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21.
Rubber tappers promoted extractive reserves as a sustainable alternative to forest destruction in the Brazilian Amazon. However, the significance of rubber tapping itself has declined since the creation of extractive reserves, which raises questions about the contemporary cultural content of the rubber tapper identity. This paper therefore evaluates rubber tapper identity, using the case of the Chico Mendes Extractive Reserve (CMER) in Acre, Brazil. We first draw on household survey data from the CMER to construct a statistical model of who self-identifies as a rubber tapper. The model shows that socio-economic background, household assets, institutional context, and knowledge of the CMER’s management plan are relevant to understanding rubber tapper self-identification, but not resource management practices, including rubber tapping itself. We therefore pursue qualitative analysis of key informant interviews to better apprehend contemporary understandings of the “rubber tapper” identity, particularly in light of recent shifts in livelihoods from rubber tapping toward cattle ranching. The qualitative analysis shows that there are now several different foundations for self-identifying as a “rubber tapper,” and that there are disagreements concerning the acceptability of cattle ranching among “rubber tappers.” These findings bear implications for research on the relationship of livelihood-based identities with resource management practices and environmental change, as well as public policies that seek to reconcile regional development with forest conservation.  相似文献   
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This paper examines a seemingly anomalous situation in southern Brazil where the dunefields on Santa Catarina Island (e.g. Joaquina Beach) migrate to the NNW, almost completely the opposite direction (c. 160) to the dunefields immediately to the south (e.g. Pinheira Beach), and some much further to the north (e.g. Cabo Frio) which migrate to the SSW. A variety of mechanisms are examined to explain the differences in dunefield migration including grain size variations, topographic effects on local winds, shoreline orientation, and regional wind field changes. The mean grain sizes of the two beaches, Pinheira and Joaquina, are not sufficiently different to restrict aeolian sediment transport in either place, nor to account for a lack of transport from the NNE to the SSW in the case of Joaquina. Some topographic steering of the wind is likely but could not account for the long‐term average difference in migration trends of the island dunefields compared to the mainland dunefields. While the orientation of the shoreline to prevailing winds is an important control on beach and dune sediment transport, it is not the dominant controlling mechanism. An analysis of the regional wind patterns demonstrates that there is a major shift in the regional wind field near the island such that the dominant island winds blow from the SW/SSW while those further south blow from the NE. It is concluded that this is the predominant reason for the divergence in the direction of migration of the dunefields. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
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Due to the severity related to extreme flood events, recent efforts have focused on the development of reliable methods for design flood estimation. Historical streamflow series correspond to the most reliable information source for such estimation; however, they have temporal and spatial limitations that may be minimized by means of regional flood frequency analysis (RFFA). Several studies have emphasized that the identification of hydrologically homogeneous regions is the most important and challenging step in an RFFA. This study aims to identify state‐of‐the‐art clustering techniques (e.g., K ‐means, partition around medoids, fuzzy C‐means, K ‐harmonic means, and genetic K ‐means) with potential to form hydrologically homogeneous regions for flood regionalization in Southern Brazil. The applicability of some probability density function, such as generalized extreme value, generalized logistic, generalized normal, and Pearson type 3, was evaluated based on the regions formed. Among all the 15 possible combinations of the aforementioned clustering techniques and the Euclidian, Mahalanobis, and Manhattan distance measures, the five best were selected. Several watersheds' physiographic and climatological attributes were chosen to derive multiple regression equations for all the combinations. The accuracy of the equations was quantified with respect to adjusted coefficient of determination, root mean square error, and Nash–Sutcliffe coefficient, whereas, a cross‐validation procedure was applied to check their reliability. It was concluded that reliable results were obtained when using robust clustering techniques based on fuzzy logic (e.g., K ‐harmonic means), which have not been commonly used in RFFA. Furthermore, the probability density functions were capable of representing the regional annual maximum streamflows. Drainage area, main river length, and mean altitude of the watershed were the most recurrent attributes for modelling of mean annual maximum streamflow. Finally, an integration of all the five best combinations stands out as a robust, reliable, and simple tool for estimation of design floods.  相似文献   
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Ocean Dynamics - In numerical ocean modeling, dynamical downscaling is the approach consisting in generating high-resolution regional simulations exploiting the information from coarser resolution...  相似文献   
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The Niayes of Senegal are sahelian interdunal fens, that hosted an azonal subguinean vegetation during the Holocene thanks to the availability of fresh groundwater despite contrasted climatic conditions. Exploratory scenario-based modeling of the zonal hydrogeology has been conducted for different periods with the Cast3M code. The results show that the delay in the onset of humid vegetation ca. 10 ky cal. BP could be ecosystemic and denote a start of the African Humid Period (AHP) ca. 11.5 ky cal. BP. Alternatively, the AHP could have started earlier while its beneficial effects would have been canceled by low sea levels. Vegetation degradation around 7.5 ky cal. BP is shown to have resulted from a climate minoration, that possibly alleviated until 4 ky cal. BP. The rising watertable allowed the degraded forest to persist during that period however. The forest expansion that followed ca. 3.5 ky cal. BP had then clearly a climatic origin. The interpretation of pollens for climate research requires a careful filtering-out of local groundwater availability.  相似文献   
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There is limited knowledge about root morphological differences at the species level. Consequently, plant ecological groups are largely defined on aboveground traits. Our hypothesis was that roots of graminoid species differ in morphological and functional attributes. In field and greenhouse studies, we measured morphological and functional root traits of eight dominant graminoids. Multivariate analyses of root traits arranged species into two groups. Species were unequivocally classified by either discriminant analysis or a taxonomic key. Traits that contributed most to identification were diameter, colour, and branching. Species from one group had large root diameters, more branching, and lower tensile strength, specific length, rate of new root generation, and RGR than the other group. The grouping by root traits matched previous classifications: one group had been described as more xerophytic, less preferred by livestock, and more delayed in phenology than the second group. Our study shows that (1) a set of root morphological traits may be reliably used to recognize species, and (2) root traits reflect the major ecological grouping of species, even when they all belong to the same growth form. For Patagonia and similar sites, our work will open the way to more detailed, specific-level studies on community underground organization.  相似文献   
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