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71.
72.
A survey procedure using digitally acquired, scale-corrected sidescan sonar has been applied to document active submarine
landslides in the Mississippi Delta region. Periodic resurveys have been completed for a 70-km2 area in water depths of 10 to 50 m. Sufficient resurvey precision allowed short-term changes in seafloor mapping to be observed.
Mudslides showed enlargement by retrogression and downslope surging within a single 5-month period. 相似文献
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Cyclic sequences occur worldwide in nearly every stratigraphic sequence; they are particularly well developed in marine deposits
associated with large river systems. Superimposed on those cycles attributed to shifting sites of deposition are those related
to high-frequency sea level changes. The large data base for this study (including 471 deep foundation borings, thousands
of line kilometers of high-resolution seismic, and sedimentological and dating analyses) represents the most complete information
on high-resolution chronostratigraphy and lithostratigraphy that is available on any modern continental shelf/upper slope.
These data are used to document sedimentological characteristics and spatial depositional patterns during three complete sea
level cycles over the entire continental shelf/upper slope of offshore Louisiana.
Sedimentation during periods of high sea level is characterized by: 1) thin, slowly accumulated depositional sequences, referred
to as condensed sections, 2) calcareous-rich deposits, including hemipelagic sediments and shell hashes, and 3) wide lateral
continuity. Sedimentation during periods of low sea level is characterized by; 1) variable-thickness, rapidly accumulated
sequences referred to as expanded sections, 2) coarse-grained elastic deposits, including abundant sands and gravels, and
3) well-defined depositional trends.
Even though the data set covers only a short period of geologic time (240 000 yrs), these high frequency events are responsible
for the deposition of excellent reservoir-quality facies in well-defined and predictable trends. 相似文献
75.
A submarine sediment instability event (landslide) occurred at Kitimat, British Columbia, in 1975. Recent high-resolution
surveys provide details of the resulting seafloor morphology. The effects of the slide include modification of the fjord head
delta-front slopes, transport of delta sediments into deep water and mixing with deep water, fjord bottom clays. Distinctive
features include the results of shallow rotational sliding, tearing and shearing, compressional folding and long distance
block gliding at the downslope slide terminus. 相似文献
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Andre Frossard Pereira de Lucena Roberto Schaeffer Alexandre Salem Szklo 《Global Environmental Change》2010,20(2):342-350
Global climate change induced by the emission of greenhouse gases may pose challenges to energy security. The vulnerability of energy sources, in particular of renewable sources, to climate change raises the need to identify adaptation measures. This paper applies an integrated resource planning approach to calculate least-cost adaptation measures to a set of projected climate impacts on the Brazilian power sector. The methodology used has the advantage of finding optimal solutions that take into consideration the whole energy chain and the interactions between energy supply and demand. Results point in the direction of an increased installed capacity based, mostly, on natural gas, but also sugarcane bagasse, wind power and coal/nuclear plants, to compensate for a lower reliability of hydroelectric production, amongst other impacts. The indirect effect of these results is the displacement of natural gas from other consuming sectors, such as industry, in favor of its use for power generation. Results obtained are, however, based on the techno-economic premises used in the simulation, which may vary in the long term. 相似文献
79.
Kieran M. Ryan D. Michael Williams Drew S. Coleman Staci Loewy 《Geological Journal》2010,45(4):467-480
The western Ireland Ordovician stratigraphy has been previously used to constrain the timing of docking of an island arc and its fore‐arc basin with the margin of Laurentia for the British and Irish Caledonides. New field relationships and age data indicate that one of the key formations, the Rosroe Formation (459.2 ± 0.8 and 465.1 ± 2.1 Ma), and its supposed lateral equivalent, the Maumtrasna Formation are younger than previously interpreted. New age data for a tuff band in the Maumtrasna Formation (468.9 ± 1.3 Ma) also support previous studies showing it can be correlated to the adjacent Mweelrea Formation. The new field evidence, age data and geochemistry contradict some previous studies and show that the Maumtrasna, Rosroe and Derrylea formations can no longer be considered lateral equivalents. Based on the new stratigraphy a revised tectonic model is required with sedimentation in this part of the Caledonides taking place in a fore‐arc basin outboard of a continental arc and the oceanic arc was an along‐strike equivalent of this arc situated in an embayment of the Laurentian margin. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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