首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   161篇
  免费   3篇
  国内免费   7篇
测绘学   3篇
大气科学   16篇
地球物理   60篇
地质学   27篇
海洋学   27篇
天文学   27篇
综合类   7篇
自然地理   4篇
  2023年   2篇
  2022年   1篇
  2021年   1篇
  2020年   4篇
  2019年   1篇
  2018年   3篇
  2017年   2篇
  2016年   11篇
  2015年   3篇
  2014年   6篇
  2013年   9篇
  2012年   7篇
  2011年   7篇
  2010年   4篇
  2009年   8篇
  2008年   9篇
  2007年   6篇
  2006年   4篇
  2005年   7篇
  2004年   2篇
  2003年   4篇
  2002年   4篇
  2001年   4篇
  2000年   6篇
  1999年   4篇
  1998年   3篇
  1997年   1篇
  1996年   5篇
  1995年   3篇
  1994年   1篇
  1993年   1篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1987年   4篇
  1986年   1篇
  1985年   4篇
  1984年   1篇
  1983年   1篇
  1982年   4篇
  1981年   1篇
  1980年   2篇
  1978年   2篇
  1977年   1篇
  1976年   3篇
  1975年   3篇
  1974年   1篇
  1973年   2篇
  1971年   2篇
  1965年   1篇
排序方式: 共有171条查询结果,搜索用时 109 毫秒
111.
112.
Numerical models are systematically presented for time-dependent thermal convection of Newtonian fluid with strongly temperature-dependent viscosity in a two-dimensional rectangular box of aspect ratio 3 at various values of the Rayleigh number Rab defined with viscosity at the bottom boundary up to 1.6×108 and the viscosity contrast across the box rη up to 108. We found that there are two different series of bifurcations that take place as rη increases. One series of bifurcations causes changes in the behavior of the thermal boundary layer along the surface boundary from small-viscosity-contrast (SVC) mode, through transitional (TR) mode, to stagnant-lid (ST) mode, or from SVC mode directly to ST mode, depending on Rab. Another series of bifurcations causes changes in the aspect ratio of convection cells; convection with an elongated cell can take place at moderate rη (103–105.5 at Rab=6×106), while only convection of aspect ratio close to 1 takes place at small rη and large rη. The parameter range of rη and Rab for elongated-cell convection overlaps the parameter range for SVC and ST modes and include the entire parameter range for TR mode. In the elongated-ST regime, the lid of highly viscous fluid along the top boundary is not literally ‘stagnant’ but can horizontally move at a velocity high enough to induce a convection cell with aspect ratio much larger than 1.  相似文献   
113.
A Note has been published for this article in Hydrological Processes 18(4) 2004, 825. Both water and heat balances were studied in a conifer plantation watershed in south‐west Japan, within the warm‐temperate East Asia monsoon area. Forest cover in the watershed consists mainly of Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) plantations. Precipitation and runoff have been observed since 1991, so evapotranspiration can be compared with the water balance. Two meteorological observation towers were built to monitor evapotranspiration in the watershed. The annual average precipitation, amount of runoff and losses were 2166, 1243 and 923 mm, respectively. The evapotranspiration (latent heat flux) agreed well with the water balance losses. The average annual evapotranspiration at the tower built in the centre of the watershed was 902 mm; evapotranspiration at the other tower, further upslope, was 875 mm. The observed evapotranspiration was 39% to 40% of the average precipitation (2166 mm). The mean net radiation was c. 2·6 GJ m?2 year?1, and is considered a representative value of the net radiation (Rn) in coniferous plantations in this region. This region is classified in the humid zone based on the ratio of net radiation (Rn) to the energy required to evaporate the rainfall (λR). The mean annual evaporation of canopy‐intercepted water was 356 mm or about 15% of the average precipitation. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
114.
Remote sensing was used to understand the seasonal and spatial variation of suspended sediment in the Ganges and Brahmaputra Rivers in Bangladesh for two different discharge periods. Suspended sediment concentration (SSC) in these rivers was estimated from the reflectance of Landsat TM band 3. During the high discharge period, SSC in the Ganges is higher than that in the Brahmaputra. But in the low discharge period, this is reversed. Both erosional and depositional processes are active on their flood plains. Significant fluctuations in SSC and in suspended sediment load were observed along their courses because of river bank erosion and deposition and/or scouring and aggradation of river beds. Owing to scouring and turbulence, SSC increases markedly at the confluence of these rivers. Reflectance of AVHRR band 1 data was also analysed to study the distribution of suspended sediment along other reaches of these rivers. Like SSC, reflectance at the confluence zone increases compared with that in the Brahmaputra. However, this increase is not marked compared with the Ganges. The influence of their tributaries on the suspended sediment load could be inferred from the pattern of reflectance. Remote sensing data used in this study was corrected for atmospheric effects. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
115.
A sudden acceleration of the Kuroshio jet appears off Cape Shionomisaki in the high-resolution (horizontal resolution of 1/36°) JCOPE 2 ocean reanalysis data. Using this dataset, we investigated the structure of the Kuroshio acceleration. The increase in the velocity of the current is accompanied by a downstream flow separation from the coast and an outcrop of cold temperature inshore. The acceleration of Kuroshio appears when it takes a near-shore path. Cape Shionomisaki amplifies the responses to the Kuroshio flow by creating the zonal velocity acceleration toward the downstream region when the Kuroshio flows closer to the coast. The Kuroshio acceleration coincided with the topographic ridge on the continental shelf near Cape Shionomisaki. This relation suggests that the dynamics of the acceleration is linked to the topographic feature. We proposed an explanation of the Kuroshio acceleration using a hydraulic control theory. An analytical solution was applied to the coastal topography around the Kii Peninsula. The solution captured some aspects of the Kuroshio acceleration.  相似文献   
116.
The northern Nagano Prefecture earthquake, MJMA?6.7 (Mw?6.2), which is inferred to have been triggered by the huge (Mw?9.0) March 11, 2011 Tohoku earthquake, occurred on March 12, 2011, in northern Nagano Prefecture, an area in Japan famous for heavy snowfall. A large number of landslides were triggered by the 12 March earthquake, and it caused building damage in the area of the epicenter. To clarify characteristics of the distribution and dynamic behavior of these landslides, we analyzed aerial photographs and conducted field surveys in and around the epicentral area. Large-scale landslides with long distance run-outs are a remarkable characteristic of the landslides induced by this earthquake. The long travel distance is considered to be related to the thick snowpack at the time the earthquake occurred. Moderate scale deep-seated landslides and shallow landslides were also observed in the study area. Based on an analysis of landslides with the active fault on which the earthquake is believed to have occurred, most of these landslides were distributed on the hanging wall of the active fault, within a distance of 12?km from the fault.  相似文献   
117.
The nitric oxide density profile between the altitudes 72 and 120 km was obtained by means of the airglow γ(1, 0) band measured with a rocket-borne radiometer flown at Syowa Station (69°S, 40°E). The NO density was found to have two peaks with a value of 1.5× 108cm?3 at 90 and 110 km, and is much larger than those in the middle and low latitudes. Because of a long lifetime of NO in the mesosphere, the observed NO enhancement may be due to the after-effect of the particle precipitation event which occurred within the half day before, despite no polar disturbance during the rocket flight.  相似文献   
118.
119.
T. Ogawa 《Annales Geophysicae》1997,14(12):1454-1461
We briefly overview the radar observations that have been made for 30 years at Syowa Station, Antarctica for studying small-scale electron-density irregularities in the southern high-latitude E- and F-region ionosphere. Some observational results (i.e., long-term variations of radio aurora, Doppler spectra with narrow spectral widths and low Doppler velocities, and simultaneous observations of radar and optical auroras) from VHP radars capable of detecting 1.3- to 3-m scale irregularities are presented. A new 50-MHz radar system equipped with phased-antenna arrays began operation in February 1995 to observe two-dimensional behaviors of E-region irregularities. An HF radar experiment also began in February 1995 to explore decameter-scale E- and F-region irregularities in the auroral zone and polar cap. These two radars will contribute to a better understanding of the ionospheric irregularities and ionospheric physics at southern high latitudes.  相似文献   
120.
Arsenic release experiments using natural indigenous microbial assemblages and natural sediment samples in Bangladesh have been performed. The As release appears to be facilitated by moderate organic input. Addition of some nutrients caused reducing conditions, which may generate the appropriate environment for Fe-reducing bacteria to become active. Detailed cellular phospholipid fatty acid (PLFA) analysis suggests the presence of SO4-reducing and Fe-reducing bacteria in the sediments. These Fe-reducing bacteria may serve as the agents catalyzing As release in the organic-rich sediments. 16S rDNA analysis of one cultured sample suggests the presence of clostridia, some of which are known to mediate Fe reduction. Based on new PLFA analyses, it is proposed that combined microbial processes of SO4 reduction to generate anaerobic conditions and Fe reduction to co-reduce As are important biogeochemical factors for As release in the Bangladesh sediments.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号