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151.
Background
The voluntary carbon market is a new and growing market that is increasingly important to consider in managing forestland. Monitoring, reporting, and verifying carbon stocks and fluxes at a project level is the single largest direct cost of a forest carbon offset project. There are now many methods for estimating forest stocks with high accuracy that use both Airborne Laser Scanning (ALS) and high-resolution optical remote sensing data. However, many of these methods are not appropriate for use under existing carbon offset standards and most have not been field tested. 相似文献152.
The global and regional projected changes in tropical cyclone (TC) genesis due to increased CO2 concentrations has been investigated through a large-scale TC genesis parameter (convective seasonal genesis parameter, ConvGP) in two perturbed physics ensembles. The ensembles are based on the third generation Hadley Centre atmosphere?Cocean general circulation model with the first ensemble using a coupled fully dynamic ocean (HadCM3) and the second coupled to a simplified mixed layer thermodynamic ocean (HadSM3) both consisting of 17 members. In each ensemble, parameters are identically perturbed to provide a wide range of climate sensitivity whilst retaining a credible present-day climate simulation. It is found, by comparing the ConvGP climatology from reanalysis data with the best track genesis, that it is possible to reproduce the observed genesis distribution. Future changes in the spatial ConvGP distribution are explored with respect to each tropical ocean basin. Whilst there is a similarity in the gross pattern of the ensemble-mean projected ConvGP change between HadCM3 and HadSM3, there is a non-trivial difference in the tropical Pacific Ocean, arising from different patterns of tropical Pacific sea surface temperature change. This indicates that ocean representation can be important for regional scale projections. The quantitative contribution of individual constituent parameters (i.e. vorticity parameter, shear parameter and convective potential) to the projected ConvGP change is estimated. It is found that all three large-scale parameters generally contribute constructively, but with different magnitude, in the regions where a large doubled CO2 response is found. 相似文献
153.
Understanding the impact of climate change on Northern Hemisphere extra-tropical cyclones 总被引:3,自引:2,他引:1
Ruth E. McDonald 《Climate Dynamics》2011,37(7-8):1399-1425
Extra-tropical cyclones strongly influence weather and climate in mid-latitudes and any future changes may have large impacts on the local scale. In this study Northern Hemisphere storms are analysed in ensembles of time-slice experiments carried out with an atmosphere only model with present day and future anthropogenic emissions. The present day experiment is forced by observed sea-surface temperature and sea-ice. The sea-surface temperatures and sea-ice for the future experiment are derived by adding anomalies, from parallel but lower resolution coupled model experiments, to the observed data. The storms in the present day simulation compare fairly well with observations in all seasons but some errors remain. In the future simulations there is some evidence of a poleward shift in the storm tracks in some seasons and regions. There are fewer cyclones in the Northern Hemisphere in winter and spring. The northeast end of the North Atlantic storm track is shifted south in winter giving more storms and increased frequency of strong winds over the British Isles. This shift is related to an increase in baroclinicity and a southward shift of the jet that occurs as a response to a minimum in ocean warming in the central North Atlantic. An increase in the frequency of storms over the UK is likely to cause enhanced levels of wind and flood damage. These results concur with those from some other models, however, large uncertainties remain. 相似文献
154.
Robert Graves Thomas H. Jordan Scott Callaghan Ewa Deelman Edward Field Gideon Juve Carl Kesselman Philip Maechling Gaurang Mehta Kevin Milner David Okaya Patrick Small Karan Vahi 《Pure and Applied Geophysics》2011,168(3-4):367-381
CyberShake, as part of the Southern California Earthquake Center??s (SCEC) Community Modeling Environment, is developing a methodology that explicitly incorporates deterministic source and wave propagation effects within seismic hazard calculations through the use of physics-based 3D ground motion simulations. To calculate a waveform-based seismic hazard estimate for a site of interest, we begin with Uniform California Earthquake Rupture Forecast, Version 2.0 (UCERF2.0) and identify all ruptures within 200?km of the site of interest. We convert the UCERF2.0 rupture definition into multiple rupture variations with differing hypocenter locations and slip distributions, resulting in about 415,000 rupture variations per site. Strain Green Tensors are calculated for the site of interest using the SCEC Community Velocity Model, Version 4 (CVM4), and then, using reciprocity, we calculate synthetic seismograms for each rupture variation. Peak intensity measures are then extracted from these synthetics and combined with the original rupture probabilities to produce probabilistic seismic hazard curves for the site. Being explicitly site-based, CyberShake directly samples the ground motion variability at that site over many earthquake cycles (i.e., rupture scenarios) and alleviates the need for the ergodic assumption that is implicitly included in traditional empirically based calculations. Thus far, we have simulated ruptures at over 200 sites in the Los Angeles region for ground shaking periods of 2?s and longer, providing the basis for the first generation CyberShake hazard maps. Our results indicate that the combination of rupture directivity and basin response effects can lead to an increase in the hazard level for some sites, relative to that given by a conventional Ground Motion Prediction Equation (GMPE). Additionally, and perhaps more importantly, we find that the physics-based hazard results are much more sensitive to the assumed magnitude-area relations and magnitude uncertainty estimates used in the definition of the ruptures than is found in the traditional GMPE approach. This reinforces the need for continued development of a better understanding of earthquake source characterization and the constitutive relations that govern the earthquake rupture process. 相似文献
155.
D. A. Holwell I. McDonald I. B. Butler 《Contributions to Mineralogy and Petrology》2011,161(6):1011-1026
Magmatic sulfide deposits are the most significant source of platinum-group elements (PGE) in the world. Key to understanding
their genesis is determining the processes and timing of sulfide saturation, metal enrichment and crustal contamination. In
this study, we have identified droplets of magmatic sulfide from the Platreef, South Africa, where droplets of sulfide have
been trapped in the earliest crystallising phase, chromite. Due to their early entrapment at high temperatures, metal concentrations
and ratios that they display are indicative of a very early-stage sulfide liquid in the system, as they will have cooled and
fractionated within an essentially closed system, unlike interstitial blebs that crystallise in an open system as the magma
cools. Analysis of these droplets in an opaque mineral like chromite by LA-ICP-MS is problematic as some of the fractionated
inclusion is necessarily lost during cutting and polishing to initially identify the inclusion. This particularly affects
the ability to representatively sample the most fractionated phases such as gold and platinum minerals. Here, using a novel
technique whereby the inclusions are homogenized and quickly quenched, so that any cutting, polishing and subsequent LA-ICP-MS
analysis samples a truly representative portion of the droplet. This has been used to show that early sulfide liquids in the
Platreef were highly PGE-rich and had Pt/Pd ratios of close to unity that supports genetic models invoking sulfide saturation
and metal enrichment prior to intrusion, with pre-enriched sulfides entrained within the Platreef magma. 相似文献
156.
The sorption of selenium(VI) onto pure anatase, a polymorph of titanium dioxide, was investigated. At the macroscopic level, batch experiments and electrophoretic mobility measurements were performed. Selenium(VI) retention was found to be pH-dependent, i.e. sorption of selenium(VI) decreases with increasing pH (pH range 3.5-11). Selenium(VI) sorption dependence on the ionic strength was also evidenced, i.e. sorption increases while the ionic strength decreases. Electrophoretic mobility measurements showed that selenium(VI) sorption had no effect on the isoelectric point of anatase. At the microscopic level, XPS (X-ray Photoelectron Spectroscopy) measurements evidenced the absence of reduction of selenium(VI) during the sorption process. Furthermore, the nature of the sorbed surface species at the anatase/liquid interface was elucidated using Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) spectroscopy. The spectroscopic results strongly suggested the formation of outer-sphere complexes on the whole pH range, in agreement with batch sorption experiments and electrophoretic mobility findings. 相似文献
157.
Achim G. Reisdorf Andreas Wetzel Rudolf Schlatter Peter Jordan 《Swiss Journal of Geoscience》2011,104(1):97-146
The deposits of the Early Jurassic in northern Switzerland accumulated in the relatively slowly subsiding transition zone
between the southwestern part of the Swabian basin and the eastern part of the Paris basin under fully marine conditions.
Terrigenous fine-grained deposits dominate, but calcarenitic and phosphorit-rich strata are intercalated. The total thickness
varies between 25 and 50 m. In the eastern and central parts of N Switzerland, sediments Sinemurian in age constitute about
90% of the total thickness. To the West, however, in the Mont Terri area, Pliensbachian and Toarcian deposits form 70% of
the total thickness. Stratigraphic gaps occur on a local to regional scale throughout N Switzerland. Such hiatus comprise
a subzone to a stage in time. With respect to lithology and fossil content, the Early Jurassic deposits in northern Switzerland
are similar to those in SW Germany. Nonetheless, an exact stratigraphic correlation is hardly possible, particulary in the
southern and southwestern Folded Jura where distinct facies changes occur over short distances. Revised existing and new litho-
and biostratigraphic data form the base to refine the stratigraphic subdivision of the deposits that have been informally
called “Lias”. The name Staffelegg Formation is suggested and defined as the mapping unit for the Early Jurassic. The Staffelegg
Formation is introduced for Early Jurassic sediments in northern Switzerland between the Doubs River and Mt. Weissenstein
in the west and the Randen Hills located north of the city of Schaffhausen in the east. The Staffelegg Formation starts within
the Planorbis zone of the Hettangian. The upper boundary to the overlying Aalenian Opalinus-Ton is diachronous. The lithostratigraphic
names previously in use have been replaced by new ones, in accordance within the rules of lithostratigraphic nomenclature.
The Staffelegg Formation comprises 11 members and 9 beds. Several of these beds are important correlation horizons in terms
of allostratigraphy. Some of them correspond to strata or erosional unconformities encountered in the Swabian realm, some
of them can be correlated with strata in the Paris basin. The facies transition to the Paris basin is expressed by introduction
of a corresponding lithostratigraphic unit. 相似文献
158.
Martin Danišík Jaroslav Kadlec Christoph Glotzbach Anett Weisheit István Dunkl Milan Kohút Noreen J. Evans Monika Orvošová Brad J. McDonald 《Swiss Journal of Geoscience》2011,104(2):285-298
A combination of four thermochronometers [zircon fission track (ZFT), zircon (U–Th)/He (ZHe), apatite fission track (AFT)
and apatite (U–Th–[Sm])/He (AHe) dating methods] applied to a valley to ridge transect is used to resolve the issues of metamorphic,
exhumation and topographic evolution of the Nízke Tatry Mts. in the Western Carpathians. The ZFT ages of 132.1 ± 8.3, 155.1 ± 12.9,
146.8 ± 8.6 and 144.9 ± 11.0 Ma show that Variscan crystalline basement of the Nízke Tatry Mts. was heated to temperatures
>210°C during the Mesozoic and experienced a low-grade Alpine metamorphic overprint. ZHe and AFT ages, clustering at ~55–40
and ~45–40 Ma, respectively, revealed a rapid Eocene cooling event, documenting erosional and/or tectonic exhumation related
to the collapse of the Carpathian orogenic wedge. This is the first evidence that exhumation of crystalline cores in the Western
Carpathians took place in the Eocene and not in the Cretaceous as traditionally believed. Bimodal AFT length distributions,
Early Miocene AHe ages and thermal modelling results suggest that the samples were heated to temperatures of ~55–90°C during
Oligocene–Miocene times. This thermal event may be related either to the Oligocene/Miocene sedimentary burial, or Miocene
magmatic activity and increased heat flow. This finding supports the concept of thermal instability of the Carpathian crystalline
bodies during the post-Eocene period. 相似文献
159.
Hamish A. Malcolm Peter L. DaviesAlan Jordan Stephen D.A. Smith 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(5):616-627
Improved understanding of the East Australian Current (EAC) and sea-temperature patterns within the Solitary Islands region of northern New South Wales, an area where tropical and temperate faunas overlap, is an essential step in explaining cross-shelf gradients in biotic patterns. Sea temperature at ∼10 m was logged using thermistors at seven stations every 30 minutes between January 2001 and December 2008. Stations were replicated in three distance-from-shore categories (<1.5; 1.5 to 6; and >6 km from the coast), corresponding with predominant assemblage patterns of reef fish. Daily, monthly, seasonal and yearly sea-temperature patterns were compared between and within stations and distance-from-shore categories. SST images were examined to determine the role of the EAC in producing short-period (2 to 4 days) temperature anomalies. Sea temperatures ranged between 16.6-27.5 °C and were highest offshore and lowest inshore. Offshore sites experienced average temperatures ∼1 °C higher than nearshore sites over the 8-year study. There was considerable variation in sea temperature between years, with 2002 and 2006 being the warmest and 2007 the coolest. These patterns correspond with strong inter-annual variability of the EAC at the scale of the Solitary Islands region. The EAC influenced shelf waters most strongly during late spring/summer when temperatures were also most variable over the smallest temporal scales (hours, days). Short-period anomalies between and within stations could largely be explained by variable encroachment of the EAC across the shelf and/or colder intrusions of water forming adjacent to the coastline. Previous assumptions that the EAC strongly influences gradients in the distribution of tropical species in this nearshore region are strongly supported. 相似文献
160.
Buffelgrass invasions have been documented in Australia to North America, pointing to an end result of large-scale wildfires. In heavily populated areas such as Nogales, Sonora and Tucson and Phoenix, Arizona buffelgrass populations are growing exponentially. Although much research has been conducted on buffelgrass, relatively little is known about fire behaviors produced by a buffelgrass-fueled fire. To determine which abiotic and biotic characteristics best predict fire behavior, fire-behavior characteristics were measured in four prescribed fires in southern Arizona. Given that buffelgrass is known to decrease native plant richness in other ecosystems, the relationship between buffelgrass abundance and native plant cover was evaluated. Buffelgrass fires are more intense than fires in surrounding ecosystems, even in communities with comparable fuels. There is a strong negative relationship between buffelgrass cover and native plant cover. In addition, buffelgrass appears to be invading favorable microsites rather than species-poor communities and is radiating from the former sites. Historically, fire was rare in arid regions, but with the increase in fuels and because arid regions have weather that promotes intense fire behavior, as observed in this study, managers will increasingly observe and need to mitigate hazardous fires. 相似文献