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111.
The significance of zoned Ca-amphibole found in metapelites, quartzites, and synfolial veins of the Internal Zone of the Betic-Rif
range (Federico units from Northern Rif and Alpujárride units from Western Betic) in the Alpine tectono-metamorphic evolution
of these units is discussed for first time. Typical Al-rich metapelites from both areas show assemblages consisting of white
mica and chlorite, with sporadic kyanite and chloritoid. Nevertheless, in the Rif zone, phyllites and synfolial veins of Permo-Triassic
units show the assemblage pumpellyite + epidote + actinolite. In the Jubrique area (Betic zone), Ca-rich phyllites, fine-grained
quartzites, and quartz veins show assemblages consisting of Ca-amphibole, plagioclase, epidote, titanite, chlorite, and quartz.
The Al-in-amphibole thermobarometer defines clockwise pressure–temperature paths with a range of prograde temperatures and
pressures between 272°C-1.2 kbar and 484°C-3.2 kbar for the Federico unit and between 274°C-1.1 kbar and 620°C-6.1 kbar in
the Jubrique unit. Amphiboles from both areas define prograde pressure–temperature paths typical of Barrovian-type metamorphism.
This finding contrasts with previous estimates, which deduced high-pressure conditions in both areas. The described amphiboles
indicate metamorphic conditions similar to those found in the tectonically deepest complex (Veleta complex) of the Betic Internal
Zone and suggest formation during a medium P/T Alpine event, which has not been previously identified in the Alpujárride complex. 相似文献
112.
Eugenio Molina-Navarro Antonio Sastre-Merlín Rosa Vicente Silvia Martínez-Pérez 《Hydrogeology Journal》2014,22(5):1115-1129
A small calcareous basin in central Spain was studied to establish the role of groundwater in the Pareja Limno-reservoir. Limno-reservoirs aim to preserve a constant water level in the riverine zone of large reservoirs to mitigate the impacts arising from their construction. Groundwater flow contribution (mean 60 %) was derived by recharge estimation. In situ measurements (spring discharge, electrical conductivity and sulfate) were undertaken and spring discharge was compared with a drought index. Twenty-eight springs were monitored and three hydrogeological units (HGUs) were defined: a carbonate plateau (HGU1), the underlying aquitard (HGU2), and the gypsum-enriched HGU3. HGU1 is the main aquifer and may play a role in the preservation of the limno-reservoir water level. Hydrogeochemical sampling was conducted and the code PHREEQC used to describe the main geochemical processes. Weathering and dissolution of calcite and gypsum seem to control the hydrogeochemical processes in the basin. Water progresses from Ca2+–HCO3 – in the upper basin to Ca2+–SO4 2– in the lower basin, where HGU3 outcrops. A clear temporal pattern was observed in the limno-reservoir, with salinity decreasing in winter and increasing in summer. This variation was wider at the river outlet, but the mixing of the river discharge with limno-reservoir water buffered it. 相似文献
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119.
R. Orús M. Hernndez-Pajares J. M. Juan J. Sanz M. García-Fernndez 《Journal of Atmospheric and Solar》2002,64(18)
The existence of a worldwide international GPS service (IGS) permanent network of dual-frequency receivers makes the computation of global ionospheric maps (GIMs) of total electron content (TEC) feasible. The GIMs computed by the IGS Associate Analysis Centers on a daily basis and by other kinds of forecast GIMs, which can be computed from, for instance, the international reference ionosphere (IRI) model, and the GPS broadcast models in the navigation message, can be applied to a broad diversity of fields, for instance as, navigation and time transfer.In this context, the performance of different kinds of models are presented in order to determine the accuracy of the different GIM. This is carried out by comparison with the TOPEX data that provides an independent and precise (at the level of few TECU) vertical TEC determination over the oceans and seas. Thus, the obtained accuracies, in terms of global relative error, ranging from 54% corresponding to the GPS broadcast model, to about 41% corresponding to IRI climatological model, and to less than 30% corresponding to GPS data driven models. 相似文献
120.
Carmelo Ferlito Marco Viccaro Eugenio Nicotra Renato Cristofolini 《Bulletin of Volcanology》2010,72(10):1179-1190
Over the last 2 years, the south east crater (SEC) at Mt. Etna (Italy) has been characterised by the intermittent emission
of lava flows, often accompanied by paroxysmal episodes with violent strombolian activity and/or lava fountains. One of the
most intense and intriguing episodes occurred on November 16, 2006 during strombolian and effusive activity from the very
top of the SEC. At the eastern base of the crater, a violent and short-lasting outburst generated a 300-m-high eruptive curtain
of finely fragmented magma and steam, which collapsed in a few seconds giving rise to a small but significant pyroclastic
flow. The paroxysm was preceded by progressive sliding of the eastern flank of the SEC edifice, which led to the formation
of a large niche. Previously published models explain the outburst as due to rapid vaporisation of water contained in sediments
on contact with hot lava flowing along the flank of the SEC or, alternatively, to gravitational collapse of a destabilised
portion of the eastern flank of the crater. However, several lines of evidence suggest that these models do not adequately
explain the paroxysm, which we propose was associated with the explosive emission of magma during the rapid opening of an
ESE-WNW-oriented fracture at the eastern base of the SEC. Moreover, geochemical data of the products associated with this
episode show that they are the most primitive and gas-rich among those erupted during the entire 2006 period. We suggest that
the paroxysm of November 16, 2006, which occurred at base of the SEC, was a magma outburst due to rapid ground fracturing
related to a drop in confining pressure upon the underlying dyke consequent to the sliding of the eastern flank of the SEC
cone. Specifically, the unloaded shallow portion of the feeding dyke did not restrain the arrival of a new batch of gas-rich
magma, which worked its way out by fracturing the base of the niche at its weakest point. This paroxysm appears significant
because it reveals the potential development of syn-eruptive dynamics acting directly on the uppermost portion of the plumbing
system which is able to generate pyroclastic flows even on basaltic volcanoes such as Mount Etna. 相似文献