全文获取类型
收费全文 | 56篇 |
免费 | 2篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 18篇 |
地球物理 | 13篇 |
地质学 | 9篇 |
天文学 | 8篇 |
出版年
2022年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有58条查询结果,搜索用时 15 毫秒
21.
M. T. A. H. Muella E. R. de Paula P. R. Fagundes J. A. Bittencourt Y. Sahai 《Surveys in Geophysics》2010,31(5):509-530
The possible role, on L-band scintillation activity, played by the nighttime magnetic meridional component of the thermospheric
horizontal neutral winds, the post-sunset F-layer base height, the electrical field pre-reversal enhancement (PRE) and the latitudinal gradients of the F2-layer peak density is analyzed, considering different cases of scintillation occurrence (and their latitudinal extent) during
August and September 2002. The meridional winds were derived over low-latitudes from a modified form of the nonlinear time-dependent
servo-model. A chain of two scintillation monitors and three digital ionosondes was operational in Brazil and used to collect,
respectively, global positioning system signal amplitude scintillation and ionospheric height (h′F; hpF2) and frequency (foF2) parameters. From the overall behavior in the 2 months analyzed, the results suggest that high near sunset upward vertical
plasma drifts are conducive for the generation of spread-F irregularities, whereas large poleward meridional winds tend to suppress the development of plasma bubble irregularities
and the occurrence of their associated scintillations. Even when generated, a reduced fountain effect, due to weak electric
field PRE, acts for the bubbles to be expanded less effectively to higher latitudes. The results also reveal that high F-layer base and peak heights (at equatorial and off-equatorial latitudes), and intense gradients in the F2-peak density between the dip equator and the equatorial anomaly crests, are favorable conditions for the generation of F-region irregularities and increased scintillation activity. Other distinct features of the controlling factors in the cases
of occurrence and non-occurrence of equatorial scintillations are presented and discussed. 相似文献
22.
A 204 m high solid concrete gravity dam is proposed across the River Yamuna in Garhwal Himalaya, India. It will be located on dolerite rocks which have been intruded into the slates of Chandpur Formation. The present study includes the evaluation of the dam foundation by means of drifts, drill holes, water pressure tests and abutment slope stability studies. The water pressure test indicate the necessity of providing a grout curtain below the dam foundation. The analysis of the dam abutments for stability using the Limit equilibrium method indicates that the right abutment slope is kinematically unstable for plane failure mode. The plane failure analysis of the right abutment slope was carried out by modifying the Hoek and Bray (1981, Rock Slope Engineering, 3rd ed., Institute of Mining and Metallurgy, London) technique of plane failure analysis. The analysis reveals that right abutment slope may become unstable during the stripping operation. Based upon the analysis a safe cut slope design for the abutments have been suggested. Subsurface exploration by means of cross drift and drill holes has indicated a sheared contact of slate and dolerite in the foundation area. To avoid the settlement of the dam along this shear zone precautionary measures are suggested. 相似文献
23.
Climate Change: A Case Study Over India 总被引:1,自引:0,他引:1
A. K. Sahai 《Theoretical and Applied Climatology》1998,61(1-2):9-18
Summary A brief account of various causes of climate change in recent decades and climate change trends in the Indian region is presented.
It is of great importance to determine the influence of human activities on the likely climate change during recent decades.
Local temperature is one of the major climatic elements to record the changes in the atmospheric environment caused by industrialization
and urbanization. It is mentioned in the literature that there is either a cooling tendency or cessation of warming after
the late 1950s at most of the Indian industrial cities. A case study of Nagpur, a centrally located city in India, is done
to understand and the possible cause of cooling. Nagpur is the only city in India for which a long-term record of temperature,
for urban (Mayo Hospital) and relatively suburban (Sonegaon Airport) area, is available. The study of the diurnal asymmetry
in maximum and minimum temperatures indicates that the role of suspended particulate matter dominates over that of increasing
greenhouse gases.
Received April 15, 1998 相似文献
24.
The OH (8, 3) band airglow emission has been observed over 1 year at a latitude of 23°S. The average band intensity observed was 385 Rayleighs with a nocturnal range typically less than 100 R. The nocturnal variation in rotational temperature was usually less than 10°K, and the mean temperature was 179°K. The nocturnal variation of intensity is usually uncorrelated with that of the rotational temperature. Time average values of these parameters do, however, show some correlation. On some occasions large post-twilight and pre-dawn intensity enhancements are observed. 相似文献
25.
Joseph Susmitha Sahai A. K. Shabu Hindhiya Chattopadhyay R. Kaur Manpreet 《Theoretical and Applied Climatology》2022,147(1-2):251-264
Theoretical and Applied Climatology - Monsoon intraseasonal oscillations (MISOs) define a significant proportion of intraseasonal variability of the Indian summer monsoon. In the backdrop of... 相似文献
26.
27.
28.
29.
On the recent strengthening of the relationship between ENSO and northeast monsoon rainfall over South Asia 总被引:1,自引:1,他引:1
The southeastern parts of India and Sri Lanka receive substantial rainfall from the northeast monsoon (NEM) during October through December. The interannual variability in NEM rainfall is known to be significantly influenced by the El-Niño/Southern Oscillation (ENSO). Unlike the southwest monsoon (SWM), the NEM rainfall is enhanced during the warm ENSO events, and vice versa. In the context of the recent weakening of the inverse relationship between Southwest Monsoon (SWM) and ENSO, we examine the secular variations in the positive relationship between ENSO and NEM rainfall over South Asia, showing that their relationship has strengthened over the recent years. Based on the analysis of GISST, IMD/CRU precipitation and NCEP/NCAR reanalysis data, we suggest that this secular variation of the relationship is due to epochal changes in the tropospheric circulation associated with ENSO over the region. 相似文献
30.
J. MacDougall M.A. Abdu I. Batista P.R. Fagundes Y. Sahai P.T. Jayachandran 《Journal of Atmospheric and Solar》2009,71(17-18):2013-2016
This paper deals with how atmospheric gravity waves produce the traveling ionospheric disturbances (TIDs) that are observed by ionosondes. It is shown that, rather than directly producing variations of ionospheric height, a likely mechanism involves changes in ionization density by gradients in the horizontal atmospheric gravity wave air motion. These density changes can be observed as variations of the height of an ionospheric isodensity surface (the usual way of measuring TIDs). This mechanism involving enhancement/depletion of ionospheric density requires quite moderate atmospheric gravity wave air motion speeds, and works well at almost all latitudes. 相似文献