全文获取类型
收费全文 | 633篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 39篇 |
地球物理 | 146篇 |
地质学 | 204篇 |
海洋学 | 62篇 |
天文学 | 137篇 |
综合类 | 1篇 |
自然地理 | 61篇 |
出版年
2022年 | 4篇 |
2021年 | 15篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 20篇 |
2015年 | 10篇 |
2014年 | 22篇 |
2013年 | 35篇 |
2012年 | 21篇 |
2011年 | 34篇 |
2010年 | 16篇 |
2009年 | 39篇 |
2008年 | 21篇 |
2007年 | 31篇 |
2006年 | 24篇 |
2005年 | 20篇 |
2004年 | 10篇 |
2003年 | 24篇 |
2002年 | 20篇 |
2001年 | 20篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 17篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1971年 | 2篇 |
排序方式: 共有655条查询结果,搜索用时 15 毫秒
651.
Water managers always have had to cope with climate variability. All water management practices are, to some extent, a response to natural hydrologic variability. Climate change poses a different kind of problem. Adaptation to climate change in water resource management will involve using the kinds of practices and activities currently being used. However, it remains unclear whether or not practices and activities designed with historical climate variability will be able to cope with future variability caused by atmospheric warming. This paper examines the question of adaptation to climate change in the context of Canadian water resources management, emphasizing issues in the context of the Great Lakes, an important binational water resource. 相似文献
652.
Arch M. Reid J.L. Warner W.I. Ridley R.W. Brown 《Geochimica et cosmochimica acta》1973,37(4):1011-1030
Glass compositions in the Luna 20 soil indicate a minor contribution of mare rocks and a major contribution of highly feldspathic highland material. Glasses with the composition of Highland basalt (anorthositic gabbro or norite) predominate in a range of highly aluminous glasses.The analyses of minerals in the soil show that the highland rocks have a unique assemblage of minerals that can readily be distinguished from the mineral assemblages of either mare or KREEP basalts. The soils are characterized by abundant anorthitic (An92–99), low-Fe plagioclase. Highly magnesian orthopyroxenes, pigeonites and augites are the most prominent pyroxenes. Unlike mare basalt pyroxenes, clinopyroxenes with intermediate Ca values are not abundant, but extreme iron enrichment towards pyroxferroite does occur. Olivines are more abundant than at other sites and are Mg-rich, low in Ca and Cr. Spinels with compositions approaching MgAl2O4 predominate over pleonastes and chromites. Ilmenite and metal are present but not abundant.These data establish the unique nature of the minerals in the highland soils. The mineral compositions are consistent with derivation from a suite of highly feldspathic rocks in which Highland basalt compositions predominate. Some of the mineral data, particularly from the pyroxenes, are suggestive of surface or near-surface processes, rather than plutonic crystallization. 相似文献
653.
654.
C. Reid Ferring 《Geoarchaeology》1986,1(3):259-274
Rates of fluvial sedimentation exhibit spatial and temporal variability that is important with respect to the study of prehistoric archaeological sites. Sedimentation rates within fluvial basins vary in response to internal dynamics, geomorphic controls, and external factors including climate and tectonics. Fluvial rates of sedimentation may be estimated using sedimentary, pedogenic, biogenic, and radiometric evidence. Holocene rates of sedimentation vary by three orders of magnitude, as shown by radiometric data from numerous localities in North America. Sedimentation rates define rates of matrix accumulation in archaeological sites. These act as controls on site construction and site modification. Artifact densities, spatial patterning, and preservation are all conditioned by rates of matrix accumulation. These dimensions of prehistoric sites are critical to the evaluation of variability within and between archaeological sites and to the study of past settlement/subsistence systems. 相似文献
655.
Louise Best Alexander R. Simms Martin Brader Jerry Lloyd Juliet Sefton Ian Shennan 《第四纪科学杂志》2022,37(1):59-70
New relative sea-level (RSL) data constrain the timing and magnitude of RSL changes in the southern Isle of Skye following the Last Glacial Maximum (LGM). We identify a marine limit at ~23 m OD, indicating RSL ~20 m above present c. 15.1 ka. Isolation basin data, supported by terrestrial and marine limiting dates, record an RSL fall to 11.59 m above present by c. 14.2 ka. This RSL fall occurs across the time of global Meltwater Pulse 1A, supporting recent research on the sources of ice melting. Our new data also help to resolve some of the chronological issues within the existing Isle of Skye RSL record and provide details of the sub-Arctic marine environment associated with the transition into Devensian Lateglacial climate at c. 14.5 k cal a bp , and the timing of changes in response to the Loch Lomond Stadial climate. Glacio-isostatic adjustment (GIA) model predictions of RSL deviate from the RSL constraints and reflect uncertainties in local and global ice models used within the GIA models. An empirical RSL curve provides a target for future research. 相似文献