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421.
422.
Franck Touratier Catherine Goyet 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1708-1716
Monthly observations accumulated over more than a decade at the DYFAMED time-series station allow us to estimate the temporal evolution of anthropogenic CO2 in the western Mediterranean Sea. This objective is reached by using recognized interpolation procedures to reconstruct the incomplete distributions of measured total dissolved inorganic carbon and total alkalinity. These reconstructed fields, associated with those available for dissolved oxygen and temperature, are used to estimate the distribution of anthropogenic CO2. This is done with the recently developed Tracer combining Oxygen, inorganic Carbon, and total alkalinity (TrOCA) approach. The main results indicate that (1) the concentrations of anthropogenic CO2 are much higher than those found in the Atlantic Ocean (the minimum concentration at the DYFAMED site is 50 μmol kg−1), and (2) the temporal trend for anthropogenic CO2 is decreasing, especially in the intermediate and the deep layers of the water column at the DYFAMED site. This decrease in anthropogenic CO2 is significantly correlated with a decrease in the dissolved oxygen and with an increase in both salinity and temperature. These trends are discussed in the light of recent published works that propose explanations for the observed increases in salinity and temperature that occurred in the western basin since the 1950s. We conclude that the decrease in anthropogenic CO2 probably resulted from an invasion of old water masses. Different hypotheses on the origin of these water masses are considered and several arguments indicate that the eastern Mediterranean transient (EMT) could have played an important role in the observed decrease in anthropogenic CO2 concentrations at the DYFAMED site. 相似文献
423.
Gilbert Bellaiche 《Marine Geology》1975,19(2):M1-M6
The interpretation of sedimentological and geochronological results lead us to the conclusion that the sedimentary levees flanking the deep-sea channels of the Rhône deep-sea fan are made up of various kinds of turbidites originating from different coastal areas and were deposited during the Quaternary glacial epochs. 相似文献
424.
In this article, we present a numerical method to deal with fluid–solid interactions and simulate particle–fluid systems as encountered in soils. This method is based on a coupling between two methods, now widely used in mechanics of granular media and fluid dynamics respectively: the discrete element (DE) method and the lattice Boltzmann (LB) method. The DE method is employed to model interactions between particles, whereas the LB method is used to describe an interstitial Newtonian fluid flow. The coupling presented here is a full one in the sense that particle motions act on fluid flow and reciprocally. This article presents in details each of the two methods and the principle of the coupling scheme. Determination of hydrodynamic forces and torques is also detailed, and the treatment of boundaries is explained. The coupled method is finally illustrated on a simple example of piping erosion, which puts in evidence that the combined LB–DE scheme constitutes a promising tool to study coupled problems in geomechanics. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
425.
Z. Garai T. Pribulla
. Hamblek R. Errmann Ch. Adam S. Buder T. Butterley V. S. Dhillon B. Dincel H. Gilbert Ch. Ginski L. K. Hardy A. Kellerer M. Kitze E. Kundra S. P. Littlefair M. Mugrauer J. Nedoro
ík R. Neuhuser A. Pannicke S. Raetz J. G. Schmidt T. O. B. Schmidt M. Seeliger M. Vako R. W. Wilson 《Astronomische Nachrichten》2016,337(3):261-285
We report results of the first five observing campaigns for the open stellar cluster NGC 7243 in the frame of project Young Exoplanet Transit Initiative (YETI). The project focuses on the monitoring of young and nearby stellar clusters, with the aim to detect young transiting exoplanets and to study other variability phenomena on time‐scales from minutes to years. After five observing campaigns and additional observations during 2013 and 2014, a clear and repeating transit‐like signal was detected in the light curve of J221550.6+495611. Furthermore, we detected and analysed 37 new eclipsing binary stars in the studied region. The best fit parameters and light curves of all systems are given. Finally, we detected and analysed 26 new, presumably pulsating variable stars in the studied region. The follow‐up investigation of these objects, including spectroscopic measurements of the exoplanet candidate, is currently planned. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
426.
The 1D version of the Model for Applications at Regional Scale is used to parameterize the effects of sea surface waves in
2D in a horizontally homogeneous offshore zone of the Iroise sea. Here we present the first simulation of the Iroise sea including
sea surface waves forcing, and more generally, the first study of a boundary layer including the Hasselmann force with a tidal
wave. We use a single equation turbulence closure based on a non-local diagnosis for energetic and dissipation length scales.
The turbulent energy flux at the surface due to whitecaps and the Hasselmann force induced by Stokes drift are assessed using
the whole sea surface waves spectrum given by the Wave Watch Third generation model. The ability of the parameterization to
reproduce surface currents over a period of 1 year (2007) is tested with high frequency radar using spectral and time-frequency
analysis. One problem with 1D modelling, corresponding to overestimation of current oscillating at inertial frequency is illustrated
by comparing 1D and 3D simulations. We found an overall improvement by including the Hasselmann force mainly within the bandwidth
of less than one cycle per day to one cycle per day for surface currents. Turbulence is induced by whitecaps decaying rapidly
below the ocean surface but the mixed layer below 40 m is deeper due to waves breaking on the sea surface. 相似文献
427.
Strombolian-type volcanic activity is characterized by a series of gas bubbles bursting at the top of a magma column and leading
to the ejection of lava clots and gas emission at the surface. The quantitative analysis of physical parameters (e.g., velocity,
size, and mass fluxes) controlling the emission dynamics of these volcanic products is very important for the understanding
of eruption source mechanisms but remains difficult to obtain in a systematic fashion. Ground-based Doppler radar is found
to be a very effective tool for measuring ejecta velocities at a high acquisition rate and close to the emission source. We
present here a series of measurements carried out at Mt. Etna’s Southeast crater, using an L-band volcanological Doppler radar,
during the 4 July 2001 Strombolian eruptions. Doppler radar data are supplemented by the analysis of video snapshots recorded
simultaneously. We provide here a set of physical parameters systematically retrieved from 247 Strombolian explosions spanning
15 min and occurring during the paroxysm of the eruption from 21:30 to 21:45 UT. The time-average values give a maximum particle
velocity of
Vmaxp = 94.7±24 \textm/s V_{{\max }}^p = {94}.{7}\pm {24} {\text{m/s}} , a bulk lava jet velocity of
V\textPW - rad = 37.6±1.9 \textm/s {V_{{{\text{PW - rad}}}}} = {37}.{6}\pm {1}.{9} {\text{m/s}} , and an initial gas velocity at the source vent of
V0g = 118.4±36 \textm/s V_0^g = {118}.{4}\pm {36} {\text{m/s}} . The time-averaged particle diameter is found to be about
D\textPW - rad = 4.2±2.1 \textcm {D_{{{\text{PW - rad}}}}} = {4}.{2}\pm {2}.{1} {\text{cm}} . The volume and mass gas fluxes are estimated from time-averaged source gas velocities over the sequence duration at
Qvg = 3 - 11 ×103\textm3\text/s Q_v^g = {3} - {11} \times {1}{0^{{3}}}{{\text{m}}^{{3}}}{\text{/s}} and
Qmg = 0.5 - 2 ×103\textkg/s Q_m^g = 0.{5} - {2} \times {1}{0^{{3}}}{\text{kg/s}} , respectively. 相似文献
428.
Assessing the use of global land cover data for guiding large area population distribution modelling
Gridded population distribution data are finding increasing use in a wide range of fields, including resource allocation,
disease burden estimation and climate change impact assessment. Land cover information can be used in combination with detailed
settlement extents to redistribute aggregated census counts to improve the accuracy of national-scale gridded population data.
In East Africa, such analyses have been done using regional land cover data, thus restricting application of the approach
to this region. If gridded population data are to be improved across Africa, an alternative, consistent and comparable source
of land cover data is required. Here these analyses were repeated for Kenya using four continent-wide land cover datasets
combined with detailed settlement extents and accuracies were assessed against detailed census data. The aim was to identify
the large area land cover dataset that, combined with detailed settlement extents, produce the most accurate population distribution
data. The effectiveness of the population distribution modelling procedures in the absence of high resolution census data
was evaluated, as was the extrapolation ability of population densities between different regions. Results showed that the
use of the GlobCover dataset refined with detailed settlement extents provided significantly more accurate gridded population
data compared to the use of refined AVHRR-derived, MODIS-derived and GLC2000 land cover datasets. This study supports the
hypothesis that land cover information is important for improving population distribution model accuracies, particularly in
countries where only coarse resolution census data are available. Obtaining high resolution census data must however remain
the priority. With its higher spatial resolution and its more recent data acquisition, the GlobCover dataset was found as
the most valuable resource to use in combination with detailed settlement extents for the production of gridded population
datasets across large areas. 相似文献
429.
Maarten Van Daele Aurélien van Welden Jasper Moernaut Christian Beck Franck Audemard Javier Sanchez François Jouanne Eduardo Carrillo Gustavo Malavé Andrés Lemus Marc De Batist 《Marine Geology》2011,279(1-4):37-51
The Gulf of Cariaco is a marginal basin located between the Cariaco Basin and the Paria Gulf, offshore NE Venezuela, along a system of active right-lateral strike-slip faults. It is connected to the Caribbean Sea via a shallow 58-m-deep sill implying that the gulf was disconnected from the global ocean during eustatic lowstands. A dense grid of high-resolution reflection seismic profiles has been used to determine the overall tectonic structure of the gulf and to establish the seismic stratigraphy of its sedimentary infill. Six unconformity-bounded seismic–stratigraphic units were identified in the upper ~ 200 m of the sedimentary infill. Detailed seismic–stratigraphic and seismic-facies analysis allowed defining a series of sedimentary features that can be used as indicators of past sea or lake level in the Gulf of Cariaco: i) delta offlap breaks, ii) evaporites, and iii) erosional unconformities. Using accurate measurements of these various indicators at several locations in the gulf and a simple total subsidence model, a relative sea/lake-level history encompassing the last 130 kyr could be reconstructed. In periods of connection with the open ocean, reconstructed relative sea level correlates well with eustatic sea level. In times of disconnection, distinct lake-level fluctuations occurred, which sometimes resulted in total dessication of the gulf. Lake-level fluctuations appear to correlate with major Heinrich Events, stadials and interstadials. MIS 4, the LGM and the Younger Dryas were thus identified in the Gulf of Cariaco sedimentary record. The last reconnection to the Caribbean Sea occurred during MWP1b (around 11.5 kyr). The very good fit of the Cariaco sea/lake-level curve with the eustatic sea-level curves (both in terms of amplitude and of timing) underscores potential for future paleoclimate research of the sedimentary record contained in this marginal basin, despite its active tectonic setting. 相似文献
430.
Claire Seard Gilbert Camoin Yusuke Yokoyama Hiroyuki Matsuzaki Nicolas Durand Edouard Bard Sophie Sepulcre Pierre Deschamps 《Marine Geology》2011,279(1-4):63-86
The widespread occurrence of microbialites in the last deglacial reef frameworks (16–6 Ka BP) implies that the accurate study of their development patterns is of prime importance to unravel the evolution of reef architecture through time and to reconstruct the reef response to sea-level variations and environmental changes.The present study is based on the sedimentological and chronological analysis (14C AMS dating) of drill cores obtained during the IODP Expedition #310 “Tahiti Sea Level” on the successive terraces which typify the modern reef slopes from Tahiti. It provides a comprehensive data base to investigate the microbialite growth patterns (i.e. growth rates and habitats), to analyze their roles in reef frameworks and to reconstruct the evolution of the reef framework architecture during sea-level rise.The last deglacial reefs from Tahiti are composed of two distinctive biological communities: (1) the coralgal communities including seven assemblages characterized by various growth forms (branching, robust branching, massive, tabular and encrusting) that form the initial frameworks and (2) the microbial communities developed in the primary cavities of those frameworks, a few meters (1.5 to 6 m) below the living coral reef surface, where they heavily encrusted the coralgal assemblages to form microbialite crusts. The dating results demonstrate the occurrence of two distinctive generations of microbialites: the “reefal microbialites” which developed a few hundred years after coralgal communities in shallow-water environments, whereas the “slope microbialites” grew a few thousands of years later in significantly deeper water conditions after the demise of coralgal communities.The development of microbialites was controlled by the volume and the shape of the primary cavities of the initial reef frameworks determined by the morphology and the packing of coral colonies. The most widespread microbialite development occurred in frameworks dominated by branching, thin encrusting, tabular and robust branching coral colonies which built loose and open frameworks typified by a high porosity (> 50%). In contrast, their growth was minimal in compact coral frameworks formed by massive and thick encrusting corals where primary cavities yielded a low porosity (~ 30%) and could not host a significant microbialite expansion. 相似文献