首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   13篇
  免费   1篇
环保管理   1篇
综合类   1篇
基础理论   9篇
污染及防治   1篇
评价与监测   2篇
  2014年   1篇
  2013年   2篇
  2011年   1篇
  2010年   1篇
  2009年   1篇
  2008年   1篇
  2007年   1篇
  2006年   1篇
  2004年   1篇
  2001年   1篇
  1997年   1篇
  1995年   1篇
  1981年   1篇
排序方式: 共有14条查询结果,搜索用时 31 毫秒
1.
2.
3.
Following habitat alteration or fragmentation, competition, parasitism, and predation from species that live in the new habitats may reduce the survival and reproductive success of species living in the original habitats. Negative influences from species that live outside the remnant patches are expected to be greater in small rather than in large remnant patches because more "external" species are expected to move through the centers of small remnant patches. We surveyed birds within remnant patches of old-growth montane forests on Vancouver Island, Canada, (1) to evaluate whether the richness and abundance of non-old-growth bird species were larger at the center of small rather than large patches and (2) to evaluate whether the opposite was true of old-growth bird species. More non-old-growth bird species were present at the center of small remnant patches of old growth than in large old-growth patches. We found no relationship, however, between patch size and richness or abundance of old-growth bird species at the center of remnant patches of old growth. This was true for old-growth species with open, cup-shaped nests and cavity nests. Old-growth birds may have been affected less in our study area than in other areas because they evolved within heterogeneous montane forests and interacted with non-old-growth species throughout their evolutionary histories or because the contrast between old-growth forests and logged areas was less than that between the forests and agricultural/urban areas that were surveyed in other studies.  相似文献   
4.
Abstract:  Databases on the distribution of species can be used to describe the geographic patterns of biodiversity. Nevertheless, they have limitations. We studied three of these limitations: (1) inadequacy of raw data to describe richness patterns due to sampling bias, (2) lack of survey effort assessment (and lack of exhaustiveness in compiling data about survey effort), and (3) lack of coverage of the geographic and environmental variations that affect the distribution of organisms. We used a biodiversity database (BIOTA-Canarias) to analyze richness data from a well-known group (seed plants) in an intensively surveyed area (Tenerife Island). Observed richness and survey effort were highly correlated. Species accumulation curves could not be used to determine survey effort because data digitalization was not exhaustive, so we identified well-sampled sites based on observed richness to sampling effort ratios. We also developed a predictive model based on the data from well-sampled sites and analyzed the origin of the geographic errors in the obtained extrapolation by means of a geographically constrained cross-validation. The spatial patterns of seed-plant species richness obtained from BIOTA-Canarias data were incomplete and biased. Therefore, some improvements are needed to use this database (and many others) in biodiversity studies. We propose a protocol that includes controls on data quality, improvements on data digitalization and survey design to improve data quality, and some alternative data analysis strategies that will provide a reliable picture of biodiversity patterns.  相似文献   
5.
Abstract: The current shortfall in effectiveness within conservation biology is illustrated by increasing interest in “evidence‐based conservation,” whose proponents have identified the need to benchmark conservation initiatives against actions that lead to proven positive effects. The effectiveness of conservation policies, approaches, and evaluation is under increasing scrutiny, and in these areas models of excellence used in business could prove valuable. Typically, conservation programs require years of effort and involve rigorous long‐term implementation processes. Successful balance of long‐term efforts alongside the achievement of short‐term goals is often compromised by management or budgetary constraints, a situation also common in commercial businesses. “Business excellence” is an approach many companies have used over the past 20 years to ensure continued success. Various business excellence evaluations have been promoted that include concepts that could be adapted and applied in conservation programs. We describe a conservation excellence model that shows how scientific processes and results can be aligned with financial and organizational measures of success. We applied the model to two well‐documented species conservation programs. In the first, the Po’ouli program, several aspects of improvement were identified, such as more authority for decision making in the field and better integration of habitat management and population recovery processes. The second example, the black‐footed ferret program, could have benefited from leadership effort to reduce bureaucracy and to encourage use of best‐practice species recovery approaches. The conservation excellence model enables greater clarity in goal setting, more‐effective identification of job roles within programs, better links between technical approaches and measures of biological success, and more‐effective use of resources. The model could improve evaluation of a conservation program's effectiveness and may be used to compare different programs, for example during reviews of project performance by sponsoring organizations.  相似文献   
6.

Residues of the pyrimidine fungicide pyrimethanil [N-(4,6-dimethylpyrimidin-2yl)aniline] were determined in table grapes “Italia” by gas chromatography nitrogen-phosphorus detector (GC-NPD). Pesticides were extracted from grapes with ethyl acetate and hexane solution (1:1 v/v), and were analyzed without any further clean up. Pyrimethanil was confirmed by high-performance liquid chromatography (HPLC) fitted with a diode array detector (DAD) and electrospray ionization mass spectrometry (ESI-MS) in the select ion-monitoring mode (SIM). The residue of pyrimethanil was under the legal limit immediately after treatment, and showed a half-life time, calculated as a reaction of pseudo first order, of 12 days, with a regression coefficient of 0.9954. Recoveries from fortified grapes ranged between 90 and 113% with a maximum coefficient of variation (CV) of 11%. The calculated limits of detection and quantitation for pyrimethanil were 0.005 and 0.01 mg/kg, respectively.  相似文献   
7.
A survey of the crown status of Turkey oak Quercus cerris L.) trees in the boron-rich area atTravale (Southern Tuscany, Italy) was carried outin order to evaluate the impact ofgeothermal power plants. Crown thinness was assessed andmorphological and chemical tests werecarried out on leaf samples. Leaf area and dry weight weredetermined as morphological parameters;while the chemical measurements performed included nitrogenand potassium (among the nutrients),and sulphur, boron, arsenic and mercury (among the elements ofgeothermal origin). Acute damagewas found only in the area immediately adjacent to the outletsand is the result of the action of boron;crown thinness, on the other hand, is affected by the natureof the geological substrate. High quantitiesof sulphur were found in leaves throughout the survey area,due both to the availability of this elementin the geopedological substrate and to the atmospheric inputof geothermal H2S. The leafcontent of this element correlates negatively with thedistance from the power plants. Boron andarsenic are the other geothermal origin elements most commonlyfound in plant matrices. The presenceof these two elements is associated with leaf area reductionand/or an increase of specific dry weight.The most significant impact on the environment appears to beexerted by the southernmost powerplant, where there is an unfavourable ratio between quantityof emissions and height of the chimneys.  相似文献   
8.
两步回归法研究空气污染与儿童呼吸病症率的关系   总被引:6,自引:0,他引:6       下载免费PDF全文
通过两步回归法对空气污染与儿童呼吸病症发生率之间的关系进行了研究.结果表明,颗粒物与大部分儿童呼吸病症发生率之间存在显著的正相关关系,SO2与儿童感冒时气喘有着显著的正相关关联,NOX与儿童未感冒时气喘有显著的正相关关联.两种回归方法的结果基本一致.其中的混合线性模型不但在城市间发现这些正相关关系,而且在城市内的城郊区之间也发现了正相关关联.本文还给出了暴露在各种空气污染物下儿童呼吸病症发生率的比数比(OR).  相似文献   
9.
10.
Abstract:  Changes in temperature, precipitation, and other climatic drivers and sea-level rise will affect populations of existing native and non-native aquatic species and the vulnerability of aquatic environments to new invasions. Monitoring surveys provide the foundation for assessing the combined effects of climate change and invasions by providing baseline biotic and environmental conditions, although the utility of a survey depends on whether the results are quantitative or qualitative, and other design considerations. The results from a variety of monitoring programs in the United States are available in integrated biological information systems, although many include only non-native species, not native species. Besides including natives, we suggest these systems could be improved through the development of standardized methods that capture habitat and physiological requirements and link regional and national biological databases into distributed Web portals that allow drawing information from multiple sources. Combining the outputs from these biological information systems with environmental data would allow the development of ecological-niche models that predict the potential distribution or abundance of native and non-native species on the basis of current environmental conditions. Environmental projections from climate models can be used in these niche models to project changes in species distributions or abundances under altered climatic conditions and to identify potential high-risk invaders. There are, however, a number of challenges, such as uncertainties associated with projections from climate and niche models and difficulty in integrating data with different temporal and spatial granularity. Even with these uncertainties, integration of biological and environmental information systems, niche models, and climate projections would improve management of aquatic ecosystems under the dual threats of biotic invasions and climate change.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号