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1.
Summary Boron-doped mullites were synthesized using aluminium nitrate-nonahydrate, tetraethoxysilane and boric acid in a sol–gel process
with subsequent annealing at 950 and 1300 °C for five hours. Two different bulk compositions with constant Al2O3 contents (60 and 70 mol%, respectively) and varying SiO2 plus B2O3 contents were investigated. X-ray powder diffraction analyses yielded a linear decrease of the lattice parameters with increasing
bulk B2O3 content, which was interpreted as to be due to boron incorporation. Related to the increasing boron content, corresponding
infrared spectra revealed a slight and continuous shift for most of the absorption bands. These data show that mullite is
able to incorporate large amounts of boron into its structure (up to about 20 mol% B2O3 depending on the bulk composition of the starting materials). Infrared analyses suggest that boron is incorporated into the
mullite structure in form of planar three-fold coordinated BO3 groups.
Author’s address: A. Beran, Institut für Mineralogie und Kristallographie, Universit?t Wien-Geozentrum, Althanstra?e 14, 1090 Wien, Austria 相似文献
2.
Prof. Dr. A. Beran 《Mineralogy and Petrology》1990,41(2-4):73-79
Summary IR spectra of phenakite single crystals from different localities show a distinct variability in the region of the OH stretching fundamental. Minute hydrous mineral phases (tourmaline, bertrandite) are included in Piracicaba phenakite. Structural OH, ranging up to 0.005 equivalent wt.% H2O, is characterized by two extremely pleochroic bands centered at 3380 and 3120 cm–1. On the basis of their pleochroic scheme it is proposed that (O2(OH)2) and (O3(OH)) tetrahedra occur as structural elements, assuming that the vacancies are on Be sites.
With 3 Figures 相似文献
Das Auftreten von OH Absorptionen in Phenakit—eine IR spektroskopische Untersuchung
Zusammenfassung Die IR Spektren von Phenakit-Einkristallen verschiedener Vorkommen zeigen im Bereich der OH-Streckschwingungen eine deutliche Variabilität. Piracicaba Phenakit enthält feinste Einschlüsse von OH-hältigen Mineralphasen (Turmalin, Bertrandit). Strukturell gebundene OH-Gruppen (bis 0,005 äquivalente Gew.% H2O) sind durch zwei extrem pleochroitische Banden bei 3380 und 3120 cm–1 charakterisiert. Unter der Annahme von Be-Leerstellen werden aufgrund des Pleochroismus dieser Banden (O2(OH)2) und (O3(OH)) Tetraeder als strukturelle Baueinheiten vorgeschlagen.
With 3 Figures 相似文献
3.
4.
A new type of tungsten deposit was discovered in the Eastern Alps at the Mallnock, Nock mountains, Austria. The mineralization is restricted to concordant layers of carbonate rocks within phyllites belonging to the metamorphic Palaeozoic of the Upper Austroalpine Gurktal nappe system. Wolframite (ferberite 95) and scheelite occur as network fissure fillings in coarse-grained Fe-magnesite (siderite 15) rocks (average W content ca. 0.9 wt%); fine-grained dolomite marbles contain scheelite as the only tungsten mineral (average W content ca. 0.5 wt%). Assuming the dolomite marbles as a primary metal source, mobilization processes are responsible for the formation of the wolframite- and scheelite-bearing Fe-magnesite rocks. 相似文献
5.
Polarized infrared absorption spectra of thin single-crystal slabs parallel to (010) and (001) of a staurolite from Pizzo Forno, Ticino, with analyzed composition (Fe2.9Mg0.9Zn0.1Mn0.1)Al17.5Ti0.1(Si7.7Al0.3)O48H3 have been measured in the range of 3000–4000 cm?1. From the pleochroitic behaviour of the OH-vibrations three groups of bands can be distinguished: the bands of group I, a strong band at 3445 cm?1 plus a weak shoulder at 3358 cm?1, and the bands of group II, a weak band centered at 3677 cm?1 plus a shoulder at 3635 cm?1, are assigned to the H1 and H2 protons, respectively. The bands of group III, a weak band at 3577 cm?1 plus a shoulder, cannot be interpreted on the basis of the proton positions known so far. We assign them to an additional proton H3, which is bonded to O1 and shows a bifurcated hydrogen bridge to two O5 in a vacant T2 site. 相似文献
6.
Polarized infrared (IR) spectroscopy of olivine crystals from Zabargad, Red Sea shows the existence of four pleochroic absorption bands at 3,590, 3,570, 3,520 and 3,230 cm?1, and of one non pleochroic band at 3,400 cm?1. The bands are assigned to OH stretching frequencies. Transmission electron microscopy (TEM) shows no oriented intergrowths in this olivine; it is concluded that OH is structural. On the basis of the pleochroic scheme of the absorption spectra it is proposed that [□O(OH)3] and [□O2(OH)2] tetrahedra occur as structural elements, assuming that the vacancies are on Si sites. If M2 site vacancies were assumed [SiO3(OH)] and [SiO2(OH)2] tetrahedra occur as structural elements. 相似文献
7.
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9.
Zusammenfassung Rutile, Cassiterite und Brookite verschiedener Fundorte enthalten entsprechend einer scharfen Absorptionslinie bei =3 kleine Mengen von Hydroxyl-Gruppen. Die Zuordnung der Absorptionslinie zur OH-Streckschwingung wurde für diese drei Minerale durch die Linienverschiebung bewiesen, die man nach hydrothermaler Deuterierung beobachtet. Die ungefähre Orientierung der OH-Gruppen konnte aus dem Pleochroismus orientierter Kristallplatten abgeleitet werden, wobei polarisierte UR-Strahlung verwendet wurde. Es wird die strukturelle Deutung gebracht. Anatas alpiner Herkunft enthält keine oder nur sehr wenige OH-Gruppen.
Mit 8 Abbildungen 相似文献
Measurement of the infrared-pleochroism in Minerals. XI. The Pleochroism of the OH-stretching frequency in rutile, anatase, brookite, and cassiterite
Summary Rutile, cassiterite, and brookite from several localities contain small amounts of hydroxyl groups, based on the presence of a sharp absorption line at =3. The attribution of the absorption line to the OH-stretching vibration is proved for the three minerals by the line shift which is caused by hydrothermal deuteration. The approximate orientation of the OH-groups could be derived from the pleochroism as observed in oriented crystal plates with polarized IR-radiation. The structural interpretations are given. Anatase, however, from Alpine fissures contains no or undedectable amounts of OH-groups.
Mit 8 Abbildungen 相似文献
10.
Zusammenfassung Mikroskopisch Einschluß-freie Andalusite aus Brasilien zeigen im UR-Absorptionsspektrum ein Doppelmaximum bei zirka 2,9 und ein deutlich schwächeres einfaches Maximum bei 3,04 , die OH-Valenzschwingungen zugeordnet werden. Diese Maxima verschwinden nach mehrtägigem Glühen bei 1000° C. In Platten parallel (110) zeigt das Doppelmaximum bei zirka 2,9 einen extrem starken Pleochroismus, wobei die Bande praktisch völlig verschwindet, wenn der elektrische Vektor parallel [001] schwingt. Damit müssen zumindest die OH-Gruppen, die für diese Bande verantwortlich sind, in die Struktur eingebaut sein. Für beide Arten von OH-Gruppen werden die plausiblen Anordnungen diskutiert.
Mit 3 Abbildungen 相似文献
Measurement of the infrared-pleochroism in minerals. VIII. The pleochroism of the OH-stretching frequency in andalusite
Summary Inclusion-free andalusites from Brazil show in the IR absorption spectrum a double maximum at ca. 2.9 and a much weaker single maximum at 3.04 which are interpreted as belonging to OH-stretching frequencies. The maxima disappear after annealing the specimen at 1000°C for several days. Plates parallel to (110) show a very strong pleochroism for the 2.9 -band, the peak being practically of zero height if the electric vector vibrates parallel [001]. This proves that at least the OH-groups which are responsible for this absorption band are constituents of the crystal structure. For both kinds of OH-groups the probable distributions are discussed.
Mit 3 Abbildungen 相似文献