全文获取类型
收费全文 | 886篇 |
免费 | 15篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 31篇 |
地球物理 | 525篇 |
地质学 | 162篇 |
海洋学 | 2篇 |
天文学 | 159篇 |
综合类 | 1篇 |
自然地理 | 14篇 |
出版年
2020年 | 10篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 20篇 |
2015年 | 17篇 |
2014年 | 22篇 |
2013年 | 25篇 |
2012年 | 17篇 |
2011年 | 27篇 |
2010年 | 30篇 |
2009年 | 24篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2005年 | 13篇 |
1999年 | 14篇 |
1997年 | 9篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 22篇 |
1993年 | 13篇 |
1992年 | 21篇 |
1991年 | 13篇 |
1990年 | 18篇 |
1989年 | 23篇 |
1988年 | 21篇 |
1987年 | 22篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 16篇 |
1977年 | 17篇 |
1976年 | 9篇 |
1975年 | 16篇 |
1974年 | 10篇 |
1973年 | 20篇 |
1972年 | 13篇 |
1971年 | 18篇 |
1970年 | 13篇 |
1969年 | 12篇 |
1966年 | 11篇 |
1964年 | 9篇 |
1963年 | 9篇 |
1962年 | 10篇 |
1960年 | 15篇 |
1957年 | 10篇 |
排序方式: 共有905条查询结果,搜索用时 140 毫秒
901.
Bohdan Kříbek Vladimír Majer František Veselovský Imasiku Nyambe 《Journal of Geochemical Exploration》2010
Samples of topsoil together with reference samples of subsurface soil from a depth of 80–90 cm were collected in the central-northern part of the Zambian Copperbelt to distinguish lithogenic sources of metals from anthropogenic contamination of soils caused by fallout of dust from mining operations, flotation ore treatment plants, tailings dams, smelters and slag dumping grounds. The total sulphur, Cu and Co contents were found to be significantly higher in topsoil relative to subsurface soil over a large part of the surveyed area, and Zn, Pb, As and Hg contents showed a definite increase in the close neighbourhood of smelters and in the direction of prevailing winds. This indicates that the increase of these elements in the topsoil is due to anthropogenic activities. The areal extent and degree of anthropogenic contamination of topsoil can be expressed by an enrichment index (EI) based on the average ratio of the actual and median concentrations of the given contaminants. Although the contamination of soil by dust fallout decreases progressively with depth in the soil profile, in areas strongly affected by mining and mineral processing the anthropogenic contamination by sulphur and copper can be traced to a depth of 80–90 cm. In contrast, the concentration of elements such as Cr, Ni, and V, that show a direct correlation with the content of iron in the soils, increases in the subsurface soil relative to the topsoil. This is particularly evident in areas underlain by rocks of the Katanga Supergroup. 相似文献
902.
Richard Přikryl Jiřina Přikrylová Martin Racek Zuzana Weishauptová Kateřina Kreislová 《Environmental Earth Sciences》2017,76(7):290
A carving of the indoor main altar of St. Vitus Cathedral in Prague (Czech Republic) is made of the opuka stone—a clayey–calcareous silicite—which now exhibits the development of decay phenomena such as the formation of salt-laden case-hardened subsurface layer (approx. 150 mm thick), with detachment of the case-hardened layer manifested by blistering and/or flaking. Formation of this gypsum-rich layer is linked to the reaction of components (SO2) from polluted air (both outdoor and indoor) and from the rock itself (calcium ion from calcite). Development of brittle damage in the subsurface layer and underlying stone is interpreted based on the results from previous environmental monitoring in the Cathedral’s interior, which indicated highly fluctuating temperature and humidity, resulting in a hygrothermal stress in the material described by the “double-layer sandwich” model. The sensitivity of the studied stone to the above-mentioned processes is evidenced by its microstructural properties, specifically parameters of the pore spaces which indicate an extremely high susceptibility to damage by the actions of freezing water and/or salt crystallisation. 相似文献
903.
904.
How well can we simulate complex hydro‐geomorphic process chains? The 2012 multi‐lake outburst flood in the Santa Cruz Valley (Cordillera Blanca,Perú)
下载免费PDF全文
![点击此处可从《地球表面变化过程与地形》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Martin Mergili Adam Emmer Anna Juřicová Alejo Cochachin Jan‐Thomas Fischer Christian Huggel Shiva P. Pudasaini 《地球表面变化过程与地形》2018,43(7):1373-1389
Changing high‐mountain environments are characterized by destabilizing ice, rock or debris slopes connected to evolving glacial lakes. Such configurations may lead to potentially devastating sequences of mass movements (process chains or cascades). Computer simulations are supposed to assist in anticipating the possible consequences of such phenomena in order to reduce the losses. The present study explores the potential of the novel computational tool r.avaflow for simulating complex process chains. r.avaflow employs an enhanced version of the Pudasaini ( 2012 ) general two‐phase mass flow model, allowing consideration of the interactions between solid and fluid components of the flow. We back‐calculate an event that occurred in 2012 when a landslide from a moraine slope triggered a multi‐lake outburst flood in the Artizón and Santa Cruz valleys, Cordillera Blanca, Peru, involving four lakes and a substantial amount of entrained debris along the path. The documented and reconstructed flow patterns are reproduced in a largely satisfactory way in the sense of empirical adequacy. However, small variations in the uncertain parameters can fundamentally influence the behaviour of the process chain through threshold effects and positive feedbacks. Forward simulations of possible future cascading events will rely on more comprehensive case and parameter studies, but particularly on the development of appropriate strategies for decision‐making based on uncertain simulation results. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. 相似文献
905.
Diffusion-controlled development of silica-undersaturated domains in felsic granulites of the Bohemian Massif (Variscan belt of Central Europe) 总被引:2,自引:0,他引:2
Lucie Tajčmanová Jiří Konopásek James A. D. Connolly 《Contributions to Mineralogy and Petrology》2007,153(2):237-250
Plagioclase rims around metastable kyanite crystals appear during decompression of high-pressure felsic granulites from the
high-grade internal zone of the Bohemian Massif (Variscan belt of Central Europe). The development of the plagioclase corona
is a manifestation of diffusion-driven transfer of CaO and Na2O from the surrounding matrix and results in isolation of kyanite grains from the quartz- and K-feldspar-bearing matrix. This
process establishes Si-undersaturated conditions along the plagioclase–kyanite interface, which allow crystallization of spinel
during low-pressure metamorphism. The process of the plagioclase rim development is modeled thermodynamically assuming local
equilibrium. The results combined with textural observations enable estimation of equilibration volume and diffusion length
for Na and Ca that extends ∼400–450 and ∼450–550 μm, respectively, around each kyanite crystal. Low estimated bulk diffusion
coefficients suggest that the diffusion rate of Ca and Na is controlled by low diffusivity of Al across the plagioclase rim. 相似文献