全文获取类型
收费全文 | 209篇 |
免费 | 11篇 |
国内免费 | 20篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 24篇 |
地球物理 | 68篇 |
地质学 | 86篇 |
海洋学 | 17篇 |
天文学 | 19篇 |
综合类 | 1篇 |
自然地理 | 13篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 11篇 |
2015年 | 13篇 |
2014年 | 9篇 |
2013年 | 14篇 |
2012年 | 4篇 |
2011年 | 13篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 3篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1952年 | 4篇 |
1950年 | 1篇 |
1920年 | 1篇 |
1914年 | 1篇 |
1913年 | 1篇 |
排序方式: 共有240条查询结果,搜索用时 15 毫秒
1.
2.
Aude?ValadeEmail authorView authors OrcID profile Sebastiaan?Luyssaert Patrick?Vallet Sylvestre?Njakou Djomo Ingride?Jesus Van Der Kellen Valentin?Bellassen 《Carbon balance and management》2018,13(1):26
Background
Concern about climate change has motivated France to reduce its reliance on fossil fuel by setting targets for increased biomass-based renewable energy production. This study quantifies the carbon costs and benefits for the French forestry sector in meeting these targets. A forest growth and harvest simulator was developed for French forests using recent forest inventory data, and the wood-use chain was reconstructed from national wood product statistics. We then projected wood production, bioenergy production, and carbon balance for three realistic intensification scenarios and a business-as-usual scenario. These intensification scenarios targeted either overstocked, harvest-delayed or currently actively managed stands.Results
All three intensification strategies produced 11.6–12.4 million tonnes of oil equivalent per year of wood-based energy by 2026, which corresponds to the target assigned to French wood-energy to meet the EU 2020 renewable energy target. Sustaining this level past 2026 will be challenging, let alone further increasing it. Although energy production targets can be reached, the management intensification required will degrade the near-term carbon balance of the forestry sector, compared to continuing present-day management. Even for the best-performing intensification strategy, i.e., reducing the harvest diameter of actively managed stands, the carbon benefits would only become apparent after 2040. The carbon balance of a strategy putting abandoned forests back into production would only break even by 2055; the carbon balance from increasing thinning in managed but untended stands would not break even within the studied time periods, i.e. 2015–2045 and 2046–2100. Owing to the temporal dynamics in the components of the carbon balance, i.e., the biomass stock in the forest, the carbon stock in wood products, and substitution benefits, the merit order of the examined strategies varies over time.Conclusions
No single solution was found to improve the carbon balance of the forestry sector by 2040 in a way that also met energy targets. We therefore searched for the intensification scenario that produces energy at the lowest carbon cost. Reducing rotation time of actively managed stands is slightly more efficient than targeting harvest-delayed stands, but in both cases, each unit of energy produced has a carbon cost that only turns into a benefit between 2060 and 2080.3.
The development of groundwater favourability map is an effective tool for the sustainability management of groundwater resources in typical agricultural regions, such as southern Perak Province, Malaysia. Assessing the potentiality and pollution vulnerability of groundwater is a fundamental phase of favourability mapping. A geographic information system (GIS)-based Boolean operator of a spatial analyst module was applied to combine a groundwater potentiality map (GPM) model and a groundwater vulnerability to pollution index (GVPI) map, thereby establishing the favourable zones for drinking water exploration in the investigated area. The area GPM model was evaluated by applying a GIS-based Dempster–Shafer–evidential belief function model. In the evaluation, six geoelectrically determined groundwater potential conditioning factors (i.e. overburden resistivity, overburden thickness, aquifer resistivity, aquifer thickness, aquifer transmissivity and hydraulic conductivity) were synthesized by employing the probability-based algorithms of the model. The generated thematic maps of the seven hydrogeological parameters of the DRASTIC model were considered as pollution potential conditioning factors and were analysed with the developed ordered weighted average–DRASTIC index model algorithms to construct the GVPI map. Approximately 88.8 and 85.71% prediction accuracies for the Groundwater Potentiality and GVPI maps were established using the reacting operating characteristic curve method and water quality status–vulnerability zone relationship scheme, respectively. Finally, the area groundwater favourability map (GFM) model was produced by applying a GIS-based Boolean operator on the Groundwater Potentiality and GVPI maps. The GFM model reveals three distinct zones: ‘not suitable’, ‘less suitable’ and ‘very suitable’ zones. The area analysis of the GFM model indicates that more than 50% of the study area is covered by the ‘very suitable’ zones. Results produce a suitability map that can be used by local authorities for the exploitation and management of drinking water in the area. The study findings can also be applied as a tool to help increase public awareness of groundwater issues in developing countries. 相似文献
4.
V. A. San’kov A. V. Parfeevets A. V. Lukhnev A. I. Miroshnichenko S. V. Ashurkov 《Geotectonics》2011,45(5):378-393
Comprehensive analysis of the parameters characterizing contemporary and neotectonic deformations of the Earth’s crust and
upper mantle developed in the Mongolia-Siberia area is presented. The orientation of the axes of horizontal deformation in
the geodetic network from the data of GPS geodesy is accepted as an indicator of current deformations at the Earth’s surface.
At the level of the middle crust, this is the orientation of the principal axes of the stress-tensors calculated from the
mechanisms of earthquake sources. The orientation of the axes of stress-tensors reconstructed on the basis of structural data
is accepted as an indicator of Late Cenozoic deformations in the upper crust. Data on seismic anisotropy of the upper mantle
derived from published sources on the results of splitting of shear waves from remote earthquakes serve as indicators of deformation
in the mantle. It is shown that the direction of extension (minimum compression) in the studied region coincides with the
direction of anisotropy of the upper mantle, the median value of which is 310–320° NW. Seismic anisotropy is interpreted as
the ordered orientation of olivine crystals induced by strong deformation owing to the flow of mantle matter. The observed
mechanical coupling of the crust and upper mantle of the Mongolia-Siberia mobile area shows that the lithospheric mantle participated
in the formation of neotectonic structural elements and makes it possible to ascertain the main processes determining the
Late Cenozoic tectogenesis in this territory. One of the main mechanisms driving neotectonic and contemporary deformations
in the eastern part of the Mongolia-Siberia area is the long-living and large-scale flow of the upper mantle matter from the
northwest to the southeast, which induces both the movement of the northern part of the continent as a whole and the divergence
of North Eurasia and the Amur Plate with the formation of the Baikal Rift System. In the western part of the region, deformation
of the lithosphere is related to collisional compression, while in the central part, it is due to the dynamic interaction
of these two large-scale processes. 相似文献
5.
大别山构造地貌的DEM初步分析 总被引:6,自引:1,他引:6
以地理信息系统(GIS)为平台,利用航天飞机雷达地形测量(SRTM)数据,构建了大别造山带地区的数字高程模型(DEM),对大别山地区的构造地貌进行了模拟解译分析.研究表明,大别山在造山带走向和垂直走向的方向上都是中间高、两边低,两边地势低的部位发育断陷盆地.SRTM DEM地貌图显示,郯庐等大断裂地貌特征明显,断裂构造严格控制了水系的发育,大别山水系多呈格子状分布,在地貌上主要表现为河流的大角度转弯以及主支流近直角交汇;由于本区地壳沿断裂作差异性升降运动,造成地堑谷、断块山和断陷盆地并存的地貌特点.本文统计分析了坡度与高程之间的相互关系,并提取了夷平面信息. 相似文献
6.
Cione Alberto L. Tonni Eduardo P. San Cristóbal Jorge Hernández Pedro J. Benítez Adrián Bordignon Fernando Perí Jorge A. 《Earth, Moon, and Planets》2002,91(1):9-24
Ten oblong aligned depressions in the Río Cuarto area (provincia de Córdoba, Argentina) were supposed to be the result of very-low-angle Holocene meteoroid impacts. However, we consider that authors that studied the structures did not demonstrated their extraterrestrial origin. We suggest that an eolian origin for the structures of Río Cuarto is more likely. Actually, these landforms integrate large systems of similar deflation/accumulation geoforms aligned according to predominant winds during different periods. 相似文献
7.
Cheng San Zhang Zhi-Yong Zhou Feng Li Man Chen Hui Shi Fu-Sheng Huang Lin-Pin Li Yong 《应用地球物理》2021,(3):375-385
A three-dimensional (3D) step-by-step inversion strategy for audio magnetotellurics(AMT) is investigated in this study.The objective function is minimized by it... 相似文献
8.
Puerto Galera Bay is a coastal lagoon with a variety of marine habitats and high species diversity. It is an area in the Phillippines where the growing influence of human activities is affecting the quality of its marine resources. This study examined the distribution and behaviour of nutrients and the physical hydrography of Puerto Galera Bay and determined how its physico-chemical nature affected the condition of biotic components in the bay. The relative importance of the nitrogen and phosphorus signals were used as indicators to implicate the influence of sewage and run-off into the bay. A nutrient pool accumulated in the bay as a result of low flushing rates. The interaction of hydrodynamic forcing with the biota have implications on the phytoplankton production and coral communities in the area. 相似文献
9.
Hailstorms are a common meteorological phenomenon in Spain which causes substantial economic damage especially in spring and summer. During 2000 and 2001, a radar-based application for convective monitoring was developed at STAP (Forecasting and Analysis Techniques Department); in order to improve this nowcasting tool, it is needed to include an advanced procedure to estimate the presence of hail as a complementary module in the operational application. A preliminary study, carried out during 2001, showed that the Waldvogel technique, VIL (vertical integrated liquid) density and the hail detection algorithm (HDA) are the methodologies which proved more accurate in our latitudes.Throughout the spring and summer of 2001, all available information about hail events (time, place and hail size) and about storms without hail was used for tuning an experimental module to detect severe and non-severe hailstorms, taking into account the selected algorithms. During 2002, further information about storms was gathered in order to assess the behaviour of the developed hail module. Afterwards, a new module calibration was carried out with the information of the complete storms data set of 2001 and 2002. With this new calibration, the hail module became an operational tool during the spring and summer of 2003. Currently, the verification of the operational module using the data from the storms in 2003 is being elaborated. The aim of this work is to put forward the calibration procedure carried out, the verification results of 2002, and the performance of the hail estimate module in selected cases during 2003 in Spain. 相似文献
10.