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71.
Raka Dona Ray Mandal Sushan Konar Mira Dey Jishnu Dey 《Monthly notices of the Royal Astronomical Society》2009,399(2):822-826
The single glitch observed in PSR B1821−24, a millisecond pulsar in M28, is unusual on two counts. First, the magnitude of this glitch is at least an order of magnitude smaller (Δν/ν∼ 10−11 ) than the smallest glitch observed to date. Secondly, all other glitching pulsars have strong magnetic fields with B ≳ 1011 G and are young, whereas PSR B1821−24 is an old recycled pulsar with a field strength of 2.25 × 109 G . We have earlier suggested that some of the recycled pulsars could actually be strange quark stars. In this work, we argue that the crustal properties of such a strange pulsar are just right to give rise to a glitch of this magnitude, explaining the scarcity of larger glitches in millisecond pulsars. 相似文献
72.
Andrew Barnes Devin J. Sapsford Mathew Dey Keith P. Williams 《Journal of Geochemical Exploration》2009,100(2-3):192-198
The determination of electrophoretic mobility and zeta potential was used as a diagnostic tool, alongside kinetic experiments, to delineate between three plausible mechanisms for the heterogeneous oxidation of Fe(II) by dissolved oxygen. One of these mechanisms is dependant on the positive surface charge that exists on Fe(III) (oxy)hydroxide surfaces at pH values below the Iso-Electric Point (IEP). However, this mechanism can be disputed as catalysis is observed on Fe(III) (oxy)hydroxide surfaces above the IEP despite a negative zeta potential. As well as an IEP shift an overall reduction of the magnitude of the zeta potential is observed in samples of field Fe(III) (oxy)hydroxide collected from the Taff Merthyr mine water treatment site in South Wales, UK. Low zeta potentials determined in mine water treatment systems will have beneficial effects for particle coagulation and settling in passive mine water treatment systems. 相似文献
73.
N. Janardhana Raju Prahlad Ram Sangita Dey 《Journal of the Geological Society of India》2009,73(2):178-192
The lower Varuna River basin in Varanasi district situated in the central Ganga plain is a highly productive agricultural
area, and is also one of the fast growing urban areas in India. The agricultural and urbanization activities have a lot of
impact on the groundwater quality of the study area. The river basin is underlain by Quaternary alluvial sediments consisting
of clay, silt, sand and gravel of various grades. The hydrogeochemical study was undertaken by randomly collecting 75 groundwater
samples from dug wells and hand pumps covering the entire basin in order to understand the sources of dissolved ions, and
to assess the chemical quality of the groundwater through analysis of major ions. Based on the total dissolved solids, two
groundwater samples are considered unsuitable for drinking purpose, but all samples are useful for irrigation. Graphical treatment
of major ion chemistry by Piper diagram helps in identifying hydro-geochemical facies of groundwaters and the dominant hydrochemical
facies is Ca-Mg-HCO3 with appreciable percentage of the water having mixed facies. As per Wilcox’s diagram and US Salinity laboratory classification,
most of the groundwater samples are suitable for irrigation except two samples (No’s 30 and 68) which are unsuitable due to
the presence of high salinity and medium sodium hazard. Irrigation waters classified based on residual sodium carbonate, have
revealed that all groundwaters are in general safe for irrigation except one sample (No. 27), which needs treatment before
use. Permeability index indicates that the groundwater samples are suitable for irrigation purpose.
Although the general quality of groundwater of the lower Varuna River basin is suitable for irrigation purpose, fifty seven
percent of the samples are found having nitrate content more than permissible limit (>45 mg/l) which is not good for human
consumption. Application of N-Fertilizers on agricultural land as crop nutrients along the Varuna River course may be responsible
for nitrate pollution in the groundwater due to leaching by applied irrigation water. The other potential sources of high
nitrate concentration in extreme northern, southern and southwestern parts of study area are poor sewerage and drainage facilities,
leakage of human excreta from very old septic tanks, and sanitary landfills. The high fluoride contamination (>1.5 mg/l) in
some of the samples may be due to the dissolution of micaceous content in the alluvium. Nitrate and fluoride contamination
of groundwater is a serious problem for its domestic use. Hence an immediate protective measure must be put into action in
the study area. 相似文献
74.
Image fusion assists in visual interpretation, mapping, change detection and many other applications. Multispectral and Panchromatic
images are fused to produce images having enhanced spatial and spectral properties. These properties are generally distorted
from original images. The aim of this paper is to identify the effectiveness of the several fusion techniques based on the
distortions and applications. This paper employs seven image fusion techniques namely, Brovey transform, intensity hue saturation,
high pass filter, principle component analysis, UNB Pansharpening, wavelet transform and multiplicative, available in various
commercial image processing software. The data for this study are panchromatic image of Cartosat-1 and multispectral image
of IRS - P6 LISS 4 sensor of study area, Bhopal Municipal Corporation area, M.P. State, India. The effectiveness of image
fusion techniques is determined by quantitative and qualitative assessments. Quantitative assessment is divided into two parts:
1) assessment of fusion techniques by statistical parameters and 2) accuracy assessment of land use maps generated from the
fused images. For part 1, three parameters namely, mean bias, correlation coefficient and Q4 quality index, have been used.
Based on the results of part 1, UNB Pansharpening and wavelet transform are the best among seven fusion techniques. For part
2, Gaussian and Artificial Neural Network classifiers have been used to generate land cover maps. However, the accuracy results
are inconclusive to identify a single best method. Nevertheless, image fusion by wavelet transform has provided best results
in both the sector. Hence, wavelet transform is concluded as the best among selected fusion techniques. 相似文献
75.
Radhika?Patro S.?N.?Mahapatro A.?BhattacharyaEmail author N.?C.?Pant J.?K.?Nanda A.?Dey A.?K.?Tripathy 《Contributions to Mineralogy and Petrology》2011,161(4):547-563
The origin of chemical and mineralogical heterogeneity in tens-of-microns wide layers and domains in enderbite-hosted couple-of-centimeters
wide pseudotachylite vein is examined based on the results of BSE and X-ray element imaging, and electron probe microanalyses
of major elements of host-rock minerals, clasts, microphenocrysts, and pseudotachylite matrix. The pseudotachylite layers
and domains containing variable proportions of orthopyroxene and magnetite microphenocrysts continue as mantles around quartz,
K-feldspar, plagioclase and garnet clasts. The clasts are chemically modified along margins and intra-clast pseudotachylite
injections. The chemical modifications are extensive in smaller clasts <5 μm diameter. At least three chemically distinct
layers and domains in the pseudotachylite, and their fine-grained matrices, plot in sharply defined, well-segregated and non-overlapping
fields in FeO + MgO−Al2O3–SiO2, FeO–CaO–MgO and CaO–Na2O–K2O and FeO vs. FeO/FeO + MgO diagrams. The compositions of the layers and domains—smeared between a feldspar + quartz component
and a ferromagnesian component of garnet + Fe–Ti oxides (±orthopyroxene)—possibly correspond to fractionated quenched melts,
or admixtures of microphenocrysts that cannot be resolved by the microbeam techniques employed. The compositional variations
are incompatible with deformation-driven crystal fractionation in melt. Instead the layers and domains possibly are crystal-melt
mushes produced by syn-deformation ultra-high temperature (1,250–1,375°C) melting reactions involving variable proportions
of host-rock minerals determined by time-transient local phase aggregates experiencing strain. The similar element variation
trends in pseudotachylite examined here and those reported from anorthosite, metapelite and charnockite elsewhere suggests
local phase aggregate controlled multi-reaction melting is a phenomenon commoner than hitherto realized in pseudotachylites. 相似文献
76.
Sukanta Goswami P K Upadhyay Sangeeta Bhagat Syed Zakaulla A K Bhatt V Natarajan Sukanta Dey 《Journal of Earth System Science》2018,127(2):20
The lower stratigraphic part of the Cuddapah basin is marked by mafic and felsic volcanism. Tadpatri Formation consists of a greater variety of rock types due to bimodal volcanism in the upper part. Presence of bimodal volcanism is an indication of continental rift setting. Various genetic processes involved in the formation of such volcanic sequence result in original textures which are classified into volcaniclastic and coherent categories. Detailed and systematic field works in Tadpatri–Tonduru transect of SW Cuddapah basin have provided information on the physical processes producing this diversity of rock types. Felsic volcanism is manifested here with features as finger print of past rhyolite-dacite eruptions. Acid volcanics, tuffs and associated shale of Tadpatri Formation are studied and mapped in the field. With supporting subordinate studies on geochemistry, mineralogy and petrogenesis of the volcanics to validate field features accurately, it is understood that volcanism was associated with rifting and shallow marine environmental condition. Four facies (i.e., surge, flow, fall and resedimented volcaniclastic) are demarcated to describe stratigraphic units and volcanic history of the mapped area. The present contribution focuses on the fundamental characterization and categorization of field-based features diagnostic of silica-rich volcanic activities in the Tadpatri Formation. 相似文献
77.
Manjari Bagchi Subharthi Ray Mira Dey † Jishnu Dey 《Monthly notices of the Royal Astronomical Society》2006,368(2):971-975
From recent reports on terrestrial heavy ion collision experiments it appears that one may not obtain information about the existence of asymptotic freedom (AF) and chiral symmetry restoration (CSR) for quarks of QCD at high density. This information may still be obtained from compact stars – if they are made up of strange quark matter (SQM).
Very high gravitational redshift lines (GRL), seen from some compact stars, seem to suggest high ratios of mass and radius ( M / R ) for them. This is suggestive of strange stars (SS) and can in fact be fitted very well with SQM equation of state (EOS) deduced with built in AF and CSR. In some other stars broad absorption bands (BAB) appear at about ∼0.3 keV and multiples thereof, that may fit in very well with resonance with harmonic compressional breathing mode frequencies of these SS. Emission at these frequencies are also observed in six stars.
If these two features of large GRL and BAB were observed together in a single star, it would strengthen the possibility for the existence of SS in nature and would vindicate the current dogma of AF and CSR that we believe in QCD. Recently, in 4U 1700 − 24 , both features appear to be detected, which may well be interpreted as observation of SS – although the group that analyzed the data did not observe this possibility. We predict that if the shifted lines, that has been observed, are from neon with GRL shift z = 0.4 – then the compact object emitting it is a SS of mass 1.2 M⊙ and radius 7 km. In addition the fit to the spectrum leaves a residual with broad dips at 0.35 keV and multiples thereof, as in 1E 1207 − 5209 which is again suggestive of SS. 相似文献
Very high gravitational redshift lines (GRL), seen from some compact stars, seem to suggest high ratios of mass and radius ( M / R ) for them. This is suggestive of strange stars (SS) and can in fact be fitted very well with SQM equation of state (EOS) deduced with built in AF and CSR. In some other stars broad absorption bands (BAB) appear at about ∼0.3 keV and multiples thereof, that may fit in very well with resonance with harmonic compressional breathing mode frequencies of these SS. Emission at these frequencies are also observed in six stars.
If these two features of large GRL and BAB were observed together in a single star, it would strengthen the possibility for the existence of SS in nature and would vindicate the current dogma of AF and CSR that we believe in QCD. Recently, in 4U 1700 − 24 , both features appear to be detected, which may well be interpreted as observation of SS – although the group that analyzed the data did not observe this possibility. We predict that if the shifted lines, that has been observed, are from neon with GRL shift z = 0.4 – then the compact object emitting it is a SS of mass 1.2 M
78.
79.
A study is conducted to estimate the accurate attitude of a ship's motion and the estimation is used to arrive at the corrections required for a farfield pattern of a coaxial circular array. The relevant analytical expression is developed for the computation of moving average filter weights to estimate the ship's attitude for beamsteerings at different sea conditions. Farfield patterns are presented for different steered directions for the coaxial circular array of the additive type, and the multiplicative array technique is also used for beamsteering for higher steering angles to observe its control on the sidelobes as well as for the main beamwidths. In order to introduce an adaptive filter to estimate the accurate attitude for stable sonar platform, an adaptive parameter is examined for bathymetric applications where nonstationary ship movement prevails. 相似文献
80.
Mitali Dey Chumki Chowdhury Asim A. Pattnaik Dipnarayan Ganguly Sandip K. Mukhopadhyay Tarun K. De Tapan K. Jana 《Marine Ecology》2013,34(1):14-29
Ongoing climate change and anthropogenic activities are introducing stressors that affect the structure and function of coastal ecosystems. This paper focuses on the fluvial fluxes and estuarine transport of nutrients from a tropical river (Mahanadi River) in Northeastern India and compares select nutrient and water quality parameters between 1983 and 2008. This estuary acts as a perennial source of CO2 with a net annual flux to the atmosphere of about 135 tons. The non‐conservative fluxes showed a net annual removal of 650 and 140 tons of phosphorus and nitrogen from the water column, respectively. Negative biogeochemical feedbacks that decreased the availability of N and P in 2008 relative to 1983 levels indicate major changes in biogeochemical responses towards fluvial fluxes of nutrient. 相似文献