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11.
Sk. Md. Equeenuddin S. Tripathy P. K. Sahoo M. K. Panigrahi 《Environmental Earth Sciences》2010,60(4):723-731
The deposition of ochreous is common by a consequence of acid mine drainage (AMD). The ochreous precipitated from the AMD
sites around Tertiary coalfield of Assam, India were collected and characterized by X-ray diffractometry (XRD), Fe to S molar
ratio, ammonium oxalate acid (pH 3.0) extraction, fourier-transform infrared spectroscopy (FTIR), field emission scanning
electron microscopy (FESEM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The ochreous mainly
consists of goethite, schwertmannite, ferrihydrite and jarosite. Mineralogy of ochreous was controlled by the pH whereas formation
of ferrihydrite was favored at high organic carbon content. Role of bacteria for the formation of secondary minerals was observed.
Mobility of metals was controlled by the ochreous, and they were also retained during the process of phase transformation
of poorly ordered iron-oxyhydroxysulfates into the stable forms. 相似文献
12.
M K Panigrahi A Mookherjee G V C Pantulu K Gopalan 《Journal of Earth System Science》1993,102(2):399-413
On the basis of field relations, petrography and chemistry, three types of granitoids are recognized at Malanjkhand in and
around the copper deposit over an area of about 200 km2. These are (i) a fine grained ‘leucogranite’ of restricted occurrence in the surrounding area (Gr-I); (ii) coarse-grained,
grey in most parts, gneissose granitoid of regional extension (Gr-II); and (iii) the pink-feldspar bearing massive type hosting
the mineralization with occasional representatives in the surrounding country (Gr-III). Gr-I comes out as a distinct entity
on the basis of cross-cutting relation and mineralogical and chemical composition, the Rb-Sr whole rock isochron also giving
a younger age than the other two groups irrespective of the regression model used. Gr-II comes out as the oldest unit but
its age relationship with Gr-III cannot be established unequivocally. An uncorrelated error regression model establishes the
age relationship as Gr-I<Gr-III<Gr-II, whereas a two-error regression model establishes temporal closeness between Gr-II and
III.
The term ‘granitoids’ is being used broadly to include rocks ranging in composition from alkali-granite to tonalite. 相似文献
13.
Mruganka K. Panigrahi Brendan R. Bream Kula C. Misra Rajesh K. Naik 《Mineralium Deposita》2004,39(5-6):670-677
The Malanjkhand copper–molybdenum deposit in the Bhandara Craton, Central India, is hosted by a granite complex which consists of regionally dominant grey granitoid and pink granitoid confined to the mineralized zone. New SHRIMP RG data on zircons from both granite types are inferred to have crystallized during the same magmatic pulse at ca 2.48 Ga. The discrepancy between zircon age and earlier obtained Rb–Sr whole-rock age is attributed to modification of the Rb–Sr system by hydrothermal overprint. Similarity in petrographic features and chemical affinity in combination with identical age strongly indicate that the pink granite is the hydrothermally altered variety (microclinization and silicification) of the grey granite. The spatially associated, main Cu–Mo mineralization event at Malankhand appears to be broadly contemporaneous with and genetically related to the emplacement of the host granitoids at about 2.48 Ga. 相似文献
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J. Swain R. K. Shukla A. Raghunadha Rao J. K. Panigrahi N. R. Venkitachalam 《Journal of Earth System Science》2003,112(2):255-266
Time-series wind and wave measurements were carried out onboard INS Sagardhwani in the central Bay of Bengal during BOBMEX-99.
Various other marine meteorological and oceanographic measurements relevant to monsoon studies were also collected simultaneously.
The observed variations of wind and waves and the associated mixed layer depth (MLD) variability based on both temperature
and density criteria at 3 hourly intervals are presented in this paper as a case study. At the time-series location (13‡N,
87‡E) wind varied between 6 and 16m/s and the predominant direction was southwesterly. The significant wave height and period
varied from 1.9 to 3.7m and 8 to 13 s respectively. Some of the available statistical predictive methods for the determination
of MLD by forced mixing are utilized to test the extent of mechanical mixing within the top layer of water by the local wind
and wave activity. The same is extended to formulate a new empirical relation for gross estimation of effective depth within
which the sound energy is generally trapped during its transmission in the surface duct. The present analysis aiming for estimation
of observed MLD variability (35 to 75 m) using the suggested simple empirical relation reveals that, the mixed layer variability
observed during the experiment depends on both local ocean variability as well as remote forcing as reported earlier. 相似文献
18.
In this paper, the problem of spatially homogeneous and an isotropic Bianchi type-1 space time with perfect fluid distribution
is considered in Barber's second theory of gravitation. To obtain determinate solutions, we have assumed the equation of statep= γρ, 0 ≤ γ ≤ 1. It is observed that the general fluid distribution degenerates isotropic vacuum model whenγ = 1 and Λ < 0.
Further it is observed that the vacuum model obtained in case of γ = 0, ρ = 0 andΛ = 0, reduces to well known Kasner model
in Einstein's theory. Some physical and geometrical aspects of the models together with singularities in the models are also
discussed
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Jitendra Pandey Dheeraj Kumar D. C. Panigrahi V. K. Singh 《Environmental Earth Sciences》2017,76(12):439
Coal is dominant energy source of world at large and India in particular for several decades and expected to being continued for foreseeable future. However, fire in this fossils fuel is still a global catastrophe for the major coal-producing countries. There are several direct and cascading distress of coal mine fire has been encountered by environment, economy, safety and society. Without knowledge of actual status and extent of coal mine fire, any scope for its better managements may be futile. In India, the coal mine fire of well-known Jharia coalfield (JCF) has been continued since last ten decades and still spreading towards newer areas. The aim of this paper is to highlight the chronological net lateral spatial changes in coal mine fire areas of JCF using Landsat satellite thermal imageries. The mapping of coal mine fire area of JCF during 1988–2013 has been carried out with consecutive 5-year intervals. The lateral changes in surface and subsurface fire areas along with propagation towards new area have been studied. The study also included to evaluate changes of status and extent fire during this time span and effect of its management efforts. On the basis of aforementioned analysis, the study concludes a slow reducing trend in coal mine fire area during last 25 years. 相似文献
20.
Minimal time ship routing is studied between Mumbai port (India) to Mombasa port (Kenya) using model hindcast wave climate over the Arabian Sea. With the launch of IRS-P4 (OCEANSAT-I), it became possible now to carry out routine wave hindcasting over the Indian Ocean. The MSMR channel of the satellite gives scalar wind, which is analyzed at NCMRWF, India, for converting to vector winds. The same is used as input to third-generation spectral wave model WAM for regional grid system for simulating the rough weather period of July 2000. This simulated wave climate formed the basis for computing effective ship velocity in the irregular seaway. This study gives a quantitative estimation of change in ship velocity in the open Indian Ocean for a bulk carrier. The minimal time path is charted using Dijkstra's algorithm for optimum route voyage. The optimum track information has broad scope for obtaining a safer route, least time route by avoiding delay in schedule with minimum fuel consumption. 相似文献