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11.
Controls on organic carbon distribution in sediments from the eastern Arabian Sea Margin 总被引:2,自引:0,他引:2
Sediment cores from the upper continental slope of the eastern Arabian Sea have high organic carbon (OC), CaCO3, and sand content at the top. The values decrease with increasing depth in the Holocene and Upper Pleistocene. Topographic
highs show highest OC and lower CaCO3 in the Holocene clayey sediments and vice versa in the Pleistocene sandy sediments. The OC is immature and marine or a mixture
of both marine and terrestrial in the Holocene sediments and is mostly terrestrial and/or reworked marine in the Pleistocene
sediments. Productivity is the main controlling factor for the organic carbon enrichment. Texture and reworking also influence
the organic carbon variations.
Received: 29 May 1996/Revision received: 10 January 1997 相似文献
12.
The radioelement and heavy mineral distribution in river, beach and innershelf areas of the southern Kerala coast is related
to placer mineral concentration on the beaches at Chavara. Southern Kerala rivers—Neyyar, Karamana and Vamanapuram—transport
higher amounts of radioactive elements than the larger Kallada River due to higher radioactive minerals in the hinterland
rocks. Coastal configurations and the seasonal longshore current pattern seems to control along-shore distribution of minerals.
The proposed model for placer concentration suggests that the energy difference and seasonal current direction along this
coast is important. 相似文献
13.
14.
The lifetimes and spatial scales of emission network cells in the solar chromosphere were studied from a nearly continuous sequence of Caii K filtergrams, obtained from Antarctica. The temporal autocorrelation function (ACF) was calculated for spatially-aligned windows from the time sequence of filtergrams. The lifetime of network cells was found to be dependent on the activity of the region. The estimated lifetimes are 24–34 hours for quiet-region cells and 58–61 hours for active-region cells. The temporal ACF shows prominent undulations in some of the quiet-region windows. The spatial ACF reveals the periodicity of the emission network in quiet regions. 相似文献
15.
A. K. Pathak M. Sridhar Y. Harsha A. Markandeyulu B. V. S. N. Raju A. K. Chaturvedi 《Journal of the Geological Society of India》2017,89(6):675-678
Aravalli fold belt has witnessed major tectonism resulting in intense deformation and associated mafic magmatism. Recently acquired high resolution aeromagnetic data over central Aravalli fold belt brought out a conspicuous E-W trending magnetic anomaly extending for more than 35 km in length cutting across the whole succession of Aravalli Supergroup. This anomaly on ground is manifested as undeformed basic dyke intruding into metasediments of Aravalli Supergroup. The E-W trend and undeformed nature of these dykes suggest that they represent post Aravalli mafic magmatism which are emplaced sympathetic to the axial plane of F3 folding. 相似文献
16.
K. S. Rao Girish Chandra C. Suresh Raju 《Journal of the Indian Society of Remote Sensing》1987,15(2):53-63
The dielectric property of the soil is an important parameter for microwave remote sensing. Therefore an attempt is made to study and compare the models for the dielectric constant of moist soils by considering three soil types namely Haldi series (sandy loam), Hathiapathar series (silt loam) and Jambria series (clay) and at frequencies 1.4, 4.0 and 18.0 GHz. The semiempirical models of Wang et al. (1980) and Dobson et al (1985) predict more or les same results in the domain of their applicability. However, at lower frequencies below 1.0 GHz, the imaginary part of dielectric constant shows a decreasing trend with decreasing frequency for Wang et al (1980) model whereas it shows reverse trend for Dobson et al (1985) model. The soil texture and frequency dependence of dielectric constant have been investigated for Indian soils. Some of the representative dielectric profiles of black soils of Pune have been computed using semiempirical model of Dobson et al (1985) which are useful for the development of multifrequency models for the study of soil moisture. 相似文献
17.
RedSanders in their natural distribution occur almost exclusively in quartzites and shales. This indicates the geobotanical
response to these rock types in the semi-arid tract of the southeastern portion of Andhra Pradesh in the tropical dry deciduous
forests of Chittoor, Cuddapah and Nellore districts. Thus Red Sanders are important from a commercial point of view and also
a useful tool to demarcate stratigraphic formations.
Received: 27 April 1998 · Accepted: 21 July 1998 相似文献
18.
Hydrogeochemical investigation and groundwater quality assessment of Pratapgarh district,Uttar Pradesh 总被引:3,自引:0,他引:3
Ashwani Kumar Tiwari Abhay Kumar Singh 《Journal of the Geological Society of India》2014,83(3):329-343
Hydogrochemical investigation of groundwater resources of Paragraph district has been carried out to assess the solute acquisition processes and water quality for domestic and irrigation uses. Fifty-five groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids, hardness, major anions (F?, Cl?, NO3, HCO3 ?, SO4 2?) and cations (Ca2+, Mg2+, Na+, K+). Study results reveal that groundwater of the area is alkaline in nature and HCO3 ?, Cl?, Mg2+, Na+ and Ca2+ are the major contributing ions to the dissolved solids. The hydrogeochemical data suggest that weathering of rock forming minerals along with secondary contributions from agricultural and anthropogenic sources are mainly controlling the groundwater composition of Pratapgarh district. Alkaline earth metals (Ca2++Mg2+) exceed alkalis (Na++K+) and weak acid (HCO3 ?) dominate over strong acids (Cl?+SO4 2?) in majority of the groundwater samples. Ca-Mg-HCO3 and Ca-Mg-Cl-HCO3 are the dominant hydrogeochemical facies in the groundwater of the area. The computed saturation indices demonstrate oversaturated condition with respect to dolomite and calcite and undersaturated with gypsum and fluorite. A comparison of groundwater quality parameters in relation to specified limits for drinking water shows that concentrations of TDS, F?, NO3 ? and total hardness exceed the desirable limits in many water samples. Quality assessment for irrigation uses reveal that the groundwater is good for irrigation. However, values of salinity, sodium adsorption ratio (SAR), residual sodium carbonate (RSC), %Na and Kelley index are exceeding the prescribed limit at some sites, demanding adequate drainage and water management plan for the area. 相似文献
19.
Biogeochemical investigation in south eastern Andhra Pradesh: the distribution of rare earths, thorium and uranium in plants and soils 总被引:4,自引:0,他引:4
The concentration of rare earth elements (REE), thorium and uranium were determined by inductively coupled plasma mass spectrometry
(ICP−MS) in the plant species, Pterocarpus santalinus, P. marsupium and P. dalbergioides, and the soils on which they were growing. Higher concentrations of lanthanum (La), cerium (Ce) were observed in both plants
and soils. Large amounts of thorium and uranium were found in the soil. In all tree species, the concentration of REEs were
higher in the heartwood than the leaves. The heartwood of P. santalinus accumulated larger quantities of uranium (average concentration of 1.22 ppm) and thorium (mean value of 2.57 ppm) than the
other two species.
Received: 8 September 1999 · Accepted: 15 December 1999 相似文献
20.
The first optical signatures of plasmapause associated processes were gleaned from the daytime auroral emissions monitored
from Maitri, the Indian station in Antarctica, using the newly built, ground-based, Multiwavelength Daytime Photometer (MWDPM).
The plasmapause boundary inferred from these measurements conforms well with the known empirical relationship with the geomagnetic
indexKp. The measurements made at 391.4, 486.1, 557.7 and 630.0 nm emissions revealed significant day-to-day variations in their
spatial and temporal extents. These preliminary results are presented and discussed. 相似文献