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61.
Roberto De Propris Matthew Colless John A. Peacock Warrick J. Couch Simon P. Driver Michael L. Balogh Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Chris Collins Nicholas Cross Gavin Dalton George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Edward Hawkins Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg Will Percival Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,351(1):125-132
62.
Chris Blake Michael B. Pracy Warrick J. Couch Kenji Bekki Ian Lewis Karl Glazebrook Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Carole Jackson Ofer Lahav Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,355(3):713-727
63.
64.
Trapper R. Dickson Darren G. Bos Marlow G. Pellatt Ian R. Walker 《Journal of Paleolimnology》2014,51(3):325-341
We compared water chemistry and environmental data with midge assemblage data, using multivariate analysis to assess the environmental gradients that limit midge (Chironomidae, Chaoboridae and Ceratopogonidae) distributions in the Hudson Bay Lowlands, northeastern Manitoba, Canada. Midge remains, comprising 62 taxa, were obtained from surficial sediments of 63 ponds. Ponds were sampled to maximize the salinity gradient. Specific conductance ranged from 46 to 29,000 μS cm?1. Proximity to the coast was a principal determinant of pond salinity, with ponds closer to Hudson Bay shoreline more saline that those farther away. Multivariate analysis indicated that midge distributions have a significant relationship ( $ {\text{r}}_{\text{boot}}^{2} = 0.68 $ ) with salinity in the data set. This work will allow paleolimnological inferences of midge community responses to changing sea level (i.e. salinity) via isostatic rebound within the Hudson Bay Lowlands, and will provide essential limnological information to scientists and managers in a region where understanding of aquatic ecosystems is limited. One undescribed midge taxon was dominant in ponds with the highest salinities and may be a key indicator for inferring highly saline environments. 相似文献
65.
Darren M. Parsons Mark A. Morrison Simon F. Thrush Crispin Middleton Matt Smith Keren T. Spong Dane Buckthought 《Marine Ecology》2013,34(4):492-500
Estuarine and sheltered coastal habitats that contain physical structure are potentially important nurseries for juvenile fish. Many of these structured habitats, however, are potentially vulnerable to stressors such as elevated turbidity. Quantifying the benefits that structured habitats provide to juvenile fish may therefore be an important step in the management process. We investigated the value of structured habitat for juvenile fishes in northeastern New Zealand, using artificial seagrass units (ASUs) with varying blade density. ASUs were predominantly settled by juvenile snapper (Pagrus auratus) and spotty (Notolabrus celidotus). The density of both snapper and spotty was greatest on ASUs with the highest blade density. For snapper, a gradient in abundance was present (with higher abundance closer to the harbour mouth), suggesting either a gradient in the supply of recruits or a potential recruitment shadow effect. The size distribution of juvenile snapper (12–70 mm fork length) was very similar on both sampling trips, despite the 2‐month interim period, suggesting an ontogenetic habitat shift dependent on size. The condition of juvenile snapper from ASUs with the highest blade density was also greater than the other ASU treatments. Overall, these results provide new empirical evidence that habitats with physical structure within shallow estuarine systems are important to early stage juvenile fishes such as snapper, and indicate that the location‐specific context of that habitat is also likely important. 相似文献
66.
The shared Torres Strait rock lobster (Panulirus ornatus) fishery provides important income for commercial and traditional fishers in Australia and Papua New Guinea. The lobster stock is first fished in Torres Strait by divers from both countries and then becomes vulnerable to Australian prawn trawlers, followed by Papua New Guinea trawlers during its annual breeding migration. Lobster catch sharing arrangements are governed by the Torres Strait Treaty ratified in 1985, but the sequential trawling of breeding lobsters has been controlled by bilateral agreements. A trawl ban was implemented in 1984 in both countries to conserve the breeding stock, but some trawling has been conducted in the Gulf of Papua since then and there is renewed interest in Papua New Guinea to resume trawling. To evaluate the impact of trawling migratory breeding lobsters on the lobster fishery, a model that combines a cohort depletion model with a stock recruitment relationship was developed in this study. The model showed that when the fishery is fully or over‐exploited by the dive fishery, trawling breeding lobsters would reduce both the spawning stock and the total catch of the fishery. The reduction in catch would increase with increasing fishing mortality. If trawling occurred on the Papua New Guinea side only, a redistribution of catch between Australia and Papua New Guinea would result in a small gain in catch for Papua New Guinea at the expense of the Australian dive fishery. But when fishing mortality reaches a certain level, any trawling in any country will incur catch loss to both countries. For the long‐term sustainability and maximum production of the fishery, regulations should be implemented in both countries under a co‐management scheme of a shared fish stock. 相似文献
67.
Bedload sediment transport dynamics in a macrotidal embayment, and implications for export to the southern Great Barrier Reef shelf 总被引:1,自引:0,他引:1
David A. Ryan Brendan P. Brooke Helen C. Bostock Lynda C. Radke Paulus J.W. Siwabessy Nugzar Margvelashvili Darren Skene 《Marine Geology》2007,240(1-4):197-215
Keppel Bay is a macrotidal embayment on a tectonically stable, tropical coast, which links the Fitzroy River with the Great Barrier Reef continental shelf. Estuaries and deltas act as conduits between catchments and inner shelf environments. Therefore, understanding sediment transport pathways in these complex systems is essential for the management of ecosystems such as coral-reefs that are potentially vulnerable to enhanced river sediment loads. Furthermore, the morphology and sediment dynamics of subtidal sand ridges and dunes are relatively poorly characterised in macrotidal estuaries, particularly in turbid, episodic systems such as the Fitzroy River and Keppel Bay. Our sedimentological analysis of seabed samples, shear-stress modelling and three-dimensional acoustic imaging reveals that Keppel Bay is a mixed wave- and tide-dominated estuarine system. Areas of sediment starvation and shoreward transport characterise the offshore zone, whereas a complex of both active and relict tidal sand ridges, and associated subaqueous dunes, dominate the relatively protected southern Keppel Bay. Transport within this region is highly dynamic and variable, with ebb-dominated sediment transport through tidal channels into the outer bay where there is a switch to wave-dominated shoreward transport. Ultimately, bedload sediments appear to be reworked back inshore and to the north, and are gradually infilling the bedrock-defined embayment. Our characterisation of the Keppel Bay system provides a detailed example of the physiography of the seaward portion of a tide-dominated system, and shows that sediment transport in these areas is influenced by a variable hydrodynamic regime as well as relict channels and bedrock topography. 相似文献
68.
Darren K. Hayunga 《International journal of geographical information science》2016,30(12):2339-2354
Mapping spatial processes at a small scale is a challenge when observed data are not abundant. The article examines the residential housing market in Fort Worth, Texas, and builds price indices at the inter- and intra-neighborhood levels. To accomplish our objectives, we initially model price variability in the joint space–time continuum. We then use geostatistics to predict and map monthly housing prices across the area of interest over a period of 4 years. For this analysis, we introduce the Bayesian maximum entropy (BME) method into real estate research. We use BME because it rigorously integrates uncertain or secondary soft data, which are needed to build the price indices. The soft data in our analysis are property tax values, which are plentiful, publicly available, and highly correlated with transaction prices. The results demonstrate how the use of the soft data provides the ability to map house prices within a small areal unit such as a subdivision or neighborhood. 相似文献
69.
Quantitative techniques that link sediments to their sources are needed to understand a range of tectonic, climate, and anthropogenic driven Earth surface processes. Many provenance techniques exist for sand-sized material but fewer are available for fine-grained sediment archives. In this respect, bulk 40Ar/39Ar ages from silt-sized sediment show potential, but many questions remain about the significance of a bulk sediment 40Ar/39Ar age. We interrogate bulk sediment 40Ar/39Ar ages by step heating mixtures of well-constrained 40Ar/39Ar mineral standards crushed to silt-sized. Silt-sized end member components Alder Creek Sanidine, Taylor Creek Sanidine and Heidelberg Biotite all yield plateau ages within uncertainty of their coarse-grained counterparts. High-resolution step heating (as many as 43 steps) of the mineral mixtures shows that biotite degasses first at lower temperatures compared to the two sanidines that degas generally in concert. Concordant age steps develop at both low and high temperatures and the transition from the isotope signal being dominated by one mineral phase to another is clearly observed. We show that age spectra for the mineral standard mixtures can be modeled and predicted for all mixtures by assuming a (simplistic) Gaussian distributed release of Ar, and by using the degassing maxima, variance, K concentration, and 40Ar/39Ar age of each monitor mineral. Thus, bulk sediment 40Ar/39Ar ages can be robust indicators of the average cooling/crystallization age of all contributing K-bearing minerals to a depositional center. Furthermore, we discuss the potential to deconvolve individual mineral age populations by model inversion. The application of this bulk sediment provenance technique should not be considered a replacement for single grain analyses. It should be applied to environments that do not provide sand-sized sediment archives (e.g., distal terrigenous sedimentary archives) when information about source changes through time are more important than precise sediment source identification. 相似文献
70.
Soil particles may be lost through dissolution, degradation or erosion. Regardless of the process of loss, there follows a change in soil structure both in terms of phase composition and grading. In this paper, the influence of size and amount of particle loss on phase composition at two stresses is investigated. The tests are performed on sand–salt mixtures, loaded in a modified permeation oedometer and subsequently dissolved. Changes in overall volume and void ratio are presented. Two significant observations about the volumetric consequences of particle loss can be made. First, overall volume changes are directly related to the amount of dissolved particles and to a lesser extent, the size of particle lost. Second, particle loss leads to an increase in void ratio; the magnitude of the increase is related to the amount of dissolved particles but appears not to be sensitive to either the size of particle lost or the pre-dissolution void ratio. Based on the observed response and a dissolution-induced void change parameter, the influence of different mechanisms of volume change is discussed. Tests were performed at two different vertical stresses with no discernible influence on void ratio change. 相似文献