全文获取类型
收费全文 | 56篇 |
免费 | 3篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 6篇 |
地球物理 | 14篇 |
地质学 | 21篇 |
海洋学 | 12篇 |
天文学 | 1篇 |
自然地理 | 2篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 6篇 |
2010年 | 2篇 |
2009年 | 6篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有59条查询结果,搜索用时 15 毫秒
41.
M. Pilar Salvador Sanchis Dino Torri Lorenzo Borselli Rorke Bryan Jean Poesen Marta S. Yañez Cati Cremer 《地球表面变化过程与地形》2009,34(15):2023-2030
Eroding channels can usually be characterized by a power relationship between channel width (W) and channel discharge (Q). This paper examines the WQ relation using a recently developed channel junction approach to extend the validity of the WQ relation and to develop a procedure for estimating the WQ exponent and proportionality coefficient. Rill and gully channel data from the literature, and new data collected in different badland areas and in a few forest mountain streams, are analysed. Analysis shows that the WQ relation for channel width collected in badlands and forests agrees with trends observed for cropland. The exponent increases with increasing channel width in a continuous fashion rather than in a step‐like way and tends to a maximum whose value ranges between 0·5 and 0·6. The proportionality coefficient can be split into two terms, one expressing the case in which an eroding channel can broaden, the other reflecting the difficulties in removing the less erodible clods or rock fragments from the channel bed. Its splitting allows the development of a more correct form of the WQ relation in agreement with modern approaches of channel geometry: one part has the dimension of a discharge and makes the power base dimensionless, while the other brings the dimension of a length, needed for the channel width, into the WQ relation. The interpretation of the two constants is supported by data collected in rainfall‐runoff simulation experiments conducted in the field. Values characterizing the two constants in some environments are also given. Nevertheless the approach is not sufficiently parameterized yet to be of practical use (e.g. in models or for estimating peak discharge in areas where rill channels have formed). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
42.
43.
Asuncion Beamonte Pilar Gargallo Manuel Salvador 《Journal of Geographical Systems》2010,12(2):227-240
In this paper, we extend the Bayesian methodology introduced by Beamonte et al. (Stat Modelling 8:285–311, 2008) for the estimation and comparison of spatio-temporal autoregressive models (STAR) with neighbourhood effects, providing
a more general treatment that uses larger and denser nets for the number of spatial and temporal influential neighbours and
continuous distributions for their smoothing weights. This new treatment also reduces the computational time and the RAM necessities
of the estimation algorithm in Beamonte et al. (Stat Modelling 8:285–311, 2008). The procedure is illustrated by an application to the Zaragoza (Spain) real estate market, improving the goodness of fit
and the outsampling behaviour of the model thanks to a more flexible estimation of the neighbourhood parameters. 相似文献
44.
Alvarado Patricia Christiansen Rodolfo Gregori Salvador Daniel Saez Mauro 《Natural Hazards》2020,102(3):1011-1031
Natural Hazards - The present study has investigated site amplification effects from the analysis of peak ground accelerations (PGA) and spectral accelerations (SA) of the last two major crustal... 相似文献
45.
Stock Evaluation of Three Littoral Echinoid Species on the Catalan Coast North-Western Mediterranean 总被引:2,自引:0,他引:2
Cruz Palacín Xavier Turon Manuel Ballesteros Gonzalo Giribet Salvador López 《Marine Ecology》1998,19(3):163-177
Abstract. We estimated the abundances of the three common littoral echinoid species Paracentrotus lividus, Arbacia lixula and Sphaerechinus granularis in a littoral zone between 0 and 10m depth on the Catalan shores NE Spain. Densities of each species were estimated from a total number of 11 571× 1 m2 sampling units deployed at 152 sites along the 13 zones into which the coast was divided. The surface area available in each of these zones was estimated at the scale of the sampling unit 1 m2 taking into account the fractal dimension of the shore. The stocks individuals > 2cm test diameter of these species for the whole Catalan shore ≅ 300 km, straight-line distance were estimated to be about 279.1 × 106 individuals for P. lividus , 28.9 × 106 individuals for A. lixula and 10.9 × 106 individuals for S. granularis. These sea-urchins are key species in the regulation of algal communities and some of them P. lividus. S. granularis are of commercial interest. This information will provide a tool for the future monitoring and management of this resource, which now faces diverse pressures of human origin. 相似文献
46.
The southeastern beaches and inner shelf of the Buenos Aires coastline are dominated by storms coming from the south and southeast. Erosion is dominant at the coastal cliffs and abrasion platforms, while deposition is extended below the 9-m contour depth. In relation to sand abundance on the inner shelf, there is a northward transition between shelly sand sheets, a fine-sand ribbon field, and sand ridges with oblique megaripples. Side-scan records indicate the selective sorting processes that lead to grain size diminishing to the north, and heavy-mineral enrichment, either at the beach or on the shelf. These storm-induced effects should be considered when evaluating placers on the inner shelf or monitoring the heavy-metal content in sediments. Two-way analyses of variance (ANOVA) tests were used to establish the grain-size effects on heavy-metal analysis. 相似文献
47.
Darío Andrés Giagante Salvador Aliotta Silvia Susana Ginsberg Laura Gabriela Vecchi Jorge Osvaldo Spagnuolo 《Quaternary Research》2011,75(3):614-623
The purpose of this research is to analyze the seismostratigraphic and paleoenvironmental features of an ancient fluvial deposit characterized by the presence of paleochannels and sedimentary structures in Bahía Blanca estuary, Argentina. To this end, high-resolution seismic methods were used. Paleochannels exhibiting v-shaped cuts were found at different topographic positions at the base of this deposit. It was observed that channel silting is indicative of the relative change of river base level and the consequent migration of fluvial tributaries. This alluvial deposit is composed of low compacted fine sand and its middle–upper facies is characterized by the presence of horizontal and discontinuous wavy reflectors. The upper boundary of this deposit is an erosive discontinuity resulting from Holocene sea-level rise during which the mouth of old fluvial courses underwent changes. The deposit was subsequently buried by sandy and clayey silt sediments. The paleodrainage at subbottom indicates that this deposit is associated with an ancient river mouth. Based on the seismostratigraphic and lithological characteristics and the paleochannel structures found in the study area, it can be concluded that the deposit analyzed is an alluvial sequence formed in the period from the Middle-Late Pleistocene to Holocene marine transgression. 相似文献
48.
RésuméÀ la suite d’un violent orage, une lave torrentielle d’un volume supérieur à 100 000 m3 s’est répandue sur le cône de déjection du torrent du Bez, provoquant des dégâts considérables aux infrastructures. Les observations réalisées durant l’événement et les investigations menées dans le bassin versant nous permettent de mieux comprendre le déclenchement de cette lave. Le flot boueux marquant le début de l’événement a été en grande partie alimenté par les ravinements affectant le haut du bassin versant. La lave à blocs qui a suivi s’est nourrie quant à elle des dépôts morainiques recouvrant la rive gauche du torrent, dans la partie inférieure du bassin versant. Au lendemain de la crue, on pouvait observer deux grandes entailles d’une profondeur maximale de 15 m. L’instabilité des berges qui en résultait a alors été rapidement enrayée par d’importants travaux de terrassements et d’enrochements. © Elsevier, Paris 相似文献
49.
Rodríguez Juan Sánchez Salvador García Antonio Blasco Manolo Villalonga Miquel A. 《Earth, Moon, and Planets》2002,90(1-4):185-194
The results from the analysis of the extensive CCD photometry that we haveobtained during the long-term monitoring (from its
discovery until its break-up)of comet C/1999 S4 (linear) are presented here. Our observations showthat the comet did not always
behave as expected: it showed activity ahead oftime and in the end became fainter instead of brighter as it approached perihelion.A
sequence of images and a lightcurve are shown. 相似文献
50.
The Quaternary: its character and definition 总被引:5,自引:0,他引:5
Martin J. Head Philip Gibbard Amos Salvador 《《幕》》2008,31(2):234-238
The Quaternary, is characterised by the development of widespread glaciations in mid-northern latitudes. As a chronostratigraphic term it has attracted vigorous debate. The Quaternao; as accepted by the International Union for Quaternary Research and proposed by the International Commission on Stratigraphy, begins at 2.6 Ma within a 2.8-2.4 Ma interval of profound change in Earth's climate system. 相似文献