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771.
An Introduction to MODISI and SCMOD Methods for Correction of the MODIS Snow Assessment Algorithm 总被引:1,自引:0,他引:1
Mohammad Reza Mobasheri Hossein Shafizadeh Moghadam Siavosh Shayan 《Journal of the Indian Society of Remote Sensing》2010,38(4):674-685
Detection, monitoring and precise assessment of the snow covered regions is an important issue. Snow cover area and consequently
the amount of runoff generated from snowmelt have a significant effect on water supply management. To precisely detect and
monitor the snow covered area we need satellite images with suitable spatial and temporal resolutions where we usually lose
one for the other. In this study, products of two sensors MODIS and ASTER both on board of TERRA platform having low and high
spatial resolution respectively were used. The objective of the study was to modify the snow products of MODIS by using simultaneous
images of ASTER. For this, MODIS snow index image with high temporal resolution were compared with that of ASTER, using regression
and correlation analysis. To improve NDSI index two methods were developed. The first method generated from direct comparison
of ASTER averaged NDSI with those of MODIS (MODISI). The second method generated by dividing MODIS NDSI index into 10 codes
according to their percentage of surface cover and then compared the results with the difference between ASTER averaged and
MODIS snow indices (SCMOD). Both methods were tested against some 16 MODIS pixels. It is found that the precision of the MODISI
method was more than 96%. This for SCMOD was about 98%. The RMSE of both methods were as good as 0.02. 相似文献
772.
Michael Huettner Annette Freibauer Constanze Haug Uwe Cantner 《Carbon balance and management》2010,5(1):2
The 'Copenhagen Accord' fails to deliver the political framework for a fair, ambitious and legally-binding international climate
agreement beyond 2012. The current climate policy regime dynamics are insufficient to reflect the realities of topical complexity,
actor coalitions, as well as financial, legal and institutional challenges in the light of extreme time constraints to avoid
'dangerous' climate change of more than 2°C. In this paper we analyze these stumbling blocks for international climate policy
and discuss alternatives in order to regain momentum for future negotiations. 相似文献
773.
In the past researchers have suggested hard classification approaches for pure pixel remote sensing data and to handle mixed
pixels soft classification approaches have been studied for land cover mapping. In this research work, while selecting fuzzy
c-means (FCM) as a base soft classifier entropy parameter has been added. For this research work Resourcesat-1 (IRS-P6) datasets
from AWIFS, LISSIII and LISS-IV sensors of same date have been used. AWIFS and LISS-III datasets have been used for classification
and LISS-III and LISS-IV data were used for reference data generation, respectively. Soft classified outputs from entropy
based FCM classifiers for AWIFS and LISS-III datasets have been evaluated using sub-pixel confusion uncertainty matrix (SCM).
It has been observed that output from FCM classifier has higher classification accuracy with higher uncertainty but entropy-based
classifier with optimum value of regularizing parameter generates classified output with minimum uncertainty. 相似文献
774.
Kinematic precise point positioning at remote marine platforms 总被引:6,自引:2,他引:6
Precise kinematic differential positioning using the global positioning system (GPS) at a marine platform usually requires
a relatively short distance (e.g. <500 km) to a land-based reference station. As an alternative, precise point positioning
(PPP) is normally considered free from this limiting requirement. However, due to the prerequisite of network-based satellite
products, PPP at a remote marine platform may still be affected by its distance to the reference network. Hence, this paper
investigates this scenario by configuring rings of reference stations with different radii centered on a to-be-positioned
marine platform. Particularly, we applied ambiguity resolution at a single station to PPP by estimating uncalibrated phase
delays (UPDs). We used three rings of reference stations centered on a vessel, with radii of roughly 900, 2,000 and 3,600 km,
to determine satellite clocks and UPDs independently. For comparison, we also performed differential positioning based on
a single reference station with baseline lengths of about 400, 1,700 and 2,800 km. We demonstrate that, despite the increasing
ring-network radius to a few 1,000 km, the overall change in accuracy of the satellite clocks that are used at the vessel
is smaller than 0.02 ns, and the RMS values of differences between the three sets of narrow-lane UPD estimates are around
0.05 cycles only. Moreover, the kinematic positioning accuracy of PPP is affected by the increasing ring-network radius, but
can still achieve several centimeters after ambiguity resolution when the vessel is over a few 1,000 km away from the ring
network, showing better performance than that of differential positioning. Therefore, we propose that ambiguity-fixed PPP
can be used at remote marine platforms that support precise oceanographic and geophysical applications in open oceans. 相似文献
775.
The grid DEM(digital elevation model) generation can be from any of a number of sources:for instance,analogue to digital conversion of contour maps followed by application of the TIN model,or direct elevation point modelling via digital photogrammetry applied to airborne images or satellite images.Currently,apart from the deployment of point-clouds from LiDAR data acquisition,the generally favoured approach refers to applications of digital photogrammetry.One of the most important steps in such deployment i... 相似文献
776.
Recently,the expertise accumulated in the field of geovisualization has found application in the visualization of abstract multidimensional data,on the basis of methods called spatialization methods.Spatialization methods aim at visualizing multidimensional data into low-dimensional representational spaces by making use of spatial metaphors and applying dimension reduction techniques.Spatial metaphors are able to provide a metaphoric framework for the visualization of information at different levels of gran... 相似文献
777.
Pavagada taluk of Tumkur district in Karnataka is one of the most backward taluks receiving less than 500 mm annual rainfall.
The maximum area of the taluk is under monocropping, reasons for the same were not documented well. The present study was
carried out using remote sensing data along with field survey and laboratory analysis for assessing the potentials and limitations
of soil. Using the basic information on soil, climate and topography based on the matching exercise between the growth and
production requirements of the crop, suitability of soils for groundnut, paddy and finger millet was assessed as per FAO land
evaluation. The soil suitability maps were prepared using Arc GIS software. About 48 per cent of the total area was moderate
to marginally suitable and 13 per cent of the area was not suitable for both groundnut and finger millet. Lowland areas covering
12 per cent of the area was highly suitable, 15 per cent was moderate to marginally suitable and 20 per cent was not suitable
for paddy cultivation. 相似文献
778.
A geodetic boundary value problem (GBVP) approach has been formulated which can be used for solving the problem of height
datum unification. The developed technique is applied to a test area in Southwest Finland with approximate size of 1.5° ×
3° and the bias of the corresponding local height datum (local geoid) with respect to the geoid is computed. For this purpose
the bias-free potential difference and gravity difference observations of the test area are used and the offset (bias) of
the height datum, i.e., Finnish Height Datum 2000 (N2000) fixed to Normaal Amsterdams Peil (NAP) as origin point, with respect
to the geoid is computed. The results of this computation show that potential of the origin point of N2000, i.e., NAP, is
(62636857.68 ± 0.5) (m2/s2) and as such is (0.191 ± 0.003) (m) under the geoid defined by W
0 = 62636855.8 (m2/s2). As the validity test of our methodology, the test area is divided into two parts and the corresponding potential difference
and gravity difference observations are introduced into our GBVP separately and the bias of height datums of the two parts
are computed with respect to the geoid. Obtaining approximately the same bias values for the height datums of the two parts
being part of one height datum with one origin point proves the validity of our approach. Besides, the latter test shows the
capability of our methodology for patch-wise application. 相似文献
779.
Bovolo F. Bruzzone L. Capobianco L. Garzelli A. Marchesi S. Nencini S. 《Geoscience and Remote Sensing Letters, IEEE》2010,7(1):53-57
780.
Assessment of the LandStar Real-Time DGPS Service under Several Operational Conditions 总被引:1,自引:0,他引:1
LandStar is a differential global positioning service (DGPS) that provides 24-h real-time positioning for various applications
on land, water, and air in North America, Australia, New Zealand, Europe, and Africa. Its focus is on real-time applications
requiring a submeter positioning capability such as agriculture, forestry, Geospatial Information Systems (GIS), survey/mapping,
and land/vehicular navigation. LandStar uses a Wide Area Network of reference stations to derive DGPS corrections to model
the variation of GPS error sources over a large area. These model parameters are used by the Virtual Reference Station processors
to calculate standard corrections that are available for all predefined locations in the network. The corrections are transmitted
to the user by L-band satellite communication in the standard RTCM SC104 DGPS correction format. This article investigates
the performance of the LandStar Mk III system under various operational conditions and assesses its performance in both static
and kinematic modes. Four field tests were conducted during 12 months that tested the sysem in clear static and kinematic
conditions as well as suboptimal environments associated with low and heavy foliage conditions. Both the accuracy and availability
of the system under these conditions is investigated, with an emphasis on whether the above variables are caused by the LandStar
system differential corrections, the GPS measurements, or a combination of both. ? 1999 John Wiley & Sons, Inc. 相似文献