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991.
Bedřich Šalamon 《Studia Geophysica et Geodaetica》1963,7(4):313-329
Ohne Zusammenfassung 相似文献
992.
We report the results from a 250 km long transect, from the Danish coast to the North Sea at 55°30′ N, which was sampled every
32 km in order to study the composition and distribution of phytoplankton, and their dependence on the distance from the coast,
depth and other environmental factors. Altogether 144 species of algae were identified by light, epifluorescence and electron
microscopy. Some ecological preferences were found on the basis of measured environmental parameters and compared with the
literature. Possible controlling mechanisms for the distribution patterns of the plankton algae were analyzed by multivariate
statistics. Only distance from the coast was found to be a significant factor for algal distribution along the transect. Three
main areas of the transect were found: the coastal, middle and oceanic areas. Diatoms, mainly the centric ones, were the most
abundant group of algae. The other less abundant groups were Dinophyceae, Dictyochophyceae, Prasinophyceae and Chlorophyceae.
The pattern of distribution of diatoms and dinophytes along the transect was more or less similar, with larger numbers of
cells found close to both the eastern and western parts of the transect, although the species composition was different. Some
species were found to prefer coastal waters, other species were characterized as oceanic, and several species were found at
all stations. Porosira glacialis showed an atypical distribution along the transect, with highest abundances at both coastal and oceanic stations. 相似文献
993.
E. SKRZYPEK P. ŠTÍPSKÁ K. SCHULMANN O. LEXA M. LEXOVÁ 《Journal of Metamorphic Geology》2011,29(4):451-472
In the Orlica–?nie?nik Dome (NE Bohemian massif), alternating belts of orthogneiss with high‐pressure rocks and belts of mid‐crustal metasedimentary–metavolcanic rocks commonly display a dominant subvertical fabric deformed into a subhorizontal foliation. The first macroscopic foliation is subvertical, strikes NE–SW and is heterogeneously folded by open to isoclinal folds with subhorizontal axial planes parallel to the heterogeneously developed flat‐lying foliation. The metamorphic evolution of the mid‐crustal metasedimentary rocks involved successive crystallization of chlorite–muscovite–ilmenite–plagioclase–garnet, followed by staurolite‐bearing and then kyanite‐bearing assemblages in the subvertical fabric. This was followed by garnet retrogression, with syntectonic crystallization of sillimanite and andalusite parallel to the shallow‐dipping foliation. Elsewhere, andalusite and cordierite statically overgrew the flat‐lying fabric. With reference to a P–T pseudosection for a representative sample, the prograde succession of mineral assemblages and the garnet zoning pattern with decreasing grossular, spessartine and XFe are compatible with a P–T path from 3.5–5 kbar/490–520 °C to peak conditions of 6–7 kbar/~630 °C suggesting burial from 12 to 25 km with increasing temperature. Using the same pseudosection, the retrograde succession of minerals shows decompression to sillimanite stability at ~4 kbar/~630 °C and to andalusite–cordierite stability at 2–3 kbar indicating exhumation from 25 km to around 9–12 km. Subsequent exhumation to ~6 km occurred without apparent formation of a deformation fabric. The structure and petrology together with the spatial distribution of the metasedimentary–metavolcanic rocks, and gneissic and high‐pressure belts are compatible with a model of burial of limited parts of the upper and middle crust in narrow cusp‐like synclines, synchronous with the exhumation of orogenic lower crust represented by the gneissic and high‐pressure rocks in lobe‐shaped and volumetrically more important anticlines. Converging P–T–D paths for the metasedimentary rocks and the adjacent high‐pressure rocks are due to vertical exchanges between cold and hot vertically moving masses. Finally, the retrograde shallow‐dipping fabric affects both the metasedimentary–metavolcanic rocks and the gneissic and high‐pressure rocks, and indicates that the ~15‐km exhumation was mostly accommodated by heterogeneous ductile thinning associated with unroofing of a buoyant crustal root. 相似文献
994.
995.
Jiří Vaněk 《Studia Geophysica et Geodaetica》2000,44(1):86-86
996.
997.
998.
Sibila Borojević Šoštarić Ladislav A. Palinkaš Sabina Strmić Palinkaš Vladimir Bermanec Franz Neubauer Jorge Spangenberg Walter Prochaska 《Mineralogy and Petrology》2009,97(1-2):111-128
The Petrova and Trgovska Gora Mts. (Gora=Mountain) are Variscan basement units incorporated into the northwestern Dinarides during the Alpine orogeny. They host numerous siderite-quartz-polysulphide, siderite-chalcopyrite, siderite-galena and barite veins, as well as stratabound hydrothermal-replacement ankerite bodies within carbonates in non-metamorphosed, flysch-like Permo-Carboniferous sequences. The deposits have been mined for Cu, Pb, Ag and Fe ores since Medieval times. Fluid inclusion studies of quartz from siderite-polysulphide-quartz and barite veins of both regions have shown the presence of primary aqueous NaCl?CaCl2±MgCl2?H2O±CO2 inclusions. The quartz-sulphide stage of both regions show variable salinities; 2.7–26.2 wt% NaCl eq. for the Trgovska Gora region and 3.4–23.4 wt% NaCl eq. for the Petrova gora region, and similar homogenisation temperatures (100–230°C). Finally, barite is precipitated from low salinity-low temperature solutions (3.7–15.8 wt % NaCl equ. and 115–145°C). P-t conditions estimated via isochore construction yield formation temperatures between 180–250°C for the quartz-sulphide stage and 160–180°C for the barite stage, using a maximum lithostatic pressure of 1 kbar (cc. 3 km of overburden). The sulphur isotope composition of barite from both deposits indicates the involvement of Permian seawater in ore fluids. This is supported by the elevated bromium content of the fluid inclusion leachates (120–660 ppm in quartz, 420–960 ppm in barite) with respect to the seawater, indicating evaporated seawater as the major portion of the ore-forming fluids. Variable sulphur isotope compositions of galena, pyrite and chalcopyrite, between ?3.2 and +2.7‰, are interpreted as a product of incomplete thermal reduction of the Permian marine sulphate mixed with organically- and pyrite-bound sulphur from the host sedimentary rocks. Ore-forming fluids are interpreted as deep-circulating fluids derived primarily from evaporated Permian seawater and later modified by interaction with the Variscan basement rocks. 40Ar/39Ar data of the detrital mica from the host rocks yielded the Variscan age overprinted by an Early Permian tectonothermal event dated at 266–274 Ma. These ages are interpreted as those reflecting hydrothermal activity correlated with an incipient intracontinental rifting in the Tethyan domain. Nevertheless, 75 Ma recorded at a fine-grained sericite sample from the alteration zone is interpreted as a result of later resetting of white mica during Campanian opening/closure of the Sava back arc in the neighbouring Sava suture zone (Ustaszewski et al. 2008). 相似文献
999.
Decorative marbles from the Krkonoše-Jizera Terrane (Bohemian Massif,Czech Republic): provenance criteria 总被引:1,自引:0,他引:1
Marbles from western part of the Krkonoše-Jizera Terrane (northern part of the Bohemian Massif) have been studied to obtain
mineropetrographic and chemical reference data for provenance studies. Samples from six different quarries were analysed by
mineralogical-petrographic and geochemical methods (optical microscopy, X-ray diffraction, stable isotope ratio analysis,
cathodoluminescence, bulk magnetic susceptibility). Petrographic characteristics permit a distinction between fine-grained
to medium-grained marbles from the Jizera Mts (amphibolite metamorphic facies) and fine-grained marbles from the Ještěd Mts
(low-grade greenschist facies). The samples studied are mainly calcitic, with the exception of those from Raspenava in which
dolomite is abundant in two types. The mineralogical composition of the insoluble residues is clinochlore ± serpentine ± tremolite ± diopside ± pyrite + magnetite
in case of the locality Raspenava and clinochlore + muscovite ± quartz ± pyrite ± rutile ± haematite in case of the localities
from the Ještěd Mts. δ13C and δ18O variations in primary and secondary carbonate phases allow to distinguish genetically different carbonate veins and permit
quarry separation in one case (Raspenava, Jizera Mts). The δ13C and δ18O values of the groundmass range from −1 to +3‰ and from −8 to −20‰ (PDB), respectively. The δ13C and δ18O values of secondary carbonate veins decrease to −3‰ and reach more negative values up to −26‰ in case of δ18O. The fabric of cathodomicrofacies allows the distinction between calcite and dolomite, except three localities (Pilínkov,
Horní Hanychov, Jitrava—rose type) with majority of quenchers (high content of iron in carbonate). The genetically different
calcite is characterised by a pale and dark orange luminescence distribution. Serpentine, tremolite, forsterite, opaque minerals
and quartz have no luminescence and very dull luminescence, respectively. The majority of studied marbles exhibits low values
of the bulk magnetic susceptibility, with the exception of those from Raspenava rich in magnetite. 相似文献
1000.
Atmospheric waves influence the dynamics and energetic budget of the upper atmosphere. Using the continuous HF Doppler sounder,
we study the wave activity in the ionosphere during tropospheric convective storms in western and central part of the Czech
Republic. The study is focused on acoustic-gravity waves in the period range 2–30 minutes. We discuss possible methods of
distinguishing the waves emitted by meteorological sources from waves of different origin, particularly waves of geomagnetic
origin. In two cases out of twenty-five analysed, we found waves in the infrasonic period range which might be generated by
exceptionally intense meteorological activity in the troposphere. The results differ considerably from those previously obtained
in North America. In the central part of the United States, infrasonic waves were frequently observed during convective storms.
As a possible reason, we discuss different intensity and dynamics of weather systems in both regions. 相似文献