全文获取类型
收费全文 | 80篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 10篇 |
地球物理 | 17篇 |
地质学 | 30篇 |
海洋学 | 3篇 |
天文学 | 1篇 |
综合类 | 9篇 |
自然地理 | 11篇 |
出版年
2024年 | 1篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2015年 | 2篇 |
2014年 | 9篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有85条查询结果,搜索用时 15 毫秒
41.
Santosh Kumar Rana Hum Kala Rana Suresh Kumar Ghimire Krishna Kumar Shrestha Sailesh Ranjitkar 《山地科学学报》2017,14(3):558-570
Predicting the potential distribution of medicinal plants in response to climate change is essential for their conservation and management. Contributing to the management program, this study aimed to predict the distribution of two threatened medicinal plants, Fritillaria cirrhosa and Lilium nepalense. The location of focal species gathered from herbarium specimen housed in different herbaria and online databases were geo-referenced and checked for spatial autocorrelation. The predictive environmental variables were selected, and MaxEnt software was used to model the current and future distributions of focal species. Four Representative Concentration Pathway (RCP) trajectories of the BCC-CSM1.1 model were used as the future (2050) projection layer. The MaxEnt modelling delineated the potential distribution of F. cirrhosa and L. nepalense. The current suitability is projected towards Central and Eastern Hilly/Mountainous regions. Both species gain maximum suitability in RCP 4.5 which decline towards other trajectories for L. nepalense. Overall, both the focal species shift towards the north-west, losing their potential habitat in hilly and lower mountainous regions by 2050 across all trajectories. Our results highlight the impact of future climate change on two threatened and valuable species. The results can be further useful to initiate farming of these medicinally and economically important species based on climatically suitable zone and for designing a germplasm conservation strategy. 相似文献
42.
The alpine treeline ecotone is an important component of mountain ecosystems of the Nepal Himalaya; it plays a vital role in the livelihood of indigenous people, and provides ecosystem services. However, the region faces a problem of paucity of data on treeline characteristics at the regional and landscape scales. Therefore, we used Remote Sensing (RS), and Geographic Information Science (GIS) approaches to investigate cross-scale interactions in the treeline ecotone. Additionally, European Space Agency land cover map, International Center for Integrated Mountain Development (ICIMOD) land cover map, ecological map of Nepal, and United States Geological Survey Shuttle Radar Topography Mission-Digital Elevation Model were used to analyze treeline pattern at the regional scale. Digital Globe high-resolution satellite imagery of Barun (eastern Nepal) and Manang (central Nepal) were used to study treeline patterns at the landscape scale. Treeline elevation ranges from 3300-4300 m above sea level. Abies spectabilis, Betula utilis, and Pinus wallichiana are the main treeline-forming species in the Nepal Himalaya. There is an east to west treeline elevation gradient at the regional scale. No slope exposure is observed at the regional scale; however, at the landscape scale, slope exposure is present only in a disturbed area (Manang). Topography and human disturbance are the main treeline controlling factor in Barun and Manang respectively. 相似文献
43.
Gaurav Shrestha Youhei Uchida Satoru Kuronuma Mutsumi Yamaya Masahiko Katsuragi Shohei Kaneko Naoaki Shibasaki Mayumi Yoshioka 《Hydrogeology Journal》2017,25(5):1437-1450
Development of a ground-source heat pump (GSHP) system with higher efficiency, and evaluation of its operating performance, is essential to expand the growth of GSHP systems in Japan. A closed-loop GSHP system was constructed utilizing a flowing (artesian) well as a ground heat exchanger (GHE). The system was demonstrated for space-heating and space-cooling of a room (area 126.7 m2) in an office building. The average coefficient of performance was found to be 4.5 for space-heating and 8.1 for space-cooling. The maximum heat exchange rate was 70.8 W/m for space-heating and 57.6 W/m for space-cooling. From these results, it was determined that a GSHP system with a flowing well as a GHE can result in higher performance. With this kind of highly efficient system, energy saving and cost reduction can be expected. In order to assess appropriate locations for the installation of similar kinds of GSHP systems in Aizu Basin, a suitability map showing the distribution of groundwater up-flowing areas was prepared based on the results of a regional-scale three-dimensional analytical model. Groundwater up-flowing areas are considered to be suitable because the flowing well can be constructed at these areas. Performance evaluation of the GSHP system utilizing the flowing well, in conjunction with the prepared suitability map for its installation, can assist in the promotion of GSHP systems in Japan. 相似文献
44.
Kyle P.Larson Asghar Ali Sudip Shrestha Mathieu Soret John M.Cottle Rafique Ahmad 《地学前缘(英文版)》2019,10(3):849-861
New metamorphic petrology and geochronology from the Loe Sar dome in the Swat region of northern Pakistan place refined constraints on the pressure, temperature and timing of metamorphism and deformation in that part of the Himalayan orogen. Thermodynamic modelling and monazite petrochronology indicate that metamorphism in the area followed a prograde evolution from ~525 ± 25 ℃and 6 士 0.5 kbar to ~610 ± 25 ℃ and 9 士 0.5 kbar, between ca. 39 Ma and 28 Ma. Partitioning of heavy rare earth elements between garnet rims and 30-28 Ma monazite are interpreted to indicate coeval crystallization at peak conditions. Microtextural relationships indicate that garnet rim growth post-dated the development of the main foliation in the area. The regional foliation is folded about large-scale N-S trending fold axes and overprinting E-W trending folds to form km-scale domal culminations. The textural relationships observed indicate that final dome development must be younger than the 30-28 Ma monazite that grew with garnet rims post-regional foliation development, but pre-doming-related deformation. This new timing constraint helps resolve discrepancy between previous interpretations,which have alternately suggested that N-S trending regional folds must be either pre-or post-early Oligocene. Finally, when combined with existing hornblende and white mica cooling ages, these new data indicate that the study area was exhumed rapidly following peak metamorphism. 相似文献
45.
This study reveals some disturbing facts about the status of minorities in geography in the United States. The three underrepresented minority groups comprise only about 3% of the total geography population in the sample. This does not reflect well on geography, a discipline whose cultural and regional roots are as diverse as its subjects of study. It is important to increase minority participation in geography in order to diversify the discipline as well as allow minority students to enhance their spatial skills such as an understanding of the earth, cultural patterns, and political issues at the local, national, and global levels. If the discipline continues to neglect the need to provide a quality geographic education to minority students, it will forsake not only one of its major missions of spreading global knowledge to all, but will lose its market share of the growing minority student population. This paper describes the extent of minority underrepresentation in geography and provides a set of general recommendations, including a call for a national conference and formation of a high-level committee to deal with the issue of increased minority participation in geography. 相似文献
46.
47.
Hussaini Mohammad Salem Farahmand Asadullah Shrestha Sangam Neupane Sanjiv Abrunhosa Manuel 《Hydrogeology Journal》2022,30(1):59-78
Hydrogeology Journal - While the success and sustainability of managed aquifer recharge (MAR) strongly depends on many characteristics of the site, it is necessary to integrate the site... 相似文献
48.
Journal of Geographical Sciences - Land use in the northeast region of Thailand has changed dramatically in the past two decades. These changes are mainly due to the government policies, which... 相似文献
49.
R. M. Bhagat Sharda Singh C. Sood R. S. Rana V. Kalia S. Pradhan W. Immerzeel B. Shrestha 《Journal of the Indian Society of Remote Sensing》2009,37(2):233-240
Land suitability analysis is prerequisite for sustainable agriculture and it plays a pivotal role in the niche based agricultural
planning in mountain regions. In this paper different parameters viz. climatic (precipitation and temperature), topographic
(elevation), soil type and land cover/land use have been used in order to perform land suitability evaluation for cereals
food-grain crops in Himachal Pradesh using Geographic Information System (GIS). The suitability analysis was performed by
digital processing of geo-referenced data (elevation, climate, soil and landcover) and calculating potential production areas
by combining different types of geographical data through decision rules framed for each crop in ArcView spatial analyst.
Suitable areas have been delineated for cereal crops in the form of land suitability maps. In comparison to the actual area
under cereal crops, the possibility of further expansion under each cereal crop was determined. These discriminated areas
appear suitable for growing these crops and can be harnessed efficiently for achieving long term sustainability and food security. 相似文献
50.
A hydrologic regression sediment-yield model was established to determine the relationship between water discharge and suspended sediment discharge at the Blue Nile and the Atbara River outlet stations during the flood season. The model consisted of two main submodels: (1) a suspended sediment discharge model, which was used to determine suspended sediment discharge for each basin outlet; and (2) a sediment rating model, which related water discharge and suspended sediment discharge for each outlet station. Due to the absence of suspended sediment concentration measurements at or near the outlet stations, a minimum norm solution, which is based on the minimization of the unknowns rather than the residuals, was used to determine the suspended sediment discharges at the stations. In addition, the sediment rating submodel was regressed by using an observation equations procedure. Verification analyses on the model were carried out and the mean percentage errors were found to be +12.59 and –12.39, respectively, for the Blue Nile and Atbara. The hydrologic regression model was found to be most sensitive to the relative weight matrix, moderately sensitive to the mean water discharge ratio, and slightly sensitive to the concentration variation along the River Nile's course. 相似文献