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1.
Alessandro Tarantino Andrew M. Ridley David G. Toll 《Geotechnical and Geological Engineering》2008,26(6):751-782
This paper presents a review of techniques for field measurement of suction, water content, and water hydraulic conductivity
(permeability). Main problems in the use of field tensiometers are addressed and hints on how to improve tensiometer performance
are given. Advantages and limitations of instruments for indirect measurement of suction including electrical conductivity
sensors, thermal conductivity sensors, dielectric permittivity sensors, filter paper, and psychrometer are discussed. Techniques
for water content measurement based on dielectric methods are then presented. These include time and amplitude domain reflectometry
and capacitance. Finally, a brief overview of methods for measurement of water permeability in the field is presented. 相似文献
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In the summer and fall of 2012, during the GLAD experiment in the Gulf of Mexico, the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE) used several ocean models to assist the deployment of more than 300 surface drifters. The Navy Coastal Ocean Model (NCOM) at 1 km and 3 km resolutions, the US Navy operational NCOM at 3 km resolution (AMSEAS), and two versions of the Hybrid Coordinates Ocean Model (HYCOM) set at 4 km were running daily and delivering 72-h range forecasts. They all assimilated remote sensing and local profile data but they were not assimilating the drifter’s observations. This work presents a non-intrusive methodology named Multi-Model Ensemble Kalman Filter that allows assimilating the local drifter data into such a set of models, to produce improved ocean currents forecasts. The filter is to be used when several modeling systems or ensembles are available and/or observations are not entirely handled by the operational data assimilation process. It allows using generic in situ measurements over short time windows to improve the predictability of local ocean dynamics and associated high-resolution parameters of interest for which a forward model exists (e.g. oil spill plumes). Results can be used for operational applications or to derive enhanced background fields for other data assimilation systems, thus providing an expedite method to non-intrusively assimilate local observations of variables with complex operators. Results for the GLAD experiment show the method can improve water velocity predictions along the observed drifter trajectories, hence enhancing the skills of the models to predict individual trajectories. 相似文献
4.
本文介绍的模拟开关自动换挡滤波器,已在生产中使用,性能良好。本文着重介绍控制电路的设计原理、特点及使用方法,并对滤波电路部分作一定的讨论。由于模拟开关在导通时,存在导通电阻R_s,本文推出了加入R_s后的电路传输函数,设计了程序,计算加入R_s后的滤波器的幅频特性、相频特性,并与R_s=0的电路比较,来讨论能否满足仪器对滤波器的要求,以及减少R_s影响的办法。 相似文献
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几种滤波器对地面飑线场的中尺度滤波试验 总被引:4,自引:0,他引:4
本文用Barnes带通滤波法,二十五点格式滤波法,对含有地面幅合线和飑线的地面加密观测资料和客观分析资料进行了中尺度滤波试验,结果表明,三种滤波器的作用结果都胡有效突出地面辐合线和飑线的中尺度特征,其中Barnes法的性能和结果较理想,二十五点法和高阶高通法各有特点。 相似文献
6.
The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.Responsible Editor: Jörg-Olaf Wolff 相似文献
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A commercial version of the prototype New Zealand narrowband interference filter instrument has been run at Garmisch-Partenkirchen since autumn 1977. The vicinity of the Dobson stations Hohenpeissenberg and Arosa permitted a check of the filter instrument's utility, reliability and long-term stability in total ozone measurement by (i) station to station-or short-range intercomparisons of daily means and (ii) a several days' direct intercomparison at Arosa in spring 1978.The regression analysis with the Hohenpeissenberg data-covering the five month autumn-winter 1977/78 period with highly variable ozone-shows that the filter instrument's direct-sun modeX
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total ozone values were systematically too low by a conversion factor of 0.93. The excellent proportionality between the instruments is indicated by the standard deviation of only 1,3%. The (–7.0±1.3%) bias perfectly agrees with the result reported byBasher [1] for a similar, yet direct, intercomparison.During the direct Arosa intercomparison the filter instrument also tracked down short-time variations in a remarkable, though biased, parallelism with the Dobson instruments, and theX
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daily means fit well into the prognostic relationship derived from the preceding autumn-winter short-range intercomparison.A creeping deterioration of the characteristics of the 305.5 nm double filter then prevented any furtherX
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total ozone intercomparison. No final decision is possible whether this behaviour after a half year's run is typical or just an unusual exception. The otherwise excellent long-term stability is demonstrated by the comparison of theX
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daily means with the HohenpeissenbergX
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data for a 1 1/2 year's period (autumn 1977–spring 1979), resulting in the same bias relationship as for theX
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total ozone measurements. 相似文献
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