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51.
Fluorite solubility equilibria in selected geothermal waters 总被引:2,自引:0,他引:2
Calculation of chemical equilibria in 351 hot springs and surface waters from selected geothermal areas in the western United States indicate that the solubility of the mineral fluorite, CaF2, provides an equilibrium control on dissolved fluoride activity. Waters that are undersaturated have undergone dilution by non-thermal waters as shown by decreased conductivity and temperature values, and only 2% of the samples are supersaturated by more than the expected error. Calculations also demonstrate that simultaneous chemical equilibria between the thermal waters and calcite as well as fluorite minerals exist under a variety of conditions.Testing for fluorite solubility required a critical review of the thermodynamic data for fluorite. By applying multiple regression of a mathematical model to selected published data we have obtained revised estimates of the pK (10,96), ΔGof (?280.08 kcal/mole), ΔHof (?292.59 kcal/mole), S° (16.39 cal/deg/mole) and CoP (16.16 cal/deg/mole) for CaF2 at 25°C and 1 atm. Association constants and reaction enthalpies for fluoride complexes with boron, calcium and iron are included in this review. The excellent agreement between the computer-based activity products and the revised pK suggests that the chemistry of geothermal waters may also be a guide to evaluating mineral solubility data where major discrepancies are evident. 相似文献
52.
Tracking particle-associated processes in nearshore environments by use of 234Th/238U disequilibrium
Robert C. Aller Larry K. Benninger J. Kirk Cochran 《Earth and Planetary Science Letters》1980,47(2):161-175
Measurement of excess 234Th (t1/2 = 24.1 days) in surface sediment from 12 stations throughout Long Island Sound, U.S.A., demonstrates: (1) a mean (summer) sediment inventory of 3.6 dpm/cm2 consistent with complete, nearly instantaneous removal of 234Th from the overlying water and capture within the estuary, and (2) preferential association of excess 234Th with small particles and inventory build-ups in muddy bottom areas. There may also be a tendency for higher inventories in areas of high physical or biogenic reworking of surface sediments. A range of particle reworking rates (0–5 cm) from <0.01 × 10?6 to 1.6 × 10?6 cm2/s is found in the Sound with most values ~0.2?0.5 × 10?6 cm2/s. The inventory and reworking patterns demonstrate the high mobility, both horizontal and vertical, of particles in the estuary on 234Th decay time scales and are unequivocal evidence for control of reactive element distribution in the water column by the muddy regions of the basin. 相似文献
53.
54.
Greg?K?Druschel Martin?AA?SchoonenEmail author D?Kirk?Nordstrom James?W?Ball Yong?Xu Corey?A?Cohn 《Geochemical transactions》2003,4(1):12
A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed
in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange
resin Bio-Rad™ AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and
thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with
1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five
pools in Yellowstone National Park between on-site IC analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored
sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern)
and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin
were made using HCl solutions, but were unsuccessful. Bio-Rad™ AG2-X8, an anion-exchange resin with weaker binding sites than
the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been
accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl.
Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly
using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions
using AG2-X8 resin columns. 相似文献
55.
Huan Feng J. Kirk Cochran David J. Hirschberg Robert E. Wilson 《Estuaries and Coasts》1998,21(2):263-280
Multiple sediment cores were collected in June 1994 in the turbidity maximum zone of the Hudson River estuary off Manhattan, New York. Results from X-radiography of the sediments and measurements of natural radionuclides (234Th,7Be, and210Pb) and trace metals (Ag, Cd, Cu, Pb, and Zn) show significant spatial variability of sediment composition and structure and patchy distributions of radionuclides activities and trace metal concentrations in this small area (0.6 km × 0.5 km). Radionuclide and trace metal analyses confirm prior work (Olsen et al. 1978; Olsen et al. 1981; Hirschberg et al. 1996) that show the western margin area of the river acts as a repository of these chemical constituents at least for the short-term period (0.5–1 yr), and the mid-channel area is not a depositional area for sediments and associated chemical constituents.7Be profiles reveal short-term sediment deposition rates ranging from 6 cm yr?1 to 26 cm yr?1 in the western margin area. Significant spatial variations in excess234Th and7Be inventories (up to a factor of 10 and 5 for234Th and7Be, respectively) are found in the western margin depositional area, although the inventories are balanced, on average, with in situ production in water column and atmospheric supply. The spatial variation of surficial excess210Pb and trace metal concentrations in depositional areas of the western margin are ≤10% for Ag, Cu, Pb, and Zn and 29% for Cd. However, the variations in the transition zone range from 28% to 93%. This variability is likely related to variations in tidal current velocity, bottom shear stress, and river channel morphology. 相似文献
56.
Redistribution of sea level rise associated with enhanced greenhouse warming: a simple model study 总被引:1,自引:0,他引:1
Future sea level rise from thermal expansion of the World Ocean due to global warming has been explored in several recent studies using coupled ocean-atmosphere models. These coupled models show that the heat input by the model atmosphere to the ocean in such an event could be quite non-uniform in different areas of the ocean. One of the most significant effects predicted by some of the models is a weakening of the thermohaline circulation, which normally transports heat poleward. Since the greatest heat input from enhanced greenhouse warming is in the higher latitudes, a weakening of the poleward heat transport effectively redistributes the heat anomaly and the associated sea level rise to lower latitudes. In this study, the mechanism of ocean circulation spindown and heat redistribution was studied in the context of a much simpler, linearized shallow water model. Although the model is much simpler than the three-dimensional ocean circulation models used in the coupled model experiments, and neglects several important physical effects, it has a nearly 10-fold increase in horizontal resolution and clearer dynamical interpretations. The results indicated that advanced signals of sea level rise propagated rapidly through the action of Kelvin and Rossby waves, but the full adjustment toward a more uniform sea level rise took place much more slowly. Long time scales were required to redistribute mass through narrow currents trapped along coasts and the equatorial wave guide. For realistic greenhouse warming, the model showed why the sea level rise due to ocean heating could be far from uniform over the globe and hence difficult to estimate from coastal tide gauge stations. 相似文献
57.
Kirk Bryan 《Climate Dynamics》1996,12(8):545-555
Climate change due to enhanced greenhouse warming has been calculated using the coupled GFDL general circulation model of the atmosphere and ocean. The results of the model for a sustained increase of atmospheric carbon dioxide of 1% per year over a century indicate a marked warming of the upper ocean. Results of the model are used to study the rise in sea level caused by increase in ocean temperatures and associated changes in ocean circulation. Neglecting possible contributions due to changes in the volume of polar ice sheets and mountain glaciers, the model predicts an average rise in sea level of approximately 15 ± 5 cm by the time atmospheric carbon dioxide doubles. Heating anomalies are greatest in subpolar latitudes. This effect leads to a weakening of the ocean thermohaline circulation. Changes in thermohaline circulation redistribute heat within the ocean from high latitudes toward the equator, and cause a more uniform sea level rise than would occur otherwise. 相似文献
58.
59.
Kirk A Maasch 《Climate Dynamics》1989,4(1):45-55
The Grassberger-Procaccia method of calculating dimension from a time series is applied to 14 late Pleistocene 18O records. The difficulties encountered when using this algorithm on limited data sets are reviewed and the step-by-step procedure actually used to calculate the dimension of each record is explicitly listed. Although the results must be viewed with caution, they do indicate that the dimension cannot be measured accurately enough to determine whether or not it is fractal. However, in spite of inaccuracies in the time scale, the underlying dynamics do not appear to be random and there is a suggestion that a lower bound to the Grassberger-Procaccia dimension is somewhere between 4 and 6. 相似文献
60.