全文获取类型
收费全文 | 278篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 33篇 |
地球物理 | 86篇 |
地质学 | 76篇 |
海洋学 | 36篇 |
天文学 | 27篇 |
综合类 | 2篇 |
自然地理 | 19篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 13篇 |
2013年 | 12篇 |
2012年 | 14篇 |
2011年 | 18篇 |
2010年 | 17篇 |
2009年 | 23篇 |
2008年 | 17篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 4篇 |
排序方式: 共有286条查询结果,搜索用时 9 毫秒
81.
82.
In recent years the use of Acoustic Doppler Current Profilers (ADCPs) to estimate Reynolds stresses, using the so-called variance
method, has become popular; and although there was great effort in studying the uncertainties on this technique, there were
no reports in the main literature of its validity using independent measurements. This work reports on the comparison of ADCP
and Acoustic Current Velocimeter (ADV) estimates of Reynolds stresses. The comparison of the ADCP and ADV is encouraging during
periods when no strong waves were present with both the explained variance of 0.8 and the slope of the regression being 0.97.
Nevertheless, when strong waves are present the method breaks down and the comparison between ADCP and ADV is very poor with
R2 =0.04. 相似文献
83.
Di Virgilio Giovanni Evans Jason P. Di Luca Alejandro Grose Michael R. Round Vanessa Thatcher Marcus 《Climate Dynamics》2020,54(11):4675-4692
Climate Dynamics - Coarse resolution global climate models (GCMs) cannot resolve fine-scale drivers of regional climate, which is the scale where climate adaptation decisions are made. Regional... 相似文献
84.
W. R. Hartmann M. Santana M. Hermoso M. O. Andreae E. Sanhueza 《Journal of Atmospheric Chemistry》1991,13(1):63-72
Formic and acetic acids were measured in a scrub-grass savanna and in a nearby semideciduous forest. Gaseous HCOOH and CH3COOH were collected using the mist-scrubber technique, and were determined using ion chromatography. A strong diurnal cycle was observed at both sites, with higher mixing ratios during daytime. Concentrations in the savanna were always higher than in the forest. Most of the time HCOOH/CH3COOH ratios greater than one were recorded at the savanna site, and ratios less than one at the forest site. Boundary-layer mixing ratios in the savanna region, derived from measurements during midday, are 1.3±0.4 ppbv and 0.7±0.3 ppbv for HCOOH and CH3COOH. Dry depositions velocities between 0.5 and 1 cm s-1 were estimated for the savanna region. Atmospheric residence times of <3 days and >5 days were estimated for the rainy and dry season, respectively. 相似文献
85.
Antonio Algaba Fernando Fernández-Sánchez Manuel Merino Alejandro J. Rodríguez-Luis 《Theoretical and Applied Climatology》2016,126(3-4):797-799
The paper, “Study on the reliable computation time of the numerical model using the sliding temporal correlation method,” was published in Theoretical and Applied Climatology. In that work, the sliding temporal correlation analysis is employed to investigate the predictable time of two typical chaotic numerical models, namely the Lorenz system and the Chen chaotic system. However, it has been recently shown by us when using a linear scaling in time and state variables that generically, the Chen system is only a particular case of the Lorenz system, with time reversion if the parameter c is positive. Consequently, to study the Chen chaotic system is simply to consider the Lorenz system integrated backwards. 相似文献
86.
Alejandro Caparrós 《Climatic change》2009,96(3):421-441
We set out a dynamic model to investigate optimal time paths of emissions, carbon stocks and carbon sequestration by land
conversion, allowing for non-instantaneous carbon sequestration. Previous research in a dynamic general equilibrium framework,
assuming instantaneous carbon sequestration, has shown that land conversion should take place as soon as possible. On the
contrary, previous research within a partial equilibrium framework has shown that, with increasing carbon prices, it is optimal
to delay carbon sequestration through land conversion. We show that land use change alternatives, e.g. reforestation, have
to be used as soon as possible before the singular path is reached, i.e. the unique trajectory that brings the system to the
steady-state. We also show that faster increasing carbon prices can induce a reduction in the rate of reforestation, and that
this may take place after an initial phase of increased reforestations or even immediately, depending upon the shape of the
increase in carbon prices. Finally, we show that the type of species used is relevant and that the land conversion rate gets
smaller the longer it takes the trees to grow. We analyze four different carbon accounting methods, describing the conditions
that make them efficient and discussing the comparative advantages of each of them. 相似文献
87.
Alejandro?D.?Canepuccia Maria?S.?Fanjul Eugenia?Fanjul Florencia?Botto Oscar?O.?Iribarne Consejo Nacional de Investigaciones Científicas y Técnicas Departamento de Biología Universidad Nacional de Mar del Plata Mar del Plata Argentina 《Estuaries and Coasts》2008,31(5):920-930
The role of positive and indirect interactions is often crucial in communities with intense abiotic stress such as salt marshes.
The burrowing crab, Neohelice (=Chasmagnathus) granulata, is the dominant benthic macroinvertebrate of southwest Atlantic marshes (southern Brazil to Northern Argentinean Patagonia),
having strong direct and indirect effects on marsh soil and, in consequence, on marsh vegetation and primary consumers. In
this work, we investigate if this crab indirectly modifies habitat use by the granivorous rodents, Akodon azarae and Oligoryzomys flavescens, by increasing nutrient availability and thus enhancing seed production by the marsh plant Spartina densiflora. The study was conducted at the Mar Chiquita Coastal Lagoon, Argentina (37°32′ S). Rodent frequencies in S. densiflora were positively correlated with crab densities throughout the low and middle marsh. Additionally, the highest quality of
S. densiflora and inflorescence density was recorded at the highest crab densities. Experimental manipulation of crab densities shows that
N. granulata indirectly enhances the performance of S. densiflora (e.g., decreased fiber content and C/N ratios) and increases density of seeds. Moreover, N. granulata also facilitates S. densiflora seed availability to rodents by concentrating them in sediment mound at their burrows entrances. Experimental rodent exclusions
showed that rodent species used S. densiflora seeds, a variable positively related to crab burrow density. Thus, our results show that N. granulata drives the granivorous rodent distribution and the intensity of seeds–rodent interaction trough facilitative and indirect
interactions in marsh community. 相似文献
88.
We studied a large debris-avalanche deposit of Pleistocene age in the Tenteniguada Basin, Gran Canaria Island, Spain. This
deposit, which is well preserved because it is mostly covered by basanite lava flows, has distinctive matrix and block facies,
hummocky topography and internal structures typical of debris avalanches. However, neither syneruptive lavas nor some characteristic
features of volcanic debris-avalanche deposits, such as a stratovolcano edifice or a horseshoe-shaped crater, are present.
The occurrence of internal features characteristic of volcanic avalanche deposits could be attributed to the volcanic materials
involved in the movement rather than to the triggering of the avalanche during a volcanic eruption. The conditioning factors
are shown to be associated with specific structural and hydrological conditions, such as the presence of old volcanic domes,
strength reduction of the rocks, effective stress decrease, active gully erosion and water table rise during Pleistocene humid
episodes. We finally suggest that the possible triggering factor of the avalanche was a neighbouring volcanic or tectonic
earthquake. 相似文献
89.
Laura McFarlane Tranquilla April Hedd Chantelle Burke William A. Montevecchi Paul M. Regular Gregory J. Robertson Leslie Ann Stapleton Sabina I. Wilhelm David A. Fifield Alejandro D. Buren 《Estuarine, Coastal and Shelf Science》2010
Ocean climate change is having profound biological effects in polar regions. Such change can also have far-reaching downstream effects in sub-polar regions. This study documents an environmental relationship between High Arctic sea ice changes and mortality events of marine birds in Low Arctic coastal regions. During April 2007 and March 2009, hundreds of beached seabird carcasses and moribund seabirds were found along the east and northeast coasts of Newfoundland, Canada. These seabird “wrecks” (i.e. dead birds on beaches) coincided with a period of strong, persistent onshore winds and heavily-accumulated sea ice that blocked bays and trapped seabirds near beaches. Ninety-two percent of wreck seabirds were Thick-billed Murres (Uria lomvia). Body condition and demographic patterns of wreck murres were compared to Thick-billed Murres shot in the Newfoundland murre hunt. Average body and pectoral masses of wreck carcasses were 34% and 40% lighter (respectively) than shot murres, indicating that wreck birds had starved. The acute nature of each wreck suggested that starvation and associated hypothermia occurred within 2–3 days. In 2007, first-winter murres (77%) dominated the wreck. In 2009, there were more adults (78%), mostly females (66%). These results suggest that spatial and temporal segregation in ages and sexes can play a role in differential survival when stochastic weather conditions affect discrete areas where these groups aggregate. In wreck years, southward movement of Arctic sea ice to Low Arctic latitudes was later and blocked bays longer than in most other years. These inshore conditions corresponded with recent climate-driven changes in High Arctic ice break-up and ice extent; coupled with local weather conditions, these ice conditions appeared to be the key environmental features that precipitated the ice-associated seabird wrecks in the Low Arctic region. 相似文献
90.
Eugenia Fanjul María A. Grela Alejandro Canepuccia Oscar Iribarne 《Estuarine, Coastal and Shelf Science》2008
Along the coastal areas of the Southwest Atlantic estuaries and embayments, phreatic water often circulates through very extended areas (up to several hundred meters perpendicular to the coast), dominated by dense assemblages of deep burrows of the crab Neohelice granulata (formerly Chasmagnathus granulatus). This crab inhabits the intertidal area, from mudflats to marshes vegetated by species of Spartina, Sarcocornia and Juncus, generating extensive burrowing beds where burrow density may reach up to 60 burrows m−2. Since the lower limit of the crab burrows is usually the water table, we investigated through field experiments the effect of N. granulata and their burrows on the chemical characteristics of this phreatic water. Water analysis from experimental (1) occupied burrows (with crabs), (2) unoccupied burrows (where crabs were excluded), and (3) sediment pore water show remarkable differences. Water oxygenation, and nitrate, ammonium and sulphate concentrations inside occupied burrows were higher than in the water inside unoccupied burrows or pore waters. Moreover, directed sampling of phreatic water entering and leaving the crab bed, shows that dissolved inorganic nitrogen concentration is enhanced as the water crosses the crab bed. These results may be ascribed to the fact that in the salt marsh the crabs spend most of their time within burrows, where presumably they store food (plants) and defecate. These activities generate an area of accumulation of excrements and nutrients in different decomposition states. The present work shows a novel way by which bioturbating organisms can affect nutrients exportation from salt marshes to the open waters. 相似文献