全文获取类型
收费全文 | 529篇 |
免费 | 23篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 32篇 |
地球物理 | 134篇 |
地质学 | 192篇 |
海洋学 | 22篇 |
天文学 | 138篇 |
综合类 | 1篇 |
自然地理 | 25篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 12篇 |
2019年 | 12篇 |
2018年 | 24篇 |
2017年 | 22篇 |
2016年 | 36篇 |
2015年 | 28篇 |
2014年 | 36篇 |
2013年 | 31篇 |
2012年 | 29篇 |
2011年 | 33篇 |
2010年 | 25篇 |
2009年 | 37篇 |
2008年 | 35篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 17篇 |
2004年 | 16篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1940年 | 2篇 |
1939年 | 1篇 |
排序方式: 共有556条查询结果,搜索用时 15 毫秒
161.
Michele Marroni M.Cemal Goncüoglu Chiara Frassi Kaan Sayit Luca Pandolfi Alessandro Ellero Giuseppe Ottria 《地学前缘(英文版)》2020,11(1):129-149
The Anatolian peninsula is a key location to study the central portion of the Neotethys Ocean(s)and to understand how its western and eastern branches were connected.One of the lesser known branches of the Mesozoic ocean(s)is preserved in the northern ophiolite suture zone exposed in Turkey,namely,the Intra-Pontide suture zone.It is located between the Sakarya terrane and the Eurasian margin(i.e.,Istanbul-Zonguldak terrane)and consists of several metamorphic and non-metamorphic units containing ophiolites produced in supra-subduction settings from the Late Triassic to the Early Cretaceous.Ophiolites preserved in the metamorphic units recorded pervasive deformations and peak metamorphic conditions ranging from blueschist to eclogite facies.In the nonmetamorphic units,the complete oceanic crust sequence is preserved in tectonic units or as olistoliths in sedimentary melanges.Geochemical,structural,metamorphic and geochronological investigations performed on ophiolite-bearing units allowed the formulation of a new geodynamic model of the entire"life"of the IntraPontide oceanic basin(s).The reconstruction starts with the opening of the Intra-Pontide oceanic basins during the Late Triassic between the Sakarya and Istanbul-Zonguldak continental microplates and ends with its closure caused by two different subductions events that occurred during the upper Early Jurassic and Middle Jurassic.The continental collision between the Sakarya continental microplate and the Eurasian margin developed from the upper Early Cretaceous to the Palaeocene.The presented reconstruction is an alternative model to explain the complex and articulate geodynamic evolution that characterizes the southern margin of Eurasia during the Mesozoic era. 相似文献
162.
Implications of land use change on the national terrestrial carbon budget of Georgia 总被引:1,自引:0,他引:1
Pontus Olofsson Paata Torchinava Curtis E Woodcock Alessandro Baccini Richard A Houghton Mutlu Ozdogan Feng Zhao Xiaoyuan Yang 《Carbon balance and management》2010,5(1):4
Background
Globally, the loss of forests now contributes almost 20% of carbon dioxide emissions to the atmosphere. There is an immediate need to reduce the current rates of forest loss, and the associated release of carbon dioxide, but for many areas of the world these rates are largely unknown. The Soviet Union contained a substantial part of the world's forests and the fate of those forests and their effect on carbon dynamics remain unknown for many areas of the former Eastern Bloc. For Georgia, the political and economic transitions following independence in 1991 have been dramatic. In this paper we quantify rates of land use changes and their effect on the terrestrial carbon budget for Georgia. A carbon book-keeping model traces changes in carbon stocks using historical and current rates of land use change. Landsat satellite images acquired circa 1990 and 2000 were analyzed to detect changes in forest cover since 1990. 相似文献163.
164.
Marco G. Malus Riccardo Polino Andrea Cerrina Feroni Alessandro Ellero Giuseppe Ottria Lahssen Baidder Giovanni Musumeci 《地学学报》2007,19(6):481-489
New field data integrated by fission‐track (FT) analysis unravel an innovative scenario for the post‐Variscan evolution of the eastern Anti‐Atlas. This area, unaffected by Meso‐Cenozoic tectonics according to most workers, is crosscut by crustal faults bearing evidence of a polyphase deformation history. Apatite FT ages, ranging between 284 and 88 Ma, point to fast Neogene exhumation and unravel contrasting cooling paths across major faults. Results show that the study area was buried beneath 2 km of allochthonous Variscan units, now eroded. The eastern Anti‐Atlas acted as the southern shoulder of the Atlasic rift in the Mesozoic, and underwent a dextral transpressional structuring of Neogene age followed by sub‐meridian shortening. The southern front of Atlasic deformation is therefore located inside the Anti‐Atlas region, and it is still active. 相似文献
165.
Alessandro Morbidelli Antonio Giorgilli 《Celestial Mechanics and Dynamical Astronomy》1989,47(2):173-204
The general theory exposed in the first part of this paper is applied to the following resonances with Jupiter's motion : 3/2, 2/1, 5/2, 3/1, 7/2, 4/1; these are the most relevant resonances for the asteroids. The whole analysis is performed in the framework of the spatial problem of three bodies, both in the circular and in the elliptic case. The results are also compared with the observed distribution of the asteroids. 相似文献
166.
Margherita Polacci Michael R. Burton Alessandro La Spina Filippo Murè Stefano Favretto Franco Zanini 《Journal of Volcanology and Geothermal Research》2009,179(3-4):265-269
We investigated the dynamics of explosive activity at Mt. Etna between 31 August and 15 December 2006 by combining vesicle studies in the erupted products with measurements of the gas composition at the active, summit crater. The analysed scoria clasts present large, connected vesicles with complex shapes and smaller, isolated, spherical vesicles, the content of which increases in scoriae from the most explosive events. Gas geochemistry reports CO2/SO2 and SO2/HCl ratios supporting a deep-derived gas phase for fire-fountain activity. By integrating results from scoria vesiculation and gas analysis we find that the highest energy episodes of Mt. Etna activity in 2006 were driven by a previously accumulated CO2-rich gas phase but we highlight the lesser role of syn-eruptive vesicle nucleation driven by water exsolution during ascent. We conclude that syn-eruptive vesiculation is a common process in Etnean magmas that may promote a deeper conduit magma fragmentation and increase ash formation. 相似文献
167.
A. Aiuppa W. D’Alessandro S. Gurrieri P. Madonia F. Parello 《Environmental Geology》2007,53(4):903-913
Hydrological and geochemical studies performed on Lake Specchio di Venere on Pantelleria island (Italy) indicate that this
endorheic basin has been formed through upwelling of the water table, and that it is continuously fed by the thermal springs
situated on its shores. The lake is periodically stratified both thermally and in salinity, albeit this stratification is
rather unstable over time, since meteorological events such as strong rain or wind can determine the mixing of its waters.
Periodical analyses of the lake water chemistry show large variations of the salt content due to the yearly evaporation-rain
dilution cycle. These processes are also responsible for the saline stratification during steady meteorological conditions.
The mineralogical characterisation of the bottom sediments shows the almost exclusive presence of neoformation minerals, mainly
carbonates, formed in response to the pH gradient between spring- (pH ≈ 6) and lake-waters (pH ≈ 9). Finally, the CO2 partial pressures in the lake water slightly exceeding the atmospheric one, are due to the large amounts of CO2 brought to the lake through the bubbling free gas phase of the thermal springs. Nevertheless the high pH value of the lake
water, its small volume and its periodical mixing prevent dangerous built up of this gas. 相似文献
168.
Alessandro Bonforte Salvatore Gambino Francesco Guglielmino Francesco Obrizzo Mimmo Palano Giuseppe Puglisi 《Bulletin of Volcanology》2007,69(7):757-768
On 22 September 2002, 1 month before the beginning of the flank eruption on the NE Rift, an M-3.7 earthquake struck the northeastern
part of Mt. Etna, on the westernmost part of the Pernicana fault. In order to investigate the ground deformation pattern associated
with this event, a multi-disciplinary approach is presented here. Just after the earthquake, specific GPS surveys were carried
out on two small sub-networks, aimed at monitoring the eastern part of the Pernicana fault, and some baselines belonging to
the northeastern EDM monitoring network of Mt. Etna were measured. The leveling route on the northeastern flank of the volcano
was also surveyed. Furthermore, an investigation using SAR interferometry was performed and also the continuous tilt data
recorded at a high precision sensor close to the epicenter were analyzed to constrain the coseismic deformation. The results
of the geodetic surveys show a ground deformation pattern that affects the entire northeastern flank of the volcano, clearly
shaped by the Pernicana fault, but too strong and wide to be related only to an M-3.7 earthquake. Leveling and DInSAR data
highlight a local strong subsidence, up to 7 cm, close to the Pernicana fault. Significant displacements, up to 2 cm, were
also detected on the upper part of the NE Rift and in the summit craters area, while the displacements decrease at lower altitude,
suggesting that the dislocation did not continue further eastward. Three-dimensional GPS data inversions have been attempted
in order to model the ground deformation source and its relationship with the volcano plumbing system. The model has also
been constrained by vertical displacements measured by the leveling survey and by the deformation map obtained by SAR interferometry. 相似文献
169.
F. D’Alessandro A. A. Deshpande P. M. McCulloch 《Journal of Astrophysics and Astronomy》1997,18(1):5-14
Power spectra of the timing noise observed in 18 southern pulsars have been derived using a novel technique, based on the
CLEAN algorithm. Most of the spectra are well described by a single- or double-component power-law model. Some of these spectra
can be interpreted in the context of one or more of the current timing noise models. The results combined with those obtained
from the time-domain analyses of the timing activity in these pulsars are used to assess the viability of the various theoretical
models of pulsar timing noise. 相似文献
170.
Linda Schmidtobreick Claus Tappert Alessandro Ederoclite Ivo Saviane Elena Mason 《Astrophysics and Space Science》2006,304(1-4):303-305
We report preliminary results of an observing run at the 1--m telescope at CTIO during which we followed RR Pic over several nights in February 2005. The resulting light curves show no sign of an eclipse. Apart from the 3.48 h period, which is usually interpreted as the orbital one, we find an additional period at P=3.78 h, which we interpret as the superhump period of the system.We furthermore present high–resolution Doppler maps in Hα, Hβ and He II, which we derived from observations at the NTT, La Silla in February 2004. They show strong variations in the emission distribution from one day to the next. While Hα and Hβ emission clearly show the accretion disc with some additional isolated sources, the He II emission is confined to an elongated region at low velocities. 相似文献