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111.
The strong increase in altimeter measurement errors near land surfaces is a limiting factor for coastal applications. We analyze the performance of the new Ka-band SARAL/AltiKa (SRL) mission in the northwestern Mediterranean Sea. SRL sea surface height (SSH) measurements are compared with those from the Jason-2 Ku-band satellite mission. The results show a significant increase in both quantity and quality of SSH data available near coastlines when using SRL data. Available edited data are 95.1% of SRL compared with 88.6% for Jason-2. Closer than 10 km to the coastline, available SRL data are still about 60% and only about 31% for Jason-2. Comparisons of the altimeter sea level variations are made with available coastal tide gauge data. The differences obtained between altimeter and tide gauge SLA time series are reduced for SRL (3.3 cm in average) compared with Jason-2 (4.2 cm in average), especially closer than 30 km to the land. It results in higher correlations (by 30%) obtained with SRL data. The coastal circulation derived from altimetry using SRL data shows an offshore meandering, which is more stable in time and with larger velocities close to the coast than that derived from Jason-2 observations. 相似文献
112.
SIM‐France is a large connected atmosphere/land surface/river/groundwater modelling system that simulates the water cycle throughout metropolitan France. The work presented in this study investigates the replacement of the river routing scheme in SIM‐France by a river network model called RAPID to enhance the capacity to relate simulated flows to river gauges and to take advantage of the automated parameter estimation procedure of RAPID. RAPID was run with SIM‐France over a 10‐year period and results compared with those of the previous river routing scheme. We found that while the formulation of RAPID enhanced the functionality of SIM‐France, the flow simulations are comparable in accuracy to those previously obtained by SIM‐France. Sub‐basin optimization of RAPID parameters was found to increase model efficiency. A single criterion for quantifying the quality of river flow simulations using several river gauges globally in a river network is developed that normalizes the square error of modelled flow to allow equal treatment of all gauging stations regardless of the magnitude of flow. The use of this criterion as the cost function for parameter estimation in RAPID allows better results than by increasing the degree of spatial variability in optimization of model parameters. Likewise, increased spatial variability of RAPID parameters through accounting for topography is shown to enhance model performance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
113.
114.
Photoelectric observations of seven asteroids were made from Gila Observatory between October 14, 1983, and June 21, 1984. The following synodic rotational periods and amplitudes are reported: 9 Metis, P = 5.04 hr, ΔM = 0.05; 18 Melpomene, P = 11.570 hr, ΔM = 0.22; 60 Echo, P = 25.208 hr, ΔM = 0.22; 116 Sirona, P = 12.028 hr, ΔM = 0.42; 230 Athamantis, P = 23.99 hr, ΔM > 0.20; 694 Ekard, P = 5.925 hr, ΔM = 0.50; 1984 KD, P = 1.97 hr, ΔM = 0.26. The rotational periods reported for asteroid 60 Echo, 116 Sirona, 694 Ekard, and 1984 KD represent completely new results. The synodic rotational period reported for asteroid 1984 KD is tentative and is based largely upon the observations of a single night. The reported synodic periods of the remaining six asteroids are based upon a minimum of 3 nights of photometric observations. 相似文献
115.
Florence Le Hébel Olivier Vidal Jean-Robert Kienast Denis Gapais 《Comptes Rendus Geoscience》2002,334(3):205-211
The so-called ‘Porphyro??des’ Unit of South Brittany is located below units marked by an early HP–LT event (blueschists from the Île de Groix) and above units marked by Upper Carboniferous HT metamorphism. P–T estimates in the Porphyro??des (at Belle-Île-en-Mer), using the phengite–chlorite thermobarometer, indicate pressures around 8 kbar and temperatures of 350–400 °C. These new estimates suggest that the early tectonic history of the ‘Porphyro??des’ should be linked to that of the overlying Blueschists, and imply a much larger areal extension of the HP–LT domain in this part of the Hercynian Belt. To cite this article: F. Le Hébel et al., C. R. Geoscience 334 (2002) 205–211. 相似文献
116.
Om Prakash Tripathi Sophie Godin-Beekmann Franck Lefèvre Marion Marchand Andrea Pazmiño Alain Hauchecorne Florence Goutail Hans Schlager C. Michael Volk B. Johnson G. König-Langlo Stefano Balestri Fred Stroh T. P. Bui H. J. Jost T. Deshler Peter von der Gathen 《Journal of Atmospheric Chemistry》2006,55(3):205-226
Simulations of polar ozone losses were performed using the three-dimensional high-resolution (1∘ × 1∘) chemical transport model MIMOSA-CHIM. Three Arctic winters 1999–2000, 2001–2002, 2002–2003 and three Antarctic winters 2001, 2002, and 2003 were considered for the study. The cumulative ozone loss in the Arctic winter 2002–2003 reached around 35% at 475 K inside the vortex, as compared to more than 60% in 1999–2000. During 1999–2000, denitrification induces a maximum of about 23% extra ozone loss at 475 K as compared to 17% in 2002–2003. Unlike these two colder Arctic winters, the 2001–2002 Arctic was warmer and did not experience much ozone loss. Sensitivity tests showed that the chosen resolution of 1∘ × 1∘ provides a better evaluation of ozone loss at the edge of the polar vortex in high solar zenith angle conditions. The simulation results for ozone, ClO, HNO3, N2O, and NO
y
for winters 1999–2000 and 2002–2003 were compared with measurements on board ER-2 and Geophysica aircraft respectively. Sensitivity tests showed that increasing heating rates calculated by the model by 50% and doubling the PSC (Polar Stratospheric Clouds) particle density (from 5 × 10−3 to 10−2 cm−3) refines the agreement with in situ ozone, N2O and NO
y
levels. In this configuration, simulated ClO levels are increased and are in better agreement with observations in January but are overestimated by about 20% in March. The use of the Burkholder et al. (1990) Cl2O2 absorption cross-sections slightly increases further ClO levels especially in high solar zenith angle conditions. Comparisons of the modelled ozone values with ozonesonde measurement in the Antarctic winter 2003 and with Polar Ozone and Aerosol Measurement III (POAM III) measurements in the Antarctic winters 2001 and 2002, shows that the simulations underestimate the ozone loss rate at the end of the ozone destruction period. A slightly better agreement is obtained with the use of Burkholder et al. (1990) Cl2O2 absorption cross-sections. 相似文献
117.
Duane G Froese Derald G SmithJohn A Westgate Thomas A AgerShari J Preece Amanjit SandhuRandolph J Enkin Florence Weber 《Quaternary Research》2003,60(1):50-62
Recurring glacial outburst floods from the Yukon-Tanana Upland are inferred from sediments exposed along the Yukon River near the mouth of Charley River in east-central Alaska. Deposits range from imbricate gravel and granules indicating flow locally extending up the Yukon valley, to more distal sediments consisting of at least 10 couplets of planar sands, granules, and climbing ripples with up-valley paleocurrent indicators overlain by massive silt. An interglacial organic silt, occurring within the sequence, indicates at least two flood events are associated with an earlier glaciation, and at least three flood events are associated with a later glaciation which postdates the organic silt. A minimum age for the floods is provided by a glass fission track age of 560,000 ± 80,000 yr on the GI tephra, which occurs 8 m above the flood beds. A maximum age of 780,000 yr for the floods is based on normal magnetic polarity of the sediments. These age constraints allow us to correlate the flood events to the early-middle Pleistocene. And further, the outburst floods indicate extensive glaciation of the Yukon-Tanana Upland during the early-middle Pleistocene, likely representing the most extensive Pleistocene glaciation of the area. 相似文献
118.
In southwest Western Australia, strong and persistent sea breezes are common between September and February. We hypothesized
that on the inner continental shelf, in the absence of tidal forcing, the depth, magnitude, and lag times of the current speed
and direction responses to sea breezes would vary though the water column as a function of the sea breeze intensity. To test
this hypothesis, field data were used from four sites were that were in water depths of up to 13 m. Sites were located on
the inner continental shelf and were on the open coast and in a semi-enclosed coastal embayment. The dominant spectral peak
in currents at all sites indicated that the majority of the spectral energy contained in the currents was due to forcing by
sea breezes. Currents were aligned with the local orientation of the shoreline. On a daily basis, the sea breezes resulted
in increased current speeds and also changed the current directions through the water column. The correlation between wind–current
speeds and directions with depth, and the lag time between the onset of the sea breeze and the response of currents, were
dependent on the intensity of the sea breezes. A higher correlation between wind and current speeds occurred during strong
sea breezes and was associated with shorter lag times for the response of the bottom currents. The lag times were validated
with estimates of the vertical eddy viscosity. Solar heating caused the water column to stratify in summer and the sea breezes
overcame this stratification. Sea breezes caused the mixed layer to deepen and the intensity of the stratification was correlated
to the strength of the sea breezes. Weak sea breezes of <5 m s−1 were associated with the strongest thermal stratification of the water column, up to 1°C between the surface and bottom layers
(6 and 10 m below the surface). In comparison, strong sea breezes of >14 m s−1 caused only slight thermal stratification up to 0.5°C. Apart from these effects on the vertical structure of water column,
the sea breezes also influenced transport and mixing in the horizontal dimension. The sea breezes in southwest Western Australia
rotated in an anticlockwise direction each day and this rotation was translated into the currents. This current rotation was
more prominent in surface currents and in the coastal embayment compared to the open coast. 相似文献
119.
The Bali Action Plan and Cancun agreements on Reducing Emissions from Deforestation and forest Degradation, plus forest conservation, sustainable management of forests and enhancement of forest carbon stocks (REDD+) have encouraged demonstration activities as part of Readiness and a step towards national approaches. This has enabled important growth in pilot and demonstration projects. Yet an understanding about how these projects are connected and contribute to national-level technical, policy, and institutional preparedness (Readiness) for REDD+ is lacking. This article examines the linkages between national processes and the private-sector-driven Kasigau Corridor REDD+ project in Kenya. The study reveals interesting cross-scale interactions that have increased over time and have high potential for harnessing national-level processes through lessons from the project level. Key innovations from the Kasigau Corridor Project include the implementation of REDD+ in dry forests, operationalization of conservation easements in the context of REDD+, and demonstration of potential ways of obtaining upfront finance for REDD+. The study also provides a number of key recommendations for Kenya and REDD+ in general, including official endorsement of stand-alone REDD+ projects under national Readiness schemes and exploring jurisdictional and nested REDD+ approaches. Additionally, more accommodating national-level frameworks for attracting private-sector engagement and investments, and for integrating, scaling-out, or scaling-up lessons from such projects, would be needed to enhance national REDD+ Readiness. 相似文献
120.