全文获取类型
收费全文 | 956篇 |
免费 | 60篇 |
国内免费 | 14篇 |
专业分类
测绘学 | 33篇 |
大气科学 | 65篇 |
地球物理 | 311篇 |
地质学 | 336篇 |
海洋学 | 63篇 |
天文学 | 155篇 |
综合类 | 5篇 |
自然地理 | 62篇 |
出版年
2023年 | 5篇 |
2022年 | 23篇 |
2021年 | 14篇 |
2020年 | 27篇 |
2019年 | 22篇 |
2018年 | 47篇 |
2017年 | 48篇 |
2016年 | 51篇 |
2015年 | 52篇 |
2014年 | 65篇 |
2013年 | 64篇 |
2012年 | 63篇 |
2011年 | 62篇 |
2010年 | 61篇 |
2009年 | 80篇 |
2008年 | 57篇 |
2007年 | 43篇 |
2006年 | 30篇 |
2005年 | 38篇 |
2004年 | 25篇 |
2003年 | 28篇 |
2002年 | 26篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1992年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1969年 | 3篇 |
排序方式: 共有1030条查询结果,搜索用时 31 毫秒
961.
We present a new visualization method for human inspection of seismic data called supersonograms, which maximizes the amount of time and stations visible on screen while retaining the possibility to detect short and low-signal to noise ratio (SNR) signals. This visualization approach is integrated into a seismological software suite used in the seismic aftershock monitoring system (SAMS) of Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) on-site inspections (OSI) to detect suspicious events eventually representing aftershocks from an underground nuclear explosion (UNE). During an OSI, huge amounts of continuous waveform data accumulate from up to 50 six-channel mini-arrays covering an inspection area of 1,000 square kilometers. Sought-after events can have magnitude as low as $\hbox{M}_{\rm L}\,{-2.0}$ and duration of just a few seconds, which makes it particularly hard to discover them in large, noisy datasets. Therefore, the data visualization is based on nonlinearly scaled, noise-adapted spectrograms, i.e., sonograms, which help to distinguish weak signal energy from stationary background noise. Four single-trace sonograms per mini-array can be combined into supersonograms, since the array aperture is small and sonograms suppress differences of local site noise, allowing an analyst to check array-wide signal coherence quickly. In this paper, we present the supersonograms and the software on the basis of a dataset from a creeping, inhabited landslide in Austria where the same station layout is used as in an OSI. Detected signals are fracture processes in the sedimentary landslide, i.e., slidequakes, with $\hbox{M}_{\rm L}\,{-0.5} \,\hbox{\,to}\,{-2.5}$ between July 2009 and July 2011. These signals are comparable in magnitude and duration to expected weak UNE aftershocks. 相似文献
962.
Efthymios I. Nikolopoulos Marco Borga Davide Zoccatelli Emmanouil N. Anagnostou 《水文科学杂志》2014,59(7):1363-1376
AbstractThe concept of “catchment-scale storm velocity” quantifies the rate of storm motion up and down the basin accounting for the interaction between the rainfall space–time variability and the structure of the drainage network. It provides an assessment of the impact of storm motion on flood shape. We evaluate the catchment-scale storm velocity for the 29 August 2003 extreme storm that occurred on the 700 km2-wide Fella River basin in the eastern Italian Alps. The storm was characterized by the high rate of motion of convective cells across the basin. Analysis is carried out for a set of basins that range in area from 8 to 623 km2 to: (a) determine velocity magnitudes for different sub-basins; (b) examine the relationship of velocity with basin scale and (c) assess the impact of storm motion on simulated flood response. Two spatially distributed hydrological models of varying degree of complexity in the representation of the runoff generation processes are used to evaluate the effects of the storm velocity on flood modelling and investigate model dependencies of the results. It is shown that catchment-scale storm velocity has a non-linear dependence on basin scale and generally exhibits rather moderate values, in spite of the strong kinematic characteristics of individual storm elements. Consistently with these observations and for both models, hydrological simulations show that storm motion has an almost negligible effect on the flood response modelling.Editor Z.W. Kundzewicz; Guest editor R.J. MooreCitation Nikolopoulos, E.I., Borga, M., Zoccatelli, D., and Anagnostou, E.N., 2014. Catchment-scale storm velocity: quantification, scale dependence and effect on flood response. Hydrological Sciences Journal, 59 (7), 1363–1376. http://dx.doi.org/10.1080/02626667.2014.923889 相似文献
963.
An integrated approach for investigating geomorphic response to extreme events: methodological framework and application to the October 2011 flood in the Magra River catchment,Italy
下载免费PDF全文
![点击此处可从《地球表面变化过程与地形》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Massimo Rinaldi William Amponsah Marco Benvenuti Marco Borga Francesco Comiti Ana Lucía Lorenzo Marchi Laura Nardi Margherita Righini Nicola Surian 《地球表面变化过程与地形》2016,41(6):835-846
A high‐magnitude flash flood, which took place on 25 October 2011 in the Magra River catchment (1717 km2), central‐northern Italy, is used to illustrate some aspects of the geomorphic response to the flood. An overall methodological framework is described for using interlinked observations and analyses of the geomorphic impacts of an extreme event. The following methods and analyses were carried out: (i) hydrological and hydraulic analysis of the event; (ii) sediment delivery by event landslide mapping; (iii) identification and estimation of wood recruitment, deposition, and budgeting; (iv) interpretation of morphological processes by analysing fluvial deposits; (v) remote sensing and geographic information system (GIS) analysis of channel width changes. In response to the high‐magnitude hydrological event, a large number of landslides occurred, consisting of earth flows, soil slips, and translational slides, and a large quantity of wood was recruited, in most part deriving from floodplain erosion caused by bank retreat and channel widening. The most important impact of the flood event within the valley floor was an impressive widening of the overall channel bed and the reactivation of wide portions of the pre‐event floodplain. Along the investigated (unconfined or partly confined) streams (total investigated length of 93.5 km), the channel width after the flood was up to about 20 times the channel width before the event. The study has shown that a synergic use of different methods and types of evidence provides fundamental information for characterizing and understanding the geomorphic effects of intense flood events. The prediction of geomorphic response to a flood event is still challenging and many limitations exist; however a robust geomorphological analysis can contribute to the identification of the most critical reaches. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
964.
Sensitivity of simulated flow fields and bathymetries in meandering channels to the choice of a morphodynamic model
下载免费PDF全文
![点击此处可从《地球表面变化过程与地形》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Morphodynamic models are used by river practitioners and scientists to simulate geomorphic change in natural and artificial river channels. It has long been recognized that these models are sensitive to the choice of parameter values, and proper calibration is now common practice. This paper investigates the less recognized impact of the choice of the model itself. All morphodynamic models purport to simulate the same flow and sediment dynamics, often relying on the same governing equations. Yet in solving these equations, the models have different underlying assumptions, for example regarding spatial discretization, turbulence, sediment inflow, lateral friction, and bed load transport. These differences are not always considered by the average model user, who might expect similar predictions from calibrated models. Here, a series of numerical simulations in meandering channels was undertaken to test whether six morphodynamic codes (BASEMENT, CCHE‐2D, NAYS, SSIIM‐1, TELEMAC‐2D and TELEMAC‐3D) would yield significantly different equilibrium bathymetries if subjected to identical, initial flow conditions. We found that, despite producing moderately similar velocity patterns on a fixed‐flat bed (regression coefficient r of 0.77 ± 0.20), the codes disagree substantially with respect to simulated bathymetries (r = 0.49 ± 0.31). We relate these discrepancies to differences in the codes' assumptions. Results were configuration specific, i.e. codes that perform well for a given channel configuration do not necessarily perform well with higher or lower sinuosity configurations. Finally, limited correlation is found between accuracy and code complexity; the inclusion of algorithms that explicitly account for the effects of local bed slope and channel curvature effects on transport magnitude and direction does not guarantee accuracy. The range of solutions obtained from the evaluated codes emphasizes the need for carefully considering the choice of code. We recommend the creation of a central repository providing universal validation cases and documentation of recognized fluvial codes in commonly studied fluvial settings. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
965.
David Vincent Özgur Karatekin Valentin Vallaeys Alexander G. Hayes Marco Mastrogiuseppe Claudia Notarnicola Véronique Dehant Eric Deleersnijder 《Ocean Dynamics》2016,66(4):461-482
In the context of the emergence of extra-terrestrial oceanography, we adapted an existing oceanographic model, SLIM (www.climate.be/slim), to the conditions of Titan, a moon of Saturn. The tidal response of the largest southern lake at Titan’s surface, namely Ontario Lacus, is simulated. SLIM solves the 2D, depth-averaged shallow water equations on an unstructured mesh using the discontinuous Galerkin finite element method, which allows for high spatial resolution wherever needed. The impact of the wind forcing, the bathymetry, and the bottom friction is also discussed. The predicted maximum tidal range is about 0.56 m in the southern part of the lake, which is more than twice as large as the previous estimates (see Tokano, Ocean Dyn 60:(4) 803–817 10.1007/s10236-010-0285-3 (Tokano 2010)). The patterns and magnitude of the current are also markedly different from those of previous studies: the tidal motion is not aligned with the major axis of the lake and the speed is larger nearshore. Indeed, the main tidal component rotates clockwise in an exact period of one Titan day and the tidal currents can reach 0.046 ms ?1 close to the shores depending on the geometry and the bathymetry. Except for these specific nearshore regions, the current speed is less than 0.02 ms ?1. Circular patterns can be observed offshore, their rotational direction and size varying along the day. 相似文献
966.
Building damage scenarios based on exploitation of Housner intensity derived from finite faults ground motion simulations 总被引:2,自引:2,他引:0
Leonardo Chiauzzi Angelo Masi Marco Mucciarelli Marco Vona Francesca Pacor Giovanna Cultrera Frantisek Gallovič Antonio Emolo 《Bulletin of Earthquake Engineering》2012,10(2):517-545
In this paper earthquake damage scenarios for residential buildings (about 4200 units) in Potenza (Southern Italy) have been
estimated adopting a novel probabilistic approach that involves complex source models, site effects, building vulnerability
assessment and damage estimation through Damage Probability Matrices. Several causative faults of single seismic events, with
magnitude up to 7, are known to be close to the town. A seismic hazard approach based on finite faults ground motion simulation
techniques has been used to identify the sources producing the maximum expected ground motion at Potenza and to generate a
set of ground motion time histories to be adopted for building damage scenarios. Additionally, site effects, evaluated in
a previous work through amplification factors of Housner intensity, have been combined with the bedrock values provided by
hazard assessment. Furthermore, a new relationship between Housner and EMS-98 macroseismic intensity has been developed. This
relationship has been used to convert the probability mass functions of Housner intensity obtained from synthetic seismograms
amplified by the site effects coefficients into probability mass function of EMS-98 intensity. Finally, the Damage Probability
Matrices have been applied to estimate the damage levels of the residential buildings located in the urban area of Potenza.
The proposed methodology returns the full probabilistic distribution of expected damage, thus avoiding average damage index
or uncertainties expressed in term of dispersion indexes. 相似文献
967.
The paper presents the main characteristics of an innovative platform which has been conceived and designed to extend the
operational capabilities of current unmanned surface vehicles in terms of platform stability in waves and of powering requirement
at a relatively high speed. The main idea which rules the project is the realization of a small autonomous surface unit (about
6 m in length) capable of undertaking several tasks in the marine environment even with moderate rough sea conditions. The
designed vessel has the ability to locate, recover, and launch other members of the autonomous fleet (like AUVs or other underwater
devices) and at the same time could carry out a surveillance service of the surrounding areas. To manage these tasks, the
vehicle is designed to provide a fairly good autonomy which is needed to face intermediate-range missions (100 nautical miles).
The choice of a small waterplane area twin hull (SWATH) form has been motivated by its excellent properties of seakeeping
qualities, combined with a non-conventional low resistance underwater hull shape, currently under patenting process, which
is able to reduce to a minimum the resistance of the vessel especially at higher speeds. To obtain the most efficient profile
of the underwater bodies, a systematic optimization with an automatic procedure based on a parametric definition of the geometry,
a state-of-the-art computational fluid dynamics (CFD) flow solver, and a differential evolution global minimization algorithm
have been created and used. As expected, all the final CFD computations on the best design have demonstrated the superior
efficiency of the developed unconventional SWATH technology with respect to different alternatives of current hull typologies. 相似文献
968.
969.
Flow and transport in channels with submerged vegetation 总被引:3,自引:0,他引:3
This paper reviews recent work on flow and transport in channels with submerged vegetation, including discussions of turbulence
structure, mean velocity profiles, and dispersion. For submerged canopies of sufficient density, the dominant characteristic
of the flow is the generation of a shear-layer at the top of the canopy. The shear-layer generates coherent vortices by Kelvin-Helmholtz
(KH) instability. These vortices control the vertical exchange of mass and momentum, influencing both the mean velocity profile,
as well as the turbulent diffusivity. For flexible canopies, the passage of the KH vortices generates a progressive wave along
the canopy interface, termed monami. The KH vortices formed at the top of the canopy penetrate a distance δ
e
into the canopy. This penetration scale segregates the canopy into an upper layer of rapid transport and a lower layer of
slow transport. Flushing of the upper canopy is enhanced by the energetic shear-scale vortices. In the lower layer turbulence
is limited to length-scales set by the stem geometry, and the resulting transport is significantly slower than that of the
upper layer. 相似文献
970.
Body-wave Attenuation in the Region of Garda, Italy 总被引:1,自引:0,他引:1
Raúl R. Castro Marco Massa Paolo Augliera Francesca Pacor 《Pure and Applied Geophysics》2008,165(7):1351-1366
We analyzed the spectral amplitude decay with hypocentral distance of P and S waves generated by 76 small magnitude earthquakes (ML 0.9–3.8) located in the Garda region, Central-Eastern Alps, Italy. These events were recorded by 18 stations with velocity
sensors, in a distance range between 8 and 120 km. We calculated nonparametric attenuation functions (NAF) and estimated the
quality factor Q of both body waves at 17 different frequencies between 2 and 25 Hz. Assuming a homogeneous model we found that the Q frequency dependence of P and S can be approximated with the functions Q
P
= 65 f
0.9
and Q
S
= 160 f
0.6
, respectively. At 2 Hz the Q
S
/Q
P
ratio reaches the highest value of 2.8. At higher frequencies Q
S
/Q
P
varies between 0.7 and 1.7, suggesting that for this frequency band scattering may be an important attenuation mechanism
in the region of Garda. To explore the variation of Q in depth, we estimated Q at short (r ≤ 30 km) and intermediate (35–90 km) distance paths. We found that in the shallow crust P waves attenuate more than S (1.3 < Q
S
/Q
P
< 2.5). Moreover, P waves traveling along paths in the lower crust (depths approximately greater than 30 km) attenuate more than S waves. To quantify the observed variability of Q in depth we considered a three-layer model and inverted the NAF to estimate Q in each layer. We found that in the crust Q increases with depth. However, in the upper mantle (~40–50 km depth) Q decreases and in particular the high frequency Q
S
(f > 9 Hz) has values similar to those estimated for the shallow layer of the crust. 相似文献