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341.
Warren W. Wood Richard M. Bailey Brian A. Hampton Thomas F. Kraemer Zhong Lu David W. Clark Rhodri H.R. James Khalid Al Ramadan 《Quaternary Research》2012,77(2):215-220
The coastline along the southern Arabian Gulf between Al Jubail, Kingdom of Saudi Arabia, and Dubai, UAE, appears to have risen at least 125 m in the last 18,000 years. Dating and topographic surveying of paleo-dunes (43–53 ka), paleo-marine terraces (17–30 ka), and paleo-marine shorelines (3.3–5.5 ka) document a rapid, > 1 mm/a subsidence, followed by a 6 mm/a uplift that is decreasing with time. The mechanism causing this movement remains elusive but may be related to the translation of the coastal area through the backbasin to forebulge hinge line movement of the Arabian plate or, alternatively, by movement of the underlying Infracambrian-age Hormuz salt in response to sea-level changes associated with continental glaciation. Independent of the mechanism, rapid and episodic uplift may impact the design of engineering projects such as nuclear power plants, airports, and artificial islands as well as the interpretation of sedimentation and archeology of the area. 相似文献
342.
343.
We present a study of water vapour in the Venus troposphere obtained by modelling specific water vapour absorption bands within the 1.18 μm window. We compare the results with the normal technique of obtaining the abundance by matching the peak of the 1.18 μm window. Ground-based infrared imaging spectroscopy of the night side of Venus was obtained with the Anglo-Australian Telescope and IRIS2 instrument with a spectral resolving power of R ~ 2400. The spectra have been fitted with modelled spectra simulated using the radiative transfer model VSTAR. We find a best fit abundance of 31 ppmv (?6 +9 ppmv), which is in agreement with recent results by Bézard et al. (Bézard, B., Fedorova, A., Bertaux, J.-L., Rodin, A., Korablev, O. [2011]. Icarus, 216, 173–183) using VEX/SPICAV (R ~ 1700) and contrary to prior results by Bézard et al. (Bézard, B., de Bergh, C., Crisp, D., Maillard, J.P. [1990]. Nature, 345, 508–511) of 44 ppmv (±9 ppmv) using VEX/VIRTIS-M (R ~ 200) data analyses. Comparison studies are made between water vapour abundances determined from the peak of the 1.18 μm window and abundances determined from different water vapour absorption features within the near infrared window. We find that water vapour abundances determined over the peak of the 1. 18 μm window results in plots with less scatter than those of the individual water vapour features and that analyses conducted over some individual water vapour features are more sensitive to variation in water vapour than those over the peak of the 1. 18 μm window. No evidence for horizontal spatial variations across the night side of the disk are found within the limits of our data with the exception of a possible small decrease in water vapour from the equator to the north pole. We present spectral ratios that show water vapour absorption from within the lowest 4 km of the Venus atmosphere only, and discuss the possible existence of a decreasing water vapour concentration towards the surface. 相似文献
344.
The uppermost Whitcliffian strata of the Welsh Borderlands record the final phase of marine sedimentation in the Silurian basin and shelf environments. They give way transitionally to the succeeding non-marine Lower Old Red Sandstone. As a contribution to the understanding of the change from marine to continental facies, the magnetic fabric method was used to obtain palaeocurrent data for the uppermost Whitcliffian. The results confirm that the uppermost Whitcliffian palaeocurrent pattern is essentially “Silurian” in character and does not foreshadow the deltaic and littoral patterns of sediment distribution observed in the basal Old Red Sandstone. 相似文献
345.
The worldwide increase in shell midden deposits on coastlines during the Holocene has been variously explained as the result of human population growth, economic intensification, changes in the visibility of midden deposits with changes in sea level, or climatic and environmental changes. Since coastlines are relatively unstable in geological and ecological terms, and since many archaeological sequences span periods of major climatic change, a critical issue is the ability to disentangle palaeoenvironmental from cultural and anthropogenic effects. We draw on a case study from the cave sequences of northern Spain to illustrate the problems and possibilities of palaeoeconomic and palaeoenvironmental interpretation, using studies of palaeogeographical context and analysis of abundance, taxonomic representation, ecological tolerances, size, growth structures, and other physical and chemical characteristics of the molluscs themselves. We demonstrate that the dominant, but by no means exclusive, factor in archaeologically visible long‐term changes in shell‐gathering behavior is environmental change rather than cultural change. © 2003 Wiley Periodicals, Inc. 相似文献
346.
A total field magnetic anomaly contour map of the continental margin west of Ireland is described by reference to geological structure previously established by seismic reflection profiling. The western Irish Mainland Shelf, Porcupine Seabight Trough and Porcupine Ridge were previously defined as major north-south elements in the structure of the margin. Each is readily distinguished on the magnetic anomaly contour map. To the north these features terminate against, or merge with, the east-west Slyne Ridge. A pronounced change in the magnetic anomaly pattern at about 53°N suggests that the southern limit of this Ridge coincides with a major geological discontinuity extending from near the coast of Ireland to the continental slope, some 320 km to the west. The magnetic anomaly contour map gives general support to the idea that the Slyne Ridge and Porcupine Ridge represent submerged blocks of marginal continental crust, and that the Porcupine Seabight Trough is founded upon crust significantly different in character. 相似文献
347.
Haydon Bailey 《Geology Today》2023,39(1):18-26
The unique geological history which resulted in the evolution of the Chiltern Hills to the north of London, The United Kingdom, created the underlying foundations for everything that we see there on the surface today. The roots of the Chiltern Hills lie in their Chalk foundations. To understand the details of the way the chalk acts as an aquifer it is important to understand first the origins of the chalk sediment and how the subsequent geological history of the region has impacted on the rocks preserved today. 相似文献