全文获取类型
收费全文 | 122篇 |
免费 | 2篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 26篇 |
地球物理 | 13篇 |
地质学 | 36篇 |
海洋学 | 17篇 |
天文学 | 25篇 |
自然地理 | 5篇 |
出版年
2024年 | 3篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 2篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 12篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 171 毫秒
91.
92.
This paper contains three discoveries and observations of numbered asteroids observed in September and October 1984 at the ESO in La Silla. 相似文献
93.
de Freitas Pedro Paulo Amorim Felipe de Luca Lopes Mill Guilherme Nogueira da Costa Vladimir Santos Gabioux Mariela Cirano Mauro Paiva Afonso de Moraes 《Ocean Dynamics》2019,69(10):1203-1215
Ocean Dynamics - Near-inertial oscillations (NIO) are intermittent motions with a frequency close to the inertial frequency and represent an important fraction of the energy to the currents in the... 相似文献
94.
Ricardo Sousa Joana Vasconcelos Rodrigo Riera Joo Delgado Jos A. Gonzlez Mafalda Freitas Paulo Henriques 《Marine Ecology》2019,40(2)
Harvesting of intertidal grazers such as topshells is known to affect negatively the exploited populations by altering population structure and decreasing abundance. Phorcus sauciatus has a wide geographic distribution in the North‐eastern Atlantic Ocean and is subject to increasing levels of harvesting pressure due to the expansion of human population on coastal areas. The effect of proximity to human settlements and coastal accessibility on the size structure and abundance of P. sauciatus populations was examined in Madeira archipelago. Mean size, proportion of reproductive individuals, and abundance of this species were generally smaller in areas closer to human settlements and in more accessible coastal areas. Marine protected areas returned the highest mean sizes evidencing their effectiveness in preserving the size structure of this species. The results highlight the necessity to regulate the harvest of P. sauciatus in Madeira archipelago, as well as the implementation of management measures aiming at the sustainable exploitation and conservation of this species, exploited in this region since the early 15th century. 相似文献
95.
Victor Quintino Franca Sangiorgio Fernando Ricardo Renato Mamede Adília Pires Rosa Freitas Ana Maria Rodrigues Alberto Basset 《Estuarine, Coastal and Shelf Science》2009
An experimental study on Phragmites australis leaf litter decomposition was conducted in the estuarine environment, Ria de Aveiro, Western Portugal, using the leaf-bag technique, with fine- (1 mm) and coarse-mesh (5 mm) bags. The leaf bags were placed in the field sites at day 0, covering a complete salinity gradient, and replicates were collected over time, at days 3 (leaching), 7, 15, 30 and 60. The biomass loss through the leaching phase, about 20% of the initial leaf mass, was independent of both the salinity and the bag mesh size. The biomass decay pattern along the salinity gradient varied through time and presented strong similarities between the two mesh sizes, with the remaining biomass always lower in the 5 mm mesh-size bags. At days 7 and 15, the lowest remaining biomass was observed at the head of the estuary, the preferential distribution area of P. australis. At day 30, the remaining biomass was higher in the marine area and diminished under a direct relationship with salinity, reaching the lowest value in the freshwater environment, with values ranging from 66% to 44% of the initial weight in 5 mm bags, and from 79% to 51% in 1 mm bags. The largest heterogeneity in the remaining biomass among the study areas positioned along the salinity gradient was found close to days 30 (5 mm) and 40 (1 mm). The overall results indicate that the relationship between leaf decay rate and salinity depends on the decay time considered (k15, k30 or k60) and, for the later stages (k60), also on the leaf-bag mesh size. This implies that the use of leaf litter decay rates as a functional indicator in transitional waters will need to take into consideration the factor location in the salinity gradient and leaf litter stage at which the decay rate is determined. The differences between the decay rates with the mesh size acted mainly at the level of the absolute k value and not at the level of the pattern along the salinity gradient. Even so, the data obtained at the mouth of the estuary, in the area closest to a fully marine environment, indicated that after the initial biomass loss through leaching, P. australis decayed either very slowly, in the 5 mm, or not at all, in the 1 mm mesh bags. 相似文献
96.
Joana Campos Henk W. Van der Veer Vnia Freitas Sebastiaan A.L.M. Kooijman 《Journal of Sea Research》2009,62(2-3):106
In this paper a contribution is made to the ongoing debate on which brown shrimp generation mostly sustains the autumn peak in coastal North Sea commercial fisheries: the generation born in summer, or the winter one. Since the two perspectives are based on different considerations on the growth timeframe from settlement till commercial size, the Dynamic Energy Budget (DEB) theory was applied to predict maximum possible growth under natural conditions. First, the parameters of the standard DEB model for Crangon crangon L. were estimated using available data sets. These were insufficient to allow a direct estimation, requiring a special protocol to achieve consistency between parameters. Next, the DEB model was validated by comparing simulations with published experimental data on shrimp growth in relation to water temperatures. Finally, the DEB model was applied to simulate growth under optimal food conditions using the prevailing water temperature conditions in the Wadden Sea. Results show clear differences between males and females whereby the fastest growth rates were observed in females. DEB model simulations of maximum growth in the Wadden Sea suggest that it is not the summer brood from the current year as Boddeke claimed, nor the previous winter generation as Kuipers and Dapper suggested, but more likely the summer generation from the previous year which contributes to the bulk of the fisheries recruits in autumn. 相似文献
97.
Pedro J. M. Costa César Andrade Maria C. Freitas Maria A. Oliveira Carlos M. da Silva Rachid Omira Rui Taborda Maria A. Baptista Alastair G. Dawson 《地球表面变化过程与地形》2011,36(15):2054-2068
A remarkable accumulation of marine boulders located above the present spring tide level has occurred in two coastal lowlands of the Algarve (Portugal). The size‐interval of the particles studied here is seldom reported in the literature in association with extreme events of coastal inundation, thus making this study of relevance to many other coasts worldwide. The spreads of boulders extend several hundred meters inland and well beyond the present landward limit of storm activity. The marine origin of the boulders is demonstrated by well‐developed macro‐bioerosion sculpturing and in situ skeletal remains of endolithic shallow marine bivalves. The good state preservation of the fossils within the boulders indicates that abrasion during transport and redeposition was not significant. We envisage boulder deposition as having taken place during the Lisbon tsunami of ad 1755 through the simultaneous landward entrainment of coarse particles from nearshore followed by rapid shoreward suspended‐dominated transport and non‐graded redeposition that excluded significant sorting by weight or boulder dimensions. We use numerical hydrodynamic modeling of tsunami (and storm) waves to test the observational data on boulder dimensions (density, size, distribution) on the most likely processes of sediment deposition. This work demonstrates the effectiveness of the study of boulder deposits in tsunami reconstruction. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
98.
Sébastien Peirani Fabrice Durier José A. de Freitas Pacheco 《Monthly notices of the Royal Astronomical Society》2006,367(3):1011-1016
Cosmological N -body simulations were performed to study the evolution of the phase-space density Q =ρ/σ3 of dark matter haloes. No significant differences in the scale relations Q ∝σ−2.1 or Q ∝ M −0.82 are seen for the 'cold' or 'warm' dark matter models. The follow-up of individual haloes from z = 10 up to the present time indicate the existence of two main evolutionary phases: an early and fast one (10 > z > 6.5) , in which Q decreases on the average by a factor of 40 as a consequence of the randomization of bulk motions, and a late and long one (6.5 > z ≥ 0) , in which Q decreases by a factor of 20 because of mixing induced by merger events. The study of these haloes has also evidenced that rapid and positive variations of the velocity dispersion, induced by merger episodes, are related to a fast decrease of the phase-space density Q . 相似文献
99.
T. P. Idiart J. Silk José A. de Freitas Pacheco 《Monthly notices of the Royal Astronomical Society》2007,381(4):1711-1718
New calibrations of spectrophotometric indices of elliptical galaxies as functions of spectrophotometric indices are presented, permitting estimates of mean stellar population ages and metallicities. These calibrations are based on evolutionary models including a two-phase interstellar medium, infall and a galactic wind. Free parameters were fixed by requiring that models reproduce the mean trend of data in the colour–magnitude diagram as well as in the plane of indices Hβ–Mg2 and Mg2 –〈Fe〉 . To improve the location of faint ellipticals ( M B > −20) in the Hβ–Mg2 diagram, downsizing was introduced. An application of our calibrations to a sample of ellipticals and a comparison with results derived from single stellar population models are given. Our models indicate that mean population ages span an interval of 7–12 Gyr and are correlated with metallicities, which range from approximately half up to three times solar. 相似文献
100.