全文获取类型
收费全文 | 158篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 36篇 |
地球物理 | 32篇 |
地质学 | 46篇 |
海洋学 | 22篇 |
天文学 | 22篇 |
自然地理 | 10篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 15篇 |
2012年 | 6篇 |
2011年 | 5篇 |
2010年 | 7篇 |
2009年 | 2篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 10篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1892年 | 1篇 |
1887年 | 1篇 |
1885年 | 3篇 |
排序方式: 共有170条查询结果,搜索用时 15 毫秒
81.
Pooja?V.?Kshirsagar Hetu?C.?ShethEmail author Sheila?J.?Seaman Badrealam?Shaikh Poonam?Mohite Trupti?Gurav D.?Chandrasekharam 《Bulletin of Volcanology》2012,74(2):559-577
Spherulites and thundereggs are rounded, typically spherical, polycrystalline objects found in glassy silicic rocks. Spherulites
are dominantly made up of radiating microscopic fibers of alkali feldspar and a silica mineral (commonly quartz). They form
due to heterogeneous nucleation in highly supercooled rhyolitic melts or by devitrification of glass. Associated features
are lithophysae (“stone bubbles”), which have an exterior (sometimes concentric shells) of fine quartz and feldspar, and internal
cavities left by escaping gas; when filled by secondary silica, these are termed thundereggs. Here, we describe four distinct
occurrences of spherulites and thundereggs, in pitchstones (mostly rhyolitic, some trachytic) of the Deccan Traps, India.
The thundereggs at one locality were previously misidentified as rhyolitic lava bombs and products of pyroclastic extrusive
activity. We have characterized the thundereggs petrographically and geochemically and have determined low contents of magmatic
water (0.21–0.38 wt.%) in them using Fourier transform infrared spectroscopy. We consider that the spherulite-bearing outcrops
at one of the localities are of lava flows, but the other three represent subvolcanic intrusions. Based on the structural
disposition of the Deccan sheet intrusions studied here and considerations of regional geology, we suggest that they are cone
sheets emplaced from a plutonic center now submerged beneath the Arabian Sea. 相似文献
82.
E. Williams N. Nathou E. Hicks C. Pontikis B. Russell M. Miller M.J. Bartholomew 《Atmospheric Research》2009,91(2-4):292-298
Two Doppler radars and a suite of auxiliary surface observations are used to document the electrical, aerosol and aerodynamic properties of dust-lofting gust fronts near Niamey, Niger during the AMMA (African Monsoon Multidisciplinary Analysis). Electrification with dominant negative polarity is a common behavior, consistent with earlier studies on dust devils and the Harmattan wind in dry environments. 相似文献
83.
Data collected in 2007 from a dense commercial network (operated by AWS Convergence Technologies, Inc.) of roof-mounted temperature
sensors are used to explore the heat island characteristics of Washington, DC, and New York City, NY. Considerable spatial
detail is revealed, but aggregating data in annuli centered on assumed central locations in the business districts of the
two cities reveals that the heat islands extend out to more than 30 km, with the New York City island being somewhat larger.
The results from both arrays reveal the influence of the surroundings, with large scatter of daytime results being characteristic
of sites with the greatest local surface inhomogeneity. Nighttime data are more ordered, and suggest that surface air temperatures
decrease by about 0.02°C km−1 for the Washington case, and 0.04°C km−1 for New York, with the winter behaviour being more pronounced than for other seasons. Scatter of the data in the daytime
is a common feature for all seasons, but mainly for those with the strongest insolation. Comparison between working day and
weekend temperatures provides convincing verification that the air responds quite slowly to changes in surface (radiometric)
temperatures, with distance constants of the order of many tens of km. There appears to be a small wind speed effect, which
is evident in the nighttime data but is largely obscured by scatter for the daytime. 相似文献
84.
Brendan J. Hicks 《新西兰海洋与淡水研究杂志》2013,47(5):651-664
Abstract Stable isotopes of carbon (C) and nitrogen (N) were studied in 11 stream communities in the Waikato region of New Zealand. From comparisons of mean δ13C and δ15N values, food webs in the shaded, forest streams were clearly based on allochthonous material (conditioned leaf litter and terrestrial invertebrates). Autotrophs in forest streams were not a significant C source for the food webs. However, the C source of food webs in the unshaded pasture streams appeared to be a mixture of allochthonous and autochthonous material. Conditioned leaf litter appeared to contribute to the pasture stream food webs, and the δ13C and δ15N of some samples of epilithic diatoms indicated their consumption by invertebrates in pasture streams. Fish ate a wide range of aquatic invertebrates; longfinned eels (Anguilla dieffenbachii) and banded kokopu (Galaxias fasciatus) also had a large proportion of terrestrial invertebrates in their diet. Filamentous green algae were found only at pasture sites, where they were sometimes abundant. The wide range of δ13C values of filamentous green algae (‐18.8 to ‐29.7‰) complicated understanding of their role in the stream food webs. The δ13C values of Cladophora were related to water velocity, with more 13C‐enriched values in pools than in runs (‐23.2‰ in pools, mean velocity 0.12 m s?1; ‐28.1‰ in runs, mean velocity 0.24 m s?1). Crayfish and the gastropod mollusc Potamopyrgus appeared to be the only invertebrates to eat filamentous green algae. 相似文献
85.
G. R. F. Hicks 《新西兰海洋与淡水研究杂志》2013,47(1):86-119
Seven species of littoral harpacticoid copepods are recorded from the Wellington coast of central New Zealand. Amongst these are five new species, one in each of the genera Scutellidium, Eupelte, Amphiascus and two in Porcellidium. Amphiascopsis cinctus (Claus, 1866) and A. south‐georgiensis (Lang, 1936) are recorded and figured. 相似文献
86.
Six nights of BVR photometry and three nights of R photometry were collected over a month-long period shortly after the Cassini encounter with Hyperion on September 24 2005. Our observations were designed to help constrain the rotational state of the chaotically rotating satellite. Fourier analysis of our lightcurve data yields three possible periods: 10.2±0.2, 13.9±0.2, and 19.7±0.4 days. Our B-V and V-R colors agree well with previous ground-based and Voyager 2 measurements. 相似文献
87.
Facies analysis combined with sequence stratigraphic interpretation of the Upper Permian carbonate (Ca2) of NE Germany (i.e. northern basin margin of the Southern Permian Basin) confirm the existence of a rimmed platform with a steep and tectonically structured slope. The karstified A1 platform is overlain by deposits of a thin transgressive systems tract (TST) and a thick highstand systems tract (HST) which shows two larger-scale regressive shallowing-upwards cycles (4th order) with typical stacking patterns of small-scale cycles (5th order). The TST consists of bitumen-rich mudstones with reworked clasts of anhydrite and early cemented wacke- to grainstones, and it shows two, probably 5th-order, deepening-upwards cycles. The first larger-scale shallowing-up cycle on the Ca2 platform (4th-order) is dominated by aggradation of the bar and shoal deposits, whereas the second one is dominated by progradation. The tops of both cycles are characterised by erosional and exposure surfaces. Various types of small-scale shallowing-upwards cycles (5th-order) are observed in the bar, in the intertidal and in the algal-dominated supratidal environment, showing pronounced transgressive boundaries. On the slope and in the basin, equally thick TST and HST are observed. These incorporate carbonate turbidites which indicate "highstand shedding" from the platform. Various orders of relative sea-level variations are discussed. Controlling factors include tectonics, climate, and eustatic processes. A combined carbonate and evaporite sequence was found on the upper Ca2 slope, which may indicate a Ca2-lowstand systems wedge. 相似文献
88.
The impact of the Wangara experiment 总被引:1,自引:0,他引:1
89.
Neutron polarization analysis has been used for the quantitative determination of hydrogen in a crystal of synthetic quartz. The observed weighted average value of 1860±950 H/106Si is in good agreement with the value determined from infrared absorption. 相似文献
90.
Two types of hyphal-extraction, direct-count methods of estimating fungal biovalume in standing-dead, autumn leaves of Spartina alterniflora were compared with a clearing+staining method which does not require homogenization. Bacterial biovolume also was estimated, by an acridine-orange direct-count method. Type of homogenization had little effect on measured fungal volume, but counts made using water-soluble-aniline-blue epifluorescence were consistently lower than those made using phase-contrast (by 6–10x). Clearing+staining could not be used to estimate hyphal lengths, but was of use in estimating total ascocarp volume (=0.06 mm3 per mm3 of leaf). Estimated fungal hyphal volume was approximately 0.27 mm3 per mm3 of leaf. Bacterial volume was <3% of fungal volume. 相似文献