全文获取类型
收费全文 | 482篇 |
免费 | 28篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 25篇 |
地球物理 | 143篇 |
地质学 | 188篇 |
海洋学 | 46篇 |
天文学 | 55篇 |
自然地理 | 48篇 |
出版年
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 14篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 21篇 |
2012年 | 15篇 |
2011年 | 33篇 |
2010年 | 19篇 |
2009年 | 27篇 |
2008年 | 21篇 |
2007年 | 18篇 |
2006年 | 26篇 |
2005年 | 17篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 16篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1862年 | 2篇 |
排序方式: 共有514条查询结果,搜索用时 15 毫秒
61.
Variable Grid Method: An Intuitive Approach for Simultaneously Quantifying and Visualizing Spatial Data and Uncertainty 下载免费PDF全文
Efforts to develop applications and methods that effectively quantify and communicate uncertainty associated with spatial data remains a focus within many scientific communities. However, the inherent complexity of uncertainty makes it difficult to define, characterize, and represent. Frequently, the products of spatial and spatio‐temporal data are presented without a clear explanation of the inherent uncertainty underlying the data. As uses and applications for spatial data and their products continues to increase, so does the importance for utilizing reliable approaches to effectively communicate spatial data along with their inherent uncertainties. To address this need, the Variable Grid Method (VGM) was developed as an intuitive approach that simultaneously communicates both spatial patterns and trends and the uncertainty associated with data or their analyses. This article details the VGM approach and demonstrates the utility of the VGM to provide critical information about the relationship between uncertainty and spatial data, necessary to support the increasing utilization of spatial information for a wide range of research and other needs. 相似文献
62.
Dai Aiguo Huang Danqing Rose Brian E. J. Zhu Jian Tian Xiangjun 《Climate Dynamics》2020,54(11):4515-4543
Climate Dynamics - Equilibrium climate sensitivity (ECS) refers to the total global warming caused by an instantaneous doubling of atmospheric CO2 from the pre-industrial level in a climate system.... 相似文献
63.
Globalization,Pacific Islands,and the paradox of resilience 总被引:1,自引:0,他引:1
Matthew Lauer Simon Albert Shankar Aswani Benjamin S. Halpern Luke Campanella Douglas La Rose 《Global Environmental Change》2013,23(1):40-50
On April 2nd, 2007 a 12 m tsunami struck Simbo, a relatively remote island in Western Province, Solomon Islands. Although Simbo's population continues to depend on their own food production and small-scale governance regimes regulate access to resources, the island's way of life over the last century has increasingly been affected by processes associated with globalization. In this context of a rapidly globalizing world, this article examines the island's resilience and vulnerability to the tsunami and the adaptive capacities that enabled the response and recovery. The tsunami completely destroyed two villages and damaged fringing coral reefs, but casualties were low and social–ecological rebound relatively brisk. By combining social science methods (household surveys, focus group and ethnographic interviews) and underwater reef surveys we identify a number of countervailing challenges and opportunities presented by globalization that both nurture and suppress the island's resilience to high amplitude, low-frequency disturbances like tsunamis. Analysis suggests that certain adaptive capacities that sustain general system resilience come at the cost of more vulnerability to low-probability hazards. We discuss how communities undergoing increasingly complex processes of change must negotiate these kinds of trade-offs as they manage resilience at multiple spatial and temporal scales. Understanding the shifting dynamics of resilience may be critical for Pacific Island communities who seek to leverage globalization in their favor as they adapt to current social–ecological change and prepare for future large-scale ecological disturbances. 相似文献
64.
The Last Glacial Maximum in the North Sea Basin: micromorphological evidence of extensive glaciation
Despite a long history of investigation, critical issues regarding the last glacial cycle in northwest Europe remain unresolved. One of these refers to the extent, timing and dynamics of Late Devensian/Weichselian glaciation of the North Sea Basin, and whether the British and Scandinavian ice sheets were confluent at any time during this period. This has been the result of the lack of the detailed sedimentological data required to reconstruct processes and environment of sediments recovered through coring. This study presents the results of seismic, sedimentological and micromorphological evidence used to reconstruct the depositional processes of regionally extensive seismic units across the North Sea Basin. Thin section micromorphology is used here to provide an effective means of discriminating between subglacial and glacimarine sediments from cored samples and deriving process‐based interpretations from sediment cores. On the basis of micromorphology, critical formations from the basin have been reinterpreted, with consequent stratigraphic implications. Within the current stratigraphic understanding of the North Sea Basin, a complex reconstruction is suggested, with a minimum of three major glacial episodes inferred. On at least two occasions during the Weichselian/Devensian, the British and Scandinavian ice sheets were confluent in the central North Sea. Whilst micromorphology can provide much greater confidence in the interpretation of Late Quaternary offshore stratigraphic sequences, it is noted that a much better geochronology is required to resolve key stratigraphic issues between the onshore and offshore stratigraphic records. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
65.
Mark Cable Rains Graham E. Fogg Thomas Harter Randy A. Dahlgren Robert J. Williamson 《水文研究》2006,20(5):1157-1175
Relatively little is known about the role of perched aquifers in hydrological, biogeochemical, and biological processes of vernal pool landscapes. The objectives of this study are to introduce a perched aquifer concept for vernal pool formation and maintenance and to examine the resulting hydrological and biogeochemical phenomena in a representative catchment with three vernal pools connected to one another and to a seasonal stream by swales. A combined hydrometric and geochemical approach was used. Annual rainfall infiltrated but perched on a claypan/duripan, and this perched groundwater flowed downgradient toward the seasonal stream. The upper layer of soil above the claypan/duripan is ~0·6 m in thickness in the uplands and ~0·1 m in thickness in the vernal pools. Some groundwater flowed through the vernal pools when heads in the perched aquifer exceeded ~0·1 m above the claypan/duripan. Perched groundwater discharge accounted for 30–60% of the inflow to the vernal pools during and immediately following storm events. However, most perched groundwater flowed under or around the vernal pools or was recharged by annual rainfall downgradient of the vernal pools. Most of the perched groundwater was discharged to the outlet swale immediately upgradient of the seasonal stream, and most water discharging from the outlet swale to the seasonal stream was perched groundwater that had not flowed through the vernal pools. Therefore, nitrate‐nitrogen concentrations were lower (e.g. 0·17 to 0·39 mg l?1) and dissolved organic carbon concentrations were higher (e.g. 5·97 to 3·24 mg l?1) in vernal pool water than in outlet swale water discharging to the seasonal stream. Though the uplands, vernal pools, and seasonal stream are part of a single surface‐water and perched groundwater system, the vernal pools apparently play a limited role in controlling landscape‐scale water quality. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
66.
F. M. Kerr A. Gouveia R. W. Lee P. K. Patel O. Renner S. J. Rose H. A. Scott J. S. Wark 《Astrophysics and Space Science》2005,298(1-2):171-176
An astrophysically relevant experiment is compared to the output of a multidimensional radiation transfer code in which populations
and radiation are self-consistently treated. Experimental Al Ly α spectra obtained with a very high-resolution spectrometer
are presented as quantitative evidence of dot plasma non-planar expansion. Analysis of these spectra using the code is performed,
in particular examining the effects of velocity gradients in directions other than that of the primary expansion. These calculations
are found to be in good agreement with the experimental results. Usage of the Ly α doublet as a planarity diagnostic is discussed. 相似文献
67.
68.
A field study was conducted using a combination of intrinsic and artificial tracers to estimate travel times and dilution during transport of infiltrate from a reclaimed water infiltration basin to nearby monitoring wells. A major study objective was to validate boric acid enriched in (10)B as an artificial tracer. Basin 10E at the Rio Hondo Spreading Grounds in Whittier, California, was the site of the test. The basin normally receives a mixture of treated municipal waste water, purchased State Project water, and local runoff from the San Gabriel River. Approximately 3.5 kg of (10)B-enriched boric acid was dispersed among 2.05 x 10(5) m(3) of basin water to initiate the experiment. The resultant median delta(11)B in the infiltration basin was -71 per thousand. Prior to tracer addition, the basin water had an intrinsic delta(11)B of +2 per thousand. Local monitoring wells that were used to assess travel times had delta(11)B values of +5 per thousand and +8 per thousand at the time of tracer addition. Analytic results supported an assumption that boron is conserved during ground water transport and that boron enriched in (10)B is a useful artificial tracer. Several intrinsic tracers were used to reinforce the boric acid tracer findings. These included stable isotopes of oxygen (delta(18)O) and hydrogen (deltaD), sulfate concentration, and the boron to chloride ratio. Xenon isotopes, (136)Xe and (124)Xe, also supported boron isotope results. Xenon isotopes were added to the recharge basin as dissolved gases by investigators from the Lawrence Livermore National Laboratory. 相似文献
69.
A proposal for a new scenario framework to support research and assessment in different climate research communities 总被引:1,自引:0,他引:1
Detlef P. van Vuuren Keywan Riahi Richard Moss Jae Edmonds Allison Thomson Nebojsa Nakicenovic Tom Kram Frans Berkhout Rob Swart Anthony Janetos Steven K. Rose Nigel Arnell 《Global Environmental Change》2012,22(1):21-35
In this paper, we propose a scenario framework that could provide a scenario “thread” through the different climate research communities (climate change – vulnerability, impact, and adaptation - and mitigation) in order to support assessment of mitigation and adaptation strategies and climate impacts. The scenario framework is organized around a matrix with two main axes: radiative forcing levels and socio-economic conditions. The radiative forcing levels (and the associated climate signal) are described by the new Representative Concentration Pathways. The second axis, socio-economic developments comprises elements that affect the capacity for mitigation and adaptation, as well as the exposure to climate impacts. The proposed scenarios derived from this framework are limited in number, allow for comparison across various mitigation and adaptation levels, address a range of vulnerability characteristics, provide information across climate forcing and vulnerability states and span a full century time scale. Assessments based on the proposed scenario framework would strengthen cooperation between integrated-assessment modelers, climate modelers and vulnerability, impact and adaptation researchers, and most importantly, facilitate the development of more consistent and comparable research within and across these research communities. 相似文献
70.
Early and Middle Pleistocene landscapes of eastern England 总被引:1,自引:1,他引:0
This paper reviews the pattern of climate and environmental change in eastern England over the period of the Early and Middle Pleistocene, focussing especially upon northern East Anglia. Particular attention is given to the climate and tectonics that have brought about these changes and the distinctive geology, topography and biology that has developed. Throughout, an attempt is made to describe the new models that have been proposed for the Early and Middle Pleistocene of eastern England, and explain the reasons for these changes. The Early Pleistocene experienced relatively high insulation and relatively low magnitude climatic change and is represented primarily by non-climatically forced processes in the form of tidal current- and wave-activity which formed shallow marine deposits. It is possible to recognise a tectonic control in the distribution of deposits of this age because the surface processes do not have the power to remove this signature. The early Middle Pleistocene was dominated by higher magnitude climatic change involving, occasionally, climatic extremes that ranged from permafrost to mediterranean. The landscape at this time was dominated by the behaviour of major rivers (Thames, Bytham, Ancaster) and extensive coastal activity. In the latter part of the early Middle Pleistocene and the Late Middle Pleistocene the climate experienced major changes which resulted in periods of lowland glaciation and short intervals when the climate was warmer than the present. Details of tectonic activity are difficult to identify because they are removed by powerful surface processes, but it is possible to infer uplift focussed on the major interfluves of central England and subsidence in the North Seas basin. In the areas of glaciation the landscape changed radically from an organised terrain dominated by large rivers and extensive shallow coastal zones to complex, with small valleys, disrupted drainage and often discontinuous river, slope and coastal deposits. Likewise the switching off of the North Sea Delta and the opening of the Strait of Dover, separating Britain from continental Europe can be attributed to the onset of lowland glaciation. The case is made that eastern England was glaciated four times during the Middle Pleistocene: during MIS 16, 12, 10 and 6, and attention is given to recent evidence contradicting this model. Over the period of the Middle Pleistocene there is evidence for high biomass production occurring over short intervals coinciding with the climatic optima of MIS 19, 17, 15, 13, 11, and 7c, 7a and during most of these warmer periods, extending back to c. 750 ka (MIS 19/17), there is evidence in the region for the brief appearance of humans. 相似文献