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31.
R. S. Tiwari Manoj K. Arora T. Kailash 《Journal of the Indian Society of Remote Sensing》1999,27(4):225-234
With increasing resolution of the remotely sensed data the problems of images contaminated by mixed pixels arc frequent. Conventional
classification techniques often produce erroneous results when applied to images dominated by mixed pixels. This may load
to unrealistic representation of land cover, thereby, affecting efficient planning, management and monitoring of natural resources.
Consequently, soft classification techniques providing sub-pixel land cover information may have to be utilised.
From a range of soft classification techniques, the present study focuses on the utility of conventional maximum likelihood
classifier and linear mixture modelling for sub-pixel. land cover classifications. The accuracy of the soft classifications
has been assessed using distance measures and correlation co-efficient. The results show that linear mixture modelling has
produced accuracies comparable to maximum likelihood classifier. Besides this the correlations between actual land cover proportions
and proportions from linear mixture modelling, though not strong, arc statistically significant at 95% level of confidence.
It has also been observed that the normalised likelihoods of maximum likelihood classifier also show strong correlations with
the actual land cover proportions on ground and therefore has the potential to be used as a soft classification technique. 相似文献
32.
R. Tatavarti A. C. Narayana P. Manoj Kumar Shyam Chand 《Journal of Earth System Science》1999,108(1):57-68
Field experiments conducted in the nearshore ocean to understand the dynamics of mudbank off Kerala, south-west coast of India,
are highlighted. Real time monitoring of the nearshore ocean off Purakkad, Kerala was accomplished using pressure transducers
for nearshore surface wave measurements, and current sensors for nearshore velocity measurements. Comprehensive information
on the spatial structure of mudbank was obtained from aerial surveys. Extensive data collected on surface waves and currents
in the nearshore ocean, indicate that the infra-gravity (IG) waves (leaky modes and trapped edge wave modes), and far infra-gravity
(FIG) waves coupled with strong shoreline reflections and undertow play an important role in the dynamics associated with
the mudbanks off Kerala during the monsoon season. During the non-monsoon season evidence for progressive edge waves in the
infragravity frequency band, an energetic gravity wave band and a strong undertow with weak reflections was observed. 相似文献
33.
Crop classification using biologically-inspired techniques with high resolution satellite image 总被引:5,自引:0,他引:5
S. N. Omkar J. Senthilnath Dheevatsa Mudigere M. Manoj Kumar 《Journal of the Indian Society of Remote Sensing》2008,36(2):175-182
Remote sensing provides a lucid and effective means for crop coverage identification. Crop coverage identification is a very
important technique, as it provides vital information on the type and extent of crop cultivated in a particular area. This
information has immense potential in the planning for further cultivation activities and for optimal usage of the available
fertile land. As the frontiers of space technology advance, the knowledge derived from the satellite data has also grown in
sophistication. Further, image classification forms the core of the solution to the crop coverage identification problem.
No single classifier can prove to satisfactorily classify all the basic crop cover mapping problems of a cultivated region.
We present in this paper the experimental results of multiple classification techniques for the problem of crop cover mapping
of a cultivated region. A detailed comparison of the algorithms inspired by social behaviour of insects and conventional statistical
method for crop classification is presented in this paper. These include the Maximum Likelihood Classifier (MLC), Particle
Swarm Optimisation (PSO) and Ant Colony Optimisation (ACO) techniques. The high resolution satellite image has been used for
the experiments. 相似文献
34.
Maintaining real-time precise point positioning during outages of orbit and clock corrections 总被引:1,自引:1,他引:0
The precise point positioning (PPP) is a popular positioning technique that is dependent on the use of precise orbits and clock corrections. One serious problem for real-time PPP applications such as natural hazard early warning systems and hydrographic surveying is when a sudden communication break takes place resulting in a discontinuity in receiving these orbit and clock corrections for a period that may extend from a few minutes to hours. A method is presented to maintain real-time PPP with 3D accuracy less than a decimeter when such a break takes place. We focus on the open-access International GNSS Service (IGS) real-time service (RTS) products and propose predicting the precise orbit and clock corrections as time series. For a short corrections outage of a few minutes, we predict the IGS-RTS orbits using a high-order polynomial, and for longer outages up to 3 h, the most recent IGS ultra-rapid orbits are used. The IGS-RTS clock corrections are predicted using a second-order polynomial and sinusoidal terms. The model parameters are estimated sequentially using a sliding time window such that they are available when needed. The prediction model of the clock correction is built based on the analysis of their properties, including their temporal behavior and stability. Evaluation of the proposed method in static and kinematic testing shows that positioning precision of less than 10 cm can be maintained for up to 2 h after the break. When PPP re-initialization is needed during the break, the solution convergence time increases; however, positioning precision remains less than a decimeter after convergence. 相似文献
35.
Manoj Khanal Deepak Adhikary Chandana Jayasundara Rao Balusu 《Geotechnical and Geological Engineering》2016,34(1):217-235
This paper investigates various multiseam mining related parameters using mine site specific data and numerical simulations. Two important mining effects—subsidence and stress—are analysed for different possible mining layouts. A geological mine dataset has been used to generate a numerical model. The predicted surface subsidence magnitude and surface profile have been compared under different scenarios to assess potential options in multiseam mining strategies. The effects that seam separation distances, mining offset, panel layout and panel orientation each have on surface subsidence and chain pillar stress magnitude have been investigated. The numerical simulation shows that ascending or descending mining directions have little impact on controlling the surface subsidence in multiseam mining and predicted an almost identical maximum stress development at the chain pillars. Numerical simulations infer that the orientation of the top panels control the subsidence profile. 相似文献
36.
The Ninetyeast Ridge north of the equator in the eastern Indian Ocean is actively deforming as evidenced by seismicity and its eastward subduction below the Andaman Trench. Basement of the ridge is elevated nearly 2 km with respect to the Bengal Fan; seismic surveys demonstrate continuity of the ridge beneath sediment for 700 km north of 10° N where the ridge plunges below the Fan sediment. The ridge is characterised by a free-air gravity high of 50 mgal amplitude and 350 km wavelength, and along-strike continuity of 1500 km in a north-south direction, closely fringing (locally, even abutting) the Andaman arc-trench bipolar gravity field. Regression analysis between gravity and bathymetry indicates that the ridge gravity field cannot be explained solely by its elevation. The ridge gravity field becomes gradually subdued northwards where overlying Bengal Fan sediments have a smaller density contrast with the ridge material. Our gravity interpretation, partly constrained by seismic data, infers that the ridge overlies significant crustal mass anomalies consistent with the hot spot model for the ridge. The anomalous mass is less dense by about 0.27 g cm–3 than the surrounding oceanic upper mantle, and acts as a cushion for isostatic compensation of the ridge at the base of the crust. This cushion is up to 8 km thick and 400–600 km wide. Additional complexities are created by partial subduction of the ridge below the Andaman Trench that locally modifies the arc-trench gravity field. 相似文献
37.
M. C. Ramadevi S. Seetha Dipankar Bhattacharya B. T. Ravishankar N. Sitaramamurthy G. Meena M. Ramakrishna Sharma Ravi Kulkarni V. Chandra Babu Kumar Brajpal Singh Anand Jain Reena Yadav S. Vaishali B. N. Ashoka Anil Agarwal K. Balaji G. Nagesh Manoj Kumar Dhruti Ranjan Gaan Prashanth Kulshresta Pankaj Agarwal Mathew Sebastian A. Rajarajan D. Radhika Anuj Nandi V. Girish Vivek Kumar Agarwal Ankur Kushwaha Nirmal Kumar Iyer 《Experimental Astronomy》2017,44(1):11-23
Scanning Sky Monitor (SSM) onboard AstroSat is an Xray sky monitor in the soft X-ray band designed with a large field of view to detect and locate transient X-ray sources and alert the astronomical community about interesting phenomena in the X-ray sky. SSM comprises position sensitive proportional counters with 1D coded mask for imaging. There are three detector units mounted on a platform capable of rotation which helps covering about 50% of the sky in one full rotation. This paper discusses the elaborate details of the instrument and few immediate results from the instrument after launch. 相似文献
38.
Acta Geotechnica - The forced vertical vibration tests were performed in the field on 3.3-m-long driven steel pipe on a single vertical pile, P1 (β?=?0°), and single batter... 相似文献
39.
Mechanisms for the land/sea warming contrast exhibited by simulations of climate change 总被引:3,自引:3,他引:0
Manoj M. Joshi Jonathan M. Gregory Mark J. Webb David M. H. Sexton Tim C. Johns 《Climate Dynamics》2008,30(5):455-465
The land/sea warming contrast is a phenomenon of both equilibrium and transient simulations of climate change: large areas
of the land surface at most latitudes undergo temperature changes whose amplitude is more than those of the surrounding oceans.
Using idealised GCM experiments with perturbed SSTs, we show that the land/sea contrast in equilibrium simulations is associated
with local feedbacks and the hydrological cycle over land, rather than with externally imposed radiative forcing. This mechanism
also explains a large component of the land/sea contrast in transient simulations as well. We propose a conceptual model with
three elements: (1) there is a spatially variable level in the lower troposphere at which temperature change is the same over
land and sea; (2) the dependence of lapse rate on moisture and temperature causes different changes in lapse rate upon warming
over land and sea, and hence a surface land/sea temperature contrast; (3) moisture convergence over land predominantly takes
place at levels significantly colder than the surface; wherever moisture supply over land is limited, the increase of evaporation
over land upon warming is limited, reducing the relative humidity in the boundary layer over land, and hence also enhancing
the land/sea contrast. The non-linearity of the Clausius–Clapeyron relationship of saturation specific humidity to temperature
is critical in (2) and (3). We examine the sensitivity of the land/sea contrast to model representations of different physical
processes using a large ensemble of climate model integrations with perturbed parameters, and find that it is most sensitive
to representation of large-scale cloud and stomatal closure. We discuss our results in the context of high-resolution and
Earth-system modelling of climate change. 相似文献
40.
Impact of seismic factors on landslide susceptibility zonation: a case study in part of Indian Himalayas 总被引:6,自引:0,他引:6
Landslides are one of the most widespread natural hazards in high mountain terrains such as the Himalayas, which are one of
the youngest tectonically and seismically active mountain ranges in the world. The crustal movements along the longitudinal
thrusts and transverse faults give rise to earthquakes and in turn initiate landslides in the region. In fact, in addition
to various static factors causing landslides, earthquakes are one of the major causes of landslides. It is thus imperative
to incorporate seismic factor also while carrying out landslide susceptibility zonation map preparation in a seismically active
areas like Garhwal Himalayas. In this paper, a study on the effect of earthquakes on landslide susceptibility zonation has
been demonstrated by taking Chamoli earthquake as an example. 相似文献