全文获取类型
收费全文 | 307篇 |
免费 | 24篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 30篇 |
地球物理 | 99篇 |
地质学 | 121篇 |
海洋学 | 26篇 |
天文学 | 37篇 |
综合类 | 1篇 |
自然地理 | 20篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 26篇 |
2017年 | 12篇 |
2016年 | 24篇 |
2015年 | 15篇 |
2014年 | 23篇 |
2013年 | 20篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 17篇 |
2009年 | 27篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 8篇 |
2005年 | 15篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1985年 | 3篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有338条查询结果,搜索用时 15 毫秒
141.
Fulong Chen Nicola Masini Jie Liu Jiangbin You Rosa Lasaponara 《International Journal of Digital Earth》2016,9(12):1224-1241
Synthetic Aperture Radar (SAR) remote sensing is increasingly favoured in archaeological applications. However, the effectiveness of this technology for archaeological prospection has so far not been fully assessed. In this study, an integrated single-date and multi-temporal SAR data-processing chain was proposed to sharpen archaeological signs and hence their detection and monitoring. In total, 14 scenes of X-band Cosmo-SkyMed, C-band Sentinel-1 and L-band PALSAR data covering the Western Regions of the Silk Road Corridor in China were employed for two important archaeological sites including the Yumen Frontier Pass with emerging archaeological traces and Niya ruins with subsurface remains. The results pointed out that single-date satellite radar data were useful for the identification of subsurface traces buried under desert in the landscape-scale, whereas for the identification of emerging monuments, Sentinel-1 was limited by its lower spatial resolution compared to TerraSAR and PALSAR data. Multi-date products, such as interferometric coherence, the averaged radar signatures and RGB multi-temporal composites, were effective to sharpen archaeological traces as well as for change detection in Yumen Frontier Pass. This study presents a pilot assessment of satellite SAR data for the analysis and monitoring of archaeological features in the predominantly arid-sandy environmental characteristic of investigated sites. 相似文献
142.
The first use of Fulton's K for assessing and comparing the conditions of inter‐tidal fish populations
下载免费PDF全文
![点击此处可从《Marine Ecology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fulton's K condition factor was applied, for the first time, to inter‐tidal specimens of the shanny (Lipophrys pholis) and long‐spined scorpion fish (Taurulus bubalis) from two English rocky shore and two Welsh rocky shore sites during summer 2010 and winter 2011. As both species contribute to the diet of commercial species such as cod (Gadus morhua) and near‐threatened species such as the European otter (Lutra lutra), their condition may affect that of these predators. Fulton's K found that inter‐tidal Welsh fish maintained a ‘good’ condition between seasons, whereas the inter‐tidal English fish were in a poorer condition during winter. Although condition also changed amongst the sites on each coast, further studies are needed into fish morphologies, environmental parameters, prey availabilities and abundances, and fish specimen sex and maturities. 相似文献
143.
The aim of this paper was to provide a significant case‐history concerning the evolution of a segmented system of extensional faults and related basins, investigated by a set of seismic reflection profiles. We investigated two kinematically linked semi‐grabens, developed at the hangingwall of two opposite‐dipping normal faults: the Vallo di Diano and Auletta basins, located in the southern Apennines, one of the most seismically active regions of the Italian peninsula. Our interpretation suggests that the Pliocene–Quaternary tectonic history consists of a single extensional phase, where the major NW–SE trending normal faults, generating the basins, and the strike‐slip and transtensional faults connecting adjacent normal fault segments, simultaneously act, being part of the same extensional system. We also conclude that major normal faults, bordering the basins, should be considered as potential seismogenic sources in the seismic hazard evaluation. 相似文献
144.
Pandara V. Femeena Indrajeet Chaubey Antoine Aubeneau Sara K. McMillan Paul D. Wagner Nicola Fohrer 《水文研究》2020,34(11):2599-2611
Hydrological models have long been used to study the interactions between land, surface and groundwater systems, and to predict and manage water quantity and quality. The soil and water assessment tool (SWAT), a widely used hydrological model, can simulate various ecohydrological processes on land and subsequently route the water quality constituents through surface and subsurface waters. So far, in-stream solute transport algorithms of the SWAT model have only been minimally revised, even though it has been acknowledged that an improvement of in-stream process representation can contribute to better model performance with respect to water quality. In this study, we aim to incorporate a new and improved solute transport model into the SWAT model framework. The new process-based model was developed using in-stream process equations from two well established models—the One-dimensional Transport with Inflow and Storage model and the Enhanced Stream Water Quality Model. The modified SWAT model (Mir-SWAT) was tested for water quality predictions in a study watershed in Germany. Compared to the standard SWAT model, Mir-SWAT improved dissolved oxygen (DO) predictions by removing extreme low values of DO (<6 mg/L) simulated by SWAT. Phosphate concentration peaks were reduced during high flows and a better match of daily predicted and measured values was attained using the Mir-SWAT model (R2 = 0.17, NSE = −0.65, RSR = 1.29 with SWAT; R2 = 0.28, NSE = −0.04, RSR = 1.02 with Mir-SWAT). In addition, Mir-SWAT performed better than the SWAT model in terms of Chlorophyll-a content particularly during winter months, improving the NSE and RSR for monthly average Chl-a by 74 and 42%, respectively. With the new model improvements, we aim to increase confidence in the stream solute transport component of the model, improve the understanding of nutrient dynamics in the stream, and to extend the applicability of SWAT for reach-scale analysis and management. 相似文献
145.
146.
Cecilia T. Satta Sílvia Anglès Esther Garcés Nicola Sechi Silvia Pulina Bachisio Mario Padedda Daniela Stacca Antonella Lugliè 《Estuaries and Coasts》2014,37(3):646-663
The present study identified and quantified dinoflagellate cysts in surface sediments from three Mediterranean lagoons. Sediment samples were recovered from 11 stations in May 2009 at Cabras Lagoon, eight stations in May 2010 at Corru S'Ittiri Lagoon, and five stations in May 2011 at Santa Giusta Lagoon. Fifty-three dinoflagellate cyst morphotypes were identified. Sixteen species are first reports for the lagoons, and two for the Mediterranean Sea. Moreover, a new Scrippsiella species was discovered in Cabras. Seven harmful algal species were identified, primarily belonging to the potentially toxic genus Alexandrium. Total cyst abundance, number of morphotypes, and assemblages varied among lagoons, and each lagoon showed a distinct morphotype composition. A degree of heterogeneity was also detected within lagoon. Cabras and Santa Giusta cyst assemblages were characterised by morphotypes belonging to the autotrophic genus Scrippsiella, whereas Corru S'Ittiri assemblages showed dominance of heterotrophic morphotypes, including Protoperidinium cf tricingulatum. Differentiation among lagoons was also evident according to environmental conditions. Salinity proved to be a fundamental variable in determining total cyst abundance, morphotype number, and composition. This study was among the first to examine dinoflagellate cyst composition in coastal lagoons, especially from the Mediterranean region, and contributed data that increased our knowledge of cyst-producing dinoflagellates in these environments. 相似文献
147.
Jiacong Huang Junfeng Gao Georg Hörmann Nicola Fohrer 《Environmental Earth Sciences》2014,72(9):3609-3621
Understanding the short-term response of phytoplankton biomass on environmental variables is needed for issuing early warnings of harmful algal blooms in aquatic ecosystems. Predicting harmful algal blooms are particularly challenging in large shallow lakes due to their complex mixing patterns. This study used a two-dimensional hydrodynamic–phytoplankton model to evaluate the effects of environmental variables on short-term changes in the horizontal distribution of phytoplankton biomass in a large shallow lake, Lake Taihu, China. Two simulations were performed using daily and hourly average wind condition and water temperature data collected in 2009. Other model inputs were identical for these two simulations. The response of phytoplankton to wind conditions, light intensity, water temperature, and total dissolved phosphorus and nitrogen concentrations were examined based on a sensitivity analysis using the hourly data. Hourly simulation achieved a more realistic distribution of phytoplankton biomass than the daily simulation. This finding implies that data with a higher temporal resolution are more useful for short-term prediction of phytoplankton biomass in this lake. Sensitivity analysis indicated that water temperature and light intensity dominate short-term changes in phytoplankton biomass in this lake. Wind conditions also affect phytoplankton biomass distribution by causing advective water movement. 相似文献
148.
149.
Ivan Valtchanov Rosalind Hopwood Edward Polehampton Dominique Benielli Trevor Fulton Peter Imhof Tomasz Konopczyński Tanya Lim Nanyao Lu Nicola Marchili David Naylor Bruce Swinyard 《Experimental Astronomy》2014,37(2):207-223
We present a method to derive the relative pointing offsets for SPIRE Fourier-Transform Spectrometer (FTS) solar system object (SSO) calibration targets, which were observed regularly throughout the Herschel mission. We construct ratios R obs(ν) of the spectra for all observations of a given source with respect to a reference. The reference observation is selected iteratively to be the one with the highest observed continuum. Assuming that any pointing offset leads to an overall shift of the continuum level, then these R obs(ν) represent the relative flux loss due to mispointing. The mispointing effects are more pronounced for a smaller beam, so we consider only the FTS short wavelength array (SSW, 958–1546 GHz) to derive a pointing correction. We obtain the relative pointing offset by comparing R obs(ν) to a grid of expected losses for a model source at different distances from the centre of the beam, under the assumption that the SSW FTS beam can be well approximated by a Gaussian. In order to avoid dependency on the point source flux conversion, which uses a particular observation of Uranus, we use extended source flux calibrated spectra to construct R obs(ν) for the SSOs. In order to account for continuum variability, due to the changing distance from the Herschel telescope, the SSO ratios are normalised by the expected model ratios for the corresponding observing epoch. We confirm the accuracy of the derived pointing offset by comparing the results with a number of control observations, where the actual pointing of Herschel is known with good precision. Using the method we derived pointing offsets for repeated observations of Uranus (including observations centred on off-axis detectors), Neptune, Ceres and NGC 7027. The results are used to validate and improve the point-source flux calibration of the FTS. 相似文献
150.
Semi-active control of the benchmark highway bridge based on seismic early warning systems 总被引:1,自引:1,他引:0
Giuseppe Maddaloni Nicola Caterino Antonio Occhiuzzi 《Bulletin of Earthquake Engineering》2011,9(5):1703-1715
Possible interactions between seismic early warning systems and structural control are herein investigated. A SEWS can provide
the knowledge of some parameters, ahead of time, of the seismic event that is going to occur in a certain site. Current research
activities on SEWS include the estimate of the anticipated peak ground acceleration (PGA) and the acceleration response spectrum
(Sa) of an incoming earthquake. This paper proposes the exploitation of this information in the framework of semi-active (SA)
control strategies, by using magnetorheological dampers. The latter are time-varying properties devices able to achieve a
wide range of physical behaviours using low-power electrical currents. The main idea of this work consists in changing the
MR damper behaviour according to the forecasted intensity of an incoming earthquake provided by the SEWS, in order to obtain
the optimal seismic response of the hosting structure. This is investigated assuming a case-study problem. It consists in
the 91/5 highway bridge located in Orange County of southern California and proposed in literature as a benchmark structure
for applications in the field of structural control. The effectiveness of the proposed control strategy is assessed and compared
to more consolidated control techniques. 相似文献