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101.
Prof. Dott. Alfredo Boni 《Pure and Applied Geophysics》1947,10(1-2):192-194
Riassunto Breve descrizione ed analisi dei movimenti franosi verificatisi a Grassura (Cravagliana) nel Gennaio e nel Marzo 1947.
Summary Short report on the rockfalls occured at Grassura (Cravagliana) in January and March 1947.相似文献
102.
Alfredo E. Prelat 《Mathematical Geology》1977,9(4):343-367
The statistical technique of discriminant analysis is used to define target areas for detailed general exploration given only general geological information and aeromagnetic anomaly blues. In the test area, located in Central Norway, on-going exploration surveys have revealed the presence of mineralization; however, it still has not been determined if any of the sites will beeconomically feasible. The area was divided into 1400 1-km × 1-km cells by superimposing square grid on 1:50,000-scale geological and geophysical maps. Later the area was divided into two subareas based on major differences in each area's geology. A number of geological natures and the aeromagnetic anomaly values were coded systematically in each cell. The cells representing an advanced degree of exploration were chosen as control cells in each of the subareas. The geological and geophysical parameters were transformed, by means of relatively simple transformations, to produce near-normal frequency distributions. A discriminant function was then obtained by discriminant analysis to divide the control data into two groups, cells with presence of mineral occurrence and cells without mineral occurrence. the discriminant function obtained for the control area proved to be relevant both geologically and statistically. Consequently, the discriminant equation was applied to cells outside the control area. The cells were assigned to one of the two groups by entering the geologic factors pleasured from the maps into the discriminant model. The exploration potential of a large number of cells was evaluated by this procedure. To test the results, field work including geochemical sampling was carried out in the cells with highest probability of mineral occurrance The field work results have shown that the application of discriminant analysis to geological information at 1:50,000 scale with 1-km × 1-km cells combined with a careful selection of techniques for transforming the variables is a feasible method for predicting gaeralization, and as such could become a valuable tool for mining exploration.This paper was presented at Symposium 116.3, Quantitative Strategy for Exploration, held as part of the 25th International Geological Congress, Sydney, Australia, August 1976. 相似文献
103.
Alfredo B. Henriques 《Astrophysics and Space Science》1996,235(1):129-140
The classical tests of cosmology are applied to a simple cosmological model based on the Kantowski-Sachs metric and the results compared with those obtained for the standard model, based on the FRW metric. It is seen that for a large class of KS models the observations will not be able to distinguish between these models and the standard model. Some comments are also made with respect to the possibility of other tests, those involving the primordial nucleosynthesis and the generation of large scale structure, to constrain the acceptable KS models. 相似文献
104.
Probabilistic seismic hazard for Mainland Portugal was re-evaluated in order to perform its disaggregation. Seismic hazard
was disaggregated considering different spaces of random variables, namely, univariate conditional hazard distributions of
M (magnitude), R (source-to-site distance) and ε (deviation of ground motion to the median value predicted by an attenuation model), bivariate conditional hazard distributions
of M–R and X–Y (seismic source latitude and longitude) or multivariate conditional hazard distributions of M–R–ε and M–(X–Y)–ε. The main objective of the present work was achieved, as it was possible, based on the modal values of the above mentioned
distributions, to characterize the scenarios that dominate some seismic hazard levels of the 278 Mainland Portuguese counties.
In addition, results of 4D disaggregation analysis, in M–(X–Y)–ε, pointed out the existence of one geographic location shared by the dominant scenario of most analyzed counties, especially
for hazard levels correspondent to high return periods. Those dominant scenarios are located offshore at a distance of approximately
70 km WSW of S. Vicente cape. On the other hand, the lower the return period the higher is the number of modal scenarios in
the neighbourhood of the analyzed site. One may conclude that modal scenarios reproduce hazard target values in each site
with great accuracy enabling the applications derived from those scenarios (e.g. loss evaluation) to be associated to a hazard
level exceedance probability. 相似文献
105.
Jaco Weinstock Beth Shapiro Alfredo Prieto Juan Carlos Marín Benito A. González M. Thomas P. Gilbert Eske Willerslev 《Quaternary Science Reviews》2009,28(15-16):1369-1373
We present the results of a palaeogenetic analysis of two Late Pleistocene camelids originating in southern Chile. Our analysis of two mitochondrial DNA fragments (control region and cytochrome b gene) reveals that these specimens do not belong to an extinct taxon, but rather to extant vicuña (Vicugna vicugna), whose modern distribution is restricted to the extreme elevations of the Andes, more than 3500 km to the north of where these specimens originated. Our results also suggest fossil specimens from Patagonia that are currently assigned to the extinct taxon Lama gracilis, may actually belong to V. vicugna, implying a continuous distribution of the latter from the southern tip of South America to the Andes during the Final Pleistocene. The haplotypes of both specimens are not present in modern populations, suggesting a loss of genetic diversity concomitant with the contraction of the vicuña geographical distribution during the Final Pleistocene or early Holocene. 相似文献
106.
G. De Vicente R. Vegas A. Muoz-Martín J.D. Van Wees A. Casas-Sinz A. Sopea Y. Snchez-Moya A. Arche J. Lpez-Gmez A. Olaiz J. Fernndez-Lozano 《Tectonophysics》2009,470(3-4):224-242
The Iberian Chain is a wide intraplate deformation zone formed by the tectonic inversion during the Pyrenean orogeny of a Permian–Mesozoic basin developed in the eastern part of the Iberian Massif. The N–S convergence between Iberia and Eurasia from the Late Cretaceous to the Lower Miocene times produced significant intraplate deformation. The NW–SE oriented Castilian Branch of the Iberian Chain can be considered as a “key zone” where the proposed models for the Cenozoic tectonic evolution of the Iberian Chain can be tested. Structural style of basin inversion suggests mainly strike–slip displacements along previous NW–SE normal faults, developed mostly during the Mesozoic. To confirm this hypothesis, structural and basin evolution analysis, macrostructural Bouguer gravity anomaly analysis, detailed mapping and paleostress inversions have been used to prove the important role of strike slip deformation. In addition, we demonstrate that two main folding trends almost perpendicular (NE–SW to E–W and NW–SE) were simultaneously active in a wide transpressive zone. The two fold trends were generated by different mechanical behaviour, including buckling and bending under constrictive strain conditions. We propose that strain partitioning occurred with oblique compression and transpression during the Cenozoic. 相似文献
107.
José López-Gómez Alfredo Arche Henar Vargas Mariano Marzo 《Sedimentary Geology》2010,223(3-4):320-333
The stratigraphy of a sedimentary basin is mainly the result of the long-term response of a depositional surface to prolonged subsidence. However, the real nature of interrelations between fluvial architecture and subsidence is still unknown. Herein, we present new data on these relationships by combining the results of detailed sedimentological field work with data acquired through automated forward modelling and backstripping for the alluvial Permian and Triassic sediments of the SE Iberian Ranges. Using this methodology, we determined tectonic subsidence of the basin by means of backstripping analysis and crust and lithospheric mantle stretching factors (δ and β, respectively) using forward modelling technique. Results indicated that a configuration of two individual and independent layers during lithospheric subsidence for each tectonic phase fit better for this time of the studied basin evolution than the assumption of subsidence due to a single layer spanning the whole lithosphere.For this study, we simplified fluvial geometries as two main types: isolated (I) and amalgamated (A), with subtypes in each case. Different order bounding surfaces (b.s.) were distinguished in the field, although we only selected those affecting the whole basin under study. These included those b.s. of clear tectonic origin, ranging from individual basin boundary-fault pulses produced over periods of approximately 1 My to those arising from major tectonic events, such as the beginning of extension in the basin, causing major changes in basin geometry over periods of 3–5 My.The comparison of δ and β values and fluvial geometries for each identified tectonic phase in the basin evolution, revealed some possible relationship between subsidence and fluvial geometry: Sections showing the most varied fluvial architectural geometries, including ribbon and nested forms, were related to higher β and δ stretching factors values indicating tectonic phases of greater stretching and subsidence. When both stretching factors were similar and close to 1, fluvial geometry was basically reduced to amalgamated geometry type. Wider ranging of fluvial geometries was associated with stages of basin development in which crust and upper mantle activities differed, that is, showing larger differences of β and δ stretching factors values. The related slope changes are proposed as the main surface control of fluvial styles.Combination of subsidence with other possible controlling factors such as avulsion rate, climate or budget of sediments, gives rise to the definitive alluvial architecture of a basin. 相似文献
108.
Axel Gerik Jörn H. Kruhl Alfredo Caggianelli 《Journal of the Geological Society of India》2010,75(1):210-224
Fractal-geometry-based analysis techniques offer simple and efficient ways for analyzing magmatic fabrics that are otherwise
difficult to describe quantitatively. This study shows an application of two different methods on flow patterns observed in
a syntectonic magmatic body injected into the lower crust. XZ and YZ rock cuts are scanned, and the scans are automatically
transferred to binary patterns of mafic and felsic minerals. These are analyzed by boxcounting as well as the modified Cantor-dust
method. Box-counting leads to characterization of the entire patterns, proves their fractality in two different scale ranges,
and yields information about magma mingling and grain-aggregate forming processes. The modified Cantor-dust method quantifies
the anisotropy of pattern complexity and represents a potentially powerful method for determination of shear sense during
magmatic flow. Both methods represent useful tools specifically for analyzing diffuse magmatic fabrics and for connecting
field-related studies with analyses on the microscale. 相似文献
109.
Aquifer vulnerability and groundwater quality in mega cities: case of the Mexico Basin 总被引:1,自引:0,他引:1
Jose Alfredo Ramos Leal C. Noyola Medrano F. O. Tapia Silva 《Environmental Earth Sciences》2010,61(6):1309-1320
The aquifer system in the Metropolitan Zone of the Mexican Basin is comprised by a higher, middle, and a lower aquifer, separated
by less permeable elements. This study integrated a geographical database from which aquifer vulnerability values were obtained
using the SINTACS method. The results show the lowest vulnerability values in the lacustrine zone of the basin, where most
of the urban area is settled. The medium vulnerability indices are at the edges of the basin and are associated with tuffs,
pyroclasts and alluvial deposits. The highest vulnerability values are in the ranges bordering the basin. High water quality
values are toward the limits of the basin and in the recharge zones while lower quality water is in the Tlahuac and Iztapalapa
zones. The results of this study enable a cause–effect relationship to be established between potential sources of contamination
and groundwater quality indices only for Tlahuac and Iztapalapa, a notable finding since most of the urban area is settled
over low and very low vulnerability zones. 相似文献
110.
Jean-Philippe Boulanger G. Brasseur Andrea Fabiana Carril Manuel de Castro Nicolas Degallier Carlos Ereño H. Le Treut Jose Antonio Marengo Claudio Guillermo Menendez Mario Nestor Nuñez Olga C. Penalba Alfredo Luis Rolla Matilde Rusticucci Rafael Terra 《Climatic change》2010,98(3-4):307-329
The goal of the CLARIS project was to build an integrated European–South American network dedicated to promote common research strategies to observe and predict climate changes and their consequent socio-economic impacts taking into account the climate and societal peculiarities of South America. Reaching that goal placed the present network as a privileged advisor to contribute to the design of adaptation strategies in a region strongly affected by and dependent on climate variability (e.g. agriculture, health, hydro-electricity). Building the CLARIS network required fulfilling the following three objectives: (1) The first objective of CLARIS was to set up and favour the technical transfer and expertise in earth system and regional climate modelling between Europe and South America together with the providing of a list of climate data (observed and simulated) required for model validations; (2) The second objective of CLARIS was to facilitate the exchange of observed and simulated climate data between the climate research groups and to create a South American high-quality climate database for studies in extreme events and long-term climate trends; (3) Finally, the third objective of CLARIS was to strengthen the communication between climate researchers and stakeholders, and to demonstrate the feasibility of using climate information in the decision-making process. 相似文献