全文获取类型
收费全文 | 334篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 11篇 |
地球物理 | 111篇 |
地质学 | 141篇 |
海洋学 | 37篇 |
天文学 | 30篇 |
综合类 | 1篇 |
自然地理 | 17篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 17篇 |
2017年 | 20篇 |
2016年 | 17篇 |
2015年 | 23篇 |
2014年 | 20篇 |
2013年 | 19篇 |
2012年 | 22篇 |
2011年 | 22篇 |
2010年 | 26篇 |
2009年 | 18篇 |
2008年 | 31篇 |
2007年 | 20篇 |
2006年 | 4篇 |
2005年 | 15篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 10篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有352条查询结果,搜索用时 15 毫秒
221.
Adriano Ribolini Alessandro Chelli Mauro Guglielmin Marta Pappalardo 《Quaternary Research》2007,68(3):353-363
In the Schiantala Valley of the Maritime Alps, the relationship between a till-like body and a contiguous rock glacier has been analyzed using geomorphologic, geoelectric and ice-petrographic methodologies. DC resistivity tomographies undertaken in the till and in the rock glacier show the presence of buried massive ice and ice-rich sediments, respectively. Ice samples from a massive ice outcrop show spherical gas inclusions and equidimensional ice crystals that are randomly orientated, confirming the typical petrographic characteristics of sedimentary ice. The rock glacier formation began after a phase of glacier expansion about 2550 ± 50 14C yr BP. Further ice advance during the Little Ice Age (LIA) overrode the rock glacier root and caused partial shrinkage of the pre-existing permafrost. Finally, during the 19th and 20th centuries, the glacial surface became totally debris covered. Geomorphological and geophysical methods combined with analyses of ice structure and fabric can effectively interpret the genesis of landforms in an environment where glaciers and permafrost interact. Ice petrography proved especially useful for differentiating ice of past glaciers versus ice formed under permafrost conditions. These two mechanisms of ice formation are common in the Maritime Alps where many sites of modern rock glaciers were formerly occupied by LIA glaciers. 相似文献
222.
Mauro Coltorti Jacopo Della Fazia 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):218-126
The Quebrada Ñaguapua alluvial fan provides a record of changes that have affected the Bolivian Chaco during the Holocene. The 4th oldest Unit, possibly related to the last glaciation, is restricted to the fan apex; it was deeply dissected during the Early Holocene, with three other units emplaced within the resultant incision. Sandy sediments characterise Unit 1 and 3 while Unit 2 is a forest soil that marks a period of stability. The oldest Unit 1 was deposited just before 6900 years BP. It contains artefacts that represent the earliest evidence of human occupation and suggests that deposition was perhaps induced by deforestation. Anthropogenic deforestation is evident at the base of Unit 3, which contains a wooden plank (140 years BP), charcoal, ash and charred tree-trunks. Some trunks have been burnt in situ while others survived the fire and are still growing, although their roots emanate from Unit 2. Although, similar events slightly to the north have been attributed to climatic changes, the delay in soil erosion in closely spaced areas could be plausibly attributed to human-induced changes. Megafaunal remains in Unit 1 represent the last occurrence of megafauna, including horse, in South America. The faunal association is anomalous because of the concurrent presence of aquatic, forest and open-environment species. We suggest that the last migrated from the southern part of Continent, where ecologic conditions allowed their survival in the Early Holocene, after the widespread clearing of the natural forest and shortly prior to the extinction of the Magafauna. 相似文献
223.
Duccio Tampucci Mauro Gobbi Giuseppe Marano Patrizia Boracchi Giacomo Boffa Francesco Ballarin Paolo Pantini Roberto Seppi Chiara Compostella Marco Caccianiga 《Boreas: An International Journal of Quaternary Research》2017,46(2):185-198
Active rock glaciers are periglacial landforms consisting of coarse debris with interstitial ice or ice‐core. Recent studies showed that such landforms are able to support plant and arthropod life and could act as warm‐stage refugia for cold‐adapted species due to their microclimate features and thermal inertia. However, integrated research comparing active rock glaciers with surrounding landforms to outline their ecological peculiarities is still scarce. We analysed the abiotic (ground surface temperature and humidity, soil physical and chemical parameters) and biotic (plant and arthropod communities) features of two Alpine active rock glaciers with contrasting lithology (silicate and carbonate), and compared them with the surrounding iceless landforms as reference sites (stable slopes and active scree slopes). Our data show remarkable differences between stable slopes and unstable landforms as a whole, while few differences occur between active scree slopes and active rock glaciers: such landforms show similar soil features but different ground surface temperatures (lower on active rock glaciers) and different occurrence of cold‐adapted species (more frequent/abundant on active rock glaciers). Both plant and arthropod species distributions depend mainly on the geographical context as a function of soil pH and on the contrast between stable slopes and unstable landforms as a function of the coarse debris fraction and organic matter content, while the few differences between active scree slopes and active rock glaciers can probably be attributed to microclimate. The role of active rock glaciers as potential warm‐stage refugia for cold‐adapted species is supported by our data; however, at least in the European Alps, their role in this may be less important than that of debris‐covered glaciers, which are able to host cold‐adapted species even below the climatic tree line. 相似文献
224.
225.
Mauro Dolce Francesca Pacor Roberto Paolucci 《Bulletin of Earthquake Engineering》2011,9(6):1717-1721
The Special Issue of the Bulletin of Earthquake Engineering devoted to the new Italian strong motion database ITACA (ITalian
ACelerometric Archive) is introduced in this foreword. An overview of the papers published in this issue is presented, providing
an idea of the number of problems encountered in the compilation of a database as rich of information as ITACA, of the solutions
adopted and of the possible research and practical applications. Most of the contents, though specifically addressed to ITACA
and to its accelerograms, can be usefully thought of as an exemplification of approaches and methods that can be used for,
and extended to, similar databases in other countries. 相似文献
226.
227.
228.
Claudio Lo Iacono Attilio Sulli Mauro Agate Valeria Lo Presti Fabrizio Pepe Raimondo Catalano 《Marine Geophysical Researches》2011,32(1-2):127-138
The continental shelf and the upper slope of the Gulf of Palermo (Southern Tyrrhenian Sea) in the depth interval ranging from 50 to 1,500 m were mapped for the first time with Multi Beam echosounder and high resolution seismic. Seven submarine canyons are confined to the upper slope or indent the shelf-edge and enter the Palermo intraslope basin at a depth of around 1,300 m. The canyons evolved through concurrent top-down turbiditic processes and bottom-up retrogressive mass failures. Most of the mass failure features of the area are related to canyon-shaping processes and only few of them are not confined to the upper slope. In general, these features probably do not represent a significant tsunami hazard along the coast. The geological element that controls the evolution of the canyons and induces sediment instability corresponds to the steep slope gradient, especially in the western sector of the Gulf, where the steepest canyons are located. The structural features mapped in the Palermo offshore contributed to the regulation of mass failure processes in the area, with direct faults and antiform structures coinciding with some of the canyon heads. Furthermore, the occurrence of pockmarks and highs that probably consist of authigenic carbonates above faulted and folded strata suggests a local relationship between structural control, fluid escape processes and mass failure. This paper presents a valuable high-resolution morphologic dataset of the Gulf of Palermo, which constitutes a reliable base for evaluating the geo-hazard potential related to slope failure in the area. 相似文献
229.
Michael M. McGlue Aguinaldo Silva Fabrício A. Corradini Hiran Zani Mark A. Trees Geoffrey S. Ellis Mauro Parolin Peter W. Swarzenski Andrew S. Cohen Mario L. Assine 《Journal of Paleolimnology》2011,46(2):273-289
Sediment records from floodplain lakes have a large and commonly untapped potential for inferring wetland response to global
change. The Brazilian Pantanal is a vast, seasonally inundated savanna floodplain system controlled by the flood pulse of
the Upper Paraguay River. Little is known, however, about how floodplain lakes within the Pantanal act as sedimentary basins,
or what influence hydroclimatic variables exert on limnogeological processes. This knowledge gap was addressed through an
actualistic analysis of three large, shallow (<5 m) floodplain lakes in the western Pantanal: Lagoa Gaíva, Lagoa Mandioré
and Baia Vermelha. The lakes are dilute (CO3
2− > Si4+ > Ca2+), mildly alkaline, freshwater systems, the chemistries and morphometrics of which evolve with seasonal flooding. Lake sills
are bathymetric shoals marked by siliciclastic fans and marsh vegetation. Flows at the sills likely undergo seasonal reversals
with the changing stage of the Upper Paraguay River. Deposition in deeper waters, typically encountered in proximity to margin-coincident
topography, is dominated by reduced silty-clays with abundant siliceous microfossils and organic matter. Stable isotopes of
carbon and nitrogen, plus hydrogen index measured on bulk organic matter, suggest that contributions from algae (including
cyanobacteria) and other C3-vegetation dominate in these environments. The presence of lotic sponge spicules, together with patterns of terrigenous sand
deposition and geochemical indicators of productivity, points to the importance of the flood pulse for sediment and nutrient
delivery to the lakes. Flood-pulse plumes, waves and bioturbation likewise affect the continuity of sedimentation. Short-lived
radioisotopes indicate rates of 0.11–0.24 cm year−1 at sites of uninterrupted deposition. A conceptual facies model, developed from insights gained from modern seasonal processes,
can be used to predict limnogeological change when the lakes become isolated on the floodplain or during intervals associated
with a strengthened flood pulse. Amplification of the seasonal cycle over longer time scales suggests carbonate, sandy lowstand
fan and terrestrial organic matter deposition during arid periods, whereas deposition of lotic sponges, mixed aquatic organic
matter, and highstand deltas characterizes wet intervals. The results hold substantial value for interpreting paleolimnological
records from floodplain lakes linked to large tropical rivers with annual flooding cycles. 相似文献
230.
Seismic-event-based methodology to obtain earthquake-induced translational landslide regional hazard maps 总被引:1,自引:0,他引:1
A seismic-event-based methodology to generate earthquake-induced translational landslide maps using Newmark method is proposed. The steps are: (1) to construct a GIS-based geotechnical database; (2) to identify those areas that are susceptible to the occurrence of translational landslides based on available geological information; (3) to compute a static safety factor; (4) to compute the critical acceleration that defines the threshold acceleration required to cause a displacement; (5) to characterize the seismic hazard as a set of stochastic events, collectively exhaustive and mutually exclusive, that fully describes the hazard spatial distribution and annual frequency of occurrence (in accordance with the earthquake location, depth and magnitude) with the appropriate ground-motion prediction equations; (6) to compute the Newmark displacement; and finally, (7) to carry out a probabilistic translational landslide hazard analysis to estimate an exceedance rate of a given displacement. This methodology is applied to Mexico, and maps for return periods of 150 and 500 years are presented. Results shown in maps are estimations of where translational landslides may occur and should be useful to carry out local studies to elaborate recommendations of site specific hazard reduction plans as well as to calculate insurance rates. In addition, these results are useful to identify civil protection actions, risk management at regional and local level, and land use planning, as well as for promoting more detailed vulnerability and risk studies at different scales. 相似文献