全文获取类型
收费全文 | 179篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 8篇 |
地球物理 | 51篇 |
地质学 | 58篇 |
海洋学 | 24篇 |
天文学 | 23篇 |
综合类 | 1篇 |
自然地理 | 16篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 9篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 17篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有187条查询结果,搜索用时 531 毫秒
51.
L. Matias N. A. Dias I. Morais D. Vales F. Carrilho J. Madeira J. L. Gaspar L. Senos A. B. Silveira 《Journal of Seismology》2007,11(3):275-298
The Faial earthquake (M
L 5.8) that occurred on the 9th of July, 1998, in the Azores region (north Atlantic), caused nine casualties and severe destruction
affecting more than 5,000 people. The main shock was located at sea, 10 km NE of the Faial Island, and triggered a seismic
sequence that lasted for several weeks and was characterized by an unusual high p-value of 1.40 for the modified Omori law. We present here the results of a joint inversion of hypocenters and 1D velocity
model performed on the data collected by the permanent network complemented with a temporary network installed shortly after
the occurrence of the main event. The 1D velocity model shows a heterogeneous upper crust, testified by the observed differences
in site effects at the stations, while the middle crust from ∼2.5 to 8 km in depth is quite homogeneous. The Moho is located
at a depth of about 12–13 km and the Vp/Vs ratio is found to be around 1.78. The events at depth are mainly concentrated in
the middle-lower crust (8–12 km), while their spatial distribution shows a main cluster, visible after relocation, SSE trending.
This direction of elongation is consistent with one of the fault planes (N151°E) of the centroid moment tensor (CMT) solution
for the main shock. The same plane is the preferred main shock fault plane inferred after a Coulomb failure function analysis
on the aftershock distribution. The main event relocation points to a focal depth shallower than 5 km. The aftershocks pattern
shows that several fault systems were reactivated by the stress perturbation induced by the main shock. Besides the two main
tectonic directions, trending WNW–ESE and NNW–SSE, observed in the tectonics of Faial, Pico, and S. Jorge, there is also evidence
of a new tectonic direction trending WSW–ENE. 相似文献
52.
53.
Pereira Rafael H. M. Andrade Pedro R. Vieira João Pedro Bazzo 《Journal of Geographical Systems》2023,25(3):453-466
Journal of Geographical Systems - The creation of the General Transit Feed Specification (GTFS) in the mid-2000s provided a new data format for cities to organize and share digital information on... 相似文献
54.
João Manuel Cabral Fernando Marques Paula Figueiredo Luís Matias 《Journal of Seismology》2011,15(2):215-234
The Lower Tagus Valley has experienced significant (M 6–7) historical seismicity, evidencing the presence of seismogenic faults. These are still deficiently known due to the low strain rates and the recent alluvial sedimentation of the Tagus River that buries most of the structures, though Paleoseismic evidence was allegedly found by a research team in the Tagus valley, at a site 60 km N of Lisbon, near Vila Chã de Ourique (VCO). According to this team, trenching at the VCO site exposed an active thrust fault, evidencing the surface rupture of a large earthquake that occurred in 1531. Our studies performed at this site, comprising field observations with a reappraisal of the trench outcrops previously excavated, borehole drilling, soil mechanics laboratory testing, and seismic reflection acquisition, pointed to the alternative interpretation that the outcropping structures are gravitational and not of tectonic origin. The interpretation of new outcrops crosscutting the structures exposed at the trenches, as well as newly acquired high-resolution seismic reflection data, definitely exclude the active thrust fault explanation and support a gravitational slip model for all the observed structures. Gravitational slip in the river bank slope was promoted by low shear strength clays and high pore water pressure coupled with slope toe river erosion. Gravitational slides must have occurred prior to development of the present sedimentation level of the Tagus alluvial plain, which was attained in the last few thousand years as indicated by borehole data and estimations of sedimentation rates. 相似文献
55.
56.
J. Espinha Marques J. Samper B. Pisani D. Alvares J. M. Carvalho H. I. Chaminé J. M. Marques G. T. Vieira C. Mora F. Sodré Borges 《Environmental Earth Sciences》2011,62(6):1219-1234
High-mountain basins provide a source of valuable water resources. This paper presents hydrological models for the evaluation
of water resources in the high-mountain Zêzere river basin in Serra da Estrela, Central Portugal. Models are solved with VISUAL BALAN v2.0, a code which performs daily water balances in the root zone,
the unsaturated zone and the aquifer and requires a small number of parameters. A lumped hydrological model fails to fit measured
stream flows. Its limitations are overcome by considering the dependence of the temperature and precipitation data with elevation
and the spatial variability in hydrogeomorphological variables with nine sub-basins of uniform parameters. Model parameters
are calibrated by fitting stream flow measurements in the Zêzere river. Computed stream flows are highly sensitive to soil
thickness, whereas computed groundwater recharge is most sensitive to the interflow and percolation recession coefficients.
Interflow is the main component of total runoff, ranging from 41 to 55% of annual precipitation. High interflows are favored
by the steep relief of the basin, by the presence of a high permeability soil overlying the fractured low permeability granitic
bedrock and by the extensive subhorizontal fracturing at shallow depths. Mean annual groundwater recharge ranges from 11 to
15% of annual precipitation. It has a significant uncertainty due to uncertainties in soil parameters. This methodology proves
to be useful to handle the research difficulties regarding a complex mountain basin in a context of data scarcity. 相似文献
57.
Vieira L.E.A. Gonzalez W.D. Echer E. Guarnieri F.L. Prestes A. Gonzalez A.L.C. Santos J.C. Dal Lago A. Schuch N.J. 《Solar physics》2003,217(2):383-394
In this work we present a methodology to estimate the geomagnetic symmetric index (Sym) based on the wavelet analysis of the time series of the H component of the geomagnetic field measured at mid-latitude stations localized at Kakioka (KAK), Honolulu (HON), Hermanus (HER) and San Juan (SJG). A case study of the intense geomagnetic storm of 17–22 February 1999, caused by intense southward magnetic fields just behind an interplanetary shock driven by a magnetic cloud, is shown as an example of the procedure of derivation of the symmetric index and the capabilities of this analysis to improve the study of the coupling of the solar wind and the Earth's magnetosphere. Other examples are shown in order to demonstrate the applicability of the methodology to different magnetospheric conditions. It is shown that the long period variations of the symmetric index are linearly correlated to variations at the same periods of the H component of the geomagnetic field and that the contribution of short period variations to the symmetric index are biased by localized current systems such as the partial ring current and the field aligned currents. 相似文献
58.
Dal Lago A. Vieira L.E.A. Echer E. Gonzalez W.D. de Gonzalez A.L.C. Guarnieri F.L. Schuch N.J. Schwenn R. 《Solar physics》2004,222(2):323-328
We have compared characteristics of 38 halo coronal mass ejections observed on the Sun by the Large Angle and Spectrometric Coronagraph onboard SOHO with their corresponding counterparts observed near Earth by the magnetic field and plasma instruments onboard the ACE, WIND and SOHO satellites, in the period from January 1997 to April 2001. We only have selected events that have some associated interplanetary ejecta structure at 1 AU and we have compared the lateral expansion speeds of these halo CMEs and the corresponding ejecta speeds near Earth. We found that there is a high correlation between these two speeds. The results are very similar to the study done by Lindsay et al. (1999) using observations made by Solwind and SMM coronagraphs, and Helios-1 and PVO plasma and interplanetary field data from the period of 1979 to 1988. Also, we reviewed the relation between the CME-related shock transit speed to Earth and the ejecta speeds near Earth. This kind of relation is very important to estimate ejecta speeds of events for which no interplanetary observations are available. 相似文献
59.
Gonçalves Leonardo Alkmim Fernando F. Pedrosa-Soares Antônio Gonçalves Cristiane C. Vieira Valter 《International Journal of Earth Sciences》2018,107(1):337-358
International Journal of Earth Sciences - The Araçuaí-West Congo orogen (AWCO) is one of the various components of the Brasiliano/Pan-African orogenic network generated during the... 相似文献
60.
A.R. Lopes A. Girona-García S. Corticeiro R. Martins J.J. Keizer D.C.S. Vieira 《地球表面变化过程与地形》2021,46(1):205-219
In the near future, a higher occurrence of wildfires is expected due to climate change, carrying social, environmental, and economic implications. Such impacts are often associated with an increase of post-fire hydrological and erosive responses, which are difficult to predict. Soil erosion models have been proven to be a valuable tool in the decision-making process, from emergency response to long-term planning, however, they were not designed for post-fire conditions, so need to be adapted to include fire-induced changes. In recent years, there have been an increasing number of studies testing different models and adaptations for the prediction of post-fire soil erosion. However, many of these adaptations are being applied without field validation or model performance assessment. Therefore, this study aims to describe the scientific advances in the last 20 years in post-fire soil erosion modelling research and evaluate model adaptations to burned areas that aim to include: (i) fire-induced changes in soil and ground cover; (ii) fire-induced changes in infiltration; (iii) burn severity; and (iv) mitigation measures in their predictions. This study also discusses the strengths and weaknesses of these approaches, suggests potential improvements, and identifies directions for future research. Results show that studies are not homogeneously distributed worldwide, according to the model type used or by region most affected by wildfire. During calibration, 73% of cases involved model adaptation to burned conditions, and only 21% attempted to accommodate new processes. Burn severity was addressed in 75% of cases, whilst mitigation measures were simulated in 27%. Additionally, only a minor percentage of model predictions were validated with independent field data (17%) or assessed for uncertainties (13%). Therefore, further efforts are required in the adaptation of erosion models to burned conditions, to be widely used for post-fire management decisions. © 2020 John Wiley & Sons, Ltd. 相似文献