全文获取类型
收费全文 | 1120篇 |
免费 | 27篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 42篇 |
大气科学 | 98篇 |
地球物理 | 228篇 |
地质学 | 502篇 |
海洋学 | 47篇 |
天文学 | 176篇 |
综合类 | 3篇 |
自然地理 | 68篇 |
出版年
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 16篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 25篇 |
2015年 | 22篇 |
2014年 | 35篇 |
2013年 | 52篇 |
2012年 | 40篇 |
2011年 | 42篇 |
2010年 | 50篇 |
2009年 | 46篇 |
2008年 | 42篇 |
2007年 | 49篇 |
2006年 | 36篇 |
2005年 | 38篇 |
2004年 | 33篇 |
2003年 | 31篇 |
2002年 | 40篇 |
2001年 | 37篇 |
2000年 | 21篇 |
1999年 | 23篇 |
1998年 | 22篇 |
1997年 | 19篇 |
1996年 | 30篇 |
1995年 | 21篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 23篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1976年 | 7篇 |
1975年 | 10篇 |
1973年 | 12篇 |
1971年 | 9篇 |
1958年 | 5篇 |
排序方式: 共有1164条查询结果,搜索用时 218 毫秒
101.
Helmcke DGZG University of Goettingen D Goettingen GermanyIngavat Helmcke Rc/o GZG University of Goettingen D Goettingen GermanyFeng QinglaiFaculty of Earth Sciences China University of Geosciences Wuhan Wagner B Heppe KGZG 《中国地质大学学报(英文版)》2001,12(3)
INTRODUCTIONTheSimaoregion (SWYunnan ,China) ,situatedbe tweentheAilaoshanbeltintheeastandtheLancangjiangzoneinthewest (Fig .1) ,isakeyareatochronologicallyconstrainlatePaleozoiccompressionaldeformationsandthusofprimein terestwhendiscussingtheplate tectonichi… 相似文献
102.
Martin Gast Wolfgang Schaaf Joerg Scherzer Rudolf Wilden Bernd U. Schneider Reinhard F. Hüttl 《Journal of Geochemical Exploration》2001,73(2):196
To analyze the development of pine ecosystems on lignite and pyrite containing mine soils, four pine stands with ages of 3–35 years were investigated in a chronosequence approach. Bulk precipitation, throughfall and soil solution in depths of 20, 40, 70 and 100 cm were studied over a three-year period to determine element fluxes in these forest ecosystems on extreme acidic and saline soils.Element budgets are controlled by the processes induced by pyrite oxidation such as intensive weathering of primary minerals, precipitation and leaching of secondary phases.Despite low water fluxes, element outputs can reach extraordinary high values due to very high concentrations in the soil solution. Although element outputs decrease drastically with stand age, respectively, site age, they exceed those of comparable pine stands on non-mine sites. Nitrogen release from the lignite fraction represents a special characteristic of the examined substrates. Nitrogen losses beneath the rooted zone can be 34 kg N ha−1 yr−1 in 100 cm depth. Element input and output in the examined ecosystems are far from balance. Closed cycling of nutrients seems to be recognizable in the case of potassium. 相似文献
103.
104.
105.
106.
Summary The global power of the differences of altimetric sea heights at collocated points in the first 44 cycles of the Topex/Poseidon (T/P) mission, apparently shows the influence of errors in the major tides and long period ocean signals. Results show the principal semidiurnal tides (M2/S2 lumped together) in the Cartwright and Ray (1991) model are probably in error globally by 3–4 cm (rms). The dominant fluctuation in the differences over the 44 cycles (14 months total) arises from an annual signal of 4–6 cm (rms), significantly greater than long term climate data suggests (but with considerable uncertainty due to unresolved semiannual effects). 相似文献
107.
Dr. H. Stiller Dr. Dr. F. Frölich Dipl.-Geophys. F. Ch. Wagner 《Pure and Applied Geophysics》1961,49(1):129-136
Summary The normal type of serpentinites consists of chrysotile. The magnetite parts are essential parts of the structure of chrysotile serpentinites (primary magnetite). Chrysotile is changed to antigorite by mechanical deformations. The magnetite parts of rock structure are lost and they sat down in the veins of serpentinite rocks (secondary magnetite). In this paper the thermomagnetic diagrams and the results of X-ray investigations of secondary and primary magnetite are described. Some results of susceptibility measurements are given. The secondary magnetite is characterized by a region of oxydation in the interval 280–400° C (secondary magnetite-Fe2O3-Fe2O3). The oxydation to -Fe2O3 is remarkably. On the thermomagnetic diagrams of primary magnetite no typical oxydation region is to be seen. The oxydation: primary magnetite-Fe2O3 is very small. The interval of measured susceptibility values amounts to (10–1500)·10–6 cgs units. The essential variability of the main parts of serpentinite samples is characterized by the great changes of susceptibility values from point to point.The determined values of specific saturation magnetization (Gauss. cm3 g–1), the X-ray powder data, and some results on remanent magnetization are given.
Zusammenfassung Die Normaltypserpentinite bestehen aus Chrysotil. Der Magnetit ist Bestandteil der Struktur der Chrysotilserpentinite (primärer Magnetit). Unter dem Einfluß mechanischer Deformationen geht Chrysotil in Antigorit über. Die Magnetitanteile der Gesteinsstruktur gehen verloren und scheiden sich auf Klüften ab (sekundärer Magnetit). In der vorliegenden Arbeit werden die thermomagnetischen Abhängigkeiten und die Ergebnisse von Röntgenuntersuchungen des sekundären und primären Magnetits beschrieben. Es werden einige Ergebnisse der Suszeptibilitätsmessungen angeführt. Der sekundäre Magnetit wird durch einen Oxydationsbereich im Temperaturintervall 280–400° C charakterisiert (sekundärer Magnetit-Fe2O3-Fe2O3). Die Oxydation zu -Fe2O3 ist beträchtlich. Die thermomagnetischen Diagramme des primären Magnetits zeigen keinen typischen Oxydationsbereich. Die Oxydation: primärer Magnetit-Fe2O3 ist sehr gering. Das Intervall der gemessenen Suszeptibilitätswerte beträgt (10–1500)·10–6 CGS-Einheiten. Die starke Veränderlichkeit der Hauptbestandteile der Serpentinitproben wird durch die großen Änderungen der Suszeptibilitätswerte von Punkt zu Punkt gekennzeichnet.Die gemessenen Werte der Sättigungsmagnetisierung (Gauss.cm3 g–1), der Röntgenuntersuchungen und einige Ergebnisse über die remanente Magnetisierung werden gegeben.相似文献
108.
Zusammenfassung Aus dem Zirkulationstheorem von V. Bjerknes wird eine Formel (Seite17, Formel (6)) für die praktische Berechnung von Meeresströmungen abgeleitet, welche über jene von B. Helland-Hansen und J.W. Sandström hinausgeht. Der neuen Formel lä\t sich der Gültigkeitsbereich der alten entnehmen, wenn man die Grö\enordnung der horizontalen Scherung sowie der Divergenzen kennt.
V. Bjerknes' circulation theorem and its application to oceanographic research
Summary From V. Bjerknes' circulation theorem a new formula (see page 17, (6)) is derived allowing practical computations of ocean currents to be made. The new formula surpasses that one given by B. Helland-Hansen and J. W. Sandström. The range of validity of the old formula can be deduced from the new one if the order of magnitude of horizontal shearing as well as that of the divergences are known.
Le théorème de circulation d'après V. Bjerknes et son application à des recherches océanographiques
Résumé On déduit du théorème de circulation d'après V. Bjerknes une nouvelle formule (voir page 17, (6)) permettant le calcul pratique des courants océaniques. Cette nouvelle formule est supérieure à celle présentée par B. Helland-Hansen et J. W. Sandström. La portée de validité de la formule antérieure se laisse dériver de la nouvelle formule lorsqu'on connaÎt l'ordre de magnitude du cisaillement horizontal et celui des divergences.相似文献
109.
With this petrographic re-investigation of the beerbachite (Chelius, 1892) from Odenwald/Germany geochemical and phase-petrological data are given for the first time.By petrofabric relics (Fig. 7) and geochemical characteristics (Figs. 8–11) is shown that the beerbachite-xenoliths are due to blocks broken down from the surrounding amphibolite series. They are present high grade hornfelses.Beerbachite, porphyroblastic by plagioclase (here porphyroblastic beerbachite, Bbp) (Chelius' Gabbroporphyrit) (Fig. 6) frequently forms marginal zones of beerbachite blocks and is explained as beerbachite-metablastite.Phase relation (Fig. 13) and mineral reactions with increasing metamorphic grade from amphibolite to amphibolite-hornfels (containing hornblende) finally to beerbachite are demonstrated and discussed.The first step may be the mineral reaction: plagI(An 35–40)+hblI+sphene= plagII(An 50–60)+hblII+cpx+opx+magnetite/ilmenite+H2O. The pyroxene-hornfels facies respectively the orthopyroxene subfacies of the K-feldspar-cordierite-hornfels facies (Winkler, 1967) is only reached with the typical assemblage: plag(An 55–70)-cpx-opx-mt/ilm±(quartz) of beerbachite.On condition that the load correspondends to 3–4 km the maximum temperatures may not have exceeded 720–750° C. This valuation would result from experimental data of Choudhuri and Winkler (1967) of the model reaction: hbl=en+di+an+H2O, if
. The natural conditions will differ from this experimental model because of
resp. P
load (p. 81)The very probably required temperature for the mineral assemblage of beerbachite would still be within sub-solidus temperatures of the corresponding model system, according to Fig. 13d. Therefore, the coarse grained plagioclases of Bbp (p. 69) could not be formed from cotectic pockets, too.Finally, convergences and divergences to the beerbachite concept are discussed out of the recent literature.
Herrn Dr. E. Knauer vom hiesigen Institut danken wir sehr für die Bestimmung des Chemismus zweier Pyroxen-Paare aus Beerbachit bzw. Hornfels mit der Mikrosonde (CAMEGA MS 46), Leihgabe der Deutschen Forschungsgemeinschaft. Den Herren Prof. E. Nickel und Dr. M. Maggetti vom Mineralogischen Institut der Universität Fribourg (Schweiz) und Dr. H. D. Trochim, Mineralogisches Institut der Universität Bochum, verdanken wir Vergleichsproben oder Einsichtnahme in vorhandene Dünnschliffe. 相似文献
Herrn Dr. E. Knauer vom hiesigen Institut danken wir sehr für die Bestimmung des Chemismus zweier Pyroxen-Paare aus Beerbachit bzw. Hornfels mit der Mikrosonde (CAMEGA MS 46), Leihgabe der Deutschen Forschungsgemeinschaft. Den Herren Prof. E. Nickel und Dr. M. Maggetti vom Mineralogischen Institut der Universität Fribourg (Schweiz) und Dr. H. D. Trochim, Mineralogisches Institut der Universität Bochum, verdanken wir Vergleichsproben oder Einsichtnahme in vorhandene Dünnschliffe. 相似文献
110.
Wolfgang Schubert 《Contributions to Mineralogy and Petrology》1969,21(4):295-310
Ultrabasic metamorphic rocks with typical mineral assemblage of cummingtonitic hornblende+Mg-chlorite+talc (described byMatthes u.Okrusch, 1965, and called “hösbachit”) were found for the first time in Odenwald/Germany. Three steps of metamorphic development can be described: the primary magmatic ultrabasic rock consisted of (1) orthopyroxene (bronzite), clinopyroxene (diallage), poikilitic olivine, and some hornblende. This is indicated by textural relicts, structural and geochemical investigations. A regional metamorphic process under conditions of the staurolite-almandine-subfacies ofWinkler’s andTurner andVerhoogen’s almandine-amphibolite facies transformed this assemblage to (2): cummingtonitic hornblende I+Mg-chlorite I (clinochlore)+talc. The third step followed under more diaphthoritic conditions and brought mineral assemblage (3): tremolitic hornblende II+Mg-chlorite II (pennine)+talc. 相似文献