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181.
Vegetation and hydraulic-morphological interactions at the individual plant, patch and channel scale
Interactions between vegetation, flow and sediment are a key ingredient for the development of vegetated islands in highly
dynamic, fluvial alpine ecosystems such as the Tagliamento River, north-east Italy. There has been substantial research on
factors influencing the establishment of vegetation and feedback mechanisms between vegetation, hydraulic, and geomorphological
processes in such environments. This has yielded the development of conceptual models identifying different trajectories of
vegetation and landform development from bare gravel to established floodplain forest. Nevertheless, some of the finer-scale
processes underpinning such interactions are not well understood and parameterisation concepts that augment our knowledge
from process understanding to quantified data and prediction models are not available until now. This paper identifies mechanisms
and parameters of vegetation-flow interaction at the individual scale that are reflected at a patch or even at the channel
scale. These mechanisms are reviewed from a multi-disciplinary perspective and concepts and analogies are proposed that provide
ideas to progress research towards the development of predictive vegetation-flow models. Such models must incorporate both
hydraulic and ecological components and this is demonstrated for a simplified force-bending model of Salicaceae seedlings.
The development of such models demands advances in the individual disciplines of hydraulics, morphology, plant ecology and
biomechanics, which offers many possibilities for multidisciplinary research between these disciplines. 相似文献
182.
A comparison of seismic risk maps for Italy 总被引:5,自引:3,他引:2
Helen Crowley Miriam Colombi Barbara Borzi Marta Faravelli Mauro Onida Manuel Lopez Diego Polli Fabrizio Meroni Rui Pinho 《Bulletin of Earthquake Engineering》2009,7(1):149-180
National seismic risk maps are an important risk mitigation tool as they can be used for the prioritization of regions within
a country where retrofitting of the building stock or other risk mitigation measures should take place. The production of
a seismic risk map involves the convolution of seismic hazard data, vulnerability predictions for the building stock and exposure
data. The seismic risk maps produced in Italy over the past 10 years are compared in this paper with recent proposals for
seismic risk maps based on state-of-the-art seismic hazard data and mechanics-based vulnerability assessment procedures. The
aim of the paper is to open the discussion for the way in which future seismic risk maps could be produced, making use of
the most up-to-date information in the fields of seismic hazard evaluation and vulnerability assessment. 相似文献
183.
Lynda C. Howard Paul J. Wood Malcolm T. Greenwood Helen M. Rendell 《Journal of Paleolimnology》2009,42(4):453-466
Sub-fossil insect remains have the potential to characterise changing environmental conditions in both lentic and lotic water
systems, however, relatively few studies have been undertaken in riverine environments. This paper uses sub-fossil caddisfly
larvae (Trichoptera) and aquatic beetles (Coleoptera) to reconstruct river flow conditions for a large paleochannel (from
multiple monoliths) using the Lotic invertebrate Index for Flow Evaluation (LIFE). Examination of the larval Trichoptera and
Coleoptera remains indicated a marked change in the community and flow environment, as suggested by paleoLIFE scores within
the profile of three of the monoliths examined. At the base of the channel the community was characterised by taxa indicative
of high energy lotic habitats with predominantly mineral substrates (e.g. Trichoptera: Hydropsyche
contubernalis and Brachycentrus
subnubilis, Coleoptera: Elmis
aenea and Esolus
parallelepipedus). Within three of the monoliths there was a change in community composition to one indicative of a low energy backwater/lentic
environment with abundant submerged and emergent vegetation (e.g. Trichoptera: Phryganea
bipunctata and Limnephilus
flavicornis, Coleoptera: Colymbetes
fuscus and Hydrobius
fuscipes). Detrended Correspondence Analysis (DCA) and loss of mass on ignition (LOI) indicated the presence of a strong environmental
gradient within the data, associated with river flow. The utilisation of two aquatic insect orders provides clear evidence
of temporal changes within the instream community and when combined with knowledge of ecological and habitat associations,
allows differences between the two groups to be interpreted more clearly. 相似文献
184.
Development and assessment of damage‐to‐loss models for moment‐frame reinforced concrete buildings
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Luís Martins Vítor Silva Mário Marques Helen Crowley Raimundo Delgado 《地震工程与结构动力学》2016,45(5):797-817
The assessment of earthquake loss often requires the definition of a relation between a measure of damage and a quantity of loss, usually achieved through the employment of a damage‐to‐loss model. These models are frequently characterized by a large variability, which inevitably increases the uncertainty in the vulnerability assessment and earthquake loss estimation. This study provides an insight on the development of damage‐to‐loss functions for moment‐frame reinforced concrete buildings through an analytical methodology. Tri‐dimensional finite element models of existing reinforced concrete buildings were subjected to a number of ground motion records compatible with the seismicity in the region of interest, through nonlinear dynamic analysis. These results were used to assess, for a number of damage states, the probability distribution of loss ratio, taking into consideration member damage and different repair techniques, as well as to derive sets of fragility functions. Then, a vulnerability model (in terms of the ratio of cost of repair to cost of replacement, conditional on the level of ground shaking intensity) was derived and compared with the vulnerability functions obtained through the combination of various damage‐to‐loss models with the set of fragility functions developed herein. In order to provide realistic estimates of economic losses due to seismic action, a comprehensive study on repair costs using current Portuguese market values was also carried out. The results of this study highlight important issues in the derivation of vulnerability functions, which are a fundamental component for an adequate seismic risk assessment. © 2015 The Authors. Earthquake Engineering & Structural Dynamics published by John Wiley & Sons Ltd. 相似文献
185.
Helen M. Roe G. Russell Coope Robert J.N. Devoy Colin J.O. Harrison Kirsty E.H. Penkman Richard C. Preece Danielle C. Schreve 《Quaternary Science Reviews》2009,28(23-24):2342-2373
Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2 °C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus, appears to have formed during the Ipswichian (MIS 5e). This evidence is compared with other important sites of late Middle Pleistocene age in Britain and elsewhere on the continent and the importance of a multidisciplinary approach is stressed. 相似文献
186.
W. Todd Jarvis 《Ground water》2010,48(3):346-350
187.
The Pacific island nation-state of Tuvalu featured significantly at the Copenhagen Conference of Parties (COP) 15 climate change negotiations, where the vulnerability of Tuvalu to sea level rise and emotional outpourings of the Tuvaluan delegation contributed to the nation's prominence. In this paper we discuss the likely impacts for Tuvalu of a 1.5°C versus 2°C global warming target and explore sadness and discomfort surrounding discussion of these targets during COP 15. We highlight tensions between science and emotion, arguing that affective encounters can be significant in climate change decision-making. Weeping by a member of the Tuvalu delegation evoked discomfort in the conference plenary. This discomfort briefly unsettled the apparently stable boundaries of convention and protocol that seek to separate emotion from science and politics. We argue that possibilities for change arise when emotions enter climate change negotiations, even though (or perhaps because) these are arenas that privilege rational exchange. Our conclusion urges that more attention be paid to how climate science and emotion are intertwined in climate change politics. 相似文献
188.
The low detection limits and multi‐element capability of inductively coupled plasma‐mass spectrometry (ICP‐MS) makes it an attractive option in a wide range of environmental, medical, biological, industrial and archaeological applications. Quadrupole ICP‐MS is used to determine element concentrations in a diverse range of sample types, often very different from the geological applications for which ICP‐MS was originally developed. Whilst modern instruments are robust and capable of a high degree of automation, it is essential that users of both instrumentation and data are aware of the strengths and limitations of the technique. Many people who are now involved with the operation and application of ICP‐MS instruments are not specialists in the field, as was usually the case amongst early operators. This back‐to‐basics review is aimed at the novice user and includes a guide to ICP‐MS instrumentation and performance. Whilst solids, liquids and gases can all be measured by ICP‐MS, discussion of sample introduction is limited to liquids. Requirements for producing good quality data, including aspects of sample preparation, calibration, and methods of interference limitation are also discussed. 相似文献
189.
Deformation-related microstructures in magmatic zircon and implications for diffusion 总被引:1,自引:1,他引:0
Steven Michael Reddy Nicholas E. Timms Patrick Joseph Hamilton Helen R. Smyth 《Contributions to Mineralogy and Petrology》2009,157(2):231-244
An undeformed glomeroporphyritic andesite from the Sunda Arc of Java, Indonesia, contains zoned plagioclase and amphibole
glomerocrysts in a fine-grained groundmass and records a complex history of adcumulate formation and subsequent magmatic disaggregation.
A suite of xenocrystic zircon records Proterozoic and Archaean dates whilst a discrete population of zoned, euhedral, igneous
zircon yields a SHRIMP U-Pb crystallisation age of 9.3 ± 0.2 Ma. Quantitative microstructural analysis of zircon by electron
backscatter diffraction (EBSD) shows no deformation in the inherited xenocrysts, but intragrain orientation variations of
up to 30° in 80% of the young zircon population. These variations are typically accommodated by both progressive crystallographic
bending and discrete low angle boundaries that overprint compositional growth zoning. Dispersion of crystallographic orientations
are dominantly by rotation about an axis parallel to the zircon c-axis [001], which is coincident with the dominant orientation of misorientation axes of adjacent analysis points in EBSD
maps. Less common <100> misorientation axes account for minor components of crystallographic dispersion. These observations
are consistent with zircon deformation by dislocation creep and the formation of tilt and twist boundaries associated with
the operation of <001>{100} and <100>{010} slip systems. The restriction of deformation microstructures to large glomerocrysts
and the young magmatic zircon population, and the absence of deformation within the host igneous rock and inherited zircon
grains, indicate that zircon deformation took place within a low-melt fraction (<5% melt), mid-lower crustal cumulate prior
to fragmentation during magmatic disaggregation and entrainment of xenocrystic zircons during magmatic decompression. Tectonic
stresses within the compressional Sunda Arc at the time of magmatism are considered to be the probable driver for low-strain
deformation of the cumulate in the late stages of initial crystallisation. These results provide the first evidence of crystal
plastic dislocation creep in zircon associated with magmatic crystallisation and indicate that the development of crystal-plastic
microstructures in zircon is not restricted to high-strain rocks. Such microstructures have previously been shown to enhance
bulk diffusion of trace elements (U, Th and REE) in zircon. The development of deformation microstructures, and therefore
multiple diffusion pathways in zircon in the magmatic environment, has significant implications for the interpretation of
geochemical data from igneous zircon and the trace element budgets of melts due to the potential enhancement of bulk diffusion
and dissolution rates. 相似文献
190.
Roberto Soria Kinwah Wu Helen M. Johnston 《Monthly notices of the Royal Astronomical Society》1999,310(1):71-77
We carried out spectroscopic observations of the candidate black hole binary GX 339−4 during its low–hard and high–soft X-ray states. We have found that the spectrum is dominated by emission lines of neutral elements with asymmetric, round-topped profiles in the low–hard state. In the high–soft state, however, the emission lines from both neutral and ionized elements have unambiguously resolved double-peaked profiles. The detection of double-peaked emission lines in the high–soft state, with a larger peak separation for higher ionization lines, indicates the presence of an irradiatively heated accretion disc. The round-topped lines in the low–hard state are probably caused by a dense matter outflow from an inflated non-Keplerian accretion disc. Our data do not show velocity modulations of the line centres caused by the orbital motion of the compact object, neither do the line basewidths show substantial variations in each observational epoch. There are no detectable absorption lines from the companion star. All these features are consistent with those of a system with a low-mass companion star and low orbital inclination. 相似文献