全文获取类型
收费全文 | 119篇 |
免费 | 7篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 9篇 |
地球物理 | 23篇 |
地质学 | 55篇 |
海洋学 | 4篇 |
天文学 | 14篇 |
综合类 | 2篇 |
自然地理 | 7篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 11篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1997年 | 1篇 |
排序方式: 共有126条查询结果,搜索用时 15 毫秒
61.
Effects of climate change on thermal properties of lakes and reservoirs, and possible implications 总被引:3,自引:2,他引:1
G. B. Sahoo S. G. Schladow J. E. Reuter R. Coats 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(4):445-456
Meteorologic-driven processes exert large and diverse impacts on lakes’ internal heating, cooling, and mixing. Thus, continued
global warming and climate change will affect lakes’ thermal properties, dynamics, and ecosystem. The impact of climate change
on Lake Tahoe (in the states of California and Nevada in the United States) is investigated here, as a case study of climate
change effects on the physical processes occurring within a lake. In the Tahoe basin, air temperature data show upward trends
and streamflow trends indicate earlier snowmelt. Precipitation in the basin is shifting from snow to rain, and the frequency
of intense rainfall events is increasing. In-lake water temperature records of the past 38 years (1970–2007) show that Lake
Tahoe is warming at an average rate of 0.013°C/year. The future trends of weather variables, such as air temperature, precipitation,
longwave radiation, downward shortwave radiation, and wind speed are estimated from predictions of three General Circulation
Models (GCMs) for the period 2001–2100. Future trends of weather variables of each GCM are found to be different to those
of the other GCMs. A series of simulation years into the future (2000–2040) is established using streamflows and associated
loadings, and meteorologic data sets for the period 1994–2004. Future simulation years and trends of weather variables are
selected so that: (1) future simulated warming trend would be consistent with the observed warming trend (0.013°C/year); and
(2) future mixing pattern frequency would closely match with the historical mixing pattern frequency. Results of 40-year simulations
show that the lake continues to become warmer and more stable, and mixing is reduced. Continued warming in the Tahoe has important
implications for efforts towards managing biodiversity and maintaining clarity of the lake. 相似文献
62.
63.
Sarata K. Sahoo Masahiro Hosoda Ganesh Prasad Hiroyuki Takahashi Atsuyuki Sorimachi Tetsuo Ishikawa Shinji Tokonami Shigeo Uchida 《Acta Geophysica》2013,61(4):876-885
The activity concentrations of 226Ra and 228Ac in weathered Japanese soils from two selected prefectures have been measured using a γ-ray spectroscopy system with high purity germanium detector. The uranium, thorium, and rare earth elements (REEs) concentrations were determined from the same soil samples using inductively coupled plasma mass spectrometry (ICP-MS). For example, granitic rocks contain higher amounts of U, Th, and light REEs compared to other igneous rocks such as basalt and andesites. Therefore, it is necessary to understand the interaction between REEs and nature of soils since soils are complex heterogeneous mixture of organic and inorganic solids, water, and gases. In this paper, we will discuss about distribution pattern of 238U and 232Th along with REEs in soil samples of weathered acid rock (granite) collected from two prefectures of Japan: Hiroshima and Miyagi. 相似文献
64.
65.
Rahul Tripathi Rabi N. Sahoo Vinay K. Sehgal R. K. Tomar Debashish Chakraborty S. Nagarajan 《Journal of the Indian Society of Remote Sensing》2012,40(1):19-28
The current development of satellite technology particularly in the sensors like POLDER and MISR, has emphasized more on directional
reflectance measurements (i.e. spectral reflectance of the target measured from different view zenith and azimuth angles)
of the earth surface features mainly the vegetation for retrieval of biophysical parameters at regional scale using radiative
transfer models. This approach being physical process based and uses directional reflectance measurement has been found to
better and more reliable compared to the conventional statistical approach used till date and takes care of anisotropic nature
(i.e. reflectance from the target is different if measured from different view angles) of the target. Keeping this in view
a field experiment was conducted in mustard crop to evaluate the radiative transfer model for biophysical parameter retrieval
through its inversion with the objectives set as (i) to relate canopy biophysical parameters and geometry to its bidirectional
reflectance, (ii) to evaluate a canopy reflectance model to best represent the radiative transfer within the canopy for its
inversion and (iii) to retrieve crop biophysical parameters through inversion of the model. Two varieties of the mustard crop
(Brassica juncea L) were grown with two nitrogen treatments. The bidirectional reflectance data obtained at 5 nm interval
for a range of 400–1100 nm were integrated to IRS LISS–II sensor’s four band values using Newton Cotes Integration technique.
Biophysical parameters like leaf area index, leaf chlorophyll content, leaf length, plant height and average leaf inclination
angle, biomass etc were estimated synchronizing with the bi-directional reflectance measurements. Radiative transfer model PROSAIL model was
validated and its inversion was done to retrieve LAI and ALA. Look Up Table (LUT) of Bidirectional reflectance distribution
function (BRDF) was prepared simulating through PROSAIL model varying only LAI (0.2 interval from 1.2 to 5.4 ) and ALA (5°
interval from 40° to 55°) parameters and inversion was done using a merit function and numerical optimization technique given
by Press et al. (1986). The derived LAI and ALA values from inversion were well matched with observed one with RMSE 0.521
and 5.57, respectively. 相似文献
66.
Process-based groundwater models are useful to understand complex aquifer systems and make predictions about their response to hydrological changes. A conceptual model for evaluating responses to environmental changes is presented, considering the hydrogeologic framework, flow processes, aquifer hydraulic properties, boundary conditions, and sources and sinks of the groundwater system. Based on this conceptual model, a quasi-three-dimensional transient groundwater flow model was designed using MODFLOW to simulate the groundwater system of Mahanadi River delta, eastern India. The model was constructed in the context of an upper unconfined aquifer and lower confined aquifer, separated by an aquitard. Hydraulic heads of 13 shallow wells and 11 deep wells were used to calibrate transient groundwater conditions during 1997–2006, followed by validation (2007–2011). The aquifer and aquitard hydraulic properties were obtained by pumping tests and were calibrated along with the rainfall recharge. The statistical and graphical performance indicators suggested a reasonably good simulation of groundwater flow over the study area. Sensitivity analysis revealed that groundwater level is most sensitive to the hydraulic conductivities of both the aquifers, followed by vertical hydraulic conductivity of the confining layer. The calibrated model was then employed to explore groundwater-flow dynamics in response to changes in pumping and recharge conditions. The simulation results indicate that pumping has a substantial effect on the confined aquifer flow regime as compared to the unconfined aquifer. The results and insights from this study have important implications for other regional groundwater modeling studies, especially in multi-layered aquifer systems. 相似文献
67.
Bhabagrahi Sahoo Muthiah Perumal Tommaso Moramarco Silvia Barbetta Soumyaranjan Sahoo 《水文科学杂志》2020,65(3):335-347
ABSTRACTStream gauge-based information is the foundation for many hydrological applications in a river basin including the aquatic-habitat conservation. A simple two-parameter model for routing streamflow depth (alternatively, stream–stage) hydrographs and estimating corresponding discharge hydrographs in river channels is proposed using the multilinear approach, based on Nash-type discrete-cascade model. The applicability of this model is investigated by extending its framework to the realm of compound cross-section trapezoidal channels for both in-bank and overbank flows by using 20 flood events of the Tiber River in the Umbria region of Central Italy, and subsequently comparing the simulated results with the corresponding simulations of the HEC-RAS (Hydrologic Engineering Center – River Analysis System) hydrodynamic model and observed flow depth hydrographs. The field application, comparative study, and uncertainty and sensitivity analysis of the results demonstrate that the proposed multilinear discrete Nash-cascade stage-hydrograph (MDNS) routing model has the potential for routing floods in real-world rivers and canal irrigation systems, especially in operational mode. 相似文献
68.
Manganese ores of Nishikhal occur as distinctly conformable bands in the khondalite suite of rocks belonging to the Precambrian
Eastern Ghats complex of south Orissa, India. Manganese minerals recorded are cryptomelane, romanechite, pyrolusite, with
minor amounts of jacobsite, hausmannite, braunite, lithiophorite, birnessite and pyrophanite. Goethite, graphite, hematite
and magnetite are the other opaque minerals and quartz, orthoclase, garnet, kaolinite, apatite, collophane, fibrolite, zircon,
biotite and muscovite are the gangue minerals associated with these ores. The mineral chemistry of some of the phases, as
well as the modes of association of phosphorous in these ores have been established. The occurrence of well-defined bands
of manganese ore; co-folding of manganese ore bands and associated metasedimentary country rocks; the min-eral assemblage
of spessartite-sillimanite-braunite-jacobsite-hausmannite; the geochemical association of Mn-Ba-Co-Ni-Zn together with the
Si versus Al and Na versus Mg plots of the manganese ores suggest that the Nishikhal deposit is a metamorphosed Precambrian
lacustrine deposit. Continental weathering appears to be the source for manganese and iron. After deposition and probable
diagenesis, the manganese-rich sediments were metamorphosed along with conformable psammitic and pelitic sediments under granulite
facies conditions, and subsequently underwent supergene enrichment to produce the present deposit.
Received: 14 March 1995 / Accepted: 11 April 1996 相似文献
69.
Shreerup Goswami Kamaljyoti Das Mrutyunjaya Sahoo Soumyaranjan Bal Sanghamitra Pradhan Kamal Jeet Singh Anju Saxena 《Arabian Journal of Geosciences》2018,11(17):524
The present megafloral assemblage recorded from the Barakar sediments of Dholpahar section along Singda rivulet near Gopal Prasad Village in Talcher Basin comprises of equisetaceous stems, Gangamopteris buriadica, Palaeovittaria kurzii and 19 species of the genus Glossopteris. Record of Gangamopteris, Palaeovittaria and many narrow mesh forms of Glosspteris viz., G. angustifolia, G. churiensis, G. communis, G. recurva, G. spatulata, G. stenoneura, G. tenuifolia, G. vulgaris and G. zeilleri from two older fossiliferous horizons demonstrates that these fossils were preserved during Lower Barakar sedimentation. The report of middle and broad mesh forms of Glossopteris viz., G. barakarensis, G. browniana, G. indica, G. intermittens, G. karharbariensis, G. nakkarea, G. oldhamii, G. taeniensis and G. retifera in the youngest fossiliferous horizons reveals that these fossils were preserved during the deposition of Upper Barakar sediments. The continuation of some of the Karharbari plant fossils in the early phase of Barakar Formation and their disappearance in the flora of Late Barakar suggests a shift in the climatic setup. Palaeoclimate and palaeovegetation of this area are also summarised in this study. Moreover, the fossil assemblages of different fossiliferous beds of Dholpahar section demonstrate the evolution of midrib and meshes in different reticulate leaves. 相似文献
70.
Pulakesh Das Mukunda Dev Behera Nitesh Patidar Bhabagrahi Sahoo Poonam Tripathi Priti Ranjan Behera S K Srivastava Partha Sarathi Roy Praveen Thakur S P Agrawal Y V N Krishnamurthy 《Journal of Earth System Science》2018,127(2):19
As a catchment phenomenon, land use and land cover change (LULCC) has a great role in influencing the hydrological cycle. In this study, decadal LULC maps of 1985, 1995, 2005 and predicted-2025 of the Subarnarekha, Brahmani, Baitarani, Mahanadi and Nagavali River basins of eastern India were analyzed in the framework of the variable infiltration capacity (VIC) macro scale hydrologic model to estimate their relative consequences. The model simulation showed a decrease in ET with 0.0276% during 1985–1995, but a slight increase with 0.0097% during 1995–2005. Conversely, runoff and base flow showed an overall increasing trend with 0.0319 and 0.0041% respectively during 1985–1995. In response to the predicted LULC in 2025, the VIC model simulation estimated reduction of ET with 0.0851% with an increase of runoff by 0.051%. Among the vegetation parameters, leaf area index (LAI) emerged as the most sensitive one to alter the simulated water balance. LULC alterations via deforestation, urbanization, cropland expansions led to reduced canopy cover for interception and transpiration that in turn contributed to overall decrease in ET and increase in runoff and base flow. This study reiterates changes in the hydrology due to LULCC, thereby providing useful inputs for integrated water resources management in the principle of sustained ecology. 相似文献