全文获取类型
收费全文 | 59篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 6篇 |
地球物理 | 13篇 |
地质学 | 15篇 |
海洋学 | 8篇 |
天文学 | 1篇 |
综合类 | 6篇 |
自然地理 | 8篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2017年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2009年 | 1篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有63条查询结果,搜索用时 15 毫秒
31.
为了满足矿山企业对储量简测和管理工作的需要,以无锡地区小型露采矿山为基础,综合考虑全省其他地区同类矿山的特征,研制开发了一套在省内较为实用的小型露采矿山储量计算系统软件(第一版)。该系统以DOS为平台,FORTRAN语言开发,对硬件设备要求低,适应性和针对性强。在无锡地区的实际使用说明,该储量计算系统具有计算快速准确,可快速滚动计算等优点,是矿山储量信息化管理的一个较好的工具。 相似文献
32.
33.
全球环境变化和地球科学面临的新任务 总被引:4,自引:0,他引:4
阐述了地球科学与可持续发展的关系;讨论了当今地球面临的三大环境问题,并介绍了美国1997年全球变化研究计划概况,全球变化研究对于认识、评价和预测全球环境变化、人类健康、生态系统和经济持续发展是十分重要的,为了满足社会的需要,地球科学正面临着4方面的重大挑战。 相似文献
34.
Springs and seeps occur in the spaces around Po Hing Fong Street in the Mid‐Levels area, Hong Kong. Most of the springs occur through the drainage weepholes on retaining walls at the street. This paper first examines the geology and history of the springs. The paper then reports the findings from a 1‐year comprehensive spring monitoring programme. The temporal variations of flow rate, physiochemical parameters and hydrochemistry of the springs are discussed. The average temperatures of the springs were close to the mean air temperature, although there was a systematic lag time of 40 to 50 days between the peak air temperature and highest water temperatures. Spring waters from two rows of weepholes in the retaining wall showed significantly different physical and hydrochemical responses to the changes in rainfall and temperature, though their vertical distance is only about 1 m. The results suggest that water from the upper row of weepholes may represent a recharge source that is shallow or close to the spring outlets, whereas that from the lower row of weepholes may represent a recharge source that is much deeper or further up the hill. Although the spring flows increased rapidly after rainstorms, analysis of the total dissolved solids showed a delayed response to rainstorm events. The concentration of individual ions in the spring water varied in a unique way in response to rainstorm events. It is clear that the presence of underground man‐made drainage systems and the leakage from water mains in the study area may add complexity to the solute responses and transport mechanisms. Further studies are required to constrain the impacts of these man‐made structures on the hydrogeology of the springs. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
35.
36.
In the territory of Altomonte, a village located in Calabria, in the Southern part of Italy, a new thermoelectrical station
is under construction. This work involved major earthworks which regarded new excavated slopes. In order to protect soil from
erosion due to rainfall and runoff and also in order to prevent superficial soil instability, it was decided to plant four
different species of perennial “gramineae” plants (Eragrass, Elygrass, Pangrass and Vetiver) characterised by deep roots.
Works began in November 2002 and ended in May 2003, a period marked by very different climate and meteorological conditions,
varying from exceptionally rainy and cold winter to warm and dry spring months. The paper describes the different stages of
the project and the monitoring programme for the following months. The extension of the work and the use of four different
kinds of vegetation made periodic inspections of the entire site appropriate. Two in situ investigations, respectively performed
in August 2003 and in November 2003, are outlined. The aim of these surveys was to confirm the success of the work by verifying
the growth of the plants and roots. The principal monitored parameters were the percentage of sprouted plants, the height
of the foliage and the depth of roots. The investigations showed good results, keeping in mind the very difficult climatic
conditions and the extreme poor fertility of the topsoil laid down upon the clay layer: in particular, high survival rate
were measured over the entire area of the works and the root systems have developed sufficiently to grow through the upper
topsoil layer (0.2–0.3 m) into the underlying clay layer. In March 2004, a sampling programme was undertaken on the same site.
Direct shear tests were carried out in the laboratory in order to evaluate the increase in shear strength of the rooted soil
mass. The research involved the recovery of three undisturbed samples of soil with roots for each of the four types of “gramineae”
plants and three undisturbed samples constituted only of soil, from the surface to a depth of 1.0 m. The tests were performed
in a large direct shear apparatus on 200 mm diameter samples. The test results allowed to evaluate the roots’ contribution
of the different gramineous species and to underline the direct correlation between the increase in soil shear strength and
the root tensile strengths. In particular, an increase in cohesion ranging between 2 kPa and 15 kPa was recorded, according
to the different species: the maximum values of increase in shear strength were reached by Vetiver roots, which are also characterised
by the highest tensile strength. 相似文献
37.
In 2001, the four global change research programmes ‘urgently’ called for ‘an ethical framework for global stewardship and strategies for Earth System management’. Yet this notion of ‘earth system management’ remains vaguely defined: It is too elusive for natural scientists, and too ambitious or too normative for social scientists. In this article, I develop an alternative concept that is better grounded in social science theory: ‘earth system governance’. I introduce, first, the concept of earth system governance as a new social phenomenon, a political programme and a crosscutting theme of research in the field of global environmental change. I then sketch the five key problem structures that complicate earth system governance, and derive from these four overarching principles for earth system governance as political practice, namely credibility, stability, adaptiveness, and inclusiveness. In the last part of the article, I identify five research and governance challenges that lie at the core of earth system governance as a crosscutting theme in global change research. These are the problems of the overall architecture of earth system governance, of agency beyond the state, of the adaptiveness of governance mechanisms and of their accountability and legitimacy, and of the modes of allocation in earth system governance—in short, the five A's of earth system governance research. 相似文献
38.
刘文宝 《大地测量与地球动力学》1992,(4)
基于动态平差模型,应用多指标动态规划工具建立了两种同时顾及精度,费用和可靠性准则的二类优化设计模型。通过一个实例阐明了进行动态网复测权整体设计的一般方法。 相似文献
39.
气象台站规划必须适应气象业务及其现代化发展需要,同时也应满足职工生活要求 。从这一角度出发,阐明了分析规划时应考虑的因素,制定了台站基本建设规划的思路和方 向,提出了宜采取的办法。 相似文献
40.