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101.
Nadiane Smaha Kruk Íria Fernades Vendrame Humberto Ribeiro da Rocha Sin Chan Chou Osvaldo Cabral 《Theoretical and Applied Climatology》2010,99(1-2):115-123
The accurate estimate of the surface longwave fluxes contribution is important for the calculation of the surface radiation budget, which in turn controls all the components of the surface energy budget, such as evaporation and the sensible heat fluxes. This study evaluates the performance of the various downward longwave radiation parameterizations for clear and all-sky days applied to the Sertãozinho region in São Paulo, Brazil. Equations have been adjusted to the observations of longwave radiation. The adjusted equations were evaluated for every hour throughout the day and the results showed good fits for most of the day, except near dawn and sunset, followed by nighttime. The seasonal variation was studied by comparing the dry period against the rainy period in the dataset. The least square linear regressions resulted in coefficients equal to the coefficients found for the complete period, both in the dry period and in the rainy period. It is expected that the best fit equation to the observed data for this site be used to produce estimates in other regions of the State of São Paulo, where such information is not available. 相似文献
102.
Prakki Satyamurty Aline Anderson de Castro Julio Tota Lucia Eliane da Silva Gularte Antonio Ocimar Manzi 《Theoretical and Applied Climatology》2010,99(1-2):139-148
Rainfall series at 18 stations along the major rivers of the Brazilian Amazon Basin, having data since 1920s or 1930s, are analyzed to verify if there are appreciable long-term trends. Annual, rainy-season, and dry-season rainfalls are individually analyzed for each station and for the region as a whole. Some stations showed positive trends and some negative trends. The trends in the annual rainfall are significant at only six stations, five of which reporting increasing trends (Barcelos, Belem, Manaus, Rio Branco, and Soure stations) and just one (Itaituba station) reporting decreasing trend. The climatological values of rainfall before and after 1970 show significant differences at six stations (Barcelos, Belem, Benjamin Constant, Iaurete, Itaituba, and Soure). The region as a whole shows an insignificant and weak downward trend; therefore, we cannot affirm that the rainfall in the Brazilian Amazon basin is experiencing a significant change, except at a few individual stations. Subregions with upward and downward trends are interspersed in space from the far eastern Amazon to western Amazon. Most of the seasonal trends follow the annual trends, thus, indicating a certain consistency in the datasets and analysis. 相似文献
103.
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
104.
I.C.A. da Silveira J.A.M. Lima A.C.K. Schmidt W. Ceccopieri A. Sartori C.P.F. Franscisco R.F.C. Fontes 《Dynamics of Atmospheres and Oceans》2008,45(3-4):187
Temporally-growing frontal meandering and occasional eddy-shedding is observed in the Brazil Current (BC) as it flows adjacent to the Brazilian Coast. No study of the dynamics of this phenomenon has been conducted to date in the region between 22° S and 25°S. Within this latitude range, the flow over the intermediate continental slope is marked by a current inversion at a depth that is associated with the Intermediate Western Boundary Current (IWBC). A time series analysis of 10-current-meter mooring data was used to describe a mean vertical profile for the BC-IWBC jet and a typical meander vertical structure. The latter was obtained by an empirical orthogonal function (EOF) analysis that showed a single mode explaining 82% of the total variance. This mode structure decayed sharply with depth, revealing that the meandering is much more vigorous within the BC domain than it is in the IWBC region. As the spectral analysis of the mode amplitude time series revealed no significant periods, we searched for dominant wavelengths. This search was done via a spatial EOF analysis on 51 thermal front patterns derived from digitized AVHRR images. Four modes were statistically significant at the 95% confidence level. Modes 3 and 4, which together explained 18% of the total variance, are associated with 266 and 338-km vorticity waves, respectively. With this new information derived from the data, the [Johns, W.E., 1988. One-dimensional baroclinically unstable waves on the Gulf Stream potential vorticity gradient near Cape Hatteras. Dyn. Atmos. Oceans 11, 323–350] one-dimensional quasi-geostrophic model was applied to the interpolated mean BC-IWBC jet. The results indicated that the BC system is indeed baroclinically unstable and that the wavelengths depicted in the thermal front analysis are associated with the most unstable waves produced by the model. Growth rates were about 0.06 (0.05) days−1for the 266-km (338-km) wave. Moreover, phase speeds for these waves were low compared to the surface BC velocity and may account for remarks in the literature about growing standing or stationary meanders off southeast Brazil. The theoretical vertical structure modes associated with these waves resembled very closely to the one obtained for the current-meter mooring EOF analysis. We interpret this agreement as a confirmation that baroclinic instability is an important mechanism in meander growth in the BC system. 相似文献
105.
Javier Rodríguez Zaurín Joanna Holt Clive N. Tadhunter Rosa M. González Delgado 《Astrophysics and Space Science》2009,324(2-4):225-229
We use long-slit spectra taken with the William Herschel Telescope on La Palma and high-resolution Hubble Space Telescope imaging to study the gas kinematic in the halo of the ultraluminous infrared/radio galaxy PKS1345+12 (z=0.122). Our long-slit spectra show line splitting at the locations of massive star clusters ( $10^{6}<M_{\mathrm{SSC}}^{\mathrm{YSP}}<10^{7}$ M⊙), indicating that they are moving at up to 450 km?s?1 with respect to the local ambient gas. Given their kinematics, it is plausible that these super star clusters have been formed either in fast-moving gas streams or tidal tails that are falling back into the nuclear regions as part of the merger process, or as a consequence of jet-induced star formation linked to the extended, diffuse radio emission detected in the halo of the galaxy. 相似文献
106.
Enrique Pérez Richard de Grijs Rosa M. González Delgado 《Astrophysics and Space Science》2009,324(2-4):79-81
107.
108.
Antonio C. da Silva rea Catalano Ludovic Montier Etienne Pointecouteau Joseph Lanoux Martin Giard 《Monthly notices of the Royal Astronomical Society》2009,396(2):849-859
We investigate the effect of dust on the scaling properties of galaxy clusters based on hydrodynamic N -body simulations of structure formation. We have simulated five dust models plus radiative cooling and adiabatic models using the same initial conditions for all runs. The numerical implementation of dust was based on the analytical computations of Montier & Giard. We set up dust simulations to cover different combinations of dust parameters that make evident the effects of size and abundance of dust grains. Comparing our radiative plus dust cooling runs with a purely radiative cooling simulation, we find that dust has an impact on cluster scaling relations. It mainly affects the normalization of the scalings (and their evolution), whereas it introduces no significant differences in their slopes. The strength of the effect critically depends on the dust abundance and grain size parameters as well as on the cluster scaling. Indeed, cooling due to dust is effective in the cluster regime and has a stronger effect on the 'baryon driven' statistical properties of clusters such as L X – M , Y – M , S – M scaling relations. Major differences, relative to the radiative cooling model, are as high as 25 per cent for the L X – M normalization, and about 10 per cent for the Y – M and S – M normalizations at redshift zero. On the other hand, we find that dust has almost no impact on the 'dark matter driven' T mw – M scaling relation. The effects are found to be dependent in equal parts on both dust abundances and grain size distributions for the scalings investigated in this paper. Higher dust abundances and smaller grain sizes cause larger departures from the radiative cooling (i.e. with no dust) model. 相似文献
109.
Sandro Conticelli Sara Marchionni Davide Rosa Guido Giordano Elena Boari Riccardo Avanzinelli 《Contributions to Mineralogy and Petrology》2009,157(1):41-63
The Roccamonfina volcano is characterised by two stages of volcanic activity that are separated by volcano-tectonic caldera
collapses. Ultrapotassic leucite-bearing rocks are confined to the pre-caldera stage and display geochemical characteristics
similar to those of other volcanoes in the Roman Province. After the major sector collapse of the volcano, occurred at ca.
400 ka, shoshonitic rocks erupted from cinder cones and domes both within the caldera and on the external flanks of the pre-caldera
Roccamonfina volcano. On the basis of new trace element and Sr–Nd–Pb isotope data, we show that the Roccamonfina shoshonitic
rocks are distinct from shoshonites of the Northern Roman Province, but are very similar to those of the Neapolitan volcanoes.
The last phases of volcanic activity erupted sub-alkaline magmas as enclaves in trachytic domes, and as lavas within the Monte
Santa Croce dome. Ultrapotassic rocks of the pre-caldera composite volcano are plagioclase-bearing leucitites characterised
by high levels of incompatible trace elements with an orogenic signature having troughs at Ba, Ta, Nb, and Ti, and peaks at
Cs, K, Th, U, and Pb. Initial values of 87Sr/86Sr range from 0.70926 to 0.70999, 143Nd/144Nd ranges from 0.51213 to 0.51217, while the lead isotope rations vary between 18.788–18.851 for 206Pb/204Pb, 15.685–15.701 for 207Pb/204Pb, and 39.048–39.076 for 208Pb/204Pb. Shoshonites show a similar pattern of trace element depletions and enrichments to the earlier ultrapotassic leucite-bearing
rocks but have a larger degree of differentiation and lower concentrations of incompatible trace elements. On the other hand,
shoshonitic rocks have Sr, Nd, and Pb isotopes consistently different than pre-caldera ultrapotassic leucite-bearing rocks.
87Sr/86Sr ranges from 0.70665 to 0.70745, 143Nd/144Nd ranges from 0.51234 to 0.51238, 206Pb/204Pb ranges from 18.924 to 19.153, 207Pb/204Pb ranges from 15.661 to 15.694, and 208Pb/204Pb ranges from 39.084 to 39.212. High-K calc-alkaline samples have intermediate isotopic values between ultrapotassic plagioclase
leucitites and shoshonites, but the lowest levels of incompatible trace element contents. It is argued that ultrapotassic
magmas were generated in a modified lithospheric mantle after crustal-derived metasomatism. Interaction between the metasomatic
agent and lithospheric upper mantle produced a low-melting point metasomatised veined network. The partial melting of the
veins alone produced pre-caldera leucite-bearing ultrapotassic magmas. It was possibly triggered by either post-collisional
isotherms relaxation or increasing T°C due increasing heat flow through slab tears. Shoshonitic magmas were generated by further melting, at higher temperature,
of the same metasomatic assemblage with addition 10–20% of OIB-like astenospheric mantle material. We suggest that addition
of astenospheric upper mantle material from foreland mantle, flowing through slab tearing after collision was achieved.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
110.
The broad-spectrum herbicide glyphosate has become the largest-selling crop-protection product worldwide. The increased use of glyphosate is associated with the appearance of a growing number of tolerant or resistant weeds, with socio-environmental consequences apart from the loss of productivity. In 2002, a glyphosate-resistant biotype of johnsongrass (Sorghum halepense (L.)) appeared in Argentina and now covers at least 10,000 ha. This paper analyzes the driving forces behind the emergence and spread of this weed and also examines management responses and their implications.Preventive strategies against glyphosate-resistant johnsongrass fail because of the institutional setting. Reactive measures, however, transfer the risks to the society and the environment through the introduction of novel genetically modified crops that allow the use of yet more herbicide. This in turn reinforces the emergence of herbicide-resistant weeds, constituting a new phenomenon of intensification, the “transgenic treadmill”. 相似文献