全文获取类型
收费全文 | 334篇 |
免费 | 26篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 42篇 |
地球物理 | 74篇 |
地质学 | 149篇 |
海洋学 | 14篇 |
天文学 | 68篇 |
综合类 | 3篇 |
自然地理 | 15篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 19篇 |
2016年 | 19篇 |
2015年 | 17篇 |
2014年 | 19篇 |
2013年 | 20篇 |
2012年 | 23篇 |
2011年 | 23篇 |
2010年 | 21篇 |
2009年 | 21篇 |
2008年 | 24篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 15篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有370条查询结果,搜索用时 31 毫秒
271.
Abstract The Southern Uralides are a collisional orogen generated in the Late Devonian–Early Carboniferous by the collision of the Magnitogorsk island arc (MA) generated in the Early to Middle Devonian by intra‐oceanic convergence opposite to the continental margin, and the continental margin of the East European craton. A suture zone of the arc to the continental margin, the Main Uralian Fault (MUF), is marked by ophiolites and exhumed high‐pressure–low‐temperature metamorphic rocks of continental origin. The pre‐orogenic events of the Southern Urals and their geodynamic setting are traced by means of fluid‐immobile incompatible trace elements (rare earth elements and high field strength elements) and Sr–Nd–Pb isotope geochemistry of the MA suites, in particular the protoarc suite with boninites and probably ankaramites, and the mature arc comprised of island arc tholeiitic (IAT) suites, transitional IAT to calc‐alkaline (CA), and CA suites. The MA volcanics result in genetically distinct magmatic source components. In particular, depleted normal‐mid‐oceanic ridge basalt‐type mantle sources with various enrichments in a slab‐derived aqueous fluid component are evident. The enriched component is not involved in significant amounts, as testified by the rather radiogenic Nd isotopes and unradiogenic Pb isotopes. Further information on the pre‐orogenic events is provided by the Mindyak Massif metagabbros derived from diverse gabbroic protoliths that were affected by oceanic rodingitization, and subsequently by a high‐temperature (HT) metamorphism related to the development of a metamorphic sole. The HT metamorphism has the same age as the protoarc volcanism, and constrains the initiation of subduction at approximately 410 Ma. Consequently, the maximum timespan between initial intra‐oceanic convergence and final collision is approximately 31 my, a duration consistent with that of present‐day ongoing collisions in the western Pacific. The characteristics of early volcanism and the traces of a metamorphic sole provide useful criteria to attribute most MUF ophiolites to the Tethyan type with a complex pre‐orogenic evolution. 相似文献
272.
Lead isotope variations across terrane boundaries of the Tien Shan and Chinese Altay 总被引:1,自引:0,他引:1
Massimo Chiaradia Dmitry Konopelko Reimar Seltmann Robert A. Cliff 《Mineralium Deposita》2006,41(5):411-428
The Altaid orogen was formed by aggregation of Paleozoic subduction–accretion complexes and Precambrian basement blocks between the Late Proterozoic and the Early Mesozoic. Because the Altaids are the site of abundant granitic plutonism and host some of the largest gold deposits in the world, understanding their formation has important implications on the comprehension of Phanerozoic crustal growth and metallogeny. In this study, we present the first extensive lead isotope data on magmatic and metasedimentary rocks as well as ore deposits of the southern part of the Altaids, including the Tien Shan (Tianshan) and southern Altay (Altai) orogenic belts. Our results show that each terrane investigated within the Tien Shan and southern Altay is characterized by a distinct Pb isotope signature and that there is a SW–NE Pb isotope gradient suggesting a progressive transition from a continental crust environment in the West (the Kyzylkum and Kokshaal segments of the Southern Tien Shan) to an almost 100% juvenile (MORB-type mantle-derived) crust environment in the East (Altay). The Pb isotope signatures of the studied ore deposits follow closely those of magmatic and metasedimentary rocks of the host terranes, thus supporting the validity of lead isotopes to discriminate terranes. Whereas this apparently suggests that no unique reservoir has been responsible for the huge gold concentration in this region, masking of a preferential Pb-poor Au-bearing reservoir by mixing with Pb-rich crustal reservoirs during the mineralizing events cannot be excluded. 相似文献
273.
274.
After the major 1991–1993 eruption, Mt. Etna resumed flank activity in July 2001 through a complex system of eruptive fissures
cutting the NE and the S flanks of the volcano and feeding effusive activity, fire fountains, Strombolian and minor phreatomagmatic
explosions. Throughout the eruption, magmas with different petrography and composition were erupted. The vents higher than
2,600 m a.s.l. (hereafter Upper vents, UV) erupted porphyritic, plagioclase-rich trachybasalt, typical of present-day summit
and flank activity. Differently, the vents located at 2,550 and 2,100 m a.s.l. (hereafter Lower vents, LV) produced slightly
more primitive trachybasalt dominated by large clinopyroxene, olivine and uncommon minerals for Etna such as amphibole, apatite
and orthopyroxene and containing siliceous and cognate xenoliths. Petrologic investigations carried out on samples collected
throughout the eruption provided insights into one of the most intriguing aspects of the 2001 activity, namely the coeval
occurrence of distinct magmas. We interpret this evidence as the result of a complex plumbing system. It consists in two separate
magma storage systems: a shallow one feeding the activity of the UV and a deeper and more complex storage related to the activity
of LV. In this deep storage zone, which is thermally and compositionally zoned, the favourable conditions allow the crystallization
of amphibole and the occurrence of cognate xenoliths representing wall cumulates. Throughout 2001 eruption, UV and LV magmas
remain clearly distinct and ascended following different paths, ruling out the occurrence of mixing processes between them.
Furthermore, integrating the 2001 eruption in the framework of summit activity occurring since 1995, we propose that the 2001
magma feeding the vents lower than 2,600 m a.s.l. is a precursor of a refilling event, which reached its peak during the 2002–2003
Etna flank eruption. 相似文献
275.
276.
Massimo Civita Adriano Fiorucci Roberta Miè 《Geostandards and Geoanalytical Research》2001,25(2-3):431-439
Aluminium was determined in surface and ground waters in the Alba region of NW Italy to provide information on natural and anthropogenic sources of contamination. Determinations were made by a spectrophotometric method based on the aluminium-pyrocatechol complex. The total aluminium content of waters was determined as well as the toxic form of monomeric aluminium, obtained from samples that had been passed through 0.20 μm cellulose filters to remove colloidal and particulate material. Results were correlated with mortality data associated with Alzheimer's disease. There appeared to be a correlation between mortality data and areas having the highest aluminium content of water. 相似文献
277.
Giuseppe Capaldi Massimo Cortini Raimondo Pece 《Journal of Volcanology and Geothermal Research》1985,26(3-4)
Hemond and Condomines (1985) claim that our results on zero age volcanic materials of Vesuvius and Etna are incorrect, that no disequilibrium exists in those materials and that the validity of the 230Th-238U dating method is thus confirmed. We show that other researchers obtained similar results in zero age rocks. The validity of the 230Th-238U dating method is simply ruled out by a comparison of the ages obtained by this method with those obtained on the same samples by different methods. 相似文献
278.
A conceptual and numerical model for groundwater management: a case study on a coastal aquifer in southern Tuscany, Italy 总被引:5,自引:3,他引:2
Piero Barazzuoli Monica Nocchi Roberto Rigati Massimo Salleolini 《Hydrogeology Journal》2008,16(8):1557-1576
Ongoing hydrogeological research aims to develop a correct management model for the Plio-Pleistocene multi-aquifer system of the Albegna River coastal plain (southern Tuscany, Italy); overexploitation of this aquifer for irrigation and tourism has caused seawater intrusion. The conceptual model is based on field and laboratory data collected during the 1995–2003 period. Meteoric infiltration and flows from the adjoining carbonate aquifer recharge the aquifer. Natural outflow occurs through a diffuse flow into the sea and river; artificial outflow occurs through intensive extraction of groundwater from wells. Water exchanges in the aquifer occur naturally (leakage, closing of aquitard) and artificially (multiscreened wells). The aquifer was represented by a three-dimensional finite element model using the FEFLOW numerical code. The model was calibrated for steady-state and transient conditions by matching computed and measured piezometric levels (February 1995–February 1996). The model helped establish that seawater intrusion is essentially due to withdrawals near the coast during the irrigation season and that it occurs above all in the Osa-Albegna sector, as well as along the river that at times feeds the aquifer. The effects of hypothetical aquifer exploitation were assessed in terms of water budget and hydraulic head evolution. 相似文献
279.
Tectono‐sedimentary evolution of the northern Iranian Plateau: insights from middle–late Miocene foreland‐basin deposits
下载免费PDF全文
![点击此处可从《Basin Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Paolo Ballato Francesca Cifelli Ghasem Heidarzadeh Mohammad R. Ghassemi Andrew D. Wickert Jamshid Hassanzadeh Guillaume Dupont‐Nivet Philipp Balling Masafumi Sudo Gerold Zeilinger Axel K. Schmitt Massimo Mattei Manfred R. Strecker 《Basin Research》2017,29(4):417-446
Sedimentary basins in the interior of orogenic plateaus can provide unique insights into the early history of plateau evolution and related geodynamic processes. The northern sectors of the Iranian Plateau of the Arabia–Eurasia collision zone offer the unique possibility to study middle–late Miocene terrestrial clastic and volcaniclastic sediments that allow assessing the nascent stages of collisional plateau formation. In particular, these sedimentary archives allow investigating several debated and poorly understood issues associated with the long‐term evolution of the Iranian Plateau, including the regional spatio‐temporal characteristics of sedimentation and deformation and the mechanisms of plateau growth. We document that middle–late Miocene crustal shortening and thickening processes led to the growth of a basement‐cored range (Takab Range Complex) in the interior of the plateau. This triggered the development of a foreland‐basin (Great Pari Basin) to the east between 16.5 and 10.7 Ma. By 10.7 Ma, a fast progradation of conglomerates over the foreland strata occurred, most likely during a decrease in flexural subsidence triggered by rock uplift along an intraforeland basement‐cored range (Mahneshan Range Complex). This was in turn followed by the final incorporation of the foreland deposits into the orogenic system and ensuing compartmentalization of the formerly contiguous foreland into several intermontane basins. Overall, our data suggest that shortening and thickening processes led to the outward and vertical growth of the northern sectors of the Iranian Plateau starting from the middle Miocene. This implies that mantle‐flow processes may have had a limited contribution toward building the Iranian Plateau in NW Iran. 相似文献
280.