全文获取类型
收费全文 | 275篇 |
免费 | 17篇 |
专业分类
测绘学 | 32篇 |
大气科学 | 34篇 |
地球物理 | 93篇 |
地质学 | 69篇 |
海洋学 | 11篇 |
天文学 | 45篇 |
综合类 | 1篇 |
自然地理 | 7篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 7篇 |
2020年 | 14篇 |
2019年 | 9篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 36篇 |
2012年 | 18篇 |
2011年 | 21篇 |
2010年 | 12篇 |
2009年 | 16篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1990年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
排序方式: 共有292条查询结果,搜索用时 15 毫秒
61.
The IVS Intensive sessions are single-baseline, 1-h VLBI sessions carried out everyday in order to determine Universal Time
(UT1). We investigate different possibilities to improve the results of such sessions. We do this investigation by extracting
2-h single-baseline sessions from the CONT08 data set. These are analysed like normal Intensives, and the results are compared
to the results of the analysis of the full CONT08 data set. We find that tropospheric asymmetry is the major error source
for the single-baseline sessions. It is possible to improve the accuracy of the estimated UT1 either by using accurate a priori
tropospheric gradients or by estimating gradients in the data analysis. 相似文献
62.
Agnès Mazot Alain Bernard Tobias Fischer Salvatore Inguaggiato Igan S. Sutawidjaja 《Journal of Volcanology and Geothermal Research》2008
Papandayan is a stratovolcano situated in West Java, Indonesia. Since the last magmatic eruption in 1772, only few hydrothermal explosions have occurred. An explosive eruption occurred in November 2002 and ejected ash and altered rocks. The altered rocks show that an advanced argillic alteration took place in the hydrothermal system by interaction between acid fluids and rocks. Four zones of alteration have been defined and are limited in extension and shape along faults or across permeable structures at different levels beneath the active crater of the volcano. 相似文献
63.
64.
An investigation of low-resolution ratio spectra of Jupiter, Saturn, and Titan in the region 5400–6500 Å has permitted new evaluations of ammonia absorption bands. The distribution of ammonia over the disk of Jupiter is very inhomogeneous. The carbon-to-nitrogen ratio is distinctly different from the solar value, but this is probably a result of uneven mixing of methane and ammonia, as suggested previously by Kuiper, rather than a compositional anomaly. The abundance of ammonia on Saturn also shows spatial variations, but appears constant in time over a 3-yr period. Two weak, unidentified absorptions were discovered in the red region of Titan's spectrum, in the absence of any detectable ammonia. The new upper limit is ηN < 120 cm-am. 相似文献
65.
Vladimir A. Krasnopolsky Jean Pierre Maillard Tobias C. Owen Robert A. Toth Michael D. Smith 《Icarus》2007,192(2):396-403
Oxygen and carbon isotope ratios in the martian CO2 are key values to study evolution of volatiles on Mars. The major problems in spectroscopic determinations of these ratios on Mars are uncertainties associated with: (1) equivalent widths of the observed absorption lines, (2) line strengths in spectroscopic databases, and (3) thermal structure of the martian atmosphere during the observation. We have made special efforts to reduce all these uncertainties. We observed Mars using the Fourier Transform Spectrometer at the Canada–France–Hawaii Telescope. While the oxygen and carbon isotope ratios on Mars were byproducts in the previous observations, our observation was specifically aimed at these isotope ratios. We covered a range of 6022 to 6308 cm−1 with the highest resolving power of ν/δν=3.5×105 and a signal-to-noise ratio of 180 in the middle of the spectrum. The chosen spectral range involves 475 lines of the main isotope, 184 lines of 13CO2, 181 lines of CO18O, and 119 lines of CO17O. (Lines with strengths exceeding 10−27 cm at 218 K are considered here.) Due to the high spectral resolution, most of the lines are not blended. Uncertainties of retrieved isotope abundances are in inverse proportion to resolving power, signal-to-noise ratio, and square root of the number of lines. Laboratory studies of the CO2 isotope spectra in the range of our observation achieved an accuracy of 1% in the line strengths. Detailed observations of temperature profiles using MGS/TES and data on temperature variations with local time from two GCMs are used to simulate each absorption line at various heights in each part of the instrument field of view and then sum up the results. Thermal radiation of Mars' surface and atmosphere is negligible in the chosen spectral range, and this reduces errors associated with uncertainties in the thermal structure on Mars. Using a combination of all these factors, the highest accuracy has been achieved in measuring the CO2 isotope ratios: 13C/12C = 0.978 ± 0.020 and 18O/16O = 1.018 ± 0.018 times the terrestrial standards. Heavy isotopes in the atmosphere are enriched by nonthermal escape and sputtering, and depleted by fractionation with solid-phase reservoirs. The retrieved ratios show that isotope fractionation between CO2 and oxygen and carbon reservoirs in the solid phase is almost balanced by nonthermal escape and sputtering of O and C from Mars. 相似文献
66.
67.
Turbulent flux observations and modelling over a shallow lake and a wet grassland in the Nam Co basin,Tibetan Plateau 总被引:1,自引:1,他引:1
Tobias?BiermannEmail author Wolfgang?Babel Weiqiang?Ma Xuelong?Chen Elisabeth?Thiem Yaoming?Ma Thomas?Foken 《Theoretical and Applied Climatology》2014,116(1-2):301-316
The Tibetan Plateau plays an important role in the global water cycle and is strongly influenced by climate change. While energy and matter fluxes have been more intensely studied over land surfaces, a large proportion of lakes have either been neglected or parameterised with simple bulk approaches. Therefore, turbulent fluxes were measured over wet grassland and a shallow lake with a single eddy-covariance complex at the shoreline in the Nam Co basin in summer 2009. Footprint analysis was used to split observations according to the underlying surface, and two sophisticated surface models were utilised to derive gap-free time series. Results were then compared with observations and simulations from a nearby eddy-covariance station over dry grassland, yielding pronounced differences. Observations and footprint integrated simulations compared well, even for situations with flux contributions including grassland and lake. The accessibility problem for EC measurements on lakes can be overcome by combining standard meteorological measurements at the shoreline with model simulations, only requiring representative estimates of lake surface temperature. 相似文献
68.
Will climate change exacerbate water stress in Central Asia? 总被引:3,自引:0,他引:3
Tobias Siegfried Thomas Bernauer Renaud Guiennet Scott Sellars Andrew W. Robertson Justin Mankin Peter Bauer-Gottwein Andrey Yakovlev 《Climatic change》2012,112(3-4):881-899
Millions of people in the geopolitically important region of Central Asia depend on water from snow- and glacier-melt driven international rivers, most of all the Syr Darya and Amu Darya. The riparian countries of these rivers have experienced recurring water allocation conflicts ever since the Soviet Union collapsed. Will climate change exacerbate water stress and thus conflicts? We have developed a coupled climate, land-ice and rainfall-runoff model for the Syr Darya to quantify impacts and show that climatic changes are likely to have consequences on runoff seasonality due to earlier snow-melt. This will increase water stress in unregulated catchments because less water will be available for irrigation in the summer months. Threats from geohazards, above all glacier lake outbursts, are likely to increase as well. The area at highest risk is the densely populated, agriculturally productive, and politically unstable Fergana Valley. Targeted infrastructural developments will be required in the region. If the current mismanagement of water and energy resources can be replaced with more effective resource allocation mechanisms through the strengthening of transboundary institutions, Central Asia will be able to successfully address these future climate-related challenges. 相似文献
69.
Deep massive sulphide exploration using 2D and 3D geoelectrical and induced polarization data in Skellefte mining district,northern Sweden 下载免费PDF全文
Saman Tavakoli Tobias E. Bauer Thorkild M. Rasmussen Pär Weihed Sten‐Åke Elming 《Geophysical Prospecting》2016,64(6):1602-1619
Geoelectrical and induced polarization data from measurements along three profiles and from one 3D survey are acquired and processed in the central Skellefte District, northern Sweden. The data were collected during two field campaigns in 2009 and 2010 in order to delineate the structures related to volcanogenic massive sulphide deposits and to model lithological contacts down to a maximum depth of 1.5 km. The 2009 data were inverted previously, and their joint interpretation with potential field data indicated several anomalous zones. The 2010 data not only provide additional information from greater depths compared with the 2009 data but also cover a larger surface area. Several high‐chargeability low‐resistivity zones, interpreted as possible massive sulphide mineralization and associated hydrothermal alteration, are revealed. The 3D survey data provide a detailed high‐resolution image of the top ~450 m of the upper crust around the Maurliden East, North, and Central deposits. Several anomalies are interpreted as new potential prospects in the Maurliden area, which are mainly concentrated in the central conductive zone. In addition, the contact relationship between the major geological units, e.g., the contact between the Skellefte Group and the Jörn Intrusive Complex, is better understood with the help of 2010 deep‐resistivity/chargeability data. The bottommost part of the Vargfors basin is imaged using the 2010 geoelectrical and induced polarization data down to ~1‐km depth. 相似文献
70.
Karst aquifers represent important water resources in many parts of the world. Unfortunately, karst aquifers are characterised
by high contamination risks. This paper presents a travel time based method for the estimation of karst groundwater vulnerability.
It considers (1) physics-based lateral flow within the uppermost weathered zone (epikarst) in a limestone-dominated region
and (2) high velocities of vertical infiltration at discrete infiltration points (e.g. sinkholes) or lines (e.g. dry valleys,
faults). Consequently, the Transit Time Method honours the actual flow path within the unsaturated zone of a karst aquifer
system. A test site in Northern Jordan was chosen for the demonstration of the assessment technique, i.e. the catchment area
of the Qunayyah Spring north of the capital Amman. The results demonstrate that zones of highest vulnerability lie within
valleys and nearby main fault zones. It also reveals that regions, categorised as protected areas by other methods due to
thick unsaturated zones, contribute to a major degree to the total risk. 相似文献