全文获取类型
收费全文 | 1901篇 |
免费 | 51篇 |
国内免费 | 20篇 |
专业分类
安全科学 | 129篇 |
废物处理 | 82篇 |
环保管理 | 445篇 |
综合类 | 209篇 |
基础理论 | 490篇 |
环境理论 | 2篇 |
污染及防治 | 387篇 |
评价与监测 | 124篇 |
社会与环境 | 72篇 |
灾害及防治 | 32篇 |
出版年
2023年 | 15篇 |
2022年 | 24篇 |
2021年 | 22篇 |
2020年 | 26篇 |
2019年 | 24篇 |
2018年 | 47篇 |
2017年 | 61篇 |
2016年 | 67篇 |
2015年 | 64篇 |
2014年 | 60篇 |
2013年 | 131篇 |
2012年 | 86篇 |
2011年 | 155篇 |
2010年 | 100篇 |
2009年 | 88篇 |
2008年 | 114篇 |
2007年 | 125篇 |
2006年 | 120篇 |
2005年 | 72篇 |
2004年 | 71篇 |
2003年 | 71篇 |
2002年 | 59篇 |
2001年 | 40篇 |
2000年 | 28篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 15篇 |
1996年 | 25篇 |
1995年 | 16篇 |
1994年 | 20篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1969年 | 3篇 |
1937年 | 2篇 |
1936年 | 2篇 |
1935年 | 3篇 |
1926年 | 2篇 |
排序方式: 共有1972条查询结果,搜索用时 15 毫秒
631.
Direct and interactive effects of enemies and mutualists on plant performance: a meta-analysis 总被引:5,自引:0,他引:5
Morris WF Hufbauer RA Agrawal AA Bever JD Borowicz VA Gilbert GS Maron JL Mitchell CE Parker IM Power AG Torchin ME Vázquez DP 《Ecology》2007,88(4):1021-1029
Plants engage in multiple, simultaneous interactions with other species; some (enemies) reduce and others (mutualists) enhance plant performance. Moreover, effects of different species may not be independent of one another; for example, enemies may compete, reducing their negative impact on a plant. The magnitudes of positive and negative effects, as well as the frequency of interactive effects and whether they tend to enhance or depress plant performance, have never been comprehensively assessed across the many published studies on plant-enemy and plant-mutualist interactions. We performed a meta-analysis of experiments in which two enemies, two mutualists, or an enemy and a mutualist were manipulated factorially. Specifically, we performed a factorial meta-analysis using the log response ratio. We found that the magnitude of (negative) enemy effects was greater than that of (positive) mutualist effects in isolation, but in the presence of other species, the two effects were of comparable magnitude. Hence studies evaluating single-species effects of mutualists may underestimate the true effects found in natural settings, where multiple interactions are the norm and indirect effects are possible. Enemies did not on average influence the effects on plant performance of other enemies, nor did mutualists influence the effects of mutualists. However, these averages mask significant and large, but positive or negative, interactions in individual studies. In contrast, mutualists ameliorated the negative effects of enemies in a manner that benefited plants; this overall effect was driven by interactions between pathogens and belowground mutualists (bacteria and mycorrhizal fungi). The high frequency of significant interactive effects suggests a widespread potential for diffuse rather than pairwise coevolutionary interactions between plants and their enemies and mutualists. Pollinators and mycorrhizal fungi enhanced plant performance more than did bacterial mutualists. In the greenhouse (but not the field), pathogens reduced plant performance more than did herbivores, pathogens were more damaging to herbaceous than to woody plants, and herbivores were more damaging to crop than to non-crop plants (suggesting evolutionary change in plants or herbivores following crop domestication). We discuss how observed differences in effect size might be confounded with methodological differences among studies. 相似文献
632.
Floodplains are among the world's most threatened ecosystems due to the pervasiveness of dams, levee systems, and other modifications to rivers. Few unaltered floodplains remain where we may examine their dynamics over decadal time scales. Our study provides a detailed examination of landscape change over a 60-year period (1945-2004) on the Nyack floodplain of the Middle Fork of the Flathead River, a free-flowing, gravel-bed river in northwest Montana, USA. We used historical aerial photographs and airborne and satellite imagery to delineate habitats (i.e., mature forest, regenerative forest, water, cobble) within the floodplain. We related changes in the distribution and size of these habitats to hydrologic disturbance and regional climate. Results show a relationship between changes in floodplain habitats and annual flood magnitude, as well as between hydrology and the cooling and warming phases of the Pacific Decadal Oscillation (PDO). Large magnitude floods and greater frequency of moderate floods were associated with the cooling phases of the PDO, resulting in a floodplain environment dominated by extensive restructuring and regeneration of floodplain habitats. Conversely, warming phases of the PDO corresponded with decreases in magnitude, duration, and frequency of critical flows, creating a floodplain environment dominated by late successional vegetation and low levels of physical restructuring. Over the 60-year time series, habitat change was widespread throughout the floodplain, though the relative abundances of the habitats did not change greatly. We conclude that the long- and short-term interactions of climate, floods, and plant succession produce a shifting habitat mosaic that is a fundamental attribute of natural floodplain ecosystems. 相似文献
633.
Nest-site selection is an important determinant of individual fitness in birds. Understanding what information individuals use to choose nest sites is therefore important for understanding the evolution of nest-site selection, the dynamics of populations, and the conservation of species. We used five years of mark-recapture data for Mountain Bluebirds (Sialia currucoides) to examine how dispersal probability and nest-site selection vary with potential cues of nest-site quality. Dispersal distance between breeding seasons and nest-site selection were modeled as a function of personal reproductive success, conspecific density, conspecific reproductive success, and habitat type. Between years, the dispersal probability was related to personal reproductive success, not conspecific information, and individuals fledging fewer young dispersed longer distances. For dispersing individuals, the probability that a nest site was selected in year i was negatively related to distance from the nest site selected in year i - 1 for all age and sex classes, and positively related to conspecific density and reproductive success in year i - 1 for both second-year (SY) and after-hatch-year (AHY) females. However, nest-site selection in year i was more strongly related to conspecific density in year i- 1 for hatch-year (HY) females and was much more strongly related to the reproductive success of conspecifics in year i - 1 for AHY females. Nest-site selection of HY and AHY males was not consistently related to the metrics of conspecific information, but we suspect that relationships were obscured by competitive interactions. We found no evidence indicating that individuals respond differently to conspecific information at longer distances, suggesting that individuals limit dispersal to areas where they have prior knowledge. We predict that these patterns of nest-site selection will allow birds to loosely track nest-site quality and maintain an ideal free distribution, where average fitness is equal in all habitat types. 相似文献
634.
Sheppard PR Speakman RJ Ridenour G Glascock MD Farris C Witten ML 《Environmental geochemistry and health》2007,29(5):405-412
Spatial patterns of tungsten and cobalt are described for surface dust of Fallon, Nevada, where a cluster of childhood leukemia
has been ongoing since 1997. In earlier research, airborne tungsten and cobalt was shown to be elevated in total suspended
particulates in Fallon. To fine-tune the spatial patterns of tungsten and cobalt deposition in Fallon, surface dust was collected
in a grid pattern within as well as outside of Fallon to establish background concentrations of metals. In surface dust, tungsten
and cobalt show sharp peaks (934 ppm and 98 ppm, respectively) within Fallon just north of highway 50 and west of highway
95. These two peaks overlap spatially, and given the grid pattern used for collecting surface dust, the source area of these
two airborne metals can be pinpointed to the vicinity of hard-metal industry located north of highway 50 and west of highway
95. Fallon is distinctive in west central Nevada because of high airborne tungsten and cobalt particulates, and given its
cluster of childhood leukemia, it stands to reason that additional biomedical research is in order to test directly the leukogenicity
of combined airborne tungsten and cobalt particulates. 相似文献
635.
636.
Clarifying values,risk perceptions,and attitudes to resolve or avoid social conflicts in invasive species management
下载免费PDF全文
![点击此处可从《Conservation biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Rodrigo A. Estévez Christopher B. Anderson J. Cristobal Pizarro Mark A. Burgman 《Conservation biology》2015,29(1):19-30
Decision makers and researchers recognize the need to effectively confront the social dimensions and conflicts inherent to invasive species research and management. Yet, despite numerous contentious situations that have arisen, no systematic evaluation of the literature has examined the commonalities in the patterns and types of these emergent social issues. Using social and ecological keywords, we reviewed trends in the social dimensions of invasive species research and management and the sources and potential solutions to problems and conflicts that arise around invasive species. We integrated components of cognitive hierarchy theory and risk perceptions theory to provide a conceptual framework to identify, distinguish, and provide understanding of the driving factors underlying disputes associated with invasive species. In the ISI Web of Science database, we found 15,915 peer‐reviewed publications on biological invasions, 124 of which included social dimensions of this phenomenon. Of these 124, 28 studies described specific contentious situations. Social approaches to biological invasions have emerged largely in the last decade and have focused on both environmental social sciences and resource management. Despite being distributed in a range of journals, these 124 articles were concentrated mostly in ecology and conservation‐oriented outlets. We found that conflicts surrounding invasive species arose based largely on differences in value systems and to a lesser extent stakeholder and decision maker's risk perceptions. To confront or avoid such situations, we suggest integrating the plurality of environmental values into invasive species research and management via structured decision making techniques, which enhance effective risk communication that promotes trust and confidence between stakeholders and decision makers. Clarificar los Valores, Percepciones de Riesgo y Actitudes para Resolver o Evitar Conflictos Sociales en el Manejo de Especies Invasoras 相似文献
637.
The theory behind,and the challenges of,conserving nature's stage in a time of rapid change
下载免费PDF全文
![点击此处可从《Conservation biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Joshua J. Lawler David D. Ackerly Christine M. Albano Mark G. Anderson Solomon Z. Dobrowski Jacquelyn L. Gill Nicole E. Heller Robert L. Pressey Eric W. Sanderson Stuart B. Weiss 《Conservation biology》2015,29(3):618-629
Most conservation planning to date has focused on protecting today's biodiversity with the assumption that it will be tomorrow's biodiversity. However, modern climate change has already resulted in distributional shifts of some species and is projected to result in many more shifts in the coming decades. As species redistribute and biotic communities reorganize, conservation plans based on current patterns of biodiversity may fail to adequately protect species in the future. One approach for addressing this issue is to focus on conserving a range of abiotic conditions in the conservation‐planning process. By doing so, it may be possible to conserve an abiotically diverse “stage” upon which evolution will play out and support many actors (biodiversity). We reviewed the fundamental underpinnings of the concept of conserving the abiotic stage, starting with the early observations of von Humboldt, who mapped the concordance of abiotic conditions and vegetation, and progressing to the concept of the ecological niche. We discuss challenges posed by issues of spatial and temporal scale, the role of biotic drivers of species distributions, and latitudinal and topographic variation in relationships between climate and landform. For example, abiotic conditions are not static, but change through time—albeit at different and often relatively slow rates. In some places, biotic interactions play a substantial role in structuring patterns of biodiversity, meaning that patterns of biodiversity may be less tightly linked to the abiotic stage. Furthermore, abiotic drivers of biodiversity can change with latitude and topographic position, meaning that the abiotic stage may need to be defined differently in different places. We conclude that protecting a diversity of abiotic conditions will likely best conserve biodiversity into the future in places where abiotic drivers of species distributions are strong relative to biotic drivers, where the diversity of abiotic settings will be conserved through time, and where connectivity allows for movement among areas providing different abiotic conditions. 相似文献
638.
Byela Tibesigwa Martine Visser Mark Collinson Wayne Twine 《Sustainability Science》2016,11(2):193-214
This paper examines the impact of agriculture-related shocks on consumption patterns of rural farming households using 3 years of data from South Africa. We make two key observations. First, agriculture-related shocks reduce households’ consumption. Second, natural resources and informal social capital somewhat counteract this reduction and sustain dietary requirements. In general, our findings suggest the promotion of informal social capital and natural resources as they are cheaper and more accessible coping strategies, in comparison to, for example, insurance, which remains unaffordable in most rural parts of sub-Saharan Africa. However, a lingering concern centres on the sustainability of these less conventional adaptation strategies. 相似文献
639.
The resilience perspective has emerged as a plausible approach to confront the increasingly devastating impacts of disasters; and the challenges and uncertainty climate change poses through an expected rise in frequency and magnitude of hazards. Stakeholder participation is posited as pivotal for building resilience, and resilience is not passive; rather, stakeholders are actively involved in the process of building resilience. Who is involved and how they are involved are crucial aspects for developing resilience in practice. Nevertheless, there are few empirical studies available to inform theory or show how these issues are addressed. This study focuses on revealing how practitioners frame the issue of participation in relation to resilience, its relevance to a changing climate and how, in consequence, they construct practices. Using Hajer's [(1995). The politics of environmental discourse: Ecological modernization and the policy process. New York] ‘Social-interactive discourse theory’, in this interdisciplinary research, we study the frames and subsequent practices developed around a disaster management policy initiative in Australia: the Natural Disaster Resilience Program in Queensland. What emerges from the research findings as critical and requiring urgent attention is stakeholder and especially local government and community participation, and for this to become socially relevant, challenges such as meaningful communication and power structures need to be addressed. What is also critical is to move from experiential learning to social learning. Additionally, the results presented here offer empirical evidence on how broadening the pool of actors can be implemented, and the opportunities that this opens up for building resilience. 相似文献
640.