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351.
Anthropogenic S emissions in the Athabasca oil sands region (AOSR) in Alberta, Canada, affect SO4 deposition in close vicinity of industrial emitters. Between May 2008 and May 2009, SO4-S deposition was monitored using open field bulk collectors at 15 sites and throughfall collectors at 14 sites at distances between 3 and 113 km from one of the major emission stacks in the AOSR. At forested plots >90 km from the operations, SO4 deposition was ∼1.4 kg SO4-S ha−1 yr−1 for bulk deposition and ∼3.3 kg SO4-S ha−1 yr−1 for throughfall deposition. Throughfall SO4 deposition rates in the AOSR exceeded bulk deposition rates at all sites by a factor of 2–3, indicating significant inputs of dry deposition especially under forest canopies. Both bulk and throughfall SO4 deposition rates were elevated within 29 km distance of the industrial operations with deposition rates as high as 11.7 kg SO4-S ha−1 yr−1 for bulk deposition and 39.2 kg SO4-S ha−1 yr−1 for throughfall at industrial sites. Sulfur isotope ratio measurements of atmospheric SO4 deposited in the AOSR revealed that at a few selected locations 34S-depleted SO4, likely derived from H2S emissions from tailing ponds contributes to local atmospheric SO4 deposition. In general, however, δ34S values of SO4 deposition at distant forested plots (>74 km) with low deposition rates were not isotopically different from δ34S values at sites with high deposition rates in the AOSR and are, therefore, not suitable to determine industrial S contributions. However, O isotope ratios of atmospheric SO4 in bulk and throughfall deposition in the AOSR showed a distinct trend of decreasing δ18O-SO4 values with increasing SO4 deposition rates allowing quantification of industrial contributions to atmospheric SO4 deposition. Two-end-member mixing calculations revealed that open field bulk SO4 deposition especially at industrial sites in close proximity (<29 km) to the operations is significantly (17–59%) affected by industrial S emissions and that throughfall generally contained 49–100% SO4 of industrial origin. Hence, it is suggested that δ18O values of SO4 may constitute a suitable tracer for quantifying industrial contributions to atmospheric SO4 deposition in the AOSR. 相似文献
352.
Choon-Ki Lee Shin-Chan Han Bernhard Steinberger 《Physics of the Earth and Planetary Interiors》2011,184(1-2):51-62
The radial viscosity structure of the Earth is explored on the basis of the geoid observations. The variations of uncertainty in seismic tomography models are accounted for when finding the radial viscosity structure. The new methodology we propose attempts to fit more closely those features of the geoid that are better constrained by tomography models and avoids to fit those features that are poorly constrained. This approach is particularly important because the error of geoid predictions caused by uncertainties in seismic tomography models is overwhelmingly larger than the noise in the geoid measurements. The synthetic tests indicate that the viscosity structures obtained by disregarding the uncertainty variations in seismic tomography models can be biased depending on the geoid spectral band and on the ‘input’ seismic tomography model. When the uncertainty variations in seismic models are considered in the inversion process, results do not indicate a viscosity in the transition zone lower than in the upper mantle. A robust feature found with the new method is a viscosity in the upper mantle two orders of magnitude smaller than in the lower mantle. The error covariance of seismic tomography models is critical for the method we suggest. A covariance matrix rigorously derived by seismologists should help to even more reliably infer the viscosity structure and relation between anomalies in density and seismic velocities from surface observations such as the geoid, and thus lead to a better knowledge of the Earth interior. 相似文献
353.
Ulrike Exner Neil S. Mancktelow Bernhard Grasemann 《Journal of Structural Geology》2004,26(12):2191-2201
Flanking structures are deflections of planar or linear fabric elements in a rock alongside a crosscutting element (CE), e.g. a vein or fault. This study provides new results from analogue experiments, which test and extend recent numerical models of flanking structures. A linear viscous matrix material (PDMS) was deformed in a ring shear rig that allows continuous observation to large values of shear strain. Rotational behaviour, offset and deflection of marker lines around a predefined, lubricated CE were monitored for different initial orientations of the fault with respect to the shear zone boundary, and the results were compared with numerical results and natural examples. At high initial angles to the shear zone boundary (>135°), a structure previously described as an ‘s-type flanking fold’ develops. During progressive deformation, an initially straight marker line passing through the centre of the CE is offset in a sense synthetic with the bulk sense of shear and shows a shortening displacement across the CE. Simultaneously, this central marker line is deflected and forms symmetrical folds, which are convex in the direction of shear along the CE (i.e. normal drag). Both offset and deflection of the marker lines decrease towards the tips of the fault. Natural examples of s-type flanking folds, directly comparable with the model results, are more common than is generally appreciated. 相似文献
354.
355.
An increasing number of occurrences of margarite have been reported in the last years. However, previous experimental investigations in the system CaO-Al2O3-SiO2-H2O are limited to the synthesis of margarite and to the upper stability limit according to the reaction (1) 1 margarite?1 anorthite +1 corundum +1 H2O (Chatterjee, 1971; Velde, 1971). Since margarite often occurs together with quartz, the upper stability limit of margarite in the presence of quartz is of special interest. Therefore, the reactions (5) 1 margarite +1 quartz ?1anorthite +1 kyanite/andalusite +1 H2O and (6) 4 margarite+3 quartz ? 2 zoisite+5 kyanite+3 H2O were investigated experimentally using mixtures of natural margarite (from Chester, Mass., USA), quartz, kyanite, andalusite, zoisite, and synthetic anorthite. The indicated equilibrium temperatures at water pressures equal to total pressure are: 515± 25°C at 4 kb, 545 ±15°C at 5 kb, 590±10°C at 7 kb, and 650±10°C at 9 kb for reaction (5), and 651±11°C at 10 kb, 648 ± 8°C at 12.5kb, and 643±13°C at 15kb for reaction (6), respectively. Besides this, additional brackets for equilibrium temperatures were determined for the above cited reaction (1): 520±10°C at 3 kb, 580±10°C at 5 kb, and 640± 20°C at 7 kb. On the basis of these experimentally determined reactions (1), (5), and (6) and of the reactions (3) 2 zoisite +1 kyanite? 4 anorthite +1 corundum +1 H2O (7) 2 zoisite +1 kyanite +1 quartz ? 4 anorthite +1 H2O and (10) 1 pyrophyllite ? 1 andalusite/kyanite+3 quartz+1 H2O for which experimental or, in the case of reaction (3), calculated data were already available, a pressure-temperature diagram with 3 invariant points and 11 univariant reactions was developed using the method of Schreinemakers. This diagram, summarizing both experimental and phase relation studies, allows conclusions about the conditions under which margarite has been formed in nature. Margarite is limited to low grade metamorphism at water pressures up to approximately 3.5 kb; in the presence of quartz, margarite is even limited to low grade metamorphism at water pressures up to 5.5 kb. Only at water pressures higher than the values stated before margarite, and margarite+quartz, respectively, can occur in medium grade metamorphism (as defined by Winkler, 1970 and 1973). For the combined occurrence of margarite+quartz and staurolite as reported by Harder (1956) and Frey (personal communication, 1973) it may be estimated that water pressure has been greater than approximately 5.5 kb, wheras temperature has been in the range from 550 to 650°C. Furthermore, the present study shows that the assemblage zoisite+kyanite (+ H2O) is an indicator of both pressure [P H 2 O> approximately 9kb]and temperature [T> approximately 640 to 650° Cat water Pressures up to 15 kb]. 相似文献
356.
Around the globe underground hard coal mining leads to a release of methane into the atmosphere. About 7% of the global annual methane emissions originate from coal mining. In the year 2002, 16 countries used coal gas to generate heat and electricity. In many cases, the exact size of coalbed methane reservoirs is not identified. The possibility of a long-term gas production and its profitability at single sites are unknown. To clarify these points, the processes of gas generation as well as the gas-in-place volume have to be determined. Both issues are tackled here for the Ruhr basin. Within this basin, coal gas samples were taken at 13 gas production sites, spread over three samplings within 14 months. There were virtually no changes in the concentrations of gas components at single sites within this period. The isotope composition of methane (δ13C-methane: −40.0 to −57.3‰ vs. PDB) revealed that the produced methane is a mixture of gases of thermogenic and microbial origin. The microbial contribution of methane seems to be more pronounced at sites of active and especially abandoned coal mining than at unmined places. Ethane and propane are of thermogenic origin, with ethane's isotopic composition tending to heavier values (richer in 13C) with time. This time-dependent phenomenon is interpreted as being caused by desorption. In addition, living methanogenic archaea were detected in mine water samples from depths down to 1200 m. 相似文献
357.
Bernhard Heck 《Studia Geophysica et Geodaetica》2011,55(3):441-454
For more than 150 years gravity anomalies have been used for the determination of geoidal heights, height anomalies and the
external gravity field. Due to the fact that precise ellipsoidal heights could not be observed directly, traditionally a free
geodetic boundary-value problem (GBVP) had to be formulated which after linearisation is related to gravity anomalies. Since
nowadays the three-dimensional positions of gravity points can be determined by global navigation satellite systems very precisely,
the modern formulation of the GBVP can be based on gravity disturbances which are related to a fixed GBVP using the known
topographical surface of the Earth as boundary surface. The paper discusses various approaches into the solution of the fixed
GBVP which after linearization corresponds to an oblique-derivative boundary-value problem for the Laplace equation. Among
the analytical solution approaches a Brovar-type solution is worked out in detail, showing many similarities with respect
to the classical solution of the scalar free GBVP. 相似文献