全文获取类型
收费全文 | 241篇 |
免费 | 11篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 15篇 |
地球物理 | 57篇 |
地质学 | 119篇 |
海洋学 | 37篇 |
天文学 | 25篇 |
自然地理 | 1篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 10篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 14篇 |
2012年 | 14篇 |
2011年 | 9篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 19篇 |
2007年 | 12篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 1篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
排序方式: 共有258条查询结果,搜索用时 296 毫秒
241.
Heliana Teixeira João Magalhães Neto Joana Patrício Helena Veríssimo Rute Pinto Fuensanta Salas João Carlos Marques 《Marine pollution bulletin》2009,58(10):1477-1486
Assessing the health of ecosystems has become a focal point among researchers worldwide. Recently, the European Water Framework Directive intensified the development of approaches to assess ecosystems’ ecological quality. The Benthic Assessment Tool (BAT) is a multimetric approach to evaluate condition of subtidal soft bottom macroinvertebrates of coastal and transitional waters. The effects of anthropogenic disturbances on benthic macroinvertebrate communities, from 1990 to 2006, allowed testing BAT performance in Mondego estuary (Portugal). The method was able to detect decrease on ecological quality, induced essentially by eutrophication and physical disturbances, and follow communities’ subsequent recovery. It evidenced, nevertheless, some limitations associated with the unstable nature of estuaries. The ecological classification of key species in the community and the balance expected between ecological groups of estuarine communities had great influence in the final ecological assessment. Shortcomings of the method were discussed in the light of its suitability for assessing transitional waters’ condition. 相似文献
242.
We produce factor of safety (FOS) and slope failure susceptibility index (SFSI) maps for a 4.4-km2 study area in Rio de Janeiro, Brazil, in order to explore the sensitivity of the geotechnical and geohydraulic parameterization on the model outcomes. Thereby, we consider parameter spaces instead of combinations of discrete values. SFSI is defined as the fraction of tested parameter combinations within a given space yielding FOS <1. We repeat our physically based calculations for various parameter spaces, employing the infinite slope stability model and the sliding surface model of the software r.slope.stability for testing the geotechnical parameters and the Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Model (TRIGRS) for testing the geohydraulic parameters. Whilst the results vary considerably in terms of their conservativeness, the ability to reproduce the spatial patterns of the observed landslide release areas is relatively insensitive to the variation of the parameterization as long as there is sufficient pattern in the results. We conclude that landslide susceptibility maps yielded by catchment-scale physically based models should not be interpreted in absolute terms and suggest that efforts to develop better strategies for dealing with the uncertainties in the spatial variation of the key parameters should be given priority in future slope stability modelling efforts. 相似文献
243.
Arthur Ayres Neto Vanessa Alves da Costa Clara Pinto Ferreira Maia Porto Thais Cristina Vargas Garrido Jean-Pierre Hermand 《Marine Georesources & Geotechnology》2020,38(4):437-449
AbstractMarine mining is the ocean’s new exploration frontier, and polymetallic crusts (PMCs) and ferromanganese nodules are considered a strategic resource for the future. Acoustic geophysical methods are a valuable tool for oceanic research and have been employed for several decades in the exploration of marine resources and environmental evaluations. The main objective of this work was to investigate the correlation between the chemical composition of PMCs from three different areas along the Brazilian continental margin and their physico-acoustic attributes (P-wave velocity, density and acoustic impedance). The results show that the geoacoustic properties of PMCs are correlated to their chemical composition. Measurements showed positive and negative trends between acoustic impedance and studied elements (Fe, Mn, Co, Cu, Zn, W and Ni) according to the direction of measurement, indicting high anisotropy levels. Our study sheds initial light on the correlation between acoustic properties and metal content of PMCs. The study facilitates assessments of the acoustic responses of PMCs allowing more efficient prospection and exploitation compared to ship-board geophysical techniques that are too qualitative to identify PMCs. The results can contribute to determining the best procedures and techniques for more efficient future exploration of this resource. 相似文献
244.
Potassic and low- and high-Ti mildly alkaline volcanism in the Neoproterozoic Ramada Plateau, southernmost Brazil 总被引:1,自引:0,他引:1
Carlos Augusto Sommer Evandro Fernandes de Lima Lauro Valentim Stoll Nardi Ana Maria Graciano Figueiredo Ronaldo Pierosan 《Journal of South American Earth Sciences》2005,18(3-4):237-254
Ramada Plateau Neoproterozoic volcanism represents a portion of the shoshonitic and mildly alkaline magmatism related to postcollisional events of the Brasiliano/Pan African cycle of southernmost Brazil. It is constituted by shoshonitic basic-intermediate lavas, followed by a bimodal sequence characterized by pyroclastic deposits, lava flows, and hypabyssal rocks with ages of 549±5 Ma. The shoshonitic magmatism presents greater K2O than Na2O2, K2O/Na2O ratios close to 1, and moderate large ion lithophile and high-field strength element contents. The bimodal basic-acid volcanism presents a transitional chemical affinity with features of sodic, silica-saturated alkaline to continental tholeiitic series. Observed basic and acid rocks with contrasting Ti contents are referred to as high- and low-Ti basalt-rhyolites. Another group of acid rocks with higher Nb, Ta, and Rb values was identified as high-Nb rhyolites. The Ramada Plateau magmatism is comparable to associations related to the final stages of orogenic cycles, in which shoshonitic and high- and low-Ti alkaline magmatism reflects the melting of subduction-modified sources, whereas the high-Nb magmas show less influence of subduction-related metasomatism and are closer to magmas produced from anorogenic sources. A model of magma generation in collisional settings involving slab break-off and asthenospheric upwelling is applied to the evolution of magmatism from subduction-related to anorogenic in the Ramada Plateau. 相似文献
245.
Spatial distribution of heavy metals in surficial sediments from Guanabara Bay: Rio de Janeiro, Brazil 总被引:1,自引:0,他引:1
José Antônio Baptista Neto Franz Xaver Gingele Thomas Leipe Isa Brehme 《Environmental Geology》2006,49(7):1051-1063
Ninety-two surface sediment samples were collected in Guanabara Bay, one of the most prominent urban bays in SE Brazil, to
investigate the spatial distribution of anthropogenic pollutants. The concentrations of heavy metals, organic carbon and particle
size were examined in all samples. Large spatial variations of heavy metals and particle size were observed. The highest concentrations
of heavy metals were found in the muddy sediments from the north western region of the bay near the main outlets of the most
polluted rivers, municipal waste drainage systems and one of the major oil refineries. Another anomalous concentration of
metals was found adjacent to Rio de Janeiro Harbour. The heavy metal concentrations decrease to the northeast, due to intact
rivers and the mangrove systems in this area, and to the south where the sand fraction and open-marine processes dominate.
The geochemical normalization of metal data to Li or Al has also demonstrated that the anthropogenic input of heavy metals
have altered the natural sediment heavy metal distribution. 相似文献
246.
D. Vitullo R. Altieri A. Esposito F. Nigro M. Ferrara G. Alfano G. Ranalli V. De Cicco G. Lima 《International Journal of Environmental Science and Technology》2013,10(2):209-220
Two organic amendments (OMW-M1 and OMW-M2), based on olive mill wastes (OMWs) subjected to advanced processes of aerobic static storage or composting, were tested for their suppressive activity against Verticillium dahliae, the causal agent of olive Verticillium wilt. OMW-M1 and OMW-M2 drastically inhibited the pathogen growth in vitro and then were further tested in suppressive pot experiments. The amendments, mixed at 15 % (v/v) with a nursery standard plant-growth matrix, were tested alone or in combination with two biocontrol bacteria (Bacillus amyloliquefaciens and Burkholderia cepacia) selected from suppressive soils. All mixtures were artificially contaminated with V. dahliae microsclerotia (MS), the density of which was periodically monitored by either a semi-selective medium or a specific real-time Polymerase Chain Reaction technique. In plant-less pot assays conducted in a growth chamber, OMW-M1 was the most effective amendment, reducing V. dahliae MS density by 100 % after 90 days with respect to the untreated control. In nursery experiments with pot-growing olive plants, OMW-M1, particularly when combined with the biocontrol bacteria, confirmed its strong suppressive activity reducing up to 100 % the density of V. dahliae MS in the rhizosphere behaving even better than a commercial biofungicide (Trichoderma asperellum TV1) used as a control. The best combined treatment also reduced plant mortality and increased root and shoot extension. It is concluded that organic amendments from stabilized olive mill by-products showed positive agronomic and phytosanitary properties on pot-growing olive plants and, particularly when enriched with biocontrol agents, they are potentially suitable for use in sustainable agriculture. 相似文献
247.
Dahlquist Juan A. Alasino Pablo H. Basei Miguel A. S. Morales Cámera Matías M. Macchioli Grande Marcos da Costa Campos Neto Mario 《International Journal of Earth Sciences》2018,107(7):2575-2603
International Journal of Earth Sciences - We report a study integrating 13 new U–Pb LA-MC-ICP-MS zircon ages and Hf-isotope data from dated magmatic zircons together with complete... 相似文献
248.
249.
250.
Gustavo M. Martins Rita F. Patarra Nuno V. Álvaro Afonso C. L. Prestes Ana I. Neto 《Marine Ecology》2013,34(3):289-297
A better understanding of biological systems can only be gained if we understand what processes are important and how they operate to determine the distribution of organisms. Coastal orientation and depth can influence environmental conditions, including the degree of water motion and availability of light, which in turn may influence the horizontal and vertical patterns of organism distribution. Here, we used a mixed‐model design to examine the effects of coastal orientation and depth on the structure of benthic assemblages by comparing the abundance and distribution of macroalgae and invertebrates in shallow and deep waters on the opposing coasts of São Miguel. Generally, coastal orientation had little influence on the distribution of most taxa. In contrast, significant differences were generally associated with depth, although patterns were spatially variable at the scale of locations. This study suggests that depth, and processes operating at the scale of location, but not at the scale of the coast, have an important influence on these assemblages, and that failure to recognise such a scale of variability may hamper our ability to better understand the processes that structure these communities. 相似文献