全文获取类型
收费全文 | 344篇 |
免费 | 14篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 12篇 |
地球物理 | 79篇 |
地质学 | 182篇 |
海洋学 | 17篇 |
天文学 | 26篇 |
自然地理 | 29篇 |
出版年
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 2篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 11篇 |
2013年 | 12篇 |
2012年 | 14篇 |
2011年 | 24篇 |
2010年 | 15篇 |
2009年 | 20篇 |
2008年 | 20篇 |
2007年 | 21篇 |
2006年 | 21篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 12篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1964年 | 2篇 |
1960年 | 1篇 |
1952年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有361条查询结果,搜索用时 31 毫秒
121.
Bernhard Chapligin Melanie J. Leng Anne Alexandre Akira Ijiri Aldo Shemesh Ulrike Herzschuh Hanno Meyer Yusuke Okazaki Zachary D. Sharp Corinne Sonzogni Florence Sylvestre Ruth Yam 《Geochimica et cosmochimica acta》2011,75(22):7242-7256
Several techniques have been introduced in the last decades for the dehydration and release of O2 from biogenic silica (opal-A) for oxygen-isotope analysis. However, only one silica standard is universally available: a quartz standard (NBS28) distributed by the IAEA, Vienna. Hence, there is a need for biogenic silica working standards. This paper compares the existing methods of oxygen-isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the δ18O values of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of δ18O values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by scanning electron microscopy (SEM) were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a standard deviation (SD) for δ18O values between 0.3‰ and 0.9‰ (1σ). Based on the results, we propose four additional biogenic silica working standards (PS1772-8: 42.8‰; BFC: 29.0‰; MSG60: 37.0‰; G95-25-CL leaves: 36.6‰) for δ18O analyses, available on request through the relevant laboratories. 相似文献
122.
Christian A. Miller Bernhard Peucker-Ehrenbrink Franco Marcantonio 《Geochimica et cosmochimica acta》2011,75(22):7146-7179
We re-evaluate the cycling of molybdenum (Mo) and rhenium (Re) in the near-surface environment. World river average Mo and Re concentrations, initially based on a handful of rivers, are calculated using 38 rivers representing five continents, and 11 of 19 large-scale drainage regions. Our new river concentration estimates are 8.0 nmol kg−1 (Mo), and 16.5 pmol kg−1 (Re, natural + anthropogenic). The linear relationship of dissolved Re and in global rivers (R2 = 0.76) indicates labile continental Re is predominantly hosted within sulfide minerals and reduced sediments; it also provides a means of correcting for the anthropogenic contribution of Re to world rivers using independent estimates of anthropogenic sulfate. Approximately 30% of Re in global rivers is anthropogenic, yielding a pre-anthropogenic world river average of 11.2 pmol Re kg−1. The potential for anthropogenic contribution is also seen in the non-negligible Re concentrations in precipitation (0.03-5.9 pmol kg−1), and the nmol kg−1 level Re concentrations of mine waters. The linear Mo- relationship (R2 = 0.69) indicates that the predominant source of Mo to rivers is the weathering of pyrite. An anthropogenic Mo correction was not done as anthropogenically-influenced samples do not display the unambiguous metal enrichment observed for Re. Metal concentrations in high temperature hydrothermal fluids from the Manus Basin indicate that calculated end-member fluids (i.e. Mg-free) yield negative Mo and Re concentrations, showing that Mo and Re can be removed more quickly than Mg during recharge. High temperature hydrothermal fluids are unimportant sinks relative to their river sources 0.4% (Mo), and 0.1% (pre-anthropogenic Re). We calculate new seawater response times of 4.4 × 105 yr (τMo) and 1.3 × 105 yr (τRe, pre-anthropogenic). 相似文献
123.
Hannah Pomella Urs Klötzli Robert Scholger Michael Stipp Bernhard Fügenschuh 《International Journal of Earth Sciences》2011,100(8):1827-1850
This study concentrates on small intrusions along two important faults of the Giudicarie fault system, the Northern Giudicarie
and the Meran-Mauls fault, summarised under the term tonalitic lamellae. Magnetic fabric analyses in combination with structural
field data indicate dextral strike slip deformation along the NE–SW striking northern part of the Giudicarie fault system,
the Meran-Mauls fault, overprinted by younger thrusting. The regional stressfield was oriented approximately NNW–SSE during
Tertiary times. The distinctive change in deformation along the Meran-Mauls fault from dextral strike slip to top-SE thrusting
may be caused by a rotation or bending of the fault after the intrusion of the tonalites and the formation of their horizontal
magnetic foliation. Based on the assumption of a preliminary straight Periadriatic lineament bent by the NNW-wards advancement
of the Southalpine indenter, the tonalitic lamellae may be interpreted as lenses sheared off from the Adamello batholith during
indentation. New U/Pb data on zircon show that some of the lamellae are of Oligocene (Rupelian), others of Late Eocene (Priabonian)
age. An amphibole-gabbro lens occurring on the Meran-Mauls fault provides a Middle Eocene (Bartonian) age. Among the major
Periadriatic plutons, only the southern units of the Adamello batholith also intruded in the Eocene that suggests a strong
correlation between the tonalitic lamellae and the Adamello batholith. The analyses of the remanent magnetisation and the
Curie point determinations argue for magnetite as the main carrier of a viscous magnetisation blocked at relatively low temperatures.
This indicates slow cooling of the investigated intrusions along the Giudicarie fault system down to approximately 300°C,
which is in contrast to the fast cooling determined for the Adamello intrusion units currently at the surface. The new zircon
fission track data also show later cooling of the tonalites along the Giudicarie fault system when compared with the Adamello
batholith in the south and the Mauls lamellae in the north, indicating that this area contains magmatic bodies exhumed from
a deeper structural level than in the Adamello and the Mauls region. This may be due to important top-SE thrusting and transpressive
faulting in the footwall of the Northern Giudicarie fault and the Meran-Mauls fault. 相似文献
124.
Listric versus planar normal fault geometry: an example from the Eisenstadt-Sopron Basin (E Austria) 总被引:1,自引:0,他引:1
Darko Spahić Ulrike Exner Michael Behm Bernhard Grasemann Alexander Haring Herbert Pretsch 《International Journal of Earth Sciences》2011,100(7):1685-1695
In a gravel pit at the eastern margin of the Eisenstadt-Sopron Basin, a satellite of Vienna Basin (Austria), Neogene sediments
are exposed in the hanging wall of a major normal fault. The anticlinal structure and associated conjugated secondary normal
faults were previously interpreted as a rollover anticline above a listric normal fault. The spatial orientation and distribution
of sedimentary horizons and crosscutting faults were mapped in detail on a laser scan of the outcrop wall. Subsequently, in
order to assess the 3D distribution and geometry of this fault system, a series of parallel ground penetrating radar (GPR)
profiles were recorded behind the outcrop wall. Both outcrop and GPR data were compiled in a 3D structural model, providing
the basis for a kinematic reconstruction of the fault plane using balanced cross-section techniques. However, the kinematic
reconstruction results in a geologically meaningless normal fault cutting down- and up-section. Additionally, no evidence
for a weak layer serving as ductile detachment horizon (i.e. salt or clay horizon) can be identified in stratigraphic profiles.
Instead, the observed deflection of stratigraphic horizons may be caused by a displacement gradient along a planar master
fault, with a maximum displacement in the fault centre, decreasing towards the fault tips. Accordingly, the observed deflection
of markers in the hanging wall—and in a nearby location in the footwall of the normal fault—is interpreted as large-scale
fault drag along a planar fault that records a displacement gradient, instead of a rollover anticline related to a listric
fault. 相似文献
125.
126.
Bernhard Butzin 《GeoJournal》1991,2(1):11-26
Within a typical process of urbanization several particularities can be noticed in the Helsinki region: The peninsular location does not allow a zonal expansion of the city. It has rather enforced a tight spatial sectoral expansion with specific problems of traffic and land use. The retarded industrialization has led to an unusually fast population increase without control until the 1960s.The rapid growth created a twofold problem: pressure of population versus inadequate housing, small residences versus high rents; consequently selective migration and small size families. The number of jobs rapidly increased and displaced the residential population of the inner city. This resulted in high traffic which neither the few main roads nor the public transport system of central Helsinki could cope with.These problems correspond to the essential tasks of urban planning: the bottle neck in housing construction has to be broken; the growth of jobs in the central city needs to be stopped as well as the displacement of the residential population. Decentralization, especially of the private tertiary and quartary sector may help. A system of central places within the region would diminish the commuting traffic. Transportation may be solved by a concept of growth points and growth axis along the railway lines.This grown concept of Helsinki should be thought over under the now foreseeable conditions of population stagnation. 相似文献
127.
We investigate shear band initiation and propagation in fully saturated porous media by means of a combination of strong discontinuities (discontinuities in the displacement field) and XFEM. As a constitutive behavior of the solid phase, a Drucker–Prager model is used within a framework of non-associated plasticity to account for dilation of the sample. Strong discontinuities circumvent the difficulties which appear when trying to model shear band formation in the context of classical nonlinear continuum mechanics and when trying to resolve them with classical numerical methods like the finite element method. XFEM, on the other hand, is well suited to deal with problems where a discontinuity propagates, without the need of remeshing. The numerical results are confirmed by the application of Hill’s second-order work criterion which allows to evaluate the material point instability not only locally but also for the whole domain. 相似文献
128.
The adaptive composite map projection technique changes the projection to minimize distortion for the geographic area shown on a map. This article improves the transition between the Lambert azimuthal projection and the transverse equal-area cylindrical projection that are used by adaptive composite projections for portrait-format maps. Originally, a transverse Albers conic projection was suggested for transforming between these two projections, resulting in graticules that are not symmetric relative to the central meridian. We propose the alternative transverse Wagner transformation between the two projections and provide equations and parameters for the transition. The suggested technique results in a graticule that is symmetric relative to the central meridian, and a map transformation that is visually continuous with changing map scale. 相似文献
129.
Rock avalanches destroy and reshape landscapes in only a few minutes and are among the most hazardous processes on Earth. The surface morphology of rock avalanche deposits and the interaction with the underlying material are crucial for runout properties and reach. Water within the travel path is displaced, producing large impact waves and reducing friction, leading to long runouts. We hypothesize that the 0.2 km3 Holocene Eibsee rock avalanche from Mount Zugspitze in the Bavarian Alps overran and destroyed Paleolake Eibsee and left a unique sedimentological legacy of processes active during the landslide. We captured 9.5 km of electrical resistivity tomography (ERT) profiles across the rock avalanche deposits, with up to 120 m penetration depth and more than 34 000 datum points. The ERT profiles reveal up to ~50 m thick landslide debris, locally covering up to ~30 m of rock debris with entrained fine-grained sediments on top of isolated remnants of decametre-wide paleolake sediments. The ERT profiles allow us to infer processes involved in the interaction of the rock avalanche with bedrock, lake sediments, and morainal sediments, including shearing, bulging, and bulldozing. Complementary data from drilling, a gravel pit exposure, laboratory tests, and geomorphic features were used for ERT calibration. Sediments overrun by the rock avalanche show water-escape structures. Based on all of these datasets, we reconstructed both position and size of the paleolake prior to the catastrophic event. Our reconstruction of the event contributes to process an understanding of the rock avalanche and future modelling and hazard assessment. Here we show how integrated geomorphic, geophysical, and sedimentological approaches can provide detailed insights into the impact of a rock avalanche on a lake. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献
130.
Gertraud Meißl Clemens Geitner Andreas Batliner Klaus Klebinder Bernhard Kohl Gerhard Markart 《水文研究》2021,35(6):e14186
The Brixenbach valley is a small Alpine torrent catchment (9.2 km2, 820–1950 m a.s.l., 47.45°, 12.26°) in Tyrol, Austria. Intensive hydrological research in the catchment since more than 12 years, including a hydrogeological survey, pedological and land use mapping, measurements of precipitation, runoff, soil moisture and infiltration as well as the conduction of rainfall simulations, has contributed to understand the hydrological response of the catchment, its subcatchments and specific sites. The paper presents a synthesis of the research in form of runoff process maps for different soil moisture states and precipitation characteristics, derived with the aid of a newly developed Soil-hydrological model. These maps clearly visualize the differing runoff reaction of different subcatchments. The pasture dominated areas produce high surface flow rates during short precipitation events (1 h, 86 mm) with high rainfall intensity, whilst the forested areas often develop shallow subsurface flow. Dry preconditions lead to a slight reduction of surface flow, long rainfall events (24 h, 170 mm) to a dominance of deep subsurface flow and percolation. 相似文献