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171.
The presence of chemical contaminants in marine coastal waters is a major subject of concern since many molecules are potentially immunotoxic, even at low concentration. During the last decade, studies in sentinel species, such as the blue mussel, Mytilus edulis, or the Pacific oyster, Crassostrea gigas, have revealed that immunosuppressive responses can be related to xenobiotic exposure, in the laboratory and in the field. In the present study, European flat oysters were experimentally exposed to heavy metals, to investigate possible alterations of their immune function. Several hematological and functional parameters of hemocytes were measured by flow cytometry, a technique allowing rapid, sensitive, cell-by-cell measurements in large cell populations. Results reveal a depression of phagocytosis and several subcellular, physiological changes in oysters exposed to cadmium alone or to cadmium and copper, suggesting an overall alteration of the phagocytic function. 相似文献
172.
Terlizzi A Bevilacqua S Scuderi D Fiorentino D Guarnieri G Giangrande A Licciano M Felline S Fraschetti S 《Marine pollution bulletin》2008,56(7):1303-1309
The exploitation of fossil fuels in the Mediterranean Sea will likely lead to an increase in the number of offshore platforms, a recognized threat for marine biodiversity. To date, in this basin, few attempts have been made to assess the impact of offshore gas and oil platforms on the biodiversity of benthic assemblages. Here, we adopted a structured experimental design coupled with high taxonomic resolution to outline putative effects of gas platforms on soft-bottom macrofauna assemblages in the North Ionian Sea. The analysis was based on a total of 20,295 specimens of 405 taxa, almost entirely identified at species level. Multivariate and univariate analyses showed idiosyncratic patterns of assemblage change with increasing distance from the platforms. Potential reasons underlying such inconsistency are analyzed and the view that structured experimental monitoring is a crucial tool to quantify the extent and magnitude of potential threats and to provide sound baseline information on biodiversity patterns is supported. 相似文献
173.
Dario Dello Iacono Aldo Zollo Maurizio Vassallo Tiziana Vanorio Sebastien Judenherc 《Bulletin of Volcanology》2009,71(3):275-284
In September 2001, an extensive active-seismic investigation (Serapis experiment) was carried out in the Gulfs of Naples and
Pozzuoli, with the aim of investigating and reconstructing the shallow crustal structure of the Campi Flegrei caldera, and
possibly identifying its feeding system at depth. The present study provides a joint analysis of the very shallow seismic
reflection data and tomographic images based on the Serapis dataset. This is achieved by reflection seismic sections obtained
by the 3D data gathering and through refined P-velocity images of the shallowest layer of Pozzuoli Gulf (z < 1,000 m). From the refined Vp model, the overall picture of the velocity distribution confirms the presence of a complex
arc-shaped anomaly that borders the bay offshore. The deeper part of the anomaly (beneath 700 m, with Vp > 3,500 m/s) correlates
with units made up of agglomerate tuffs and interbedded lava, which form the southern edge of the caldera, which was probably
formed following the two large ignimbritic eruptions that marked the evolutionary history of the area under study. The upper
part of the anomaly that tends to split into two parallel arcs is correlated with dikes, volcanic mounds and hydrothermal
alteration zones noted in previous shallow reflection seismic analyses. The depth of the transition between the upper and
lower parts of the anomaly is characterized by an abrupt Vp increase on the one-dimensional (1D) profiles extracted from the
3D tomographic model and by the presence of a strong reflector located at about 0.6/0.7 s Two Way Time (TWT) on Common Mid
Point gathers. The move-out velocity analysis and stack of the P–P and P–S reflections at the layer bottom allowed to estimate
relatively high Vp/Vs values (3.7 ± 0.9). This hypothesis has been tested by a theoretical rock physical modeling of the Vp/Vs
ratio as a function of porosity suggesting that the shallow layer is likely formed by incoherent, water saturated, volcanic
and marine sediments that filled Pozzuoli Bay during the post-caldera activity. 相似文献
174.
Dario Camuffo Caterina Secco Peter Brimblecombe Javier Martin-Vide 《Climatic change》2000,46(1-2):209-223
Data regarding the frequency andoccurrence of sea storms in the Adriatic Sea and theWestern Mediterranean during the last millennium havebeen extracted from historical written sources. TheAdriatic Sea shows two anomalous periods of high stormfrequency: the first half of the 1500s and the secondhalf of the 1700s. In the 1500s the storms were morefrequent in autumn, while in the late 1700s theyoccurred at high frequency in winter. In the WesternMediterranean, storms had a higher frequency in thefirst half of the 1600s, with two lesser periods ofhigh frequency in the 1400s and at the end of the1700s. Although both records show a maximum frequencyof sea storms during the Spörer Minimum(1416–1534) of solar activity, sunspot series yieldno, or poor, correlation during the other periods oflowest activity, i.e., Oort Minimum (1010–1090), WolfMinimum (1282–1342), and Maunder Minimum (1645–1715),suggesting that a teleconnection between sea stormsand sunspots is improbable or masked in this region.No teleconnection was found either between the ElNiño-Southern Oscillation (ENSO) and surgesflooding Venice or the Western Mediterranean storms orbetween Venice surges and the Northern AtlanticOscillation (NAO). 相似文献
175.
Dario TERRIBILINI Otto EUGSTER David W. MITTLEFEHLDT Larryn W. DIAMOND Stephan VOGT Daode WANG 《Meteoritics & planetary science》2000,35(3):617-628
Abstract— We performed a comprehensive study of the noble gas isotopic abundances, radionuclide activities, and mineralogical and chemical composition of two mesosiderites and two iron meteorites. For the mesosiderites Dong Ujimqin Qi and Weiyuan, the silicate and the metal phases were studied. The anomalous ataxite Rafrüti is not chemically related to any other meteorite class, whereas Ningbo is a type IVA octahedrite. The mineralogy and major and trace element abundances of the silicate phases of Dong Ujimqin Qi and Weiyuan are similar to those of other mesosiderites and distinct from those of the howardites. The cosmic‐ray exposure history was studied based on the concentrations of the cosmogenic noble gas nuclei and radionuclide activities. For the iron meteorites, cosmic‐ray exposure ages were calculated from the pairs 10Be‐21Ne, 26Al‐21Ne, and 36Cl‐36Ar. Rafrüti yields the youngest exposure age of all ataxites (6.8 ± 1.7 Ma), whereas that of Ningbo with 107 ± 15 Ma falls within the range observed for the other octahedrites. The parent body break‐up times of the mesosiderites Dong Ujimqin Qi and Weiyuan are 252 ± 50 and 25.9 ± 5.0 Ma, respectively. We find no evidence for a common break‐up event for the mesosiderites and the howardites. 相似文献
176.
Alternative interpretations of horizontal to vertical spectral ratios of ambient vibrations: new insights from theoretical modeling 总被引:2,自引:1,他引:1
Different positions exist about the physical interpretation of horizontal to vertical spectral ratios (HVSR) deduced from
ambient vibrations. Two of them are considered here: one is based on the hypothesis that HVSR are mainly conditioned by body
waves approaching vertically the free surface, the other one assumes that they are determined by surface waves (Rayleigh and
Love, with relevant upper modes) only. These interpretations can be seen as useful approximations of the actual physical process,
whose reliability should be checked case-by-case. To this purpose, a general model has been here developed where ambient vibrations
are assumed to be the complete wave field generated by a random distribution of independent harmonic point sources acting
at the surface of a flat stratified visco-elastic Earth. Performances of the approximate interpretations and complete wave
field models have been evaluated by considering a simple theoretical subsoil configuration and an experimental setting where
measured HVSR values were available. These analyses indicate that, at least as concerns the subsoil configurations here considered,
the surface-waves approximation seems to produce reliable results for frequencies larger than the fundamental resonance frequency
of the sedimentary layer. On the other hand, the body waves interpretation provides better results around the resonance frequency.
It has been also demonstrated that the HVSR curve is sensitive to the presence of a source-free area around the receiver and
that most energetic contribution of the body waves component comes from such local sources. This dependence from the sources
distribution implies that, due to possible variations in human activities in the area where ambient vibrations are carried
on, significant variations are expected to affect the experimental HVSR curve. Such variations, anyway, only weakly affect
the location of HVSR maximum that confirms to be a robust indicator (in the range of 10%) of the local fundamental resonance
frequency. 相似文献
177.
178.
In a companion paper two different modelling approaches have been described, operating at the meso‐scale of the fibre elements and at the micro‐scale of the finite element (FE) method. The aim of this paper is to explore the efficiency of these models in the pushover analysis for the seismic assessment of existing reinforced concrete (RC) structures. To this purpose a prototype reference structure, one of the RC shear walls designed according to the multi‐fuse concept and tested on shaking table for the CAMUS Project, is modelled at different levels of refinement. At the micro‐scale the reinforcement and anchorage details are described with increasing accuracy in separate models, whereas at the meso‐scale one single model is used, where each element represents a large part of the structure. Static incremental non‐linear analyses are performed with both models to derive a capacity curve enveloping the experimental results and to reproduce the damage pattern at the displacement level where failure is reached. The comparison between experimental and numerical results points out the strong and weak points of the different models inside the procedure adopted, and the utility of an integration of results from both approaches. This study confirms, even for the rather difficult case at study, the capability of the pushover in reproducing the non‐linear dynamic response, both at a global and a local level, and opens the way to the use of the models within a displacement‐based design and assessment procedure. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
179.
Bo. R. Larsen Dario Di Bella Marianne Glasius Richard Winterhalter Niels R. Jensen Jens Hjorth 《Journal of Atmospheric Chemistry》2001,38(3):231-276
Smog chamber experiments have beenconducted in which cyclic monoterpenes were oxidisedin the gas phase by OH. The evolved secondary organicaerosol (SOA) was analysed by LC-MSn and thegas-phase products were analysed by FT-IR. Theconcentrations of the identified compoundscorresponded to carbon mass balances in the range of40%–90%. The identified compounds in the particularphase corresponded to 0.5%–4.2% of the reactedcarbon. The most abundant compounds in SOA fromterpenes with an endocyclic C=C double bond wereC10-keto-aldehydes, C10-keto-carboxylicacids, C10-hydroxy-keto-carboxylic acids, andC10-hydroxy-keto-aldehydes (pinonaldehyde,pinonic acid, hydroxy-pinonic acid isomers, andhydroxy-pinonaldehyde isomers from -pinene;3-caronaldehyde, 3-caronic acid, hydroxy-3-caronicacid isomers, and hydroxy-3-caronaldehyde isomers from3-carene). The most abundant compounds in SOA fromterpenes with an exocyclic C=C double bond wereC9-ketones, C9-dicarboxylic acids, andC10-hydroxy-keto-carboxylic acids (nopinone,pinic acid, and hydroxy-pinonic acid isomers from-pinene; sabinaketone, sabinic acid andhydroxy-sabinonic acid isomers from sabinene).Decarboxylated analogues of most of the compounds werepresent in SOA in minor concentrations, such asC9-keto-carboxylic acids (norpinonic acid,nor-3-caronic acid) and C8-dicarboxylic acids(norpinic acid, nor-3-caric acid, norsabinic acid). InSOA from limonene, which contains an endocyclic aswell as an exocyclic C=C double bond, the mostabundant compounds were a C10-keto-aldehyde andits oxo-derivative (limononaldehyde and keto-limononaldehyde) together with hydroxy-derivatives of aC10-keto-carboxylic acid (isomers ofhydroxy-limononic acid). Also aC10-keto-carboxylic acid (limononic acid) waspresent together with minor concentrations of aC9-dicarboxylic acids (limonic acid), itsoxo-derivative (keto-limonic acid), and itsdecarboxylated analogue (norlimonic acid). Mechanisticpathways for the formation of these products, some ofwhich are identified here for the first time, areproposed. 相似文献
180.
A discrete model to represent the unbounded soil (halfspace) in a soil–structure interaction analysis in the time domain is developed. For each dynamic degree of freedom of the foundation node, the discrete model consists of a mass M0 which is attached to a rigid support with a spring K and with a damper C0. In addition, a free node with the mass M1 is introduced, which is connected to the foundation node with a damper C1. All coefficients are frequency-independent. The discrete model is semi-empirical. It is based on a semi-infinite truncated cone, whereby, after enforcing the static stiffness, the remaining parameters are modified to achieve an optimal fit of the dynamic-stiffness coefficient in the frequency domain. The spring K is equal to the static stiffness. The coefficients appearing in the equations for the dampers C0, C1 and the masses M0, M1 are specified (assuming a homogeneous halfspace) for the disc, the embedded cylinder, the rectangle (also embedded) and the strip. A square on a layer whose stiffness increases with depth resting on a homogeneous halfspace is also treated. For an embedded foundation, eccentricities arise. Material damping increases the damper C0 and the mass M0. 相似文献