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81.
A. Ebert D. Rieke-Zapp M. Herwegh K. Ramseyer E. Gnos D. Decrouez 《Tectonophysics》2009,463(1-4):175-184
A new approach to quantify microstructures of coarse-grained marbles is presented. This technique is based on the intensity of light reflectance in dependence of the crystallographic orientation of calcite grains. The technique setup consists of a high-resolution camera, a strong light source and the polished sample in reflection position. Microstructural data obtained with this method are comparable with those obtained by light microscopy or by secondary electron microscopy. However, the new approach reflects the grain size distribution even more accurately than in the case of other techniques, because it allows an easy quantification of larger sample surfaces. Therefore, in contrast to established techniques, microstructural analysis and statistics can also be performed for coarse-grained samples with grains that exceed diameters of 1 cm. With this new technique, coarse-grained mylonitic microstructures from Naxos were quantified, which in turn allowed relating different microfabrics to different strain localization episodes within a large-scale shear zone complex. 相似文献
82.
Volcanic eruptions can overwhelm all senses of observers in their violence, spectacle and sheer incredibility. When an eruption is catastrophic or unexpected, neither individuals nor communities can easily assimilate the event into their world view. Psychological studies of disaster aftermaths have shown that trauma can shake the very foundations of a person's faith and trigger a search – supernatural, religious, or scientific – for answers. For this reason, the ability to rapidly comprehend a traumatic event by “accepting” the catastrophe as part the observer's world represents an important component of community resilience to natural hazards. A relationship with the event may be constructed by adapting existing cosmological, ancestral, or scientific frameworks, as well as through creative and artistic expression. In non-literate societies, communal perceptions of an event may be transformed into stories that offer myth-like explanations. As these stories make their way into oral traditions, they often undergo major changes to allow transmission through generations and, in some cases, to serve political or religious purposes. Disaster responses in literate societies are no different, except that they are more easily recorded and therefore are less prone to change over time. 相似文献
83.
Michael B. Turner Shane J. Cronin Mark S. Bebbington Thomas Platz 《Bulletin of Volcanology》2008,70(4):507-515
The majority of continental arc volcanoes go through decades or centuries of inactivity, thus, communities become inured to
their threat. Here we demonstrate a method to quantify hazard from sporadically active volcanoes and to develop probabilistic
eruption forecasts. We compiled an eruption-event record for the last c. 9,500 years at Mt Taranaki, New Zealand through detailed
radiocarbon dating of recent deposits and a sediment core from a nearby lake. This is the highest-precision record ever collected
from the volcano, but it still probably underestimates the frequency of eruptions, which will only be better approximated
by adding data from more sediment core sites in different tephra-dispersal directions. A mixture of Weibull distributions
provided the best fit to the inter-event period data for the 123 events. Depending on which date is accepted for the last
event, the mixture-of-Weibulls model probability is at least 0.37–0.48 for a new eruption from Mt Taranaki in the next 50 years.
A polymodal distribution of inter-event periods indicates that a range of nested processes control eruption recurrence at
this type of arc volcano. These could possibly be related by further statistical analysis to intrinsic factors such as step-wise
processes of magma rise, assembly and storage. 相似文献
84.
Shane Paul Griffiths 《International Journal of Salt Lake Research》1999,8(4):307-327
The consequences of artificially opening lagoon entrances on the fish assemblages of coastal lagoons in south-eastern Australia
were investigated. Impacts of lagoon opening were assessed by comparing changes in the fish assemblages of Werri and Shellharbour
Lagoons, both of which intermittently opened to the sea with that of Lake Illawarra, a third coastal lagoon which remained
closed during the study period. Numbers of fish species and individuals did not differ significantly after lagoon openings
at Werri Lagoon and Shellharbour Lagoon. However, higher numbers of species and individuals were found in Lake Illawarra before
the other lagoons had opened. Abundances of some economically significant species (namelyMugil cephalus, Myxus elongatus andLiza argentea) significantly increased after openings, mainly due to small juveniles (<40 mm FL) recruiting to the seagrass beds. In contrast,
these species were caught as larger juveniles (>70 mm FL) in Lake Illawarra. Furthermore, their abundance in Lake Illawarra
declined during successive months, coinciding with declining salinity. Abundances of resident species (such asPseudomugil olorum andAfurcagobius tamarensis) remained largely unchanged after openings. Although it was clear that marine-spawning species must benefit from lagoon openings,
the number and composition of species able to move into lagoons from adjacent waters may be dependent upon the frequency,
duration and time of year that the entrance is connected to the sea. The present study thus provides data which may be useful
for fisheries management in intermittently open lagoons. However, these results should not be cited as reason to artificially
open lagoon entrances as further detailed studies of other aspects of lagoon biota, such as their invertebrate and avian faunas,
are also needed to provide sufficient basis for broader management frameworks. 相似文献
85.
Simon J. Nicol Valerie Allain Graham M. Pilling Jeff Polovina Marta Coll Johann Bell Paul Dalzell Peter Sharples Robert Olson Shane Griffiths Jeffrey M. Dambacher Jock Young Antony Lewis John Hampton Jesus Jurado Molina Simon Hoyle Karine Briand Nic Bax Patrick Lehodey Peter Williams 《Climatic change》2013,119(1):131-145
Climate change presents an emerging challenge to the sustainable management of tuna fisheries, and robust information is essential to ensure future sustainability. Climate and harvest affect tuna stocks, populations of non-target, dependent species and the ecosystem. To provide relevant advice we need an improved understanding of oceanic ecosystems and better data to parameterise the models that forecast the impacts of climate change. Currently ocean-wide data collection in the Pacific Ocean is primarily restricted to oceanographic data. However, the fisheries observer programs that operate in the region offer an opportunity to collect the additional information on the mid and upper trophic levels of the ecosystem that is necessary to complement this physical data, including time-series of distribution, abundance, size, composition and biological information on target and non-target species and mid trophic level organisms. These observer programs are in their infancy, with limited temporal and spatial distribution but recent international and national policy decisions have been made to expand their coverage. We identify a number of actions to initiate this monitoring including: consolidating collaborations to ensure the use of best quality data; developing consistency between sub-regional observer programmes to ensure that they meet the objectives of ecosystem monitoring; interrogating of existing time series to determine the most appropriate spatial template for monitoring; and exploring existing ecosystem models to identify suitable indicators of ecosystem status and change. The information obtained should improve capacity to develop fisheries management policies that are resilient and can be adapted to climate change. 相似文献
86.
Je-Hun Jang Ryan Mathur Laura J. Liermann Shane Ruebush Susan L. Brantley 《Chemical Geology》2008,250(1-4):40-48
We measured the Fe isotope fractionation during the reactions of Fe(II) with goethite in the presence and absence of a strong Fe(III) chelator (desferrioxamine mesylate, DFAM). All experiments were completed in an O2-free glove box. The concentrations of aqueous Fe(II) ([Fe(II)aq]) decreased below the initial total dissolved Fe concentrations ([Fe(II)total], 2.15 mM) due to fast adsorption within 0.2 day. The concentration of adsorbed Fe(II) ([Fe(II)ads]) was determined as the difference between [Fe(II)aq] and the concentration of extracted Fe(II) in 0.5 M HCl ([Fe(II)extr]) (i.e., [Fe(II)ads] = [Fe(II)extr] − [Fe(II)aq]). [Fe(II)ads] also decreased with time in experiments with and without DFAM, documenting that fast adsorption was accompanied by a second, slower reaction. Interestingly, [Fe(II)extr] was always smaller than [Fe(II)total], indicating that some Fe(II) was sequestered into a pool that is not HCl-extractable. The difference was attributed to Fe(II) incorporated into goethite structure (i.e., [Fe(II)inc] = [Fe(II)total] −[Fe(II)extr]). More Fe(II) was incorporated in the presence of DFAM than in its absence at all time steps. Regardless of the presence of DFAM, both aqueous and extracted Fe(II) (δ56/54Fe(II)aq and δ56/54Fe(II)extr) became isotopically lighter than or similar to goethite (− 0.27‰) at day 7, implying that the isotope exchange occurred between bulk goethite and aqueous Fe. Consistently, the mass balance indicated that the incorporated Fe is isotopically heavier than extracted Fe. These observations suggested that (i) co-adsorption of Fe(II) with DFAM resulted in more pervasive electron transfer, (ii) the electron transfer from heavy Fe(II) in the adsorbed Fe(II) to light Fe(III) in goethite results in the fixation of heavy adsorbed Fe(III) on the surface and accumulation of Fe(II) within the goethite, and (iii) desorption of the reduced, light Fe from goethite does not necessarily occur at the same surface sites where adsorption occurred. 相似文献
87.
A laboratory experiment with two sequenced columns was performed as a preliminary study for the installation of a permeable
reactive barrier (PRB) at a site where a mixed ground water contamination exists. The first column contained granular zero
valent iron (ZVI), the second column was filled with granular activated carbon (GAC). Trichloromethane (TCM, 930 μg/l) and
chlorobenzene (MCB, 260 μg/l) were added to the ground water from the site as the main contaminants. Smaller amounts (<60 μg/l)
of benzene, 1,2-dichloroethane, 1,1,2-trichloroethane (1,1,2-TCA), 1,1-dichloroethene (1,1-DCE), trichloroethene (TCE), tetrachloroethene
(PCE), 1,2-dichloropropane (1,2-DCP), bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM), vinyl
chloride and chromate were also added to the water to simulate the complex contamination pattern at the site of interest.
PCE, TCE, 1,1-DCE, DBCM, BDCM, TBM, MCB and chromate were remediated in contact with ZVI, while the remaining contaminants
showed incomplete degradation. A fraction of 8–16.5% TCM was converted to dichloromethane (DCM). Remaining contaminant concentrations
were efficiently sorbed by the GAC until breakthrough of DCM was observed after 1,230 exchanged pore volumes in the GAC. The
results show that the complex mixture of contaminants can be remediated by a sequenced PRB consisting of ZVI and GAC and that
DCM sorption capacity is the critical parameter for the dimensions of the GAC reactor. 相似文献
88.
89.
H. Ebert 《International Journal of Earth Sciences》1936,27(1):74-75
Ohne Zusammenfassung 相似文献
90.
Millennial timescale resolution of rhyolite magma recharge at Tarawera volcano: insights from quartz chemistry and melt inclusions 总被引:4,自引:4,他引:0
Phil Shane Victoria C. Smith Ian Nairn 《Contributions to Mineralogy and Petrology》2008,156(3):397-411
Most rhyolite eruption episodes of Tarawera volcano have emitted several physiochemically distinct magma batches (∼1–10 km3). These episodes were separated on a millennial timescale. The magma batches were relatively homogeneous in temperature and
composition at pumice scale (>4 cm), but experienced isolated crystallisation histories. At the sub-cm scale, matrix glasses
have trace element compositions (Sr, Ba, Rb) that vary by factors up to 2.5, indicating incomplete mixing of separate melts.
Some quartz-hosted melt inclusions are depleted in compatible trace elements (Sr, Ti, Ba) compared to enclosing matrix glasses.
This could reflect re-melting of felsic crystals deeper in the crystal pile. Individual quartz crystals display a variety
of cathodoluminescence brightness and Ti zoning patterns including rapid changes in melt chemistry and/or temperature (∼50–100°C),
and point to multi-cycle crystallisation histories. The Tarawera magma system consisted of a crystal-rich mass containing
waxing and waning melt pockets that were periodically recharged by silicic melts driven by basaltic intrusion.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献