全文获取类型
收费全文 | 662篇 |
免费 | 41篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 46篇 |
地球物理 | 171篇 |
地质学 | 229篇 |
海洋学 | 78篇 |
天文学 | 52篇 |
综合类 | 2篇 |
自然地理 | 110篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 28篇 |
2017年 | 34篇 |
2016年 | 31篇 |
2015年 | 26篇 |
2014年 | 38篇 |
2013年 | 35篇 |
2012年 | 39篇 |
2011年 | 68篇 |
2010年 | 36篇 |
2009年 | 37篇 |
2008年 | 37篇 |
2007年 | 37篇 |
2006年 | 25篇 |
2005年 | 26篇 |
2004年 | 32篇 |
2003年 | 28篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有707条查询结果,搜索用时 15 毫秒
701.
After wildfire, hillslope and channel erosion produce large amounts of sediment and can contribute significantly to long-term erosion rates. However, pre-erosion high-resolution topographic data (e.g. lidar) is often not available and determining specific contributions from post-fire hillslope and channel erosion is challenging. The impact of post-fire erosion on landscape evolution is demonstrated with Structure from Motion (SfM) Multi-View Stereo (MVS) photogrammetry in a 1 km2 Idaho Batholith catchment burned in the 2016 Pioneer Fire. We use SfM-MVS to quantify post-fire erosion without detailed pre-erosion topography and hillslope transects to improve estimates of rill erosion at adequate spatial scales. Widespread rilling and channel erosion produced a runoff-generated debris-flow following modest precipitation in October 2016. We implemented unmanned aerial vehicle (UAV)-based SfM-MVS to derive a 5 cm resolution digital elevation model (DEM) of the channel scoured by debris-flow. In the absence of cm-resolution pre-erosion topography, a synthetic surface was defined by the debris-flow scour's geomorphic signature and we used a DEM of Difference (DoD) to map and quantify channel erosion. We found 3467 ± 422 m3 was eroded by debris-flow scour. Rill dimensions along hillslope transects and Monte Carlo simulation show rilling eroded ~1100 m3 of sediment and define a volume uncertainty of 29%. The total eroded volume (4600 ± 740 m3) we measured in our study catchment is partitioned into 75% channel erosion and 25% rill erosion, reinforcing the importance of catchment size on erosion process-dominance. The deposit volume from the 2016 event was 5700 ± 1140 m3, indicating ~60% contribution from post-fire channel erosion. Dating of charcoal fragments preserved in stratigraphy at the catchment outlet, and reconstructions of prior deposit volumes provide a record of Holocene fire-related debris-flows at this site; results suggest that episodic wildfire-driven erosion (~6 mm/year) dominate millennial-scale erosion (~5 mm/Ka) at this site. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd. 相似文献
702.
This article introduces an important, but overlooked, actor—the research associate—into methodological discussions about the production of knowledge. We use the term research associate (rather than assistant) to encompass the individuals on whom researchers rely while conducting fieldwork. We seek to avoid the unidirectional hierarchy and power dynamics between researchers and associates, which place the researcher as expert and knowledge producer while obscuring the diversity of roles conducted by field associates. Therefore, throughout this article we examine and destabilize power dynamics and hierarchies and widen the range of what is considered research assistance in the coproduction of knowledge. We also highlight the ways in which geopolitics are written into encounters with ourselves and research associates, encounters that render and reveal the complexities of vulnerability and bodily risk in fieldwork. The goals of this article are threefold: to (1) introduce the influential role of research associates during the production and dissemination of knowledge, (2) situate the work of research associates in both fieldwork and methodological literature, and (3) problematize the invisibility of research associates in academic publications and discuss possible alternatives to how authorship is credited. 相似文献
703.
ABSTRACTThis paper is a broad review of green infrastructure theory and practice relative to urban sustainability and the space for geographers in these discussions. We use examples from various urban sustainability plans to highlight ways in which green infrastructure is being conceptualized and implemented. We explore how geography contributes research on green infrastructure as well as the emerging practices as seen within sustainability plans. We identify four areas in which geographers can influence both green infrastructure theory and practice: 1) scale; 2) mapping distribution; 3) sensitivity to place and locale; and 4) equity and access. We conclude that in these areas geographers have tremendous opportunity contribute more deliberately to sustainable urbanism. 相似文献
704.
ABSTRACTThis essay narrates the ‘slow violence’, or creeping environmental harms taking place within contemporary environmental governance. It centres on a tall, dense and highly flammable introduced pasture species Gamba grass (Andropogon gayanus), which was listed as a weed across north Australian jurisdictions in 2008. Since this time, it has continued to expand its reach across the Northern Territory (NT). With a potential invasion range of over 380,000?sqkm2, this grass is a serious threat to many more-than-human worlds in the north, including Indigenous-led and Indigenous-owned environmental service economies and multimillion-dollar projects engaged in savanna fire management for carbon credits. Drawing upon fieldwork and interviews with a range of public servants, landholders and researchers in the NT between 2015 and 2018, this essay demonstrates how environmental governance is being undermined through specific institutions and practices. Through an ethnographic reading of weed management documents, including several legal permits to grow Gamba grass within the NT’s ‘eradication zone’, this essay narrates the diverse threads of a pressing ‘slow’ disaster. The unfolding story of Gamba grass, we suggest, is instructive for those seeking to understand the present and future of resource extraction or ‘extractivism’ in Australia and elsewhere. 相似文献
705.
Lisa M. Campbell Jennifer J. Silver Noella J. Gray Sue Ranger Annette Broderick Tatum Fisher Matthew H. Godfrey Shannon Gore John Jeffers Corrine Martin Andrew McGowan Peter Richardson Carlos Sasso Lorna Slade Brendan Godley 《Marine Policy》2009
Co-management between local communities and government agencies is promoted as a strategy to improve fisheries management. This paper considers the potential for co-management of sea turtle fisheries within four UK Overseas Territories (OTs) in the Caribbean, and for co-ordinated management among those territories. We focus on fisher incentives for engaging in co-management and on the potential to scale up co-management to a regional level. This paper presents data from Anguilla, British Virgin Islands, Montserrat, and Turks and Caicos Islands, where 110 turtle fishers participated in a socio-economic survey undertaken as part of the ‘Turtles in the UK Overseas Territories in the Caribbean’ project. Based on three established criteria for co-management (perceived crisis in stock, willingness to participate and community cohesion), results suggest that fisher support for co-management exists within each OT, but the extent of support for and views of specific management interventions varies among OTs. The implications of results for co-management in each territory, and for establishing co-ordinated management regimes in the region, are discussed in the context of current debates about the nature of resources and scalar (mis)matches between resource and management regimes. 相似文献
706.
Modelling the circulation and exchange of Kingston Basin and Lake Ontario with FVCOM 总被引:1,自引:0,他引:1
An unstructured grid, finite-volume, 3-dimensional primitive equation, sigma-coordinate terrain following ocean model (FVCOM) has been applied to Lake Ontario to investigate its monthly climatological circulation with a focus on Kingston Basin. Kingston Basin, in the northeastern end of Lake Ontario, sits between the main body of the lake and the outflowing St. Lawrence River and is adjacent to the Bay of Quinte Area of Concern designated by the International Joint Commission. The focus of this study is to use the unstructured model FVCOM to model the mean circulation in the Basin. Results showed that the FVCOM model can take up to 3 years to spin-up from rest for a wind-forced, almost fully enclosed lake model. The model accurately reproduced the current flow field within the main body of the lake and compared favourably to the flow field observed during the International Field Year for the Great Lakes (IFYGL) in Kingston Basin. Transport streamfunction results show that the structure of the flow into Kingston Basin from the main body of the lake changes throughout the year. 相似文献
707.