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排序方式: 共有198条查询结果,搜索用时 15 毫秒
191.
India is a vast country and is highly diversified in terms of natural resources and socio-economic setup. Moreover, its water resources are unevenly distributed in space and time. With increasing population and increasing aspiration for improved standard of living, there is an acute pressure on the demand and availability of water. Though the idea of interlinking of rivers is not a new concept in India, it had rather persisted long back as much as in other countries of ancient civilization. National Water Development Agency (NWDA) has given the real shape to the proposal of the interlinking of rivers of the country. In India the river-linking project in a sensible and scientific manner will not only allow the prevention of the colossal wastage of a vitally important natural resource, mitigate the flood and inundation by detaining flowing surface water of rainy seasons, but also ensure availability of water to drier areas; combating both flood and drought simultaneously. Moreover, this project will generate 34,000 MW of hydropower and irrigation of an additional 35 million hectares (135,135 square miles) of land. Though linking of rivers may initially appear to be a costly proposition in ecological, geological, hydrological and economical terms, in the long run the net benefits coming from it will far outweigh these costs or losses. However, in the absence of any definite international legal framework, Bangladesh has raised objections against the project. This paper aims at looking at this long-term plan, the project proposal, its involvement and impact not only on the states of India, India as a whole, but also on its neighbouring nations which are linked with India through the waterways, and share the common climatic conditions and economic status.  相似文献   
192.
The Nyiragongo volcano is located in the Virunga volcanic chain (Western Branch Rift, Eastern African Rift System). On January 17-18, 2002 a NS-oriented fracture network quickly propagated down-slope up to 16 km from the crater and two of the several lava flows emitted reached the city of Goma (about 500000 inhabitants). On May 2002 the volcanic activity resumed in the main crater with the formation of an active lava lake, which produced a volcanic plume mainly displaced west towards by the dominant winds. TOMS data suggest a release of SO2 of up to 60000 tons per day with relevant amounts of HF, HC1 and CO2. About 50000 people living in the villages around the western flank of Nyiragongo were forced to use rainwater, having no direct access to drinkable water Furthermore, crops and plants located in the western sector lie below the main direction of the volcanic plume. In order to evaluate the effects on the environment and public health caused by the Nyiragongo degassing system, rain waters, ashes, scorias and Pelee's hairs have been collected in a span of time of more than three years from different sites: (1) Nyiragongo crater;  相似文献   
193.
Recharge to a saline, unconfined shallow-water-table aquifer is normally considered as an irrecoverable loss of water, but such thinking could be reviewed empirically. The use of an appropriate groundwater harvesting system does not only provide an opportunity to recover this lost water, but can also help in catchment salinity management and improvement. Agricultural-based land-drainage systems such as those that use serial biological concentration (SBC) of salts, provide examples of such harvesting methods. The impact of groundwater harvesting has been assessed on the hydro-salinity of a saline catchment in southeastern Australia through modeling. For both the below average rainfall and very wet years, the “do nothing” scenario resulted in increasing salinization in the catchment. However, after introducing a SBC system, groundwater salinity showed a decreasing trend while hydraulic heads tended to stabilize around the depth of subsurface collector wells. However, for a successful groundwater harvesting system, proper understanding of the groundwater flows and salt mobilization associated with a catchment is necessary. The outcomes of this modelling study have the potential to address similar issues (salinization) and/or needs (water harvesting) existing elsewhere in the world, particularly in semi-arid regions.
Muhammad Nadeem AsgharEmail:
  相似文献   
194.
The Chinese caterpillar fungus is famous for its high market value, unusual life history, and significant medicinal uses. It is harvested by very poor communities and sold for an extraordinarily high price. Most of the studies on this species are focused on therapeutic uses, chemical analyses, ecology, and trade. However, harvesting techniques and intensity of the harvests remain undocumented. We document harvesting techniques, trends of harvest, and perceptions of the Chinese caterpillar fungus harvesters in Dolpa, Nepal, based on surveys, focus-group discussions, and direct observations. Along with increasing market value, intensity of the harvest has been increasing. The Chinese caterpillar fungus harvest has now become the second most important livelihood strategy for the local communities, after agriculture. Reported per-capita harvest based on the first day of collection has declined over the last 4 years, apparently because of the decline in the stock and the increasing number of harvesters.  相似文献   
195.
Energy harvesting using piezoelectric materials can be realised by periodic external force. Piezoelectric material directly converts strain energy into electric power to capture a wasted ambient kinetic energy. This recovered energy can be used for operating wireless sensors, such as those found in environmental monitoring, mechanical sensing and structural diagnostic. In our previous work, a flexible piezoelectric device, FPED, was proposed and developed as an energy harvester for generating electric power from flow-induced vibration in ocean and wind environments. In this study a FPED with a painted piezoelectric layer, highly durable in order to withstand extreme bending and weathering caused by waves and currents, is proposed and developed by spray coating for use as an ocean energy harvester. A numerical method is developed to predict electro-fluid–structure interactions and to evaluate electrical performance and mechanical behaviours of the painted FPED. Additionally, validation of the numerical model is provided through several experimental tests. This study also investigates the relationship between the stiffness of the painted FPED and the vibrated frequency, as well as determining their influence on the electrical performance. Finally, the outcomes from a field test, conducted in real ocean space, is presented to provide information on electrical performance, mechanical behaviours and durability of painted FPEDs. The paper shows that a painted FPED is a useful and robust energy harvester for generating electric power from harsh environments.  相似文献   
196.
再论北京西山山地壶穴的形态特征与成因机制   总被引:1,自引:0,他引:1  
嵇少丞  黎乐 《冰川冻土》2018,40(4):715-727
北京西山"京西古道"的"驮兽蹄窝",近些年来因为进山旅游的人越来越多而名声大噪,常见诸报刊、电视、网络等媒体。至于其真正成因,却鲜有学者深究。通过对出现"驮兽蹄窝"的北京西山牛角岭、石佛岭和峰口庵三个垭口详细的野外观察和实地测量,认为基岩路面上那些圆形、椭圆形或多边形凹坑,是历史上无数次暴雨流挟带砂砾冲刷与磨蚀基岩坡面上原先的构造和岩性薄弱部位而逐渐形成的山地壶穴(hillside potholes),属于正常的雨流侵蚀现象(rain-induced erosion)。壶穴的分布特征(在山脊垭口两侧,沿基岩路面上沟槽成串分布)、几何形态的非对称性、内壁的水平擦痕、底部的中央岛现象,以及长、短轴长度、长短轴比(a/b)、宽深比(D/h)和长轴倾向的统计结果与D-h相关性等数据,皆证明"驮兽蹄窝"的成因是不可能的。  相似文献   
197.
孔燕  白晓华 《水文》2019,39(1):60-65
为明确星云湖主要入湖河流向湖体的氮素营养盐输送特征,研究以星云湖南岸4条主要入湖河流单元雨季与旱季不同形态氮素的监测数据为基础,系统研究了星云湖南岸主要入湖河流单元不同形态氮的入湖浓度时空变化及不同形态氮对入湖TN的贡献,并探讨了已建南岸带状调蓄系统入湖污染削减效果。结果表明:①星云湖南岸主要入湖河流单元TN浓度为1.1~18.69 mg/L,DTN浓度为1.88~8.61 mg/L,且农田径流污染导致雨季TN浓度均高于旱季。②南岸大多数入湖河流单元样点中氮素以NO_3-N为主,占TN 39.49%;PN和NH3-N含量相近,分别占TN的28.50%与24.75%;DON含量相对较少,占TN的9.97%。雨季NH3-N、NO_3-N及PN对入湖TN的贡献显著增加。③星云湖南岸四条入湖河流在经过调蓄系统调蓄后,TN浓度均呈现下降趋势,TN平均削减率达到32.35%。不同形态氮素削减效果以NO_3-N最佳,平均削减率达到58.22%;NH_3-N及PN削减效果相对不显著。④星云湖南岸带状调蓄系统应考虑不同形态氮污染季节性差异,并进一步与湖滨湿地串联,提升调蓄系统对NH_3-N与PN的削减效果。  相似文献   
198.
砂田集雨补灌对西瓜产量和土壤水分的影响   总被引:8,自引:7,他引:8  
砂田在干旱半干旱地区是传统保水保墒的耕作方式,至今已有300多年的历史。对传统的砂田配合现代集雨滴灌技术种植西瓜,供试品种是西农8号,试验处理为集雨滴灌砂田(DSF),传统砂田(CSF),不覆砂的传统土田(CEF)。通过甘肃景泰十里砂河村的田间试验表明,产量比传统砂田提高近3倍。产量提高最主要的因素是在西瓜水分受到胁迫的几个关键需水期,及时实施了集雨补灌技术。从田间水分变化分析了集雨补灌砂田的增产机理。  相似文献   
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