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311.
Antonella Bertagnini Alessio Di Roberto Massimo Pompilio 《Bulletin of Volcanology》2011,73(9):1229-1243
The persistent normal activity of Stromboli is occasionally interrupted by sudden and highly energetic explosive events called
Strombolian paroxysms. These phenomena together with landslide-generated tsunamis represent the most hazardous manifestations
of present-day volcanic activity at Stromboli. The most recent paroxysms, on 5 April 2003 and 15 March 2007, have drawn attention
to these energetic events because they significantly threatened inhabitants and tourists. Historical accounts and field evidence
indicate, however, that even larger paroxysms, in terms of volume, dispersal of products and intensity of explosive phenomena,
occurred in the recent past. During these paroxysms incipiently welded spatter deposits mantled the north and south rims of
the Sciara del Fuoco down to low elevations, extending much farther than the similar deposits from recent observed events
(5 April 2003 and 15 March 2007). In order to identify, characterize and discriminate among products of these outstanding
spatter-forming eruptions, more than 50 stratigraphic sections were measured and sampled. Stratigraphic, sedimentological
and radiometric (14C) data indicate that only two paroxysms produced spatter that reached very low elevations and inhabited areas: the first
occurred in the 16th century and the last in AD 1930. Analysis of texture and deposit components reveals that the early phases
of the two eruptions were driven by distinctly different eruptive dynamics. Both identified paroxysms are at least one order
of magnitude greater than any similar event observed by monitoring systems at Stromboli. These two large paroxysms were the
most powerful volcanic events at Stromboli in the last eighteen centuries. 相似文献
312.
Fracassini Massimo Gilardoni Giorgio Pasinetti Laura E. 《Astrophysics and Space Science》1973,22(1):141-152
The spectrophotometric method for computing the apparent stellar diameters, proposed by Chalonge and Divan (1950) and modified by Fracassini and Pasinetti (1967) has been applied to 172 B5V-A5V stars (single and belonging to galactic clusters) of the Catalogue of Geneva Observatory (Rufener, 1971). In the straight line diagrams log vsm, drawn for the stars of the same spectral type, it is possible to identify some peculiar stars (with peculiarities in the diameter or monochromatic brightness). The agreement with the values of the apparent diameters of Leo, Ori, Lyr and CMa, obtained by Hanbury Brownet al. (1967), is very good. The comparison with the diagramss
v
vs (B-V)0,R vs (B-V)0 deduced by Wesselink (1969), seems satisfactory. The comparison with the results obtained by other authors and the great number of stars which will be observed in the photometric system in seven colors of Geneva, demonstrate the wide possibilities of this spectrophotometric method for determining the apparent stellar diameters.
Thesis for the degree on Applied Physics. 相似文献
Sommario Il metodo spettrofotometrico di Chalonge e Divan (1950) per il calcolo dei diametri stellari apparenti, modificato da Fracassini e Pasinetti (1967), è stato applicato a 172 stelle B5V-A5V (isolate e in ammassi galattici) del Catalogo dell'Osservatorio di Ginevra (Rufener, 1971). Costruiti i diagrammi lineari log -m v per i vari gruppi di stelle dello stesso tipo spettrale, è possibile identificare alcune stelle peculiari con diametri e brillanze monochromatiche anomale. Il confronto con i diametti apparenti di Leo, Ori, Lyr e CMa determinati da Hanbury Brownet al. (1967) mostra un accordo molto buono. Il confronto con le relazionis v -(B-V)0eR-(B-V) 0 ottenute da Wesselink (1969) appare soddisfacente. Il confronto con i risultati ottenuti da altri autori e il grande numero di stelle che saranno osservate nel sistema fotometrico in sette colori di Ginevra, dimostrano le ampie possibilità di questo metodo spettrofotometrico per la determinazione dei diametri stellari apparenti.
Thesis for the degree on Applied Physics. 相似文献
313.
Jan Košler Jiří Sláma Elena Belousova Fernando Corfu George E. Gehrels Axel Gerdes Matthew S. A. Horstwood Keith N. Sircombe Paul J. Sylvester Massimo Tiepolo Martin J. Whitehouse Jon D. Woodhead 《Geostandards and Geoanalytical Research》2013,37(3):243-259
Inter‐laboratory comparison of laser ablation ICP‐MS and SIMS U‐Pb dating of synthetic detrital zircon samples provides an insight into the state‐of‐the art of sedimentary provenance studies. Here, we report results obtained from ten laboratories that routinely perform this type of work. The achieved level of bias was mostly within ± 2% relative to the ID‐TIMS U‐Pb ages of zircons in the detrital sample, and the variation is likely to be attributed to variable Pb/U elemental fractionation due to zircon matrix differences between the samples and the reference materials used for standardisation. It has been determined that ~ 5% age difference between adjacent age peaks is currently at the limit of what can be routinely resolved by the in situ dating of detrital zircon samples. Precision of individual zircon age determination mostly reflects the data reduction and procedures of measurement uncertainty propagation, and it is largely independent of the instrumentation, analytical technique and reference samples used for standardisation. All laboratories showed a bias towards selection of larger zircon grains for analysis. The experiment confirms the previously published estimates of the minimum number of grains that have to be analysed in order to detect minor zircon age populations in detrital samples. 相似文献
314.
İbrahim Uysal E. Yalçın Ersoy Orhan Karslı Yildirim Dilek M. Burhan Sadıklar Chris J. Ottley Massimo Tiepolo Thomas Meisel 《Lithos》2012
We present new, whole-rock major and trace element chemistry, including rare earth elements (REE), platinum-group elements (PGE), and Re–Os isotope data from the upper mantle peridotites of a Cretaceous Neo-Tethyan ophiolite in the Mu?la area in SW Turkey. We also report extensive mineral chemistry data for these peridotites in order to better constrain their petrogenesis and tectonic environment of formation. The Mu?la peridotites consist mainly of cpx-harzburgite, depleted harzburgite, and dunite. Cpx-harzburgites are characterized by their higher average CaO (2.27 wt.%), Al2O3 (2.07 wt.%), REE (53 ppb), and 187Os/188Os(i) ratios varying between 0.12497 and 0.12858. They contain Al-rich pyroxene with lower Cr content of coexisting spinel (Cr# = 13–22). In contrast, the depleted harzburgites and dunites are characterized by their lower average CaO (0.58 wt.%), Al2O3 (0.42 wt.%), and REE (1.24 ppb) values. Their clinopyroxenes are Al-poor and coexist with high-Cr spinel (Cr# = 33–83). The 187Os/188Os(i) ratios are in the range of 0.12078–0.12588 and are more unradiogenic compared to those of the cpx-harzburgites.Mineral chemistry and whole rock trace and PGE data indicate that formation of the Mu?la peridotites cannot be explained by a single stage melting event; at least two-stages of melting and refertilization processes are needed to explain their geochemical characteristics. Trace element compositions of the cpx-harzburgites can be modeled by up to ~ 10–16% closed-system dynamic melting of a primitive mantle source, whereas those of the depleted harzburgites and dunites can be reproduced by ~ 10–16% open-system melting of an already depleted (~ 16%) mantle. These models indicate that the cpx-harzburgites are the products of first-stage melting and low-degrees of melt–rock interaction that occurred in a mid-ocean ridge (MOR) environment. However, the depleted harzburgites and dunites are the product of second-stage melting and related refertilization which took place in a supra subduction zone (SSZ) environment. The Re–Os isotope systematics of the Mu?la peridotites gives model age clusters of ~ 250 Ma, ~ 400 Ma and ~ 750 Ma that may record major tectonic events associated with the geodynamic evolution of the Neo-Tethyan, Rheic, and Proto-Tethyan oceans, respectively. Furthermore, > 1000 Ma model ages can be interpreted as a result of an ancient melting event before the Proto-Tethys evolution. 相似文献
315.
Application and validation of bivariate GIS-based landslide susceptibility assessment for the Vitravo river catchment (Calabria,south Italy) 总被引:3,自引:1,他引:2
Massimo Conforti Gaetano Robustelli Francesco Muto Salvatore Critelli 《Natural Hazards》2012,61(1):127-141
The Calabria (Southern Italy) region is characterized by many geological hazards among which landslides, due to the geological,
geomorphological, and climatic characteristics, constitute one of the major cause of significant and widespread damage. The
present work aims to exploit a bivariate statistics-based approach for drafting a landslide susceptibility map in a specific
scenario of the region (the Vitravo River catchment) to provide a useful and easy tool for future land planning. Landslides
have been detected through air-photo interpretation and field surveys, by identifying both the landslide detachment zones
(LDZ) and landslide bodies; a geospatial database of predisposing factors has been constructed using the ESRI ArcView 3.2
GIS. The landslide susceptibility has been assessed by computing the weighting values (Wi) for each class of the predisposing factors (lithology, proximity to fault and drainage line, land use, slope angle, aspect,
plan curvature), thus evaluating the distribution of the landslide detachment zones within each class. The extracted predisposing
factors maps have then been re-classified on the basis of the calculated weighting values (Wi) and by means of overlay processes. Finally, the landslide susceptibility map has been considered by five classes. It has
been determined that a high percentage (61%) of the study area is characterized by a high to very high degree of susceptibility;
clay and marly lithologies, and slope exceeding 20° in inclination would be much prone to landsliding. Furthermore, in order
to ascertain the proposed landslide susceptibility estimate, a validation procedure has been carried out, by splitting the
landslide detachment zones into two groups: a training and a validation set. By means of the training set, the susceptibility
map has first been produced; then, it has been compared with the validation set. As a result, a great majority of LDZ-validation
set (85%) would be located in highly and very highly susceptible areas. The predictive power of the model is considered reliable,
since more than 50% of the LDZ fall into 20% of the most susceptible areas. The reliability of the susceptibility map is also
suggested by computing the SCAI index, true positive and false positive rates; nevertheless, the most susceptible areas are
overestimated. As a whole, the results indicate that landslide susceptibility assessment based on a bivariate statistics-based
method in a GIS environment may be useful for land planning policy, especially when considering its cost/benefit ratio and
the need of using an easy tool. 相似文献
316.
317.
318.
Abstract— This forensic work aims to authenticate the recovery location of Castenaso, a 120 g ordinary chondritic (L5) meteorite reportedly found in 2003 along the sandy bank of the Idice Stream, near the village of Castenaso (Bologna, Emilia‐Romagna, Italy). Using the hypothesis that Castenaso was instead a hot‐desert meteorite, we conducted a comparative mineralogical and geochemical study of major weathering effects on European and Saharan ordinary chondrites as potential markers of the environment where Castenaso resided during its terrestrial lifetime. Inductively coupled plasma‐mass spectrometry (ICP‐MS) data reveals that Castenaso is significantly enriched in Sr, Ba, Tl, and U, and suggests geochemical alteration in a hot‐desert environment. The alteration is minor: Castenaso is not coated by desert varnish and does not show significant light rare earth element (LREE) enrichment or loss of Ni and Co. The apparent contrast in size, morphology, and composition between the soil particles filling the external fractures of Castenaso and those from the bank of the Idice Stream observed under the scanning electron microscope (SEM) suggests that Castenaso did not reside at the reported find location. Abraded quartz grains (up to 1 mm in size) in Castenaso are undoubtedly from a hot‐desert eolian environment: they are well‐rounded and show external surfaces characterized by the presence of dish‐shaped concavities and upturned silica plates that have been subject to solution‐precipitation and subsequent smoothing. We therefore conclude that Castenaso is one of the many hot‐desert ordinary chondrite finds, probably from the Sahara, that is currently available on the market. This forensic work provides the scientific grounds for changing the name of this meteorite. 相似文献
319.
Riccardo Tribuzio Massimo Tiepolo Stefania Fiameni 《Contributions to Mineralogy and Petrology》2008,155(5):619-633
The layered sequence from Niagara Icefalls (northern Victoria Land, Antarctica) is related to the Cambrian-Early Ordovician
Ross Orogeny. The sequence consists of dunites, harzburgites, orthopyroxenites, melagabbronorites and gabbronorites of cumulus
origin. The Mg# of olivine, spinel, orthopyroxene and clinopyroxene from these rocks yields positive correlations, thus indicating
formation from melts that mainly evolved through fractional crystallisation. The following fractionation sequence was identified:
olivine (up to 94 mol% forsterite) + Cr-rich spinel → olivine + orthopyroxene ± spinel → orthopyroxene → orthopyroxene + anorthite-rich
plagioclase ± clinopyroxene. Clinopyroxenes retain the peculiar trace element signature of boninite melts, such as extremely
low concentrations of HREE and HFSE, and LILE enrichment over REE and HFSE. U–Pb isotope data on zircons separated from a
gabbronorite have allowed us to constrain the age of emplacement of the Niagara Icefalls sequence at ∼514 Ma. The occurrence
of inherited zircons dated at ∼538 Ma indicates that the boninitic melts experienced, at least locally, crustal contamination.
The Niagara Icefalls sequence can be related to a regional scale magmatic event that affected the eastern margin of the Gondwana
supercontinent in the Middle Cambrian. We propose that the formation of the sequence was associated with the development of
an embryonic back-arc basin in an active continental margin.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献