全文获取类型
收费全文 | 134篇 |
免费 | 5篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 3篇 |
地球物理 | 49篇 |
地质学 | 42篇 |
海洋学 | 19篇 |
天文学 | 21篇 |
综合类 | 3篇 |
自然地理 | 7篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 3篇 |
2011年 | 8篇 |
2010年 | 2篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 12篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有145条查询结果,搜索用时 18 毫秒
71.
Hossein Azizi Sepideh Hadad Robert J. Stern Yoshihiro Asahara 《International Geology Review》2019,61(2):195-223
The Baneh plutonic complex is situated in the Zagros suture zone of northwest Iran between the Arabian and Eurasian plates. This complex is divided into granite and appinite groups. Zircon U–Pb dating shows that granites crystallized 41–38 million years ago but appinites experience more protracted magmatic evolution, from at 52 to 38 Ma. Whole-rock chemical compositions show significant major and trace element variations between the two lithologies. Granitic rocks are more evolved, with high contents of SiO2 (62.4–77.0 wt%), low contents of TiO2 (0.25 wt%), MgO (0.05–1.57 wt%), and Fe2O3 (0.40–4.06 wt%) and high contents of Na2O + K2O (≈10 wt%). In contrast, appinites have low contents of SiO2 (51.0–57.0 wt%) and K2O (<2.1 wt%) and high Fe2O3 (6.4–9.35 wt%), MgO (2.0–9.9 wt%), and Mg number (Mg# = 35–76). The concentration of rare earth elements in the appinites is higher than in granitic rocks, making it difficult to form granites solely by fractionation of appinite magma. (87Sr/86Sr)i and εNd(40 Ma) in both groups are similar, from 0.7045 to 0.7061 and ?1.2 to +2.6, except for a primitive gabbroic dike with εNd(40 Ma) = +9.9. Appinites show mainly typical I-type characteristics, but granites have some S-type characteristics. The sigmoidal shape of the Baneh pluton and its emplacement into deformed Cretaceous shales and limestone showing kink bands, asymmetric and recumbent folds in a broad contact zone, with pervasive ductile to brittle structures in both host rocks and intrusion, indicate that magma emplacement was controlled by a transpressional tectonic regime, perhaps developed during early stages in the collision of Arabia and Eurasian plates. 相似文献
72.
73.
Hossein Azizi Fatemeh Nouri Robert J. Stern Marie Azizi Federico Lucci Yoshihiro Asahara 《International Geology Review》2020,62(13-14):1635-1657
ABSTRACT We address the growing controversy about the tectonic setting in which Jurassic magmatism of Iran occurred: arc or continental rift. In the Ghorveh area of the northern Sanandaj Sirjan zone (SaSZ), the Ghalayan metabasites are interlayered with marble and schist and locally cut by acidic dikes. Zircon U-Pb dating of the metabasitic rocks shows that these crystallized at ca. 145–144 Ma ago in the Late Jurassic (Tithonian). This complex was metamorphosed in the lower greenschist facies, however, some protolithic structures such as pillow lava and primary minerals are preserved. The metabasites are tholeiites with low SiO2 (45.6–50.5 wt.%), moderate Al2O3 (11.3–17.0 wt.%), and high TiO2 (0.7–2.9 wt.%) and Fe2O3 (9.4–14.1 wt.%). The Ghalayan metabasites are enriched in Light rare earth elements (LREEs) without significant Nb, Ta, Pb, Sr and Ba anomalies, similar to modern continental intra-plate tholeiitic basalts such as Afar and East African rifts. The Ghalaylan metabasites show wide ranges for 87Sr/86Sr(i) (0.7039–0.7077) and positive εNd(t) values (+0.1 to +4.6). These isotopic compositions are similar to those expected for slightly depleted subcontinental lithospheric mantle sources. Independently built discrimination diagrams indicate an intra-continental rifting regime for the source of Jurassic metabasites in the northern SaSZ. Geochemical and tectonic evidence suggests that rifting or a mantle plume was responsible for volcanic activity in the Upper Jurassic SaSZ. Considering the variation of ages of basaltic volcanism along the SaSZ, we suggest that Ghalayan basaltic magmatism reflected a submarine volcano that formed as part of the late stage continental rift, similar to Afar in the East African Rift system. Our results indicate that an extensional tectonic regime dominated SaSZ tectonics in the Middle to Late Jurassic. 相似文献
74.
Fatemeh Sarjoughian Somayeh Javadi Hossein Azizi Wenli Ling Yoshihiro Asahara David Lentz 《International Geology Review》2020,62(13-14):1769-1795
ABSTRACT Soheyle-Pakuh granitoid rocks, with a variety of quartz diorite, quartz monzodiorite, granodiorite, tonalite, and granite, have been emplaced into the Tertiary volcanic rocks in the Urumieh-Dokhtar magmatic arc in central Iran. Zircon U–Pb dating yields an age of 39.63 ± 0.93 Ma for the crystallization of this body. Whole-rock compositions show that SiO2 changes from 52.31 to 65.78 wt.% and Al2O3 varies from 15.54 to 18.24 wt.%, as well as high concentrations of large-ion lithophile elements (LILE, e.g. Cs, Rb, Ba, and K) and quite low contents of high field strength elements (HFSE, e.g. Nb, Ti, P), as expected in I-type arc granitoids formed in an active continental margin setting. Initial ratios of 87Sr/86Sr and 143Nd/144Nd exhibit ranges 0.7043–0.7047 and 0.51284 to 0.51287, respectively, with positive εNd(t) from +4.9 to +5.5 with a young TDM1 age (483–674 Ma); this tracer isotopic data suggesting that the SPG originated from juvenile basaltic crust derived from depleted mantle (~90%) with variable contributions from undepleted mantle and approximately 10% old lower crust, despite diverse processes (e.g. magma mixing and fractional crystallization) during their evolution and emplacement into a local extensional setting within the continental margin arc. The isotopic data are similar to those of other Phanerozoic granitoids of the Central Asian Orogenic Belt and corroborate melting of predominantly mantle-derived juvenile crustal protoliths and indicating extensive addition of new continental crust, during Cambrian-Neoproterozoic time, in the suprasubduction zone beneath the central Urumieh-Dokhtar magmatic arc. Generation of these types of granitoids favours a model whereby rollback and (or) break-off of a subducted slab with subsequent lithospheric extension triggered by mantle upwelling, heat advection, and underplating resulting in melting of the central UDMA mantle-derived juvenile lower continental crust in the Late Eocene. 相似文献
75.
76.
Yoshinobu Aramaki Takushi Yokoyama Yoshihiro Okaue Akira Imai Koichiro Watanabe 《Resource Geology》2005,55(3):281-284
Abstract. Silica scales containing large amounts of smectite were recently found in the pipelines for geothermal water at a geothermal power plant. To elucidate the mechanism of smectite formation, seven silica scale samples were characterized by powder X-ray diffraction, chemical analysis and 27 A1 MAS NMR. Smectite was present in samples with MgO levels above 10 wt% and Al2 O3 levels below 10 wt%. In 27 A1 MAS NMR spectra, peaks assigned to both tetrahedrally and octahedrally coordinated aluminum (Al(4) and Al(6)) were observed for Mg-rich samples, whereas a peak due to Al(4) alone appeared in Mg-poor samples. From these observation and comparison between 27 A1 MAS NMR spectra for synthesized precipitates of Al2 O3 -SiO2 containing MgO and not containing MgO, it is concluded that magnesium plays an important role in the stabilization of Al(6), and results in the formation of smectite 相似文献
77.
Fuji volcano is the largest active volcano in Japan, and consists of Ko-Fuji and Shin-Fuji volcanoes. Although basaltic in composition, small-volume pyroclastic flows have been repeatedly generated during the Younger stage of Shin-Fuji volcano. Deposits of those pyroclastic flows have been identified along multiple drainage valleys on the western flanks between 1,300 and 2,000 m a.s.l., and have been stratigraphically divided into the Shin-Fuji Younger pyroclastic flows (SYP) 1 to 4. Downstream debris flow deposits are found which contain abundant material derived from the pyroclastic flow deposits. The new14C ages for SYP1 to SYP4 are 3.2, 3.0, 2.9, and 2.5 ka, respectively, and correspond to a period where explosive summit eruptions generated many scoria fall deposits mostly toward the east. The SYP1 to SYP4 deposits consist of two facies: the massive facies is about 2 m thick and contains basaltic bombs of less than 50 cm in size, scoria lapilli, and fresh lithic basalt fragments supported in an ash matrix; the surge facies is represented by beds 1 to 15 cm thick, consisting mainly of ash with minor amount of fine lapilli. The bombs and scoria are 15 to 30% in volume within the massive facies. The ashes within the SYP deposits consist largely of comminuted basalt lithics and crystals that are derived from the Middle-stage lava flows exposed at the western flanks. SYP1 to SYP4 were only dispersed down the western flanks. The reason for this one-sided distribution is the asymmetric topography of the edifice; the western slopes of the volcano are the steepest (over 34 degrees). Most pyroclastic materials cannot rest stably on the slopes steeper than 33 degrees. Therefore, ejecta from the explosive summit eruptions that fell on the steep slopes tumbled down the slopes and were remobilized as high-temperature granular flows. These flows consisted of large pyroclastics and moved as granular avalanches along the valley bottom. Furthermore, the avalanching flows increased in volume by abrasion from the edifice and generated abundant ashes by the collision of clasts. The large amount of the fine material was presumably available within the transport system as the basal avalanches propagated below the angle of repose. Taking the typical kinetic friction coefficient of small pyroclastic flows, such flows could descend the western flanks where scattered houses are below 1,000 m a.s.l. A similar type of pyroclastic flow could result if explosive summit eruptions occur in the future.Editorial responsibility: R Cioni 相似文献
78.
79.
We investigate the initial rupture process of microearthquakes to reveal relationships between nucleation region sizes and eventual earthquake sizes. In order to obtain high quality waveform data, we installed a trigger recording system with a sampling frequency of 10 kHz at the base of a deep borehole at the Nojima Fault, Japan. We analyze waveform data of 31 events around the borehole, with seismic moment ranging from 4.2 × 109 Nm to 7.1 × 1011 Nm. We use both a circular crack model with an accelerating rupture velocity (SK model) [Sato, T., Kanamori, H., 1999. Beginning of earthquakes modeled with the Griffith's fracture criterion, Bull. Seism. Soc. Am., 89, 80-93.], which generates a slow initial phase of velocity pulse, and a circular crack model with a constant rupture velocity (SH model) [Sato, T, Hirasawa, T., 1973. Body wave spectra from propagating shear cracks, J. Phys. Earth, 21, 415-431.], which generates a ramp-like velocity pulse. Source parameters of these two models are estimated by waveform inversion of the first half cycle of the observed velocity pulse applying both a grid search and a non-linear least squares method. 14 of 31 events are never reproduced by the SH model with a constant Q operator. But SK model with a constant Q operator provides a size of the pre-existing crack, corresponding to the size of the nucleation regions, and a size of the eventual crack. We recognize that (i) the eventual seismic moment is approximately scaled as the cube of the size of pre-existing cracks, (ii) the eventual seismic moment is scaled as the cube of the size of eventual cracks, and (iii) the size of eventual cracks is roughly proportional to the size of pre-existing cracks. We, thus, conclude that the size of eventual earthquakes is controlled by the size of the nucleation regions. 相似文献
80.
Nitrate pollution of groundwater in the Yellow River delta,China 总被引:8,自引:0,他引:8
Jianyao Chen Makoto Taniguchi Guanqun Liu Kunihide Miyaoka Shin-ichi Onodera Tomochika Tokunaga Yoshihiro Fukushima 《Hydrogeology Journal》2007,15(8):1605-1614
Nitrate pollution of groundwater in the Yellow River delta, China is an important issue related not only to nitrate dispersion and health concerns but also to mass transport and interactions of groundwater, sea, and river waters in the coastal area. The spatial distribution of nitrate, nitrate sources, and nitrogen transformation processes were investigated by field surveys and geochemical methods. Nitrate occurred mainly in shallow layers and had a spatial distribution coinciding with geomorphology and land/water use. Irrigation water from the Yellow River and anthropogenic waste are two main nitrogen sources of nitrate in the delta, and both denitrification and mixing processes could take place according to characteristics identified by ionic and isotopic data. 相似文献