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311.
A developmental model of olivine morphology as a function of the cooling rate and the degree of undercooling 总被引:3,自引:2,他引:1
Faure François Trolliard Gilles Nicollet Christian Montel Jean-Marc 《Contributions to Mineralogy and Petrology》2003,145(2):251-263
We performed dynamic crystallization experiments in the CMAS system at 1 atm to investigate the evolution of the morphology of forsterite crystals as a function of cooling rate and degree of undercooling. In sections parallel to the (010) plane, we observed the evolution of the forsterite morphology from tablets to hopper (skeletal) crystals, and then to swallowtail shapes (dendritic morphology) for increased degree of undercooling. The other shapes described in the literature can be interpreted as particular sections of those three shapes. The onset of dendritic growth is due to a competition between the growth of the faces of the initial hopper crystal and dendrite overgrowths. The forsterite dendrites are formed by a succession of units which look like hopper shapes. This result has been tested by an additional set of experiments. 相似文献
312.
Pesticide contamination of the coastline of Martinique 总被引:2,自引:0,他引:2
In January and February 2002, the presence of certain agricultural pesticides throughout the coastline of the Caribbean island of Martinique was investigated. The tropical climate of the French West Indies is suitable for banana production, which requires intensive use of pesticides. An inventory of all pesticides used on the island (compounds and tonnage) was compiled. Surveys and analyses revealed the presence of pesticides in the plumes of seven rivers. The organochlorine chlordecone and metabolites of aldicarb were detected at nearly all of the monitored sites, even though the use of chlordecone has been prohibited since 1993. Two triazines (ametryn and simazine) were also identified. The concentrations of carbamates and triazines detected in the water and sediment samples from Martinique are comparable to those reported for mainland France. Chlordecone concentrations in the sediment and particulate matter samples were, however, particularly high in the samples from Martinique. Toxicological implications are discussed. Of particular concern are the high levels of chlordecone (which is bioaccumulating and carcinogenic) and further monitoring of this compound is recommended, especially in fish and other sea-food products. 相似文献
313.
Lepoint G Vangeluwe D Eisinger M Paster M van Treeck P Bouquegneau JM Gobert S 《Marine pollution bulletin》2004,48(5-6):465-470
A (15)N tracer study was performed during an experimental transplantation trial of natural Posidonia oceanica cuttings. The experiment was done in situ at 17 m depth in the Revellata Bay (Calvi, NW Corsica, France). Despite high survival rates of transplants (>90%) after one year, the weight and the N content of transplants are significantly lower than those of reference plants. In absence of roots, the transplants are not able to meet their N requirement, because leaf uptake is insufficient to replenish the N lost during the natural leaf decay. This could constitute a major cause of long-term failure for transplantation experiments or natural re-colonisation processes. The increase of the (15)N content in the roots shows that the plant re-allocates the nitrogen of one organ (i.e. leaves, rhizomes) to ensure the growth of another (i.e. roots). 相似文献
314.
Gilles Durrieu Régine Maury-Brachet Michel Girardin Eric Rochard Alain Boudou 《Estuaries and Coasts》2005,28(4):581-591
The Gironde estuary, one of the largest in Europe, is considerated as a reference ecological system, with all the western
European diadromous fish species present. The national biomonitoring program on the coastal marine environment has revealed
since 1979 severe metal pollution (mostly cadmium [Cd]) in oysters collected from the estuary. No data are available on metal
contamination levels in fish, despite their ecological and economic importance. We present the results from a detailed study
based on 4 metals (Cd, zinc [Zn], copper [Cu], and mercury [Hg]) measured in 4 organs (gills, dorsal skeletal muscle, liver,
and kidneys) from 8 fish species illustrating several ecological combinations: European eel (Anguilla anguilla), twaite shad (Alosa fallax), bass (Dicentrarchus labrax), meagre (Argyrosomus regius), flounder (Platichthys flesus),, thin-lippid grey mullet (Liza ramada), sole (Solea vulgaris), and Canary drum (Umbrina canariensis). The results show very marked differences between species and organs, as well as very significant variations between the
4 metals. Although metal concentrations measured in fish muscle are low, except in the case of Hg for theA. fallax, high levels of Cu and Cd were observed in the kidneys and livers ofL. ramada andA. anguilla. A multifactorial analysis based on rank ordered metal concentrations for the 8 fish species clearly shows 4 clusters of
species assigned to the different degrees of metal contamination, from the lowest contaminated (A. regius, D. labrax, S. vulgaris, andU. canariensis), to the most contaminated group (L. ramada). The most contaminated species (L. ramada, A. angailla, andP. flesus) are characterized by long residence times in the estuary, between 3.5 and 14 yr. ForL. ramada, biofilms with high metal storage capacities would be the principal uptake route; the two other species are benthic with
a carnivorous regime. Comparisons between our data and four estuaries (Seine, France; Mersey, U.K.; La Plata, Argentina; Guadalquivir,
Spain), on a limited number of common species, metals and fish organs, clearly reveal higher Cd bioaccumulation levels in
the Gironde estuary. 相似文献
315.
Gilles Grandjean Céline Pennetier Adnan Bitri Ombeline Meric Jean-Philippe Malet 《Comptes Rendus Geoscience》2006,338(9):587-595
Geophysical methods such as seismic surveying and electrical resistivity imaging appear to be well-adapted to investigate and understand landslide mechanisms. They allow direct and non-intrusive measurement of acoustic velocity and electrical resistivity, two fundamental parameters used to define the physical properties of the reworked moving materials. Both methods were applied at the Super-Sauze site in the French South Alps, where a typical example of an intra-material earthflow-mudslide can be observed. Measurements were taken simultaneously along two orthogonal profiles: one 325 m in length is perpendicular to the axis of the earthflow; the other 235 m in length is located along the axis of the earthflow. The results show a correlation between the seismic and electrical resistivity data, confirming that the simultaneous use of both methods gives complementary information about landslide mechanisms. The seismic data provide information on fracture density variations, whereas the electrical resistivity data provide information on water content variations. To cite this article: G. Grandjean et al., C. R. Geoscience 338 (2006). 相似文献
316.
John Samuel Vincent Jaillot Clément Colin Diego Vinasco Alvarez Eric Boix Sylvie Servigne Gilles Gesquière 《Transactions in GIS》2023,27(3):841-858
With the widespread availability of a large volume of urban data, stakeholders from different domains require advanced tools to manage, visualize and understand cities and their evolution. During the last few years, researchers have proposed numerous research works and applications to illustrate the cities of the past and possible scenarios of the future under different conditions. However, many of these approaches are one-time solutions and not based on standards, making them obsolete and unusable for reproducible research. In this article, we present UD-SV: an Urban data-Services and Visualization open-source framework for multidisciplinary research to handle complex processing, analysis, and visualization of urban data. However, our goal is not to present a one-time monolithic software solution for urban data management and analysis, but we demonstrate the design and development of an open and interoperable software framework driven by use cases from diverse users to solve applied research challenges. The main contribution of UD-SV is that it uses open standards and open data with documented and reproducible processes with a particular emphasis on the reuse of existing open-source software components. We also show an enhanced use of standards to enable a shift toward components that are interchangeable or composable with other existing components in the GIS community. 相似文献
317.
Gilles Van Hamme 《Geoforum》2012,43(4):772-783
The pertinence of social classes to the understanding of political behaviour has been questioned. The purpose of this article is to propose some directions for a geographical approach of political behaviour centred on social classes. More precisely, we intend here to show how geography can participate in this major debate about the present relevance of social classes. To achieve this objective, a geographical analysis must integrate two major socio-political evolutions since the 1970s: the re-composition processes of social classes and the role of parties in the decline of class voting. Drawing on examples in Belgium, the paper proposes original multi-scalar analyses that take these evolutions into account. At local scale, we highlight fractures inside intermediate classes, which are associated to the fact that left wing segments of these classes are more inclined to live in core cities. At national level, we show the deepness of class and regional gaps in political attitudes despite relative dealignment in electoral behaviour, resulting in the difficulties for big national parties to keep together such a heterogeneous electoral support. Finally, we show how big left wing national parties are able to overcome these difficulties when they are associated to strong and dense local social networks. 相似文献
318.
Fabien Knoll Gilles Cuny Pierre-Olivier Mojon Raquel López-Antoñanzas 《Proceedings of the Geologists' Association. Geologists' Association》2014
The palaeontological content (charophytes and vertebrates) of organic-rich layers from the Middle Jurassic (Bathonian) of the Grands Causses at Mostuéjouls (Aveyron, France) has been examined. It is rich in gyrogonites of Porochara douzensis. The vertebrates of the lower layer include a single hybodontiform tooth, “semionotiform” teeth and scales, and one pycnodontiform tooth whereas the upper layer has yielded one hybodontiform tooth, a variety of actinopterygian remains (mostly Caturus sp. and indeterminate pycnodontiforms) and a few possible reptile remains. The variation in fauna between the two layers is ascribed to a different degree of marine influence. 相似文献
319.
Influence of bioturbation by the polychaete Nereis diversicolor on the structure of bacterial communities in oil contaminated coastal sediments 总被引:1,自引:0,他引:1
Cuny P Miralles G Cornet-Barthaux V Acquaviva M Stora G Grossi V Gilbert F 《Marine pollution bulletin》2007,54(4):452-459
Patterns of change in the structure of bacterial communities monitored by ribosomal intergenic spacer analysis (RISA) in oil contaminated sediments inhabited or not by the marine polychaete Nereis diversicolor were studied during 45 days under laboratory conditions. Results supported by principal component analysis showed a marked response of the bacterial communities to the oil contamination and to the presence of N. diversicolor. Phylogenetic affiliation of specific RISA bands showed that, in the contaminated sediments, the presence of the marine polychaetes favoured the development of bacteria which may play an active role in natural bioremediation processes of oil polluted environments. 相似文献
320.
Sophie Decrée Étienne Deloule Gilles Ruffet Stijn Dewaele Florias Mees Christian Marignac Johan Yans Thierry De Putter 《Mineralium Deposita》2010,45(7):621-629
The Katanga province, Democratic Republic of Congo, hosts world-class cobalt deposits accounting for ~50% of the world reserves.
They originated from sediment-hosted stratiform copper and cobalt sulfide deposits within Neoproterozoic metasedimentary rocks.
Heterogenite, the main oxidized cobalt mineral, is concentrated as “cobalt caps” along the top of silicified dolomite inselbergs.
The supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world-class
“manganese cap” deposits in western Katanga, i.e., the “black earths” that are exploited by both industrial and artisanal
mining. Here, we provide constraints on the genesis and the timing of these deposits. Ar–Ar analyses of oxidized Mn ore and
in situ U–Pb SIMS measurements of heterogenite yield Mio–Pliocene ages. The Ar–Ar ages suggest a multi-phase process, starting
in the Late Miocene (10–5 Ma), when the metal-rich substratum was exposed to the action of meteoric fluids, due to major regional
uplift. Further oxidation took place in the Pliocene (3.7–2.3 Ma) and formed most of the observed deposits under humid conditions:
Co- and Mn-caps on metal-rich substrata, and coeval Fe laterites on barren areas. These deposits formed prior to the regional
shift toward more arid conditions in Central Africa. Arid conditions still prevailed during the Quaternary and resulted in
erosion and valley incision, which dismantled the metal-bearing caps and led to ore accumulation in valleys and along foot
slopes. 相似文献