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221.
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Myskova T. A. Mil'kevich R. I. L'vov A. B. Miller Yu. V. 《Lithology and Mineral Resources》2000,35(6):583-593
The stratotype Chupa Sequence, which makes up the synonymous tectonic nappe and is a member of oldest (Late Archean) rocks in the Belomorian Mobile Belt, is scrutinized. The nappe is mainly composed of the migmatized, coarse-grained garnet–biotite gneiss with kyanite. Relic formations are represented by lenses of the fine-grained (possibly primary) garnet–biotite gneiss. Fine-grained gneisses generally represent primary sedimentary formations, while metadacites are rare. The kyanite-bearing gneiss is presumably a restitic rock produced by migmatization. Chupa metasediments are represented by immature (low-differentiated) metagraywackes and are akin to metaterrigenous rocks from Late Archean greenstone belts of Karelia (Kostomuksha) and Canada (Quetico). The provenance of metasediments comprises the following three components: tonalite (dacite) 70%, mafic rocks 20%, and ultramafic rocks 10%. The Chupa metagraywacke presumably deposited in a fore-arc basin. 相似文献
223.
We propose a method to compensate for the phase lag and the amplitudeattenuation in the cup anemometer signal. These two effects, caused by theinstrument's inertia, are the major flaws of the cup anemometer in additionto over-speeding. Since the instrument's response is invariant in wavenumber (not frequency) representation, we transform the signals to becompensated from the time domain to the spatial domain by using Taylor'shypothesis. In the spatial domain we apply a linear time-invariant filterto eliminate the phase lag and the amplitude attenuation. The proposedprocedure improves instrument performance down to spatial scales equal toor smaller than the distance constant of the anemometer. The method for cupanemometer compensation is presented in detail and later adapted for vanes. 相似文献
224.
C. Covey A. Abe-Ouchi G. J. Boer B. A. Boville U. Cubasch L. Fairhead G. M. Flato H. Gordon E. Guilyardi X. Jiang T. C. Johns H. Le Treut G. Madec G. A. Meehl R. Miller A. Noda S. B. Power E. Roeckner G. Russell E. K. Schneider R. J. Stouffer L. Terray J.-S. von Storch 《Climate Dynamics》2000,16(10-11):775-787
We examine the seasonal cycle of near-surface air temperature simulated by 17 coupled ocean-atmosphere general circulation models participating in the Coupled Model Intercomparison Project (CMIP). Nine of the models use ad hoc “flux adjustment” at the ocean surface to bring model simulations close to observations of the present-day climate. We group flux-adjusted and non-flux-adjusted models separately and examine the behavior of each class. When averaged over all of the flux-adjusted model simulations, near-surface air temperature falls within 2?K of observed values over the oceans. The corresponding average over non-flux-adjusted models shows errors up to ~6?K in extensive ocean areas. Flux adjustments are not directly applied over land, and near-surface land temperature errors are substantial in the average over flux-adjusted models, which systematically underestimates (by ~5?K) temperature in areas of elevated terrain. The corresponding average over non-flux-adjusted models forms a similar error pattern (with somewhat increased amplitude) over land. We use the temperature difference between July and January to measure seasonal cycle amplitude. Zonal means of this quantity from the individual flux-adjusted models form a fairly tight cluster (all within ~30% of the mean) centered on the observed values. The non-flux-adjusted models perform nearly as well at most latitudes. In Southern Ocean mid-latitudes, however, the non-flux-adjusted models overestimate the magnitude of January-minus-July temperature differences by ~5?K due to an overestimate of summer (January) near-surface temperature. This error is common to five of the eight non-flux-adjusted models. Also, over Northern Hemisphere mid-latitude land areas, zonal mean differences between July and January temperatures simulated by the non-flux-adjusted models show a greater spread (positive and negative) about observed values than results from the flux-adjusted models. Elsewhere, differences between the two classes of models are less obvious. At no latitude is the zonal mean difference between averages over the two classes of models greater than the standard deviation over models. The ability of coupled GCMs to simulate a reasonable seasonal cycle is a necessary condition for confidence in their prediction of long-term climatic changes (such as global warming), but it is not a sufficient condition unless the seasonal cycle and long-term changes involve similar climatic processes. To test this possible connection, we compare seasonal cycle amplitude with equilibrium warming under doubled atmospheric carbon dioxide for the models in our data base. A small but positive correlation exists between these two quantities. This result is predicted by a simple conceptual model of the climate system, and it is consistent with other modeling experience, which indicates that the seasonal cycle depends only weakly on climate sensitivity. 相似文献
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Chris Simpson Steve Rawlings 《Monthly notices of the Royal Astronomical Society》2000,317(4):1023-1028
We present JHKL ' photometry of a complete sample of steep-spectrum radio-loud quasars from the revised 3CR catalogue in the redshift range 0.65 z <1.20. After correcting for contributions from emission lines and the host galaxies, we investigate their spectral energy distributions (SEDs) around 1 μm. About 75 per cent of the quasars are tightly grouped in the plane of optical spectral index, α opt , versus near-infrared spectral index, α IR , with the median value of α opt close to the canonical value, and the median α IR slightly flatter. We conclude that the fraction of moderately obscured, red quasars decreases with increasing radio power, in accordance with the 'receding torus' model which can also explain the relatively flat median near-infrared spectra of the 3CR quasars. Two of the red quasars have inverted infrared spectral indices, and we suggest that their unusual SEDs might result from a combination of dust-scattered and transmitted quasar light. 相似文献
229.
Drivers of ecosystem and climate change in tropical West Africa over the past ∼540 000 years
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230.
William R. Miller Walter H. Ficklin Robert E. Learned 《Journal of Geochemical Exploration》1982,16(3):217-233
A hydrogeochemical survey utilizing waters from streams and springs was conducted in the area of two known porphyry copper deposits in the tropical-marine climate of westcentral Puerto Rico. The most important pathfinder for regional hydrogeochemical surveys is sulfate which reflects the associated pyrite mineralization. Because of increased mobility due to intense chemical weathering and the low pH environment, dissolved copper can also be used as a pathfinder for regional surveys and has the advantage of distinguishing barren pyrite from pyrite associated with copper mineralization. For follow-up surveys, the most important pathfinders are copper, sulfate, pH, zinc, and fluoride. High concentrations of dissolved copper and moderate concentrations of sulfate is a diagnostic indication of nearby sources of copper minerals.An understanding of the geochemical processes taking place in the streambeds and the weathering environment, such as the precipitation of secondary copper minerals, contributes to the interpretation of the geochemical data and the selection of the most favorable areas for further exploration. 相似文献