全文获取类型
收费全文 | 935篇 |
免费 | 41篇 |
国内免费 | 43篇 |
专业分类
测绘学 | 256篇 |
大气科学 | 50篇 |
地球物理 | 65篇 |
地质学 | 146篇 |
海洋学 | 68篇 |
天文学 | 8篇 |
综合类 | 87篇 |
自然地理 | 339篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 45篇 |
2021年 | 44篇 |
2020年 | 50篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2017年 | 46篇 |
2016年 | 44篇 |
2015年 | 34篇 |
2014年 | 50篇 |
2013年 | 70篇 |
2012年 | 34篇 |
2011年 | 36篇 |
2010年 | 34篇 |
2009年 | 21篇 |
2008年 | 48篇 |
2007年 | 44篇 |
2006年 | 36篇 |
2005年 | 47篇 |
2004年 | 36篇 |
2003年 | 37篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 35篇 |
1999年 | 23篇 |
1998年 | 18篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1019条查询结果,搜索用时 12 毫秒
31.
32.
British Columbia's current approach to monitoring salmon aquaculture waste is disconnected from political and legal trends towards the recognition of Aboriginal rights in Canada. Drawing on insights from collaborative monitoring in northern Canada and interviews with 23 Kwakwaka’wakw clam-diggers and cultural specialists (2006–2007), preliminary directions for integrating First Nations’ values, knowledge and stewardship practices into marine environmental monitoring are identified. Kwakwaka’wakw monitoring practices include the use of qualitative individual, community and population scale indicators and the integration of traditional knowledge as baseline data about the healthy conditions of traditional food resources. 相似文献
33.
34.
????Ω???????????????????????????????ò???????????????????????????????? ???????????????????????Ω?????????????????????????????????????????????????????????????÷????????????????????????????з?????????? 相似文献
35.
利用CitesSpace软件对1997-2017年DMSP/OLS夜间灯光数据进行知识图谱分析,梳理国内外研究热点与演化历史,发掘研究难点,为后来研究者提供方向。本文选取Web of Science 核心数据集数据库收录的文献,进行合著特征分析、关键词共现分析和文献共被引分析。结果表明:① 夜间灯光数据相关研究最活跃的国家、机构和作者分别是美国、中国科学院和Elvidge;② 社会经济条件估计(人口、人口密度和电力)和城市扩展变化监测一直是国内外研究的热点和前沿;③ 目前的研究难点是如何减少灯光溢出效应以及灯光过饱和现象对研究精度的影响;④ 研究学科交叉性强,涉及地理学、测绘科学与技术、应用经济学、社会学等领域。因此,未来的研究趋势主要表现在数据处理方法的优化、研究领域的拓展以及深化已有研究成果3个方面。 相似文献
36.
Application of participatory principles to investigation of the natural world: An example from Chile
Participatory research in environmental and natural resources-related fields is premised on many of the same notions that underlie participatory processes in decision making. This study examines one instance of participatory research to assess the extent to which the documented benefits of participatory decision-making hold up in the context of research. A survey of Chilean shell-fishers engaged in research with marine biologists assesses the relationships between four variables: fishers’ participation in research, fishers’ opinions of biologists, fishers’ trust in biologists, and fishers’ acquisition of knowledge from biologists. Results illuminate the multidimensionality of these variables and suggest that complex interrelationships between them make the benefits of participatory research more nuanced than those reported for participatory decision-making. For instance, participatory research may provide low benefits when participatory research outcomes differ little from those produced solely by scientists. In addition, high-cost scenarios may result when outcomes of participatory research are inferior to those produced solely by scientists. A third downside may result when participation leads participants to increase their deference to scientific knowledge, thereby defeating the corroborative purpose of their participation. A fourth effect may occur when increased trust by in scientists results from participation, decreasing participants’ perceived need to take part in research. 相似文献
37.
Understanding how science, technology and innovation can best help to accelerate progress in achieving sustainable development remains a grand challenge for researchers and practitioners. In the context of the global consultation process for preparing a post-2015 Sustainable Development Agenda, various science-based actor networks have emerged, aiming to translate research into political decision-making and to inform transformations towards sustainability. Over the last years, these networks seem to have taken an ever-growing role in structuring the science-policy interface in global sustainability governance. The question arises, however, how they understand and organize ‘scientific knowledge integration’ in sustainability politics.This study offers a structured comparison of twelve global science-based actor networks engaged in the implementation of the Sustainable Development Goals. It shows that these networks use two types of strategies to foster scientific knowledge integration in sustainability governance. A new framework emerges, in which each strategy corresponds to two main approaches of scientific knowledge integration: The entrepreneurial strategy generally seeks to advance advice-oriented and solution-oriented knowledge processes, while assessment-oriented and learning-oriented processes in scientific knowledge integration are mainly promoted through a mediating strategy. 相似文献
38.
Knowledge representation structure and reasoning processes are very important issues in the knowledge-based approach of integrating multiple spatial data sets for resource exploration. An object-oriented knowledge representation structure and corresponding reasoning processes are formulated and tested in this research on the knowledge-based approach of integrating spatial exploration data. The map-based prototype expert system developed in this study has self-contained knowledge representation structure and inference mechanisms. It is important to distinguish between lack of information and information providing negative evidence for a map-based system because the spatial distribution of data sets are uneven in most cases. Error and uncertainty estimation is also an important component of any production expert system. The uncertainty propagation mechanisms developed here work well for this type of integrated exploration problem. Evidential bellef function theory provides a natural theoretical basis for representing and integrating spatially uneven geophysical and geological information. The prototype system is tested using real mineral exploration data sets from the Snow Lake area, northern Manitoba, Canada. The test results outline the favorable exploration areas successfully and show the effectiveness of the knowledge representation structure and inference mechanisms for the knowledge-based approach. 相似文献
39.
This work reports on a method using fuzzy membership functions to construct an aggregated interaction matrix in which the summation of variables is scaled according to the way rainfall and soil variables affect water availability to plants and hence influence rangeland productivity. Aggregation of the variables gives a comprehensive value which can be used to predict production. The model increases the predicability of production to 81% compared to models using rainfall alone and a multiplicative parametric one which give predictibilities of 61 and 76% respectively. The results showed that (1) the importance of rainfall in determining production was most important at lower rainfalls i.e. <350 mm; (2) soil texture and particularly slope were important through out the rainfall range (149–700 mm) investigated; and (3) soil depth was only important at the higher >350 mm rainfalls. The aggregated interaction matrix gives a measure of land productive capability. 相似文献
40.