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71.
S. C. Patel S. Ravi S. S. Thakur T. K. Rao K. V. Subbarao 《Mineralogy and Petrology》2006,88(1-2):363-380
Summary Mineralogical characteristics of eclogite xenoliths from three kimberlite pipes (KL2, P2 and P10) of the Proterozoic Wajrakarur
kimberlite field of southern India have been studied. In a rare sample of enstatite eclogite from the KL2 pipe garnet contains
microscopic triangular arrays of needles or blebs of omphacite, enstatite and rutile consistent with an origin by exsolution
parallel to the isometric form {111}. Discrete omphacite grains in the sample contain exsolved needles or blebs of enstatite
and garnet. Kyanite eclogites are abundant in the KL2 pipe which occasionally show a secondary ring of pure celsian around
kyanite grains. Omphacite Na2O contents in the eclogites of the KL2 and P2 pipes are typically between 3 and 6 wt%, and garnet has widely variable composition
with end member ranges of Prp22-81Grs0-47Alm10-30Sps0-1Adr0-5Uv0-3. Eclogites of the P10 pipe comprise chromian omphacite
and garnet. Phase relations in the ACF projection exhibit systematic increase of the Ca-Tschermak’s component in omphacite
from enstatite eclogite through biminerallic eclogite to kyanite eclogite. Garnet-clinopyroxene Fe–Mg geothermometry yields
temperatures mostly in the range of 900–1100 °C. A formerly supersilicic nature of garnet in enstatite eclogite as inferred
from exsolution mineralogy indicates minimum peak pressure of 5 GPa. 相似文献
72.
M Poza NITA Bhagia J H Patel SUJAY Dutta V K Dadhwal 《Journal of the Indian Society of Remote Sensing》1996,24(4):243-254
I he aim of the piesent study was to suggest an approach for national level acreage estimation for wheat using satellite remote sensing data and demonstrate its perfromantee Multi-date moderate resolution (188 m) IRS-IC WiFS data sets were used as the core data Sampie segment approach with stratified random sampling was used for the data analysis For making meaningful comparisons over time, multi-date sets were geometncally registered and radiometrically normalised by extracting pseudo-invariant Features and performing regression analysis on the digital numbers of such features The corrected multi-temporal data sets were used in hierarchical classification scheme. The results of this exercise are presented. It appeals that there is an overestimatoin of wheat acreage The sampling effieieney was also low, indicating need to improve sampling strategy Some of the problems encountered and the corrections planned to overcome them are also discussed 相似文献
73.
Dhruvesh P. Patel Jorge A. Ramirez Prashant K. Srivastava Michaela Bray Dawei Han 《Natural Hazards》2017,89(1):93-130
Surat city of India, situated 100 km downstream of Ukai Dam and 19.4 km upstream from the mouth of River Tapi, has experienced the largest flood in 2006. The peak discharge of about 25,770 m3 s?1 released from the Ukai Dam was responsible for a disaster. To assess the flood and find inundation in low-lying areas, simulation work is carried out under the 1D/2D couple hydrodynamic modeling. Two hundred ninety-nine cross sections, two hydraulic structures and five major bridges across the river are considered for 1D modeling, whereas a topographic map at 0.5 m contour interval was used to produce a 5 m grid, and SRTM (30 and 90 m) grid has been considered for Surat and the Lower Tapi Basin. The tidal level at the river mouth and the release from the Ukai Dam during 2006 flood are considered as the downstream and upstream boundaries, respectively. The model is simulated under the unsteady flow condition and validated for the year 2006. The simulated result shows that 9th August was the worst day in terms of flooding for Surat city and a maximum 75–77% area was under inundation. Out of seven zones, the west zone had the deepest flood and inundated under 4–5 m. Furthermore, inundation is simulated under the bank protection work (i.e., levees, retaining wall) constructed after the 2006 flood. The simulated results show that the major zones are safe against the inundation under 14,430 m3 s?1 water releases from Ukai Dam except for the west zone. The study shows the 2D capability of new HEC-RAS 5 for flood inundation mapping and management studies. 相似文献
74.
Acta Geotechnica - The potential use of a hunchbacked retaining wall over a conventional retaining wall under the seismic passive state is emphasised in this study employing the method of stress... 相似文献
75.
Joy Sanyal Priyanka Dasgupta Shinjiro Kanae 《Singapore journal of tropical geography》2020,41(2):284-298
Dam-related downstream adjustments of riverbeds are normally investigated by analysing the trend in sediment supply and high flow events during the pre- and post-dam periods. The required data for existing predictive models is not measured at river gauges, which limits the application of these tools. We derived the frequency of sediment-transporting streamflow events (T*) and upstream sediment supply (S*) in the pre- and post-dam periods with widely available gauged records and predicted changes in the downstream riverbed by adapting an existing model. Ten gauging stations in the Godavari River Basin, India, located downstream of dams, were chosen as study sites. Annually surveyed cross-sections at each site validated the accuracy of the predicted dam-related downstream changes. Then, a regression equation (R2 = 0.75) was established between T*/S* (independent variable) and changes in the downstream bed elevation (dependent variable) for the Godavari Basin. We recommended that similar local empirical equations be formulated for larger river basins. Models of large-scale rainfall-runoff and sediment transport processes that can account for the influence of dams, such as the Soil & Water Assessment Tool, can be paired with the proposed regression equation to estimate dam-related downstream erosion and deposition with globally available data. 相似文献
76.
This paper presents observations of SiO maser emission from 161 Mira variables distributed over a wide range of intrinsic
parameters like spectral type, bolometric magnitude and amplitude of pulsation. The observations were made at 86.243 GHz,
using the 10-4 m millimeter-wave telescope of the Raman Research Institute at Bangalore, India. These are the first observations
made using this telescope. From these observations, we have established that the maser emission is restricted to Miras having
mean spectral types between M6 and M10. The infrared period-luminosity relation for Mira variables is used to calculate their
distances and hence estimate their maser luminosities from the observed fluxes. The maser luminosity is found to be correlated
with the bolometric magnitude of the Mira variable. On an H-R diagram, the masing Mira variables are shown to lie in a region
distinct from that for the non-masing ones. 相似文献
77.
A method of seismic zonation based on deterministic modeling of rupture plane is presented in this work. This method is based
on the modeling of finite rupture plane along identified lineaments in the region using the semi-empirical technique, of Midorikawa
[(1993) Tectonophysics 218:287–295]. The modeling procedure follows ω2 scaling law, directivity effects, and other strong motion parameters. The technique of zonation is applied for technoeconomically
important NE part of Brahmaputra valley that falls in the seismic gap region of Himalaya. Zonation map prepared for Brahmaputra
valley for earthquakes of magnitude M > 6.0 show that approximately 90,000 km2 area fall in the highly hazardous zone IV, which covers region that can have peak ground accelerations of order more than
250 cm/s2. The zone IV covers the Tezu, Tinsukia, Dibrugarh, Ziro, North Lakhimpur, Itanagar, Sibsagar, Jorhat, Golaghat, Wokha, Senapati,
Imphal, and Kohima regions. The Pasighat, Daring, Basar, and Seppa region belong to zone III with peak ground accelerations
of the order 200–250 cm/s2. The seismic zonation map obtained from deterministic modeling of the rupture is consistent with the historical seismicity
map and it has been found that the epicenter of many moderate and major earthquakes fall in the identified zones. 相似文献
78.
Geology and geochemistry of giant quartz veins from the Bundelkhand Craton,central India and their implications 总被引:1,自引:0,他引:1
J. K. Pati S. C. Patel K. L. Pruseth V. P. Malviya M. Arima S. Raju P. Pati K. Prakash 《Journal of Earth System Science》2007,116(6):497-510
Giant quartz veins (GQVs; earlier referred to as ‘quartz reefs’) occurring in the Archean Bundelkhand Craton (29,000 km2) represent a gigantic Precambrian (∼2.15 Ga) silica-rich fluid activity in the central Indian shield. These veins form a
striking curvilinear feature with positive relief having a preferred orientation NE-SW to NNE-SSW in the Bundelkhand Craton.
Their outcrop widths vary from ≤1 to 70m and pervasively extend over tens of kilometers along the strike over the entire craton.
Numerous younger thin quartz veins with somewhat similar orientation cut across the giant quartz veins. They show imprints
of strong brittle to ductile-brittle deformation, and in places are associated with base metal and gold incidences, and pyrophyllite-diaspore
mineralization. The geochemistry of giant quartz veins were studied. Apart from presenting new data on the geology and geochemistry
of these veins, an attempt has been made to resolve the long standing debate on their origin, in favour of an emplacement
due to tectonically controlled polyphase hydrothermal fluid activity. 相似文献
79.
Diagnostic infrared spectra of individual nanogram-sized interplanetary dust particles (IDPs) collected in the Earth's stratosphere have been obtained. A mount containing three crushed “chondritic” IDPs shows features near 1000 and 500 cm?1, suggestive of crystalline pyroxene, and different from those of crystalline olivine, amorphous olivine, or meteoritic clay minerals. The structural diversity of chondritic IDPs and possible effects of atmospheric heating must be considered when comparing this spectrum with astrophysical spectra of interplanetary and cometary dust. Transmission electron microscope (TEM) and infrared observations are also reported on one member of the rare subset of IDPs which resemble hydrated carbonaceous chondrite matrix material. The infrared spectrum of this particle between 4000 and 400 cm?1 closely matches that of the C2 meteorite Murchison. TEM observations suggest that this class of particles might serve as a thermometer for the process of heating on atmospheric entry. 相似文献
80.
The interplanetary magnetic field has been shown to influence the ring current field represented by Dst. Explorer 28 hourly magnetic field observations have been used with the hourly Dst values. The moderate geomagnetic storms of 60 and quiet-time fluctuations of 10–30 are correlated with the North to South change of the interplanetary field component perpendicular to the ecliptic. This change in the interplanetary field occurs one to three hours earlier than the corresponding change in the Dst field. 相似文献