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71.
Ana Lorena Esteban‐García Raquel Lebrero Manuel Alejandro de los Santos Raúl Muñoz Juan Ignacio Tejero 《洁净——土壤、空气、水》2013,41(5):469-472
A study was performed in two submerged, pilot‐scale biofilm bioreactors operated under different conditions to determine the relationship between the operating parameters and H2S emission. H2S was always detected in the exhaust air at concentrations varying from 1 to 353 ppmv. The specific aeration rate was the most influencing parameter, with As < 30 kg COD (dissolved oxygen concentrations <4 mg L?1) increasing noticeably the H2S production. The periodical removal of the accumulated sludge reduced H2S emissions by ~14%. 相似文献
72.
Ignacio?Torresi Roberto?Perez?XavierEmail author Diego?F.?A.?Bortholoto Lena?V.?S.?Monteiro 《Mineralium Deposita》2012,47(3):299-323
The Alvo 118 iron oxide–copper–gold (IOCG) deposit (170 Mt at 1.0 wt.% Cu, 0.3 g/t Au) lies in the southern sector of the
Itacaúnas Shear Belt, Carajás Mineral Province, along a WNW–ESE-striking, 60-km-long shear zone, close to the contact of the
~2.76-Ga metavolcano-sedimentary Itacaiúnas Supergroup and the basement (~3.0 Ga Xingu Complex). The Alvo 118 deposit is hosted
by mafic and felsic metavolcanic rocks and crosscutting granitoid and gabbro intrusions that have been subjected to the following
hydrothermal alteration sequence towards the ore zones: (1) poorly developed sodic alteration (albite and scapolite); (2)
potassic alteration (biotite or K-feldspar) accompanied by magnetite formation and silicification; (3) widespread, pervasive
chlorite alteration spatially associated with quartz–carbonate–sulphide infill ore breccia and vein stockworks; and (4) local
post-ore quartz–sericite alteration. The ore assemblage is dominated by chalcopyrite (~60%), bornite (~10%), hematite (~20%),
magnetite (10%) and subordinate chalcocite, native gold, Au–Ag tellurides, galena, cassiterite, F-rich apatite, xenotime,
monazite, britholite-(Y) and a gadolinite-group mineral. Fluid inclusion studies in quartz point to a fluid regime composed
of two distinct fluid types that may have probably coexisted within the timeframe of the Cu–Au mineralizing episode: a hot
(>200°C) saline (32.8‰ to 40.6 wt.% NaCl eq.) solution, represented by salt-bearing aqueous inclusions, and a lower temperature
(<200°C), low to intermediate salinity (<15 wt.% NaCl eq.) aqueous fluid defined by two-phase (LH2O + VH2O) fluid inclusions. This trend is very similar to those defined for other IOCG systems of the Carajás Mineral Province. δ
18OH2O values in equilibrium with calcite (−1.0‰ to 7.5‰ at 277°C to 344°C) overlap the lower range for primary magmatic waters,
but the more 18O-depleted values also point to the involvement of externally derived fluids, possibly of meteoric origin. Furthermore, sulphide
δ
34S values (5.1‰ to 6.3‰), together with available boron isotope and Cl/Br–Na/Cl data provide evidence for a significant component
of residual evaporative fluids (e.g., bittern fluids generated by seawater evaporation) in this scenario that, together with
magma-derived brines, would be the main sources of the highly saline fluids involved in the formation Alvo 118 IOCG deposit.
The restricted high temperature sodic alteration, the pervasive overprinting of the potassic alteration minerals by chlorite
proximal to the ore zones, ore breccias with open-space filling textures in brittle structures, microthermometric and stable
isotope data indicate, collectively, that the Alvo 118 IOCG system developed at structurally high levels and may be considered
the shallower representative of the IOCG systems of the CMP. 相似文献
73.
We present detailed pollen and charcoal records from Lago Pichilafquén (~ 41°S) to decipher the effects of climate change and varying disturbance regimes on the composition and structure of the vegetation on the Andean foothills of northwestern Patagonia during the last 2600 yr. Here, temperate rainforests have dominated the landscape since 2600 cal yr BP with variations ranging from cool-temperate and wet north Patagonian rainforests to relatively warm and summer-drought-resistant Valdivian rainforests. We interpret relatively warm/dry conditions between 1900–2600, 690–750 and 320–430 cal yr BP, alternating with cold/wet conditions between 1500–1900, 750–1100 and 430–690 cal yr BP. Rapid deforestation and spread of plants introduced by Europeans occurred at 320 and 140 cal yr BP. The record includes five tephras with ages of 2130, 1460, 1310, 1210, and 340 cal yr BP, all of which precede local fire events and increases in trees favored by disturbance by less than 100 yr. We conclude that centennial-scale changes in the southern westerlies were the primary driver of vegetation shifts in northwestern Patagonia over the last 2600 yr. Within this interval, local disturbance regimes altered the structure, composition, and dynamics of the lowland rainforest vegetation during several discrete, short-lived episodes. 相似文献
74.
75.
Ignacio Vidal 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(3):571-582
With the objective of modelling annual rainfall maximum intensities in different geographical zones of Chile, we have created a Bayesian inference method for the generalized extreme value type I distribution (Gumbel distribution). We considered an uninformative prior distribution for the location parameter, μ, and three different prior distributions for the scale parameter, σ. Under these conditions we obtained the posterior distribution of (μ, σ) and associated summary statistics such as modes, expected values, quantiles and credibility intervals. In order to predict and estimate return periods, we obtained the posterior distribution of future observations, its expected value, quantiles and credibility intervals. To obtain several of these posterior summary measures it was necessary to utilize both numerical and Laplace approximations. Furthermore we estimate return period curves and intensity–duration–frequency curves. 相似文献
76.
J. Germán Rodríguez Oihana Solaun María Jesús Belzunce Segarra J. Ignacio García Alonso Victoriano Valencia 《Marine pollution bulletin》2010,60(1):139-642
Tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) were measured in surficial sediments at, the ports of Pasaia and Bilbao, together with other mid- and small-size harbours of the Basque Country (northern Spain), in 2007-2008. The highest values of the sum of the three measured butyltin species (3523-3640 ng g−1, as Sn) were found at sampling stations near to shipyards located within the port of Pasaia. The highest value of TBT concentration (3143 ng g−1, as Sn) was found at the marina of Getxo, in the port of Bilbao. The degree of TBT degradation varied greatly between sampling stations, being found to be generally higher in those sediments with higher values of redox potential and lower values of TBT concentration (normalized by organic matter content). 相似文献
77.
Nils Lenhardt Harald Böhnel Klaus Wemmer Ignacio S. Torres-Alvarado Jens Hornung Matthias Hinderer 《Bulletin of Volcanology》2010,72(7):817-832
The volcaniclastic Tepoztlán Formation (TF) represents an important rock record to unravel the early evolution of the Transmexican
Volcanic Belt (TMVB). Here, a depositional model together with a chronostratigraphy of this Formation is presented, based
on detailed field observations together with new geochronological, paleomagnetic, and petrological data. The TF consists predominantly
of deposits from pyroclastic density currents and extensive epiclastic products such as tuffaceous sandstones, conglomerates
and breccias, originating from fluvial and mass flow processes, respectively. Within these sediments fall deposits and lavas
are sparsely intercalated. The clastic material is almost exclusively of volcanic origin, ranging in composition from andesite
to rhyolite. Thick gravity-driven deposits and large-scale alluvial fan environments document the buildup of steep volcanic
edifices. K-Ar and Ar-Ar dates, in addition to eight magnetostratigraphic sections and lithological correlations served to
construct a chronostratigraphy for the entire Tepoztlán Formation. Correlation of the 577 m composite magnetostratigraphic
section with the Cande and Kent (1995) Geomagnetic Polarity Time Scale (GPTS) suggests that this section represents the time
intervall 22.8–18.8 Ma (6Bn.1n-5Er; Aquitanian-Burdigalian, Lower Miocene). This correlation implies a deposition of the TF
predating the extensive effusive activity in the TMVB at 12 Ma and is therefore interpreted to represent its initial phase
with predominantly explosive activity. Additionally, three subdivisions of the TF were established, according to the dominant
mode of deposition: (1) the fluvial dominated Malinalco Member (22.8–22.2 Ma), (2) the volcanic dominated San Andrés Member
(22.2–21.3 Ma) and (3) the mass flow dominated Tepozteco Member (21.3–18.8 Ma). 相似文献
78.
79.
80.
Rosen G Rivera-Duarte I Chadwick DB Ryan A Santore RC Paquin PR 《Marine environmental research》2008,66(3):327-336
Critical tissue copper (Cu) residues associated with adverse effects on embryo-larval development were determined for the Mediterranean mussel (Mytilus galloprovincialis) and purple sea urchin (Strongylocentrotus purpuratus) following laboratory exposure to Cu-spiked seawater collected from San Diego Bay, California, USA. Whole body no-observed-effect-residues (NOER) were similar, with means of 21 and 23mugg(-1)dw, for M. galloprovincialis and S. purpuratus, respectively. Mean whole body median effect residues (ER50) were 49 and 142mugg(-1)dw for M. galloprovincialis and S. purpuratus, respectively. The difference in ER50s between species was reduced to a factor of <2 when expressed as soft tissue residues. Coefficients of variation among whole body-ER50s were 3-fold lower than median waterborne effect concentrations (EC50) for both species exposed to samples varying in water quality characteristics. This suggests that tissue concentrations were a better predictor of toxicity than water concentrations. The CBRs described herein do not differentiate between the internal Cu concentrations that are metabolically available and those that are accumulated and then detoxified. They do appear, however, to be well enough related to the level of accumulation at the site of action of toxicity that they serve as useful surrogates for the copper concentration that affects embryonic development of the species tested. Results presented have potentially important implications for a variety of monitoring and assessment strategies. These include regulatory approaches for deriving saltwater ambient water quality criteria for Cu, contributions towards the development of a saltwater biotic ligand model, the conceptual approach of using CBRs, and ecological risk assessment. 相似文献