全文获取类型
收费全文 | 238篇 |
免费 | 19篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 39篇 |
大气科学 | 18篇 |
地球物理 | 72篇 |
地质学 | 51篇 |
海洋学 | 34篇 |
天文学 | 25篇 |
综合类 | 14篇 |
自然地理 | 21篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 3篇 |
2017年 | 12篇 |
2016年 | 7篇 |
2015年 | 15篇 |
2014年 | 15篇 |
2013年 | 14篇 |
2012年 | 7篇 |
2011年 | 16篇 |
2010年 | 3篇 |
2009年 | 21篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 18篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有274条查询结果,搜索用时 526 毫秒
121.
Yulun Zhou 《制图学和地理信息科学》2016,43(5):379-392
ABSTRACTIn the past decade, an explosion of data has taken place in Chinese cities due to widespread use of mobile Internet devices, Web 2.0 applications, and the development of the “Wired City.” With advances in data storage and high-performance computing, big/open urban data have opened up important avenues for urban studies, planning practice, and commercial consultancy. Urban researchers and planners are eager to make use of these abundant, sophisticated, and dynamic data to deepen their understanding on urban form and functions. However, in practice, access to such urban data is limited in China due to institutional constraints on data distribution and data holders’ hesitation to share data. And this hampers urban analytics. To draw reliable conclusions about the workings of complex urban systems, efficient and effective interoperation of multisource urban datasets is needed. Also, dealing with the heterogeneity between datasets is an equally critical challenge, especially for urban planners and government officers. They would derive value from data analytics, but have little data processing experience. To address these issues, we initiated SinoGrids (Plan Xu Xiake), a crowdsourcing platform that standardizes (or “downscales”) microscale urban data in China to facilitate its sharing and interoperation. To assess the performance evaluation of SinoGrids, we propose field-testing with actual urban data and their potential users. Digital desert, a son project of SinoGrids is also included. 相似文献
122.
Propagation of shallow water waves in an open parabolic channel using the WKB perturbation technique
A singular perturbation analysis based on the WKB technique to study the hydrodynamic performance of periodic ocean waves that are incident on an open parabolic channel of constant depth is proposed. We derive a linear model to predict the propagation of the long ocean waves into the channel. In this manner, the spatial distribution for the surface elevation of the ocean waves inside the channel as a function of two dimensionless parameters, namely, a kinematical parameter, κ and a geometrical parameter ε, is governed by a second-order ordinary differential equation. The kinematical parameter κ denotes the ratio of the potential head, due to gravity, to the kinetic head of the ocean waves along the longitudinal axis of the parabolic channel. Meanwhile, ε is a dimensionless geometrical parameter that represents a characteristic ratio of the parabolic channel. Using matching conditions, simple expressions for the reflection and transmission coefficients are obtained. 相似文献
123.
Live (stained) benthic foraminifera in the Whittard Canyon, Celtic margin (NE Atlantic) 总被引:1,自引:0,他引:1
P. Duros C. Fontanier E. Metzger A. PuscedduF. Cesbron H.C. de StigterS. Bianchelli R. DanovaroF.J. Jorissen 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(2):128-146
Living (Rose Bengal stained) benthic foraminifera were investigated at 18 deep-sea stations sampled in the Whittard Canyon area (NE Atlantic). The stations were positioned along 4 bathymetric transects ranging from 300 to 3000 m depth: two along the main canyon axes (Western and Eastern branches) and two along adjacent open slopes (Western and Eastern slopes). The aim of this study was to assess changes of foraminiferal standing stock, composition and microhabitat in relation to the physico-chemical conditions prevailing at and below the sediment-water interface in various canyon and open-slope environments. Minimal oxygen penetration depths and maximal diffusive oxygen uptakes were recorded at upper canyon stations, suggesting a high mineralisation rate. This is confirmed by the high phytopigment concentrations measured in the sediment of the upper canyon axes. Foraminiferal abundance was positively correlated with diffusive oxygen uptake and phytopigment concentration in the sediment. This suggests a control of organic matter fluxes on the foraminiferal communities. Foraminiferal abundance was generally higher along the canyon axis compared to open-slope sites at comparable water depths. The species composition varied with water depth along all four transects, but was also different between canyon branches and adjacent slopes. The silty/sandy intercalations at many of the deeper canyon stations may have been rapidly deposited by fairly recent gravity flows. At station 51WB (3002 m), the faunal characteristics (strong dominance, shallow infaunal microhabitats) suggest that the foraminiferal community is in an early state of ecosystem colonisation after these recent sedimentation events, which would have supplied the important amounts of phytopigments. 相似文献
124.
Pedro J. Amado Susana Martín-Ruíz Juan Carlos Suárez Armando Arellano Ferro Andrés Moya Ignasi Ribas Ennio Poretti 《Astrophysics and Space Science》2006,304(1-4):173-175
Photometric and spectroscopic results for the star HD 172189, member of the open cluster IC 4756 in the summer field of the space mission COROT, are presented. From photometric observations in the Strömgren system carried out at various epochs, its binary nature as well as the presence of a δ Scuti-type pulsating component have been discovered. The frequency analysis of the whole dataset confirms a dominant frequency of 19.5974 c d?1 with a maximum amplitude near 0.02 mag plus other frequencies in the range 18–20 c d?1. A preliminary orbital solution from the light curve and from four FEROS spectra reveals two similar components of around 1.5 M ⊙ orbiting with a period of 5.702 d. 相似文献
125.
《Limnologica》2021
Lake temperature responses to climate forcing are of interest on account of the important linkages between water temperature and ecosystem processes. This paper describes a new 1-dimensional (1D) numerical model code and its application to investigations of multi-scale linkages between the vertical temperature structure and meteorological forcing. UCLAKE is implemented as highly portable open-source software, based on computationally efficient algorithms, and able to resolve sub-daily (e.g., hourly) dynamics while retaining the efficiency to simulate multi-decadal time scales.A UCLAKE model is calibrated and validated against thermistor profile time series for a small upland lake in North Wales, UK. Some of the challenges in 1D model calibration are explored and a sensitivity analysis reveals a dependence of optimal parameter set values on water column depth and time. An exploratory 52-year hindcast simulation demonstrates the computational efficiency of UCLAKE for multi-decadal studies of trends in lake temperature that vary with depth. A supplementary application of UCLAKE to Windermere, in the English Lake District, demonstrates its performance for larger and deeper lakes. 相似文献
126.
127.
128.
为了满足海洋科研和工程开发工作对海洋环境进行直观模拟和表达的应用需求,本文运用MFC交互框架和OSG三维渲染引擎,研究节点访问器、回调机制、事件处理以及消息传递等三维交互关键技术,从地形模型构建、海水仿真、坐标映射以及场景剪裁等几个方面对海洋环境三维场景构建和渲染技术进行研究和开发,实现了界面友好的海洋环境三维交互场景,以便进一步对海洋环境特征和现象进行仿真和模拟。 相似文献
129.
Coupled 2D Hydrodynamic and Sediment Transport Modeling of Megaflood due to Glacier Dam-break in Altai Mountains,Southern Siberia 总被引:1,自引:1,他引:0
One of the largest known megafloods on earth resulted from a glacier dam-break,which occurred during the Late Quaternary in the Altai Mountains in Southern Siberia.Computational modeling is one of the viable approaches to enhancing the understanding of the flood events.The computational domain of this flood is over 9460 km2 and about 3.784 × 106 cells are involved as a 50 m × 50 m mesh is used,which necessitates a computationally efficient model.Here the Open MP(Open Multiprocessing) technique is adopted to parallelize the code of a coupled 2D hydrodynamic and sediment transport model.It is shown that the computational efficiency is enhanced by over 80% due to the parallelization.The floods over both fixed and mobile beds are well reproduced with specified discharge hydrographs at the dam site.Qualitatively,backwater effects during the flood are resolved at the bifurcation between the Chuja and Katun rivers.Quantitatively,the computed maximum stage and thalweg are physically consistent with the field data of the bars and deposits.The effects of sediment transport and morphological evolution on the flood are considerable.Sensitivity analyses indicate that the impact of the peak discharge is significant,whilst those of the Manningroughness,medium sediment size and shape of the inlet discharge hydrograph are marginal. 相似文献
130.