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901.
VELOCITY PROFILES OF TURBULENT OPEN CHANNEL FLOWS 总被引:1,自引:0,他引:1
WANG Dianchang WANG Xingkui YU Mingzhong LI Danxun Doctor Prof Dept. of Hydraulic Engineering Tsinghua University Beijing China 《国际泥沙研究》2001,16(1)
1 INTRODUCTIONThe vertical velocity profile of open channel flows is the most basic infOrmation for the stUdy of flowresistance, channel bed stability, river nuvial process and sediment transport. Although it has been asubject of great interest for many years, there does not exist a consensus on some perPlexing questions,such as the position of the theoretical bed level. In order to investigate the properties of velocity profile,data measured in open channel nows from eight sources were … 相似文献
902.
The impact of wastewater flow on the channel bed morphology was evaluated in four ephemeral streams in Israel and the Palestinian Territories: Nahal Og, Nahal Kidron, Nahal Qeult and Nahal Hebron. Channel changes before, during and after the halting of wastewater flow were monitored. The wastewater flow causes a shift from a dry ephemeral channel with intermittent floods to a continuous flow pattern similar to that of humid areas. Within a few months, nutrient‐rich wastewater flow leads to rapid development of vegetation along channel and bars. The colonization of part of the active channel by vegetation increases flow resistance as well as bank and bed stability, and limits sediment availability from bars and other sediment stores along the channels. In some cases the established vegetation covers the entire channel width and halts the transport of bed material along the channel. During low and medium size flood events, bars remain stable and the vegetation intact. Extreme events destroy the vegetation and activate the bars. The wastewater flow results in the development of new small bars, which are usually destroyed by flood flows. Due to the vegetation establishment, the active channel width decreases by up to 700 per cent. The deposition of fine sediment and organic material changed the sediment texture within the stable bar surface and the whole bed surface texture in Nahal Hebron. The recovery of Nahal Og after the halting of the wastewater flow was relatively fast; within two flood seasons the channel almost returned to pre‐wastewater characteristics. The results of the study could be used to indicate what would happen if wastewater flows were introduced along natural desert streams. Also, the results could be used to predict the consequences of vegetation removal as a result of human intervention within the active channel of humid streams. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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906.
流动型态对曼宁糙率系数的影响研究 总被引:7,自引:0,他引:7
根据明渠水流流动型态的概念,通过对实验资料的分析,得到均匀流时糙率系数随水深增加而减小,形成M1型水面线的非均匀流时糙率系数随水深、水力坡度的增大而增大的规律。提出的糙率系数的二步计算法,可以解决因非均匀流水深沿程变化,难以建立糙率系数与水深关系的困难,为在水力计算中修正糙率系数提供了依据。 相似文献
907.
908.
Zeng Pusheng Ph.D. 《地理学报(英文版)》2002,12(3):305-312
Based on field observations, the author proposes a new understanding on the formation of the first bend of the Yangtze River.
The relationship between the formation of the first bend of the Yangtze River and Eocene magmatic activity is expounded, suggesting
that the first bend of the Yangtze River is the result from choking of the strong magmatic activity in Eocene. As a result,
the upstream became a natural reservoir, whose riverside between Mt. Yulong and Mt. Haba was burst, guiding Jinshajiang River
running eastward. At the same time, the drastic uplift of the Qinghai-Tibet Plateau led to the deep dissection of the river
cut down the channel, resulting in the formation of the Tiger Leaping Gorge. The magnitude of uplift in the study area (located
in the eastern of the Tibetan Plateau) is calculated. Taking Mt. Yulong as a base, the magnitude of lift is 3,300 m from Eocene
to Pliocene, adding 700 m since Pleistocene, totaling up to 4,000 m or so. 相似文献
909.
Urban stream channel hazards 总被引:4,自引:0,他引:4
In managing urban stream channels there are pressures to use soft engineering techniques to restore channels wherever possible, to undertake management within a drainage basin context, to produce sustainable solutions and to consider community views. However, specific methods for characterizing the channel network in terms of possible management options have not been developed explicitly for urban areas. A method of characterizing the entire drainage network of urban areas, based upon segmentation of the stream channel network according to the incidence of road crossings and stormwater outfalls, is proposed together with consideration of ways in which the segments can be characterized, including stream channel hazards as a means of providing one basis for urban channel management. 相似文献
910.
W. H. Blake D. E. Walling & Q. He 《Geografiska Annaler: Series A, Physical Geography》2002,84(2):89-102
Recent advances in the use of the environmental radionuclides caesium–137 and unsupported lead–210 to quantify medium– and longer–term rates of erosion and sediment accumulation have proved of considerable value in catchment sediment budget investigations. However, there remains a need to explore the potential for using other shorter–lived radionuclides to provide evidence of sediment mobilisation, transport and storage over shorter timescales and particularly for individual events. This contribution reports the results of a study aimed at exploring the potential for using beryllium–7 (7 Be, t ½ = 53.3 days) to meet this requirement. The study investigated the use of 7 Be as a sediment tracer in three key components of the sediment budget, namely, soil erosion and sediment mobilisation from slopes, the transport, storage and remobilisation of fine sediment in river channels and overbank deposition on river floodplains. The results presented clearly demonstrate the potential for using 7 Be to obtain information on short–term and event–based sediment redistribution rates for use in catchment sediment budget investigations. 相似文献