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491.
Electromigration is proposed as an in situ method for preconcentrating contaminants in ground water prior to pumping and treating. In earlier investigations by the senior author and co-workers, it was found that Cu in synthetic ground water migrated strongly to a Pt cathode and plated out as metallic copper. In the present study, carbon electrodes were inserted into a laboratory column of fine quartz sand that was saturated with a lower concentration of CuSO4 solution. A fixed potential of 2.5 V was applied, causing dissolved Cu and SO4 to accumulate strongly at the cathode and anode, respectively. Only minor plating-out of Cu took place on the carbon electrodes. In addition to the use of carbon electrodes, the present research also investigated the effects of a lower concentration of metal, accumulation of SO4 adjacent to the anodes, adsorption of Cu on the sand, and competition by moving ground water.
At an imposed voltage of 2.5 V and in the presence of 65 mg/L of dissolved Cu and 96 mg/L of SO4 (0.001 M CuSO4 solution), electrolysis of water caused large changes in the pH and speciation of the aqueous components, as well as precipitation of solid Cu-hydroxides. Significant retardation of Cu occurred in the presence of ground water flowing at an average intergranular velocity of 0.2 m/day, but only minor retardation at water velocities of 1.9 and 2.9 m/day.
Sulfate tends to migrate strongly to the anodes, suggesting that in situ electromigration may offer a useful new method for preconcentrating such highly soluble ions as SO4 , NO3 , and CI that are difficult to remove by conventional pump-and-treat methods. A number of potential problems exist that should be addressed in a field test. 相似文献
At an imposed voltage of 2.5 V and in the presence of 65 mg/L of dissolved Cu and 96 mg/L of SO
Sulfate tends to migrate strongly to the anodes, suggesting that in situ electromigration may offer a useful new method for preconcentrating such highly soluble ions as SO
492.
493.
494.
Catherine Quiblier Gilles Bourdier Christian Amblard Denise Pepin 《Aquatic Sciences - Research Across Boundaries》1994,56(1):29-39
Phyto-zooplankton trophic relationships were studied using phytoplanktonic pigments (chlorophylls and carotenoids) as organic natural markers. Pigments were separated by high-pressure liquid chromatography (HPLC).Comparison of pigment profiles from monospecific cultures of various taxonomic groups (Chlorophyceae, Bacillariophyceae and Cyanobacteria) and from Cladocera crustaceans (Daphnia magna) fed with these cultures, showed that the characteristic pigment associations of the different taxa are conserved during their transfer from primary producers to secondary consumers.Chromatographic profiles of the Bacillariophyceae and Chlorophyceae type were obtained fromDaphnia respectively fed with mixtures of a Chlorophyceae and a diatom species and mixture of a Chlorophyceae and a Cyanobacterium. This showed the importance of this method in demonstrating a possible selective feeding by the herbivorous zooplankton.The observation of pigment profiles of the Dinophyceae type following feeding of a zooplankton assemblage from Lake Pavin within this natural medium (phytoplankton dominated by a Dinophyceae) and of a Chlorophyceae type profile as the same assemblage was fed in the laboratory on phytoplankton from Lake Villerest (composed of about 80% Cyanobacteria and 20% Chlorophyceae), suggested that this method could be applied to the natural environment. 相似文献
495.
Pascal Umekwe Joanna Mongrain Mohabbat Ahmadi Catherine Hanks 《Natural Resources Research》2013,22(1):45-58
The capacity of 21 major fields containing more than 95% of the North Slope of Alaska’s oil were investigated for CO2 storage by injecting CO2 as an enhanced oil recovery (EOR) agent. These fields meet the criteria for the application of miscible and immiscible CO2-EOR methods and contain about 40 billion barrels of oil after primary and secondary recovery. Volumetric calculations from this study indicate that these fields have a static storage capacity of 3 billion metric tons of CO2, assuming 100% oil recovery, re-pressurizing the fields to pre-fracturing pressure and applying a 50% capacity reduction to compensate for heterogeneity and for water invasion from the underlying aquifer. A ranking produced from this study, mainly controlled by field size and fracture gradient, identifies Prudhoe, Kuparuk, and West Sak as possessing the largest storage capacities under a 20% safety factor on pressures applied during storage to avoid over-pressurization, fracturing, and gas leakage. Simulation studies were conducted using CO2 Prophet to determine the amount of oil technically recoverable and CO2 gas storage possible during this process. Fields were categorized as miscible, partially miscible, and immiscible based on the miscibility of CO2 with their oil. Seven sample fields were selected across these categories for simulation studies comparing pure CO2 and water-alternating-gas injection. Results showed that the top two fields in each category for recovery and CO2 storage were Alpine and Point McIntyre (miscible), Prudhoe and Kuparuk (partially miscible), and West Sak and Lisburne (immiscible). The study concludes that 5 billion metric tons of CO2 can be stored while recovering 14.2 billion barrels of the remaining oil. 相似文献
496.
Francesca Bacciotti Leonardo Testi Alessandro Marconi Paulo J.V. Garcia Thomas P. Ray Jochen Eislöffel Catherine Dougados 《Astrophysics and Space Science》2003,286(1-2):157-162
The interplay between accretion and ejection in the environment of young stellar objects (YSOs) is believed to be a crucial
element in the star formation process. Since most of the properties of the models are set up in the first few AUs from the
source (below the so-called Alfvèn surface), to validate and constrain the models observationally we need very high angular
resolution. With HST (resolution ∼ 0.'1, i.e. about 14 AU in Taurus)we have been able to access the external border of the
acceleration region, for jets in the Taurus-Auriga cloud. Here we see an onion-like kinematic structure in the first 200 AU
of the flow, and indications for rotation around the symmetry axis for the resolved low/moderate velocity component. We have
now planned observations with AMBER on the VLTI to investigate at 1 mas resolution (in J) the core of the central engine,
down to 0.1 AU from the source. Here we describe a joint project by several Institutes in the AMBER consortium dedicated to
the study of the morphology and detailed kinematics of a few selected targets. On one hand we will use the large UV coverage
of the ATs to explore at medium spectral resolution the structure of the flow. On the other hand the large collection area
of the UTs combined with the high resolution mode (R=10000) of AMBER will allow us to search for interesting kinematic features,
among which signatures of rotation around the axis, that would constitute an important validation of the proposed models for
the jet launching.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
497.
Catherine Grimaldi Michel Grimaldi Antoine Millet Thierry Bariac Jacques Boulgue 《水文研究》2004,18(1):93-106
The aim of this study is to identify, in a small catchment area located within a tropical forest, the pedological compartments in which the export of nutrients and chemical erosion of solutes occur during a stormflow event. The catchment area displays two types of lateral flow: (i) overland flow at the surface of the soil in the litter and root mat and (ii) groundwater flow in a macroporous subsurface horizon. We interpret the variations of stream‐water chemistry during a storm‐flow event using the separation of storm‐flow hydrograph data between overland and groundwater flow, and (Cl?) as a chemical parameter characterizing the residence time of water in the soil. It appears that K+ especially was released into the throughfall, whereas Ca++, Mg++ and Na+ were clearly released from the litter. K+ disappeared rapidly from soil solution, whereas Ca++ and Mg++ were more progressively absorbed by the vegetation. The Ca++ and Mg++ contents in groundwater increased with increasing residence time owing to the transpiration of trees. The export of H4SiO4 in the overland flow was moderate, i.e. 24% of total H4SiO4 export in the stream flow, as overland flow represented 39% of total runoff. The subsurface horizon—where active groundwater flow occurs—was successively affected by chemical erosion during the storm‐flow peak, and then by neoformation of kaolinite favoured by increasing water residence time. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
498.
Luis López-Martín Sylvie Cabrit Catherine Dougados 《Astrophysics and Space Science》2004,292(1-4):531-537
We present adaptive optics spectro-imaging observations of the RW Aur jet in optical forbidden lines, at an angular resolution of 0.4″. Comparison with HST data taken 2 yr later shows that proper motions in the blueshifted and redshifted lobes are in the same ratio as their radial velocities, a direct proof that the velocity asymmetry in this jet is real and not an emissivity effect. The inferred jet inclination to the line of sight is i = 46±3°. The inner knot spacing appears best explained by time variability with at least two modes: one irregular and asymmetric (possibly random) on timescales of ≤3–10 yr, and another more regular with ?20 yr period. We also report indirect evidence for correlated velocity and excitation gradients in the redshifted lobe, possibly related to the blue/red velocity and brightness asymmetry in this system. 相似文献
499.
Catherine Heymans Michael L. Brown Marco Barden John A. R. Caldwell Knud Jahnke Chien Y. Peng Hans-Walter Rix y Taylor Steven V. W. Beckwith Eric F. Bell rea Borch Boris Häußler Shardha Jogee Daniel H. McIntosh Klaus Meisenheimer Sebastian F. Sánchez Rachel Somerville Lutz Wisotzki Christian Wolf 《Monthly notices of the Royal Astronomical Society》2005,361(1):160-176
500.
Abstract— The carbonate mineralogy of several complex carbonate‐rich regions in Allan Hills (ALH) 84001 has been examined. These regions contain familiar forms of carbonate, as well as textural forms previously unreported including carbonate rosettes, planiform “slab” carbonates, distinct “post‐slab” magnesites, and carbonates interstitial to feldspathic glass and orthopyroxene. Slab carbonates reveal portions of the carbonate growth sequence not seen in the rosettes and suggest that initial nucleating compositions were calcite‐rich. The kinetically controlled growth of rosettes and slab carbonates was followed by an alteration event that formed the magnesite‐siderite layers on the exterior surfaces of the carbonate. Post‐slab magnesite, intimately associated with silica glass, is compositionally similar to the magnesite in these exterior layers but represents a later generation of carbonate growth. Feldspathic glasses had little or no thermal effect on carbonates, as indicated by the lack of thermal decomposition or any compositional changes associated with glass/carbonate contacts. 相似文献