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排序方式: 共有163条查询结果,搜索用时 15 毫秒
21.
Sin Chan Chou José A. Marengo André A. Lyra Gustavo Sueiro José F. Pesquero Lincoln M. Alves Gillian Kay Richard Betts Diego J. Chagas Jorge L. Gomes Josiane F. Bustamante Priscila Tavares 《Climate Dynamics》2012,38(3-4):635-653
The objective of this work is to evaluate climate simulations over South America using the regional Eta Model driven by four members of an ensemble of the UK Met Office Hadley Centre HadCM3 global model. The Eta Model has been modified with the purpose of performing long-term decadal integrations and has shown to reproduce “present climate”—the period 1961–1990—reasonably well when forced by HadCM3. The global model lateral conditions with a resolution of 2.5° latitude?×?3.75° longitude were provided at a frequency of 6?h. Each member of the global model ensemble has a different climate sensitivity, and the four members were selected to span the range of uncertainty encompassed by the ensemble. The Eta Model nested in the HadCM3 global model was configured with 40-km horizontal resolution and 38 layers in the vertical. No large-scale internal nudging was applied. Results are shown for austral summer and winter at present climate defined as 1961–90. The upper and low-level circulation patterns produced by the Eta-CPTEC/HadCM3 experiment set-up show good agreement with reanalysis data and the mean precipitation and temperature with CRU observation data. The spread in the downscaled mean precipitation and temperature is small when compared against model errors. On the other hand, the benefits in using an ensemble is clear in the improved representation of the seasonal cycle by the ensemble mean over any one realization. El Ni?o and La Ni?a years were identified in the HadCM3 member runs based on the NOAA Climate Prediction Center criterion of sea surface temperature anomalies in the Ni?o 3.4 area. The frequency of the El Ni?o and La Ni?a events in the studied period is underestimated by HadCM3. The precipitation and temperature anomalies typical of these events are reproduced by most of the Eta-CPTEC/HadCM3 ensemble, although small displacements of the positions of the anomalies occur. This experiment configuration is the first step on the implementation of Eta-CPTEC/HadCM3 upcoming experiments on climate change studies that are discussed in a companion paper. 相似文献
22.
Assessment of regional seasonal predictability using the PRECIS regional climate modeling system over South America 总被引:1,自引:0,他引:1
The purpose of this study was to evaluate the accuracy and skill of the UK Met Office Hadley Center Regional Climate Model (HadRM3P) in describing the seasonal variability of the main climatological features over South America and adjacent oceans, in long-term simulations (30 years, 1961–1990). The analysis was performed using seasonal averages from observed and simulated precipitation, temperature, and lower- and upper-level circulation. Precipitation and temperature patterns as well as the main general circulation features, including details captured by the model at finer scales than those resolved by the global model, were simulated by the model. However, in the regional model, there are still systematic errors which might be related to the physics of the model (convective schemes, topography, and land-surface processes) and the lateral boundary conditions and possible biases inherited from the global model. 相似文献
23.
Future change of climate in South America in the late twenty-first century: intercomparison of scenarios from three regional climate models 总被引:2,自引:1,他引:1
Jose A. Marengo Tercio Ambrizzi Rosmeri P. da Rocha Lincoln M. Alves Santiago V. Cuadra Maria C. Valverde Roger R. Torres Daniel C. Santos Simone E. T. Ferraz 《Climate Dynamics》2010,35(6):1073-1097
Regional climate change projections for the last half of the twenty-first century have been produced for South America, as
part of the CREAS (Cenarios REgionalizados de Clima Futuro da America do Sul) regional project. Three regional climate models
RCMs (Eta CCS, RegCM3 and HadRM3P) were nested within the HadAM3P global model. The simulations cover a 30-year period representing
present climate (1961–1990) and projections for the IPCC A2 high emission scenario for 2071–2100. The focus was on the changes
in the mean circulation and surface variables, in particular, surface air temperature and precipitation. There is a consistent
pattern of changes in circulation, rainfall and temperatures as depicted by the three models. The HadRM3P shows intensification
and a more southward position of the subtropical Pacific high, while a pattern of intensification/weakening during summer/winter
is projected by the Eta CCS/RegCM3. There is a tendency for a weakening of the subtropical westerly jet from the Eta CCS and
HadRM3P, consistent with other studies. There are indications that regions such of Northeast Brazil and central-eastern and
southern Amazonia may experience rainfall deficiency in the future, while the Northwest coast of Peru-Ecuador and northern
Argentina may experience rainfall excesses in a warmer future, and these changes may vary with the seasons. The three models
show warming in the A2 scenario stronger in the tropical region, especially in the 5°N–15°S band, both in summer and especially
in winter, reaching up to 6–8°C warmer than in the present. In southern South America, the warming in summer varies between
2 and 4°C and in winter between 3 and 5°C in the same region from the 3 models. These changes are consistent with changes
in low level circulation from the models, and they are comparable with changes in rainfall and temperature extremes reported
elsewhere. In summary, some aspects of projected future climate change are quite robust across this set of model runs for
some regions, as the Northwest coast of Peru-Ecuador, northern Argentina, Eastern Amazonia and Northeast Brazil, whereas for
other regions they are less robust as in Pantanal region of West Central and southeastern Brazil. 相似文献
24.
Jiří Žák Scott R. Paterson Vojtěch Janoušek Petr Kabele 《Contributions to Mineralogy and Petrology》2009,158(4):447-470
The Mammoth Peak sheeted intrusive complex formed in the interior of a ~7–10 km deep magma chamber, specifically in the Half
Dome granodiorite of the Tuolumne batholith, central Sierra Nevada, CA (USA). The sheets consist of fractionated melts with
accumulated hornblende, biotite, magnetite, titanite, apatite, and zircon. The accumulation, especially of titanite, had a
profound effect on minor and trace elements (Nb, Ta, Ti, REE, U, Th, P, Zr, Hf, etc.), increasing their contents up to five
to six times. Our thermal–mechanical modeling using the finite element method shows that cooling-generated tensile stresses
resulted in the inward propagation of two perpendicular sets of dilational cracks in the host granodiorite. We interpret the
sheeted complex to have formed by a crack-seal mechanism in a high strength, crystal-rich mush, whereby outward younging pulses
of fractionated magma were injected into these syn-magmatic cracks at the margin of an active magma chamber. Thermal–mechanical
instabilities developed after the assembly of the sheeted complex, which was then overprinted by late ~NW–SE magmatic foliation.
This case example provides a cautionary note regarding the interpretation that sheeted zones in large granitoid plutons imply
a diking mechanism of growth because the sheeted/dike complexes in plutons (1) may display inverse growth directions from
the growth of the overall intrusive sequence; (2) need not record initial chamber construction and instead may reflect late
pulsing of magma within an already constructed magma chamber; (3) have an overprinting magmatic fabric indicating the continued
presence of melt after construction of sheeted complexes and thus a prolonged thermal history as compared to dikes; and (4)
because the scale of the observed sheeted complexes may be small (<1%) in comparison to large homogenous parts of plutons,
in which there is no evidence for sheeting or diking. Thus, where extensive dike complexes in plutons are absent, such as
in much of the Tuolumne batholith, the application of an incremental diking model to explain chamber construction is at best
speculative. 相似文献
25.
26.
Regression models are developed and presented to predict dry mass (mg) from two linear dimensions (mm) for 17 benthic macroinvertebrate taxa common to littoral zones of New Zealand lakes. We also provide regression models to predict body length from head capsule width for the major insect taxa. Dry mass was best explained as a power function of all linear dimensions: M = aL b .Parameters are presented in the log10‐transformed linear form of this power function. Body length was a simple linear function of head capsule width for all insect taxa, hence parameters for these models are presented as untransformed values. We also provide family level models for the Chironomidae, and compare our chironomid body length‐mass model with other published Chrionomidae length‐mass models. There was a very high degree of variability in parameter values among published length‐mass models for the family Chironomidae (mean coefficient of variation for mass at length = 148%). We discuss the potential causes and implications of this variability. 相似文献
27.
28.
Human systems will have to adapt to climate change. Understanding of the magnitude of the adaptation challenge at a global scale, however, is incomplete, constrained by a limited understanding of if and how adaptation is taking place. Here we develop and apply a methodology to track and characterize adaptation action; we apply these methods to the peer-reviewed, English-language literature. Our results challenge a number of common assumptions about adaptation while supporting others: (1) Considerable research on adaptation has been conducted yet the majority of studies report on vulnerability assessments and natural systems (or intentions to act), not adaptation actions. (2) Climate change is rarely the sole or primary motivator for adaptation action. (3) Extreme events are important adaptation stimuli across regions. (4) Proactive adaptation is the most commonly reported adaptive response, particularly in developed nations. (5) Adaptation action is more frequently reported in developed nations, with middle income countries underrepresented and low-income regions dominated by reports from a small number of countries. (6) There is limited reporting on adaptations being developed to take advantage of climate change or focusing on women, elderly, or children. 相似文献
29.
Mantle xenoliths in within-plate Cenozoic alkaline mafic lavas from NE Spain are used to assess the local subcontinental lithospheric
mantle geotherm and the influence of melting and metasomatism on its oxidation state. The xenoliths are mainly anhydrous spinel
lherzolites and harzburgites and gradations between, with minor pyroxenites. Most types show protogranular textures, but transitional
protogranular–porphyroclastic and equigranular lherzolites also exist. Different thermometers used in the estimates provide
higher subsolidus equilibrium temperatures for harzburgites (1,062 ± 29°C) than for lherzolites (972 ± 89°C), although there
is overlap; the lowest temperatures correspond to porphyroclastic lherzolites, whereas pyroxenites give the highest temperatures
(up to 1,257°C). Maximum pressures for subsolidus equilibrium of peridotites are at 2.0–1.8 GPa. Later they followed adiabatic
decompression and harzburgites registered lower pressures (1.02 ± 0.19 GPa) than lherzolites (1.41 ± 0.27 GPa). One pyroxenite
gives values consistent with the spinel lherzolite field (1.08 GPa). The shallowest barometric data are in agreement with
the highest local conductive geotherms, which implies that the lithosphere–asthenosphere boundary is at 70–60 km minimum depth.
Higher equilibrium temperatures for the harzburgites could be explained by the existence of mafic magma bodies or dykes at
the lower crust–mantle boundary. Paleo-fO2 conditions during partial melting as inferred from the covariation between V and MgO concentrations are mainly between QFM−1
and QFM−2 in log units. However, most thermobarometric fO2 estimates are between QFM−1 and QFM+1, suggesting oxidation caused by later metasomatism during uplift and cooling. 相似文献
30.
The climate–population relationship has long been conceived. Although the topic has been repeatedly investigated, most of
the related works are Eurocentric or qualitative. Consequently, the relationship between climate and population remains ambiguous.
In this study, fine-grained temperature reconstructions and historical population data sets have been employed to statistically
test a hypothesized relationship between temperature change and population growth (i.e., cooling associated with below average
population growth) in China over the past millennium. The important results were: (1) Long-term temperature change significantly
determined the population growth dynamics of China. However, spatial variation existed, whilst population growth in Central
China was shown to be responsive to both long- and short-term temperature changes; in marginal areas, population growth was
only sensitive to short-term temperature fluctuations. (2) Temporally, the temperature–population relationship was obscured
in some periods, which was attributable to the factors of drought and social buffers. In summary, a temperature–population
relationship was mediated by geographic factors, the aridity threshold, and social factors. Given the upcoming threat posed
by climate change to human societies, this study seeks to improve our knowledge and understanding of the climate–society relationship. 相似文献