全文获取类型
收费全文 | 2632篇 |
免费 | 83篇 |
国内免费 | 73篇 |
专业分类
测绘学 | 78篇 |
大气科学 | 392篇 |
地球物理 | 615篇 |
地质学 | 665篇 |
海洋学 | 684篇 |
天文学 | 193篇 |
综合类 | 45篇 |
自然地理 | 116篇 |
出版年
2023年 | 5篇 |
2022年 | 25篇 |
2021年 | 40篇 |
2020年 | 48篇 |
2019年 | 54篇 |
2018年 | 127篇 |
2017年 | 117篇 |
2016年 | 162篇 |
2015年 | 88篇 |
2014年 | 172篇 |
2013年 | 231篇 |
2012年 | 120篇 |
2011年 | 156篇 |
2010年 | 160篇 |
2009年 | 162篇 |
2008年 | 152篇 |
2007年 | 144篇 |
2006年 | 120篇 |
2005年 | 115篇 |
2004年 | 117篇 |
2003年 | 75篇 |
2002年 | 60篇 |
2001年 | 55篇 |
2000年 | 39篇 |
1999年 | 34篇 |
1998年 | 26篇 |
1997年 | 19篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 2篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有2788条查询结果,搜索用时 765 毫秒
551.
552.
Song-You Hong Young Cheol Kwon Tae-Hun Kim Jung-Eun Esther Kim Suk-Jin Choi In-Hyuk Kwon Junghan Kim Eun-Hee Lee Rae-Seol Park Dong-Il Kim 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):267-292
The Korea Institute of Atmospheric Prediction Systems (KIAPS) began a national project to develop a new global atmospheric model system in 2011. The ultimate goal of this 9-year project is to replace the current operational model at the Korea Meteorological Administration (KMA), which was adopted from the United Kingdom’s Meteorological Office’s unified model (UM) in 2010. The 12-km Korean Integrated Model (KIM) system, consisting of a spectral-element non-hydrostatic dynamical core on a cubed sphere grid and a state-of-the-art physics parameterization package, has been launched in a real-time forecast framework, with initial conditions obtained via the advanced hybrid four-dimensional ensemble variational data assimilation (4DEnVar) over its native grid. A development strategy for KIM and the evolution of its performance in medium-range forecasts toward a world-class global forecast system are described. Outstanding issues in KIM 3.1 as of February 2018 are discussed, along with a future plan for operational deployment in 2020. 相似文献
553.
Geochemical processes underlying a sharp contrast in groundwater arsenic concentrations in a village on the Red River delta,Vietnam 总被引:1,自引:0,他引:1
554.
Søren Jessen Flemming Larsen Dieke Postma Pham Hung Viet Nguyen Thi Ha Pham Quy Nhan Dang Duc Nhan Mai Thanh Duc Nguyen Thi Minh Hue Trieu Duc Huy Tran Thi Luu Dang Hoang Ha Rasmus Jakobsen 《Applied Geochemistry》2008
To study the geological control on groundwater As concentrations in Red River delta, depth-specific groundwater sampling and geophysical logging in 11 monitoring wells was conducted along a 45 km transect across the southern and central part of the delta, and the literature on the Red River delta’s Quaternary geological development was reviewed. The water samples (n = 30) were analyzed for As, major ions, Fe2+, H2S, NH4, CH4, δ18O and δD, and the geophysical log suite included natural gamma-ray, formation and fluid electrical conductivity. The SW part of the transect intersects deposits of grey estuarine clays and deltaic sands in a 15–20 km wide and 50–60 m deep Holocene incised valley. The NE part of the transect consists of 60–120 m of Pleistocene yellowish alluvial deposits underneath 10–30 m of estuarine clay overlain by a 10–20 m veneer of Holocene sediments. The distribution of δ18O-values (range −12.2‰ to −6.3‰) and hydraulic head in the sample wells indicate that the estuarine clay units divide the flow system into an upper Holocene aquifer and a lower Pleistocene aquifer. The groundwater samples were all anoxic, and contained Fe2+ (0.03–2.0 mM), Mn (0.7–320 μM), SO4 (<2.1 μM–0.75 mM), H2S (<0.1–7.0 μM), NH4 (0.03–4.4 mM), and CH4 (0.08–14.5 mM). Generally, higher concentrations of NH4 and CH4 and low concentrations of SO4 were found in the SW part of the transect, dominated by Holocene deposits, while the opposite was the case for the NE part of the transect. The distribution of the groundwater As concentration (<0.013–11.7 μM; median 0.12 μM (9 μg/L)) is related to the distribution of NH4, CH4 and SO4. Low concentrations of As (?0.32 μM) were found in the Pleistocene aquifer, while the highest As concentrations were found in the Holocene aquifer. PHREEQC-2 speciation calculations indicated that Fe2+ and H2S concentrations are controlled by equilibrium for disordered mackinawite and precipitation of siderite. An elevated groundwater salinity (Cl range 0.19–65.1 mM) was observed in both aquifers, and dominated in the deep aquifer. A negative correlation between aqueous As and an estimate of reduced SO4 was observed, indicating that Fe sulphide precipitation poses a secondary control on the groundwater As concentration. 相似文献
555.
This study was performed to investigate the operating status, evaluate the problems, and discuss possible improvement methods
of passive treatment systems for acid mine drainage (AMD) in South Korea. Thirty-five passive treatment systems in 29 mines
have been constructed from 1996 to 2002 using successive alkalinity producing systems (SAPS) as the main treatment process.
We investigated 29 systems (two for metal mines), 19 of which revealed various problems. Overflows of drainage from SAPS,
wetland, or oxidation ponds were caused by the flow rate exceeding the capacities of the facilities or by the reduced permeability
of the organic substance layer. Leakages occurred at various parts of the systems. In some cases, clogged and broken pipes
at the mouths of the mine adits made the whole system unusable. Some systems showed very low efficiencies without apparent
leakage or overflow. Even though the systems showed fairly good efficiencies in metal removal ratios (mainly iron) and pH
control; sulfate removal rates were very poor except in three systems, which may indicate very poor sulfate reductions with
sulfate reducing bacteria (SRB) as a means. 相似文献
556.
Chemical weathering was investigated by collecting samples from five selected weathering profiles in a high elevation granitic
environment located in Seoul, Korea. The overall changes of chemistry and mineralogical textures were examined reflecting
weathering degrees of the samples, using polarization microscopy, X-ray diffraction (XRD), electron probe micro analysis (EPMA),
X-ray fluorescence spectroscopy (XRF), and inductively coupled plasma–mass spectroscopy (ICP–MS). The chemical distribution
in the weathering profiles shows that few trace elements are slightly immobile, whereas most major (particularly Ca and Na)
and trace elements are mobile from the beginning of the granite weathering. On the other hand, there were mineralogical changes
initiated from a plagioclase breakdown, which shows a characteristic circular dissolved pattern caused by a preferential leaching
of Ca cation along grain boundaries and zoning. The biotite in that region is also supposed to be sensitive to exterior environmental
condition and may be easily dissolved by acidic percolated water. As a result, it seems that some rock-forming minerals in
the granitic rock located in Seoul are significantly unstable due to the environmental condition of acidic rainfall and steep
slopes, where they are susceptible to be dissolved incongruently leading some elements to be highly depleted. 相似文献
557.
G. G. Katul R. Leuning J. Kim O. T. Denmead A. Miyata Y. Harazono 《Boundary-Layer Meteorology》2001,98(1):103-125
Source/sink strengths and vertical fluxdistributions of carbon dioxide within and above arice canopy were modelled using measured meanconcentration profiles collected during aninternational rice experiment in Okayama, Japan (IREX96). The model utilizes an Eulerian higher-orderclosure approach that permits coupling of scalar andmomentum transport within vegetation to infer sourcesand sinks from mean scalar concentration profiles; theso-called `inverse problem'. To compute the requiredvelocity statistics, a Eulerian second-order closuremodel was considered. The model well reproducedmeasured first and second moment velocity statisticsinside the canopy. Using these modelled velocitystatistics, scalar fluxes within and above the canopywere computed and compared with CO2eddy-correlation measurements above the canopy. Goodagreement was obtained between model calculations offluxes at the top of the canopy and measurements. Close to the ground, the model predicted higherrespiratory fluxes when the paddy was drained comparedto when it was flooded. This is consistent with thefloodwater providing a barrier to diffusion ofCO2 from the soil to the atmosphere. TheEulerian sources and flux calculations were alsocompared to source and flux distributions estimatedindependently using a Lagrangian Localized Near Fieldtheory, the first study to make such a comparison.Some differences in source distributions werepredicted by these analyses. Despite this, thecalculated fluxes by the two approaches compared wellprovided a closure constant, accounting for theinfluence of `near-field' sources in the Eulerian fluxtransport term, was given a value of 1.5 instead ofthe value of 8 found in laboratory studies. 相似文献
558.
INTRODUCTIONInternet,aglobalnetworkofcomputersconnectedthroughcommunicationdevices,providesGISusersanaccesstoremotegeographicdata .Theweb basedGIS ,akindofinternet basedGIStoolfortheaccesstoremotegeographicinformation ,ispro posedinthispaper.Nowadays ,thewe… 相似文献
559.
朝鲜Taegok地区碳酸盐岩中金银成矿作用特征Taegok地区发现的Au-Ag矿体,分布在上元古界Sadang-u岩系(碳酸盐岩),可能属于卡林型金银矿床.这种矿体具有如下特征:1.金银矿体产于碳酸盐岩(白云岩)中.2.金银矿体在成因上与辉长-辉绿岩... 相似文献
560.
Alexandre Ganachaud Carl Wunsch Myung-Chan Kim Byron Tapley 《Geophysical Journal International》1997,128(3):708-722
A global estimate of the absolute oceanic general circulation from a geostrophic inversion of in situ hydrographic data is tested against and then combined with an estimate obtained from TOPEX/POSEIDON altimetric data and a geoid model computed using the JGM-3 gravity-field solution. Within the quantitative uncertainties of both the hydrographic inversion and the geoid estimate, the two estimates derived by very different methods are consistent. When the in situ inversion is combined with the altimetry/geoid scheme using a recursive inverse procedure, a new solution, fully consistent with both hydrography and altimetry, is found. There is, however, little reduction in the uncertainties of the calculated ocean circulation and its mass and heat fluxes because the best available geoid estimate remains noisy relative to the purely oceano-graphic inferences. The conclusion drawn from this is that the comparatively large errors present in the existing geoid models now limit the ability of satellite altimeter data to improve directly the general ocean circulation models derived from in situ measurements. Because improvements in the geoid could be realized through a dedicated spaceborne gravity recovery mission, the impact of hypothetical much better, future geoid estimates on the circulation uncertainty is also quantified, showing significant hypothetical reductions in the uncertainties of oceanic transport calculations, Full ocean general circulation models could better exploit both existing oceanographic data and future gravity-mission data, but their present use is severely limited by the inability to quantify their error budgets. 相似文献