全文获取类型
收费全文 | 196篇 |
免费 | 16篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 23篇 |
地球物理 | 43篇 |
地质学 | 66篇 |
海洋学 | 21篇 |
天文学 | 28篇 |
自然地理 | 29篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 8篇 |
2016年 | 12篇 |
2015年 | 17篇 |
2014年 | 5篇 |
2013年 | 14篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 19篇 |
2009年 | 13篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有215条查询结果,搜索用时 15 毫秒
1.
Cenozoic landscape evolution of the Kruger National Park as derived from cosmogenic nuclide analyses
Christoph Glotzbach Alexander Paape Jussi Baade Bastian Reinwarth Kate Rowntree Jordan Miller 《地学学报》2016,28(5):316-322
In contrast to active tectonic settings, little is known about the potential feedback between surface processes and climate change in tectonically inactive cratonic regions. Here, we studied the driving forces of erosion and landscape evolution in the Kruger National Park in South Africa using cosmogenic nuclide dating. 10Be‐derived catchment‐wide erosion rates (~2 and ~10 mm ka?1) are similar in magnitude to erosion and rock uplift elsewhere in South Africa, suggesting that (1) rock uplift is solely the isostatic response to erosion and (2) the first‐order topography is likely of Cretaceous age. The topographic maturity is promoted by widespread exposure of rocks resistant to erosion. Our data, however, suggest that local variations in rock resistance lead to transient landscape changes, with local increases in relief and erosion rates. 相似文献
2.
An Early Permian glacial diamictite forms a distinctive unit within the Falkland Islands sedimentary succession and two aspects of its significance have recently been serendipitously enhanced. Fossil discoveries in exotic limestone clasts bear on palaeogeography, whilst a series of mineral‐exploration borehole cores have allowed a detailed study of the sedimentary record of deglaciation that followed deposition of the diamictite. Statistical analysis of reflectance and XRF core‐scanning data has identified likely Milankovitch periodicities and enabled tentative time‐scale modelling. The ‘icehouse to greenhouse’ transition appears to have spanned approximately 1.2 million years, with waning cycles of re‐advance superimposed on overall glacial retreat. The new results play into a long‐debated geological paradox: although the Falkland Islands are now proximal to the South Atlantic coastline of South America, their geology bears an uncanny resemblance to that of the Cape Fold Belt and Karoo Basin in South Africa. This puzzled the geological pioneers, but became readily explicable when first continental drift and then plate tectonics were invoked to reconstruct the break‐up of the Gondwana supercontinent—although the details remain controversial. One of the key stratigraphical correlation levels throughout the major fragments of southern Gondwana—South Africa, South America, Antarctica and Australia—is the glacigenic deposit left behind by the extensive, Late Carboniferous to Early Permian regional glaciation; in the Falkland Islands it is designated the Fitzroy Tillite Formation. 相似文献
3.
Plant macrofossils from 38 packrat middens spanning the last ~ 33,000 cal yr BP record vegetation between ~ 650 and 900 m elevation along the eastern escarpment of the Sierra San Pedro Mártir, northern Baja California. The middens span most of the Holocene, with a gap between ~ 4600 and 1800 cal yr BP, but coverage in the Pleistocene is uneven with a larger hiatus between 23,100 and 14,400 cal yr BP. The midden flora is relatively stable from the Pleistocene to Holocene. Exceptions include Pinus californiarum, Juniperus californica and other chaparral elements that were most abundant > 23,100 cal yr BP and declined after 14,400 cal yr BP. Despite being near the chaparral/woodland-desertscrub ecotone during glacial times, the midden assemblages reflect none of the climatic reversals evident in the glacial or marine record, and this is corroborated by a nearby semi-continuous pollen stratigraphy from lake sediments. Regular appearance of C4 grasses and summer-flowering annuals since 13,600 cal yr BP indicates occurrence of summer rainfall equivalent to modern (JAS average of ~ 80–90 mm). This casts doubt on the claim, based on temperature proxies from marine sediments in the Guaymas Basin, that monsoonal development in the northern Gulf and Arizona was delayed until after 6200 cal yr BP. 相似文献
4.
Morgan Gopnik Clare Fieseler Laura Cantral Kate McClellan Linwood Pendleton Larry Crowder 《Marine Policy》2012
From 2009 to 2011, marine spatial planning (MSP) rapidly gained visibility in the United States as a promising ocean management tool. A few small-scale planning efforts were completed in state waters, and the Obama Administration proposed a framework for large-scale regional MSP throughout the U.S. Exclusive Economic Zone. During that same time period, the authors engaged a variety of U.S ocean stakeholders in a series of dialogs with several goals: to share information about what MSP is or could be, to hear stakeholder views and concerns about MSP, and to foster better understanding between those who depend on ocean resources for their livelihood and ocean conservation advocates. The stakeholder meetings were supplemented with several rounds of in-depth interviews and a survey. Despite some predictable areas of conflict, project participants agreed on a number of issues related to stakeholder engagement in MSP: all felt strongly that government planners need to engage outsiders earlier, more often, more meaningfully, and through an open and transparent process. Equally important, the project affirmed the value of bringing unlike parties together at the earliest opportunity to learn, talk, and listen to others with whom they rarely engage. 相似文献
5.
6.
Udy J Gall M Longstaff B Moore K Roelfsema C Spooner DR Albert S 《Marine pollution bulletin》2005,51(1-4):224-238
For the managers of a region as large as the Great Barrier Reef, it is a challenge to develop a cost effective monitoring program, with appropriate temporal and spatial resolution to detect changes in water quality. The current study compares water quality data (phytoplankton abundance and water clarity) from remote sensing with field sampling (continuous underway profiles of water quality and fixed site sampling) at different spatial scales in the Great Barrier Reef north of Mackay (20 degrees S). Five transects (20-30 km long) were conducted from clean oceanic water to the turbid waters adjacent to the mainland. The different data sources demonstrated high correlations when compared on a similar spatial scale (18 fixed sites). However, each data source also contributed unique information that could not be obtained by the other techniques. A combination of remote sensing, underway sampling and fixed stations will deliver the best spatial and temporal monitoring of water quality in the Great Barrier Reef. 相似文献
7.
8.
9.
The assessment of sustainable development is a relatively recent advent in policy and the evaluation of industry structural adjustments. Although the elements of economic and environmental assessment have been relatively well developed and accepted, the effective inclusion of ‘social’ aspects in assessments of sustainable development are still being grappled with. 相似文献
10.
Kate A. Berry Nancy L. Markee Nanci Fowler Gary R. Giewat 《The Professional geographer》2000,52(1):93-105
The paper examines how rural and urban are interpreted and applied to counties in eleven states in the western United States. After reviewing various conceptual approaches, we turn to a three‐part analysis of county commissioners' perceptions and census data to identify characteristics associated with urban‐ness and rurality. The analysis involves comparing qualitative and quantitative survey and interview data, using a multiple regression analysis to correlate census variables with commissioners' perceptions of their home counties, and using cluster analysis techniques on census variables to identify patterns and unevenness in rurality and urbanness. Three characteristics mentioned by the widest range of commissioners and found to be statistically significant in the regression analysis were population concentration, total population, and the agricultural land base. Population concentration, in particular, was identified most frequently by interviewees as the single most important variable in characterizing an urban county and had the most meaningful contribution to predicting commissioners' perceptions of their home counties in the regression analysis. The cluster analysis identified five county types: largest urban centers, growing regional hubs, high growth rural, dispersed rural, and stable rural agriculture. These county types were widely distributed, reflecting the spatial unevenness of macroscale processes operating across eleven western states. 相似文献