全文获取类型
收费全文 | 201篇 |
免费 | 7篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 15篇 |
地球物理 | 30篇 |
地质学 | 91篇 |
海洋学 | 25篇 |
天文学 | 16篇 |
综合类 | 6篇 |
自然地理 | 24篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 10篇 |
2010年 | 17篇 |
2009年 | 7篇 |
2008年 | 10篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1980年 | 1篇 |
1969年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有219条查询结果,搜索用时 15 毫秒
211.
The orbital evolutions of the asteroid 3040 Kozai and model asteroids with similar orbits have been investigated. Their osculating orbits for an epoch 1991 December 10 were numerically integrated forward within the interval of 20,000 years, using a dynamical model of the solar system consisting of all inner planets, Jupiter, and Saturn.The orbit of the asteroid Kozai is stable. Its motion is affected only by long-period perturbations of planets. With change of the argument of perihelion of the asteroid Kozai, the evolution of the model asteroid orbits changes essentially, too. The model orbits with the argument of perihelion changed by the order of 10% show that asteroids with such orbital parameters may approach the Earth orbit, while asteroids with larger changes may even cross it, at least after 10,000 years. Long-term orbital evolution of asteroids with these orbital parameters is very sensitive on their angular elements. 相似文献
212.
Robert S. Sommer Arne Persson Nina Wieseke Uwe Fritz 《Quaternary Science Reviews》2007,26(25-28):3099-3107
We reconstruct the Holocene range fluctuations of the European pond turtle (Emys orbicularis) for northern and Central Europe. Based on 529 subfossil records and radiocarbon dating of critical finds, we provide evidence that E. orbicularis experienced a rapid range expansion with Holocene warming. Phylogeographic data argue for a colonization of northern and Central Europe from a glacial refuge located in the south-eastern Balkans. Already in the Late Preboreal (9100–8600 cal BC) the species occurred in northern Central Europe and was widespread in Denmark and southern Sweden (Skåne) during the Boreal (8600–7100 cal BC). The maximum range extension occurred during the Holocene climatic optimum (Atlantic: 7100–3750 cal BC), with records in southern England, middle Sweden, and northern Estonia. After the early Subboreal (3750–1750 cal BC) northern populations collapsed, coinciding with a climatic cooling and oceanization. Northern populations were most likely established via long distance dispersal (rafting using rivers debouching in the North and Baltic Seas); after northern Europe was reached, a minimum dispersal of 50 km per 100 years may be hypothesized for the Boreal. 相似文献
213.
214.
Urška Kuhar Tatjana Gregorc Miran Ren?elj Nina Šraj-Kr?i? Alenka Gaberš?ik 《Limnologica》2007,37(2):146-154
The distribution and abundance of macrophytes, land-use beyond the riparian zone, characteristics of the riparian zone and selected channel properties have been studied in 9 streams flowing through an agricultural landscape in the north-eastern part of Slovenia. The streams studied supported a rich macrophyte community. Altogether, 53 plant taxa were observed on 93 km of the streams. Canonical correspondence analysis indicated that 10 out of the 11 parameters examined significantly influenced macrophyte distribution. Of these, substrate characteristics and riparian vegetation type were the most influential. Species composition analysis revealed that the majority of species indicated moderate nutrient load while, in the more strongly modified reaches, species indicating eutrophic conditions, i.e. Myriophyllum spicatum and different species of genus Potamogeton, were more abundant. 相似文献
215.
Simona Skobe Špela Goričan Dragomir Skaberne Tomaž Verbič Miha Mišič Nina Zupančič 《Swiss Journal of Geoscience》2013,106(3):491-504
The study area in southeastern Slovenia is part of the transitional zone between the internal and the external Dinarides. Within Jurassic bedded cherts there are up to 2 cm thick shale intercalations, consisting of laminated, soft, fine-grained, green to brown material whose origin has been in question. In the majority of Tethyan cherts, the interbedded material is reported to be volcanogenic and/or terrigenous, although a detailed mineralogical analysis of the material is lacking. An XRD analysis confirmed the presence of quartz, illite, chlorite and K-feldspar, which is the prevailing component in some samples. Major and trace element data exclude both a volcanogenic and an hydrothermal origin. Several discrimination diagrams indicate the upper crustal terrigenous nature of shales and a biogenic silica source. The source material was probably from a Variscan crust, which at the time of deposition had already been weathered to kaolinite, and some sporadic muscovite. The MnO/Al2O3 ratio suggests a slow sedimentation rate of cherts and a faster one for shales, which probably settled from distal turbidity currents. The negative Ce anomaly indicates prolonged contact with ocean water. Sediments were deposited on a Tethyan passive margin, originally as silica-rich carbonate beds intercalated with mud. During late diagenesis, the mixing of marine and meteoric waters caused the further silicification of limestone and simultaneous potassium enrichment of shale which led to their alteration into illite or chlorite and, in sediments already rich in K-minerals, into K-feldspar. 相似文献
216.
217.
Désirée Hilbring Tanja Titzschkau Alfons Buchmann Gottfried Bonn Friedemann Wenzel Eberhard Hohnecker 《Natural Hazards》2014,70(3):1795-1825
This paper analyzes the potential of earthquake early-warning systems for transport lines. The interdisciplinary work focuses on rapidly producing an alert map during an ongoing earthquake as well as providing a damage map immediately after the strong-motion phase that visualizes potential damages to the railway infrastructure. In order to meet these application requirements, a service-oriented architecture based on geospatial standards is specified. This ensures the portability of the system architecture to different geographic regions as well as a potential transfer to other natural disasters and infrastructure systems. The first part of the paper describes the standard-based services of the system architecture together with design principles that are useful for the realization of early-warning systems. In the second part of the paper, an online demonstrator for the exemplary test area in the federal state of Baden-Württemberg, Germany, is presented. The system architecture of the demonstrator includes an earthquake early-warning methodology based on artificial neural networks and an infrastructure-specific damage assessment. The third part of the paper analyzes the potential of implementing low-cost sensors in the track, which would provide a dense network directly at the railway infrastructure. 相似文献
218.
We conducted a field experiment to assess the response of phytal harpacticoids to nutrient‐driven increases of epiphyte load in Posidonia oceanica meadows. First, we evaluated differences in species richness, diversity and assemblage structure of phytal harpacticoids in P. oceanica meadows with differing epiphyte loads. Secondly, we conducted a field experiment where epiphyte load was increased through an in situ addition of nutrients to the water column and evaluated the responses of the harpacticoid assemblages. We predicted that there would be changes in the harpacticoid assemblages as a result of nutrient‐driven increases of epiphyte load, and that these changes would be of a larger magnitude in meadows of low epiphyte load. Our results show that the harpacticoid fauna (>500 μm) present in P. oceanica meadows in the Bay of Palma comprised taxa which are considered phytal and other less abundant ones previously described as sediment dwellers or commensal on other invertebrate species. Nutrient addition had an overall significant effect on epiphyte biomass and on harpacticoid abundance, diversity and assemblage structure, possibly as a response to the increased resources and habitat complexity provided by epiphytes. The abundance of dominant species at each location was favoured by nutrient addition and in some cases correlated with epiphytic biomass, although never strongly. This may indicate that structural complexity or diversity of the epiphytic cover might be more important than the actual epiphytic biomass for the harpacticoid species investigated. More species‐specific studies are necessary to ascertain this and clarify the relationships between harpacticoids and epiphytes in seagrass meadows. To our knowledge, this is the first account of harpacticoid species associated with P. oceanica leaves and the epiphytic community they harbour in the Mediterranean Sea. 相似文献
219.
Trace elements and cathodoluminescence of quartz in stockwork veins of Mongolian porphyry-style deposits 总被引:1,自引:0,他引:1
Axel Müller Richard Herrington Robin Armstrong Reimar Seltmann Douglas J. Kirwin Nina G. Stenina Andreas Kronz 《Mineralium Deposita》2010,45(7):707-727
The combination of scanning electron microscope–cathodoluminescence (CL), fluid inclusion analysis and high-resolution electron
probe microanalysis of Al, Ti, K and Fe in vein quartz has yielded results permitting a greater understanding of the complex
mineralisation of the Central Oyu Tolgoi and Zesen Uul porphyry-style deposits, southern Mongolia. These data demonstrate
the relationship between quartz precipitation, dissolution and ore deposition as the mineralising fluid chemistry changed
through time. Four major quartz generations are identified in the A-type veins from the stockworks of both the Central Oyu
Tolgoi (OTi to OTiv) and Zesen Uul deposits (ZUi to ZUiv). Despite differences in the associated alteration and mineralisation
style, the observed CL textures and trace element signatures of the quartz generations are comparable between deposits. The
OTi and ZUi stage formed both the primary network of A-type veins and pervasive silicification of the host rock. Using the
Ti-in-quartz geothermometer, crystallisation temperatures for OTi and ZUi of between 598°C and 880°C are indicated. The main
stage of sulphide mineralisation was accompanied by the dissolution of pre-existing quartz (OTi and ZUi) and precipitation
of a weakly luminescent generation of quartz (OTii and ZUii) with a low Ti content, reflected in a calculated temperature
drop from approximately 700°C to 340°C in Central Oyu Tolgoi and 445°C in Zesen Uul. OTii and ZUii stage quartzes show high
and variable Al concentrations. The next stage of quartz in both deposits (OTiii and ZUiii) forms a fine network of veins
in cracks formed in pre-existing quartz. OTiii and ZUiii quartz contain measurable fluid inclusions of moderate salinity (3–17.1 wt.%
NaCl eq.), entrapped in the temperature range 256°C to 385°C. OTiii and ZUiii are not related to any sulphide mineralisation.
The final OTiv and ZUiv stages are characterised by quartz–calcite micro-breccias that penetrate the A-type veins. Based on
the calculated entrapment temperatures, the OTiv/ZUiv stage crystallised between 212°C and 335°C, and the quartz is characterised
by elevated but variable Al and Fe contents. The CL and trace element signatures of the OTi to OTiii and ZUi to ZUiii stages
of the two Mongolian porphyries show similar features to those observed in porphyry-style deposits from other regions. This
suggests that a common sequence of quartz crystallisation occurs during the formation of early veins in many porphyry copper
systems. 相似文献