全文获取类型
收费全文 | 281篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 10篇 |
环保管理 | 25篇 |
综合类 | 1篇 |
基础理论 | 232篇 |
污染及防治 | 5篇 |
评价与监测 | 1篇 |
灾害及防治 | 8篇 |
出版年
2014年 | 20篇 |
2013年 | 25篇 |
2012年 | 4篇 |
2011年 | 12篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 16篇 |
2007年 | 19篇 |
2006年 | 18篇 |
2005年 | 25篇 |
2004年 | 27篇 |
2003年 | 11篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1982年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有282条查询结果,搜索用时 78 毫秒
231.
DAVID HALL-MATTHEWS 《Disasters》1996,20(3):216-230
The principles upon which famine policies are based have changed less than might be expected over the last century. This paper examines the origins of the Indian Famine Codes of the 1880s, which set the administrative and, it is argued, paradigmatic precedent for famine relief in 'developing' countries, managed by 'developed' ones. In particular, the still-current questions of avoiding the creation of dependency through over-generous aid and of relying on free-market solutions to the problems of food distribution are re-examined. Although both of these issues are difficult, it is suggested that strong emphasis on their importance has historically been based on wilful misinterpretation of complex situations. The result has been famine relief programmes which served the interests of 'relievers' (in this case the colonial state) more than the relieved. The nature of famine policy-making is thus reconsidered, with a call for greater appreciation of the role of influential individuals and hidden state agendas. These are as significant today as ever. 相似文献
232.
Integrating Landscape and Metapopulation Modeling Approaches: Viability of the Sharp-Tailed Grouse in a Dynamic Landscape 总被引:9,自引:0,他引:9
H. REIT AKÇAKAYA VOLKER C. RADELOFF† DAVID J. MLADENOFF† HONG S. HE‡ 《Conservation biology》2004,18(2):526-537
Abstract: The lack of management experience at the landscape scale and the limited feasibility of experiments at this scale have increased the use of scenario modeling to analyze the effects of different management actions on focal species. However, current modeling approaches are poorly suited for the analysis of viability in dynamic landscapes. Demographic (e.g., metapopulation) models of species living in these landscapes do not incorporate the variability in spatial patterns of early successional habitats, and landscape models have not been linked to population viability models. We link a landscape model to a metapopulation model and demonstrate the use of this model by analyzing the effect of forest management options on the viability of the Sharp-tailed Grouse ( Tympanuchus phasianellus ) in the Pine Barrens region of northwestern Wisconsin (U.S.A.). This approach allows viability analysis based on landscape dynamics brought about by processes such as succession, disturbances, and silviculture. The landscape component of the model (LANDIS) predicts forest landscape dynamics in the form of a time series of raster maps. We combined these maps into a time series of patch structures, which formed the dynamic spatial structure of the metapopulation component (RAMAS). Our results showed that the viability of Sharp-tailed Grouse was sensitive to landscape dynamics and demographic variables such as fecundity and mortality. Ignoring the landscape dynamics gave overly optimistic results, and results based only on landscape dynamics (ignoring demography) lead to a different ranking of the management options than the ranking based on the more realistic model incorporating both landscape and demographic dynamics. Thus, models of species in dynamic landscapes must consider habitat and population dynamics simultaneously. 相似文献
233.
DAVID OLSON‡ LINDA FARLEY WAISEA NAISILISILI ALIPATE RAIKABULA OM PRASAD† JAMES ATHERTON CRAIG MORLEY† 《Conservation biology》2006,20(2):568-572
Abstract: On Pacific islands non-native rats and mongooses threaten many native species. In Fiji we compared visitation rates of rats and mongooses at bait stations and measured biomass of leaf-litter invertebrates to assess the relative predation pressure from these species in forest areas at different distances from the forest edge. Forest areas over 5 km from the forest edge had significantly fewer baits encountered by rats or mongooses than did natural forest areas nearer agricultural and urban habitats. Remote forest areas may function as a last refuge for island species threatened by predation from non-native rats and mongooses. The biomass of leaf-litter invertebrates in remote forest areas was higher, indicating a refuge effect for some taxa targeted by rats and mongooses. Protection of the few remaining large blocks of natural forests on Pacific islands may be the most cost-effective approach for conserving many island endemics threatened by rats and mongooses. Logging roads can compromise this refuge effect by acting as dispersal routes for rats into natural forests. 相似文献
234.
DAVID P. EDWARDS FELICITY A. ANSELL ABDUL H. AHMAD REUBEN NILUS KEITH C. HAMER 《Conservation biology》2009,23(6):1628-1633
Abstract: The recent advent of carbon crediting has led to a rapid rise in biosequestration projects that seek to remove carbon from the atmosphere through afforestation and forest rehabilitation. Such projects also present an important potential opportunity to reverse biodiversity losses resulting from deforestation and forest degradation, but the biodiversity benefits of different forms of biosequestration have not been considered adequately. We captured birds in mist nets to examine the effects of rehabilitation of logged forest on birds in Sabah, Borneo, and to test the hypothesis that rehabilitation restores avian assemblages within regenerating forest to a condition closer to that seen in unlogged forest. Species richness and diversity were similar in unlogged and rehabilitated forest, but significantly lower in naturally regenerating forest. Rehabilitation resulted in a relatively rapid recovery of populations of insectivores within logged forest, especially those species that forage by sallying, but had a marked adverse effect on frugivores and possibly reduced the overall abundance of birds within regenerating forest. In view of these results, we advocate increased management for heterogeneity within rehabilitated forests, but we strongly urge an increased role for forest rehabilitation in the design and implementation of a biodiversity‐friendly carbon‐offsetting market. 相似文献
235.
Indirect Effects of Biological Control on Plant Diversity Vary across Sites in Montana Grasslands 总被引:3,自引:0,他引:3
Abstract: Biological control with specialist, nonindigenous, herbivorous insects is an important option for controlling invasive exotic plants in wildlands and nature reserves. It is assumed that biological control agents will reduce the dominance of the target weed, thereby increasing the native diversity of the associated plant community. However, this hypothesis has rarely been tested. We introduced Aphthona nigriscutis into grassland sites infested with the invasive exotic species Euphorbia esula L. on a nature reserve in Montana (U.S.A.). Two sites with better soil had been treated previously with herbicide, whereas two other sites had not. We measured the density and biomass of Euphorbia vegetative and flowering stems and number of native and exotic shrubs, grass-like plants, and forbs in 48 microplots in Aphthona release and control macroplots at each site. After 5 years, Aphthona release was associated with a 33–39% decline in Euphorbia aboveground biomass compared with controls at all sites. Other effects of the biocontrol depended on the site. Biocontrol slowed the recovery of species diversity at the sites previously treated with herbicide but slowed the loss of diversity at sites without a history of herbicide. Biocontrol introduction was not associated with a disproportionate increase in nontarget exotic species. Release of Aphthona caused a decline in the biomass of flowering stems relative to controls at good-soil, previous-herbicide sites but was associated with a relative increase in flower stem mass at poor-soil, no-herbicide sites. Our results suggest that biocontrol reductions in weed dominance will not always be associated with increased species diversity. More emphasis should be placed on conserving desirable communities and less on simple weed control. Monitoring of community-level effects should accompany biocontrol introductions on nature reserves. 相似文献
236.
237.
238.
DAVID W. ORR 《Conservation biology》2005,19(2):290-292
Note from the Editor : Some readers may feel that topics such as politics and religion are inappropriate for a scientific journal. Our "Conservation in Context" column, however, is intended to cover the entire spectrum of the context within which the science of conservation biology must operate. Thus, we freely and openly explore topics in this column that ordinarily are not addressed in scientific journals, to better understand the real-world constraints and opportunities that define how conservation science is applied in a complex world. 相似文献
239.
JULIAN J. O'GRADY MARK A. BURGMAN† DAVID A. KEITH‡ LAWRENCE L. MASTER§ SANDY J. ANDELMAN BARRY W. BROOK†† GEOFFREY A. HAMMERSON§ TRACEY REGAN† RICHARD FRANKHAM‡‡§§ 《Conservation biology》2004,18(6):1624-1635
Abstract: Many different systems are used to assess levels of threat faced by species. Prominent ones are those used by the World Conservation Union, NatureServe, and the Florida Game and Freshwater Fish Commission (now the Florida Fish and Wildlife Conservation Commission). These systems assign taxa a threat ranking by assessing their demographic and ecological characteristics. These threat rankings support the legislative protection of species and guide the placement of conservation programs in order of priority. It is not known, however, whether these assessment systems rank species in a similar order. To resolve this issue, we assessed 55 mainly vertebrate taxa with widely differing life histories under each of these systems and determined the rank correlations among them. Moderate, significant positive correlations were seen among the threat rankings provided by the three systems (correlations 0.58–0.69). Further, the threat rankings for taxa obtained using these systems were significantly correlated to their rankings based on predicted probability of extinction within 100 years as determined by population viability analysis (correlations 0.28–0.37). The different categorization systems, then, yield related but not identical threat rankings, and these rankings are associated with predicted extinction risk. 相似文献
240.