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   305篇
  免费   11篇
  国内免费   5篇
安全科学   9篇
废物处理   16篇
环保管理   47篇
综合类   79篇
基础理论   73篇
污染及防治   71篇
评价与监测   12篇
社会与环境   9篇
灾害及防治   5篇
  2023年   6篇
  2022年   13篇
  2021年   20篇
  2020年   12篇
  2019年   11篇
  2018年   19篇
  2017年   10篇
  2016年   19篇
  2015年   6篇
  2014年   14篇
  2013年   16篇
  2012年   14篇
  2011年   22篇
  2010年   12篇
  2009年   18篇
  2008年   11篇
  2007年   10篇
  2006年   12篇
  2005年   9篇
  2004年   6篇
  2003年   11篇
  2002年   11篇
  2001年   8篇
  2000年   3篇
  1999年   1篇
  1998年   4篇
  1996年   4篇
  1995年   1篇
  1994年   4篇
  1993年   1篇
  1992年   1篇
  1990年   2篇
  1988年   1篇
  1984年   1篇
  1983年   1篇
  1981年   2篇
  1979年   2篇
  1976年   1篇
  1974年   1篇
  1973年   1篇
排序方式: 共有321条查询结果,搜索用时 46 毫秒
251.
Monitoring the number of animals in a wildlife population is an important task. In this paper, we estimate the number of active and successful bald eagle nests in a specific region using dual frame sampling techniques. The dual frame method combines independent samples from an incomplete list frame and an area frame that is assumed to be complete. Hartley's screening estimator is used to combine sample information from both frames. This methodology will be useful for monitoring any wildlife population where the breeding individuals have highly visible nesting territories which tend to be stable over many years.  相似文献   
252.
Environmental Management - Grizzly bears (Ursus arctos) appear to be attracted to natural and anthropogenic forage along railways, which may increase collision vulnerability, but also potentially...  相似文献   
253.
Common-pool governance principles are becoming increasingly important tools for natural resource management with communities and comanagement arrangements. Effectiveness of these principles depends on variability in agreements, trust, and adherence to institutional norms. We evaluated heterogeneity in governance principles by asking 449 people in 30 fishing communities in 4 East African countries to rate their effectiveness. The influences of individuals, their membership and role in stakeholder community groups, leadership, community, and country were tested. The membership and role of people were not the main influence on their perceptions of the effectiveness of governance principles. Therefore, drawing conclusions about the effectiveness of specific principles would be difficult to make independent of the individuals asked. More critical were individuals’ nationalities and their associations with the shared perceptions of a response-group's effectiveness of each principle. Perceptions of effectiveness differed strongly by country, and respondents from poor nations (Madagascar and Mozambique) were more cohesiveness but had fewer and weaker between-community conflict-resolution mechanisms. Overall, group identity, group autonomy, decision-making process, and conflict resolution principles were perceived to be most effective and likely to be enforced by repeated low-cost intragroup activities. Graduated sanctions, cost–benefit sharing, and monitoring resource users, fisheries, and ecology were the least scaled principles and less affordable via local control. We suggest these 2 groups of principles form independently and, as economies develop and natural resources become limiting, sustainability increasingly depends on the later principles. Therefore, management effectiveness in resource-limited situations depends on distributing power, skills, and costs beyond fishing communities to insure conservation needs are met.  相似文献   
254.
Near‐shore marine environments are increasingly subjected to reduced water quality, and their ability to withstand it is critical to their persistence. The potential role marine reserves may play in mitigating the effects of reduced water quality has received little attention. We investigated the spatial and temporal variability in live coral and macro‐algal cover and water quality during moderate and major flooding events of the Fitzroy River within the Keppel Bay region of the Great Barrier Reef Marine Park from 2007 to 2013. We used 7 years of remote sensing data on water quality and data from long‐term monitoring of coral reefs to quantify exposure of coral reefs to flood plumes. We used a distance linear model to partition the contribution of abiotic and biotic factors, including zoning, as drivers of the observed changes in coral and macro‐algae cover. Moderate flood plumes from 2007 to 2009 did not affect coral cover on reefs in the Keppel Islands, suggesting the reef has intrinsic resistance against short‐term exposure to reduced water quality. However, from 2009 to 2013, live coral cover declined by ~50% following several weeks of exposure to turbid, low salinity water from major flood plume events in 2011 and subsequent moderate events in 2012 and 2013. Although the flooding events in 2012 and 2013 were smaller than the flooding events between 2007 to 2009, the ability of the reefs to withstand these moderate floods was lost, as evidenced by a ~20% decline in coral cover between 2011 to 2013. Although zoning (no‐take reserve or fished) was identified a significant driver of coral cover, we recorded consistently lower coral cover on reserve reefs than on fished reefs throughout the study period and significantly lower cover in 2011. Our findings suggest that even reefs with an inherent resistance to reduced water quality are not able to withstand repeated disturbance events. The limitations of reserves in mitigating the effects of reduced water quality on near‐shore coral reefs underscores the importance of integrated management approaches that combine effective land‐based management with networks of no‐take reserves.  相似文献   
255.
256.
The relative contribution of in situ reproduction versus immigration to the recruitment process is important to ecologists. Here we consider a robust design superpopulation capture-recapture model for a population with two age classes augmented with population assignment data. We first use age information to estimate the entry probabilities of new animals originating via in situ reproduction and immigration separately for all except the first period. Then we combine age and population assignment information with the capture-recapture model, which enables us to estimate the entry probability of in situ births and the entry probability of immigrants separately for all sampling periods. Further, this augmentation of age specific capture-recapture data with population assignment data greatly improves the estimators’ precision. We apply our new model to a capture-recapture data set with genetic information for banner-tailed kangaroo rats in Southern Arizona. We find that many more individuals are born in situ than are immigrants for all time periods. Young animals have lower survival probabilities than adults born in situ. Adult animals born in situ have higher survival probabilities than adults that were immigrants.  相似文献   
257.
The outcomes of species recovery programs have been mixed; high‐profile population recoveries contrast with species‐level extinctions. Each conservation intervention has its own challenges, but to inform more effective management it is imperative to assess whether correlates of wider recovery program success or failure can be identified. To contribute to evidence‐based improvement of future conservation strategies, we conducted a global quantitative analysis of 48 mammalian recovery programs. We reviewed available scientific literature and conducted semistructured interviews with conservation professionals involved in different recovery programs to investigate ecological, management, and political factors associated with population recoveries or declines. Identifying and removing threats was significantly associated with increasing population trend and decreasing conservation dependence, emphasizing that populations are likely to continue to be compromised in the absence of effective threat mitigation and supporting the need for threat monitoring and adaptive management in response to new and potential threats. Lack of habitat and small population size were cited as limiting factors in 56% and 42% of recovery programs, respectively, and both were statistically associated with increased longer term dependence on conservation intervention, demonstrating the importance of increasing population numbers quickly and restoring and protecting habitat. Poor stakeholder coordination and management were also regularly cited by respondents as key weaknesses in recovery programs, indicating the importance of effective leadership and shared goals and management plans. Project outcomes were not influenced by biological or ecological variables such as body mass or habitat, which suggests that these insights into correlates of conservation success and failure are likely to be generalizable across mammals.  相似文献   
258.
We present a robust sampling methodology to estimate population size using line transect and capture-recapture procedures for aerial surveys. Aerial surveys usually underestimate population density due to animals being missed. A combination of capture-recapture and line transect sampling methods with multiple observers allows violation of the assumption that all animals on the centreline are sighted from the air. We illustrate our method with an example of inanimate objects which shows evidence of failure of the assumption that all objects on the centreline have probability 1 of being detected. A simulation study is implemented to evaluate the performance of three variations of the Lincoln-Petersen estimator: the overall estimator, the stratified estimator, and the general stratified estimator based on the combined likelihood proposed in this paper. The stratified Lincoln-Petersen estimator based on the combined likelihood is found to be generally superior to the other estimators.  相似文献   
259.
Summary. The turnip sawfly Athalia rosae sequesters glucosinolates from its cruciferous host plants in the larval stage. Investigation of the chemosensory and behavioural responses of adult A. rosae to glucosinolates and their volatile hydrolysis products, isothiocyanates, revealed that females detect glucosinolates by contact chemoreception and isothiocyanates by antennal olfaction. In electroantennogram recordings, four isothiocyanates (allyl [2-propenyl] isothiocyanate, benzyl isothiocyanate, butyl isothiocyanate and iberverin [3-methylthiopropyl isothiocyanate]) were active at all doses presented, including the lowest (0.1 μg), whilst the threshold for detection of three others, iberin [3-methylsulphinylpropyl isothiocyanate], methyl isothiocyanate, and sulforaphane [4-methylsulphinylbutyl isothiocyanate], was higher, at between 1 and 10 μg (source concentration of volatiles). Allyl isothiocyanate attracted experienced females in a four-chambered olfactometer, whilst na?ve females showed no response. Allyl isothiocyanate also attracted mature females to baited yellow water traps in field trials, although immature females were repelled at high isothiocyanate concentrations. In laboratory behavioural bioassays the glucosinolates sinigrin (allyl [2-propenyl] glucosinolate) and sinalbin (p-hydroxybenzyl glucosinolate), stimulated ovipositor probing in mature female A. rosae to an extent comparable to hot-water extracts of their host plants. These responses show that glucosinolates and isothiocyanates play an important role in host finding and host recognition in A. rosae.  相似文献   
260.
The goal of this work is to make ecotoxicologically-relevant substance bands visible on thin-layer chromatographic plates. Bacteria (Bacillus subtilis, Vibrio fischeri, Salmonella typhimurium), fungi (Aspergillus niger), algi (Pseudokirchneriella subcapitata) and pollen (Impatiens walleriana) were used as test organisms. With the aid of these organisms, it has been possible to identify bactericide, fungicide, algicide, phytotoxic and genotoxic bands.  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