全文获取类型
收费全文 | 404篇 |
免费 | 7篇 |
专业分类
测绘学 | 46篇 |
大气科学 | 33篇 |
地球物理 | 55篇 |
地质学 | 112篇 |
海洋学 | 26篇 |
天文学 | 124篇 |
综合类 | 1篇 |
自然地理 | 14篇 |
出版年
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 18篇 |
2017年 | 12篇 |
2016年 | 21篇 |
2015年 | 12篇 |
2014年 | 16篇 |
2013年 | 27篇 |
2012年 | 23篇 |
2011年 | 24篇 |
2010年 | 12篇 |
2009年 | 16篇 |
2008年 | 20篇 |
2007年 | 16篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 12篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有411条查询结果,搜索用时 15 毫秒
381.
The current study focuses on the response analysis of triangular tension leg platform (TLP) for different wave approach angles varying from 0° through 90° and its influence on the coupled dynamic response of triangular TLPs. Hydrodynamic loading is modeled using Stokes fifth-order nonlinear wave theory along with various other nonlinearities arising caused by change in tether tension and change in buoyancy caused by set down effect. Low frequency surge oscillations and high frequency tension oscillations of tethers are ignored in the analysis. Results show that wave approach angle influences the coupled dynamic response of triangular TLP in all degrees of freedom except heave. Response in roll and sway degrees of freedom are activated which otherwise are not present in TLP's response to unidirectional waves. Pitch and roll responses are highly stochastic in nature indicating high degree of randomness. Variation in surge, sway and heave responses are nonlinear and are not proportional to change in wave height for the same period. 相似文献
382.
A few prediction methods have been developed using the precursor techniques and are found to be successful. On the basis of geomagnetic activity aa indices during the descending phase of the preceding cycle, we have established an expression which predicts the maximum annual mean sunspot number in cycle 23 to be 166.2. This indicates that cycle 23 would be a highly active and historic cycle. The average geomagnetic activity aa index during the ascending phase of cycle 23 would be about 24.9, comparable to 22.2 and 24.8 in cycles 21 and 22, respectively. This further indicates that during the ascending phase of cycle 23 energetic two-ribbon flares will be produced so as to give rise to strong proton events. 相似文献
383.
R R Navalgund V Jayaraman A S Kiran Kumar Tara Sharma Kurien Mathews K K Mohanty V K Dadhwal M B Potdar T P Singh R Ghosh V Tamilarasan T T Medhavy 《Journal of the Indian Society of Remote Sensing》1996,24(4):207-237
Although data available from various earth observation systems have been routinely used in many resource applications, however there have been gaps, and data needs of applications at different levels of details have not been met. There is a growing demand for availability of data at higher repetivity, at higher spatial resolution, in more and narrower spectral bands etc. Some of the thrust areas of applications particularly in the Indian context are;
- Management of natural resources to ensure sustainable increase in agricultural production,
- Study the state of the environment, its monitoring and assessment of the impact of. various development actions on the environment,
- Updating and generation of large scale topographical maps.
- Exploration/exploitation of marine and mineral resources and
- Operational meteorology and studying various land and oceanic processes to understand/predict global climate changes.
- Moderate spatial resolution (l50-300m), high repetivity (2 Days), minimum set of spectral bands (VIS, NIR, MIR. TIR) full coverage.
- Moderate to high spatial resolution (20-40m), high repetivity (4-6 Days), spectral bands (VIS, MR, MIR, TIR) full coverage.
- High spatial resolution (5-10m) muitispectral data with provision for selecting specific narrow bands (VIS, N1R. MIR), viewing from different angles.
- Synthetic aperture radar operating in at least two frequencies (C, X, Ku), two incidence angles/polarizations, moderate to high spatial resolution (20-40m), high repetivity (4-6 Days).
- Very high spatial resolution (1-2m) data in panchromatic band to provide terrain details at cadastral level (1:10,000).
- Stereo capability (1-2m height resolution) to help planning/execution of development plans.
- Moderate resolution sensor operating in VIS, NIR, MIR on a geostationary platform for observations at different sun angles necessary for the development of canopy reflectance inversion models.
- Diurnal (at least two i.e. pre-dawn and noon) temperature measurements of the earth surface.
- Ocean colour monitor with daily coverage.
- Multi-frequency microwave radiometer, scatterometer. altimeter, atmospheric sounder, etc.
384.
Geomorphic characterization and diversity of the fluvial systems of the Gangetic Plains 总被引:2,自引:0,他引:2
The extensive Gangetic alluvial plains are drained by rivers which differ strongly in terms of hydrological and sediment transport characteristics. These differences are manifested in the geomorphic diversity of the plains. The Western Gangetic Plains (WGP) are marked by a degradational topography with incised channels and extensive badland development in some parts, while the Eastern Gangetic Plains (EGP) are characterized by shallow, aggrading channels with frequent avulsions and extensive flooding. We interpret such geomorphic diversity in terms of differences in stream power and sediment supply from the catchment areas. The rivers draining the western plains are marked by higher stream power and lower sediment yield that result in degradation. In comparison, the rivers draining the eastern Gangetic Plains have lower stream power and higher sediment yield that result in aggradation. The variation of stream power, a function of channel slope and high sediment yield, is attributed to differences in rainfall and rate of uplift in the hinterland. It is suggested that such differences have resulted in a marked geomorphic diversity across the plains. It is also suggested that such diversity has existed for a fairly long time because of climatic and tectonic variance. 相似文献
385.
K. V. S. Badarinath K. Madhavi Latha T. R. Kiran Chand 《Journal of the Indian Society of Remote Sensing》2004,32(4):317-322
Forests over Indian region are fire prone during summer season and effective means for monitoring such events is important. Satellite data with its repetitive and wide area coverage provides data sets required for monitoring such events. The advances in sensor technology and multi-satellite systems have improved capability for monitoring such events. The present study addresses forest fires monitoring using night time data sets of ENVISAT-AATSR data over Indian Region. The results of the study indicated that region specific algorithms are required for forest fire detection as soils in tropical regions have higher temperatures during night time. 相似文献
386.
We report here the first direct evidence for detection of H intensity oscillations in two extended flares of 15 November 1989 and 20 April 1991. The relative intensity variations measured with time at 18 different flare and chromospheric locations were analysed to obtain the oscillation modes. The analysis shows prominent 5- and 3-min modes in flares in addition to their existence in the chromosphere. However, there exists a frequency difference between the flare and chromospheric modes. This frequency deviation of about 300 µHz is proposed as an influence of higher magnetic field, location of the measurements (height) in chromosphere, and high temperature in the flare. 相似文献
387.
388.
In the present study, growth and water relation parameters were analysed in drought-stressed Coriaria nepalensis Wall. seedlings. C. nepalensis seedlings were subjected to four drought cycles of 7, 14, 21, and 28-days, and to one control level (watered on alternate days) in a glasshouse. The seedlings failed to survive a 28-days drought during summer. Osmotic adjustment (defined as the decrease in osmotic potential at zero or full turgor in response to water deficit) was measured as the difference between the osmotic potential of seedlings watered on alternate days (control) and those subjected to 21-days drought cycle. Seedlings subjected to 21-days drought had a predawn water potential of −2.60 MPa, and showed an osmotic adjustment of −1.95 MPa at full turgor and −2.17 MPa at zero turgor. The growth of seedlings was positively related to moisture and with water potential. With decline in soil moisture the root:shoot ratio increased while leaf weight ratio decreased. Leaf characteristics, such as leaf number, leaf area, leaf area ratio, specific leaf area and leaf drop, were also affected by moisture stress. This study has indicated that osmotic adjustment is a major adaptive mechanism of C. nepalensis that aids successful regeneration of seedlings in degraded sites with inhospitable soil conditions. 相似文献
389.
In this paper, the results of a series of extensive measurements of multifrequency radio wave absorption in theD-region of the ionosphere during the epoch of the minium period of the solar cycle are presented. Experimental results for Udaipur, a low latitude station (24°35′N) are compared with the theoretically expected results. It is found that the experimental values of frequency indexm and cos χ indexn agree well with those obtained theoretically. The mean values ofm andn for the whole period of observation are found to be 1·76 and 1·4 respectively. The seasonal variation of the values ofm andn is also discussed. 相似文献
390.
Malkiat Singh H S Gurm M R Deshpande R G Rastogi G Sethia A R Jain A V Janve R K Rai V M Patwari B S Subbarao 《Journal of Earth System Science》1978,87(3):47-55
Radio beacon from ATS-6 at 140 MHz was used to measure the changes in the polarization angle (Faraday rotation) at Bombay,
Rajkot, Ahmedabad, Udaipur and Patiala during October 1975 to July 1976. In this paper, results of diurnal, seasonal and latitudinal
variations in total electron content (TEC) derived from these measurements are reported. The amplitude of diurnal peak is
found to be higher at Rajkot, Ahmedabad and Udaipur as compared to that at Patiala or Bombay, indicating that the peak of
Appleton anomaly in the latitudinal variation of TEC was close to the latitude of Ahmedabad. The diurnal maximum of TEC occurs
around the same time during summer and winter months. The peak electron content shows a semiannual variation at all the stations
with large values in equinoxes as compared to winter and summer. The TEC at Bombay shows a seasonal anamoly with high values
in winter as compared to summer. The paper describes the development of latitudinal anomaly with the time of the day for different
seasons. This anomaly is maximum during 1000 to 1800 LT and is located between 12° and 14° N (dip latitude) in summer and
equinoxes and at about 10°N in winter. 相似文献