全文获取类型
收费全文 | 875篇 |
免费 | 83篇 |
国内免费 | 95篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 124篇 |
地球物理 | 233篇 |
地质学 | 482篇 |
海洋学 | 108篇 |
综合类 | 26篇 |
自然地理 | 69篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 19篇 |
2021年 | 25篇 |
2020年 | 23篇 |
2019年 | 25篇 |
2018年 | 18篇 |
2017年 | 28篇 |
2016年 | 38篇 |
2015年 | 32篇 |
2014年 | 50篇 |
2013年 | 64篇 |
2012年 | 50篇 |
2011年 | 58篇 |
2010年 | 44篇 |
2009年 | 62篇 |
2008年 | 77篇 |
2007年 | 69篇 |
2006年 | 54篇 |
2005年 | 44篇 |
2004年 | 27篇 |
2003年 | 19篇 |
2002年 | 31篇 |
2001年 | 22篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 20篇 |
1996年 | 19篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1053条查询结果,搜索用时 15 毫秒
21.
There is widespread acceptance regarding the need to transition towards more sustainable urban water practices. Supporting such a transition requires new governance frameworks that can accommodate complexity and uncertainty, and organisational cultures that embrace experimentation and learning. This empirically focused research paper examines how eleven, alternative local-scale experiments were initiated while operating in an unsympathetic regime. Furthermore, the perceptions of more than 150 urban water practitioners across Australia are presented, regarding the importance of and difficulty in undertaking experimentation in the urban water sector, and the necessary mechanisms for influencing a step change to sustainable urban water management practices. Interviewees revealed perceived limitations in experimenting with new technologies and practices when operating within a hierarchical and market-based governance paradigm. Also, industry conservatism and the dominant risk-based management approach both operate as significant constraints to promoting an experimentation culture, and are closely related to concerns about public health and financial implications. Overall, the research highlights the Australian urban water sector is willing to embrace learning-by-doing; however, a stronger emphasis on promoting an organisational and industry-wide culture of experimentation and learning is required. Policy implications for future water governance are discussed. 相似文献
22.
23.
Risk analysis and appraisal of the benefits of structural flood risk management measures such as embankments is well established. Here, a method to quantify, over extended timescales, the effectiveness of non-structural measures such as land use spatial planning, insurance and flood resilient construction is presented. The integrated approach couples socio-economic and climate change scenarios with long term land use modelling and flood risk analysis to generate maps and time series of expected annual damages. The analysis has been applied on a case study in the Thames Estuary in the UK. Stakeholders helped develop a number of scenarios that might lead to substantial changes in existing planning and insurance policies in the UK. The effectiveness of these changes was analysed and showed the substantial benefits in terms of reduction of future flood risks that are achievable with changes in planning policy, financial incentives and resilient property construction in the floodplain. Moreover, the reward can be increased through earlier action. Subsequently, the benefits of a range of policies are explored under the UK Foresight socio-economic scenarios. Different structural and non structural flood management interventions are tested and the results demonstrate that despite the potential for large increases in flood risk in the Thames Estuary, in all scenarios substantial flood risk reductions are possible. The effectiveness of non-structural measures is however sensitive to socio-economic changes and governance arrangements. The analysis described here will help to identify portfolios of non-structural and structural options that are robust to uncertainties. 相似文献
24.
1996年以来,黑龙江省草地螟第三暴发周期持续至今,危害日益加重。以1959—2008年黑龙江省28个国家基本站气象资料以及草地螟暴发期等资料为基础,分析了黑龙江省草地第三暴发周期的气候特征及风险概率。结果表明:近50 a来,黑龙江省年平均气温、年平均最低气温呈显著的上升趋势,通过0.001显著性检验,气温在1988年前后出现突变。其他要素如降水量、降水日数、风速和日照时数均呈减少趋势,但只有年日照时数和年平均风速的减少趋势通过了显著性检验。哈尔滨草地螟始发日期与同期平均气温、日最高气温、最低气温、最小相对湿度关系密切,本地越冬虫源春季羽化对气温、相对湿度敏感性较高;同时,始见日期与最大风速的风向相关较为密切,可能是由于外地虫源对风向敏感性较高。通过对黑龙江省草地螟高峰期首日的风险概率分析,得出草地螟高峰期出现在5月最后一个候的风险概率为23.6%;出现在6月上旬的风险概率为36.6%;出现在6月中旬的风险概率为24.0%;出现在6月下旬的风险概率为14.4%。 相似文献
25.
26.
27.
28.
29.
Obesity is a serious public health problem in the United States. It is important to estimate obesity prevalence at the local level to target programmatic and policy interventions. It is challenging, however, to obtain local estimates of obesity prevalence because national health surveys such as the Centers for Disease Control and Prevention (CDC) Behavioral Risk Factor Surveillance System (BRFSS) are not designed to produce direct estimates at the local levels (e.g. census tracts) due to small population samples and the need to preserve individual confidentiality. In this study we address the problem of estimating local obesity prevalence rates by implementing a spatial microsimulation modeling technique to proportionally replicate the demographic characteristics of BRFSS respondents to census tract populations in metropolitan Detroit. Obesity prevalence rates are examined for high and low spatial clusters and studied in relation to the U.S. Department of Agriculture's (USDA) measures of low-income neighborhoods and local food deserts and CDC's measure of healthy and less healthy food environments currently used to target obesity reduction initiatives. This study found that obesity prevalence was largely clustered in the City of Detroit extending north into contiguous suburbs. The spatial patterns of highest obesity prevalence tracts were most similarly aligned with USDA-defined low-income tracts and CDC's less healthy food tracts. The locations of USDA's food desert tracts rarely overlapped with the highest obesity prevalence tracts. This study demonstrated a new methodology by which to assess local areas in need of future obesity interventions. 相似文献
30.
Social capital can enhance community resilience to environmental change. Productive and trusted relations among social actors and effectual social norms can help local residents share resources, information and risks. The main objective of our study is to understand the ways in which social attributes and risk considerations influence adoption of resilient economic measures by individuals for reducing potential losses due to catastrophic rainstorm and flooding. This article provides evidence from China on how social capital contributes to anticipatory adaptation to environmental change. The inquiry is based on structured interviews with local residents of Tianjin, a flood-prone port city in China, and a standard regression analysis. Findings show that the intention to make preparation increases with the levels of social expectation, social relationship, and institutional trust. Perceived risk and damage experience, however, have no significant impacts. This suggests that building social capacity and trust will be more effective in enhancing community resilience than merely increasing awareness of hazard risks. We call for greater efforts on strengthening the capacity of formal and informal communal institutions. The structural changes required, however, are challenging. 相似文献