全文获取类型
| 收费全文 | 184篇 |
| 免费 | 22篇 |
| 国内免费 | 1篇 |
专业分类
| 测绘学 | 9篇 |
| 大气科学 | 7篇 |
| 地球物理 | 95篇 |
| 地质学 | 48篇 |
| 海洋学 | 14篇 |
| 天文学 | 30篇 |
| 自然地理 | 4篇 |
出版年
| 2023年 | 1篇 |
| 2022年 | 5篇 |
| 2021年 | 6篇 |
| 2020年 | 8篇 |
| 2019年 | 3篇 |
| 2018年 | 11篇 |
| 2017年 | 6篇 |
| 2016年 | 12篇 |
| 2015年 | 13篇 |
| 2014年 | 10篇 |
| 2013年 | 19篇 |
| 2012年 | 11篇 |
| 2011年 | 15篇 |
| 2010年 | 12篇 |
| 2009年 | 17篇 |
| 2008年 | 10篇 |
| 2007年 | 6篇 |
| 2006年 | 9篇 |
| 2005年 | 6篇 |
| 2004年 | 1篇 |
| 2003年 | 2篇 |
| 2002年 | 5篇 |
| 2001年 | 3篇 |
| 2000年 | 1篇 |
| 1999年 | 2篇 |
| 1998年 | 2篇 |
| 1996年 | 2篇 |
| 1995年 | 1篇 |
| 1993年 | 1篇 |
| 1992年 | 2篇 |
| 1990年 | 2篇 |
| 1983年 | 2篇 |
| 1980年 | 1篇 |
排序方式： 共有207条查询结果，搜索用时 499 毫秒
81.
Performance of intertidal topography video monitoring of a meso-tidal reflective beach in South Portugal 总被引：2，自引：1，他引：1
Michalis Ioannis Vousdoukas Pedro Manuel Ferreira Luis Pedro Almeida Guillaume Dodet Fotis Psaros Umberto Andriolo Rui Taborda Ana Nobre Silva Antonio Ruano Óscar Manuel Ferreira 《Ocean Dynamics》2011,61(10):1521-1540
This study discusses site-specific system optimization efforts related to the capability of a coastal video station to monitor
intertidal topography. The system consists of two video cameras connected to a PC, and is operating at the meso-tidal, reflective
Faro Beach (Algarve coast, S. Portugal). Measurements from the period February 4, 2009 to May 30, 2010 are discussed in this
study. Shoreline detection was based on the processing of variance images, considering pixel intensity thresholds for feature
extraction, provided by a specially trained artificial neural network (ANN). The obtained shoreline data return rate was 83%,
with an average horizontal cross-shore root mean square error (RMSE) of 1.06 m. Several empirical parameterizations and ANN
models were tested to estimate the elevations of shoreline contours, using wave and tidal data. Using a manually validated
shoreline set, the lowest RMSE (0.18 m) for the vertical elevation was obtained using an ANN while empirical parameterizations
based on the tidal elevation and wave run-up height resulted in an RMSE of 0.26 m. These errors were reduced to 0.22 m after
applying 3-D data filtering and interpolation of the topographic information generated for each tidal cycle. Average beach-face
slope tan(β) RMSE were around 0.02. Tests for a 5-month period of fully automated operation applying the ANN model resulted in an optimal,
average, vertical elevation RMSE of 0.22 m, obtained using a one tidal cycle time window and a time-varying beach-face slope.
The findings indicate that the use of an ANN in such systems has considerable potential, especially for sites where long-term
field data allow efficient training. 相似文献
82.
Areti Gianni Miltiadis Zamparas Ioannis T. Papadas George Kehayias Yiannis Deligiannakis Ierotheos Zacharias 《Aquatic Geochemistry》2013,19(1):77-95
The balance between physicochemical processes, influencing vertical and temporal distributions of metal compounds in one relatively isolated anoxic environment, constitutes the objective of the present work. Ion activity product (IAP) was calculated for manganese and iron sulfides, in order to define the metal sulfide forms that control Fe and Mn solubility in the bottom waters of anoxic lagoons. Iron solubility depended on amorphous FeS formation, while manganese sulfides were a minor component in a solid solution lowering its solid-phase activity. A theoretical physicochemical model was developed for the iron speciation, based on experimental pH and redox potential data. A very good match was achieved for the measured and the theoretical total dissolved iron, at all depths. The dominance of oxidant iron species Fe(OH) 3 ? in the surface waters and their sequence by FeSH+ and FeSaq in the deeper layers brings out the influence of physicochemical parameters (dissolved oxygen, sulfide, pH and Eh) in vertical distribution of dissolved metal species, in anoxic/hypoxic basins. Based on these findings, we can conclude that the distribution of manganese and iron is of special interest, not only because these are the indicators of redox conditions but also for the role of their oxidized/reduced forms in the formation of the biogeochemical structure of redox zone. 相似文献
83.
Ioannis N. Daliakopoulos 《水文科学杂志》2013,58(15):2763-2774
ABSTRACTThe rainfall–runoff process is governed by parameters that can seldom be measured directly for use with distributed models, but are rather inferred by expert judgment and calibrated against historical records. Here, a comparison is made between a conceptual model (CM) and an artificial neural network (ANN) for their ability to efficiently model complex hydrological processes. The Sacramento soil moisture accounting model (SAC-SMA) is calibrated using a scheme based on genetic algorithms and an input delay neural network (IDNN) is trained for variable delays and hidden layer neurons which are thoroughly discussed. The models are tested for 15 ephemeral catchments in Crete, Greece, using monthly rainfall, streamflow and potential evapotranspiration input. SAC-SMA performs well for most basins and acceptably for the entire sample with R2 of 0.59–0.92, while scoring better for high than low flows. For the entire dataset, the IDNN improves simulation fit to R2 of 0.70–0.96 and performs better for high flows while being outmatched in low flows. Results show that the ANN models can be superior to the conventional CMs, as parameter sensitivity is unclear, but CMs may be more robust in extrapolating beyond historical record limits and scenario building.
EDITOR M.C. Acreman; ASSOCIATE EDITOR not assigned 相似文献
84.
In this paper we examine the recently introduced Dvali-Gabadadze-Porrati (DGP) gravity model. We use a space-time metric in which the local gravitation source dominates the metric over the contributions from the cosmological flow. Anticipating ideal possible solar system effects, we derive expressions for the signal time delays in the vicinity of the Sun. and for various ranges of the angle θ of the signal approach, The time contribution due to DGP correction to the metric is found to be proportional to b 3/2/c 2 r 0. For r 0 equal to 5 Mpc and θ in the range [−π/3,π/3], Δt is equal to 0.0001233 ps. This delay is extremely small to be measured by today’s technology but it could be probably measurable by future experiments. 相似文献
85.
Ioannis Gidaris Alexandros A. Taflanidis Diego Lopez‐Garcia George P. Mavroeidis 《地震工程与结构动力学》2016,45(8):1293-1313
The design of floor isolation systems (FISs) for the protection of acceleration sensitive contents is examined considering multiple objectives, all quantified in terms of the probabilistic system performance. The competing objectives considered correspond to (i) maximization of the level of protection offered to the sensitive content (acceleration reduction) and (ii) minimization of the demand for the isolator displacement capacity and, more importantly, for the appropriate clearance to avoid collisions with surrounding objects (floor displacement reduction). Both of these objectives are probabilistically characterized utilizing a versatile, simulation‐based framework for quantifying seismic risk, addressing all important uncertainties related to the seismic hazard and the structural model. FIS performance is assessed through time‐history analysis, allowing for all important sources of nonlinearity to be directly addressed in the design framework. The seismic hazard is described through a stochastic ground motion model. For efficiently performing the multi‐objective optimization, an augmented surrogate modeling methodology is established, considering development of a single metamodel with respect to both the uncertain model parameters and the design variables for the FIS system. This surrogate model is then utilized to simultaneously support the probabilistic risk assessment and the design optimization to provide the Pareto front of dominant designs. Each of these designs establishes a different compromise between the considered risk‐related objectives offering a variety of potential options to the designer. Within the illustrative example, the efficiency of the established framework is exploited to compare three different FIS implementations, whereas the impact of structural uncertainties on the optimal design is also evaluated. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
86.
Stavroula Stolaki Ioannis Pytharoulis Theodore Karacostas 《Pure and Applied Geophysics》2012,169(5-6):961-981
An attempt is made to couple the one dimensional COBEL-ISBA (Code de Brouillard à l’échelle Locale-Interactions Soil Biosphere Atmosphere) model with the WRF (Weather Research and Forecasting)–ARW (Advanced Research WRF) numerical weather prediction model to study a fog event that formed on 20 January 2008 over Thessaloniki Airport, Greece. It is the first time that the coupling of COBEL and WRF models is achieved and applied to a fog event over an airport. At first, the performance of the integrated WRF–COBEL system is investigated, by validating it against the available surface observations. The temperature and humidity vertical profiles were used for initializing the model. The performance of WRF–COBEL is considered successful, since it realistically simulated the fog onset and dissipation better than the WRF alone. The COBEL’s sensitivity to initial conditions such as temperature and specific humidity perturbations was also tested. It is found that a small increase of temperature (~1°C) counteracts fog development and results in less fog density. On the other hand, a small decrease of temperature results in much denser fog formation. It is concluded that the integrated model approach for aviation applications can be useful to study fog impact on local traffic and aviation. 相似文献
87.
Christos Makris Panagiota Galiatsatou Konstantia Tolika Christina Anagnostopoulou Katerina Kombiadou Panayotis Prinos Kondylia Velikou Zacharias Kapelonis Elina Tragou Yannis Androulidakis Gerasimos Athanassoulis Christos Vagenas Ioannis Tegoulias Vassilis Baltikas Yannis Krestenitis Theodoros Gerostathis Kostantinos Belibassakis Eugen Rusu 《Ocean Dynamics》2016,66(12):1603-1635
88.
This paper deals with the use, for seismic applications, of a Maxwell element in parallel with a low damping isolator. The study of the properties of the frequency response function shows that this isolator is capable to reduce the base displacement of isolated structures with no considerable amplification of the non‐isolated modes. This is, also, confirmed by the floor response spectra under earthquake excitations. Hence, the previously mentioned isolator does not present the drawbacks met when base displacement is reduced by increasing damping. Moreover, it seems that its performance is comparable with that of more elaborated and expensive techniques combining passive and semi‐active devices. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
89.
Behavior of rigid blocks with geometrical defects under seismic motion: an experimental and numerical study 
下载免费PDF全文
下载免费PDF全文 Charlie Mathey Cyril Feau Ioannis Politopoulos David Clair Laurent Baillet Michel Fogli 《地震工程与结构动力学》2016,45(15):2455-2474
The present work investigates the influence of small geometrical defects on the behavior of slender rigid blocks. A comprehensive experimental campaign was carried out on one of the shake tables of CEA/Saclay in France. The tested model was a massive steel block with standard manufacturing quality. Release, free oscillations tests as well as shake table tests revealed a non‐negligible out‐of‐plane motion even in the case of apparently plane initial conditions or excitations. This motion exhibits a highly reproducible part for a short duration that was used to calibrate a numerical geometrically asymmetrical model. The stability of this model when subjected to 2000 artificial seismic horizontal bidirectional signals was compared with the stability of a symmetrical one. This study showed that the geometrical imperfections slightly increase the rocking and overturning probabilities for earthquake signals in a narrow range of peak ground acceleration. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
90.