全文获取类型
收费全文 | 173篇 |
免费 | 5篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 9篇 |
地球物理 | 36篇 |
地质学 | 87篇 |
海洋学 | 23篇 |
天文学 | 9篇 |
自然地理 | 13篇 |
出版年
2024年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 6篇 |
2012年 | 3篇 |
2011年 | 8篇 |
2010年 | 2篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有178条查询结果,搜索用时 10 毫秒
171.
172.
The detection and measurement of CO2 in air bubbles entrapped in ice originated with Per F. Scholander in 1954, predating the studies referred to in Broecker (1982), Geochim. Cosmochim. Acta 46, 1689–1706. 相似文献
173.
Narrow reversed rims on plagioclase are ubiquitous in troctolites and olivine gabbros of the Kiglapait intrusion and may be a common feature of all such cumulates. The rims occur at plag/plag, plag/ol, and less strongly at plag/aug grain boundaries. They are optically obvious atΔAn < 10 mol.% and can reachΔAn = 32 mol.% or more. In parallel,K/Na drops sharply. Although ubiquitous from sample to sample, the reversed rims are only locally present at grain boundaries even for the same pair of crystals in contact; they are prominent in linear networks suggesting the last trace of intercumulus liquid. A subsolidus origin is ruled out by the absence of reactants at plag/plag and plag/ol boundaries and by the local rather than pervasive development of rims. The rims are required to grow from intercumulus liquid, in which the partition of An component between crystals and liquid increases with the trapped augite component of the liquid. Calculations from published experimental data show thatΔAn > 30 can easily be achieved by such a process. It is also probable that the trapped liquid is part of an An-rich boundary layer generated by solute rejection during adcumulus growth. The ability of the rims to sustain steepK/Na gradients despite a long subsolidus cooling history proves that the KNa exchange rate is vanishingly small over a geologic time scale in An-rich feldspar, suggesting that at low K content the potassium is site-bound to the tetrahedralAl/Si distribution. Reversed rims therefore provide important information on diffusion limits as well as on the late-stage solidification history of plagioclase-rich cumulates. Moreover, they demonstrate that plagioclase geothermometry cannot be divorced from effects of liquid composition and structure as monitored, for example, by augite content. 相似文献
174.
Equipped to deal with uncertainty in climate and impacts predictions: lessons from internal peer review 总被引:1,自引:0,他引:1
175.
Katherine C. Filippino Margaret R. Mulholland Peter W. Bernhardt George E. Boneillo Ryan E. Morse Matthew Semcheski Harold Marshall Nancy G. Love Quinn Roberts Deborah A. Bronk 《Estuaries and Coasts》2011,34(2):269-280
Total maximum daily loads for nitrogen (N) are currently being established for the Chesapeake Bay watershed. While we know
inorganic N is bioavailable in the environment and therefore its input contributes to cultural eutrophication, the bioavailability
of organic N is unclear. Using bioassay experiments, we examined the impact of effluent-derived organic nitrogen (EON) from
wastewater treatment plants on natural water samples collected along an estuarine/salinity gradient within the lower Chesapeake
Bay watershed. All of the inorganic N and between 31% and 96% of the EON was removed during biotic bioassays within the first
2 days. Further, there was substantial abiotic reactivity of effluent N when it was added to natural water samples. Results
demonstrate that organic and inorganic N in effluent is removed to support the growth of microbial communities. These are
the first results aimed at assessing the reactivity of EON in natural waters along an estuarine/salinity gradient. 相似文献
176.
Margaret R. Mulholland Ryan Morse Todd Egerton Peter W. Bernhardt K. C. Filippino 《Estuaries and Coasts》2018,41(6):1744-1765
A multi-year study was conducted in the eutrophic Lafayette River, a sub-tributary of the lower Chesapeake Bay during which uptake of inorganic and organic nitrogen (N) and C compounds was measured during multiple seasons and years when different dinoflagellate species were dominant. Seasonal dinoflagellate blooms included a variety of mixotrophic dinoflagellates including Heterocapsa triquetra in the late winter, Prorocentrum minimum in the spring, Akashiwo sanguinea in the early summer, and Scrippsiella trochoidea and Cochlodinium polykrikoides in late summer and fall. Results showed that no single N source fueled algal growth, rather rates of N and C uptake varied on seasonal and diurnal timescales, and within blooms as they initiated and developed. Rates of photosynthetic C uptake were low yielding low assimilation numbers during much of the study period and the ability to assimilate dissolved organic carbon augmented photosynthetic C uptake during bloom and non-bloom periods. The ability to use dissolved organic C during the day and night may allow mixotrophic bloom organisms a competitive advantage over co-occurring phytoplankton that are restricted to photoautotrophic growth, obtaining N and C during the day and in well-lit surface waters. 相似文献
177.
Nels R. Bjarke Ben Livneh Sarah C. Elmendorf Noah P. Molotch Eve-Lyn S. Hinckley Nancy C. Emery Pieter T. J. Johnson Jennifer F. Morse Katherine N. Suding 《水文研究》2021,35(9):e14320
The Niwot Ridge and Green Lakes Valley (NWT) long-term ecological research (LTER) site collects environmental observations spanning both alpine and subalpine regimes. The first observations began in 1952 and have since expanded to nearly 300 available datasets over an area of 99 km2 within the north-central Colorado Rocky Mountains that include hydrological (n = 101), biological (n = 79), biogeochemical (n = 62), and geographical (n = 56) observations. The NWT LTER database is well suited to support hydrologic investigations that require long-term and interdisciplinary data sets. Experimentation and data collection at the NWT LTER are designed to characterize ecological responses of high-mountain environments to changes in climate, nutrients, and water availability. In addition to the continuation of the many legacy NWT datasets, expansion of the breadth and utility of the NWT LTER database is driven by new initiatives including (a) a catchment-scale sensor network of soil moisture, temperature, humidity, and snow-depth observations to understand hydrologic connectivity and (b) snow-albedo alteration experiments using black sand to evaluate the effects of snow-disappearance on ecosystems. Together, these observational and experimental datasets provide a substantial foundation for hydrologic studies seeking to understand and predict changes to catchment and local-scale process interactions. 相似文献
178.
Cheryl Ann Blain Mustafa Kemal Cambazoglu Robert S. Linzell Kendra M. Dresback Randall L. Kolar 《Ocean Dynamics》2012,62(3):411-437
A limited domain, coastal ocean forecast system consisting of an unstructured grid model, a meteorological model, a regional
ocean model, and a global tidal database is designed to be globally relocatable. For such a system to be viable, the predictability
of coastal currents must be well understood with error sources clearly identified. To this end, the coastal forecast system
is applied at the mouth of Chesapeake Bay in response to a Navy exercise. Two-day forecasts are produced for a 10-day period
from 4 to 14 June 2010 and compared to real-time observations. Interplay between the temporal frequency of the regional model
boundary forcing and the application of external tides to the coastal model impacts the tidal characteristics of the coastal
current, even contributing a small phase error. Frequencies of at least 3 h are needed to resolve the tidal signal within
the regional model; otherwise, externally applied tides from a database are needed to capture the tidal variability. Spatial
resolution of the regional model (3 vs 1 km) does not impact skill of the current prediction. Tidal response of the system
indicates excellent representation of the dominant M
2 tide for water level and currents. Diurnal tides, especially K
1, are amplified unrealistically with the application of coarse 27-km winds. Higher-resolution winds reduce current forecast
error with the exception of wind originating from the SSW, SSE, and E. These winds run shore parallel and are subject to strong
interaction with the shoreline that is poorly represented even by the 3-km wind fields. The vertical distribution of currents
is also well predicted by the coastal model. Spatial and temporal resolution of the wind forcing including areas close to
the shoreline is the most critical component for accurate current forecasts. Additionally, it is demonstrated that wind resolution
plays a large role in establishing realistic thermal and density structures in upwelling prone regions. 相似文献