全文获取类型
收费全文 | 384篇 |
免费 | 30篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 14篇 |
地球物理 | 138篇 |
地质学 | 124篇 |
海洋学 | 41篇 |
天文学 | 61篇 |
综合类 | 8篇 |
自然地理 | 25篇 |
出版年
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 12篇 |
2018年 | 18篇 |
2017年 | 15篇 |
2016年 | 27篇 |
2015年 | 21篇 |
2014年 | 24篇 |
2013年 | 23篇 |
2012年 | 29篇 |
2011年 | 23篇 |
2010年 | 20篇 |
2009年 | 30篇 |
2008年 | 20篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 16篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1967年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有417条查询结果,搜索用时 453 毫秒
261.
262.
Exploring composition and behaviour of fish fauna by in situ observations in the Bari Canyon (Southern Adriatic Sea,Central Mediterranean)
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)
Gianfranco D'Onghia Francesca Capezzuto Angela Carluccio Roberto Carlucci Agnese Giove Francesco Mastrototaro Michele Panza Letizia Sion Angelo Tursi Porzia Maiorano 《Marine Ecology》2015,36(3):541-556
Canyons play a fundamental role in enhancing the abundance and diversity of marine organisms through the transport of organic matter and food resources, the presence of complex physical habitats and the absence of trawl fishing. During four baited lander deployments carried out in the Bari Canyon (Southern Adriatic Sea, Central Mediterranean), at depths of 443–788 m, about 43 h of video records were taken, for a total of 619,200 video frames. A total of 12 benthopelagic fish species (five chondrichthyes and seven osteichthyes) were identified. The blackspot seabream (Pagellus bogaraveo) was the most often observed fish species. The depth of 787 m represents a new depth record for this fish in the Adriatic Sea. Groups of up to 40 individuals of P. bogaraveo were attracted to the bait and were shown in single frames. The individuals were observed both exploring the area and feeding actively on the bait. The European conger (Conger conger) was recorded at each deployment. Clear scavenger behaviour was also observed in this teleost fish and in the shark Etmopterus spinax. The shark species Centrophorus granulosus and Hexanchus griseus, which are considered ‘vulnerable’ on the published IUCN Mediterranean Regional Red List, were also recorded but, although attracted by the bait, they were never seen feeding on it. Other fish species, harvested on fishing grounds, such as Merluccius merluccius, Helicolenus dactylopterus and Polyprion americanus, were also recorded. This study represents the first in situ documentation, at very low impact, of the fish fauna in the Bari Canyon, providing new insights into its small scale distribution and behaviour, the first in situ direct observation of the variable feeding behaviour of P. bogaraveo and its gregarious habits, as well as indicating that this canyon could act as a refuge area for species that are vulnerable to fishing on the open slope. 相似文献
263.
M. C. González-García Michele Maltoni Joan Rojo 《Astrophysics and Space Science》2007,309(1-4):447-451
The precise knowledge of the atmospheric neutrino fluxes is a key ingredient in the interpretation of the results from any
atmospheric neutrino experiment. In the standard atmospheric neutrino data analysis, these fluxes are theoretical inputs obtained
from sophisticated numerical calculations. In this work we present an alternative approach to the determination of the atmospheric
neutrino fluxes based on the direct extraction from the experimental data on neutrino event rates.
相似文献
264.
Michele Cappellari R. Bacon M. Bureau M. C. Damen Roger L. Davies P. T. de Zeeuw Eric Emsellem Jesús Falcón-Barroso Davor Krajnovi Harald Kuntschner Richard M. McDermid Reynier F. Peletier Marc Sarzi Remco C. E. van den Bosch Glenn van de Ven 《Monthly notices of the Royal Astronomical Society》2006,366(4):1126-1150
265.
Katia Ganda Jesús Falcón-Barroso Reynier F. Peletier Michele Cappellari Eric Emsellem Richard M. McDermid P. Tim de Zeeuw C. Marcella Carollo 《Monthly notices of the Royal Astronomical Society》2006,367(1):46-78
We present the stellar and gas kinematics of a sample of 18 nearby late-type spiral galaxies (Hubble types ranging from Sb to Sd), observed with the integral-field spectrograph SAURON at the 4.2-m William Herschel Telescope. SAURON covers the spectral range 4800–5380 Å, allowing us to measure the Hβ, Fe, Mg b absorption features and the emission in the Hβ line and the [O iii ]λλ4959, 5007 Å and [N i ]λλ5198, 5200 Å doublets over a 33 × 41-arcsec2 field of view. The maps cover the nuclear region of these late-type galaxies and in all cases include the entire bulge. In many cases the stellar kinematics suggests the presence of a cold inner region, as visible from a central drop in the stellar velocity dispersion. The ionized gas is almost ubiquitous and behaves in a complicated fashion: the gas velocity fields often display more features than the stellar ones, including wiggles in the zero-velocity lines, irregular distributions, ring-like structures. The line ratio [O iii ]/Hβ often takes on low values over most of the field, probably indicating a wide-spread star formation. 相似文献
266.
267.
268.
Jesús Falcn-Barroso Marc Sarzi Roland Bacon Martin Bureau Michele Cappellari Roger L. Davies Eric Emsellem Kambiz Fathi Davor Krajnovi Harald Kuntschner Richard M. McDermid Reynier F. Peletier Tim de Zeeuw 《New Astronomy Reviews》2006,49(10-12):515
We present results of our ongoing study of the morphology and kinematics of the ionised gas in 48 representative nearby elliptical and lenticular galaxies using the SAURON integral-field spectrograph on the 4.2m William Herschel Telescope. Making use of a recently developed technique, emission is detected in 75% of the galaxies. The ionised-gas distributions display varied morphologies, ranging from regular gas disks to filamentary structures. Additionally, the emission-line kinematic maps show, in general, regular motions with smooth variations in kinematic position angle. In most of the galaxies, the ionised-gas kinematics is decoupled from the stellar counterpart, but only some of them present signatures of recent accretion of gaseous material. The presence of dust is very common in our sample and is usually accompanied by gas emission. Our analysis of the [Oiii]/Hβ emission-line ratios, both across the whole sample as well as within the individual galaxies, suggests that there is no unique mechanism triggering the ionisation of the gas. 相似文献
269.
Kristin R. Wilson Joseph T. Kelley Arie Croitoru Michele Dionne Daniel F. Belknap Robert Steneck 《Estuaries and Coasts》2009,32(5):855-870
Salt pools are water-filled depressions common to north-temperate salt marshes. In Wells, ME, USA, cores reveal a unique salt
pool signature consisting of water-saturated dark-gray mud often containing fragments of Ruppia maritima. Cores through pool sediment reenter salt marsh peat, not tidal flat sediment, demonstrating that most pools are of secondary
origin. A principal component analysis of attribute data collected from 119 pools defines three distinct pool types: those
with (1) surrounding high-marsh vegetation and thick heavily undercut banks (40% of the variance), (2) surrounding low-marsh
vegetation and thicker slightly undercut banks (18% of the variance), and (3) surrounding low-marsh vegetation and less thick
moderately undercut banks, containing R. maritima and a surficial drainage (15% of the variance). Cores and spatiotemporal analyses of aerial photographs between 1962 and
2003 reveal dramatic salt marsh surface dynamism suggesting that salt pools influence the geomorphological evolution of coastal
marshes. 相似文献
270.
Antonio Caracausi P. Mario Nuccio Rocco Favara Marco Nicolosi Michele Paternoster 《地学学报》2009,21(2):83-87
Geochemical investigations have shown that there is a considerable inflow of gas into both crater lakes of Monticchio, Southern Italy. These lakes are located in two maars that formed 140 000 years ago during Mt. Vulture volcano's last eruptive activity. Isotopic analyses suggest that CO2 and helium are of magmatic origin; the latter displays 3 He/4 He isotope ratios similar to those measured in olivines of the maar ejecta. In spite of the fact that the amount of dissolved gases in the water is less than that found in Lake Nyos (Cameroon), both the results obtained and the historical reports studied indicate that these crater lakes could be highly hazardous sites, even though they are located in a region currently considered inactive. This could be of special significance in very popular tourist areas such as the Monticchio lakes, which are visited by about 30 000 people throughout the summer, for the most part on Sundays. 相似文献