全文获取类型
收费全文 | 2594篇 |
免费 | 450篇 |
国内免费 | 910篇 |
专业分类
测绘学 | 21篇 |
地球物理 | 304篇 |
地质学 | 3165篇 |
海洋学 | 186篇 |
天文学 | 12篇 |
综合类 | 125篇 |
自然地理 | 141篇 |
出版年
2024年 | 14篇 |
2023年 | 41篇 |
2022年 | 77篇 |
2021年 | 76篇 |
2020年 | 111篇 |
2019年 | 131篇 |
2018年 | 89篇 |
2017年 | 118篇 |
2016年 | 90篇 |
2015年 | 119篇 |
2014年 | 142篇 |
2013年 | 171篇 |
2012年 | 159篇 |
2011年 | 146篇 |
2010年 | 113篇 |
2009年 | 159篇 |
2008年 | 182篇 |
2007年 | 171篇 |
2006年 | 150篇 |
2005年 | 173篇 |
2004年 | 183篇 |
2003年 | 139篇 |
2002年 | 115篇 |
2001年 | 132篇 |
2000年 | 111篇 |
1999年 | 115篇 |
1998年 | 93篇 |
1997年 | 112篇 |
1996年 | 72篇 |
1995年 | 83篇 |
1994年 | 76篇 |
1993年 | 68篇 |
1992年 | 56篇 |
1991年 | 47篇 |
1990年 | 19篇 |
1989年 | 26篇 |
1988年 | 25篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有3954条查询结果,搜索用时 359 毫秒
971.
972.
973.
Stratigraphic position of the Oligocene-Miocene (Paleogene-Neogene) boundary in the northern Caucasus and, in this connection, of the Alkun Formation and the Caucasian regional stage in geological sections of Maikop deposits, primarily in those of the Belaya and Kuban rivers, is considered. Arguments in support of the Caucasian regional stage are presented and necessity of distinguishing the Karadzhalganian regional stage is called in question. Stratigraphic implications of the Alkun Formation, the regional reference horizon traceable in many sections of the northern Caucasus, are discussed. It is substantiated based on nannoplankton, dinocysts, foraminifers, and distinctive lithological features of deposits that the Oligocene-Miocene boundary is confined to the Alkun Formation at the Belaya River. 相似文献
974.
975.
Fernando Tornos Carmen Galindo César Casquet Luis Rodríguez Pevida César Martínez Enrique Martínez Francisco Velasco Alexander Iriondo 《Mineralium Deposita》2006,41(8):737-769
The Aguablanca Ni–(Cu) sulfide deposit is hosted by a breccia pipe within a gabbro–diorite pluton. The deposit probably formed due to the disruption of a partially crystallized layered mafic complex at about 12–19 km depth and the subsequent emplacement of melts and breccias at shallow levels (<2 km). The ore-hosting breccias are interpreted as fragments of an ultramafic cumulate, which were transported to the near surface along with a molten sulfide melt. Phlogopite Ar–Ar ages are 341–332 Ma in the breccia pipe, and 338–334 Ma in the layered mafic complex, and are similar to recently reported U–Pb ages of the host Aguablanca Stock and other nearby calc-alkaline metaluminous intrusions (ca. 350–330 Ma). Ore deposition resulted from the combination of two critical factors, the emplacement of a layered mafic complex deep in the continental crust and the development of small dilational structures along transcrustal strike-slip faults that triggered the forceful intrusion of magmas to shallow levels. The emplacement of basaltic magmas in the lower middle crust was accompanied by major interaction with the host rocks, immiscibility of a sulfide melt, and the formation of a magma chamber with ultramafic cumulates and sulfide melt at the bottom and a vertically zoned mafic to intermediate magmas above. Dismembered bodies of mafic/ultramafic rocks thought to be parts of the complex crop out about 50 km southwest of the deposit in a tectonically uplifted block (Cortegana Igneous Complex, Aracena Massif). Reactivation of Variscan structures that merged at the depth of the mafic complex led to sequential extraction of melts, cumulates, and sulfide magma. Lithogeochemistry and Sr and Nd isotope data of the Aguablanca Stock reflect the mixing from two distinct reservoirs, i.e., an evolved siliciclastic middle-upper continental crust and a primitive tholeiitic melt. Crustal contamination in the deep magma chamber was so intense that orthopyroxene replaced olivine as the main mineral phase controlling the early fractional crystallization of the melt. Geochemical evidence includes enrichment in SiO2 and incompatible elements, and Sr and Nd isotope compositions (87Sr/86Sri 0.708–0.710; 143Nd/144Ndi 0.512–0.513). However, rocks of the Cortegana Igneous Complex have low initial 87Sr/86Sr and high initial 143Nd/144Nd values suggesting contamination by lower crustal rocks. Comparison of the geochemical and geological features of igneous rocks in the Aguablanca deposit and the Cortegana Igneous Complex indicates that, although probably part of the same magmatic system, they are rather different and the rocks of the Cortegana Igneous Complex were not the direct source of the Aguablanca deposit. Crust–magma interaction was a complex process, and the generation of orebodies was controlled by local but highly variable factors. The model for the formation of the Aguablanca deposit presented in this study implies that dense sulfide melts can effectively travel long distances through the continental crust and that dilational zones within compressional belts can effectively focus such melt transport into shallow environments.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
976.
977.
Data supporting relevant Late Cretaceous–Early Eocene sinistral displacement along the Giudicarie fault zone and a minor Neogene dextral displacement along the Periadriatic lineament are discussed. The pre-Adamello structural belt is present only in the internal Lombardy zone, located W of the Adamello massif. This belt is unknown in the Dolomites and surrounding areas located to the E of the Giudicarie lineament. Upper Cretaceous–Early Eocene thick syntectonic Flysch deposits of Lombardy and Giudicarie are well preserved along the southern and eastern border of the pre-Adamello belt (S-vergent Alpine orogen). Towards the E, in the Dolomites and in the Carnic Alps and external Dinarides, only incomplete remnants of Flysch deposits, Aptian–Albian and Turonian–Maastrichtian in age, are present. They can be considered as equivalent to those of Lombardy and Giudicarie formerly in connection to each other along the N-Giudicarie corridor. To the S, the syntectonic Flysch deposits are laterally replaced by the calcareous red pelagites of the Scaglia Rossa and by the carbonate shelf deposits of the Friuli (to the E) and Bagnolo (to the S) carbonate platforms. The different location in the southern structural accretion of the eastern and western opposite blocks (the Dolomites versus the pre-Adamello belt) can be related to the Cretaceous–Eocene convergence. In this frame, the N-Giudicarie fault has been considered as part of a former transfer zone, which produced the sinistral lateral displacement of the Southern Alps front for an amount of some 50 km. During the Late Eocene to Early Oligocene the transfer zone was mostly sealed by the Paleogene Adamello batholith. Oligocene to Neogene compressional evolution inverted the N-Giudicarie fault into a backthrust of the Austroalpine units over the South-Alpine chain. 相似文献
978.
Earthquake-induced deformation structures in lake deposits: A Late Pleistocene to Holocene paleoseismic record for Central Switzerland 总被引:1,自引:0,他引:1
979.
Lithospheric controls on the formation of provinces hosting giant orogenic gold deposits 总被引:10,自引:0,他引:10
Frank P. Bierlein David I. Groves Richard J. Goldfarb Benoit Dubé 《Mineralium Deposita》2006,40(8):874-886
Ages of giant gold systems (>500 t gold) cluster within well-defined periods of lithospheric growth at continental margins, and it is the orogen-scale processes during these mainly Late Archaean, Palaeoproterozoic and Phanerozoic times that ultimately determine gold endowment of a province in an orogen. A critical factor for giant orogenic gold provinces appears to be thickness of the subcontinental lithospheric mantle (SCLM) beneath a province at the time of gold mineralisation, as giant gold deposits are much more likely to develop in orogens with subducted oceanic or thin continental lithosphere. A proxy for the latter is a short pre-mineralisation crustal history such that thick SCLM was not developed before gold deposition. In constrast, orogens with protracted pre-mineralisation crustal histories are more likely to be characterised by a thick SCLM that is difficult to delaminate, and hence, such provinces will normally be poorly endowed. The nature of the lithosphere also influences the intrinsic gold concentrations of potential source rocks, with back-arc basalts, transitional basalts and basanites enriched in gold relative to other rock sequences. Thus, segments of orogens with thin lithosphere may enjoy the conjunction of giant-scale fluid flux through gold-enriched sequences. Although the nature of the lithosphere plays the crucial role in dictating which orogenic gold provinces will contain one or more giant deposits, the precise siting of those giants depends on the critical conjunction of a number of province-scale factors. Such features control plumbing systems, traps and seals in tectonically and lithospherically suitable terranes within orogens. 相似文献
980.
札达盆地位于西藏西南边陲,构造上处于喜马拉雅断块挠起带头部内侧,呈NW-SE走向,长约1000km,宽约70km,总面积约40000km2,海拔约4500m.盆地中地层呈明显的二元结构特征.基底岩石为三叠纪-侏罗纪灰岩、砂岩和板岩,盖层为上新世-早更新世早期沉积的固结和半固结岩石,因受喜马拉雅断块挠起运动的影响,形成NW、NE和近EW、SN向等多组节理裂隙.晚新生代以来,盆地上升,在构造节理的主导下,穿越盆地的象泉河及其支流对岩石地层进行侵蚀、切割,在雨水的淋蚀、寒冻风化的剥蚀作用下,逐渐形成现今大小不同和形态奇特的半固结砂泥岩塔林地貌景观-古格地貌,这是中国地质地貌景观的一种新类型. 相似文献