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81.
Ana I. Gómez de Castro Javier Lopez-Santiago Paola Sestito Victor Rodrigo Gudiel Fatima López Martínez Elisa de Castro Manuel Cornide Javier Yañez Gestoso 《Astrophysics and Space Science》2011,335(1):97-103
The Gould Belt is the local superassociation of star formation. The age of the Belt is some few 107 yr, henceforth, its population is dominated by luminous young OB associations and low mass pre-main sequence stars. Attempts
to unveil the low mass population have been run making use of the ROSAT all-sky survey. The all sky ultraviolet survey run
by the GALaxy Evolution eXplorer (GALEX) maps several regions in the Belt. In this contribution, we present the preliminary
analysis of the UV stellar population towards the Taurus region, one of the nearest and best studied regions of star formation. 相似文献
82.
A bacterial copper-resistant strain was isolated from a hatchery-conditioned adult of the scallop Argopecten purpuratus and was identified as Vibrio sp. according to its physiological characteristics. The lowest concentration of Cu2+ required for its complete inhibition in VNSS medium was 50 microg ml(-1). The Vibrio strain was found to accumulate copper, exhibiting cellular and loosely bound copper levels of 201.14 and 493.21 microg g(-1) dry weight, respectively, after 24 h of incubation in VNSS medium supplemented with 15 microg ml(-1) of Cu2+, with cellular concentration factors of 10.17 and 14.35 after 12 and 24 h of exposure. When a scallop larvae culture was exposed to a concentration of 6.46 x 10(2) CFU ml(-1) of Cu-enriched Vibrio, they accumulated 20.42 +/- 1.12 and 30.96 +/- 1.85 microg Cu2+ g(-1) dry weight after 12 and 24 h, respectively. This study suggests that bacterial copper accumulation could be very active in marine environments increasing the occurrence of copper transfer to marine food chains. 相似文献
83.
Rodrigo Riera Fernando Tuya Alicia Sacramento Eva Ramos Myriam Rodríguez Óscar Monterroso 《Estuarine, Coastal and Shelf Science》2011
Desalination plants generate notable (>1,000 s m3) quantities of hypersaline brine which potentially affect the biological communities in the receiving area. We assessed whether proximity to a brine discharge point located off Gran Canaria (Canary Islands, eastern Atlantic) altered patterns in the abundance and assemblage structure of subtidal, soft-bottom, meiofauna. Samples were collected twice (May 2008 and January 2009) at 0, 15 and 30 m away from the brine discharge point, corresponding to a change in salinity from 45 to 36. Proximity to the brine discharge point affected overall meiofaunal abundances: lowest abundances were observed at 0 m (64.55 ± 39.86 ind 10 cm−2, mean ± SD) than at 15 (210.49 ± 121.01 ind 10 cm−2) and 30 m (361.88 ± 102.64 ind 10 cm−2) away from the brine discharge point. This pattern was particularly notable for the most conspicuous meiofaunal groups: nematodes and copepods, and meiofaunal assemblage structure also differed with varying proximity to the brine discharge point. Although multivariate techniques identified changes in salinity as a relevant driver of patterns in meiofaunal assemblage structure with varying proximity to the brine outfall, a shift in particle size composition between May 2008 and January 2009 also contributed to explain differences in meiofaunal abundances and assemblage structure with varying proximity to the brine discharge point. Hence, meiofauna can be considered a suitable tool to monitor environmental impacts derived from the discharge of hypersaline effluents on subtidal, soft-bottom, assemblages if potential confounding drivers, i.e. here temporal changes in particle size composition, are accounted for to avoid possible confusing interpretations. 相似文献
84.
Andreas Reisenegger Rodrigo Fernández Paula Jofré 《Astrophysics and Space Science》2007,308(1-4):413-418
The equilibrium composition of neutron star matter is achieved through weak interactions (direct and inverse beta decays),
which proceed on relatively long time scales. If the density of a matter element is perturbed, it will relax to the new chemical
equilibrium through non-equilibrium reactions, which produce entropy that is partly released through neutrino emission, while
a similar fraction heats the matter and is eventually radiated as thermal photons. We examined two possible mechanisms causing
such density perturbations: (1) the reduction in centrifugal force caused by spin-down (particularly in millisecond pulsars),
leading to rotochemical heating, and (2) a hypothetical time-variation of the gravitational constant, as predicted by some theories of gravity and current
cosmological models, leading to gravitochemical heating. If only slow weak interactions are allowed in the neutron star (modified Urca reactions, with or without Cooper pairing),
rotochemical heating can account for the observed ultraviolet emission from the closest millisecond pulsar, PSR J0437-4715,
which also provides a constraint on |dG/dt| of the same order as the best available in the literature.
This work made use of NASA’s Astrophysics Data System Service, and received financial support from FONDECYT through regular
grants 1020840 and 1060644. 相似文献
85.
Gutiérrez Pedro J. Ortiz José L. Rodrigo Rafael López-Moreno José J. Jorda Laurent 《Earth, Moon, and Planets》2002,90(1-4):239-247
A simplified thermal model has been used to calculate thenon-gravitational forces acting on small irregular nuclei in the
orbit ofComet 46P/Wirtanen. The torque of thenon-gravitational force has beencalculated and the Euler equations have been
solved in order toinvestigate the rotational evolution of several irregular nuclei duringa single orbital step. Several initial
spin axis orientations andactivity patterns on their surfaces have been considered. The nucleiconsidered have a mean radius
of 1 km and their inertia moments havebeen calculated assuming a homogeneous bulk density of 500 kg/m3. Inall the simulations, the initial spin period is 6h and the nucleiinitially rotate around their shortest axis. Under these
assumptions,significant changes in the angular momentum and in spin period have beenobtained in all the simulations, but the
nucleus is found to practicallyremain in its spin state of lowest energy during the entire orbitalperiod. 相似文献
86.
Michel Michaelovitch de Mahiques Samara Cazzoli y Goya Maria Carolina da Silva Nogueira de Matos Rodrigo Augusto Udenal de Oliveira Bianca Sung Mi Kim Paulo Alves de Lima Ferreira Rubens Cesar Lopes Figueira Marcia Caruso Bícego 《国际泥沙研究》2021,36(2):317-327
The current study aims to do a comparative analysis of the results obtained with two End-Member(EM)grain-size modeling techniques(AnalySize and BasEMMA)and the Environmental Sensitive Grain-Size(ESGS)modeling for sediment samples collected in the mudbelts of the southern Brazilian shelf.The methods were compared using grain-size data from the south Brazilian shelf,and the results are discussed here.It is the first time that the concept of ESGS,in its present form,is utilized outside China.The results show that despite its relative ease of use,the ESGS is not fully comparable to the EM analyses,and only two grain-size ESGS classes were recognized as analogous to EMs.The comparison of the AnalySize and BasEMMA procedures also revealed significant differences between the techniques.A comparative analysis between the two EM techniques revealed advantages in the BasEMMA,especially in the better correlation of the end-members with the original grain size distribution.The analysis of the geographical distribution of the EM abundances allowed point sources of sandy populations to be recognized as well as the contribution of the Rio de la Plata as a source of silty sediments to be inferred. 相似文献
87.
Analyzing GNSS data in precise point positioning software 总被引:4,自引:1,他引:3
This work demonstrates that precise point positioning (PPP) can be used not only for positioning, but for a variety of other
tasks, such as signal analysis. The fact that the observation model used for accurate error modeling has to take into consideration
the several effects present in GPS signals, and that observations are undifferenced, makes PPP a powerful data analysis tool
sensitive to a variety of parameters. The PPP application developed at the University of New Brunswick, which is called GAPS
(GPS Analysis and Positioning Software), has been designed and built in order to take advantage of available precise products,
resulting in a data analysis tool for determining parameters in addition to position, receiver clock error, and neutral atmosphere
delay. These other estimated parameters include ionospheric delays, code biases, satellite clock errors, and code multipath
among others. In all cases, the procedures were developed in order to be suitable for real-time as well as post-processing
applications. One of the main accomplishments in the development described here is the use of very precise satellite products,
coupled with a very complete observation error modeling to make possible a variety of analyses based on GPS data. In this
paper, several procedures are described, their innovative aspects are pointed out, and their results are analyzed and compared
with other sources. The procedures and software are readily adaptable for using data from other global navigation satellite
systems. 相似文献
88.
We study singular elastic solutions at an angular corner left by a crack that has kinked. We have in mind a geophysical context
where the faults on either side of the kink are under compression and are ready to slip, or have already slipped, under the
control of Coulomb friction. We find separable static singular solutions that are matched across the sides of the corner by
applying appropriate boundary conditions. In our more general solution we assume that one of the sides of the corner is about
to slide, i.e. it is just contained by friction, and the other may be less pressured. Our solutions display power law behaviour
with real exponents that depend continuously on the angle of the corner, the coefficient of static friction and the difference
of shear load on both sides of the corner. When friction is the same on both sides of the kink, the solutions split into a
symmetric and an antisymmetric solution. The antisymmetric solution corresponds to the simple shear case; while the symmetric
solution appears when the kink is loaded by uniaxial stress along the bisector of the kink. The antisymmetric solution is
ruled out under this model with contact since the faults cannot sustain tension. When one side of the corner is less pressured
one can also distinguish modes with contact overall from others that must open up on one side. These solutions provide an
insight into the stress distributions near fault kinks, they can also be used as tools for improving the numerical calculation
of kinks under static or dynamic loads. 相似文献
89.
The large green-tide events that occurred in the Yellow Sea in 2008 (3489 km2) and 2009 (4994 km2) are shown to be novel events preceded only once by a much smaller event in 2007 (82 km2). The blooms originated in the coastal area of Jiangsu province and spread north-east towards the Shandong Peninsula. The blooms grew at different rates and mesoscale variability in surface winds explained the differences in the spatial and temporal patterns of blooms in 2008 and 2009. The 2009 bloom was tracked to its origin immediately offshore of extensive intertidal flats between Yancheng and Nantong where recent rapid expansion of Porphyra aquaculture has occurred. We review published hypotheses which have been advanced to explain the occurrence of blooms and in light of our findings, we conclude that the accumulation and disposal of waste Ulva prolifera from Porphyra aquaculture rafts is the most likely cause of the blooms. 相似文献
90.
Gerdhard L. JessenSilvio Pantoja Marcelo A. GutiérrezRenato A. Quiñones Rodrigo R. GonzálezJavier Sellanes Matthias Y. KellermannKai-Uwe Hinrichs 《Continental Shelf Research》2011,31(6):574-581
We studied for the first time the intertidal and subtidal gas seepage system in Mocha Island off Central Chile. Four main seepage sites were investigated (of which one site included about 150 bubbling points) that release from 150 to 240 tonnes CH4 into the atmosphere per year. The total amount of methane emitted into the atmosphere is estimated in the order of 800 tonnes per year. The gases emanated from the seeps contain 70% methane, and the stable carbon isotopic composition of methane, δ13C-CH4 averaged −44.4±1.4‰ which indicates a major contribution of thermogenic gas. Adjacent to one of the subtidal seeps, rocky substrates support a diverse community of microbial filaments, macroalgae, and benthic organisms. While stable carbon isotopic compositions of marine benthic organisms indicate a dominant photosynthesis-based food web, those of some hard-substrate invertebrates were in the range −48.8‰ to −36.8‰, suggesting assimilation of methane-derived carbon by some selected taxa. This work highlights the potential subsidy of the trophic web by CH4-C, and that its emission to the atmosphere justifies the need of evaluating the use of methane to support the energy requirements of the local community. 相似文献