistry indicates that the massive hard ores and blue dust have high iron, low alumina and phosphorus contents. Because of high quality, these ores do not require any specialized beneficiation technique for up-gradation. However, flaky-friable, lateritised and goethitic ores are low in iron, high in alumina and phosphorus contents, requiring specific beneficiation techniques for up-gradation in quality. XRD, SEM and ore microscopic studies of massive hard ores indicate the presence of hematite and goethite, while flaky and lateritic ores show a higher concentration of goethite, kaolinite, gibbsite and hematite. EPMA studies show the presence of adsorbed phosphorous as fine dust in the hard ores. Sink and float studies reveal that most of the gangue minerals are not completely liberated in the case of goethitic and lateritic ores, even at finer fractions. 相似文献
24.
We report the discovery of Early Permian (late Asselian, ∼280–275 Ma) plant fossils and associated palynomorphs from a marine sedimentary sequence of the eastern Karakoram plate, in northern India. These specimens show affinities with those found in marine Lower Gondwana sediments of the Indian subcontinent. This supports the contention that during the Early Permian Period, the Karakoram plate was Peri-Gondwanan. It is suggested to have had an intermediate position between the Indian plate and the Qiangtang–Lhasa microcontinents, at a latitude of about 35° south. 相似文献
25.
R. K. Upadhyay S. Asokan A. S. Venkatesh 《Journal of the Geological Society of India》2011,77(6):549-556
The eastern limb of horse shoe shaped “Bonai Synclinorium” in India hosts Banded Iron Formations (BIFs), consisting of major
high grade iron deposits. Phosphorus (P) gets adsorbed in the iron ore by way of ion exchange mechanism of clay minerals and
hydrated secondary iron oxide minerals. Its concentration is lesser in hard ores and blue dust types of ores, while the highest
in case of lateritic ores. P content reduces with increase in iron (Fe) content in individual ore types. Along the eastern
limb, phosphorus content gradually reduces from north to south direction. Since phosphorus is mainly associated with secondary
lateritization process, its concentration is very high in top weathered profile and along the weaker zones. 相似文献
26.
B. Nayak A. K. Singh A. K. Upadhyay K. K. Bhattacharyya 《Journal of the Geological Society of India》2009,74(3):395-401
Lower Gondwana coal from Garu-Gensi area in the West Siang district of Arunachal Pradesh in the Eastern Himalayas have been
characterized with respect to their maceral constituents, mineral matter, ash composition, sulphurand trace-element contents.
These are low-rank bituminous coals (V0 = 0.64) and their vitrinite content is about 60%. A first hand data with respect to twenty one trace-elements are reported.
Our data indicate that these Lower Gondwana coals of extra-peninsular region are richer in terms of their trace-element content
when compared with their counter parts of peninsular India. 相似文献
27.
The plasma waves in the Venus ionosphere measured by OEFD aboard PVO are analysed. It is shown that these waves are generated
by lightning like cloud-to-cloud discharges anywhere in the Venus ionosphere-surface waveguide. The theoretical minimum attenuation
for waveguide mode propagation at 5.4 kHz is consistent with the maximum occurrence rate at this frequency. The lightning-generated
and globally-propagating signals when encountered with plasma holes or ion-trough structures escape out partially and are
detected by the OEFD aboard PVO. The 100 Hz signals can propagate upwards in whistler mode. Even the localized electrostatic
mode waves would be converted into electromagnetic waves in the plasma holes and ion-trough regions. 相似文献
28.
D. Upadhyay M. M. Raith K. Mezger A. Bhattacharya P. D. Kinny 《Contributions to Mineralogy and Petrology》2006,151(4):434-456
The suture zone between the Bhandara craton and the granulite-facies rocks of the Eastern Ghats Province in SE India contains a number of deformed alkaline and tholeiitic intrusives. The Khariar alkaline complex is one of the several occurrences which intruded in the Mesoproterozoic (1,480±17 Ma, 2σ) and was deformed during the Pan-African tectonothermal event. The geochemical signatures indicate a rift-related setting for the magmatic activity. The nepheline syenite parent magma may have been produced by in-mantle fractionation of clinopyroxene and Ti-rich amphibole from a basanitic primary magma derived from an enriched spinel lherzolite mantle source in the sub-continental lithosphere. Geochemical variations in the Khariar alkaline suite can be modeled by the fractionation of clinopyroxene, amphibole, titanite, zircon, apatite and allanite. The Mesoproterozoic alkaline magmatism at Khariar marks the initiation of a NE-SW rift which formed several craton margin basins and opened an ocean towards the south. The sediments of the cratogenic basins and the Eastern Ghats Province were deposited in these rift-related basins. A K-Ar age of 1,330±53 Ma from glauconites in sandstone suggests that the NW-SE trending Godavari–Pranhita graben formed at approximately the same time as the rift at the craton margin. If the two are related, the Godavari–Pranhita graben may represent the failed arm of a rift system in which the NE-SW arm was the active segment. The granulite-facies deformation and metamorphism of the Eastern Ghats Province sediments may be related to an episode of Grenvillian basin inversion. The Mesoproterozoic rifting and Grenvillian basin closure may thus represent two well-defined parts of a Wilson cycle i.e. the opening and closure of an ocean. The Khariar and other alkaline bodies were, however, deformed during a Pan-African collisional event associated with the westward thrusting of the Eastern Ghats Province granulites over the cratonic foreland. 相似文献
29.
A. K. Upadhyay K. K. Gupta J. K. Sircar M. K. Deb G. L. Mundhara 《Environmental Geology》2007,51(8):1447-1453
The importance of study of heavy metal distribution in river sediments is a component in understanding the exogenic cycling
as well as in assessing the effect of anthropogenic influences of the elements. In India, the river Subernarekha flows over
Precambrian terrain of Singhbhum craton in the eastern India. The geological succession in this part of India is through (1)
iron ore series, (2) ultrabasic igneous rocks, (3) diorite, (4) granite, (5) newer dolerites, (6) newer tertiary and (7) alluvium.
The first four groups belong to the Archaean era, and the representative is the iron ore series consisting of iron ore, manganese
and chromite which are abundantly present. The primary rock types are schist and quartzite layers. One main tributary, the
Kharkhai flow through granite and schist and quartzite layers. Two important creeks are Gurma and Garra, respectively. The
former after originating in basic igneous area travels through schist quartzite, while the later one originates in granite
area where some functional but old gold mines are located. Freshly deposited sediments of river were collected upstream and
downstream the industrial zone (East Singhbhum district). Samples were collected from four locations and analysed in <63 μm
sediment fraction for heavy metals like Ni, Co and Cr by adsorption stripping voltammetry on hanging mercury drop electrode
and Hg by anodic stripping voltammetry using polished rotating gold disk electrode. Enrichment of these metals over and above
the local natural concentration level (NCL) has been calculated and applied to determine metal-pollution index (MPI) proposed
by Goncalves et al. and also geo-accumulation index (I
geo) by Muller. Based on Muller’s classification, Ni, Cr and Hg have been classified from unpolluted to moderately polluted range
in pre-monsoon period but for metals Ni and Cr, during the post-monsoon period the values have reached moderately polluted
level while Hg has been classified under unpolluted to moderately polluted level except at the monitoring station situated
upstream to Gurma Creek where it was found at unpolluted level. Presence of natural resources of the minerals is primarily
the reason for their detection in river sediments (lithogenic) but some anthropogenic sources are also contributing for their
presence at some sampling stations. Hg is considered to be chalcophilic in nature and is detected wherever known sulphidic
ores of copper or nickel are present. 相似文献
30.
Joshi L. M. Kotlia B. S. Kothyari G. Ch. Singh A. K. K. Taloor A. Upadhyay R. Dayal D. 《Geotectonics》2021,55(4):543-562
Geotectonics - The present study focuses on the neotectonics activity and related mass movement along the Eastern Ramganga River Basin (ERRB), Kumaun Himalaya, India. To understand the... 相似文献