全文获取类型
收费全文 | 106篇 |
免费 | 3篇 |
专业分类
测绘学 | 22篇 |
大气科学 | 6篇 |
地球物理 | 24篇 |
地质学 | 31篇 |
海洋学 | 11篇 |
天文学 | 7篇 |
自然地理 | 8篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 1篇 |
2011年 | 5篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 8篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1988年 | 2篇 |
1985年 | 3篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1959年 | 1篇 |
1953年 | 1篇 |
1949年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有109条查询结果,搜索用时 15 毫秒
31.
32.
The European Gravity Field and Steady-State Ocean Circulation Explorer Satellite Mission Its Impact on Geophysics 总被引:1,自引:0,他引:1
J. A. Johannessen G. Balmino C. Le Provost R. Rummel R. Sabadini H. Sünkel C.C. Tscherning P. Visser P. Woodworth C. Hughes P. Legrand N. Sneeuw F. Perosanz M. Aguirre-Martinez H. Rebhan M. Drinkwater 《Surveys in Geophysics》2003,24(4):339-386
Current knowledge of the Earth's gravity field and its geoid, as derived from various observing techniques and sources, is incomplete. Within a reasonable time, substantial improvement will come by exploiting new approaches based on spaceborne gravity observation. Among these, the European Space Agency (ESA) Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission concept has been conceived and designed taking into account multi-disciplinary research objectives in solid Earth physics, oceanography and geodesy. Based on the unique capability of a gravity gradiometer combined with satellite-to-satellite high-low tracking techniques, an accurate and detailed global model of the Earth's gravity field and its corresponding geoid will be recovered. The importance of this is demonstrated by a series of realistic simulation experiments. In particular, the quantitative impact of the new and accurate gravity field and geoid is examined in studies of tectonic composition and motion, Glaciological Isostatic Adjustment, ocean mesoscale variability, water mass transport, and unification of height systems. Improved knowledge in each of these fields will also ensure the accumulation of new understanding of past and present sea-level changes. 相似文献
33.
The purpose of this paper is to demonstrate the effect of geophysical background model errors that affects temporal gravity
solutions provided by the Gravity Recovery And Climate Experiment (GRACE). Initial performance estimates by Dickey et al.
(1997) suggested a formal geoid RMS error better than 0.1 mm up to spherical harmonic degree 5. Now that the GRACE gravity
models and data are available, it is evident that these original expectations were too optimistic. Our hypothesis is that
this is partially explained by errors in geophysical background models that need to be applied in the GRACE data reduction,
and that this effect was not considered by Dickey et al. (1997). We discuss the results of a closed-loop simulation, where
satellite trajectory prediction software is used for the generation of GRACE range-rate data and GRACE orbit solutions with
the help of the Global Positioning System (GPS). During the recovery step in our closed-loop simulation, we show that simulated
nuisance signals (based on tide and air pressure model differences) map to a 0.7 mm geoid effect for periods longer than 3 months
and to less than 0.4 mm for periods shorter than 3 months. The long-period geoid hydrology signal is at a level of 4.5 mm,
while the short-period hydrology is at 0.25 mm. The long-period ocean bottom pressure (OBP) signal maps at 0.8 mm and for
short periods it is 0.4 mm. We conclude that short-period effects are difficult to observe by GRACE and that long-period effects,
like hydrology, are easier to recover than OBP variations. 相似文献
34.
35.
GPS-derived orbits for the GOCE satellite 总被引:5,自引:4,他引:1
Heike Bock Adrian Jäggi Ulrich Meyer Pieter Visser Jose van den IJssel Tom van Helleputte Markus Heinze Urs Hugentobler 《Journal of Geodesy》2011,85(11):807-818
The first ESA (European Space Agency) Earth explorer core mission GOCE (Gravity field and steady-state Ocean Circulation Explorer)
was launched on 17 March 2009 into a sun-synchronous dusk–dawn orbit with an exceptionally low initial altitude of about 280 km.
The onboard 12-channel dual-frequency GPS (Global Positioning System) receiver delivers 1 Hz data, which provides the basis
for precise orbit determination (POD) for such a very low orbiting satellite. As part of the European GOCE Gravity Consortium
the Astronomical Institute of the University of Bern and the Department of Earth Observation and Space Systems are responsible
for the orbit determination of the GOCE satellite within the GOCE High-level Processing Facility. Both quick-look (rapid)
and very precise orbit solutions are produced with typical latencies of 1 day and 2 weeks, respectively. This article summarizes
the special characteristics of the GOCE GPS data, presents POD results for about 2 months of data, and shows that both latency
and accuracy requirements are met. Satellite Laser Ranging validation shows that an accuracy of 4 and 7 cm is achieved for
the reduced-dynamic and kinematic Rapid Science Orbit solutions, respectively. The validation of the reduced-dynamic and kinematic
Precise Science Orbit solutions is at a level of about 2 cm. 相似文献
36.
The volcanic-sedimentary succession of the Ventersdorp Supergroup which is virtually undisturbed tectonically and of low-grade (greenschist facies) metamorphism, affords a unique opportunity for studying the interplay between volcanic and sedimentary processes. The transitional sequence between the Rietgat and Bothaville Formations consists of a number of lithofacies. These are a basal breccia representing pyroclastic and laharic deposits, an overlying breccia—arenite—conglomerate (BAC) which formed by debris flow and fluvial processes, an arenite deposited offshore during a transgression, and an upper conglomerate laid down on a beach. In the volcaniclastic BAC and arenite lithofacies the presence of thin tuff beds, deformed acid lava fragments (bombs?) and glass shards in the arenaceous matrix suggest syndepositional volcanism.Sedimentation took place along the flanks of an asymmetrical, actively volcanic, domal structure which consisted partly of unstable pyroclastic deposits in the east. Resedimentation of the pyroclastic debris by subaerial debris flows and braided streams built a volcaniclastic fan lobe at the foot of the domal structure. As volcanic activity subsided, sands derived from a granitic terrain, mixed with minor air-fall debris to subsequently cover the fan lobe during a regional transgression. 相似文献
37.
A travel time distribution based on a particle-tracking analysis in a ground water model containing weak sinks is often uncertain because whether a particle is discharged or allowed to pass through a weak sink is unresolved by particle-tracking theory. We present a probability-based method to derive an objective travel time distribution in models containing weak sinks. The method discharges a fraction of the particle at the weak sink and allows the remaining fraction to pass through the weak sink. The weight of the discharged fraction depends on the ratio of the sink flux to the influx into the weak sink cell. We tested this approach on a coarse (100 × 100 m) and a fine (25 × 25 m) horizontal resolution regional scale ground water model (34.5 × 24 km). We compared the travel time distributions in a small subcatchment derived from particle-tracking analysis with one derived from a transport model. We found that the particle-tracking analysis with the coarse model underestimated the travel time distribution of the catchment compared to the transport solution or a particle-tracking analysis with the fine model. The underestimation of travel times with the coarse model was a result of a large area covered by sink cells in this model and the more accurate flow patterns simulated by the fine model. The probability-based method presented here compares favorably with a solute transport solution and provides an accurate travel time distribution when used with a fine-resolution ground water model. 相似文献
38.
39.
Melissa Thaw Ate Visser Richard Bibby Amanda Deinhart Erik Oerter Martha Conklin 《水文研究》2021,35(6):e14249
Sierra Nevada forests transpire a significant amount of California's water resources, sparking interest in applying forest management to improve California's water supply. Determining the source water of evapotranspiration enables forest managers to make informed decisions. To this end, a significant interest in critical zone science is to develop new methods to work across time scales to predict subsurface water storage and use. In this study, forest vegetation accessed young water and switched sources depending on availability, suggesting that forest drought vulnerability may depend on the range of water sources available (rain, snowmelt and deeply stored water). This finding also suggests that changes in transpiration rates may have immediate effects on water sources in close proximity to vegetation, and delayed effects on storage and runoff. New δ18O, δ2H and 3H data were used to track precipitation, runoff, evapotranspiration and storage through the critical zone seasonally, including seasons where evapotranspiration and snowmelt were in phase (winter snowmelt) and out of phase (seasonally dry summer). The main source of this headwater catchment's runoff is derived from its meadow saturated zone water, which was dominated by snowmelt. Water that originated as snowmelt contributed to transpiration, unless other sources, such as recent rain, became available. In cases where xylem δ18O and δ2H signatures matched those of deeper saturated zone water, 3H data showed that xylem water was distinctly younger than the deep saturated zone water. During 2016, which experienced relatively normal snowpack in winter and seasonally dry summer conditions, mean summer saturated zone water and vegetation water were similar in δ18O, −12.4 ± 0.04 ‰ and − 12.5 ± 0.3 ‰, respectively, but were distinctly different in 3H, 5.5 ± 0.2 pCi/L and 13.7 ± 1.1 pCi/L, respectively. While δ18O shows that vegetation and meadow saturated zone water have similar origins, 3H shows they have dissimilar ages. 相似文献
40.
Lumped surface and sub‐surface runoff for erosion modeling within a small hilly watershed in northern Vietnam 下载免费PDF全文
Yen Tan Bui D. Orange S. M. Visser Chu Thai Hoanh M. Laissus A. Poortinga Duc Toan Tran L. Stroosnijder 《水文研究》2014,28(6):2961-2974
Developing models to predict on‐site soil erosion and off‐site sediment transport at the agricultural watershed scale represent an on‐going challenge in research today. This study attempts to simulate the daily discharge and sediment loss using a distributed model that combines surface and sub‐surface runoffs in a small hilly watershed (< 1 km2). The semi‐quantitative model, Predict and Localize Erosion and Runoff (PLER), integrates the Manning–Strickler equation to simulate runoff and the Griffith University Erosion System Template equation to simulate soil detachment, sediment storage and soil loss based on a map resolution of 30 m × 30 m and over a daily time interval. By using a basic input data set and only two calibration coefficients based, respectively, on water velocity and soil detachment, the PLER model is easily applicable to different agricultural scenarios. The results indicate appropriate model performance and a high correlation between measured and predicted data with both Nash–Sutcliffe efficiency (Ef) and correlation coefficient (r2) having values > 0.9. With the simple input data needs, PLER model is a useful tool for daily runoff and soil erosion modeling in small hilly watersheds in humid tropical areas. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献