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81.
In recent decades, the need of future climate information at local scales have pushed the climate modelling community to perform increasingly higher resolution simulations and to develop alternative approaches to obtain fine-scale climatic information. In this article, various nested regional climate model (RCM) simulations have been used to try to identify regions across North America where high-resolution downscaling generates fine-scale details in the climate projection derived using the “delta method”. Two necessary conditions were identified for an RCM to produce added value (AV) over lower resolution atmosphere-ocean general circulation models in the fine-scale component of the climate change (CC) signal. First, the RCM-derived CC signal must contain some non-negligible fine-scale information—independently of the RCM ability to produce AV in the present climate. Second, the uncertainty related with the estimation of this fine-scale information should be relatively small compared with the information itself in order to suggest that RCMs are able to simulate robust fine-scale features in the CC signal. Clearly, considering necessary (but not sufficient) conditions means that we are studying the “potential” of RCMs to add value instead of the AV, which preempts and avoids any discussion of the actual skill and hence the need for hindcast comparisons. The analysis concentrates on the CC signal obtained from the seasonal-averaged temperature and precipitation fields and shows that the fine-scale variability of the CC signal is generally small compared to its large-scale component, suggesting that little AV can be expected for the time-averaged fields. For the temperature variable, the largest potential for fine-scale added value appears in coastal regions mainly related with differential warming in land and oceanic surfaces. Fine-scale features can account for nearly 60 % of the total CC signal in some coastal regions although for most regions the fine scale contributions to the total CC signal are of around ~5 %. For the precipitation variable, fine scales contribute to a change of generally less than 15 % of the seasonal-averaged precipitation in present climate with a continental North American average of ~5 % in both summer and winter seasons. In the case of precipitation, uncertainty due to sampling issues may further dilute the information present in the downscaled fine scales. These results suggest that users of RCM simulations for climate change studies in a delta method framework have little high-resolution information to gain from RCMs at least if they limit themselves to the study of first-order statistical moments. Other possible benefits arising from the use of RCMs—such as in the large scale of the downscaled fields– were not explored in this research. 相似文献
82.
Probabilistic estimates of future changes in California temperature and precipitation using statistical and dynamical downscaling 总被引:1,自引:0,他引:1
David W. Pierce Tapash Das Daniel R. Cayan Edwin P. Maurer Norman L. Miller Yan Bao M. Kanamitsu Kei Yoshimura Mark A. Snyder Lisa C. Sloan Guido Franco Mary Tyree 《Climate Dynamics》2013,40(3-4):839-856
Sixteen global general circulation models were used to develop probabilistic projections of temperature (T) and precipitation (P) changes over California by the 2060s. The global models were downscaled with two statistical techniques and three nested dynamical regional climate models, although not all global models were downscaled with all techniques. Both monthly and daily timescale changes in T and P are addressed, the latter being important for a range of applications in energy use, water management, and agriculture. The T changes tend to agree more across downscaling techniques than the P changes. Year-to-year natural internal climate variability is roughly of similar magnitude to the projected T changes. In the monthly average, July temperatures shift enough that that the hottest July found in any simulation over the historical period becomes a modestly cool July in the future period. Januarys as cold as any found in the historical period are still found in the 2060s, but the median and maximum monthly average temperatures increase notably. Annual and seasonal P changes are small compared to interannual or intermodel variability. However, the annual change is composed of seasonally varying changes that are themselves much larger, but tend to cancel in the annual mean. Winters show modestly wetter conditions in the North of the state, while spring and autumn show less precipitation. The dynamical downscaling techniques project increasing precipitation in the Southeastern part of the state, which is influenced by the North American monsoon, a feature that is not captured by the statistical downscaling. 相似文献
83.
Summary. (Part 1) Fourier analyses of mean monthly sea-level data from Belém, Fortaleza, Salvador and Imbituba, ports on the Brazilian coast, are made with simultaneous data of air temperature, sea surface atmospheric pressure, atmospheric precipitation and evaporation. Results show that the mean monthly sea-levels of ports below Recife's latitude show peaks in February-March and April-May which are apparently related to the seasonal temperature changes and the combined action of precipitation, winds and oceanographic large-scale changes. The port of Belém showed a stronger semi-annual seasonal component, which seems to be related to the alternate southern and northern hemispheres' influences of the atmospheric precipitation. (Part 2 of the paper presented at the Symposium concerned the longer term changes of sea-level, including an analysis of principal components. These subjects will be treated in a separate paper.) 相似文献
84.
The D'Alembert model for the spin/orbit problem in celestial mechanics is considered. Using a Hamiltonian formalism, it is shown that in a small neighborhood of a p:q spin/orbit resonance with (p,q) different from (1,1) and (2,1) the 'effective' D'Alembert Hamiltonian is a completely integrable system with phase space foliated by maximal invariant curves; instead, in a small neighborhood of a p:q spin/orbit resonance with (p,q) equal to (1,1) or (2,1) the 'effective' D'Alembert Hamiltonian has a phase portrait similar to that of the standard pendulum (elliptic and hyperbolic equilibria, separatrices, invariant curves of different homotopy). A fast averaging with respect to the 'mean anomaly' is also performed (by means of Nekhoroshev techniques) showing that, up to exponentially small terms, the resonant D'Alembert Hamiltonian is described by a two-degrees-of-freedom, properly degenerate Hamiltonian having the lowest order terms corresponding to the 'effective' Hamiltonian mentioned above. 相似文献
85.
We present here, for the O and B type stars in the Catalogue of Stellar Ultraviolet Fluxes, an approach which does not require
a precise knowledge of spectral type and luminosity class for derivingE(B-V) colour excesses. The method is based on the use of an UV-visual two-colour diagram; galactic variations in the interstellar
extinction law are analyzed and fully taken into account. Our results have been compared with those derived by using the differences
between observed and intrinsic colours for stars with known spectral classification. The very good agreement in a large number
of cases (94 per cent) demonstrates that our approach permits the derivation of reliable colour excess values for early type
stars even if only a rough spectral classification is available. 相似文献
86.
We have investigated a simple model for the effects of a central pulsar on the expansion of supernova shells. Some numerical results relevant to the Crab Nebula are also reported. 相似文献
87.
Valentina?MontaldoEmail author Ezio?Faccioli Gaetano?Zonno Aybige?Akinci Luca?Malagnini 《Journal of Seismology》2005,9(3):295-316
In the framework of the 2004 reference seismic hazard map of Italy the amplitude of the strong-motion (expressed in terms
of Peak Horizontal Acceleration with 10% probability of non-exceedence in 50 years, referred to average hard ground conditions)
was computed using different predictive relationships. Equations derived in Italy and in Europe from strong-motion data, as
well as a set of weak and strong-motion based empirical predictive relationships were employed in a logic tree procedure,
in order to capture the epistemic uncertainty affecting ground-motion attenuation. This article describes the adjustments
and conversions required to eliminate the incompatibilities amongst the relations. Particularly significant are distance conversions
and style-of-faulting adjustments, as well as the problems related to the use of regional relations, such as the selection
of a reference depth, the quantification of random variability and the strong-motion prediction. Moreover, a regional attenuation
relationship specific for volcanic areas was also employed, allowing a more realistic evaluation of seismic hazard, as confirmed
by the attenuation of macroseismic intensities. 相似文献
88.
Franco?Braga Marco?Faggella Rosario?Gigliotti Michelangelo?LaterzaEmail author 《Bulletin of Earthquake Engineering》2005,3(3):333-353
The isolation systems are usually made of rubber bearings that are sometimes coupled in hybrid combination with frictional
devices; this is the case of an in-site experimental campaign, performed on a base isolated apartment building in Rapolla
(south of Italy). Several dropout tests at initial displacements up to 17cm allowed to obtain in-site information on the true
dynamic response of the isolation system (building and isolators). The tests carried out allow a comparison between the free
vibration responses of a building, isolated by using a 28 HDRB isolation system only, or an HDRB-Friction Sliders Hybrid one.
The paper highlights the main differences of the response in the superstructure (the structure over the isolation system)
obtained by using only HDRB isolation system, or the Hybrid one (HDRB and Friction Sliders in parallel system). Analysis and
comparisons of experimental data, show the influence of nonlinearities on structural higher modes amplification, especially
observed by using the higher nonlinear Hybrid isolation system. Tests results confirm that, in the case of a regular superstructure,
like the Rapolla building, the isolation system nonlinearities influence the structural response. 相似文献
89.
Antonio?VecchioEmail author Leonardo?Primavera Vincenzo?Carbone Luca?Sorriso-Valvo 《Solar physics》2005,229(2):359-372
We use the Proper Orthogonal Decomposition (POD) to investigate the spatiotemporal features of the solar activity. Daily observation
in the period 1949–1996 of the green coronal emission line at 530.3 nm are used as indicators of the activity behavior. We
show that few POD modes suffice in describing both the space and time main periodicities. In particular, being affected by
a strongly energetic stochastic behavior, daily data are described by five POD modes, while two POD modes are enough to describe
the butterfly diagram in monthly averaged data. Apart from the basic period T0 = 11 years, using daily data we found evidences for intercycle temporal periodicities. 相似文献
90.
Franco Ricci Lucchi 《Geo-Marine Letters》1984,3(2-4):203-210
Submarine fans of different sizes, geometry, and petrology were built in the Marnoso-arenacea Basin, a migrating foredeep
within an active continental margin. In an initial depositional stage, a well-developed basin plain received sediment from
flows that by-passed restricted fan systems, now buried, located near the north end of an elongated basin. Minor fans grew
near the steeper, tectonically deformed side of the basin. In the later stage, turbidite deposition was stopped in the former
basin plain. Sediment sources and feeder channels shifted and fed fan lobes that prograded in a narrower trough and were distored
(choked). The tectonic control on development of megasequence and sand bodies is stressed here in contrast with previous emphasis
on “inner” or “autocyclic” mechanisms.
Margin setting represents fan and/or source area 相似文献