全文获取类型
收费全文 | 675篇 |
免费 | 37篇 |
国内免费 | 20篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 53篇 |
地球物理 | 179篇 |
地质学 | 252篇 |
海洋学 | 56篇 |
天文学 | 92篇 |
自然地理 | 91篇 |
出版年
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 22篇 |
2019年 | 18篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 22篇 |
2015年 | 26篇 |
2014年 | 21篇 |
2013年 | 49篇 |
2012年 | 27篇 |
2011年 | 42篇 |
2010年 | 27篇 |
2009年 | 32篇 |
2008年 | 28篇 |
2007年 | 33篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 22篇 |
2003年 | 19篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 16篇 |
1999年 | 14篇 |
1998年 | 16篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 4篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 8篇 |
1966年 | 3篇 |
1964年 | 2篇 |
1922年 | 3篇 |
1921年 | 4篇 |
1920年 | 2篇 |
排序方式: 共有732条查询结果,搜索用时 578 毫秒
701.
<正>In the last decade there has been a considerable effort to better understand the joint evolution of mafic and ultramafic magmatic systems and their deep mantle roots,through integrated petrological and thermo-barometric studies.Magma generation is regarded as the result of complex processes including melting,creation of channels for melt transfer,and interaction with the wall-rocks.Complexities in magmatic systems involve metasomatism and the creation of metasomatic fronts,branching and splitting of magma volumes during their evolution,and vat- 相似文献
702.
Steven N. Ward 《Geophysical Journal International》1984,78(1):241-253
Summary. This paper derives exact solutions to the equations of static plane strain by means of propagator matrices for homogeneous, gravitating and non- gravitating elastic media. These solutions are immediately verifiable and are flexible under a variety of boundary conditions. Propagator matrices are eminently suitable for computer encoding and, through their multiplication, are applicable to depth-dependent structures. Attention is focused upon the bending of floating plates which are loaded to simulate the deflection of oceanic lithosphere in the vicinity of trenches. By comparing responses computed with and without body forces, I find that gravity does not meaningfully change deflection profiles; however, it can influence important aspects of the internal stress state. Gravitational stresses are proportional to the gradient of the vertical deformation and amount to about 10 per cent of the bending stresses in these models. Propagators which include gravity are used to investigate the effect of regional horizontal stresses upon bending plates. I conclude that applied compressive forces can transport the neutral surface through 10–20 km of depth without significantly deforming the plate profile or increasing the maximum internal stress by more than 30 percent. These calculations support the contention that variable compressive stresses resulting from interplate coupling could account for observed regional differences in neutral surface height. For elastic-plastic material, the fundamental equations of motion become non-linear; however, there appears to be no a priori objection to their linearization. I speculate that the propagator formalism, when applied in an iterative approach, could be a powerful method for computing the deformation of such media. 相似文献
703.
Jennifer L. Lewicki Deborah Bergfeld Carlo Cardellini Giovanni Chiodini Domenico Granieri Nick Varley Cynthia Werner 《Bulletin of Volcanology》2005,68(1):76-90
We present a comparative study of soil CO2 flux () measured by five groups (Groups 1–5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1–5 measured using the accumulation chamber method at 5-m spacing within a 900 m2 grid during a morning (AM) period. These measurements were repeated by Groups 1–3 during an afternoon (PM) period. Measured ranged from 218 to 14,719 g m−2 day−1. The variability of the five measurements made at each grid point ranged from ±5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO2 emission rate estimates varied between groups by only ±22%. All three groups that made PM measurements reported an 8–19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO2 emission rate of one data set and to map the spatial distribution, we compared six geostatistical methods: arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods. While the total CO2 emission rates estimated using the different techniques only varied by ±4.4%, the maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of , but a variety of geostatistical methods are appropriate to estimate the total CO2 emission rate from a study area, which is a primary goal in volcano monitoring research.Editorial responsibility: H Shinohara 相似文献
704.
Various physical and biological properties affect solute transport patterns in streams. We measured hydraulic characteristics of Payne Creek, a low‐gradient upper Coastal Plain stream, using tracer experiments and parameter estimation with OTIS‐P (one‐dimensional transport with inflow and storage with parameter optimization). The primary objective of this study was to estimate the effects of varying discharge, season, and litter accumulation on hydraulic parameters. Channel area A ranged from 0·081 to 0·371 m2 and transient storage area As ranged from 0·027 to 0·111 m2. Dispersion D ranged from 1·5 to 11·1 m2 min−1 and exchange coefficient α ranged from 0·009 to 0·038 min−1. Channel area and dispersion were positively correlated to discharge Q, whereas storage area and exchange coefficient were not. Relative storage size As/A ranged from 0·17 to 0·59, and was higher during fall than other seasons under a similar Q. The fraction of median travel time due to transient storage ranged from 8·8 to 34·5% and was significantly correlated with Q through a negative power function. Both metrics indicated that transient storage was a significant component affecting solute transport in Payne Creek, especially during the fall. Comparison between the measured channel area Ac and A suggested that surface storage was dominant in Payne Creek. During fall, accumulation of leaf litter resulted in larger A and As and lower velocity and D than during other seasons with similar discharge. Seasonal changes in discharge and organic matter accumulation, and dynamic channel morphology affected the magnitude of transient storage and overall hydraulic characteristics of Payne Creek. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
705.
706.
707.
Nick Hewitt 《Journal of Atmospheric Chemistry》2005,50(3):321-322
708.
Nick Teanby 《Astronomy& Geophysics》2005,46(5):5.20-5.25
Cassini's first year examining Saturn and its moons has uncovered many surprises, not least on the enigmatic moon Titan. Nick Teanby reviews the progress made and discusses prospects for the future. 相似文献
709.
In this article, we assess the human and economic hazard posed by tsunami waves generated from impacts of sub-2 km diameter
asteroids. Annually, on average, 182(+197/−123) people will be affected by impact-induced waves with a corresponding infrastructure
loss of $18(+20/−12)M/y. Half of the tsunami hazard stems from impactors with diameters less than 300 m. One near Earth asteroid
will survive atmospheric transit and strike somewhere into Earth’s oceans every 5880 years, on average. In the mean generic
scenario, the tsunami from the impact affects 1.1 million people and destroys $110B of infrastructure. 相似文献
710.