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71.
Prof. Dr. Mario Vergara 《International Journal of Earth Sciences》1983,72(3):1005-1014
Recent field studies in the Andean Cordillera of Central Chile (33–40 S. L.) have shown a widespread distribution around the Chile-Argentina border of pliopleistocene volcanic and pyroclastic flow (5-1 m. y. K/Ar). The older ages are found in Rio Blanco (Santiago) area and the younger in the Cola de Zorro area. They cover horizontal to sub-horizontally, with strong unconformity their meso-cenozoic basement.In the Rio Blanco area the most silicic rocks are dactic and rhyolitic ignimbrites and lava flows. They are similar to the Rhyolitic Formation (Zeil andPichler, 1967) of northern Chile.South of 36 S. L. most of the rocks are calcalkaline basalts and andesites except for the samples from the Pino Hachado area, which plot nearRittman's alkaline field. Chemical inhomogenety of the plio-pleistocene volcanic rocks is thus present in the Andes of Central Chile.
Zusammenfassung Neue Arbeiten über die Geologie der Cordillera de los Andes im zentralen Abschnitt Chiles (33–40 S) haben eine enorme Verbreitung von plio/pleistozänen Vulkaniten (5-1 m. a.) vor allem in der Grenzregion mit Argentinien ergeben. Die höheren Alter fand man im Gebiet von Rio Blanco (Santiago) und die jüngsten im Gebiet von Cola de Zorro.Die Vulkanite bedecken mit einer horizontalen bis subhorizontalen Verbreitung und mit einer scharfen Diskordanz alle Gesteinsserien des Mesozoikums und Känozoikums.Im Gebiet von Rio Blanco handelt es sich um Ignimbrite rhyolitischer und dacitischer Zusammensetzung. Die kieselsäurereichsten Proben sind ähnlich den Gesteinen der Rhyolit-Formation vonZeil &Pichler (1967) in Nordchile.Südlich von 36 S hat die Mehrheit der Proben eine andesitische und basaltische Zusammensetzung. Es sind kalkalkaline Gesteine mit Ausnahme der Proben von Pino Hachado, die einen starken alkalinen Trend nach dem Diagramm vonRittmann haben. Auf diese Weise ergibt sich eine chemische Inhomogenität bei den plio/pleistozänen Vulkaniten von Zentralchile.
Resumen Los más recientes trabajos de geología de campo en la Cordillera de los Andes de Chile Central (33–40 L. S.) han evidenciado enormes extensiones de rocas volcánicas pliopleistocénicas (5-1 m. a.) sobre todo en el área limítrofe con Argentina. Las mayores edades fueron encontradas en el area de Rio Blanco (Santiago) y las más jóvenes en el area de Cola de Zorro.Las rocas volcánicas plio-pleistocénicas cubren con disposición horizontal a subhorizontal y con fuerte discordancia a todas las rocas subyacentes del Meso y Cenozoico.En el area de Río Blanco las rocas son ignimbritas de composición riolítica a dacítica y corresponden a las muestras más silícicas similar a rocas de la Formación Riolítica del norte de Chile deZeil yPichler (1967).Al sur del paralelo 36 S la mayoría de las muestras son de composición andesítica y basáltica de naturaleza calcoalcalina excepto las muestras de Pino Hachado que presentan fuerte afînidad alcalina según el diagrama deRittmann. De esta manera se muestra que existe inhomogeneidad química en las rocas volcánicas plios-pleistocénicas de Chile Central.
Cordillera de los Andes (33°–40° S) , . - (), --. , , . - . 36° . - , . . . , - .相似文献
72.
François Charlet Marc De Batist Emmanuel Chapron Sébastien Bertrand Mario Pino Roberto Urrutia 《Journal of Paleolimnology》2008,39(2):163-177
Prior to the collection of a series of sediment cores, a high- and very-high-resolution reflection seismic survey was carried
out on Lago Puyehue, Lake District, South-Central Chile. The data reveal a complex bathymetry and basin structure, with three
sub-basins separated by bathymetric ridges, bedrock islands and interconnected channels. The sedimentary infill reaches a
thickness of >200 m. It can be sub-divided into five seismic-stratigraphic units, which are interpreted as: moraine, ice-contact
or outwash deposits (Unit I), glacio-lacustrine sediments rapidly deposited in a proglacial or subglacial lake at the onset
of deglaciation (Unit II), lacustrine fan deposits fed by sediment-laden meltwater streams in a proglacial lake (Unit III),
distal deposits of fluvially derived sediment in an open, post-glacial lake (Unit IV) and authigenic lacustrine sediments,
predominantly of biogenic origin, that accumulated in an open, post-glacial lake (Unit V). This facies succession is very
similar to that observed in other glacial lakes, and minor differences are attributed to an overall higher depositional energy
and higher terrigenous input caused by the strong seismic and volcanic activity in the region combined with heavy precipitation.
A long sediment core (PU-II core) penetrates part of Unit V and its base is dated as 17,915 cal. yr. BP. Extrapolation of
average sedimentation rates yields an age of ca. 24,750 cal. yr. BP for the base of Unit V, and of ca. 28,000 cal. yr. BP
for the base of Unit IV or for the onset of open-water conditions. This is in contrast with previous glacial-history reconstructions
based on terrestrial records, which date the complete deglaciation of the basin as ca. 14,600 cal. yr. BP. This discrepancy
cannot be easily explained and highlights the need for more lacustrine records from this region.
This is the second in a series of eight papers published in this special issue dedicated to the 17,900 year multi-proxy lacustrine record of
Lago Puyehue, Chilean Lake District. The papers in this special issue were collected by M. De Batist, N. Fagel, M.-F. Loutre
and E. Chapron. 相似文献
73.
74.
Mario Parise 《Environmental Earth Sciences》2016,75(23):1476
Comments are presented on the article by Abbasnejad et al. (Environ Earth Sci 75:1306, 2016) dealing with qanat and hazards in Iran. My rebuttal starts from the direct attribution of the described hazards to qanat and addresses the importance in the correct use of terminology for geological hazards. All of the problems pointed out in Iran (subsidence, sinkholes, pollution) have, to me, an anthropogenic origin and cannot be directly ascribed to qanat. Eventually, I present some additional elements to highlight the remarkable importance of qanat systems and their influence on the development of similar underground structures in many countries of the Mediterranean Basin. This remarks the relevance of qanat as cultural heritage sites and the need for their preservation and valorization. 相似文献
75.
76.
The Villeta Group of Colombia and equivalent stratigraphic units of Venezuela and Ecuador comprise marine sequences ranging from Albian to Santonian in age. Deposition of the Villeta Group was presumed to take place entirely in quiet tectonic conditions in a passive margin setting that occupied NW South America. From a large database of 2D/3D seismic, well, surface geology, and biostratigraphic data, we present evidence for intra-Villeta (mostly late Albian–Cenomanian) deformation in parts of the Upper Magdalena Valley and Eastern Cordillera of Colombia, controlled by transpressional fault reactivation, produced by transpressional fault reactivation and thrusting that resulted in an angular unconformity. This event has been largely unnoticed in the literature, but previously scattered evidence supports our observations, suggesting regionally extensive tectonism. Published fission-track age determinations and other geologic evidence from Colombia and Venezuela suggest significant uplifts around 80–100 m.y., which may reflect changes in the subduction regime, with compressional deformation in certain regions and extensional deformation in others. A late Albian onset of compressional deformation along the Colombian and Peruvian segments of the Andes may be related to the opening of the South Atlantic Ocean at equatorial latitudes. Identification of tectonic activity with development of an unconformity in intra-Villeta times provides new insights into understanding the evolution of the Upper Magdalena Valley and adjacent areas of Colombia and western Venezuela and creates new possibilities for hydrocarbon exploration, with additional trapping phases, better reservoir preservation by early migration and secondary porosity, and ultimately facies changes with stratigraphic potential. 相似文献
77.
Carmela Freda Mario Gaeta Daniel B. Karner Fabrizio Marra Paul R. Renne Jacopo Taddeucci Piergiorgio Scarlato John N. Christensen Luigi Dallai 《Bulletin of Volcanology》2006,68(6):567-591
A comprehensive volcanological study of the Albano multiple maar (Alban Hills, Italy) using (i) 40Ar/39Ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and (ii) petrographic observations,
phase analyses of major and trace elements, and Sr and O isotopic analyses of the pyroclastic deposits shows that volcanic
activity at Albano was strongly discontinuous, with a first eruptive cycle at 69±1 ka producing at least two eruptions, and
a second cycle with two peaks at 39±1 and 36±1 ka producing at least four eruptions. Contrary to previous studies, we did
not find evidence of magmatic or hydromagmatic eruptions younger than 36±1 ka. The activity of Albano was fed by a new batch
of primary magma compositionally different from that of the older activity of the Alban Hills; moreover, the REE and 87Sr/86Sr data indicate that the Albano magma originated from an enriched metasomatized mantle. According to the modeled liquid line
of descent, this magma differentiated under the influence of magma/limestone wall rock interaction. Our detailed eruptive
and petrologic reconstruction of the Albano Maar evolution substantiates the dormant state of the Alban Hills Volcanic District.
Electronic Supplementary Material Supplementary material is available for this article at
Editorial responsibility: J. Donnelly-Nolan
An erratum to this article can be found at 相似文献
78.
Elizabeth Bryan Claudia Ringler Barrack Okoba Jawoo Koo Mario Herrero Silvia Silvestri 《Climatic change》2013,118(2):151-165
Changes in the agriculture sector are essential to mitigate and adapt to climate change, meet growing food demands, and improve the livelihoods of poor smallholder producers. What agricultural strategies are needed to meet these challenges? To what extent are there synergies among these strategies? This paper examines these issues for smallholder producers in Kenya across several agroecological zones. Several practices emerge as triple wins, supporting climate adaptation, greenhouse gas mitigation, and profitability goals. In particular, integrated soil fertility management and improved livestock feeding are shown to provide multiple benefits across all agroecological zones examined. Triple wins of other agricultural practices are limited to specific agroecological zones. Irrigation and soil and water conservation, for example, are essential for adaptation, mitigation, and profitability in arid areas. The results suggest that agricultural investments targeted toward these triple-win strategies will have the greatest payoff in terms of increased resilience of farm and pastoralist households and global climate change mitigation. To reap the benefits of triple-win strategies will require that policymakers, researchers, and practitioners move away from isolated approaches focused on either adaptation or mitigation or rural income generation toward a more holistic assessment of joint strategies as well as their tradeoffs and synergies. 相似文献
79.
Elmar BUCHNER Winfried H. SCHWARZ Martin SCHMIEDER Mario TRIELOFF 《Meteoritics & planetary science》2010,45(4):662-674
Abstract– 40Ar/39Ar dating of recrystallized K‐feldspar melt particles separated from partially molten biotite granite in impact melt rocks from the approximately 24 km Nördlinger Ries crater (southern Germany) yielded a plateau age of 14.37 ± 0.30 (0.32) Ma (2σ). This new age for the Nördlinger Ries is the first age obtained from (1) monomineralic melt (2) separated from an impact‐metamorphosed target rock clast within (3) Ries melt rocks and therewith extends the extensive isotopic age data set for this long time studied impact structure. The new age goes very well with the 40Ar/39Ar step‐heating and laser probe dating results achieved from mixed‐glass samples (suevite glass and tektites) and is slightly younger than the previously obtained fission track and K/Ar and ages of about 15 Ma, as well as the K/Ar and 40Ar/39Ar age data obtained in the early 1990s. Taking all the 40Ar/39Ar age data obtained from Ries impact melt lithologies into account (data from the literature and this study), we suggest an age of 14.59 ± 0.20 Ma (2σ) as best value for the Ries impact event. 相似文献
80.
Mario Costa Giorgio Ferrara Rosalino Sacchi Sonia Tonarini 《International Journal of Earth Sciences》1992,81(2):487-500
The Proterozoic basement of the Province of Zambezia (Mozambique) is located near the southern end of the so called Mozambique Belt. Rb-Sr data derived from the analyses of 66 whole rocks and a few mineral samples bear witness of a magmatic and metamorphic episode referable to the Kibaran (ca. 1000 Ma) and helped to model the late-Proterozoic evolution as follows. At 1100–1050 Ma a pre-orogenic, calc-alkaline magmatism was responsible for the emplacement of now deformed granite and granodiorite. This phase was accompanied by rhyolitic volcanism. A subsequent peak of deformation and metamorphism occurred at 1000-950 Ma and was associated with a second generation of substantially post-tectonic granites. A thermal event resulting in the emplacement of a final generation of granites and pegmatites can be dated to around 500-450 Ma.The metamorphic basement has not preserved its protolith age, probably as a result of extensive isotopic homogeneization of Sr in Kibaran times. Its maximum time of differentiation from the mantle should be around 1600 Ma.The very low values of initial Sr isotopic ratios suggest the absence of Archean crustal precursors and support the rather young, yet pre-Pan-African evolution of the southernmost Mozambique Belt.
Zusammenfassung Das proterozoische Grundgebirge der Provinz Zambesi (Mosambique) befindet sich in der Nähe des südlichen Endes des sogenannten Mozambique Belt. Rb/Sr Daten aus 66 Ganzgesteins- und einigen Mineralanalysen zeugen von einer magmatischen und metamorphen Episode die sich dem Kibaran (ca. 1000 Ma) zuordnen läßt, und wie sich im folgenden zeigt, hilfreich bei der Modellisierung der spätproterozoischen Entwicklung ist. Um 1100 bis 1050 Ma erfolgte ein präorogener kalkalkalischer Magmatismus, bestehend aus Graniten und Granodioriten, die heute deformiert vorliegen. Diese Phase wurde von rhyolithischem Vulkanismus begleitet. Von 1000 bis 950 Ma folgte der Höhepunkt der Deformation und Metamorphose, begleitet von einer bedeutenden 2. Generation posttektonischer Granite. Bedingt durch ein weiteres thermales Ereignis intrudierte die letzte Granit- und Pegmatitgeneration vor 500 bis 450 Ma.Im metamorphen Grundgebirge ist das Eduktalter vermutlich aufgrund der starken isotopischen Homogenisierung von Sr während der Kibara-Zeit nicht erhalten. Seine maximale Differentiationszeit vom Mantel muß vor 1600 Ma gewesen sein.Die sehr niedrigen Gehalte der initialen Sr-Isotopenverhältnisse lassen die Abwesenheit von archaischen Krustenvorläufern vermuten, und unterstützen die sehr junge, bis jetzt Prä-Pan-Afrikanische Entwicklung des südlichsten Mozambique Belts.
Résumé Le socle protérozoïque de la province du Zambèze, au Mozambique, se trouve à proximité de l'extrémité sud du «Mozambique Belt». Des mesures Rb/Sr effectuées sur 66 roches totales et sur quelques minéraux témoignent d'un épisode magmatique et métamorphique attribuable au Kibarien (environ 1.000 Ma), ce qui permet de se représenter comme suit l'histoire de cette région au Protérozoïque supérieur. Il y a 1.100 à 1.050 Ma, la région a connu une phase de magmatisme calco-alcalin qui s'est traduite par la mise en place de granites et granodiorites, aujord'hui déformés. Cette phase s'est accompagnée d'un volcanisme rhyolitique. Elle a été suivie, entre 1.000 et 950 Ma, d'une activité tectono-métamorphique majeure, à laquelle est associée une deuxième et importante génération de granites, post-tectoniques. Ultérieurement, la région a connu encore un épisode thermique, daté à 500-450 Ma, responsable de la mise en place d'une dernière génération de granite et de pegmatite.Le socle métamorphique n'a pas gardé de témoins de l'âge de son protolithe, en raison probablement de la forte homogénisation isotopique du Sr à l'époque kibarienne. Lâge maximal de sa différenciation à partir du manteau doit se situer autour de 1.600 Ma.La valeur très basse des rapports isotopiques initiaux du Sr suggère l'absence de précurseurs crustaux archéens et incite à admettre une évolution relativement jeune — bien que pré-panafricaine — du «Mozambique Belt» méridional.
() .. . , Rb/Sr 66 , , Kibara, 1000 , , , . 1100 1050 - - , , . . 1000 950 , - . , 500 450 . , , , Kibara. , , 1600 my . - .相似文献