全文获取类型
收费全文 | 116篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
环保管理 | 14篇 |
综合类 | 1篇 |
基础理论 | 100篇 |
灾害及防治 | 2篇 |
出版年
2014年 | 10篇 |
2013年 | 5篇 |
2012年 | 1篇 |
2011年 | 6篇 |
2010年 | 9篇 |
2009年 | 2篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2001年 | 3篇 |
1997年 | 4篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有117条查询结果,搜索用时 359 毫秒
61.
JAMES R. HERKERT 《Conservation biology》2009,23(4):1036-1040
Abstract: The role of agricultural landscapes in biodiversity conservation has been largely ignored despite their potential role in conserving declining species. Within agricultural landscapes, set-aside programs may offer the most promising conservation opportunities due to the large area involved in these programs. I explored the relationship between set-aside effect size—on the basis of data from field studies of birds in cropland and set-aside fields—and population changes following establishment of these fields. Species whose abundance was most strongly influenced by the establishment of set-aside lands also tended to show positive changes in population trends following broad-scale implementation of the set-aside program. This relationship was strongest for grassland obligate birds, a group of birds experiencing broad-scale population declines throughout North America. There is now increasing evidence that set-aside lands within the United States are providing population-level benefits to grassland birds. Nevertheless, there are also increasing concerns about the stability of these set-aside lands in the face of increased demand for crops and rising commodity prices. If set-aside area within the United States is allowed to decline, additional declines of birds and perhaps other taxa within agricultural landscapes seem likely. 相似文献
62.
Identifying Habitat Variables Important to the Rare Columbia Spotted Frog in Utah (U.S.A.): an Information-Theoretic Approach 总被引:1,自引:0,他引:1
Abstract: We identified habitat associations of the rare Columbia spotted frog ( Rana luteiventris ). We used an information-theoretic approach that encouraged careful consideration of previous studies, demanded a priori formulation of hypotheses and models, and provided interpretable results while avoiding some criticisms of traditional statistical analyses. We formulated hypotheses about habitat associations based on conductivity, emergent vegetation, littoral zone depth, pond hydrology, and water temperature. We modeled hypothesized associations with logistic regression and used Akaike's information criterion to quantify evidence for models, weigh the relative importance of each habitat variable, and select predictive models. Although variable, results suggested that spotted frogs are more likely to occur in ponds that do not shrink in size seasonally, maintain relatively constant seasonal water temperature, and have high emergent vegetation cover. Associations we identified will assist actions in Utah that may be critical to local persistence of spotted frogs. Moreover, this approach for identifying associations has great potential for other rare species. 相似文献
63.
Abstract: Several studies have reported climate-associated changes in phenotypically plastic traits of amphibians, yet it remains unknown whether amphibians can manifest an evolutionary response to global climate change at the rate and magnitude that it is occurring. To assess this issue, we examined temporal change in the morphology of the red-backed salamander ( Plethodon cinereus ), a small, abundant woodland salamander distributed widely in eastern North America with two distinct morphotypes: striped individuals associated with cooler microclimates and unstriped individuals associated with warmer microclimates. We compiled morph frequencies for 50,960 individual salamanders from 558 sites as recorded in the published literature and in unpublished field notes of herpetologists between 1908 and 2004. We observed that striping probability increased with increasing latitude, longitude, and elevation and decreased (from 80% to 74% range wide) with time. The combined forces of regional climate warming and, particularly, forest disturbance have evidently been sufficient to cause morphological evolution in this amphibian over the last century. 相似文献
64.
65.
JAMES R. THOMSON RALPH Mac NALLY †† ERICA FLEISHMAN†‡ GREG HORROCKS 《Conservation biology》2007,21(3):752-766
Abstract: Landscape optimization for biodiversity requires prediction of species distributions under alternative revegetation scenarios. We used Bayesian model averaging with logistic regression to predict probabilities of occurrence for 61 species of birds within highly fragmented box–ironbark forests of central Victoria, Australia. We used topographic, edaphic, and climatic variables as predictors so that the models could be applied to areas where vegetation has been cleared but may be replanted. Models were evaluated with newly acquired, independent data collected in large blocks of remnant native vegetation. Successful predictions were obtained for 18 of 45 woodland species (40%). Model averaging produced more accurate predictions than "single best" models. Models were most successful for smaller-bodied species that probably depend on particular vegetation types. Predictions for larger, generalist species, and seasonal migrants were less successful, partly because of changes in species distributions between model building (1995–1997) and validation (2004–2005) surveys. We used validated models to project occurrence probabilities for individual species across a 12,000-km2 region, assuming native vegetation was present. These predictions are intended to be used as inputs, along with landscape context and temporal dynamics, into optimization algorithms to prioritize revegetation. Longer-term data sets to accommodate temporal dynamics are needed to improve the predictive accuracy of models. 相似文献
66.
HERBERT TUSHABE§§§ JAMES KALEMA ACHILLES BYARUHANGA† JOSEPHINE ASASIRA PAUL SSEGAWA REW BALMFORD‡ TIM DAVENPORT§ JON FJELDSÅ IB FRIIS†† DEBORAH PAIN DEREK POMEROY PAUL WILLIAMS§§ CHARLES WILLIAMS‡ 《Conservation biology》2006,20(1):85-99
Abstract: BirdLife International's Important Bird Areas (IBA) program is the most developed global system for identifying sites of conservation priority. There have been few assessments, however, of the conservation value of IBAs for nonavian taxa. We combined past data with extensive new survey results for Uganda's IBAs in the most comprehensive assessment to date of the wider biodiversity value of a tropical country's IBA network. The combined data set included more than 35,000 site × species records for birds, butterflies, and woody plants at 86 Ugandan sites (23,400 km2 ), including 29 of the country's 30 IBAs, with data on additional taxa for many sites. Uganda's IBAs contained at least 70% of the country's butterfly and woody plant species, 86% of its dragonflies and 97% of its birds. They also included 21 of Uganda's 22 major vegetation types. For butterflies, dragonflies, and some families of plants assessed, species of high conservation concern were well represented (less so for the latter). The IBAs successfully represented wider biodiversity largely because many have distinctive avifaunas and, as shown by high cross-taxon congruence in complementarity, such sites tended to be distinctive for other groups too. Cross-taxon congruence in overall species richness was weaker and mainly associated with differences in site size. When compared with alternative sets of sites selected using complementarity-based, area-based, or random site-selection algorithms, the IBA network was efficient in terms of the number of sites required to represent species but inefficient in terms of total area. This was mainly because IBA selection considers factors other than area, however, which probably improves both the cost-effectiveness of the network and the persistence of represented species. 相似文献
67.
68.
KEVIN T. SHOEMAKER ALVIN R. BREISCH JESSE W. JAYCOX JAMES P. GIBBS 《Conservation biology》2013,27(3):542-551
For decades conservation biologists have proposed general rules of thumb for minimum viable population size (MVP); typically, they range from hundreds to thousands of individuals. These rules have shifted conservation resources away from small and fragmented populations. We examined whether iteroparous, long‐lived species might constitute an exception to general MVP guidelines. On the basis of results from a 10‐year capture‐recapture study in eastern New York (U.S.A.), we developed a comprehensive demographic model for the globally threatened bog turtle (Glyptemys muhlenbergii), which is designated as endangered by the IUCN in 2011. We assessed population viability across a wide range of initial abundances and carrying capacities. Not accounting for inbreeding, our results suggest that bog turtle colonies with as few as 15 breeding females have >90% probability of persisting for >100 years, provided vital rates and environmental variance remain at currently estimated levels. On the basis of our results, we suggest that MVP thresholds may be 1–2 orders of magnitude too high for many long‐lived organisms. Consequently, protection of small and fragmented populations may constitute a viable conservation option for such species, especially in a regional or metapopulation context. Reexaminando el Concepto de Población Mínima Viable para Especies Longevas Resumen 相似文献
69.
Effects of Recreational Impacts on Soil Microbial Communities 总被引:51,自引:0,他引:51
/ The functional diversity of soil microbial communities in heavilyimpacted subalpine campsites and adjacent undisturbed areas was comparedusing the Biolog method of carbon utilization profiles. Principal componentsanalysis of patterns and level of microbial activity indicate that microbialcommunities differentiate in response to disturbance in the top 6 cm of soil,while below 6 cm there were no recognizable differences between disturbed andundisturbed soil communities. Analysis of the factors that differentiate theupper microbial communities between disturbed and undisturbed sites revealedthat the percent of total carbon sources utilized was significantly less inthe disturbed (54%) than in undisturbed areas (95%). Carbonsubstrates important in the discrimination between soil communities includeplant, invertebrate, and microbial derivatives that could not be metabolizedby microbial communities from disturbed sites. Comparisons of totalculturable actinomycetes, bacteria, and fungi reveal no difference in overallnumber of colony forming units (CFU) on disturbed and undisturbed sites, buta marked decrease in actinomycetes on disturbed sites. Biolog andspread-plate data combined indicate a shift in the structure and function ofthe microbial community in campsite soils, which may be a useful indicator ofsoil community disturbance.KEY WORDS: Microbial functional diversity; Anthropogenic disturbance;Recreational impacts; Carbon source profile; Subalpine 相似文献
70.
The Long-Term Effects of Tiger Poaching on Population Viability 总被引:4,自引:0,他引:4
JOHN S. KENNEY JAMES L. D. SMITH ANTHONY M. STARFIELD CHARLES W. MCDOUGAL 《Conservation biology》1995,9(5):1127-1133
Poaching tigers, primarily for their bones, has become the latest threat to the persistence of wild tiger populations throughout the world. Anecdotal information indicates the seriousness of this new threat. It is important, however, to provide a quantitative analysis of poaching as a basis for strong policy action. We therefore created a tiger simulation model to explore the effects of realistic levels of poaching on population viability. The model is an individually based, stochastic spatial model that is based on the extensive data set from Royal Chitwan National Park, Nepal. We found that as poaching continues over time, the probability of population extinction increases sigmoidally; a critical zone exists in which a small, incremental increase in poaching greatly increases the probability of extinction. The implication is that poaching may not at first be seen as a threat but could suddenly become one. Moreover, even if poaching is effectively stopped, tiger populations will still be vulnerable and could go extinct due to demographic and environmental stochasticity. Our model also shows that poaching reduces genetic variability, which could further reduce population viability due to inbreeding depression. The longer poaching is allowed to continue, the more vulnerable a population will be to these stochastic events. At currently reported rates of poaching our analysis indicates that many wild tiger populations will be extirpated during the latter half of the 1990s. 相似文献