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61.
The University of California Observatories/Lick Observatory (UCO/Lick) has undertaken to produce science-grade CCDs for current and future instruments to be used on UCO/Lick and UCO/Keck telescopes. In this paper we describe the techniques developed and the progress achieved to date. 相似文献
62.
Melinda M. Taylor & Andrew J. Booth 《Monthly notices of the Royal Astronomical Society》1998,298(2):594-600
A new high-accuracy velocity curve is presented for the bright southern Cepheid β Doradus (HR 1922), and an investigation into the long-term stability of the velocity curve is made. An upper limit of 0.57 km s−1 is placed on cycle-to-cycle variations. This work is compared with a similar analysis previously applied to the long-period Cepheid ℓ Carinae (HR 3884). Using a near-infrared variant of the Barnes–Evans method, the mean radius of and distance to β Dor are found to be R = 67.8 ± 0.7 R⊙ and d = 349 ± 4 pc. The systematic errors in these parameters are less than 3 per cent. If these systematics can be resolved, through the development of advanced theoretical models and/or the direct measurement of angular diameters, a calibration of the cosmic distance scale to better than 1 per cent can be achieved. 相似文献
63.
We present an edge-on Keplerian disk model to explain the main component of the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1N. The brightness distribution and spectrum of the line of bright masers are successfully modeled with high amplification of background radio continuum emission along velocity coherent paths through a maser disk. The bend seen in the position–velocity diagram is a characteristic signature of differentially rotating disks. For a central mass of 30M, suggested by other observations, our model fixes the masing disk to have inner and outer radii of 270 and 750 AU. 相似文献
64.
The Global Earthquake Vulnerability Estimation System (GEVES): an approach for earthquake risk assessment for insurance applications 总被引:4,自引:0,他引:4
Robin Spence Emily So Sarah Jenny Hervé Castella Michael Ewald Edmund Booth 《Bulletin of Earthquake Engineering》2008,6(3):463-483
For the insurance and reinsurance industries, earthquake loss estimation is crucial not only to adequately price its product
but also to manage the accumulation risk in the face of the ever-increasing exposure in highly seismic regions. Changes in
the built environment and a continuously evolving earthquake science make it a necessity for the industry to constantly refine
earthquake loss estimation models. In particular, it has been recognized for a long time that the vulnerability of buildings
to ground shaking is a key parameter in any earthquake risk model. Current methods tend either to rely on the limited historical
damage and loss data or on the numerical simulation of the response of individual buildings to the ground-shaking produced
by earthquakes. Although both methods have their advantages and pitfalls, we are proposing here a simple solution, using transparent
input data, that can be realistically used for the needs of the insurance and reinsurance industry, whether detailed information
about the insured structures is available or not. The resulting product is known as GEVES (Global Earthquake Vulnerability
Estimation System). It is primarily intended for evaluating the mean damage ratio (MDR) suffered by a portfolio of buildings
classified by use, under the action of a given earthquake scenario (i.e. an earthquake of given size at a given distance from
the portfolio of buildings). A key assumption was that macroseismic intensity rather than spectral displacement would be the
basis of loss estimation. The paper describes the model with emphasis on its structure and the justification for the assumptions
made. In addition to a new set of earthquake vulnerability functions, the paper also provides recommendations on some aspects
of the earthquake hazard, in particular about how to define macroseismic intensity at the site of interest, for a given earthquake
scenario. This paper also discusses validation of the GEVES model against calculated vulnerability approaches, and the treatment
of uncertainty within the model. 相似文献
65.
The influence of urbanization on the temperature of small streams is widely recognized, but these effects are confounded by the great natural variety of their contributing watersheds. To evaluate the relative importance of local‐scale and watershed‐scale factors on summer temperatures in urban streams, hundreds of near‐instantaneous temperature measurements throughout the central Puget Lowland, western Washington State, were collected during a single 2‐h period in August in each of the years 1998–2001. Stream temperatures ranged from 8.9 to 27.5 °C, averaging 15.4 °C. Pairwise correlation coefficients between stream temperature and four watershed variables (total watershed area and the watershed percentages of urban development, upstream lakes, and permeable glacial outwash soils as an indicator of groundwater exchange) were uniformly very low. Akaike's information criterion was applied to determine the best‐supported sets of watershed‐scale predictor variables for explaining the variability of stream temperatures. For the full four‐year dataset, the only well‐supported model was the global model (using all watershed variables); for the most voluminous single‐year (1999) data, Akaike's information criterion showed greatest support for per cent outwash (Akaike weight of 0.44), followed closely by per cent urban development + per cent outwash, per cent lake area only, and the global model. Upstream lakes resulted in downstream warming of up to 3 °C; variability in riparian shading imposed a similar temperature range. Watershed urbanization itself is not the most important determining factor for summer temperatures in this region; even the long‐recognized effects of riparian shading can be no more influential than those imposed by other local‐scale and watershed‐scale factors. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
66.
67.
Andrew R. Farrant Peter M. Hopson Mark A. Woods Kathryn A. Booth David J. Evans 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(3):533-536
The Chalk Group of the Central Downs of the Isle of Wight forms a relay ramp between two major inverted extensional faults. Mortimore (2011) presented a structural model of this key area based on a geological map constructed from detailed logging of a limited set of exposed sections. The area has been recently mapped at 1:10,000 scale by the British Geological Survey. Our interpretation of the geological structure differs significantly from that proposed by Mortimore, and suggests that Chalk has relatively uniform dips that progressively steepen towards the hanging wall of the E-W oriented basement faults. However, a suite of mapped extensional faults indicates an element of differential movement or transpression along the main basement structures. 相似文献
68.
The amplitude spectrum of ground penetrating radar (GPR) reflection data acquired with a particular antenna set is normally concentrated over a spectral bandwidth of a single octave, limiting the resolving power of the GPR wavelet. Where variously-sized GPR targets are located at numerous depths in the ground, it is often necessary to acquire several profiles of GPR data using antennas of different nominal frequencies. The most complete understanding of the subsurface is obtained when those frequency-limited radargrams are jointly interpreted, since each frequency yields a particular response to subsurface reflectivity. The application of deconvolution to GPR data could improve image quality, but is often hindered by limited spectral bandwidth.We present multiple-frequency compositing as a means of combining data from several frequency-limited datasets and improving the spectral bandwidth of the GPR profile. A multiple-frequency composite is built by summing together a number of spatially-coincident radargrams, each acquired with antennae of different centre frequency. The goal of the compositing process is therefore to produce a composite radargram with balanced contributions from frequency-limited radargrams and obtain a composite wavelet that has properties approximating a delta function (i.e. short in duration and having a broad, uniform spectral bandwidth).A synthetic investigation of the compositing process was performed using Berlage wavelets as proxies for GPR source pulses. This investigation suggests that a balanced, broad bandwidth, effective source pulse is obtained by a compositing process that equalises the spectral maxima of frequency-limited wavelets prior to summation into the composite. The compositing of real GPR data was examined using a set of 225, 450 and 900 MHz GPR common offset profiles acquired at a site on the Waterloo Moraine in Ontario, Canada. The most successful compositing strategy involved derivation of scaling factors from a time-variant least squares analysis of the amplitude spectra of each frequency-limited dataset. Contributions to the composite from each nominal acquisition frequency are clear, and the trace averaged amplitude spectrum of the corresponding composite is broadened uniformly over a bandwidth approaching two-octaves. Improvements to wavelet resolution are clear when a composite radargram is treated with a spiking deconvolution algorithm. Such improvement suggests that multiple-frequency compositing is a useful imaging tool, and a promising foundation for improving deconvolution of GPR data. 相似文献
69.
Developing appropriate climate change adaptations to protect biodiversity requires taking into account the dynamics of agro-ecological and socio-economic change. A framework for approaching this problem was proposed, but not applied in detail, as part of a major biodiversity and climate change report prepared in Australia. This paper describes the first trial application of the method. It was applied across Vietnam as the Government is interested in identifying adaptation options and detailed data are readily available for its 65 provinces. The process involves identifying ecoregions and collating information for each region based on the current conditions and trends in biodiversity, population, income and agricultural production. Climate change scenarios are identified for each region, together with governance options. Educational needs and key adaptation actions are then identified for each region taking into account the agro-ecological and socio-economic input data. It is concluded that the framework could easily be applied in other countries and should assist the development of strategic adaptation options. 相似文献
70.