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41.
42.
Coping with floods in the city of Dresden,Germany 总被引:5,自引:2,他引:3
During August 2002 and again in March 2005 as well as in April 2006 the city of Dresden was hit by floods. The flood in 2002
was an extreme event, only comparable to flooding in 1862 and 1890 in Dresden. The flood discharge in 2006 was the second
highest discharge since 1940 at the Dresden gauge although its return period was only about 15 years. This special situation
enables a comparison of the preparedness of authorities and households in the flood endangered city of Dresden in 2002 after
a long period of relatively low flood discharges and in 2005/2006 just a few years after a severe flood event. Before August
2002, the flood risk awareness and flood preparedness of authorities and households in Dresden was low. The inundation channels
and the Elbe riverbed had not been maintained well. Just 13% of the households had undertaken building precautionary measures.
The severe flood situation as well as the low flood preparedness led to tremendous damage, e.g., losses to residential buildings
amounted to 304 million €. After 2002, the municipal authorities in Dresden developed a new flood management concept and many
households were motivated to undertake precautionary measures. Building precautionary measures had been actually undertaken
by 67% of the households before the floods in 2005 and 2006. Flood damage was significantly lower, due to the less severe
flood situations and the much better preparedness. It is an important challenge for the future to keep preparedness at a high
level also without recurrent flood experiences. 相似文献
43.
One of the most documented effects of human activity on our environment is the reduction of stratospheric ozone resulting
in an increase of biologically harmful ultraviolet (UV) radiation. In a less predictable manner, UV radiation incident at
the surface of the earth is expected to be further modified in the future as a result of altered cloud condition, atmospheric
aerosol concentration, and snow cover. Although UV radiation comprises only a small fraction of the total solar radiation
that is incident at the earth’s surface, it has the greatest energy per unit wavelength and, thus, the greatest potential
to damage the biosphere. Recent investigations have highlighted numerous ways that UV radiation could potentially affect a
variety of ecological processes, including nutrient cycling and the terrestrial carbon cycle. The objectives of the following
literature review are to summarize and synthesize the available information relevant to the effects of UV radiation and other
climate change factors on the terrestrial carbon balance in an effort to highlight current gaps in knowledge and future research
directions for UV radiation research. 相似文献
44.
Seasonal controls on sediment transport and deposition in Lake Ohau,South Island,New Zealand: Implications for a high‐resolution Holocene palaeoclimate reconstruction
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Heidi A. Roop Gavin B. Dunbar Richard Levy Marcus J. Vandergoes Alexander L. Forrest Sharon L. Walker Jennifer Purdie Phaedra Upton James Whinney 《Sedimentology》2015,62(3):826-844
Laminated sediments in Lake Ohau, Mackenzie Basin, New Zealand, offer a potential high‐resolution climate record for the past 17 kyr. Such records are particularly important due to the relative paucity of detailed palaeoclimate data from the Southern Hemisphere mid‐latitudes. This paper presents outcomes of a study of the sedimentation processes of this temperate lake setting. Hydrometeorological, limnological and sedimentological data were collected over a 14 month period between 2011 and 2013. These data indicate that seasonality in the hydrometeorological system in combination with internal lake dynamics drives a distinct seasonal pattern of sediment dispersal and deposition on a basin‐wide scale. Sedimentary layers that accumulate proximal to the lake inflow at the northern end of the lake form in response to discrete inflow events throughout the year and display an event stratigraphy. In contrast, seasonal change in the lake system controls accumulation of light (winter) and dark (summer) laminations at the distal end of the lake, resulting in the preservation of varves. This study documents the key processes influencing sediment deposition throughout Lake Ohau and provides fundamental data for generating a high‐resolution palaeoclimate record from this temperate lake. 相似文献
45.
Employing the properties of the affine mappings, a very novel fractal model scheme based on the iterative function system is proposed. We obtain the vertical scaling factors by a set of the middle points in each affine transform, solving the difficulty in determining the vertical scaling factors, one of the most difficult challenges faced by the fractal interpolation. The proposed method is carried out by interpolating the known attractor and the real discrete sequences from seismic data. The results show that a great accuracy in reconstruction of the known attractor and seismic profile is found, leading to a significant improvement over other fractal interpolation schemes. 相似文献
46.
Heidi Houston Helen Anderson Susan L. Beck Jiajun Zhang Susan Schwartz 《Pure and Applied Geophysics》1993,140(2):331-364
To evaluate the tectonic significance of the October 20, 1986 Kermadec earthquake (M
w
=7.7), we performed a comprehensive analysis of source parameters using surface waves, body waves, and relocated aftershocks. Amplitude and phase spectra from up to 93 Rayleigh waves were inverted for centroid time, depth, and moment tensor in a two-step algorithm. In some of the inversions, the time function was parameterized to include information from the body-wave time function. The resulting source parameters were stable with respect to variations in the velocity and attenuation models assumed, the parameterization of the time function, and the set of Rayleigh waves included. The surface wave focal mechanism derived (=275°, =61°, =156°) is an oblique-compressional mechanism that is not easy to interpret in terms of subduction tectonics. A seismic moment of 4.5×1020 N-m, a centroid depth of 45±5 km, and a centroid time of 13±3 s were obtained. Directivity was not resolvable from the surface waves. The short source duration is in significant contrast to many large earthquakes.We performed a simultaneous inversion ofP andSH body waves for focal mechanism and time function. The focal mechanism agreed roughly with the surface wave mechanism. Multiple focal mechanisms remain a possibility, but could not be resolved. The body waves indicate a short duration of slip (15 to 20 s), with secondary moment release 60s later. Seismically radiated energy was computed from the body-wave source spectrum. The stress drop computed from the seismic energy is about 30 bars. Sixty aftershocks that occurred within three months of the mainshock were relocated using the method of Joint Hypocentral Determination (JHD). Most of the aftershocks have underthrusting focal mechanisms and appear to represent triggered slip on the main thrust interface. The depth, relatively high stress drop, short duration of slip, and paucity of true aftershocks are consistent with intraplate faulting within the downgoing plate. Although it is not clear on which nodal plane slip occurred, several factors favor the roughly E-W trending plane. The event occurred near a major segmentation in the downgoing plate at depth, near a bend in the trench, and near a right-lateral offset of the volcanic are by 80 km along an E-W direction. Also, all events in the region from 1977 to 1991 with CMT focal mechanisms similar to that of the Mainshock occurred near the mainshock epicenter, rather than forming an elongate zone parallel to the trench as did the aftershock activity. We interpret this event as part of the process of segmentation or tearing of the subducting slab. This segmentation appears to be related to the subduction of the Louisville Ridge, which may act as an obstacle to subduction through its buoyancy. 相似文献
47.
DeWeese Nichole E. Favot Elizabeth J. Branstrator Donn K. Reavie Euan D. Smol John P. Engstrom Daniel R. Rantala Heidi M. Schottler Shawn P. Paterson Andrew M. 《Journal of Paleolimnology》2021,66(4):389-405
Journal of Paleolimnology - The spiny water flea (Bythotrephes cederströmii), a freshwater crustacean considered to be the world’s best-studied invasive zooplankter, was first recorded... 相似文献
48.
49.
Walter Finsinger Kristian Schoning Sheila Hicks Andreas Lücke Tomasz Goslar Friederike Wagner‐cremer Heidi Hyyppä 《第四纪科学杂志》2013,28(2):152-164
We present a record of peatland development in relation to climate changes and human activities from the Palomaa mire, a remote site in northern Finland. We used fine‐resolution and continuous sampling to analyse several proxies including pollen (for vegetation on and around the mire), testate amoebae (TA; for mire‐wetness changes), oxygen and carbon isotopes from Sphagnum cellulose (δ18O and δ13C; for humidity and temperature changes), peat‐accumulation rates and peat‐colour changes. In spite of an excellent accumulation model (30 14C dates and estimated standard deviation of sample ages <1 year in the most recent part), the potential to determine cause–effect (or lead–lag) relationships between environmental changes and biotic responses is limited by proxy‐specific incorporation processes below the actively growing Sphagnum surface. Nevertheless, what emerges is that mire development was closely related to water‐table changes rather than to summer temperature and that water‐table decreases were associated with increasing peat‐accumulation rates and more abundant mire vegetation. A rapid fen‐to‐bog transition occurred within a few years around AD 1960 when the water table decreased beyond the historical minimum, supporting the notion that mires can rapidly shift into bogs in response to allogenic factors. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
50.
Imke de Pater David E. Dunn Daphne M. Stam Mark R. Showalter Heidi B. Hammel Michiel Min Markus Hartung Seran G. Gibbard Marcos A. van Dam Keith Matthews 《Icarus》2013
We present observations of the uranian ring system at a wavelength of 2.2 μm, taken between 2003 and 2008 with NIRC2 on the W.M. Keck telescope in Hawaii, and on 15–17 August 2007 with NaCo on the Very Large Telescope (VLT) in Chile. Of particular interest are the data taken around the time of the uranian ring plane crossing with Earth on 16 August 2007, and with the Sun (equinox) on 7 December 2007. We model the data at the different viewing aspects with a Monte Carlo model to determine: (1) the normal optical depth τ0, the location, and the radial extent of the main rings, and (2) the parameter Aτ0 (A is the particle geometric albedo), the location, and the radial plus vertical extent of the dusty rings. Our main conclusions are: (i) The brightness of the ? ring is significantly enhanced at small phase and ring inclination angles; we suggest this extreme opposition effect to probably be dominated by a reduction in interparticle shadowing. (ii) A broad sheet of dust particles extends inwards from the λ ring almost to the planet itself. This dust sheet has a vertical extent of ∼140 km, and Aτ0 = 2.2 × 10−6. (iii) The dusty rings between ring 4 and the α ring and between the α and β rings are vertically extended with a thickness of ∼300 km. (iv) The ζ ring extends from ∼41,350 km almost all the way inwards to the planet. The main ζ ring, centered at ∼39,500 km from the planet, is characterized by Aτ0 = 3.7 × 10−6; this parameter decreases closer to the planet. The ζ ring has a full vertical extent of order 800–900 km, with a pronounced density enhancement in the mid-plane. (v) The ηc ring is optically thin and less than several tens of km in the vertical direction. This ring may be composed of macroscopic material, surrounded by clumps of dust. 相似文献