全文获取类型
收费全文 | 84篇 |
免费 | 3篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 10篇 |
地球物理 | 16篇 |
地质学 | 33篇 |
海洋学 | 9篇 |
天文学 | 5篇 |
自然地理 | 7篇 |
出版年
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 1篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1972年 | 3篇 |
1969年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有87条查询结果,搜索用时 15 毫秒
61.
62.
Modelling Indonesian rainfall with a coupled regional model 总被引:2,自引:0,他引:2
Edvin Aldrian Dmitry Sein Daniela Jacob Lydia Dümenil Gates Ralf Podzun 《Climate Dynamics》2005,25(1):1-17
Long-term high-resolution coupled climate model simulations using the Max Planck Institute Regional Climate Model and the
Max Planck Institute Ocean Model have been performed with boundary forcings from two reanalyses: firstly from the European
Centre for Medium-Range Weather Forecasts, and secondly from the joint reanalysis of the National Centers for Environmental
Prediction and the National Center for Atmospheric Research. This study employs a special coupling setup using a regional
atmospheric model and a global ocean model. The latter model applies a special conformal grid from a bipolar orthogonal spherical
coordinate system, which allows irregular positions of the poles and focuses on the detail over the Maritime Continent. The
coupled model was able to simulate stable and realistic rainfall variabilities without flux correction and at two different
ocean resolutions. The coupled system is integrated for a period between 1979 and 1993 and the results are then compared to
those from uncoupled runs and from observation. The results show improved performance after coupling: a remarkable reduction
of overestimated rainfall over the sea for the atmospheric model and of warm SST biases for the ocean model. There is no significant
change in rainfall variability at higher ocean model resolution, but the ocean circulation shows less transport variability
within the Makassar Strait in comparison to observations.
This paper has not been published or considered by any other journal in any language. 相似文献
63.
Holocene humidity fluctuations in Sweden inferred from dendrochronology and peat stratigraphy 总被引:1,自引:0,他引:1
BJÖRN ERIK GUNNARSON ERS BORGMARK STEFAN WASTEGÅRD 《Boreas: An International Journal of Quaternary Research》2003,32(2):347-360
Tree-ring and peat stratigraphy data were examined back to 5000 BC in order to identify and compare humidity changes in Fennoscandia. The temporal variation in distribution of Scots pine ( Pinus sylvestris L.) was used as a measure of past lake-level fluctuations in central Sweden. The chronology, which spans 2893 BC–AD 1998 with minor gaps in AD 887–907 and 1633–1650 BC and with additional floating chronologies back to 4868 BC, was cross-dated and fixed to an absolute timescale using a chronology from Torneträsk, northern Sweden. The peat stratigraphy from the Stömyren peat bog, south-central Sweden, was transformed into humification indices to evaluate humidity changes during the past 8000 years. The peat chronology is established by four tephra datings and eight 14 C datings. Synchronous periods of drier conditions, interpreted from regeneration and the mortality pattern of pine, tree-ring chronology and peat humification, were recognized at c. 4900–4800 BC, 2400–2200 BC, 2100–1800 BC, 1500–1100 BC, AD 50–200, AD 400–600 and AD 1350–1500. Possible wetter periods were encountered at 3600–3400 BC, 3200–2900 BC, 2200–2100 BC, 1700–1500 BC, 1100–900 BC, 100 BC-AD 50, AD 200–400, AD 750–900 and AD 1550–1700. The wet and dry periods revealed by the tree rings and peat stratigraphy data indicate considerable humidity changes in the Holocene. 相似文献
64.
Estimating groundwater recharge in a cold desert environment in northern China using chloride 总被引:4,自引:0,他引:4
Understanding sources and rates of recharge to the Badain Jaran Desert in northern China is important for assessing sustainability of the area’s oasis lake ecosystem and its water resources in general. For this purpose, direct recharge was investigated with the chloride mass balance method for 18 unsaturated zone profiles (6–16 m depth). Spatial variability is low across the area (range in mean Cl in profiles: 62–164 mg/L Cl), largely attributable to the uniformity of sandy unsaturated zone conditions. No strong correlations between environmental factors of profile locations and recharge rates were found, though a weak relationship between recharge and vegetation density was suggested. The study area’s complex dune morphology appears to have no measurable impact on recharge variability. Mean estimated diffuse recharge is 1.4 mm/year (1.0–3.6 mm/year for 95% confidence level), approximately 1.7% of mean annual precipitation. Temporal fluctuations in recharge due to climate variability are apparent and there is good correspondence in temporal trends over a time span of 200–300 years. Water balance considerations indicate that direct recharge is insufficient to support the numerous perennial lakes in the study area, suggesting that diffuse recharge presently plays a minor role in the overall water balance of the desert’s shallow Quaternary aquifer. 相似文献
65.
This paper reports on the new application of polarized extended X-ray absorption fine structure (P-EXAFS) spectroscopy to fine-grained layer silicates taking the Garfield nontronite as a case study. Up to now application of P-EXAFS to structural studies of layer silicates has been restricted to single phyllosilicate crystals (Manceau et al. 1988; Manceau et al. 1990), but we show here that P-EXAFS can rigorously be applied to self-supporting clay films without loss of spatial resolution. The quantitative analysis of P-EXAFS requires however the preparation of highly oriented clay films, the orientation distribution of which can be assessed by texture goniometry. The Fe K-edge linear dichroism measurements were simulated by ab initio EXAFS modeling performed on a nontronite cluster whose structure was refined by distance-valence least-squares calculations. It is shown that ab initio modeling quantitatively accounts for the angular dependence of experimental EXAFS spectra. These calculations allowed for the identification of the fundamental character of single- and multiple-scattering paths of the photoelectron, and the structural interpretation of all spectral features observed up to 6.5?Å for the in-plane and out-of-plane radial structure functions of nontronite. In practice, P-EXAFS measurements allow the determination of the flattening angle of Fe(O,OH)6 octahedra, cations distribution in the octahedral sheet with an enhanced sensitivity, and differentiation between dioctahedral and trioctahedral structures. 相似文献
66.
67.
Chloride and the environmental isotopes as the indicators of the groundwater recharge in the Gobi Desert,northwest China 总被引:5,自引:0,他引:5
The long term recharge in Gobi Desert from Hexi Corridor to Inner Mongolia Plateau was estimated to be 1 mm year−1 by using the chloride mass balance method from one unsaturated zone profile, which shows that no effective modern recharge
is taking place. A good rainfall database from Zhangye provides definition of the stable isotopic composition of modern rainfall.
The signature of groundwater from the late Pleistocene differs markedly from that of the Holocene, shown clearly by the compositions
of −10.5‰ δ18O as compared with values of −7‰ at the present day. It is apparent that the groundwaters in the Minqin Basin, Ejina Basin
and feeding the lake system of the Badain Jaran are part of a regional flow network related to a wetter past climate as source
of recharge. The recharge source in the past and to a limited extent in the more arid conditions of the present day included
the foothills of the mountains of the Tibetan Plateau. The tritium age determinations accurate to the year are impossible
and of no meaning to groundwater studies. A tritium value in the groundwater means multiple recharge ages in this region. 相似文献
68.
Y. Jeffrey Yang Richard D. Spencer Todd M. Gates 《Ground Water Monitoring & Remediation》1995,15(1):101-106
This paper presents analytical solutions for determining non-steady-state capture zones produced by a single recovery well and steady-state capture zones produced by multiple recovery wells. Analysis of non-steady-slate capture zones is based on the lime-dependent location of caplure zone stagnation points and the geometric similarity between steady-slate and non-steady-state capture zones. The analytical solution of steady-state capture zones is obtained from spatial variations of discharge potential across the capture zone boundary. Both capture zone analyses are based on the assumptions of uniform flow field with a constant hydraulic conductivity, the Dupuit assumption of insignificant vertical flow, a negligible delayed yield, and a fully penetrating well with a constant pumping rate. For a ground water pump-and-trcat remediation program, the pumping rate and well location design variables can be adjusted to ensure containment of the ground water contaminant plume. 相似文献
69.
巴丹吉林沙漠南部高大沙丘包气带水分空间分布特征研究 总被引:3,自引:1,他引:2
水是影响沙漠生态系统的主要因子,决定着多年生植物的种类和数量。受恶劣的自然条件和研究手段限制,目前对沙漠地区包气带水分时空动态变化的研究相对薄弱。以巴丹吉林沙漠南部湖泊密集区为研究对象,通过随机采样和同一坡向剖面采样,综合运用DCCA和地统计学分析方法,揭示0~10 m较深层包气带沙丘水分的空间变化规律和局部控制因子对包气带水分的影响。结果表明,0~10 m沙丘包气带水分变化曲线呈指数、对数和对数正态分布3种类型,分别受地下水或下伏黏土层的毛管作用、湖心距和综合地形因子控制;影响沙漠包气带水分空间变化的主要局部控制因子与小流域的研究结果差异显著。地形、植被等局部控制因子影响对数分布型包气带水分的深度为表层1 m,而影响对数正态分布型的深度为3~4 m;沙丘水分随相对湖面高程空间变化差异显著,而空间相关距离则不显著。 相似文献
70.
This paper focuses on using urea hydrolysis as a bio-grouting process to increase the strength of crushed aggregates commonly used in stone columns. Various reagent phases (2, 4, 6 and 12 phases) consisted of alternately percolating solutions containing bacterial suspension and cementation solution through the soil column. In addition, a multi-soil lift strategy with options of up to four soil lifts was undertaken to test the applicability of bio-grout to cement crushed aggregate columns. While the average amount of calcium carbonate precipitation was roughly unchanged in both techniques, the distribution within the crushed aggregate columns was heterogeneous. However, the distribution of the precipitated calcium carbonate is almost uniform in crushed aggregates treated by a two-soil lift strategy and a four-phase treatment strategy. It is also deducted that both techniques can be combined to gain a uniform calcium carbonate and strength along a long sand/stone column. Furthermore, a one-soil lift resulted in higher strength than using multi-soil lifts, and a maximum strength of approximately 2.3 MPa was achieved using 4-reagent phase treatment strategy. Scanning electron microscopy and electron dispersive spectroscopy analysis validate that calcium carbonate was deposited as white crystals on the surface of the crushed aggregate particles. 相似文献