首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   53篇
  免费   4篇
  国内免费   4篇
测绘学   2篇
大气科学   1篇
地球物理   11篇
地质学   40篇
海洋学   2篇
天文学   4篇
综合类   1篇
  2024年   1篇
  2023年   2篇
  2022年   1篇
  2021年   3篇
  2020年   2篇
  2019年   1篇
  2018年   7篇
  2017年   4篇
  2016年   7篇
  2015年   4篇
  2014年   8篇
  2013年   7篇
  2012年   2篇
  2011年   1篇
  2010年   1篇
  2009年   1篇
  2008年   3篇
  2007年   1篇
  2005年   1篇
  1998年   1篇
  1996年   1篇
  1986年   2篇
排序方式: 共有61条查询结果,搜索用时 156 毫秒
41.
The classical genetic algorithm is a stochastic process which operates by natural selection. Although the algorithm may localize a point around the global minimum of the misfit function, it is not efficient at finding the precise solution. This paper suggests some hybrid genetic algorithms, derived from evolution theories, to overcome this problem. Firstly, sexual selection has been incorporated in the classical genetic algorithm to obtain a full representation of the Darwinist evolution concept. The simulation of sexual selection is performed by assigning a higher probability of surviving to some parameters that satisfy some algebraic relationships. This method is called the ‘marked constraints’ algorithm since it permits us to insert geological and geophysical constraints into the problem. The algorithm implementation is realized by progressively shrinking the parameter search space through successive generations. In this way, the genetic algorithm gains some degree of determinism. Secondly, since the evolution theory of Lamarck postulates that the acquired traits are passed on to the next generation, a hybrid use of the damped least‐squares method and the genetic algorithm is called Lamarckian inversion. Lamarckian inversion involves some improvement procedures that simulate the reduction of the misfit with the help of a derivative‐based method between two generations. Finally, although there is no correspondence in nature, Lamarckian and Darwinist evolution concepts are combined to strengthen the deterministic part of the solution algorithm. This is called the Lamarckian‐marked‐constraint algorithm. The merits and behaviours of the suggested algorithms are discussed using two examples. The first is a hypothetical example affected by a multiminima problem. The second examines the equivalence problem using vertical electrical sounding data.  相似文献   
42.
The increase in the popularity of using environmental design criteria in town and country planning has brought about the need to fully identify the principles to determine the best location of hazardous wastes to be landfilled. This environmental management issue has received considerable attention because of its applications in urban and rural infrastructure planning, industrial development planning as well as health, housing, transportation and agricultural schemes. This paper explains a method to determine how to locate suitable sites for hazardous waste landfilling area by using the site screening study. It demonstrates how the criteria such as geology, topography, land use, climate, earthquake and other related factors can be introduced into the overlayer technique to determine the suitable site selection in a region. The research was undertaken in the Southeastern Anatolia Project (known as GAP in Turkey) region where identifying the land resources is crucial for agricultural and water management purposes. The paper also explains the validity of the method employed on the site selection process for hazardous wastes. The introduced method may enable more accurate design procedure for planning in environmental management in future.  相似文献   
43.
Inverse Problem in Ground Water: Model Development   总被引:1,自引:0,他引:1  
  相似文献   
44.
To obtain the shear wave velocity profile for engineering application to near-subsurface, many geophysical techniques are used. The dispersion curve alone is unable to provide deeper shear wave velocity information for deep soil deposit; therefore, a joint inversion of dispersion curves with the horizontal over vertical (H/V) (i.e., apparently ellipticity) curve is recommended. The H/V curve obtained from the microtremor recording contains a major part of Love wave contribution to the noise wavefield horizontal component. Due to this presence of Love wave fraction, the H/V curve does not completely replicate the ellipticity of Rayleigh wave. In this study, we try to compare the Rayleigh wave ellipticity obtained from the borehole velocity model to the H/V curve obtained at the same locality from seismic ambient noise recording. Two different techniques available for the Love effect minimization are tested and compared with the borehole ellipticity. Finally, the joint inversion of H/V and dispersion curve is made, which shows great correspondence with the previous measurement at the site.  相似文献   
45.
The origin of the nearly circular Colônia structure, located at the southwestern edge of the city of São Paulo, Brazil, has been the subject of a long‐standing debate, ever since the 1960s when the structure was first investigated by geophysical methods. The structure still raises interest for geological research, as its sedimentary infill holds important paleoclimatic information about the evolution of the tropical rainforest, as well as the interplay between the South American summer monsoon, the Intertropical Convergence Zone, and the southern Westerly wind belt—for possibly as long as several million years. In addition, the search for evidence to conclusively establish the origin of this structure continues, and the answer most likely lies in the lower portions of the basin's sedimentary infill, which also holds a significant potential for underground water resources. Here, we present the results from recent seismic (reflection and HVSR), gravimetric, and geoelectrical surveys. They have provided a reliable image of the sedimentary infill, and the maximum depth to basement within the structure has been constrained consistently by the different methods to approximately ?400 m. The geophysical data have also allowed to map the lateral contact between the crystalline basement rocks and the sedimentary infill, which indicates a diameter of approximately 2.8 km for the sedimentary basin, with 3.6 km being the diameter of the outermost limit of the structure. A total of six seismic stratigraphic boundaries were identified within the sedimentary infill, providing a framework for the planning of a deep drilling campaign and subsequent sampling program aimed at geological and paleoclimatology studies.  相似文献   
46.
Geospatial techniques play a crucial role in geomorphic studies, particularly in the challenging terrains like mountainous regions, inaccessible areas and densely vegetated landscapes, where geomorphic features cannot be recorded easily. Tectono-geomorphologic observations provide important clues regarding the landscape evolution, morpho-dynamics and ongoing tectonism of the region. The present study has been carried out in the Zanskar Basin (ZB), located to the south of the Indus Tsangpo Suture Zone (ITSZ), in the hinterland of the NW Himalaya. This study has been carried out to assess and evaluate active tectonics by employing tectono-geomorphic analysis, dynamics in drainage networks, geomorphological field observations and the Geographic Information System (GIS) environment. High-resolution satellite images, topographic maps and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) were used to generate primary data sets, which were corroborated with field investigations for valid inferences. The geometry of the ZB suggests that continuous tectonic activity exerts first-order control on the overall shape, size and structure of the ZB. This first-order response is clearly reflected in the landforms modified by tectonic processes, namely, linear mountain fronts, elongated shape and tilting of the basin, braided and meandering river courses and lower stream length gradient index values in hard rock terrain. The ZB exhibits several eye-catching geomorphic features, such as well-defined triangular facets with wide base lengths and wine-glass valleys with small outlets along the footwall block of the Zanskar Shear Zone/South Tibetan Detachment System (ZSZ/STDS), as well as the presence of wind gaps, water gaps, bedrock incision, incised and entrenched valleys, narrow gorges and a high incision rate inferring active tectonics and recent uplift in the region. In addition, the existence of uplifted river terraces, as well as the stepped morphology of fans and strath terraces, suggests that the region is experiencing recent activity and ongoing tectonic uplift. These modified geomorphic characteristics suggest that the hinterland, which is part of the NW Himalaya, is tectonically quite active and has experienced a differential rate of tectonics during its evolution. The quantified geomorphic indices and their relations with the tectonics, climate and erosion activity infer that the basin geometry is mostly controlled by the ZSZ/STDS that dips 20°–70° NE, the south-dipping Zanskar Counter Thrust (ZCT) and other local tectonic elements like the Choksti Thrust (CT), Stondgey Thrust, Zangla Thrust and tectonic structures. The synergised results of quantified geomorphic indices and tectono-geomorphic evidence in the ZB strongly indicate that both the past and ongoing tectonism have significantly shaped and modified geomorphology of the ZB.  相似文献   
47.
In this study, Land Surface Temperature(LST) and its lapse rate over the mountainous Kashmir Himalaya was estimated using MODIS data and correlated with the observed in-situ air temperature(Tair) data. Comparison between the MODIS LST and Tair showed a close agreement with the maximum error of the estimate ±1°C and the correlation coefficient 0.90. Analysis of the LST data from 2002-2012 showed an increasing trend at all the selected locations except at a site located in the southeastern part of Kashmir valley. Using the GTOPO30 DEM, MODIS LST data was used to estimate the actual temperature lapse rate(ATLR) along various transects across Kashmir Himalaya, which showed significant variations in space and time ranging from 0.3°C to 1.2°C per 100 m altitude change. This observation is at variance with the standard temperature lapse rate(STLR) of 0.65°C used universally in most of the hydrological and other land surface models. Snowmelt Runoff Model(SRM) was used to determine the efficacy of using the ATLR for simulating the stream flows in one of the glaciated and snow-covered watersheds in Kashmir. The use of ATLR in the SRM model improved the R2 between the observed and predicted streamflows from 0.92 to 0.97.It is hoped that the operational use of satellite-derived LST and ATLR shall improve the understanding and quantification of various processes related to climate, hydrology and ecosystem in the mountainous and data-scarce Himalaya where the use of temperature and ATLR are critical parameters for understanding various land surface and climate processes.  相似文献   
48.
Devrim  Akca  Armin  Gruen 《The Photogrammetric Record》2009,24(127):217-245
This paper examines the potential of mobile phones to be used as front-end sensors for photogrammetric procedures and applications. For this purpose, two mobile phone cameras (Sony Ericsson K750i and Nokia N93) were calibrated over an indoor 3D testfield, using a self-calibrating bundle adjustment. Geometric accuracy tests were carried out in order to evaluate their metric performances and to compare the results with respect to two off-the-shelf digital still video cameras (Sony DSC W100 and Sony DSC F828). The geometric accuracy evaluation comprised an absolute accuracy test, JPEG test and temporal stability test. The radiometric capabilities of all cameras (except that the DSC W100 was replaced with a DSC T100 camera) were also evaluated and compared by carrying out modulation transfer function (MTF) analysis, image noise analysis and an operating range test. Substantial systematic errors were diagnosed in some systems. However, with proper calibration it is believed that these devices can be used for many photogrammetric tasks.  相似文献   
49.
Geoelectric and hydrochemical approaches are employed to delineate the ground-water potential zones in District Okara, a part of Bari Doab, Punjab, Pakistan. Sixty-seven VES surveys are conducted with the Electrical Resistivity Meter. The resultant resistivity verses depth model for each site is estimated using computer-based software IX1D. Aquifer thickness maps and interpreted resistivity maps were generated from interpreted VES results. Dar-Zarrouk parameters, transverse resistance (TR), longitudinal conductance (SL) and anisotropy (λ) were also calculated from resistivity data to delineate the potential zones of aquifer. 70% of SL value is ≤3S, 30% of SL value is > 3S. According to SL and TR values, the whole area is divided into three potential zones, high, medium and low potential zones. The spatial distribution maps show that north, south and central parts of study area are marked as good potential aquifer zones. Longitudinal conductance values are further utilized to determine aquifer protective capacity of area. The whole area is characterized by moderate to good and up to some extent very good aquifer protective area on the basis of SL values. The groundwater samples from sixty-seven installed tube wells are collected for hydro-chemical analysis. The electrical conductivity values are determined. Correlation is then developed between the EC (μS/cm) of groundwater samples vs. interpreted aquifer resistivity showing R2 value 0.90.  相似文献   
50.
Nine positions of comet Hale-Bopp (1995 O1), derived from the X-Y positions on Bosscha Schmidt plates, taken between August 15 to August 22, 1995, are given.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号