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131.
Ghazar Galoyan Yann Rolland Marc Sosson Michel Corsini Sandra Billo Chrystelle Verati Rafael Melkonyan 《Journal of Asian Earth Sciences》2009,34(2):135-153
In the Lesser Caucausus the Sevan-Akera ophiolites of N Armenia have lithological features of a slow-spreading oceanic lithosphere: serpentinites are frequently exposed and hydrothermalized at sea-floor level, plutonic rocks and dykes are rare. A complete differentiation trend is observed from mafic norites evolving to diorites and plagiogranites. Normal faults have exposed some of the deep magmatic rocks at sea-floor level. Geochemically, two distinct lava flow series have been distinguished: (1) a contaminated Mid-Oceanic Ridge Basalt (MORB) series evolving from gabbros to plagiogranites and from basalts to basaltic andesites, exhibiting slight calc-alkaline features (enrichments in Large Ion Lithophile Elements (LILE); negative anomalies in Nb–Ta and Ti relative to N-MORB); (2) an alkaline series evolving from basanites to trachy-andesites (on anhydrous basis). 40Ar/39Ar age on amphibole-bearing gabbros evidence a Middle Jurassic age (165.3 ± 1.7 Ma, 2σ) for oceanic crust formation. Structural data, including geological cross-sections and logs of the ophiolite along the northern part of Sevan Lake allow discussing the geodynamic evolution of that segment of the Amassia-Sevan-Akera ophiolitic suture zone. 相似文献
132.
Centrifuge modelling of raked piles 总被引:1,自引:1,他引:0
Sandra Escoffier Jean-Louis Chazelas Jacques Garnier 《Bulletin of Earthquake Engineering》2008,6(4):689-704
Inclined piles are prohibited by many codes in seismic areas. Nevertheless the battered effect has not yet been clarified
because very few data are available. The present work is a comparison, at reduced scale in the centrifuge, of the response
of two simplified pile groups: a 1 × 2 vertical piles and 1 × 2 pile group with one inclined pile. Two configurations are
considered: end-bearing and floating pile group, both with pile heads rigidly fixed with a massive cap. First, repeatability
tests under horizontal cyclic loading were performed on both floating pile groups. Secondly, repeated horizontal impact tests
were performed on both end-bearing pile groups. These impact tests, which highlight the influence of inclined piles on the
inertial response of a group, are a first step for the more complex analysis of the performance of such groups under seismic
loads where inertial and kinematic interactions are combined. The first part of this work revealed the influence of sand structure
around the inclined pile tip on the repeatability of the tests performed on floating pile groups. The second part highlighted
differences in the dynamic response between the two end-bearing pile groups through measurements of the pile cap acceleration,
the bending moment profile and the axial load in the piles. 相似文献
133.
Luca Amendola Sandra Savaglio 《Monthly notices of the Royal Astronomical Society》1999,309(3):576-584
We investigate the clustering properties of 13 QSO lines of sight in flat space, with average redshifts from z ≈2 to 4. We estimate the 1D power spectrum and the integral density of neighbours, and discuss their variation with respect to redshift and column density. We compare the results with standard CDM models, and estimate the power spectrum of Lyman- α clustering as a function of both redshift and column density. We find that (a) there is no significant periodicity or characteristic scale; (b) the clustering depends on both column density and redshift; (c) the clustering increases linearly only if at the same time the H i column density decreases strongly with redshift. The results remain qualitatively the same, assuming an open cosmological model. 相似文献
134.
Diffusion of ions in sea water and in deep-sea sediments 总被引:3,自引:0,他引:3
Sandra Gregory 《Geochimica et cosmochimica acta》1974,38(5):703-714
The tracer-diffusion coefficient of ions in water, Dj0, and in sea water, , differ by no more than zero to 8 per cent. When sea water diffuses into a dilute solution of water, in order to maintain the electro-neutrality, the average diffusion coefficients of major cations become greater but of major anions smaller than their respective or Dj0 values. The tracer diffusion coefficients of ions in deep-sea sediments, Dj,sed., can be related to by , where θ is the tortuosity of the bulk sediment and a a constant close to one. 相似文献
135.
Sandra?RichardEmail authorView authors OrcID profile Kevin?J.?E.?Walsh 《Theoretical and Applied Climatology》2018,134(1-2):121-138
Multi-scale interactions between El Niño–Southern Oscillation and the Boreal Winter Monsoon contribute to rainfall variations over Malaysia. Understanding the physical mechanisms that control these spatial variations in local rainfall is crucial for improving weather and climate prediction and related risk management. Analysis using station observations and European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim) reanalysis reveals a significant decrease in rainfall during El Niño (EL) and corresponding increase during La Niña particularly north of 2°N over Peninsular Malaysia (PM). It is noted that the southern tip of PM shows a small increase in rainfall during El Niño although not significant. Analysis of the diurnal cycle of rainfall and winds indicates that there are no significant changes in morning and evening rainfall over PM that could explain the north–south disparity. Thus, we suggest that the key factor which might explain the north–south rainfall disparity is the moisture flux convergence (MFC). During the December to January (DJF) period of EL years, except for the southern tip of PM, significant negative MFC causes drying as well as suppression of uplift over most areas. In addition, lower specific humidity combined with moisture flux divergence results in less moisture over PM. Thus, over the areas north of 2°N, less rainfall (less heavy rain days) with smaller diurnal rainfall amplitude explains the negative rainfall anomaly observed during DJF of EL. The same MFC argument might explain the dipolar pattern over other areas such as Borneo if further analysis is performed. 相似文献
136.
We discuss the measurement of the average angle within pairs of muons detected in underground experiments versus their relative distance, as a tool for studying primary Cosmic Ray interactions. We propose to call Φ(d) “decorrelation” function. Under simplifying approximation, the decorrelation function can be computed analytically to show its dependence on details of cosmic ray interactions as well as on the propagation in the rock. We argue that this new measurement is useful in a real experiment, complementing traditional ones like the decoherence function. 相似文献
137.
138.
Alves SR Severino PC Ibbotson DP da Silva AZ Lopes FR Sáenz LA Bainy AC 《Marine environmental research》2002,54(3-5):241-245
Furadan is a carbamate pesticide used widely to combat agricultural pests. However little information is available about the toxicity of furadan in aquatic macroinvertebrates. The in vivo effects of furadan were evaluated in mussels, Perna perna, and oysters, Crassostrea rhizophorae. Glutathione S-transferase (GST), catalase (CAT) and cholinesterase (ChE) activities were measured in the gills of both species exposed to furadan (100 microg/l) for 96 h. No changes were observed in GST activity in the exposed groups. CAT activity was higher (9%) in the oysters exposed to furadan. ChE activity was inhibited by 64 and 35%, respectively, in C. rhizophorae and P. perna exposed to furadan, suggesting that the former is more susceptible to the toxic effects of furadan. 相似文献
139.
Falasca Silvia Ulberich Ana Pitta-Alvarez Sandra 《Theoretical and Applied Climatology》2017,129(3-4):1321-1333
Theoretical and Applied Climatology - The growing biodiesel production requires the use of new technologies and alternative feedstocks to maintain the growing demand of this biofuel. The macaw... 相似文献
140.
Simone Wengrat Andre A. Padial Erik Jeppesen Thomas A. Davidson Luciane Fontana Sandra Costa-Böddeker Denise C. Bicudo 《Journal of Paleolimnology》2018,60(2):299-309
Biodiversity changes in response to eutrophication, climate variability and species invasions. These pressures have been shown to reduce community heterogeneity at various scales; however, how productivity drives homogenization patterns in a community of primary producers, such as diatoms, has not been studied. Using a dataset with good temporal resolution, obtained from cores collected from seven tropical reservoirs, we evaluated patterns of spatial and temporal homogenization, i.e. the trends in temporal α-diversity and spatial β-diversity (change in community composition), of diatom assemblages over the past 60–100 years. The paleolimnological records allowed us to study biodiversity trends since the initial community (reservoir construction) in those systems with low anthropogenic impact and also those undergoing eutrophication. No clear trend of spatial β-diversity change over time was found when all reservoirs were analyzed together. However, when only eutrophic reservoirs were considered, a marked decrease in the spatial β-diversity occurred, suggesting that eutrophication leads to homogenization of the diatom assemblage. These findings were reinforced by the lack of change in β-diversity when the age of the reservoirs was standardized, indicating that the reservoirs’ ontogeny did not influence the spatial β-diversity trend and β-diversity did not increase even in the reservoirs with low anthropogenic impact. In addition, the results showed a decrease of α-diversity over time for almost all the eutrophic reservoirs, as well as a decrease in the total species pool for the reservoirs, although periphytic diatoms may be favored by the appearance and sometimes mass development of floating macrophytes in warm, shallow eutrophic reservoirs. This study supports the role of eutrophication as one of the main drivers of diatom assemblage homogenization in tropical reservoirs, with a significant loss of species over time. 相似文献