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1.
Hueiwang Anna C. Jeng Andrew J. Englande Reda M. Bakeer Henry B. Bradford 《Estuarine, Coastal and Shelf Science》2005,63(4):513-526
Urban stormwater runoff could contribute to the deterioration of water quality of a receiving water body. In this research, field studies and laboratory experiments were conducted to assess the microbial contamination resulting from urban stormwater runoff into the Lake Pontchartrain estuary. Fecal coliform, Escherichia coli and enterococci were used as indicator organisms. The specific objectives of the research were to examine the distribution of the indicator organisms in different environmental elements (water column, suspended particles and sediment) and to further investigate the mechanisms related to their fate. Results of the research indicated satisfactory water quality at the study sites during dry weather periods. However, a significant increase was observed in the concentrations of the indicator organisms in the water columns and sediment at specific study sites following a given stormwater event. Three to seven days were needed for the elevated indicator organisms to return back to their background levels in the water column and sediment, respectively. The mechanism of sedimentation contributed to a reduction in the microbial concentration in the water column, as the indicator organisms were found to attach to the suspended particles in the stormwater. The percentage of fecal coliform, E. coli and enterococci attached to the suspended particles was found to be within the range of 9.8–27.5%, 21.8–30.4%, and 8.4–11.5% of the total indicator organisms in the stormwater loaded into the estuary, respectively. About 75–80% of the total indicator organisms remained free-floating for some distance in the water column before dying off. 相似文献
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Modelling the spatial and temporal distribution of rainfall intensity at local scale 总被引:1,自引:0,他引:1
Summary Accurate estimates of rainfall intensity distribution with high temporal and spatial resolution are necessary in most urban hydrological studies, such as planning, simulation or control of sewer networks. Traditionally, these data are obtained from intensity-duration-frequency (IDF) curves at sites with long rainfall intensity time-series, however, little attention is given to the spatial features of precipitation. In this paper, a mathematical model of a local scale storm that takes account of the spatial variability of rainfall and rain-cell movement is proposed. The model has been calibrated with a dense network of raingauges and a long rainfall intensity timeseries (60 years) and its parameters have been calculated for convective storms of return periods up to 15 years with their most frequently-observed rain-cell velocities (1 to 4 m/s).This work has been supported by the DGICYT, Project NAT91-0596.With 6 Figures 相似文献
4.
R. Nieto L. Gimeno J. A. Añel L. De la Torre D. Gallego D. Barriopedro M. Gallego A. Gordillo A. Redaño G. Delgado 《Meteorology and Atmospheric Physics》2007,96(1-2):103-119
Summary The Iberian Peninsula is one of the regions in the world with higher occurrence of cut-off low systems (COL). The aim of this
paper is to analyse the weather events (rainfall and cloudiness layer) associated to COLs in the Iberian Peninsula with tools
not previously used: (a) the use of the new multidecadal COLs database developed by Nieto et al (2005) that permit us to study
a 41 years period (1958–1998), (b) the checking of the expected weather events (rainfall and cloudiness layer) associated
with COLs in a conceptual model (Winkler et al, 2005) and (c) the extensive use of radiosoundings to analyse convective instability
in areas inside and close to the COL. Two points of view are used to make the analysis: (1) a source oriented method, when
a particular COL is followed and its associated precipitation and cloudiness is analysed over four quadrants in which Iberia
was divided and (2) a receptor oriented method, when the precipitation associated to COLs is analysed in given areas, defined
by patterns of precipitation. Results reveal that the precipitation and cloudiness patterns associated to COLs in the conceptual
model reproduce quite well the main characteristics found over the Iberian Peninsula. The generalized idea that most of the
COLs produce intense convective rainfall is show to be misleading. Convective phenomena are important usually when the centre
of the COL is located on the Mediterranean region. Most of the rainfall associated with COLs comes from the baroclinic shield;
specially in cases located over the west half of the Iberian Peninsula. It is shown that nearly 30% of COLs do not induce
any rainfall; most of them located in the southern half of the Peninsula, and mainly during autumn. Only 30% of COLs produce
generalized rainfall over the whole analysed territory, being most of them (about 90%) located over the western half of the
Iberian Peninsula. 相似文献
5.
B. Diab 《Engineering Geology》1976,10(2-4):283-292
This paper shows by means of a numerical example and using the finite-element method that the diminution of the strain energy of a reservoir rock foundation in consequence of the failure of joints may be equivalent to the energy released by an earthquake of magnitude 6. 相似文献
6.
A. A. Zhamaletdinov A. N. Shevtsov E. P. Velikhov A. A. Skorokhodov V. E. Kolesnikov T. G. Korotkova P. A. Ryazantsev B. V. Efimov V. V. Kolobov M. B. Barannik P. I. Prokopchuk V. N. Selivanov Yu. A. Kopytenko E. A. Kopytenko V. S. Ismagilov M. S. Petrishchev P. A. Sergushin P. E. Tereshchenko B. V. Samsonov M. A. Birulya M. Yu. Smirnov T. Korja Yu. M. Yampolski A. V. Koloskov N. A. Baru S. V. Poljakov A. V. Shchennikov G. I. Druzhin W. Jozwiak J. Reda Yu. G. Shchors 《Izvestiya Atmospheric and Oceanic Physics》2015,51(8):826-857
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In most of the studies on scale properties in the rainfall process, multifractal behavior has been investigated without taking into account the different rain generation mechanisms involved. However, it is known that rain processes are related to certain scales, determined by climatological characteristics as well as regional and local meteorological features. One of the implications derived from these correspondences is the possibility that the multifractal parameters of the rainfall could depend on the dominant precipitation generation mechanism. Fractal analysis techniques have been applied in this work to rainfall data recorded in the metropolitan area of Barcelona in the period 1994–2001, as well as to a selection of synoptic rainfall events registered in the same city in the period 1927–1992. The multifractal parameters obtained have been significantly different in each case probably showing the influence of the rain generation mechanisms involved. This influence has been revealed also in the analysis of the effects of seasonality on the multifractal behavior of rainfall in Barcelona. 相似文献
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Adaptive analysis of infinite beams dynamics problems using the periodic configuration update method in the time domain 下载免费PDF全文
This paper proposes a new approach for the assessment of the dynamic response of continuously supported infinite beams under high‐speed moving loads. A change in the representation of equations of motion in the dynamics of discrete structures is proposed to obtain an improved accuracy of the numerical integration in the time domain. The proposed numerical method called the “periodic configuration update” or “PCU method” is applied to solve the problem of a vertical moving harmonic load on an infinite classical Euler‐Bernoulli beam resting on a continuous viscoelastic foundation. This study shows the superiority of the proposed method in comparison with other methods presented in the literature that suffer from the material time derivative, i.e., convective terms, that arises from the Galilean transformation. To confront this numerical problem, the PCU method retains the principle of the spatial follow of loads while zeroing the relative velocity with the traversed beam via a step‐by‐step adaptive integration of the equation of structural dynamics. The dynamic load is modeled with high theoretical velocities that can reach the critical velocity of the studied beam with different angular frequencies belonging to moderate frequency range. A parametric study is carried out to analyze the influence of key parameters on the convergence. The obtained results show a high efficiency of the PCU method for solving these types of problems relative to the dynamics of high speed trains/tracks. 相似文献