全文获取类型
收费全文 | 75篇 |
免费 | 11篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 8篇 |
地球物理 | 46篇 |
地质学 | 9篇 |
海洋学 | 9篇 |
综合类 | 2篇 |
自然地理 | 5篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 2篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有91条查询结果,搜索用时 15 毫秒
61.
Flume simulation of wave-induced release of internal dissolved nitrogen in Taihu Lake, China 总被引:1,自引:0,他引:1
A wave flume simulator was used to study internal nitrogen release from the surface sediment collected from Taihu Lake,China.Particulate nitrogen concentrations were positively correlated with the concentrations of suspended solids,primarily from surface erosion related to the shear stress and duration of wave action.In response to 4 cm-and 10 cm-high wave production representing waves generated in Taihu Lake by gentle and gusty winds,respectively,the mean dynamic release rate of ammonium(NH+4) from the sediment to the overlying water was 1×10-3 mg/(m2.s) and the NH4+ concentration in the overlying water increased by 0.016 mg/L,indicating that waves resulting from strong wind can induce the rapid release of dissolved nitrogen from Taihu Lake sediments.The decrease in interstitial NH+4 concentrations at all sediment depths was associated with an increase in NH4+ concentrations in the overlying water by 0.01 mg/L,showing that sediment below the eroded layer was the main source of internal nitrogen release.Changes in the interstitial dissolved oxygen and NH+4 concentrations showed that wave-induced pore water movement can greatly increase the diffusion rate,and that these effects can influence the sediment to a depth of at least 15 cm.Diffusion induced by pore water movement may be very important for the formation of an active sediment layer in Taihu Lake. 相似文献
62.
Impact of the simulation algorithm, magnitude of ergodic fluctuations and number of realizations on the spaces of uncertainty of flow properties 总被引:1,自引:1,他引:0
P. Goovaerts 《Stochastic Environmental Research and Risk Assessment (SERRA)》1999,13(3):161-182
Geostatistical simulation algorithms are routinely used to generate conditional realizations of the spatial distribution
of petrophysical properties, which are then fed into complex transfer functions, e.g. a flow simulator, to yield a distribution
of responses, such as the time to recover a given proportion of the oil. This latter distribution, often referred to as the
space of uncertainty, cannot be defined analytically because of the complexity (non-linearity) of transfer functions, but
it can be characterized algorithmically through the generation of many realizations. This paper compares the space of uncertainty
generated by four of the most commonly used algorithms: sequential Gaussian simulation, sequential indicator simulation, p-field simulation and simulated annealing. Conditional to 80 sample permeability values randomly drawn from an exhaustive
40×40 image, 100 realizations of the spatial distribution of permeability values are generated using each algorithm and fed
into a pressure solver and a flow simulator. Principal component analysis is used to display the sets of realizations into
the joint space of uncertainty of the response variables (effective permeability, times to reach 5% and 95% water cuts and
to recover 10% and 50% of the oil). The attenuation of ergodic fluctuations through a rank-preserving transform of permeability
values reduces substantially the extent of the space of uncertainty for sequential indicator simulation and p-field simulation, while improving the prediction of the response variable by the mean of the output distribution. Differences
between simulation algorithms are the most pronounced for long-term responses (95% water cut and 50% oil recovery), with sequential
Gaussian simulation yielding the most accurate prediction. In this example, utilizing more than 20 realizations generally
increases only slightly the size of the space of uncertainty. 相似文献
63.
室外风对高层建筑外保温层火灾发展的影响研究 总被引:1,自引:0,他引:1
近年来,由外墙保温材料引起的高层建筑火灾频繁发生,使得高层建筑室外火灾已经成为当下防火安全工程研究的热点议题。高层建筑外墙火灾受室外风影响较大,本研究采用CFD(Computational Fluid Dynamics)火灾模拟软件FDS,针对当前典型高层住宅建筑进行室外风作用下外保温材料火灾特性的模拟研究,分析了不同风向风速作用下外墙保温材料的火灾燃烧性能,研究了室外风对火灾烟气温度、运动速度、CO体积分数、可见度、火灾热释放速率等参数的影响。研究结果表明:室外风对火灾热释放速率等火灾作用参数有着较大影响,并存在一定的规律性。研究成果对未来高层节能建筑的防火设计施工具有一定的借鉴意义。 相似文献
64.
AREM模拟云参数与卫星观测的比较研究 总被引:4,自引:3,他引:1
数值模式模拟计算云量与卫星观测云量的定义不同, 难以进行定量比较, 从而限制了对云模拟误差的检验和修正.作者介绍了可把数值模式输出云参数转换成ISCCP卫星反演云参数的云模拟器, 并将其试用于AREM区域模式中, 定量分析了模拟云参数和ISCCP反演云参数的差异.结果表明, AREM模式可以再现中国东部冬季云的基本分布特征, 但与观测相比, 四川地区云量模拟偏大20%, 华东地区则偏小20%左右, 云量中心的云顶高度比ISCCP反演值偏低一个高度段, 云光学厚度偏大一个厚度段.模拟与观测云参数的定量比较, 为评估和改进模式性能提供了依据. 相似文献
65.
三自由度晃荡模拟装置及其模态分析 总被引:1,自引:0,他引:1
晃荡现象是海洋工程和船舶设计中值得关注的问题,它涉及到自由液面大幅度运动的一系列非线性问题,很难获得一个完全的理论解,相应的试验是主要方法,本文介绍三个自由度的模拟装置,并运用MSC/NASTRAN软件对该装置进行了结构有限元分析,重点在于模态分析。 相似文献
66.
Julien Boulange Farag Malhat Piyanuch Jaikaew Kazuki Nanko Hirozumi Watanabe 《国际泥沙研究》2019,34(1):38-47
A low-cost, simple to use portable rainfall simulator is developed for use over a 5 m^2 plot. The simulator is easy to transport and assemble in the field, thereby allowing for necessary experimental replicates to be done. It provides rainfall intensities of between 20 and 100 mm/h by changing the number and type of silicon nozzles used. The Christiansen coefficient of uniformities obtained in the field are appropriate and vary from 79 to 94% for rainfall intensities ranging from 30 to 70 mm/h. In addition, the median volumetric drop diameters measured for rainfall intensities of 30, 50, and 70 mm/h are in the lower range of that of natural rainfall and equal to 1.10 ± 0.08,1.69 ± 0.21, and 1.66 ± 0.20 mm, respectively. The velocities of the raindrops with diameters less than 1.2 mm reached terminal velocities, while raindrops less than 2.0 mm achieved velocities reasonably close to the terminal velocity of natural rainfall. Furthermore,the average time-specific kinetic energy(KET) for rainfall intensities of 30, 50, and 70 mm/h are 257.7,760.1, and 1645.2 J/m^2/h, respectively accounting for about 78.0 and 86.5% of the KET of natural rainfall for50 and 70 mm/h rainfall intensity, respectively. The applicability of the portable rainfall simulator for herbicide transport study is investigated using two herbicides(atrazine and metolachlor); herbicide losses in runoff and sediment samples are in the ranges reported in the literature. As a percentage of the amount of herbicide applied, 5.29% of atrazine and 2.15% of metolachlor are lost due to combined water and sediment runoff. The results show that the portable rainfall simulator can be effectively used in studying processes such as pesticide runoff, infiltration mechanisms, and sediment generation and transport at a field plot scale with an emphasis on how surface characteristics such as slope and soil properties affect these processes. 相似文献
67.
降雨冲刷对黄土公路边坡植物防护影响的试验研究 总被引:2,自引:0,他引:2
通过对裸露黄土公路边坡、厚层基材植草公路边坡、三维网植草公路边坡以及平台植树公路边坡的现场降雨冲刷试验,阐述了不同防护型式的公路黄土边坡在降雨条件下的坡面径流、含泥量以及坡面冲刷情况,得出了降雨对边坡坡面的侵蚀过程,首先是从雨滴直接打击土体开始,进而引起溅蚀,分散土粒,紧接着发生超渗径流造成坡面冲刷。以及对坡面破坏最大的是坡顶上方来水等重要结论。验证了坡面植物防护以及平台植树等防护方法可以有效降低降雨冲刷对坡面的侵蚀破坏,为黄土地区公路边坡植物防护的设计施工以提供了可靠的依据。 相似文献
68.
Earthquake simulator tests of a 1/6-scale nine-story reinforced concrete frame-wall model are described in the paper. The test results and associated numerical simulation are summarized and discussed. Based on the test data, a relationship between maximum inter-story drift and damage state is established. Equations of variation of structural characteristics (natural frequency and equivalent stiffness) with overall drifts are derived by data fitting, which can be used to estimate structural damage state if structural characteristics can be measured. A comparison of the analytical and experimental results show that both the commonly used equivalent beam and fiber element models can simulate the nonlinear seismic response of structures very well. Finally, conclusions associated with seismic design and damage evaluation of RC structures are presented. 相似文献
69.
70.