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   282篇
  免费   1篇
  国内免费   1篇
安全科学   4篇
废物处理   18篇
环保管理   57篇
综合类   54篇
基础理论   62篇
环境理论   1篇
污染及防治   66篇
评价与监测   10篇
社会与环境   9篇
灾害及防治   3篇
  2021年   4篇
  2020年   4篇
  2019年   9篇
  2017年   6篇
  2016年   6篇
  2015年   3篇
  2014年   5篇
  2013年   36篇
  2012年   14篇
  2011年   15篇
  2010年   8篇
  2009年   9篇
  2008年   11篇
  2007年   13篇
  2006年   12篇
  2005年   8篇
  2004年   8篇
  2003年   17篇
  2002年   8篇
  2001年   8篇
  2000年   7篇
  1999年   1篇
  1998年   5篇
  1997年   2篇
  1996年   3篇
  1995年   5篇
  1994年   3篇
  1993年   1篇
  1991年   3篇
  1990年   4篇
  1989年   3篇
  1988年   3篇
  1987年   1篇
  1986年   5篇
  1985年   6篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1980年   2篇
  1978年   4篇
  1976年   2篇
  1975年   1篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1971年   1篇
  1968年   1篇
  1967年   1篇
  1966年   1篇
  1958年   1篇
排序方式: 共有284条查询结果,搜索用时 31 毫秒
261.
262.
263.
Much present research on the relationship between socio-economic factors and the siting of sources of environmental pollution has focused primarily on race and income. Using census data, timed-based data from multiple sources of pollution, and rates of cancers and low birth weight in the State of Michigan by zip code, we present a multivariate model that can distinguish the effects of race, income and other land use characteristics on: (1) the location of different sources of pollution; (2) progress toward clean-up of contaminated waste; and (3) how pollution is associated with measures of public health.  相似文献   
264.
265.
Parrent JL  Morris WF  Vilgalys R 《Ecology》2006,87(9):2278-2287
Ectomycorrhizal fungi (EMF), a phylogenetically and physiologically diverse guild, form symbiotic associations with many trees and greatly enhance their uptake of nutrients and water. Elevated CO2, which increases plant carbon supply and demand for mineral nutrients, may change the composition of the EMF community, possibly altering nutrient uptake and ultimately forest productivity. To assess CO2 effects on EMF communities, we sampled mycorrhizae from the FACTS-I (Forest-Atmosphere Carbon Transfer and Storage) research site in Duke Forest, Orange County, North Carolina, USA, where Pinus taeda forest plots are maintained at either ambient or elevated CO2 (200 ppm above ambient) concentrations. Mycorrhizae were identified by DNA sequence similarity of the internal transcribed spacer ribosomal RNA gene region. EMF richness was very high; 72 distinct phylotypes were detected from 411 mycorrhizal samples. Overall EMF richness and diversity were not affected by elevated CO2, but increased CO2 concentrations altered the relative abundances of particular EMF taxa colonizing fine roots, increased prevalence of unique EMF species, and led to greater EMF community dissimilarity among individual study plots. Natural variation among plots in mean potential net nitrogen (N) mineralization rates was a key determinant of EMF community structure; increasing net N mineralization rate was negatively correlated with EMF richness and had differential effects on the abundance of particular EMF taxa. Our results predict that, at CO2 concentrations comparable to that predicted for the year 2050, EMF community composition and structure will change, but diversity will be maintained. In contrast, high soil N concentrations can negatively affect EMF diversity; this underscores the importance of considering CO2 effects on forest ecosystems in the context of background soil chemical parameters and other environmental perturbations such as acid deposition or fertilizer runoff.  相似文献   
266.
Assessing the scope and severity of threats is necessary for evaluating impacts on populations to inform conservation planning. Quantitative threat assessment often requires monitoring programs that provide reliable data over relevant spatial and temporal scales, yet such programs can be difficult to justify until there is an apparent stressor. Leveraging efforts of wildlife management agencies to record winter counts of hibernating bats, we collated data for 5 species from over 200 sites across 27 U.S. states and 2 Canadian provinces from 1995 to 2018 to determine the impact of white-nose syndrome (WNS), a deadly disease of hibernating bats. We estimated declines of winter counts of bat colonies at sites where the invasive fungus that causes WNS (Pseudogymnoascus destructans) had been detected to assess the threat impact of WNS. Three species undergoing species status assessment by the U.S. Fish and Wildlife Service (Myotis septentrionalis, Myotis lucifugus, and Perimyotis subflavus) declined by more than 90%, which warrants classifying the severity of the WNS threat as extreme based on criteria used by NatureServe. The scope of the WNS threat as defined by NatureServe criteria was large (36% of Myotis lucifugus range) to pervasive (79% of Myotis septentrionalis range) for these species. Declines for 2 other species (Myotis sodalis and Eptesicus fuscus) were less severe but still qualified as moderate to serious based on NatureServe criteria. Data-sharing across jurisdictions provided a comprehensive evaluation of scope and severity of the threat of WNS and indicated regional differences that can inform response efforts at international, national, and state or provincial jurisdictions. We assessed the threat impact of an emerging infectious disease by uniting monitoring efforts across jurisdictional boundaries and demonstrated the importance of coordinated monitoring programs, such as the North American Bat Monitoring Program (NABat), for data-driven conservation assessments and planning.  相似文献   
267.
The solubility data for a series of non‐hydrogen bonding, monosubstituted benzenes in binary mixtures of water and non‐hydrogen bonding cosolvents is presented. Good correlation between log solubility and fraction cosolvent is obtained, therefore the estimation of solubility in mixed solvents by a log‐linear relationship can be attained. Slight positive or negative deviations from predicted solubility values are seen at high volume fractions of cosolvents. These deviations are attributed to the cosolvent‐water interactions.  相似文献   
268.
Persistence of species in fragmented landscapes depends on dispersal among suitable breeding sites, and dispersal is often influenced by the "matrix" habitats that lie between breeding sites. However, measuring effects of different matrix habitats on movement and incorporating those differences into spatially explicit models to predict dispersal is costly in terms of time and financial resources. Hence a key question for conservation managers is: Do more costly, complex movement models yield more accurate dispersal predictions? We compared the abilities of a range of movement models, from simple to complex, to predict the dispersal of an endangered butterfly, the Saint Francis' satyr (Neonympha mitchellii francisci). The value of more complex models differed depending on how value was assessed. Although the most complex model, based on detailed movement behaviors, best predicted observed dispersal rates, it was only slightly better than the simplest model, which was based solely on distance between sites. Consequently, a parsimony approach using information criteria favors the simplest model we examined. However, when we applied the models to a larger landscape that included proposed habitat restoration sites, in which the composition of the matrix was different than the matrix surrounding extant breeding sites, the simplest model failed to identify a potentially important dispersal barrier, open habitat that butterflies rarely enter, which may completely isolate some of the proposed restoration sites from other breeding sites. Finally, we found that, although the gain in predicting dispersal with increasing model complexity was small, so was the increase in financial cost. Furthermore, a greater fit continued to accrue with greater financial cost, and more complex models made substantially different predictions than simple models when applied to a novel landscape in which butterflies are to be reintroduced to bolster their populations. This suggests that more complex models might be justifiable on financial grounds. Our results caution against a pure parsimony approach to deciding how complex movement models need to be to accurately predict dispersal through the matrix, especially if the models are to be applied to novel or modified landscapes.  相似文献   
269.
Morris DW  MacEachern JT 《Ecology》2010,91(11):3131-3137
Density-dependent habitat selection has numerous and far-reaching implications to population dynamics and evolutionary processes. Although several studies suggest that organisms choose and occupy high-quality habitats over poorer ones, definitive experiments demonstrating active selection, by the same individuals at the appropriate population scale, are lacking. We conducted a reciprocal food supplementation experiment to assess whether voles would first occupy a habitat receiving extra food, then change their preference to track food supplements moved to another habitat. Meadow voles, as predicted, were more abundant in food-supplemented habitat than in others. Density declined when food supplements ceased because the voles moved to the new habitat receiving extra food. Although males and females appeared to follow different strategies, meadow-vole densities reflected habitat quality because voles actively selected the best habitat available. It is thus clear that behavioral decisions on habitat use can motivate patterns of abundance, frequency, and gene flow that have widespread effects on subsequent evolution.  相似文献   
270.
A method previously used to measure thickness of the surface mucus layer (SML) of the mammalian gastrointestinal tract has been applied to the SML of reef corals. It involves manual measurement of mucus thickness using a micromanipulator and fine glass needle (micropipette) and is non-destructive to the coral, meaning that repeated measurements can be taken. A measurable mucus layer was recorded in all cases in the study, which comprised 450 individual thickness measurements from four coral species. Mucus thickness ranged from 145 to 700 μm. Thus, whatever dynamic processes control mucus synthesis, secretion to the tissue surface and subsequent release into the water column, a continuous mucosal barrier is maintained. A change in SML thickness was recorded as a response to aerial exposure during the natural tidal cycle and to solar exposure-induced bleaching, although the response due to bleaching varied between two studied species. The technique is rapid, cost-effective and a simple means of assessing coral SML thickness, a variable that shows significant variation in relation to environmental conditions and is likely to be an important health indicator in these organisms.  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