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31.
The Hammam Lif coast (North-East of Tunisia) suffered from erosion mainly after the storm that damaged the zone in 1981. To protect it, eight shore-parallel breakwaters were built. The present study is interested in presenting the effect of the protection works on the coastline behavior by using aerial photographs geo-referenced by the digital photogrammetric method and empirical relationships. The successive breakwaters made a general accretion with formation of seven tombolos and salient. The response of the coast to these structures was related to the characteristics of these latter (length, distance to coast, and spacing). The effectiveness of such protection works is shown by the evaluation of the accretion areas formed behind them. The breakwaters which are the longest, less distant from the shoreline, and less spaced formed well-developed tombolos. Whereas, the structures which are short, very far from the coastline, and far from each other caused very small tombolos and even a salient. 相似文献
32.
Kais Aridhi Sabri Aridhi Mohamed Abdoullah Ould Bagga Saâdi Abdeljaouad Fouad Zargouni Eric Mercier 《Arabian Journal of Geosciences》2013,6(5):1591-1599
The imbrication’s area in northern Tunisia is the most external segment of Alpine range, where several associated folds types with thrust ramps are recognized within imbricate units beneath Numidian front slope. Their presence help to understand thrusting mechanisms installation through studied area. In fact, this zone was considered as a result of Paleogene gravitary slop (Kujawski (Ann Miner Géol Tunis (24):281, 1969); Caire (Ann Min Géol Tunis 26:87–110, 1973); Rouvier 1977), which is proved to be affected by major deep decollement, given rise to various structures, some are propagation folds, specific of foreland front, limited to this area, and those in more external position: Tunisian Atlas (Creusot et al. (C R Acad Sci Paris 314(Sér II):961–965, 1992); Ouali and Mercier (PII: S0191-8141(97):00048-5, 1997); Ouali 1984; Ahmadi et al. (J Struct Geol 28:721–728, 2006)). Various categories of fold ramps could be identified: frontal folds ramp NE–SW and others as lateral or oblique ramp with NW–SE trend (Aridhi et al. (C R Geosci 343:360–369, 2011)). The relation between various structures has been used as recognition tools of thrusting sequences and to propose a new deformation chronology. Delimited outcropping of these structures between two both parallel faults strikes with regional displacement, leads to interpret these faults as cogenetic tear faults of propagation thrusts; this fault separates two domains with different deformation styles from each other side. 相似文献
33.
Dorra Mahdi Randa Ben Abdallah Nouri Hatira Ali Tlili Hédi Ridha Chaftar Fakher Jamoussi 《Arabian Journal of Geosciences》2013,6(11):4347-4355
The Oued Belif 48 and Koudiat El Halfa 5 borehole samples have been analysed in order to reveal the mineralogical composition of the Triassic successions and their burial history within the geological evolution of the Tethysian southern margin. Oued Belif 48 borehole belongs to Nefza district which is a part of the “Nappe zone” (Tellian unit, north-western Tunisia). Koudiat El Halfa 5 borehole crosses the Koudiat El Halfa diapir (north–west of the north–south axis, Central Atlas). In this paper, the burial degree of evaporitic Triassic samples was determined by the “illite crystallinity” index and by the evolution of the other phyllosilicates, essentially chlorite, talc and illite/chlorite and illite/smectite mixed layers. The studied samples of the two boreholes are characterized by the presence of abundant clay minerals. The <2-μm grain-size fraction of the samples is mostly composed of illite, chlorite and smectite and may contain a slight percentage of swelling layers (illite/smectite and illite/chlorite). The illite crystallinity value measured on ethylene glycol solvated oriented mounts of the Oued Belif 48 samples oscillates globally between 1 and 2.5 characterizing the epizonal zone with a range of 300–400 °C temperatures. The measures of Koudiat El Halfa 5 samples crystallinity index show a value ranging from 2 to 4, which indicates the anchizone and early epizone burial stage (temperatures around 200 °C). These data can be explained by Miocene magmatic activities characterizing the Triassic material of Nefza district and also by burial phenomena effects. 相似文献
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Fossi MC Borsani JF Di Mento R Marsili L Casini S Neri G Mori G Ancora S Leonzio C Minutoli R Notarbartolo di Sciara G 《Marine environmental research》2002,54(3-5):761-767
The aim of this study was to propose a suite of biomarkers (BPMO activity, NADPH-cytocrome c reductase, NADH-ferricyanide reductase. esterases, porphyrins, vitellogenin and zona radiata proteins) and residue levels (organochlorines, PAHs and heavy metals) in the zooplanktonic euphausiid Meganyctiphanes norvegica as a potential multi-disciplinary diagnostic tool for assessment of the health status of the Mediterranean "whale sanctuary". Very little difference in BPMO was detected between sites, with values ranging from 0.75 to 2.68 U.A.F./mg prot/h. On the other hand larger differences between sites were found for reductase activities. Esterases (AChE), porphyrins (Copro-, Uro-, Proto-porphyrins) vitellogenin and zona radiata proteins were also detectable in this zooplanctonic species. Hg showed mean levels of 0.141 ppm d.w., Cd 0.119 ppm d.w. and Pb 0.496 ppm d.w. Total PAHs ranged from 860.7 to 5,037.9 ng/g d.w., carcinogenic PAHs from 40.3 to 141.7 ng/g d.w., HCB from 3.5 to 11.6 ng/g d.w., DDTs from 45.3 to 163.2 ng/g d.w. and the PCBs from 84.6 to 210.2 ng/g d.w. 相似文献
37.
Sergio Rocchi Alfredo Mazzotti Michele Marroni Luca Pandolfi Paolo Costantini Bertozzi Giuseppe Davide di Biase Francesco Federici Papa Goumbo L 《地学学报》2007,19(4):232-239
The Atlantic margin offshore Senegal has been explored by seismic reflection and GRAV‐MAG surveys. High‐amplitude, laterally transgressive seismic reflectors are found to coincide with gravimetric and magnetic highs. Once seismic data are integrated with potential fields modelling, these reflectors can be safely interpreted as saucer‐shaped igneous sills, up to some hundreds of metres thick, some km wide. The occurrence of hydrothermal vent complexes and forced folds in the stratigraphic sequence above the sills constrain the intrusion age to the Miocene. Field observations and in‐situ magnetic susceptibility measurements of Oligocene–Miocene and Quaternary igneous rocks emplaced in coastal Senegal support this interpretation. 相似文献
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辽宁五龙金矿黄铁矿的热电性标型特征 总被引:2,自引:0,他引:2
黄铁矿是五龙金矿的主要载金矿物之一,热电性以P型为主,占总数的90.8%,变化范围为4.3-392.0uV/℃,N型占9.2%,变化范围为-28.6--177.1uV/℃;不同世代黄铁矿热电性不同,第一世代为P型,第二、三世代为P、N混合型;横向上从矿体到围岩;热电系数由小变大,As使其呈P型,而C0、Ni使其呈N型。 相似文献
40.
毒砂是老柞山金矿主要载金矿物。早期与晚期成矿作用形成的毒砂 ,其热电性具明显差异 :早期毒砂热电系数为正值 ,平均 2 5 0 .3μV /℃ ,P型导电 ;晚期毒砂热电系数为负值 ,平均- 2 16 .9μV /℃ ,为N型导电。通过对不同成矿期以及同一样品中不同导型毒砂的热电性特征与成分关系的研究得出 :毒砂的热电性特征由As、S相对含量决定 ,若为富As型毒砂 ,则为P型导电 ,若为富S型毒砂 ,则为N型导电。 相似文献