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31.
GeoJournal - Urban expansion of the Indian metropolitan cities has reached the rural peripheries. There have been social, economic, and environmental consequences of this process of... 相似文献
32.
K. V. S. Badarinath Shailesh Kumar Kharol V. Krishna Prasad Anu Rani Sharma E. U. B. Reddi H. D. Kambezidis D. G. Kaskaoutis 《Journal of Atmospheric Chemistry》2008,59(3):219-236
Measurements of total ozone column and solar UV radiation under different atmospheric conditions are needed to define variations
of both UV and ozone and to study the impact of ozone depletion at the Earth’s surface. In this study, spectral and broadband
measurements of UV-B irradiance were obtained along with total ozone observations and aerosol optical depth measurements in
the tropical urban region of Hyderabad, south India. We specifically used an Ultra-Violet Multifilter Rotating Shadow band
Radiometer (UVMFR-SR), to measure UV irradiance in time and space. To assess the aerosol and O3 effects on ground-reaching UV irradiance, we used measurements from a Microtops II sun photometer in addition to the Tropospheric
Ultraviolet Visible radiation (TUV) model. We also assessed the Defense Meteorological Satellite Program – Operational Line
Scanner (DMSP-OLS) night time satellite data for inferring biomass burning fires during the study period. Results clearly
suggested a negative correlation between the DMSP-OLS satellite derived fire count data and UVMFR-SR data suggesting that
aerosols from biomass burning are directly attenuating UV irradiance in the study region. Also, correlation analysis between
UV index and ozone measurements from sun photometer and TOMS-Ozone Mapping Instrument (OMI) indicated a clear decrease in
ground reaching UV-B irradiance during higher ozone conditions. The higher levels are attributed to photochemical production
of O3 during the oxidation of trace gases emitted from biomass burning. Results also suggested a relatively high attenuation in
UV irradiance (~6% higher) from smoke particles than dust. We also found a relatively good agreement between the modeled (TUV)
and measured UV irradiance spectra for different atmospheric conditions. Our results highlight the factors affecting UV irradiance
in a tropical urban environment, south India. 相似文献
33.
K. V. S. Badarinath Anu Rani Sharma Shailesh Kumar Kharol V. Krishna Prasad 《Journal of Atmospheric Chemistry》2009,62(1):73-86
Carbon monoxide (CO), Ozone (O3) and Black Carbon (BC) aerosol mass concentrations in relation to planetary boundary layer (PBL) height measurements were
analyzed from January–December, 2008 over tropical urban environment of Hyderabad, India. DMSP-OLS night-time satellite data
were analyzed for fire occurrence over the region and its correlation with pollution concentrations over the urban region.
Results of the study suggested considerable increase in CO and BC concentrations during early morning hours. Higher concentration
of BC, CO and ozone was observed during pre-monsoon, post-monsoon and winter and lowest concentrations exhibited during monsoon
season. NCEP/NCAR reanalysis winds suggested long range transport of aerosols and trace gases from forest fires are enhancing
the pollutant concentrations over the study area. 相似文献
34.
- The present investigation was undertaken to evaluate the effects of three sublethal concentrations (1/10th, 1/15th and 1/20th fractions of 96 h LC50) of phenol (P), dinitrophenol (DNP), pentachlorophenol (PCP) and their antagonistic [(PCP + DNP)/P], additive [(DNP + P)/PCP] and synergistic [(P + DNP)/PCP] combinations, on several organic and inorganic components of haemopoetic systems of Notopterus notopterus after 30 d of exposure.
- Glucose, lactate, total phosphorus, non-protein nitrogen, sodium, potassium, magnesium, calcium, iron and chloride were found to be increased in most cases while protein and cholesterol were found to be decreased.
- It has been concluded that these alterations in blood parameters might be due to a damage or hyperactivity of liver, kidney and endocrine glands, the main centres for controlling the tissue metabolism.
35.
NARX neural network approach for the monthly prediction of groundwater levels in Sylhet Sadar,Bangladesh 下载免费PDF全文
Abdullah Al Jami Meher Uddin Himel Khairul Hasan Shilpy Rani Basak Ayesha Ferdous Mita 《地下水科学与工程》2020,8(2):118-126
Groundwater is important for managing the water supply in agricultural countries like Bangladesh. Therefore, the ability to predict the changes of groundwater level is necessary for jointly planning the uses of groundwater resources. In this study, a new nonlinear autoregressive with exogenous inputs(NARX) network has been applied to simulate monthly groundwater levels in a well of Sylhet Sadar at a local scale. The Levenberg-Marquardt(LM) and Bayesian Regularization(BR) algorithms were used to train the NARX network, and the results were compared to determine the best architecture for predicting monthly groundwater levels over time. The comparison between LM and BR showed that NARX-BR has advantages over predicting monthly levels based on the Mean Squared Error(MSE), coefficient of determination(R~2), and Nash-Sutcliffe coefficient of efficiency(NSE). The results show that BR is the most accurate method for predicting groundwater levels with an error of ± 0.35 m. This method is applied to the management of irrigation water source, which provides important information for the prediction of local groundwater fluctuation at local level during a short period. 相似文献
36.
M. Thamban S. S. Naik R. Mohan A. Rajakumar N. Basavaiah Witty D’Souza Sarita Kerkar M. M. Subramaniam M. Sudhakar P. C. Pandey 《Journal of Earth System Science》2005,114(5):443-452
Changes in the terrigenous sediment source and transport mechanisms during the late Quaternary have been investigated using
four sediment cores within the Indian sector of Southern Ocean, using the magnetic susceptibility (MS) and sedimentological
records. Sediments deposited during the Holocene and other interglacial periods were characterised by low MS, low sand content,
reduced ice-rafted detritus (IRD) input and increased illite possibly transported via hydrographic advection from the south.
The glacial intervals are characterised by high MS, high sand content, increased IRD input and reduced illite clays, derived
from both local as well as Antarctic sources. Significant reduction in clay fraction and illite content during glacials suggests
that the erosive and transporting capabilities of the deep and bottom waters could have reduced compared to the interglacial
times. The changes in terrigenous influx to this region were significantly influenced by the rhythmic glacial-interglacial
fluctuations in bottom circulation and the position of the Polar Front. 相似文献
37.
The Biot linearized quasi-static theory of fluid-infiltrated porous materials is used to formulate the problem of the two-dimensional
plane strain deformation of a multi-layered poroelastic half-space by surface loads. The Fourier-Laplace transforms of the
stresses, displacements, pore pressure and fluid flux in each homogeneous layer of the multi-layered half-space are expressed
in terms of six arbitrary constants. Generalized Thomson-Haskell matrix method is used to obtain the deformation field. Simplified
explicit expressions for the elements of the 6 × 6 propagator matrix for the poroelastic medium are obtained. As an example
of the possible applications of the analytical formulation developed, formal solution is given for normal strip loading, normal
line loading and shear line loading. 相似文献
38.
The Biot linearized theory of fluid saturated porous materials is used to study the plane strain deformation of a two-phase
medium consisting of a homogeneous, isotropic, poroelastic half-space in welded contact with a homogeneous, isotropic, perfectly
elastic half-space caused by a two-dimensional source in the elastic half-space. The integral expressions for the displacements
and stresses in the two half-spaces in welded contact are obtained from the corresponding expressions for an unbounded elastic
medium by applying suitable boundary conditions at the interface. The case of a long dip-slip fault is discussed in detail.
The integrals for this source are solved analytically for two limiting cases: (i) undrained conditions in the high frequency
limit, and (ii) steady state drained conditions as the frequency approaches zero. It has been verified that the solution for
the drained case (ω → 0) coincides with the known elastic solution. The drained and undrained displacements and stresses are compared graphically.
Diffusion of the pore pressure with time is also studied. 相似文献
39.
K. S. Sajinkumar S. Anbazhagan A. P. Pradeepkumar V. R. Rani 《Journal of the Geological Society of India》2011,78(3):249-257
The climatic condition of Western Ghats has influenced the process of weathering and landslides in this mountainous tract
along the southwest coast of India. During the monsoon period, landslides are a common in the Western Ghats, and its intensity
depends upon the thickness of the loose unconsolidated soil formed by the process of weathering. Debris landslides with a
combination of saprock, saprolite and soil, indicate the role of weathering in landslide occurrences. This paper reports on
how the weathering in the windward slope of Western Ghats influences the occurrence of landslides and the factors which accelerate
the weathering process. Rock and soil samples were collected from the weathering profile of hornblende gniess and granite
gneiss. The chemical analysis and the calculated Chemical Index of Alteration (CIA) indicate the significant weathering and
its possible influence on landslide occurrences in the study area. Mainly, the CIA value of lateritic soil and forest loam
indicated the extent of high chemical weathering in this region. Rainfall is the dominant parameter influencing the chemical
weathering process. In addition, deforestation, land use practices and soil erosion are some of the other important factors
accelerating the weathering process and landslide occurrences in the region. The locations of the previous landslides superimposed
on geology and soil show that most of the landslide occurrences are associated with the highly weathered zone, particularly
lateritic soil and the ‘severe’ (rock outcrop) erodability zone. 相似文献
40.
Stability assessment and characterization of colloids in coastal groundwater aquifer system at Kalpakkam 总被引:1,自引:0,他引:1
Natural colloids have a potential role in facilitating the transport of radionuclides in groundwater. To assess the role of
mobile colloidal phases in radionuclide transport, characterization of colloids for size, size distribution, zeta potential,
surface charge and elemental composition is required. Groundwater samples were collected from 12 borewells in the study area
and were characterized with respect to physicochemical parameters. Water quality parameters such as pH, temperature, specific
conductance, TDS and dissolved O2 were measured in situ. Based on salinity, two groundwater types were identified in the study area: (1) freshwater type and
(2) brackish type. Laboratory and field-scale turbidity measurements in addition to quantitative analysis of major ions were
carried out. It was observed that the colloid concentrations are reduced at higher salinity. Zetasizer, particle size analyzer,
scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction techniques were used to characterize
the colloidal particles in groundwater. Colloids were present in all the groundwater samples, the concentration varying between
0.05 and 6 mg/L. Colloid concentration was greater in wells with low ionic strength and the number of colloidal particles
varied between 3 × 109 and 4 × 1011 particles/L. The average colloid size varied between 200 and 350 nm for various samples. The zeta potential of the colloidal
particles varied between −25.5 and –34.0 mV. SEM analysis of colloidal particles revealed the presence of clays particularly
kaolinite and that the mineral composition of colloids reflects the mineralogy of the aquifer. For proper risk assessment
and remediation studies, the role of colloids in radionuclide transport assumes greater importance. This study highlights
the need for, and relevance of, detailed colloid characterization to assess its role in the migration of radionuclides from
near surface disposal facilities. 相似文献