全文获取类型
| 收费全文 | 108篇 |
| 免费 | 6篇 |
| 国内免费 | 8篇 |
专业分类
| 测绘学 | 4篇 |
| 大气科学 | 2篇 |
| 地球物理 | 37篇 |
| 地质学 | 17篇 |
| 海洋学 | 57篇 |
| 综合类 | 1篇 |
| 自然地理 | 4篇 |
出版年
| 2022年 | 1篇 |
| 2020年 | 5篇 |
| 2019年 | 2篇 |
| 2018年 | 4篇 |
| 2016年 | 2篇 |
| 2014年 | 6篇 |
| 2013年 | 11篇 |
| 2012年 | 5篇 |
| 2011年 | 5篇 |
| 2010年 | 6篇 |
| 2009年 | 8篇 |
| 2007年 | 11篇 |
| 2006年 | 6篇 |
| 2005年 | 10篇 |
| 2004年 | 3篇 |
| 2003年 | 3篇 |
| 2002年 | 4篇 |
| 2001年 | 4篇 |
| 2000年 | 6篇 |
| 1999年 | 4篇 |
| 1998年 | 1篇 |
| 1997年 | 3篇 |
| 1996年 | 3篇 |
| 1994年 | 1篇 |
| 1991年 | 1篇 |
| 1990年 | 3篇 |
| 1987年 | 1篇 |
| 1985年 | 1篇 |
| 1984年 | 1篇 |
| 1977年 | 1篇 |
排序方式： 共有122条查询结果，搜索用时 593 毫秒
101.
以连云港羊窝头抛泥区为研究区域 ,对疏浚工程中产生的大量疏浚弃土倾倒入海后 ,所产生弃土的堆积—流失—扩散过程以及海域环境效应 ,进行了现场观测和计算 ,并从物理、化学和生物 3个方面对海区的水质、底质和生态环境的影响作出客观分析。认为疏浚的环境效应主要取决于疏浚弃土本身的受污染程度 ,而对海域环境的影响 ,则主要是弃土扩散所造成的海水中悬浮沙量增加引起水质浑浊度的增高的物理性影响 ,同时由于弃土中大量的粘粒和胶粒物质具有吸附海水中重金属和有机物等污染物质的能力 ,有利于水质和生态环境的改善 ,因而对各类海洋生物生存环境的影响是十分轻微的。 相似文献
102.
103.
104.
强人类活动(如航道疏浚)和自然气候变化(如海平面上升)对近岸河口环境不同影响的辨识是目前河口海岸学研究的热点和难点问题。在地形概化和动力简化条件下, 解析模型能够快速辨识强人类活动和自然气候变化对河口环境的影响, 它是探讨河口动力过程对外界干扰的响应机制的重要工具。本文基于前人对葡萄牙Guadiana河口不同分潮之间非线性相互作用的研究, 采用一维水动力解析模型探讨河口不同分潮潮波传播过程对水深变化(模拟航道疏浚和河道淤积过程)的响应机制。研究结果表明: 平均水深$\overline{h}$的变化影响无量纲河口地形参数γ和摩擦参数χ, 进一步影响河口动力参数包括潮波振幅参数ζ、流速振幅参数μ、波速参数λ、潮波振幅增大/衰减率参数δ以及流速与水位之间的相位差?等; 平均水深变化对河口中下游段(x=0~60km)的潮汐动力影响较大, 而对河口上游段(x=60~78km)影响较弱; 主要半日分潮(M2、S2、N2)对水深变化的响应略大于全日分潮(K1、O1); 航道疏浚幅度小于2m时, 对河口潮汐动力格局影响不大, 而当疏浚幅度大于2m时, 将对河口潮汐动力格局及水环境(如盐水入侵等)产生较大影响; 河道淤积将导致潮汐动力减弱, 流速振幅、潮波振幅及传播速度减小, 流速和水位之间的相位差也减小。 相似文献
105.
Field sampling of the dissolved and particulate material field downstream of a large volume bucket dredge operating in the lower Thames River estuary near New London, Connecticut, was conducted in order to examine the magnitude and character of the dredge-induced resuspension. These data indicate that large amounts of dissolved phosphate, ammonia, silica, manganese, copper and particulate materials are released into the water column, whereas cadmium concentrations were unaffected. Concentrations in the vicinity of the dredge exceed background levels by two to nine times for the dissolved materials and by two orders of magnitude for particulates. During the ebb cycle, downstream material concentrations decrease rapidly to background within approximately 180 m for dissolved materials and 700 m for particulates.Two mechanisms were found to control the distribution of materials downstream of the dredge: (a) physical transport, including advection, turbulent mixing and diffusion, and (b) geochemical processes (i.e. adsorption, desorption, precipitation, dissolution, etc.). The concentration of dissolved materials downstream of the dredge decrease at a first order exponential rate. The downstream distribution of the dissolved ammonia and silica was found to be consistent with the reactivity experiments (Figure 8) which predicted that PO4 would undergo a decay in concentration in the presence of suspended sediments. Absorption of phosphate onto suspended sediments and gravitational settling of the suspended particulates were the processes. Manganese and copper underwent a dual transformation which involved an initial dissolution, followed by flocculation and possible coprecipitation as MnO2. Cadmium concentrations in the water column were unaffected by the dredging process due to low pore water concentrations.The observed spatial distribution indicates that dredge-induced injection of dissolved and particulate materials is primarily a near field phenomenon producing relatively minor variations as compared to those caused by naturally occurring storm events. These latter systems have been shown (Tramontano, 1978; Bohlen et al., 1979) to produce estuary-wide variations in suspended materials, PO4 and NH4 concentrations increasing the mass of materials in suspension by at least a factor of two. This increase in total suspended load, PO4 and NH4, is nearly an order of magnitude larger than that produced by the dredge. 相似文献
106.
107.
就"区域沉积物管理"(简称RSM) 概念与方法进行了系统论述,以厦门地区为例阐述了 RSM 研究的必要性和重要性,并对如何应用区域沉积管理来处理海岸冲刷、淤积与港口码头建设过程中可能遇到的问题进行了深入浅出的讨论,同时,提出了发展 RSM 的战略构想与框架。 相似文献
108.
109.
In order to examine the effectiveness of engineering protection against localized scour in frontof the south groin-group of the Yangtze Estuary Waterway Improvement Project,Phase I,an undistort-ed physical model on a geometric scale of 1:250 is built in this study,covering two groins and their adacentestuarine areas.By use of rinsing fix-bed model as well as localized mobile-bed model,the experiment isundertaken under bi-directional steady flow.According to the experimental results,waterway dredgingleads to the increase in steram velocity,the increase being larger during the ebb than during the flood.Con-struction of the upstream groin has some influence on the flow patterns near the downstream groin.Local-ized scour in front of the groin-heads is controlled mainly by ebb flow.In the case of a riverbed composedentirely of silt,the depths of localized scour in front of the two groin-heads are 27 m and 29 m,respectively.In reality,the underneath sediment of the prototype riverbed is clay whose threshold ve 相似文献
110.
湖泊底泥疏浚环境效应：Ⅰ.内源磷释放控制作用 总被引：12，自引：5，他引：7
通过为期一年的疏浚模拟试验,在试验室培养疏浚与对照柱样研究了底泥疏浚对内源磷释放的控制效果,结果发现,疏浚表层30cm能够有效的消减沉积物中不同形态磷含量与孔隙水中PO43-p含量,在一年的试验周期内,疏浚和对照柱沉积物-水界面的PO43-P通量分别为-143.8至14.4与-237.3至3047.6μg(m2·d),疏浚柱沉积物-水界面的磷通量总体上低于未疏浚对照的磷通量,尤其是在温度较高的月份,从2006年3-10月疏浚柱沉积物-水界面磷释放通量显著低于未疏浚对照柱,疏浚沉积物的磷的释放潜力低于未疏浚对照沉积物,研究结果表明,在外源磷得到有效控制的前提下,底泥疏浚是消减研究区内源磷负荷有效的技术手段. 相似文献