全文获取类型
收费全文 | 560篇 |
免费 | 31篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 36篇 |
地球物理 | 146篇 |
地质学 | 273篇 |
海洋学 | 46篇 |
天文学 | 57篇 |
综合类 | 3篇 |
自然地理 | 29篇 |
出版年
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 14篇 |
2014年 | 18篇 |
2013年 | 32篇 |
2012年 | 29篇 |
2011年 | 24篇 |
2010年 | 29篇 |
2009年 | 39篇 |
2008年 | 20篇 |
2007年 | 30篇 |
2006年 | 30篇 |
2005年 | 33篇 |
2004年 | 37篇 |
2003年 | 28篇 |
2002年 | 29篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 18篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有595条查询结果,搜索用时 31 毫秒
151.
Jesús Vidal Solano Francisco A. Paz Moreno Alexander Iriondo Alain Demant Jean-Jacques Cochem 《Comptes Rendus Geoscience》2005,337(16):314
Scattered ignimbritic mesas crop out in the Hermosillo region (Sonora, Mexico). These rocks that have been dated at 12.5 Ma (Middle Miocene) have the petrography and chemical characteristics of comendites. Such a flare-up of peralkaline acidic volcanism, after a long period of subduction-related arc volcanism, emphasises an important change in the source of volcanism. It corresponds to the latest stage of continental extension prior to the marine invasion and the development of spreading centres in the Gulf of California. To cite this article: J. Vidal Solano et al., C. R. Geoscience 337 (2005). 相似文献
152.
Stochastic analysis of the effect of heterogeneity and fractures on radionuclide transport in a low-permeability clay layer 总被引:1,自引:0,他引:1
Deep low-permeability clay layers are considered as safe environments for disposal of high-level radioactive waste. In Belgium,
the Boom Clay is a candidate host rock for deep geological disposal. In this study, we analyze the effects of fractures and
spatially variable hydraulic conductivity on radionuclide migration through the clay. Fracture geometry and properties are
simulated with Monte Carlo simulation. The heterogeneity of hydraulic conductivity is simulated by direct sequential co-simulation
using measurements of hydraulic conductivity and four types of secondary variables. The hydraulic conductivity and fracture
simulations are used as input for a transport model. Radionuclide fluxes computed with this heterogeneous model are compared
with fluxes obtained with a homogeneous model. The output fluxes of the heterogeneous model differ at most 8% from the homogeneous
model. The main safety function of the Boom Clay is thus not affected by the fractures and the spatial variability of hydraulic
conductivity. 相似文献
153.
Stochastic analysis of the effect of spatial variability of diffusion parameters on radionuclide transport in a low permeability clay layer 总被引:1,自引:0,他引:1
Most studies that incorporate subsurface heterogeneity in groundwater flow and transport models only analyze and simulate the spatial variability of hydraulic conductivity. Heterogeneity of the other flow and transport parameters are usually neglected. This approach is often justified, but there are, however, cases in which disregarding the heterogeneity of the other flow and transport parameters can be questionable. In low permeability media, for instance, diffusion is often the dominant transport mechanism. It therefore seems logical to incorporate the spatial variability of the diffusion parameters in the transport model. This study therefore analyses and simulates the spatial variability of the effective diffusion coefficient and the diffusion accessible porosity with geostatistical techniques and incorporates their heterogeneity in the transport model of a low permeability formation. The formation studied was Boom clay (Belgium), a candidate host rock for the deep geological disposal of high-level radioactive waste. The calculated output radionuclide fluxes of this model are compared with the fluxes calculated with a homogeneous model and a model with a heterogeneous hydraulic conductivity distribution. This analysis shows that the heterogeneity of the diffusion parameters has a much larger effect on the calculated output radionuclide fluxes than the heterogeneity of hydraulic conductivity in the low permeability medium under study. 相似文献
154.
Laurent Viguier Leonardo Barreto Alain Haurie Socrates Kypreos Peter Rafaj 《Climatic change》2006,79(1-2):121-141
In this two-part paper we evaluate the effect of “endogenizing” technological learning and strategic behavior of agents in economic models used to assess climate change policies. In the first part we show the potential impact of R&D policies or demonstration and deployment (D&D) programs in the context of stringent stabilization scenarios. In the second part we show how game-theoretic methods can be implemented in climate change economic models to take into account three types of strategic interactions: (i) the market power of the countries benefiting from very low abatement costs on international markets for CO2 emissions, (ii) the strategic behavior of governments in the domestic allocation of CO2 emissions quotas, and (iii) the non-cooperative behavior of countries and regions in the burden sharing of CO2 concentration stabilization. The two topics of endogenous learning and game-theoretic approach to economic modeling are two manifestations of the need to take into account the strategic behavior of agents in the evaluation of climate change policies. In the first case an R&D policy or a demonstration and deployment (D&D) program are put in place in order to attain a cost reduction through the learning effect; in the second case the agents (countries) reply optimally to the actions decided by the other agents by exploiting their strategic advantages. Simulations based on integrated assessment models illustrate the approaches. These studies have been conducted under the Swiss NCCR-Climate program. 相似文献
155.
Hüseyin Yaln M.Niyazi Gündodu Alain Gourgaud Philippe Vidal Ali Uurum 《Journal of Volcanology and Geothermal Research》1998,85(1-4)
Neogene Yamadağı volcanic rocks consist of basaltic trachyandesite, trachyandesite, andesite, and dacite. The major- and trace-element chemistry indicates that the lavas are dominantly calc-alkaline and mildly alkaline in character, sodic in nature, and intermediate to acidic in composition. REE and trace-element patterns of volcanic rocks are similar to those typical of within plate magmatics. Volcanic rocks have low 87Sr/86Sr (0.70389–0.70633) and high 143Nd/144Nd ratios (0.51267–0.51276) and mostly plot within the mantle array of the isotope ratio diagram. The linear correlations among 87Sr/86Sr−143Nd/144Nd, SiO2−87Sr/86Sr and SiO2−143Nd/144Nd isotope ratios in the volcanics suggest that fractional crystallization combined with minor assimilation was an important process within the collision zone. 相似文献
156.
Mount Hasan is a double-peaked stratovolcano, located in Central Anatolia, Turkey. The magmas erupted from this multi-caldera complex range from basalt to rhyolite, but are dominated by andesite and dacite. Two terminal cones (Big Mt. Hasan and Small Mt. Hasan) culminate at 3253 m and 3069 m respectively. There are four evolutionary stages in the history of the volcanic complex (stage 1: Kecikalesi volcano, 13 Ma, stage 2: Palaeovolcano, 7 Ma, stage 3: Mesovolcano and stage 4: Neovolcano). The eruptive products consist of lava flows, lava domes, and pyroclastic rocks. The later include ignimbrites, phreatomagmatic intrusive breccias and nuées ardentes, sometimes reworked as lahars. The total volume is estimated to be 354 km3, the area extent 760 km2. Textural and mineralogical data suggest that both magma mixing and fractional crystallization were involved in the generation of the andesites and dacites. The magmas erupted from the central volcanoes show a transition with time from tholeite to calc-alkaline. Three generations of basaltic strombolian cones and lava flows were emplaced contemporaneously with the central volcanoes. The corresponding lavas are alkaline with a sodic tendency. 相似文献
157.
158.
Jacques Bourgois Jacques Azema Peter O. Baumgartner Jean Tournon Alain Desmet Jean Aubouin 《Tectonophysics》1984,108(1-2)
The Pre-Upper Senonian basement of Costa Rica crops out in the Santa Elena and Nicoya peninsulas. From south to north and from base to top the basement includes: the Esperanza, Matapalo and Santa Elena units. The Esperanza unit is Albian-Santonian in age and consists mainly of pillow basalt and massive basalt flows. The Matapalo unit includes Callovian to Cenomanian radiolarite and includes massive basalt flows, basalt, and dolerite basement. The Santa Elena unit contains ultramafic and mafic rocks in which harzburgite is the major component. The most important tectonic features of the Nicoya Complex are the large Santa Elena and Matapalo nappes. Nappe emplacement was from north to south during upper Santonian time. The sedimentary cover of the Nicoya Complex comprises:
- 1. (1) the Campanian El Viejo Formation that consists of shallow-water sediments in the north (Santa Elena Peninsula) and the Campanian-Maastrichtian Sabana Grande Formation of deep-water origin in the South (Nicoya Peninsula);
- 2. (2) Paleocene strata indicating deposition in a deep-water environment comprises the Rivas, Las Palmas and Samara Formations;
- 3. (3) a post-upper Eocene (?) sequence that consists of the shallow-water Barra Honda and Montezuma Formations.
159.
Luk Peeters Bruno Haerens Jan Van der Sluys Alain Dassargues 《Environmental Geology》2004,46(6-7):951-961
The Eisden–Meeswijk region in Belgium has been affected by mining subsidence due to the deep coal mining activities. Groundwater levels in the alluvial plain of the Meuse River are maintained below the ground surface by drainage installations and municipal well fields. A correlation between the water level in the Meuse River and the variation in nitrate and sulphate concentrations in the aquifer has been observed. A transient groundwater model is developed for the period May 1998–May 2002 and advective transport simulations have been carried out using this model. During dry periods, the major groundwater flow is directed towards the Meuse River, thereby feeding the river. During wet periods, however, groundwater flows in the opposite direction. Due to these variations in groundwater flow direction and to the extraction of groundwater, zones of higher solute concentration exist of which the position and extension vary both spatially and temporally. 相似文献
160.
Antonio Tadeu dos Reis Christian Gorini Alain Mauffret Wiktor Weibull 《Comptes Rendus Geoscience》2004,336(2):143-150
The Marseilles (also called Marseilles/Planier) and Grand Rhone sedimentary ridges, offshore the Gulf of Lions, western Mediterranean Sea, are generated by sediment spillover funnelled by the Marseilles and Grand-Rhone canyons, respectively. We show that the Marseilles and Grand-Rhone canyon directions are tectonically conditioned by Plio-Quaternary salt-induced sea-floor relief. Overburden extension in the area created an assemblage of listric faults running parallel to the strike of the continental margin. This salt-induced topography resulted in accentuated fault scarps impacting the sea-floor morphology and forcing submarine valleys to deflect to the east. Gravity-induced extension equally influenced the morphological pattern of the valley overbanking deposits. Sediment spillover occurred on both flanks of the canyons, but because active faulting generated space accommodation for overflow deposits, it inhibited the development of typical levee morphology along the canyons' left flanks. To cite this article: A.T. dos Reis, C. R. Geoscience 336 (2004). 相似文献