全文获取类型
收费全文 | 151篇 |
免费 | 6篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 19篇 |
地球物理 | 70篇 |
地质学 | 35篇 |
海洋学 | 8篇 |
天文学 | 4篇 |
自然地理 | 18篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 18篇 |
2009年 | 22篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 3篇 |
排序方式: 共有157条查询结果,搜索用时 15 毫秒
131.
David N. Dralle W. Jesse Hahm Daniella M. Rempe Nathaniel J. Karst Sally E. Thompson William E. Dietrich 《水文研究》2018,32(13):1978-1992
The relationship between seasonal catchment water storage and discharge is typically nonunique due to water storage that is not directly hydraulically connected to streams. Hydraulically disconnected water volumes are often ecologically and hydrologically important but cannot be explicitly estimated using current storage–discharge techniques. Here, we propose that discharge is explicitly sensitive to changes in only some fraction of seasonally dynamic storage that we call “direct storage,” whereas the remaining storage (“indirect storage”) varies without directly influencing discharge. We use a coupled mass balance and storage–discharge function approach to partition seasonally dynamic storage between these 2 pools in the Northern California Coast Ranges. We find that indirect storage constitutes the vast majority of dynamic catchment storage, even at the wettest times of the year. Indirect storage exhibits lower variability over the course of the wet season (and in successive winter periods) than does direct storage. Predicted indirect storage volumes and dynamics match field observations. Comparison of 2 neighbouring field sites reveals that indirect storage volumes can occur as unsaturated storage held under tension in soils and weathered bedrock and as near‐surface saturated storage that remains on hillslopes (and is eventually evapotranspired). Indirect storage volumes (including moisture in the weathered bedrock) may support plant transpiration, and our method indicates that this important water source could be quantified from precipitation and stream discharge records. 相似文献
132.
In this present era of the Anthropocene, human activities affect hydrology and droughts. Quantifying this human influence improves our understanding and builds fundamental knowledge for water resource management. Analysis of observation data is useful in progressing this knowledge as these human activities and feedbacks are intrinsically included. Therefore, here we present an observation-based approach, the upstream–downstream comparison, to quantify changes in hydrological drought downstream of a human activity. We demonstrate this approach in a basin in northern Chile, where a reservoir was introduced. A sensitivity analysis is performed to assess how different choices of drought analysis threshold can affect the results and interpretation. We find that many commonly used choices do not exclude human activities from the threshold and therefore could be underestimating the change detected due to the human influence. The upstream–downstream comparison avoids this through the application of the upstream station threshold rather than the human-influenced downstream station. 相似文献
133.
134.
Sally Thompson Gabriel Katul Alexandra KoningsLuca Ridolfi 《Advances in water resources》2011,34(8):1049-1058
Lateral redistribution of surface water in patchy arid ecosystems has been hypothesized to contribute to the maintenance of vegetation patches through the provision of a water subsidy from bare sites to vegetated sites. Such runon-runoff processes occur during Hortonian runoff events on topographically sloping ground. Surface flow redistribution may also occur on topographically flat ground if the presence of the vegetation patch creates a contrast in infiltration rate, leading to a free-surface gradient in ponded water. The precise dynamics and the eco-hydrologic role of this process has resisted complete theoretical treatment to date. Here the overland flow equations are modified to account for the presence of vegetation situated over a flat surface. The resulting model is solved numerically to determine whether this mechanism could influence the spatial partitioning of water in patchy arid ecosystems. Assumptions made about infiltration processes and overland flow in existing eco-hydrologic models of patchy and patterned arid ecosystems are evaluated in comparison to the solution of the ‘full’ coupled Saint-Venant equations with various infiltration models. The results indicate that the optimization of vegetation spatial patch scales with respect to water redistribution may be determined by the size of the infiltration redistribution length L over which the presence of an infiltration contrast perturbs baseline infiltration behavior. 相似文献
135.
Chad S. Lane Sally P. Horn Kenneth H. Orvis John M. Thomason 《Quaternary Research》2011,75(3):461-470
Climate change during the so-called Little Ice Age (LIA) of the 15th to 19th centuries was once thought to be limited to the high northern latitudes, but increasing evidence reflects significant climate change in the tropics. One of the hypothesized features of LIA climate in the low latitudes is a more southerly mean annual position of the Intertropical Convergence Zone (ITCZ), which produced more arid conditions through much of the northern tropics. High-resolution stable oxygen isotope data and other sedimentary evidence from Laguna de Felipe, located on the Caribbean slope of the Cordillera Central of the Dominican Republic, support the hypothesis that the mean annual position of the ITCZ was displaced significantly southward during much of the LIA. Placed within the context of regional paleoclimate and paleoceanographic records, and reconstructions of global LIA climate, this shift in mean annual ITCZ position appears to have been induced by lower solar insolation and internal dynamical responses of the global climate system. Our results from Hispaniola further emphasize the global nature of LIA climate change and the sensitivity of circum-Caribbean climate conditions to what are hypothesized to be relatively small variations in global energy budgets. 相似文献
136.
Margot L. Hessing-Lewis Sally D. Hacker Bruce A. Menge Steve S. Rumrill 《Estuaries and Coasts》2011,34(6):1169-1181
Land-based eutrophication is often associated with blooms of green macroalgae, resulting in negative impacts on seagrasses.
The generality of this interaction has not been studied in upwelling-influenced estuaries where oceanic nutrients dominate
seasonally. We conducted an observational and experimental study with Zostera marina L. and ulvoid macroalgae across an estuarine gradient in Coos Bay, Oregon. We found a gradient in mean summer macroalgal
biomass from 56.1 g dw 0.25 m−2 at the marine site to 0.3 g dw 0.25 m−2 at the riverine site. Despite large macroalgal blooms at the marine site, eelgrass biomass exhibited no seasonal or interannual
declines. Through experimental manipulations, we found that pulsed additions of macroalgae biomass (+4,000 mL) did not affect
eelgrass in marine areas, but it had negative effects in riverine areas. In upwelling-influenced estuaries, the negative effects
of macroalgal blooms are context dependent, affecting the management of seagrass habitats subject to nutrient inputs from
both land and sea. 相似文献
137.
Charcoal preserved in lake sediments is commonly used to reconstruct past trends in fire occurrence. However, interpretation of the charcoal record is often complicated, as changes in charcoal influx could represent natural shifts in fire regimes associated with changes in climate, changes in vegetation, or changes in patterns of anthropogenic burning. Here we examine sedimentary charcoal records from three lakes on the Caribbean islands of Hispaniola and Puerto Rico: Laguna Saladilla in the Dominican Republic, Lake Miragoane in Haiti, and Laguna Tortuguero in Puerto Rico. All records are based on microscopic charcoal fragments quantified from pollen slides and cover the last 7,000 or more years of the Holocene. We compare charcoal influx values to archeological and palynological evidence of human activity and explore the role of increasing winter insolation over the Holocene in driving increased charcoal deposition beginning ca. 6,000–5,000 cal yr BP. An increase in charcoal influx at Laguna Tortuguero at ca. 5,200 cal yr BP, previously interpreted as a signal of human settlement predating archeological evidence, may instead reflect insolation-driven shifts in winter drying that led to more frequent and possibly more intense natural fires. Decreased charcoal influx around 3,200 cal yr BP may signal human modification of the environment that altered fire frequency and/or intensity. Comparing the records from these three lowland Caribbean sites highlights possible intervals of synchronous, climate-driven burning as distinct from more localized anthropogenic burning. 相似文献
138.
139.
Information included in this summary is based on more detailed reports published in the Bulletin of the Global Volcanism Network,
vol. 34, no. 2, February 2009 (on the Internet at ). Edited by scientists at the Smithsonian, this bulletin includes reports provided by a worldwide network of correspondents.
The reports contain the names and contact information for all sources. Please note that these reports are preliminary and
subject to change as events are studied in more detail. The Global Volcanism Program welcomes further reports of current volcanism,
seismic unrest, monitoring data, and field observations. 相似文献
140.
Information included in this summary is based on more detailed reports published in the Bulletin of the Global Volcanism Network, vol. 34, no. 8, August 2009 (on the Internet at ). Edited by scientists at the Smithsonian, this bulletin includes reports provided by a worldwide network of correspondents.
The reports contain the names and contact information for all sources. Please note that these reports are preliminary and
subject to change as events are studied in more detail. The Global Volcanism Program welcomes further reports of current volcanism,
seismic unrest, monitoring data, and field observations. 相似文献