全文获取类型
收费全文 | 104篇 |
免费 | 18篇 |
国内免费 | 44篇 |
专业分类
地球物理 | 28篇 |
地质学 | 130篇 |
天文学 | 1篇 |
自然地理 | 7篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 16篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有166条查询结果,搜索用时 31 毫秒
111.
Abstract Portions of three Proterozoic tectonostratigraphic sequences are exposed in the Cimarron Mountains of New Mexico. The Cimarron River tectonic unit has affinities to a convergent margin plutonic/volcanic complex. Igneous hornblende from a quartz diorite stock records an emplacement pressure of 2–2.6 kbar. Rocks within this unit were subsequently deformed during a greenschist facies regional metamorphism at 4–5 kbar and 330 ± 50° C. The Tolby Meadow tectonic unit consists of quartzite and schist. Mineral assemblages are indicative of regional metamorphism at pressures near 4 kbar and temperatures of 520 ± 20° C. A low-angle ductile shear zone separates this succession from gneisses of the structurally underlying Eagle Nest tectonic unit. Gneissic granite yields hornblende pressures of 6–8 kbar. Pelitic gneiss records regional metamorphic conditions of 6–7 kbar and 705 ± 15° C, overprinted by retrogression at 4 kbar and 530 ± 10° C. Comparison of metamorphic and retrograde conditions indicates a P–T path dominated by decompression and cooling. The low-angle ductile shear zone represents an extensional structure which was active during metamorphism. This extension juxtaposed the Tolby Meadow and Eagle Nest units at 4 kbar and 520° C. Both units were later overprinted by folding and low-grade metamorphism, and then were emplaced against the Cimarron River tectonic unit by right-slip movement along the steeply dipping Fowler Pass shear zone. An argon isotope-correlation age obtained from igneous hornblende dates plutonism in the Cimarron River unit at 1678 Ma. Muscovite associated with the greenschist facies metamorphic overprint yields a 40 Ar/39 Ar plateau age of 1350 Ma. By contrast, rocks within the Tolby Meadow and Eagle Nest units yield significantly younger argon cooling ages. Hornblende isotope-correlation ages of 1394–1398 Ma are interpreted to date cooling during middle Proterozoic extension. Muscovite plateau ages of 1267–1257 Ma appear to date cooling from the low-grade metamorphic overprint. The latest ductile movement along the Fowler Pass shear zone post-dated these cooling ages. Argon released from muscovites of the Eagle Nest/Tolby Meadow composite unit, at low experimental temperatures, yields apparent ages of c. 1100 Ma. Similar ages are not obtained north-east of the Fowler Pass shear zone, suggesting movement more recently than 1100 Ma. 相似文献
112.
113.
M. A. Forster R. Armstrong B. Kohn G. S. Lister M. A. Cottam S. Suggate 《Australian Journal of Earth Sciences》2013,60(7):883-902
K-feldspar from the late Miocene Capoas Granite on Palawan in The Philippines appears to contain highly retentive diffusion domains that are closed to argon diffusion at near-solidus temperatures during cooling of this ~7 km-diameter pluton. This is an important result, for K-feldspar is commonly considered not retentive in terms of its ability to retain argon. Closure temperatures for argon diffusion in K-feldspars are routinely claimed to be in the range ~150–400°C but the release of 39Ar from irradiated K-feldspar during furnace step-heating experiments in vacuo yields Arrhenius data that imply the existence of highly retentive core domains, with inferred closure temperatures that can exceed ~500–700°C. These high closure temperatures from the Capoas Granite K-feldspar are consistent with the coincidence of 40Ar/39Ar ages with U–Pb zircon ages at ca 13.5 ± 0.2 Ma. The cooling rate then accelerated, but the rate of change had considerably slowed by ca 12 Ma. Low-temperature (U–Th)/He thermochronology shows that the cooling rate once again accelerated at ca 11 Ma, perhaps owing to renewed tectonic activity. 相似文献
114.
与裂变迹径定年类似,α反冲径迹定年(Alpha-Recoil Track)也是基于天然放射性元素所释放核粒子在固体中产生可蚀刻径迹的积累。铀钍及它们的子体核素进行α衰变时形成α反冲径迹,当发射一个α粒子时,重的剩余核反冲并造成30-40nm的辐射损失痕迹,经过蚀刻α反冲径迹可在干涉相差显微镜下观测。如果在样品形成以后全部迹径被保留下来,那么测定它们的总数就可以得到样品的年龄。Α反冲径迹定年是一种刚刚开始研究的新型热年代学核分析技术,研究样品可以是单个小云母片(约0.5mm),定年范围102-106a,该方法对第四纪地质、地理、灾害及考古等领域有很大的应用潜力。 相似文献
115.
藏南伸展拆离系聂拉木一带构造抬升的热年代学证据 总被引:2,自引:0,他引:2
在野外构造填图的基础上 ,采集藏南伸展拆离系 (STDS)断层面及断层下盘的糜棱岩及花岗岩进行了初步研究 ,获得糜棱岩中白云母单矿物Ar Ar坪年龄为 15 .6Ma ,磷灰石裂变径迹测年得到 9~ 11.7Ma ,MDD模式处理获得 12Ma以来的抬升速率为 5 3℃ Ma。热年代测试结果表明 ,喜马拉雅山体北侧地区在伸展作用形成后发生了快速的抬升。 相似文献
116.
青藏东缘新生代高钾岩浆活动的热年代学制约 总被引:3,自引:0,他引:3
热年代学研究表明 ,青藏东缘存在两期新生代高钾岩浆活动 ,其活动时限分别为 40~ 2 8Ma和 16~ 0Ma。两期高钾岩石在地质背景、岩石类型和地球化学特征上明显不同 ,表明早期高钾岩石是在转换压缩过程中产生的 ,起源于富集地幔的部分熔融 ,而晚期高钾岩石则与东亚和青藏地区构造伸展有关 ,起源于新近交代富集的亏损地幔。 相似文献
117.
The Bitterroot metamorphic core complex is an exhumed, mid-crustal, plutonic–metamorphic complex that formed during crustal thickening and subsequent extension in the hinterland of the North American Cordilleran Orogen, in the northern Idaho batholith region. Extension was accommodated mainly on the Bitterroot mylonite zone, a 500–1500-m-thick shear zone that deforms granitic intrusive rocks as young as 53–52 Ma, as well as older high-grade metamorphic rocks and plutons. Exhumation of the core complex, in Eocene time, is marked in the shear zone by the transition from amphibolite-facies mylonitization, to greenschist-facies mylonitization, chloritic brecciation, to brittle faulting that progressed from shallower crustal levels in the west to deeper crustal levels in the east from ca. 53 –30 Ma based on U–Pb, Ar–Ar, and fission-track data. Apatite and zircon fission-track data record the lower-temperature part of the exhumation history and help define when the shear zone became inactive, as well as the transition from rapid, core complex-style extension to slower basin-and-range-style extension. They indicate that the western part of the complex was exhumed to within 1–2 km of the surface by 48–45 Ma, while the eastern part of the complex was still at amphibolite-facies conditions and that the eastern part of the complex was not exhumed below 60 °C until after 30 Ma. Younger apatite fission-track ages (≤26 Ma) on the eastern range front of the Bitterroot Mountains suggest that the present topographic expression of the mylonite front was due to Miocene high-angle faulting and widening of the Bitterroot Valley. 相似文献
118.
Rasoul B. Sorkhabi Arvind K. Jain Tetsumaru Itaya Shiro Fukui Nand Lal Ashok Kumar 《Journal of Earth System Science》1997,106(3):169-179
The cooling and tectonic history of the Higher Himalayan Crystallines (HHC) in southwest Zanskar (along the Kishtwar-Padam
traverse) is constrained by K-Ar biotite and fission-track (FT) apatite and zircon ages. A total of nine biotite samples yields
ages in the range of 14–24 Ma, indicating the post-metamorphic cooling of these rocks through ∼ 300°C in the Miocene. Overall,
the ages become younger away from the Zanskar Shear Zone (ZSZ), which marks the basement-cover detachment fault between the
HHC and the Tethyan sedimentary zone, towards the core of the HHC. The same pattern is also observed for the FT apatite ages,
which record the cooling of the rocks through ∼ 120°C. The apatite ages range from 11 Ma in the vicinity of the ZSZ to 4 Ma
at the granitic core of the HHC. This pattern of discordant cooling ages across the HHC in southwest Zanskar reveals an inversion
of isotherms due to fast uplift-denudation (hence cooling) of the HHC core, which is, in turn, related to domal uplift within
the HHC. The Chisoti granite gneiss is the exposed domal structure along the studied traverse. Cooling history of two granite
gneisses at the core of the HHC is also quantified with the help of the biotite, zircon and apatite ages; the time-temperatures
thus obtained indicate a rapid pulse of cooling at ∼ 6 Ma, related to accelerated uplift-denudation of the HHC core at this
time. Long-term denudation rates of 0.5–0.7 mm/yr are estimated for the high-grade rocks of the Higher Himalaya in southwest
Zanskar over the past 4.0–5.5 m.yr. 相似文献
119.
对巴颜喀拉山年宝玉则花岗岩岩体样品的锆石、磷灰石进行了裂变径迹(FT)分析。结果显示该区的隆升可以分为三大阶段:①从低绿片岩相到锆石时钟启动:从200MaBP到105.57MaBP,去顶量约为2km,样品埋深上升到距地表约6km深度。去顶速率约为0.02mm/a;②从锆石时钟启动到磷灰石时钟启动:由于磷灰石在此时已抬升到距地表约6km的深度。由此到达时钟启动需距地表约3km时,去顶量应为3km,此阶段的持续时间为101.53MaBP,去顶速率约为0.03mm/a:③从磷灰石时钟启动至达到地表(至今):由于磷灰石在前一阶段也已抬升到距地表约3km的深度。即去顶量为3km。此阶段的持续时间为4.04MaBP,去顶速率约为0.74mm/a。 相似文献
120.
构造热演化是沉积盆地基础地质研究的重要内容,更是油气勘探中不可或缺的部分,多种古地温方法的综合对比研究是目前热史研究主要发展趋势。本文将裂变径迹(FT)和(U-Th)/He热年代学、镜质体反射率法(Ro)和盆地模拟等技术相结合,运用正演和反演的方法重建了川东北地区埋藏–剥露热演化历史。研究表明川东北地区自晚白垩世埋深达到最大后进入剥蚀阶段,大约从92 Ma开始隆升,经历了快速隆升–缓慢隆升–加速隆升三个阶段,整个过程的剥蚀量大约3~4 km,且两次大的剥露过程分别受控于雪峰山的隆起造山以及大巴山的推覆和青藏高原的隆升作用。研究还建立了综合热年代学、Ro和盆地模拟技术恢复复杂构造–热演化历史的方法,这对于复杂环境下的构造热演化历史的恢复以及海相油气勘探具有重要的意义。 相似文献