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   273篇
  免费   6篇
  国内免费   8篇
安全科学   19篇
废物处理   25篇
环保管理   45篇
综合类   25篇
基础理论   48篇
污染及防治   54篇
评价与监测   51篇
社会与环境   13篇
灾害及防治   7篇
  2023年   3篇
  2022年   5篇
  2021年   7篇
  2020年   4篇
  2019年   8篇
  2018年   13篇
  2017年   10篇
  2016年   10篇
  2015年   11篇
  2014年   12篇
  2013年   28篇
  2012年   13篇
  2011年   11篇
  2010年   9篇
  2009年   14篇
  2008年   9篇
  2007年   20篇
  2006年   9篇
  2005年   14篇
  2004年   8篇
  2003年   10篇
  2002年   8篇
  2001年   6篇
  2000年   9篇
  1999年   6篇
  1998年   3篇
  1997年   3篇
  1996年   1篇
  1995年   2篇
  1994年   2篇
  1993年   7篇
  1992年   4篇
  1991年   2篇
  1989年   1篇
  1988年   1篇
  1982年   1篇
  1981年   1篇
  1979年   2篇
排序方式: 共有287条查询结果,搜索用时 15 毫秒
31.
In the Wasatch Range Metropolitan Area of Northern Utah, water management decision makers confront multiple forms of uncertainty and risk. Adapting to these uncertainties and risks is critical for maintaining the long‐term sustainability of the region's water supply. This study draws on interview data to assess the major challenges climatic and social changes pose to Utah's water future, as well as potential solutions. The study identifies the water management adaptation decision‐making space shaped by the interacting institutional, social, economic, political, and biophysical processes that enable and constrain sustainable water management. The study finds water managers and other water actors see challenges related to reallocating water, including equitable water transfers and stakeholder cooperation, addressing population growth, and locating additional water supplies, as more problematic than the challenges posed by climate change. Furthermore, there is significant disagreement between water actors over how to best adapt to both climatic and social changes. This study concludes with a discussion of the path dependencies that present challenges to adaptive water management decision making, as well as opportunities for the pursuit of a new water management paradigm based on soft‐path solutions. Such knowledge is useful for understanding the institutional and social adaptations needed for water management to successfully address future uncertainties and risks.  相似文献   
32.
The United States and other developed countries are faced with restoring and managing degraded ecosystems. Evaluations of the degradation of ecological resources can be used for determining ecological risk, making remediation or restoration decisions, aiding stakeholders with future land use decisions, and assessing natural resource damages. Department of Energy (DOE) lands provide a useful case study for examining degradation of ecological resources in light of past or present land uses and natural resource damage assessment (NRDA). We suggest that past site history should be incorporated into the cleanup and restoration phase to reduce the ultimate NRDA costs, and hasten resource recovery. The lands that DOE purchased over 50 years ago ranged from relatively undisturbed to heavily impacted farmland, and the impact that occurred from DOE occupation varies from regeneration of natural ecosystems (benefits) to increased exposure to several stressors (negative effects). During the time of the DOE releases, other changes occurred on the lands, including recovery from the disturbance effects of farming, grazing, and residential occupation, and the cessation of human disturbance. Thus, the injury to natural resources that occurred as a result of chemical and radiological releases occurred on top of recovery of already degraded systems. Both spatial (size and dispersion of patch types) and temporal (past/present/future land use and ecological condition) components are critical aspects of resource evaluation, restoration, and NRDA. For many DOE sites, integrating natural resource restoration with remediation to reduce or eliminate the need for NRDA could be a win-win situation for both responsible parties and natural resource trustees by eliminating costly NRDAs by both sides, and by restoring natural resources to a level that satisfies the trustees, while being cost-effective for the responsible parties. It requires integration of remediation, restoration, and end-state planning to a greater degree than is currently done at most DOE sites.  相似文献   
33.
There are now numerous sustainable development evaluation methods to evaluate sustainable development progress. Which one to use will depend on the resources, the goals and the stakeholders. Ideally the method selected and its indicators would themselves indicate how to achieve sustainable development. Such a choice can be difficult without a framework to help ensure the representation of the essential elements of sustainable development.

This paper presents such a framework by drawing on ecological terminology to define aspects of sustainable development as manifested in the natural world. Examples of how these can be measured are provided along with an explanation of how the components of the framework contribute to achieving sustainable development in social systems.  相似文献   
34.

The pollination syndrome concept implies that flowers evolved with particular sets of characteristics, such as colors, shapes, orientations, and rewards, as a means of attracting pollinators. However, these traits may have also evolved to deter unwanted visitors. The North American genus Penstemon exhibits a great floral diversity that is mainly associated with bumblebee and hummingbird pollination. Evolutionary shifts from insect pollination to hummingbird pollination have occurred in Penstemon repeatedly, but some species maintain mixed-pollination systems and intermediate floral traits between bee- and hummingbird-pollination modes. The apparently intermediate floral traits of species with mixed-pollination systems might be potentially acting to deter bumblebee foragers. Then, bird-flower traits might be selected with increased hummingbird visitation over evolutionary time might, resulting in specialization to and the evolution of floral traits present in hummingbird-pollinated species. Here, we modified bee-pollination floral traits in Penstemon gentianoides with a mixed pollination system, to resemble hummingbird-pollination traits, and measured the effects of trait modification on bumblebee foraging behavior and plant female reproductive fitness. Our results showed that reduction in the width of the corolla tube and the absence of the corolla lip negatively affects bumblebee visitation and their efficiency as pollinators, and that the synergistic interaction of both traits enhanced the “anti-bee” effect. We conclude that acquisition of floral traits that resemble those of hummingbird-pollination enables Penstemon plant species to deter bumblebee visits.

  相似文献   
35.
A review of results of the research involving the quantitative and composition analyses of household waste conducted in Poland in recent years is presented in this paper. For these analyses various methodologies have been employed, as there is not one obligatory methodology how to characterise municipal solid waste. The results of the research in large Polish cities indicate great variability, which is difficult to be reasonably explained. This situation is affected by a number of factors, such as various methods and places for sample collection, various methods for tests, fractional character of most of the studies (studies carried out only in some periods during a year). Consequently, it is neither possible to measurably compare their results, nor to generalise them. Hence, within this article only individual data for large cities is provided. It is therefore necessary to standardise methodology for such analyses in Europe, taking into account local variability (such as different housing patterns, climate and waste collection schemes) to allow comparison of results.Reported yearly household waste generation in Polish cities varies from 238 to 309 kg per inhabitant. Biodegradable waste is a strongly dominated fraction in household waste from Polish cities, followed by paper/cardboard and plastics. Historical data shows that waste composition has undergone profound changes, the most significant being an increase of the share of plastics and decrease of fine fraction. The presented data indicates that waste composition strongly depends on the type of housing and its heating system. In the new multi-family buildings with central heating the share of paper and plastics is higher than in old houses with individual heating. In the latter ones the share of fine fraction is higher.  相似文献   
36.
37.
Knowing how people prepare for disasters is essential to developing resiliency strategies. This study examined recalled concerns, evacuation experiences, and the future preparedness plans of a vulnerable population in New Jersey, United States, following Hurricane Sandy in 2012. Understanding the responses of minority communities is key to protecting them during forthcoming disasters. Overall, 35 per cent of respondents were not going to prepare for an event. Intended future preparedness actions were unrelated to respondents' ratings of personal impact. More Blacks and Hispanics planned on preparing than Whites (68 versus 55 per cent), and more Hispanics planned on evacuating than did others who were interviewed. A higher percentage of respondents who had trouble getting to health centres were going to prepare than others. Respondents' concerns were connected to safety and survival, protecting family and friends, and having enough food and medicine, whereas future actions included evacuating earlier and buying sufficient supplies to shelter in place.  相似文献   
38.
39.
40.
Fishing pressure has increased the extinction risk of many elasmobranch (shark and ray) species. Although many countries have established no‐take marine reserves, a paucity of monitoring data means it is still unclear if reserves are effectively protecting these species. We examined data collected by a small group of divers over the past 21 years at one of the world's oldest marine protected areas (MPAs), Cocos Island National Park, Costa Rica. We used mixed effects models to determine trends in relative abundance, or probability of occurrence, of 12 monitored elasmobranch species while accounting for variation among observers and from abiotic factors. Eight of 12 species declined significantly over the past 2 decades. We documented decreases in relative abundance for 6 species, including the iconic scalloped hammerhead shark (Sphyrna lewini) (?45%), whitetip reef shark (Triaenodon obesus) (?77%), mobula ray (Mobula spp.) (?78%), and manta ray (Manta birostris) (?89%), and decreases in the probability of occurrence for 2 other species. Several of these species have small home ranges and should be better protected by an MPA, which underscores the notion that declines of marine megafauna will continue unabated in MPAs unless there is adequate enforcement effort to control fishing. In addition, probability of occurrence at Cocos Island of tiger (Galeocerdo cuvier), Galapagos (Carcharhinus galapagensis), blacktip (Carcharhinus limbatus), and whale (Rhincodon typus) sharks increased significantly. The effectiveness of MPAs cannot be evaluated by examining single species because population responses can vary depending on life history traits and vulnerability to fishing pressure.  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