全文获取类型
收费全文 | 81篇 |
免费 | 8篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 7篇 |
地球物理 | 12篇 |
地质学 | 29篇 |
海洋学 | 4篇 |
天文学 | 1篇 |
综合类 | 3篇 |
自然地理 | 22篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 6篇 |
2012年 | 1篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 10篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有93条查询结果,搜索用时 31 毫秒
41.
江苏省工业废水排放与经济增长的动态关系 总被引:8,自引:0,他引:8
本文研究了1980~2004年江苏省工业废水排放与经济增长的动态关系,结果表明1980年以来江苏省工业废水排放量在波动中平缓增长,排放强度不断下降,主要来源于制造业和能源生产部门,南京市、苏南三市和苏中苏北九市的排放量大致各占排放总量的1/3。采用环境库兹涅茨曲线模型模拟了1980~1996年和1997~2004年工业废水排放量和人均GDP之间的关系,结果显示未来江苏省工业废水排放趋向于在经历较短时间的上升后逐渐下降。采用分解分析方法分析了三种效应在工业废水排放变化中的贡献率,结果表明广义技术效应、规模效应是影响工业废水排放的重要因素,但广义技术效应起到决定性的作用。 相似文献
42.
基于Weibull函数和Gamma函数的环境污染与经济增长的关系 总被引:4,自引:1,他引:3
环境库兹涅茨曲线是研究环境污染与经济增长之间关系的有效工具。传统的环境库兹涅茨曲线研究大多采用线性模型或对数线性模型,其在采用模型描述关系的问题上存在一定的不足。为克服这些不足,本文采用Weibull函数和Gamma函数形式的面板数据模型对中国29个省区1989~2005年四种环境污染指标人均排放量与人均收入之间的关系予以研究。结果表明Weibull函数和Gamma函数的面板数据模型拟合效果较好,且参数具有较好的解释能力;人均废水和人均SO2都随人均收入增加先上升后减少,在25000元附近出现结构转变点,而人均固体废弃物和人均废气随人均收入增加则呈现单调增加的变化趋势,没有出现结构转变点。 相似文献
43.
测量实习中的测量任务量的确定是关系到实习成败的关键因素,本文应用<心理学>的普遍原理并结合本校学生进行测量实习实际情况,通过<心理学>中关于注意、记忆、感知等思维的基本原理,以及对同学在不同时期时所学知识理解的问卷调查,并与教师完成任务量所用时间的比较.得到以教师所完成的工作量为参照,来探讨确定同学测量实习的最佳任务量的科学的方法.在教学实践中取得了良好的效果. 相似文献
44.
45.
Issues concerning what measures should be adopted to achieve a sustainable world with less carbon dioxide emission and in what magnitude should we reduce our emission have been on agenda in both international negotiations and countries’ policy making aimed at coping with potential global climate change. These issues cannot be easily addressed unless comprehensive understanding about the countries’ status quo as well as historical relationship between economic development and carbon dioxide emission are gained. In this paper, we examine the historical relationship between economic development and carbon dioxide emission; the ex ante restrictions on function forms and the poorly handled robustness issues rife in economics literature are synthetically addressed. Evidence from recent four decades indicates that per capita carbon dioxide emission first significantly and monotonously increase at low income level and flattens after per capita income reaches at about 22,000 $ (2005 constant price). We perform various robustness checks by employing different data sources, different model specifications and different econometric estimates. The captured development–emission relationship is robust. Our empirical results indicate factors such as urbanization, population density, trade, energy mix and economic environment impact the absolute level of carbon dioxide emission not the overall income elasticity structure of carbon dioxide emission. 相似文献
46.
47.
This paper studies one of the most important problems of dry countries that are confronted with water deficit and the competition of rivals to allocate water. Some common methods have been investigated for computing the minimum water requirement to save a river's biological activity. After a discussion of the currently used method in Iran (the Tenant Method), the application of some other methods, which are known as Hydraulic and Hydrological Methods, is illustrated. The case study is a river in the northern part of Iran and this research addresses the critical situation of this river in near future regarding the planned anthropogenic alteration and its consequences. It has been shown that the application of environmental water allocation methods that have no background in a region could be misleading. The first proposed method is the Texas Method, in which flexibility in water allocation helps to develop an integrated river management paradigm in the study area. The second preferred method is a Hydraulic Method, by which the implementation of morphological parameters or flow geometrical properties could sustain physical habitat within an acceptable range in terms of depth, width, velocity, and bed shear stress. In the case study, the Maximum Curvature Method was superior to the Slope Method. The investigation revealed that using a widely recommended slope of 1 for the discharge‐wetted perimeter function can lead to an overestimated and unacceptable discharge. The Tenant Method in respect to minimum environmental flow requirement yielded the weakest result, and it has been illustrated that its application might impose irrecoverable shock to the ecosystem. The Flow Duration Curve Method (the Q95 Method), in spite of its subjectivity, showed more compatibility with the river's condition in comparison with the Tenant Method. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
48.
This paper proposes an automatic method for registering terrestrial laser scans in terms of robustness and accuracy. The proposed method uses spatial curves as matching primitives to overcome the limitations of registration methods based on points, lines, or patches as primitives. These methods often have difficulty finding correspondences between the scanned point clouds of freeform surfaces (e.g., statues, cultural heritage). The proposed method first clusters visually prominent points selected according to their associated geometric curvatures to extract crest lines which describe the shape characteristics of point clouds. Second, a deformation energy model is proposed to measure the shape similarity of these crest lines to select the correct matching-curve pairs. Based on these pairs, good initial orientation parameters can be obtained, resulting in fine registration. Experiments were undertaken to evaluate the robustness and accuracy of the proposed method, demonstrating a reliable and stable solution for accurately registering complex scenes without good initial alignment. 相似文献
49.
提出基于曲线弯曲识别的等高线簇结构化方法,实现等高线簇中所蕴含的地形结构的提取。首先对基于Delau-nay三角网的曲线弯曲识别方法进行改进,包括伪弯曲的合并、弯曲基点的调整及小弯曲的删除方法;基于此,建立弯曲间的层次嵌套关系及平行相邻关系,实现曲线弯曲的识别方法;然后,根据单条等高线间的空间关系,对弯曲类型进行判断;结合曲线间的空间邻近度计算方法,将等高线簇中的成组弯曲进行提取;最后完成了地形结构的识别,实现了等高线簇的结构化。该方法不仅对地形中的山谷进行提取,并且提取出了其对称结构即山脊。试验结果与水系叠置显示,所提取出的地形结构基本合理,证明了该方法的有效性。 相似文献
50.
Abstract The objective of this study is to develop a Modified Rational Equation (MoRE) that combines the advantages of the Rational Equation (e.g. simplicity and global acceptance) and those of the standard US Department of Agriculture (USDA) Soil Conservation Service (SCS) curve number (CN) method (e.g. easy parameterization and extensive verification across the world). Herein, the hypothesis is that the MoRE is more accurate, consistent and robust than the SCS-CN method and its improved versions in predicting runoff in watersheds with limited data. The MoRE was designed to have a simple structure that is described by four intrinsic parameters: CN, permanent wilting point, field capacity and saturation soil moisture, and does not include initial abstraction as a variable. An evaluation of 77 USDA small agricultural watersheds indicated that CN of the MoRE has different physical meanings from CN of the SCS-CN method. The MoRE (mean Nash-Sutcliffe coefficient, E > 0.73) performed better than the SCS-CN (mean E < 0.32) and the four improved models (mean E < 0.56) in reproducing the runoff of the study watersheds. Performance of all six models varied greatly between watersheds, as well as between events, but was independent of watershed drainage area. However, the model performances tend to be better for watersheds and/or events with a runoff-to-rainfall ratio of between 0.1 and 0.3 than for those with a ratio outside this range. The MoRE has the most consistent and robust performance. Editor D. Koutsoyiannis; Associate editor I. Nalbantis Citation Wang, X., Liu, T., and Yang, W., 2012. Development of a robust runoff-prediction model by fusing the rational equation and a modified SCS-CN method. Hydrological Sciences Journal, 57 (6), 1118–1140. 相似文献