全文获取类型
收费全文 | 180篇 |
免费 | 6篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 36篇 |
大气科学 | 14篇 |
地球物理 | 35篇 |
地质学 | 71篇 |
海洋学 | 4篇 |
天文学 | 25篇 |
综合类 | 1篇 |
自然地理 | 5篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 20篇 |
2012年 | 9篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 4篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 7篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1991年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 2篇 |
1962年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有191条查询结果,搜索用时 15 毫秒
21.
Hemant Balwant Wakode Dibyendu Dutta V. R. Desai Klaus Baier Rafig Azzam 《Arabian Journal of Geosciences》2013,6(2):395-408
Geographical Information System (GIS) have proved to be an efficient tool in the delineation of drainage pattern for water resources management and its planning. In this study, GIS and image processing techniques have been adopted for the identification of morphological features and analyzing the properties of the upper catchment of Kosi River. The basin area includes the high-altitude Himalayan Mountains, including Mount Everest and Kanchenjunga peaks. This basin is the main contributing area for devastating floods in 2008 in the Bihar state of India. The catchment can be divided into three sub-catchments, namely, Arun, Sunkosi, and Tamur. A morphometric analysis shows the nature of drainage in the upper catchment of Kosi River and some causes behind the high-intensity floods by comparing the properties of these three sub-catchments. It shows that the highest-order drains are present in both Arun and Sunkosi and the length of the first-order drains is very high (6,088 km) due to the absence of vegetation and also due to the barren/rocky surface which has tremendous potential to generate runoff. Due to highest mean channel gradient in Tamur sub-basin compared to others, it has the highest flow kinetic velocity. Also, the results show that the Arun sub-catchment has the highest potential to contribute runoff and sediment. One of the major causes behind the high intensity of floods is that the sub-catchments Arun and Sunkosi have a nearly equal time of concentration, so they contribute their peak floods at the same time and hence double the intensity of floods. 相似文献
22.
P. Kotoky M. K. Dutta R. Goswami G. C. Borah 《Journal of the Geological Society of India》2011,78(2):175-183
The bank sediments along the extremely meandered Dhansiri River channel, a south bank tributary of the mighty Brahmaputra
River, with erosion potentiality have been investigated to evaluate its certain geotechnical characteristics. The study has
shown that the bank sediments are basically composed of CL and ML types of soil. These types of sediments are very much prone
to liquefaction which in turn related to erosion susceptibility. The bank stability analysis has differentiated the studied
stretch into unstable, at risk and stable zones. Most of the erosion affected zones along the channel reach under study are
located within the unstable or at risk zones. The field study around Butalikhowa, Barguriagaon, Golaghat and Duchmuagaon areas
along the channel with active erosion activity has supported our contention and practical utility of the present study. It
is expected that such type of study will help in providing certain inevitable baseline information for various channel management
practices for this extremely flood prone areas of Northeast India. 相似文献
23.
24.
Arpita Sharma Ananya Saikia Puja Khare D K Dutta B P Baruah 《Journal of Earth System Science》2014,123(6):1439-1449
In Part 1 of the present investigation, 37 representative Eocene coal samples of Meghalaya, India were analyzed and their physico-chemical characteristics and the major oxides and minerals present in ash samples were studied for assessing the genesis of these coals. Various statistical tools were also applied to study their genesis. The datasets from Part 1 used in this investigation (Part 2) show the contribution of major oxides towards ash fusion temperatures (AFTs). The regression analysis of high temperature ash (HTA) composition and initial deformation temperature (IDT) show a definite increasing or decreasing trend, which has been used to determine the predictive indices for slagging, fouling, and abrasion propensities during combustion practices. The increase or decrease of IDT is influenced by the increase of Fe2O3, Al2O3, SiO2, and CaO, respectively. Detrital-authigenic index (DAI) calculated from the ash composition and its relation with AFT indicates Sialoferric nature of these coals. The correlation analysis, Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA) were used to study the possible fouling, slagging, and abrasion potentials in boilers during the coal combustion processes. A positive relationship between slagging and heating values of the coal has been found in this study. 相似文献
25.
Thermal metamorphism of the Arunachal Himalaya, India: Raman thermometry and thermochronological constraints on the tectono-thermal evolution 总被引:1,自引:0,他引:1
George Mathew Sharmistha De Sarkar Kanchan Pande Suryendu Dutta Shakir Ali Apritam Rai Shilpa Netrawali 《International Journal of Earth Sciences》2013,102(7):1911-1936
Determination of the peak thermal condition is vital in order to understand tectono-thermal evolution of the Himalayan belt. The Lesser Himalayan Sequence (LHS) in the Western Arunachal Pradesh, being rich in carbonaceous material (CM), facilitates the determination of peak metamorphic temperature based on Raman spectroscopy of carbonaceous material (RSCM). In this study, we have used RSCM method of Beyssac et al. (J Metamorph Geol 20:859–871, 2002a) and Rahl et al. (Earth Planet Sci Lett 240:339–354, 2005) to estimate the thermal history of LHS and Siwalik foreland from the western Arunachal Pradesh. The study indicates that the temperature of 700–800 °C in the Greater Himalayan Sequence (GHS) decreases to 650–700 °C in the main central thrust zone (MCTZ) and decreases further to <200 °C in the Mio-Pliocene sequence of Siwaliks. The work demonstrates greater reliability of Rahl et al.’s (Earth Planet Sci Lett 240:339–354, 2005) RSCM method for temperatures >600 and <340 °C. We show that the higher and lower zones of Bomdila Gneiss (BG) experienced temperature of ~600 °C and exhumed at different stages along the Bomdila Thrust (BT) and Upper Main Boundary Thrust (U.MBT). Pyrolysis analysis of the CM together with the Fission Track ages from upper Siwaliks corroborates the RSCM thermometry estimate of ~240 °C. The results indicate that the Permian sequence north of Lower MBT was deposited at greater depths (>12 km) than the upper Siwalik sediments to its south at depths <8 km before they were exhumed. The 40Ar/39Ar ages suggest that the upper zones of Se La evolved ~13–15 Ma. The middle zone exhumed at ~11 Ma and lower zone close to ~8 Ma indicating erosional unroofing of the MCT sheet. The footwall of MCTZ cooled between 6 and 8 Ma. Analyses of P–T path imply that LHS between MCT and U.MBT zone falls within the kyanite stability field with near isobaric condition. At higher structural level, the temperatures increase gradually with P–T conditions in the sillimanite stability field. The near isothermal (700–800 °C) condition in the GHS, isobaric condition in the MCTZ together with T–t path evidence of GHS that experienced relatively longer duration of near peak temperatures and rapid cooling towards MCTZ, compares the evolution of GHS and inverted metamorphic gradient closely to channel flow predictions. 相似文献
26.
Subhas Dutta 《Pure and Applied Geophysics》1962,52(1):20-26
Summary The possibility of propagation of Rayleigh waves in a transversely isotropic medium resting on (i) a rigid base and (ii) a yielding base has been studied in this paper. In the former case the relation between the wave velocity and ratio of wave length to thickness has been found and in the latter case the frequency equation and its possible solutions are obtained. 相似文献
27.
Evolution of a homogeneous, isotropic Universe with flat geometry filled with a viscous fluid is investigated in presence
of a variable cosmological Λ. A non-singular solution leading to a variable deceleration parameter is obtained which reduces
to the solution of Murphy in the ‘no Λ limit’ and to the recent solution of Vishwakarma in the context of ‘a Machian model
of dark energy’ in the ‘no viscosity’ limit. 相似文献
28.
Having recognized that it is the tropospheric temperature (TT) gradient rather than the land–ocean surface temperature gradient that drives the Indian monsoon, a new mechanism of El Niño/Southern Oscillation (ENSO) monsoon teleconnection has been unveiled in which the ENSO influences the Indian monsoon by modifying the TT gradient over the region. Here we show that equatorial Pacific coralline oxygen isotopes reflect TT gradient variability over the Indian monsoon region and are strongly correlated to monsoon precipitation as well as to the length of the rainy season. Using these relationships we have been able to reconstruct past Indian monsoon rainfall variability of the first half of the 20th century in agreement with the instrumental record. Additionally, an older coral oxygen isotope record has been used to reconstruct seasonally resolved summer monsoon rainfall variability of the latter half of the 17th century, indicating that the average annual rainfall during this period was similar to that during the 20th century. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
29.
Stratigraphy, sedimentology and bulk organic geochemistry of black shales from the Proterozoic Vindhyan Supergroup (central India) 总被引:1,自引:0,他引:1
Four organic-rich shale units of the Proterozoic Vindhyan sedimentary succession have been scanned to reveal their origin
and hydrocarbon potential. The wavy-crinkly nature of the carbonaceous laminae is suggestive of a microbial mat origin of
the shales. These shales are thus different from Phanerozoic black shales which typically exhibit planar laminae. The hydrocarbon
potential of the black shale units has been evaluated by Rock-Eval pyrolysis. Total organic carbon content of many of the
shales exceeds 1%. The meanT
max for the black shales translate to a vitrinite reflectance range of 2.05-2.40% Rm based on standard conversion techniques.
These shales have reached the catagenetic stage near the beginning of anthracite formation. 相似文献
30.
An experimental investigation to characterise soil macroporosity under different land use and land covers of northeast India 总被引:2,自引:0,他引:2
Sangeeta Shougrakpam Rupak Sarkar Subashisa Dutta 《Journal of Earth System Science》2010,119(5):655-674
Saturated macropore flow is the dominant hydrological process in tropical and subtropical hilly watersheds of northeast India.
The process of infiltration into saturated macroporous soils is primarily controlled by size, network, density, connectivity,
saturation of surrounding soil matrix, and depthwise distribution of macropores. To understand the effects of local land use,
land cover and management practices on soil macroporosity, colour dye infiltration experiments were conducted with ten soil
columns (25 × 25 × 50 cm) collected from different watersheds of the region under similar soil and agro-climatic zones. The
sampling sites included two undisturbed forested hillslopes, two conventionally cultivated paddy fields, two forest lands
abandoned after Jhum cultivation, and two paddy fields, one pineapple plot and one banana plot presently under active cultivation
stage of the Jhum cycle. Digital image analyses of the obtained dye patterns showed that the infiltration patterns differed
significantly for different sites with varying land use, land cover, and cultivation practices. Undisturbed forest soils showed
high degree of soil macroporosity throughout the soil profile, paddy fields revealed sealing of macropores at the topsoil
due to hard pan formation, and Jhum cultivated plots showed disconnected subsoil macropores. The important parameters related
to soil macropores such as maximum and average size of macropores, number of active macropores, and depthwise distribution
of macropores were estimated to characterise the soil macroporosity for the sites. These experimentally derived quantitative
data of soil macroporosity can have wide range of applications in the region such as water quality monitoring and groundwater
pollution assessment due to preferential leaching of solutes and pesticides, study of soil structural properties and infiltration
behaviour of soils, investigation of flash floods in rivers, and hydrological modelling of the watersheds. 相似文献