全文获取类型
收费全文 | 363篇 |
免费 | 30篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 27篇 |
地球物理 | 83篇 |
地质学 | 158篇 |
海洋学 | 37篇 |
天文学 | 56篇 |
综合类 | 2篇 |
自然地理 | 21篇 |
出版年
2024年 | 1篇 |
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 4篇 |
2018年 | 14篇 |
2017年 | 24篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 35篇 |
2013年 | 40篇 |
2012年 | 26篇 |
2011年 | 26篇 |
2010年 | 30篇 |
2009年 | 31篇 |
2008年 | 15篇 |
2007年 | 2篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1968年 | 1篇 |
1962年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有397条查询结果,搜索用时 15 毫秒
51.
52.
Xavier Rodó Mercedes Pascual Francisco J. Doblas-Reyes Alexander Gershunov Dáithí A. Stone Filippo Giorgi Peter J. Hudson James Kinter Miquel-Àngel Rodríguez-Arias Nils Ch. Stenseth David Alonso Javier García-Serrano Andrew P. Dobson 《Climatic change》2013,118(3-4):625-640
The next generation of climate-driven, disease prediction models will most likely require a mechanistically based, dynamical framework that parameterizes key processes at a variety of locations. Over the next two decades, consensus climate predictions make it possible to produce forecasts for a number of important infectious diseases that are largely independent of the uncertainty of longer-term emissions scenarios. In particular, the role of climate in the modulation of seasonal disease transmission needs to be unravelled from the complex dynamics resulting from the interaction of transmission with herd immunity and intervention measures that depend upon previous burdens of infection. Progress is also needed to solve the mismatch between climate projections and disease projections at the scale of public health interventions. In the time horizon of seasons to years, early warning systems should benefit from current developments on multi-model ensemble climate prediction systems, particularly in areas where high skill levels of climate models coincide with regions where large epidemics take place. A better understanding of the role of climate extremes on infectious diseases is urgently needed. 相似文献
53.
Elena DzifčÁKOVÁ 《Solar physics》2006,234(2):243-256
Changes in the excitation equilibrium of Feviii – Fe xv in the solar corona due to the electron non-thermal κ-distribution
are studied. The shape of the distribution affects the electron excitation rate and thus the relative intensities of the spectral
lines. Since the shape of the electron distribution function influences also the ionization equilibrium of Fe, both effects
change the final intensities of the lines. Possibilities for diagnostics of the shape of the electron distribution in the
solar corona are discussed. Synthetic spectrum of Fe for T = 1.58× 106 K and ne = 108 cm−3 is shown together with the synthetic spectra computed with DEM for the quiet Sun. 相似文献
54.
Christian Creixell Miguel ngel Parada Pierrick Roperch Diego Morata Csar Arriagada Carlos Prez de Arce 《Tectonophysics》2006,425(1-4):101-122
The Concón Mafic Dike Swarm (CMDS) consists of basaltic to andesitic dikes emplaced into deformed Late Paleozoic granitoids during the development of the Jurassic arc of central Chile. The dikes are divided into an early group of thick dikes (5–12 m) and a late group of thin dikes (0.5–3 m). Two new amphibole 40Ar/39Ar dates obtained from undeformed and deformed dikes, constrain the age of emplacement and deformation of the CMDS between 163 and 157 Ma. Based on radiometric ages, field observations, AMS studies and petrographic data, we conclude that the emplacement of the CMDS was syntectonic with the Jurassic arc extension and associated with sinistral displacements along the NW-trending structures that host the CMDS. The common occurrence of already deformed and rotated xenoliths in the dikes indicates that deformation in the granitoids started previously.The early thick dikes and country rocks appear to have been remagnetized during the exhumation of deep-seated coastal rocks in the Early Cretaceous (around 100 Ma). The remanent magnetization in late thin dikes is mainly retained by small amounts of low-Ti magnetite at high temperature and pyrrhotite at low temperature. The magnetization in these dikes appears to be primary in origin. Paleomagnetic results from the thin dikes also indicate that the whole area was tilted 23° to the NNW during cooling of the CMDS.The NNW–SSE extension vectors deduced from the paleomagnetic data and internal fabric of dikes are different with respect to extension direction deduced for the Middle–Late Jurassic of northern Chile, pointing to major heterogeneities along the margin of the overriding plate during the Mesozoic or differences in the mechanisms driving extension during such period. 相似文献
55.
An interdisciplinary approach to depict landscape change drivers: A case study of the Ticuiz agrarian community in Michoacan, Mexico 总被引:1,自引:0,他引:1
Minerva Campos Alejandro Velázquez Ángel Guadalupe Priego-Santander 《Applied geography (Sevenoaks, England)》2012,32(2):409-419
Landscape changes are driven by a combination of physical, ecological and socio-cultural factors. Hence, a large amount of information is necessary to monitor these changes and to develop effective strategies for management and conservation. For this, novel strategies for combining social and environmental data need to be developed. The purpose of this study is to demonstrate the value of an innovative interdisciplinary approach to help in explaining landscape change. We integrated three main sources of information: biophysical landscape attributes, land-use/cover change analysis and social perceptions of land-use change, institutional and policy factors and environmental services. Multivariate statistical analysis was used to develop a weight for each variable described or quantified. Finally we identified proximate causes and underlying driving forces of land transformation in the study area. The study was undertaken in a typical community in Mexico. 相似文献
56.
The presence of pingos on Mars has been hypothesized since the period of the Viking mission. In fact, a diverse range of pingo-like features has been found at various martian sites including Elysium, Chryse and Utopia Planitiae in the northern lowlands. Due to the morphology and the geological setting, some of those features were interpreted in different ways, creating some controversies, as happened in Athabasca Valles. This reflects the complexity of interpreting these features by remote sensing and multiple plausible interpretations of the same feature. With the objective of identifying new possible pingos or rootless cones on Mars, we selected a study area in Utopia Planitia (10-55° N, 210-260° W) where the presence of both features is possible due to its geological history (volcanic and hydrological). We analyzed more than 2100 Mars Orbiter Camera (MOC)-narrow angle images in addition to Viking, Thermal Emission Imaging System (THEMIS), and High Resolution Stereo Camera (HRSC) images, together with Mars Orbiter Laser Altimeter (MOLA)-derived Digital Elevation Models (DEMs) with a Geographic Information System (GIS). We found in 94 MOC-narrow angle images dome, cone, and ring-shaped features. We analyzed them from morphological and morphometrical points of view in order to compare them with relevant features on Mars and Earth. We tested different possible origins for those features following the approach of multiple working hypotheses. We conclude that the dome, cone, and ring-shaped features could be pingos, which is in agreement with their geological settings. Regarding the driving heat source for the formation of the purported pingos, we propose the existence of a heat source, possibly a magma chamber, underneath the surface of the Utopia basin. Together with possible climatic shifts, the past activities of the heat source may have caused melting of ground ice. The pingo growth due to freezing of the water would have occurred during the following cold climatic conditions. 相似文献
57.
Vicente Navarro Miguel Candel ngel Yustres Juan Alonso Beatriz García 《Engineering Geology》2009,108(3-4):189-198
This article presents the study conducted and the actions taken to stabilise the foundations of 25 low-rise (two/three-storey) buildings in Alcázar de San Juan (Ciudad Real, central Spain). Owing to the immediate attention required, it was decided that the study would focus on procuring a synthetic model that would be able to provide a satisfactory explanation for the tendency of the movements, overlooking the detailed model of each building. This analysis pointed out that the mobilisation was probably due to both the shrinkage caused by the existing trees during the dry-growing seasons, and to the loss of lateral confinement caused by the excavation of a service trench adjacent to the footings of the buildings. In keeping with this mechanism, stabilization was carried out by transplanting the trees growing near the damaged buildings and installing a line of piles to provide lateral support to the footings. The evolution of the damage was therefore stopped. 相似文献
58.
Guillermo M. MUÑOZ CARO Frans J. M. RIETMEIJER Virginia SOUZA‐EGIPSY Maria Pilar VALLES‐GONZÁLEZ 《Meteoritics & planetary science》2012,47(2):248-261
Abstract– We used a combination of different analytical techniques to study particle W7190‐D12 using microinfrared spectroscopy, micro‐Raman spectroscopy, and field emission scanning electron microscopy (FESEM) energy dispersive X‐ray spectroscopy (EDS). The particle consists mainly of hematite (α‐Fe2O3) with considerable variations in structural disorder. It further contains amorphous (Na,K)‐bearing Ca,Al‐silicate and organic carbon. Iron‐bearing spherules (<150 nm in diameter) cover the surface of this particle. At local sites of structural disorder at the hematite surface, the hematite spheres were reduced to FeO in the presence of organic carbons forming FeO‐spheres. However, metallic Fe spheres cannot be excluded based on the available data. To the best of our knowledge, this particle is the first detection of such spherules at the surface of a stratospheric dust particle. Although there is no definitive evidence for an extraterrestrial origin of particle W7190‐D12, we suggest that it could be an IDP that had moved away from the asteroid‐forming region of the early solar system into the outer solar system of the accreting Kuiper Belt objects. After it was released from a Jupiter family comet, this particle became part of the zodiacal cloud. Atmospheric entry flash‐heating caused (1) the formation of microenvironments of reduced iron oxide when indigenous carbon materials reacted with hematite covering its surface resulting in the formation of FeO‐spheres and (2) Na‐loss from Na,Al‐plagioclase. The particle of this study, and other similar particles on this collector, may represent a potentially new type of nonchondritic IDPs associated with Jupiter family comets, although an origin in the asteroid belt cannot be ignored. 相似文献
59.
60.
Joaquín Márquez-Pérez José I. Álvarez-Francoso 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2017,117(1):53-62
An increase in walking or hiking activities in natural areas requires improvements in information and advice about trails, including their difficulty, available services and estimated travel time. Comparative studies show remarkable differences between measured and calculated travel times obtained by available predictive procedures (Naismith’s rule, Tobler’s hiking function or MIDE). A new procedure has been designed by combining pre-existing methods (Tobler’s and MIDE), and travel times have been calculated for 21 trails located in different protected natural areas of Spain. Times obtained are compared with travel times measured by individual users and uploaded into specialized walking-hiking websites (Wikiloc). Results show that the new procedure (Modified Tobler) reduces differences between calculated and measured travel times, which makes it suitable not only for trail managers to estimate travel times but also as a key part of pedestrian transport analysis in trail networks. 相似文献