全文获取类型
收费全文 | 88篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 2篇 |
地球物理 | 7篇 |
地质学 | 37篇 |
海洋学 | 15篇 |
天文学 | 10篇 |
自然地理 | 2篇 |
出版年
2018年 | 9篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有89条查询结果,搜索用时 0 毫秒
11.
12.
Johildo Salomo Figueirêdo Barbosa Fernando Alves daSilva Najara Santos Sapucaia Sundaram S. Iyer 《Gondwana Research》1998,1(3-4):343-356
New petrological and geochemical characteristics of the Brejtes region, situated in the south of Bahia, Brazil are discussed. The region forms a part of the most important and extensive granulite facies terrain in Brazil of Archean/Paleoproterozoic age. Five groups of rock types all equilibrated in the granulite facies are identified in this region. They are: i) supracrustal and related rocks, ii) undifferentiated granulites, iii) hornblende bearing enderbite-charnockites, iv) hornblende free enderbite-charnockites, v) charnockites. The first group appears to be the oldest in the region as they form enclaves in the 2.9 Ga old undifferentiated granulites. The third and fourth group are enderbite-charnockites, whose protoliths constitute two series of calc-alkaline rocks, one titanium poor (hornblende free) and another titanium rich (hornblende bearing). U/Pb zircon SHRIMP dates indicate ages of formation at 2.81 Ga (hornblende free) and 2.69 Ga (hornblende bearing) for the two groups. The fifth group of rocks have charnockitic affinity and are present in the center of the Brejtes Dome. These rocks are also have calc-alkaline affinity, but show petrographic and geochemical characteristics distinct from those of other groups. Preliminary geochronological investigations by zircon Pb-Pb evaporation method yielded 2.6 Ga and 2.0 Ga for the charnockites from the inner core of the Brejtes Dome. These age data suggest that the circular structure was formed by the re-fusion of the 2.6 Ga old deep crustal material generating younger charnockites at 2.0 Ga. 相似文献
13.
Development of irrigation potential for increasing agricultural production is the main aim of Command Area Development. This involves interaction amongst various factors; the soil, the crop, the climate, the topograpny and others. Water management in Command Area requires careful planning, based upon adequate data regarding soils, land use and topography. It is essential to make the best possible use of the available water without creating waterlogging, salinity and alkalinity problems in the command area. The use of aerial photographs is a well recognized expedient, convenient and economical method of data collection, which appreciably suits the requirement of the survey of Command Areas. As large areas have to be surveyed for data collection, the best way to accomplish this is by taking up survey of command area in different levels: reconnaissance, semi-detailed and detailed. The reconnaissance and semi-detailed survey would enable us to identify problem areas. Detailed survey are needed in these areas for taking up reclamation measures. A case study of soil survey carried out in the Sharda Sahayak Command Area of a part of Hardoi District is given as an example to illustrate the use of aerial photographs for planning of water management practices. 相似文献
14.
S. Fadnavis S. Dhomse S. Ghude U. Iyer P. Buchunde S. Sonbawne P. E. Raj 《International Journal of Environmental Science and Technology》2014,11(2):529-542
Ozone trends in the Upper Troposphere and Lower Stratosphere over the Indian region are investigated using three satellite data sets namely Halogen Occultation Experiment (1993–2005), Stratospheric Aerosol and Gas Experiment (1993–2005) II, and Aura Microwave Limb Sounder (MLS, 2005–2011). Estimated ozone trends using multi-variate regression analysis are compared with trends at two Indian ozonesonde stations (Delhi, 28°N, 77°E and Pune, 18°N, 73°E), and a 3-D Chemical Transport Model (CTM, SLIMCAT) for the 1993–2005 time period. Overall, all the observational data sets and model simulations indicate significant increasing trend in the upper troposphere (0–2.5 %/year). In the lower stratosphere, estimated trends are slightly positive up to 30 mb and are negative between 30 and 10 mb. Increasing trends in the upper troposphere is probably due to increasing trends in the tropospheric ozone precursor gases (e.g. CO, NO x , NMHCs). Here, we argue that these contrasting ozone-trend profiles might be partially responsible for insignificant long-term trends in the tropical total column ozone. On seasonal scale, positive trends are observed during all the seasons in the upper troposphere while structure of trend profile varies in lower stratosphere. Seasonal variations of ozone trends and its linkages with stratospheric intrusions and increasing trends in lightning flashes in the troposphere are also discussed. 相似文献
15.
Indications of an extreme event deposits along the west coast of India: evidences from GPR investigations 总被引:1,自引:1,他引:0
V. J. Loveson A. R. Gujar S. D. Iyer P. Srivastava G. M. Tirodkar R. A. A. Luis 《Environmental Earth Sciences》2014,72(10):4155-4166
The ground-penetrating radar (GPR) was used to trace the subsurface details in the Palshet coastal zone (Maharashtra) as it exhibits an interesting array of geomorphological features. Furthermore, our main goal was to identify and locate features that might have formed during a reported extreme event and its effects on the flow of the nearby Sundri River. Two profiles (8 and 4 m depth) were collected across the beach and along the backshore, respectively. While the 8-m depth profile (west to east; across the beach) indicates a series of coastline regression in this area, the 4-m depth profile along the coastline (north to south) in the backshore zone reveals two significant incidents viz., (1) stages of development of the paleo-channels that indicate the migration of the Sundri River towards south and (2) huge sediment deposits up to 2.5-m thick in the backshore area. The erosional relict surface (~2.5 m depth) was traced along with various spells of sediments that perhaps occurred due to an extreme event. Sand samples were collected from two trial pits along the GPR profiles to understand the sedimentology and mineralogy in the backshore area. These data together with beach profiles and geomorphological maps suggest that the sands were deposited by an extreme event perhaps during the 1854 cyclonic storm. The sands were trapped in suitable geomorphological sites along the Palshet coast and these sand deposits of about 2.5 m thickness forced the River Sundri to shift its course towards the south. This new revelation facilitates a further study that could focus on the nearby coastal areas to document such extreme event deposits and their influence on the geomorphic set-up. 相似文献
16.
V. J. Loveson A. R. Gujar Sridhar D. Iyer P. Udayaganesan R. A. A. Luis S. S. Gaonkar P. Chithrabhanu G. M. Tirodkar A. K. Singhvi 《Natural Hazards》2014,73(3):2089-2106
Consideration of human influences is crucial to understanding the coastal sediment supply and associated shoreline responses prior to undertaking coastal hazard management studies. Observation of the widening of some selected Indian beaches, especially over the last 6 decades, is of significance. From this perspective, Miramar Beach, Goa, India, was studied using three ground-penetrating radar shallow subsurface profiles (4 m depth). Based on a series of depositional siliciclastic packages, six progradational packages were recognised, which were interrupted by sharp erosional boundaries. These erosional boundaries represent transgressive phases of the shoreline migration. It was observed that the shoreline migration is coupled with the deposition and erosion of sediments, and this is supported by the historical admiralty charts. The optically simulated luminescence dating of the sediments collected at the first progradation period reveals that the age corresponds to the years 1952–1957, which also corroborates the information provided by the local populace. In the past 6 decades, the shoreline growth has been rapid because of the heavy sediment influx from the Mandovi River caused by increased mining activities (since the 1950s) in upstream areas. Since the 1950s, the shoreline has prograded rapidly, building a beach from ~40 to ~280 m wide (average rate of 4 m/year) in response to enhanced sediment supply from the Mandovi River created by mining activities upstream. Superimposed on this overall regressive trend is a series of deposition and erosion cycles. Perhaps, if a similar trend continues, then there will possibly be a further widening of the beach in the future. A close monitoring network is needed to understand the causes of the cycles in shoreline position and to predict their future behaviour. The present investigation on the nature of the coastal response to anthropogenic activities in a river basin as well as the role of short-time cycles on shoreline behaviour in the last 6 decades could be an ideal reference study and motivate the search for similar areas along other coastal locations. 相似文献
17.
18.
R. P. Malik A. V. Shanwal H. S. Iyer 《Journal of the Indian Society of Remote Sensing》1984,12(2):59-64
Salinity is creating great problems in the Yamuna Alluvial Plain. State Government is taking steps for reclaiming these lands to increase agricultural production. Impeded drainage, excess canal irrigation, topography parent material, shallow depth and bad quality of ground water are the main factors which are responsible for the genesis of saline soils in the alluvial plains of Haryana. On the arial photographs tonal differences on account of salt concentration in the soil are clearly seen. These differences are aslo associated with physiography and soil conditions which can be easily delineated. The information thus; collected can be used for reclamation of saline soils. 相似文献
19.
Biosorption of heavy metals by a marine bacterium 总被引:1,自引:0,他引:1
Heavy metal chelation property of exopolysaccharide produced by Enterobacter cloaceae, a marine bacterium, isolated from the West Coast of India, is reported in this paper. The exopolysaccharide demonstrated excellent chelating properties with respect to cadmium (65%) followed by copper (20%) and cobalt (8%) at 100 mg/l heavy metal concentration. However, it could not chelate mercury. A comparative study of the percentage biosorption of the above mentioned metals is presented here. 相似文献
20.
S. S. Iyer A. Choudhuri M. B. A. Vasconcellos U. G. Cordani 《Contributions to Mineralogy and Petrology》1984,85(1):95-101
The radioactive element distribution in the Archean granulite facies rocks of Jequié, Brazil, has been determined. The K/Rb ratios show a large spread with majority of the values falling within the normal field (K/Rb<300). The Th/U ratios fall into two groups, one group with values in the range of 1.7 to 2.6, whereas the other group show Th/U values greater than 7 (7 to 25). These distributions can be explained on the basis of the presence of accessory minerals apatite and zircon. The relatively high concentrations of the radioactive and other elements in Jequié granulites probably represents the relict primary geochemical character, little modified during metamorphism. The radiogenic heat production data for the area are calculated and using the measured regional heat flow value from nearby area an estimate of the relative thickness of the continental lithosphere is made using the model developed by Oxburgh (1981). 相似文献