全文获取类型
收费全文 | 184篇 |
免费 | 2篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 23篇 |
地球物理 | 40篇 |
地质学 | 87篇 |
海洋学 | 8篇 |
天文学 | 20篇 |
自然地理 | 3篇 |
出版年
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 10篇 |
2012年 | 9篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 5篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有189条查询结果,搜索用时 15 毫秒
71.
Continental weathering plays a dominant role in regulating the global carbon cycle, soil chemistry and nutrient supply to oceans. The CO2-mediated silicate weathering acts as a major CO2 sink, whereas sulphuric acid-mediated carbonate dissolution releases CO2 to the atmosphere–ocean system. In this study, dissolved major ions and silica concentrations of two tropical (Damodar and Subarnarekha) river systems from India have been measured to constrain the type and rate of chemical weathering for these basins. The total dissolved solids (TDS) of these rivers, a measure of total solute supply from all possible sources, are about 2–3 times higher than that of the global average for rivers. Mass balance calculations involving inverse modelling estimate that 63 ± 11% of total cations are derived from rock weathering, of which 27 ± 7% of cations are supplied through silicate weathering. The sulphide-S concentrations are estimated by comparing the water chemistry of these two rivers with that of a nearby river (Brahmani) with similar lithology but no signatures of sulphide oxidation. The outflows of Damodar and Subarnarekha rivers receive 17% and 55% of SO4 through sulphide oxidation, respectively. The sulphide oxidation fluxes from the ore mining areas, such as upper Damodar (0.52 × 109 mol/yr) and lower Subarnarekha (0.66 × 109 mol/yr) basins, are disproportionally (~9 times) higher compared to their fractional areal coverage to the global drainage area. The corresponding CO2 release rate (2.84 × 104 mol/km2/yr) for the Damodar basin is lower by five times than its CO2 uptake rate (1.38 × 105 mol/km2/yr). The outcomes of this study underscore the dominance of sulphide oxidation in controlling the dissolved chemical (cationic and sulphur) fluxes. 相似文献
72.
Prantik Mandal 《Journal of Asian Earth Sciences》2011,40(1):150-161
A high-resolution passive seismic experiment in the Kachchh rift zone of the western India has produced an excellent dataset of several thousands teleseismic events. From this network, 500 good teleseismic events recorded at 14 mobile broadband sites are used to estimate receiver functions (for the 30–310° back-azimuth ranges), which show a positive phase at 4.5–6.1 s delay time and a strong negative phase at 8.0–11.0 s. These phases have been modeled by a velocity increase at Moho (i.e. 34–43 km) and a velocity decrease at 62–92 km depth. The estimation of crustal and lithospheric thicknesses using the inversion of stacked radial receiver functions led to the delineation of a marked thinning of 3–7 km in crustal thickness and 6–14 km in lithospheric thickness beneath the central rift zone relative to the surrounding un-rifted parts of the Kachchh rift zone. On an average, the Kachchh region is characterized by a thin lithosphere of 75.9 ± 5.9 km. The marked velocity decrease associated with the lithosphere–asthenoshere boundary (LAB), observed over an area of 120 km × 80 km, and the isotropic study of xenoliths from Kachchh provides evidence for local asthenospheric updoming with pockets of partial melts of CO2 rich lherzolite beneath the Kachchh seismic zone that might have caused by rifting episode (at 88 Ma) and the associated Deccan thermal-plume interaction (at 65 Ma) episodes. Thus, the coincidence of the area of the major aftershock activity and the Moho as well as asthenospheric upwarping beneath the central Kachchh rift zone suggests that these pockets of CO2-rich lherzolite partial melts could perhaps provide a high input of volatiles containing CO2 into the lower crust, which might contribute significantly in the seismo-genesis of continued aftershock activity in the region. It is also inferred that large stresses in the denser and stronger lower crust (at 14–34 km depths) induced by ongoing Banni upliftment, crustal intrusive, marked lateral variation in crustal thickness and related sub-crustal thermal anomaly play a key role in nucleating the lower crustal earthquakes beneath the Kachchh seismic zone. 相似文献
73.
Pavan Kumar Haroon Sajjad Bismay Ranjan Tripathy Raihan Ahmed Vinay Prasad Mandal 《Natural Hazards》2018,90(2):693-704
Dynamic and vigorous top soil is the source for healthy flora, fauna, and humans, and soil organic matters are the underpinning for healthy and productive soils. Organic components in the soil play significant role in stimulating soil productivity processes and vegetation development. This article deals with the scientific demand for estimating soil organic carbon (SOC) in forest using geospatial techniques. We assessed distribution of SOC using field and satellite data in Sariska Tiger Reserve located in the Aravalli Hill Range, India. This study utilized the visible and near-infrared reflectance data of Sentinel-2A satellite. Three predictor variables namely Normalized Difference Vegetation Index, Soil Adjusted Vegetation Index, and Renormalized Difference Vegetation Index were derived to examine the relationship between soil and SOC and to identify the biophysical characteristic of soil. Relationship between SOC (ground and predicted) and leaf area index (LAI) measured through satellite data was examined through regression analysis. Coefficient of correlation (R 2) was found to be 0.95 (p value < 0.05) for predicted SOC and satellite measured LAI. Thus, LAI can effectively be used for extracting SOC using remote sensing data. Soil organic carbon stock map generated through Kriging model for Landsat 8 OLI data demonstrated variation in spatial SOC stocks distribution. The model with 89% accuracy has proved to be an effective tool for predicting spatial distribution of SOC stocks in the study area. Thus, optical remote sensing data have immense potential for predicting SOC at larger scale. 相似文献
74.
In the eastern part of the Indian shield,late PaleozoiceMesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt(EGMB)and amphibolite facies rocks of the Rengali Province.At present,the northern part of the basin experiences periodic seismicity by reactivation of faults located both within the basin,and in the Rengali Province to the north.Detailed gravity data collected across the basin show that Bouguer anomalies decrease from the EGMB(wt15 mGal),through the basin(w 10 mGal),into the Rengali Province(w 15 mGal).The data are consistent with the reportedly uncompensated nature of the EGMB,and indicate that the crust below the Rengali Province has a cratonic gravity signature.The contact between the two domains with distinct sub-surface structure,inferred from gravity data,coincides with the North Orissa Boundary Fault(NOBF)that defnes the northern boundary of the Talchir Basin.Post-Gondwana faults are also localized along the northern margin of the basin,and present-day seismic tremors also have epicenters close to the NOBF.This indicates that the NOBF was formed by reactivation of a Neoproterozoic terrane boundary,and continues to be susceptible to seismic activity even at the present-day. 相似文献
75.
We present the estimated source parameters from SH-wave spectral modeling of selected 463 aftershocks (2002–06) of the 26 January 2001 Bhuj earthquake, the well-recorded largest continental intraplate earthquake. The estimated seismic moment (Mo), corner frequency (fc), source radius (r) and stress drop (Δσ) for aftershocks of moment magnitude 1.7 to 5.6 range from 3.55×1011 to 2.84×1017 N-m, 1.3 to 11.83 Hz, 107 to 1515 m and 0.13 to 26.7 MPa, respectively, while the errors in fc and Δσ are found to be 1.1 Hz and 1.1 MPa, respectively. We also notice that the near surface attenuation factor (k) values vary from 0.02 to 0.03. Our estimates reveal that the stress drop values show more scatter (Mo0.5 to 1 is proportional to Δσ) toward the larger Mo values (≥1014.5 N-m), while they show a more systematic nature (Mo3 is proportional to Δσ) for smaller Mo values (<1014.5 N-m), which can be explained as a consequence of a nearly constant rupture radius for smaller aftershocks in the region. The large stress drops (= 10 MPa) associated with events on the north Wagad fault (at 15–30 km depth) and Gedi fault (at 3–15 km depth) can be attributed to the large stress developed at hypocentral depths as a result of high fluid pressure and the presence of mafic intrusive bodies beneath these two fault zones. 相似文献
76.
Salt affected soils are characterized by variable distribution and dynamic nature. Based on Landsat data from 1986/1987 supported by ground truth, salt affected soil maps were prepared at 1:250,000 scale for 14 states and a union territory (UT). A map legend was evolved that described the nature, degree and extent of salt affected soils suitable for varied physiographic and agroclimatic regions of the country. Fifteen categories of salt affected soil were identified for the entire country. These were merged to two categories – saline and sodic – for management purposes. Digitized maps were developed in a geographical information system (GIS) depicting salt affected areas of the country. An area of 6.73 million ha of salt affected soils was estimated for the entire country. State-wise estimates showed that this extensive area is distributed over the Gangetic plain of Uttar Pradesh; the arid and semiarid regions of Gujarat and the peninsular plains of Maharashtra state. A significant area is also located in the coastal region covering seven states. The salt affected soils are primarily saline in deltaic (C), coastal (D) and mud flats/mangrove swamps (G) and sodic in alluvial (A), aeofluvial/aeolian/arid (B) and peninsular (F) plains. The distribution of salt affected soils in agroclimatic zones (ACZs) showed occurrence in Gujarat plain, East Coast plains, Upper-Gangetic plain, Trans-Gangetic plain, Central Plateau, Lower-Gangetic plain and Southern Plateau of the country. 相似文献
77.
Sanhita Majumdar Pijush Kanti Mandal Sudip Kumar Das Rabindranath Majumdar 《洁净——土壤、空气、水》2013,41(3):291-297
Carbon bearing materials derived from rice husk (RH) have long been recognized as sorbents for diverse chemicals – both organic and inorganic. This work presents an overview of studies demonstrating a single step process of carbonization of chemically pretreated RH to produce metal impregnated silica‐carbon char designated as silicarbon materials that can be utilized in sorbing out water‐borne organic and inorganic hazardous substances (such as phenol, hexavalent chromium, fluoride, and arsenic) and air‐borne volatile organic chemicals (such as acetone, chloroform, benzene, and pyridine). The metal‐impregnated silicarbon solids derived from RH appear to constitute renewable, low‐cost, user‐friendly, and efficient materials for control systems for indoor air contamination and for industrial as well as non‐industrial hazardous aqueous pollution. 相似文献
78.
79.
Glas H. Jonckheere M. Mandal A. James-Williamson S. De Maeyer P. Deruyter G. 《Natural Hazards》2017,88(3):1867-1891
Natural Hazards - Flood risk assessments and damage estimations form integral parts of the disaster risk management in Jamaica, owing its vulnerability to hydrometeorological hazards. Although... 相似文献
80.
Magnetized accretion flows around black holes which include standing or oscillating shock waves can produce very realistic
spectrum till a few MeV. These shocks accelerate hot electrons which produce power-law spectrum. The post-shock region intercepts
soft-photons from an external source, namely, a Keplerian disk and also from distributed sources such as the synchrotron photons
emitted from thermal and non-thermal electrons originated in the pre-shock and post-shock flow. These photons are inverse
Comptonized by the thermal and the non-thermal electrons present in the CENBOL region. Computations show that the emitted
radiation is extended till a few MeV. We include the bulk motion Comptonization as well and discuss its importance vis-a-vis
the power-law spectrum produced by non-thermal electrons.
相似文献