全文获取类型
收费全文 | 1312篇 |
免费 | 32篇 |
国内免费 | 14篇 |
专业分类
测绘学 | 100篇 |
大气科学 | 65篇 |
地球物理 | 311篇 |
地质学 | 444篇 |
海洋学 | 58篇 |
天文学 | 310篇 |
综合类 | 16篇 |
自然地理 | 54篇 |
出版年
2022年 | 11篇 |
2021年 | 17篇 |
2020年 | 19篇 |
2019年 | 27篇 |
2018年 | 64篇 |
2017年 | 49篇 |
2016年 | 67篇 |
2015年 | 42篇 |
2014年 | 51篇 |
2013年 | 82篇 |
2012年 | 44篇 |
2011年 | 43篇 |
2010年 | 44篇 |
2009年 | 56篇 |
2008年 | 57篇 |
2007年 | 46篇 |
2006年 | 36篇 |
2005年 | 34篇 |
2004年 | 19篇 |
2003年 | 25篇 |
2002年 | 21篇 |
2001年 | 22篇 |
2000年 | 23篇 |
1999年 | 25篇 |
1998年 | 27篇 |
1997年 | 15篇 |
1996年 | 15篇 |
1995年 | 22篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 25篇 |
1990年 | 12篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 26篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1973年 | 12篇 |
1972年 | 12篇 |
1971年 | 13篇 |
排序方式: 共有1358条查询结果,搜索用时 15 毫秒
91.
S.B. Rakesh Kumar Singh Mohan L. Gupta G.V. Rao 《Journal of Volcanology and Geothermal Research》1982,13(3-4)
Direct current resistivity surveys and shallow temperature measurements were carried out for geothermal exploration in a part of Parvati valley, goethermal field, Himachal Pradesh, India. At a few places, the Schlumberger soundings pointed to the presence of a relatively low-resistivity shallow layer, which probably represents fractured and jointed quartzite, saturated with hot/cold water. Wenner resistivity profiles indicate the presence of some possible shallow subsurface lateral hot water channels across the valley at Manikaran. Shallow temperature measurements show a good subsurface thermal anomaly near the confluence of the rivers Brahmaganga and Parvati. The results of the survey, together with other available geodata, suggest that an anomalous heat source does not lie beneath the study area.It is postulated that the meteoric water, originating at high elevations after heating as a result of circulation at depth, emerges at the surface in the Parvati valley as hot springs, after mixing in various proportions with near surface cold waters. 相似文献
92.
Gupta H.K. and Singh V.P., 1982. Is Shillong region, northeast India, undergoing a dilatancy stage precursory to a large earthquake? In: A.L. Hales and Z. Suzuki (Editors), Earthquake Prediction. Tectonophysics, 85: 31–33. 相似文献
93.
B. M. Singh M. L. Manchanda H. S. Iyer L. M. Pande Jitendra Prasad B. R. M. Rao 《Journal of the Indian Society of Remote Sensing》1983,11(3):1-13
A critical appraisal of the need and use of remote sensing techniques for land use mapping with particular reference to Indian conditions have been made. Land use classification system based on physiography, utility, management and identification have been suggested using remote sensing techniques at different levels of mapping. 相似文献
94.
M. L. Manchanda H. S. Iyer B. M. Singh Jitendra Prasad 《Journal of the Indian Society of Remote Sensing》1983,11(3):67-74
The use of Landsat imagery at 1:1 M and 1:250,000 and aerial photos on 1:65,000 and 1:20,000 scale have been used to study landuse. It has been possible to achieve identification using Landsat imagery up to utility level ( level 1 and II ) and with the aerial photographs further subdivisions of utility into management and identification (level III and IV) . 相似文献
95.
Shahriar M. Wahid Mukand S. Babel Ashim Das Gupta Roberto S. Clemente 《Hydrogeology Journal》2007,15(2):365-382
In Bangladesh, development of the groundwater resource for irrigation is a vital component of the government’s agricultural
strategy to attain food self-sufficiency. Amidst reports of falling groundwater levels in many parts of Bangladesh, the potential
of groundwater use has been investigated in the Teesta Barrage Project (TBP) in which large-scale groundwater development
for dry-season irrigation has taken place in the recent past. Several techniques and tools have been applied such as the combination
of analysis of groundwater hydrographs and mathematical modelling to derive key hydrogeological variables, calculation of
net irrigation requirement and the use of geographical information systems. The results show that the economically attractive
high-yielding variety (HYV) Boro (dry season) rice cultivation during the groundwater irrigation season may not be sustained in large parts of the project
area if the current trends in abstraction are continued. However, due to spatial variation in abstraction, nine thanas (sub-districts)—out of a total of 21 in the project area—may still be able to expand groundwater-irrigated cropland and a
groundwater-use potential of 40 mm/year may be created if deep-set shallow tubewells are used by the farmers to abstract groundwater.
A structured approach, based on zoning of potential areas, is recommended for groundwater development and use.
Resumen En Bangladesh, el desarrollo de las aguas subterráneas para riego es un componente vital del la estrategia agrícola del Gobierno para obtener la auto-suficiencia alimentaria. Un informe intermedio evidencia un descenso de los niveles de aguas subterráneas en muchas partes de Bangladesh, el uso potencial de aguas subterránea ha sido investigado en el Proyecto Tessta Barrage (TBP) en el cual ha tenido lugar el desarrollo de las aguas subterráneas a gran escala para el riego en la estación seca en un pasado reciente. Se ha aplicado algunas técnicas y herramientas, como la combinación del análisis de datos gráficos de aguas subterráneas y modelización matemática para obtener variables hidrogeológicas clave, el cálculo de la necesidad neta de riego y el uso de Sistemas de Información Geográfica. El resultado muestra que el cultivo, económicamente atractivo, de arroz HYV Boro (estación seca) durante la estación de riego con aguas subterráneas puede no ser sostenible en gran parte del área del proyecto si continúan las tendencias actuales en las extracciones. Sin embargo, debido a la variación espacial en la extracción, nueve thanas (subdistritos)—de un total de 21 en el área del Proyecto—pueden todavía sufrir un aumento de la tierra cultivable regada con aguas subterráneas y que se puede asumir un uso potencial de agua subterránea de 40 mm/estación si los granjeros utilizan sondeos someros instalados en fosas para la extracción. Se recomienda una aproximación estructurada para el desarrollo y uso de las aguas subterráneas, basada en la zonificación de áreas potenciales.
Résumé Au Bangladesh, l’exploitation des ressources en eau souterraines pour l’irrigation est une composante vitale de la stratégie agricole gouvernementale pour atteindre l’auto-suffisance alimentaire. Parmi les baisses de niveaux piézométriques rapportées sur de nombreuses régions du Bangladesh, le potentiel d’utilisation des eaux souterraines a été étudié sur le Projet de Barrage de Teesta (TBP), où, dans un passé récent, les eaux souterraines ont été massivement exploitées pour l’irrigation en saison sèche. De nombreux outils et techniques ont été utilisés, comme l’analyse combinée des chroniques piézométriques et des modèles mathématiques pour dégager les variables hydrogéologiques clés, le calcul des besoins nets pour l’irrigation, et l’utilisation des systèmes d’information géographique. Les résultats démontrent que la culture en saison d’irrigation de la variété de riz HYV Boro (saison sèche), économiquement attrayante, n’est potentiellement pas viable sur de nombreux secteurs de la zone étudiée si les prélèvements perdurent selon la tendance actuelle. Cependant, du fait de la variation spatiale des prélèvements, neuf thanas (sous-districts)—sur un total de 21 sur le secteur d’étude—pourraient encore augmenter les surfaces irriguées, et une disponibilité en eau de 40 mm/saison pourrait être générée si les agriculteurs utilisaient des puits peu profonds pour exploiter les ressources souterraines. Une approche structurée, basée sur le zonage des secteurs potentiels, est recommandée pour l’exploitation et l’utilisation des eaux souterraines.相似文献
96.
Numerical Simulation of Andhra Severe Cyclone (2003): Model Sensitivity to the Boundary Layer and Convection Parameterization 总被引:1,自引:0,他引:1
C. V. Srinivas R. Venkatesan D. V. Bhaskar Rao D. Hari Prasad 《Pure and Applied Geophysics》2007,164(8-9):1465-1487
The Andhra severe cyclonic storm (2003) is simulated to study its evolution, structure, intensity and movement using the Penn
State/NCAR non-hydrostatic mesoscale atmospheric model MM5. The model is used with three interactive nested domains at 81,
27 and 9 km resolutions covering the Bay of Bengal and adjoining Indian Peninsula. The performance of the Planetary Boundary
Layer (PBL) and convective parameterization on the simulated features of the cyclone is studied by conducting sensitivity
experiments. Results indicate that while the boundary layer processes play a significant role in determining both the intensity
and movement, the convective processes especially control the movement of the model storm. The Mellor-Yamada scheme is found
to yield the most intensive cyclone. While the combination of Mellor-Yamada (MY) PBL and Kain-Fritsch 2 (KF2) convection schemes
gives the most intensive storm, the MRF PBL with KF2 convection scheme produces the best simulation in terms of intensity
and track. Results of the simulation with the combination of MRF scheme for PBL and KF2 for convection show the evolution
and major features of a mature tropical storm. The model has very nearly simulated the intensity of the storm though slightly
overpredicted. Simulated core vertical temperature structure, winds at different heights, vertical winds in and around the
core, vorticity and divergence fields at the lower and upper levels—all support the characteristics of a mature storm. The
model storm has moved towards the west of the observed track during the development phase although the location of the storm
in the initial and final phases agreed with the observations. The simulated rainfall distribution associated with the storm
agreed reasonably with observations. 相似文献
97.
S. Abhilash Someshwar Das S. R. Kalsi M. Das Gupta K. Mohankumar John P. George S. K. Banerjee S. B. Thampi D. Pradhan 《Pure and Applied Geophysics》2007,164(8-9):1491-1509
Pre-monsoon rainfall around Kolkata (northeastern part of India) is mostly of convective origin as 80% of the seasonal rainfall
is produced by Mesoscale Convective Systems (MCS). Accurate prediction of the intensity and structure of these convective
cloud clusters becomes challenging, mostly because the convective clouds within these clusters are short lived and the inaccuracy
in the models initial state to represent the mesoscale details of the true atmospheric state. Besides the role in observing
the internal structure of the precipitating systems, Doppler Weather Radar (DWR) provides an important data source for mesoscale
and microscale weather analysis and forecasting. An attempt has been made to initialize the storm-scale numerical model using
retrieved wind fields from single Doppler radar. In the present study, Doppler wind velocities from the Kolkata Doppler weather
radar are assimilated into a mesoscale model, MM5 model using the three-dimensional variational data assimilation (3DVAR)
system for the prediction of intense convective events that occurred during 0600 UTC on 5 May and 0000 UTC on 7 May, 2005.
In order to evaluate the impact of the DWR wind data in simulating these severe storms, three experiments were carried out.
The results show that assimilation of Doppler radar wind data has a positive impact on the prediction of intensity, organization
and propagation of rain bands associated with these mesoscale convective systems. The assimilation system has to be modified
further to incorporate the radar reflectivity data so that simulation of the microphysical and thermodynamic structure of
these convective storms can be improved. 相似文献
98.
M. C. Gupta V. P. Krishnarajan Shailesh Nayak 《Journal of the Indian Society of Remote Sensing》2001,29(1-2):79-83
Aquaculture has emerged as one of the fast growing industries in the developing countries both for domestic consumption as well as for the export. This industry not only generates foreign exchange to the country but also provides employment opportunities to the skilled and unskilled rural poor. On the other hand, aquaculture has also some negative impacts on the environment which are mainly due to conversion of mangroves and agricultural, salination of surface water resources and agricultural land at some places besides causing pollution and diseases. All the major shrimp farming countries of the world have faced environmental problem due to intensification, improper and uncontrolled planning by greed and unlimited profit motives of a section of aquaculture community. In view of this, a proper environmental management is a basic need to sustain the industry in the long run. Selection of a suitable site in the coastal areas is the first and the foremost step which is a crucial factor in determining the success of shrimp farming. The present paper discusses the selection of brackish water aquaculture sites using remote sensing satellite data and GIS on the Cannanore coast. Different aquaculture sites in the area were evaluated using a GIS package. Finally a prioritization map showing the sites in the descending order of their priority was generated. 相似文献
99.
100.
V Hari Prasad A K Chakraborti T R Nayak 《Journal of the Indian Society of Remote Sensing》1996,24(2):85-96
Monitoring the crop acreage and irrigation water requirements vis-a-vis irrigation water supplies is important to obtain a realistic view of the “irrigation potential” and “potential utilised”. Satellite data provides information on crop area and thereby net irrigation water requirements of crops. A pilot study was taken up in Mahendragarh distributary canal in Haryana State to estimate net irrigation water requirement of crops under 17 minors for kharif and rabi seasons of 1992–93 period using IRS-1B satellite geocoded FCC images. These water requirements, when analysed with canal and tubewell water supplies for crops, show largescale deficiencies in the irrigation command area. 相似文献