全文获取类型
收费全文 | 247篇 |
免费 | 11篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 16篇 |
地球物理 | 57篇 |
地质学 | 89篇 |
海洋学 | 24篇 |
天文学 | 71篇 |
自然地理 | 7篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 17篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 14篇 |
2009年 | 22篇 |
2008年 | 14篇 |
2007年 | 7篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有269条查询结果,搜索用时 93 毫秒
261.
D. S. Sardinha Daniel Marcos Bonotto F. T. da Conceição 《Environmental Earth Sciences》2010,61(5):1025-1036
The aim of this paper was to evaluate the chemical weathering rate at Alto Sorocaba basin, São Paulo State, Brazil, as it is an important parameter on geomorphological characterization of continents. Several tools may be used for such evaluation, and this work compares the results obtained from analytical data involving the uranium concentration, the 234U/238U activity ratio and the major cation concentration for samples of waters, soils, and rocks from that basin. The use of the natural uranium as a tracer in weathering rate rocks studies is advantageous since this element is virtually absent in rainwater and also allows obtaining the dissolution rocks coefficient by the 234U/238U activity ratio. The Alto Sorocaba basin has serious environmental problems in terms of the quality of the rainwater and river waters, and, consequently, the geochemical balance using the main cations presented some difficulties. However, measuring of the weathering rate utilizing the U-isotopes method corresponded to 14 μm/year that allows estimating a time of 72,000 years to weather 1 m of rock at Sorocaba River upstream from Itupararanga Reservoir, under the present climatic conditions. 相似文献
262.
Marcos García-Arias Luis Guillermo Corretgé Antonio Castro 《Mineralogy and Petrology》2010,99(3-4):153-164
Melting experiments on a gneissic protolith using the diamond trap technique produced an accumulation of crystals of biotite in the boundary of the diamond trap. Several hypotheses can be inferred to explain this feature, but textural evidence and calculations of the settling and drag velocities of the crystals suggest a model of extraction of melt due to a pressure gradient inside the capsule as the most likely origin of this biotite layer. This biotite layer and the trapped melt resemble the melanosome and leucosome, respectively, of stromatic metatexite migmatites. The melt extraction model developed is similar to the “filter pressing” model for migmatite formation. The diamond trap technique is a suitable method to develop migmatites experimentally. 相似文献
263.
A new method to determine stress directions using the preferential orientation of plagioclase mechanical twins has been applied to high-temperature mylonitic rocks from the Além Paraíba shear zone, Ribeira fold belt, southeastern Brazil. We have measured the lattice-preferred orientation of plagioclase grains and calculated the orientation of the stress axes possible for the observed twin orientations. The maximum compressive stress direction (σ1), determined for all studied samples, is a function of the mechanical twin orientations of a number of distinct plagioclase populations. The σ1 direction is generally subperpendicular to the (010) plane. The statistical treatment for most of the plagioclase grains examined for each sample shows that σ1 is almost perpendicular to the foliation plane, suggesting a significant coaxial component in the deformation process of these rocks. 相似文献
264.
R. Fraile J. L. Sánchez J. L. de la Madrid A. Castro J. L. Marcos 《Theoretical and Applied Climatology》1999,64(1-2):105-117
Summary Since 1990 the Laboratory for Atmospheric Physics at the University of León has made use of a network of 250 hailpads spread
over an area of 1000 km2 in the province of León (north-western Spain). By the end of 1995, the network had detected 25 hailfalls of more than 15 km2 in area, registered on 13 different days during the summer months.
The 25 hailfalls were precipitated over more than 300 separate hailpads, leaving nearly 40 000 measurable prints. The size
of each hailstone, whose mass and kinetic energy were taken simply as a function of the diameter of the stone was calculated
using the hailpad network. In this way, an estimate has been made of the total quantity of ice which fell in each hailfall
(circa 19 000 metric tons on average, although a figure ten times this was calculated for one particular hailstorm). The spatial
evolution of the physical variables of the hail, determined from each pad, has also been graphically represented.
In addition, the distribution of hailstone sizes has been analysed, and the characteristic distribution parameters calculated.
Although exponential distribution is often used, the Kolmogorov-Smirnov test of goodness-of-fit shows a better fit for gamma
distribution. The information provided by these parameters has been analysed for both distributions, in relation to some specific
variables associated with hail. There is a good correlation between total energy and mass precipitated, but the quantity of
hail per unit area correlates with the total energy or mass of the precipitation only through the area affected. The size
distribution parameters only show good correlations with the maximum hailstone size recorded.
Received October 1, 1998 Revised March 8, 1999 相似文献
265.
Marangoni Gazineu Marinho Pinto Paula Martins Campos Ricardo Gallo Marcos Nicolas Parente Ribeiro Carlos Eduardo 《Ocean Dynamics》2023,73(6):303-315
Ocean Dynamics - Accurate simulations of significant wave height (Hs) are extremely important for the safety of navigation, port operations, and oil and gas exploration. Thus, accurate forecasts of... 相似文献
266.
Fonseca Diego Luiz Marroig Patrícia Cunha Carneiro Juliane Castro Gallo Marcos Nicolás Vinzón Susana Beatriz 《Ocean Dynamics》2019,69(1):51-57
Ocean Dynamics - At the nautical bottom approach, part of the fluid mud layers can be included in the available depth if they present favorable rheology. As it is difficult to perform in situ... 相似文献
267.
Anthropogenic climate forcing will cause the global mean sea level to rise over the 21st century.However,regional sea level is expected to vary across ocean basins,superimposed by the influence of natural internal climate variability.Here,we address the detection of dynamic sea level(DSL)changes by combining the perspectives of a single and a multimodel ensemble approach(the 50-member CanESM5 and a 27-model ensemble,respectively,all retrieved from the CMIP6 archive),under three CMIP6 projected scenarios:SSP1-2.6,SSP3-7.0 and SSP5-8.5.The ensemble analysis takes into account four key metrics:signal(S),noise(N),S/N ratio,and time of emergence(ToE).The results from both sets of ensembles agree in the fact that regions with higher S/N(associated with smaller uncertainties)also reflect earlier ToEs.The DSL signal is projected to emerge in the Southern Ocean,Southeast Pacific,Northwest Atlantic,and the Arctic.Results common for both sets of ensemble simulations show that while S progressively increases with increased projected emissions,N,in turn,does not vary substantially among the SSPs,suggesting that uncertainty arising from internal climate variability has little dependence on changes in the magnitude of external forcing.Projected changes are greater and quite similar for the scenarios SSP3-7.0 and SSP5-8.5 and considerably smaller for the SSP1-2.6,highlighting the importance of public policies towards lower emission scenarios and of keeping emissions below a certain threshold. 相似文献
268.
Marcos Terradillos-Bernal Martina Demuro Lee J. Arnold Jesús F. Jordá-Pardo Ignacio Clemente-Conte Alfonso Benito-Calvo J. Carlos Díez Fernández-Lomana 《第四纪科学杂志》2023,38(1):21-37
San Quirce is an open-air archaeological site situated on a fluvial terrace in the Duero basin (Palencia, northern Iberia). This paper presents new and consistent chronologies obtained for the sedimentary sequence using post-infrared infrared stimulated luminescence (pIR-IR) dating of K-feldspars and single-grain thermally transferred optically stimulated luminescence (TT-OSL) dating of quartz. The new dating results indicate that the sequence is older than ~200 000 years and place San Quirce Level III within marine isotope stages (MIS) 8 and 7, between 274 ± 13 ka and 238 ± 13 ka. The main lithic assemblage at San Quirce comes from Level III. The predominant tool types found in this level are hammerstones, manuports and flakes, with a small proportion of cores and a significant presence of denticulates. Adaptation to local environmental conditions resulted in distinctive cultural habits, which were embedded in the cultural tradition of hominins occupying the site during the final third of the Middle Pleistocene. San Quirce preserves a simple cultural tradition that was employed by local hominins to engage in a diverse array of activities, and highlights the cultural diversity that appears to have been a characteristic feature of the Lower to Middle Palaeolithic transition 300–200 ka. 相似文献
269.
F. A. Temporim Ricardo Ivan Ferreirae da Trindade Marcos Egydio-Silva Tiago Valim Angelo Eric Tohver Caroline Cibele Soares Lucas Pequeno Gouvêa Julio Cesar Mendes Silvia Regina Medeiros Antônio Carlos Pedrosa-Soares Gabriel Gomes Silva 《地学学报》2023,35(1):23-31
Featuring 3 000-km-long large and hot orogen, the Mantiqueira Province provides a rare opportunity to study the process of gravitational collapse at mid to deep crustal levels. Distinct but contemporary (~500 Ma) post-collisional intrusions show structures and anisotropy of magnetic susceptibility (AMS) fabrics related to their emplacements, recording different flow patterns. In southern deep-seated intrusions, ellipsoidal-shaped roots with gabbroic-to-hybrid cores surrounded by granitic rocks show concentric patterns of AMS fabrics that cut across the NE-trending regional foliation. In contrast, northern intrusions, exposed as the upper sections of batholith-size bodies of coarse-grained granite emplaced at the shallow to mid-crust, show general NS-trending magnetic fabrics roughly parallel to strike of the orogen and the regional foliation of host rocks. These contrasting magnetic patterns from shallow to deeper crust suggest vertical magma migration from the overthickened orogenic core to be emplaced across its thinner stretched flanks during the gravitational collapse of the orogenic edifice. 相似文献