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   87篇
  免费   2篇
  国内免费   9篇
安全科学   3篇
废物处理   5篇
环保管理   22篇
综合类   17篇
基础理论   27篇
污染及防治   6篇
评价与监测   7篇
社会与环境   7篇
灾害及防治   4篇
  2024年   1篇
  2022年   1篇
  2021年   2篇
  2020年   4篇
  2019年   2篇
  2018年   2篇
  2017年   2篇
  2016年   1篇
  2015年   5篇
  2014年   5篇
  2013年   9篇
  2012年   6篇
  2011年   6篇
  2010年   11篇
  2009年   10篇
  2008年   6篇
  2007年   5篇
  2006年   1篇
  2005年   6篇
  2004年   3篇
  2003年   2篇
  2002年   3篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
排序方式: 共有98条查询结果,搜索用时 468 毫秒
41.
The level of conditioned behavior in animals is proportional to the intensity, amount, frequency, or probability of reinforcement. Interestingly, this matching can be dynamic, with performance levels following, for example, a switch in the probability of reinforcement with a short delay. We previously found that conditioned performance levels in Drosophila match reinforcement intensity in a place conditioning paradigm. Whether Drosophila can match conditioned behavior to a change in reinforcement intensity was an open question. In this study, we found that both conditioned behavior and memory levels match reinforcement intensity after a switch, and this rapid matching occurs within 2 min. Thus, fruit flies can dynamically match conditioned behavior and memory levels to a change in reinforcement intensity.  相似文献   
42.
以上海环城林带为对象,采用美景度评判法进行不同植被类型的景观评价,评价分为林内景观和林外景观2个空间层次,分别在春、夏、秋、冬4个季节进行。结果表明,林内景观平均值和林外景观的美景度都表现为夏季最高,冬季最低。在不同植被类型的林内景观中,落叶针叶林在不同季节均表现出最高的美景度,竹林的美景度最低;针叶林中,常绿针叶林的美景度四季均低于落叶针叶林;阔叶林中,落叶阔叶林的美景度在春季和夏季高于常绿落叶林,常绿阔叶林在秋季和冬季高于落叶阔叶林;混交林中,除秋季外,针阔混交林的美景度均高于常绿落叶阔叶混交林。  相似文献   
43.
苔藓植物资源保护利用中的生态环境效应研究进展   总被引:2,自引:0,他引:2  
苔藓植物资源丰富、种类繁多、分布广泛,是一类以孢子繁殖,由水生向陆生过渡的高等植物。苔藓植物的结构相对简单,对环境变化的反应较为敏感,被广泛应用为环境污染的指示植物。苔藓植物生长与所处的环境有关,而它的生长对土壤结皮形成、水土保持、生态小环境改善等方面又发挥着重要的促进作用。综述了苔藓植物的资源分布、苔藓植物对环境污染的响应、苔藓植物的生态效应等方面的研究进展,但是目前的研究领域及其研究角度还存在着各自的不足。随着经济建设快速发展,世界各地大量的矿山开采、水电开发等工程建设对土地、自然环境的破坏日益严重,非农业建设以及农产品需求不断增加造成了农田的生态结构与功能发生着不断变化。针对各地经济社会发展以及城乡建设现状,积极开展工程建设领域以及农田生态系统苔藓植物的生态环境效应研究是今后值得十分重视的研究方向。  相似文献   
44.
苔藓植物资源丰富、种类繁多、分布广泛,是一类以孢子繁殖,由水生向陆生过渡的高等植物。苔藓植物的结构相对简单,对环境变化的反应较为敏感,被广泛应用为环境污染的指示植物。苔藓植物生长与所处的环境有关,而它的生长对土壤结皮形成、水土保持、生态小环境改善等方面又发挥着重要的促进作用。综述了苔藓植物的资源分布、苔藓植物对环境污染的响应、苔藓植物的生态效应等方面的研究进展,但是目前的研究领域及其研究角度还存在着各自的不足。随着经济建设快速发展,世界各地大量的矿山开采、水电开发等工程建设对土地、自然环境的破坏日益严重,非农业建设以及农产品需求不断增加造成了农田的生态结构与功能发生着不断变化。针对各地经济社会发展以及城乡建设现状,积极开展工程建设领域以及农田生态系统苔藓植物的生态环境效应研究是今后值得十分重视的研究方向。  相似文献   
45.
Through extensive research, ecosystem services have been mapped using both survey-based and biophysical approaches, but comparative mapping of public values and those quantified using models has been lacking. In this paper, we mapped hot and cold spots for perceived and modeled ecosystem services by synthesizing results from a social-values mapping study of residents living near the Pike–San Isabel National Forest (PSI), located in the Southern Rocky Mountains, with corresponding biophysically modeled ecosystem services. Social-value maps for the PSI were developed using the Social Values for Ecosystem Services tool, providing statistically modeled continuous value surfaces for 12 value types, including aesthetic, biodiversity, and life-sustaining values. Biophysically modeled maps of carbon sequestration and storage, scenic viewsheds, sediment regulation, and water yield were generated using the Artificial Intelligence for Ecosystem Services tool. Hotspots for both perceived and modeled services were disproportionately located within the PSI’s wilderness areas. Additionally, we used regression analysis to evaluate spatial relationships between perceived biodiversity and cultural ecosystem services and corresponding biophysical model outputs. Our goal was to determine whether publicly valued locations for aesthetic, biodiversity, and life-sustaining values relate meaningfully to results from corresponding biophysical ecosystem service models. We found weak relationships between perceived and biophysically modeled services, indicating that public perception of ecosystem service provisioning regions is limited. We believe that biophysical and social approaches to ecosystem service mapping can serve as methodological complements that can advance ecosystem services-based resource management, benefitting resource managers by showing potential locations of synergy or conflict between areas supplying ecosystem services and those valued by the public.  相似文献   
46.
In this article, we examine how issues of scale affect the integration of recreation management with the management of other natural resources on public lands. We present two theories used to address scale issues in ecology and explore how they can improve the two most widely applied recreation-planning frameworks. The theory of patch dynamics and hierarchy theory are applied to the recreation opportunity spectrum (ROS) and the limits of acceptable change (LAC) recreation-planning frameworks. These frameworks have been widely adopted internationally, and improving their ability to integrate with other aspects of natural resource management has significant social and conservation implications. We propose that incorporating ecologic criteria and scale concepts into these recreation-planning frameworks will improve the foundation for integrated land management by resolving issues of incongruent boundaries, mismatched scales, and multiple-scale analysis. Specifically, we argue that whereas the spatially explicit process of the ROS facilitates integrated decision making, its lack of ecologic criteria, broad extent, and large patch size decrease its usefulness for integration at finer scales. The LAC provides explicit considerations for weighing competing values, but measurement of recreation disturbances within an LAC analysis is often done at too fine a grain and at too narrow an extent for integration with other recreation and resource concerns. We suggest that planners should perform analysis at multiple scales when making management decisions that involve trade-offs among competing values. The United States Forest Service is used as an example to discuss how resource-management agencies can improve this integration.  相似文献   
47.
Elevated atmospheric NH3 levels near intensive livestock operations can add significant N to local agroecosystems. In this study, the potential atmospheric NH3 sorbed by soil and water was assessed over a 2-year period starting October 2000 in an intensive livestock production area in southern Alberta, Canada. Fifty-two uneven grid sampling sites were selected in the 53,905 ha study area. The sorption rate of atmospheric NH3 was estimated weekly by exposing distilled water and air-dried soil samples to the atmosphere at the sampling sites. The increases in NH4–N content in the samples after 1-week exposure was regarded as an index of the atmospheric NH3 sorbed for that week. The NH3 sorption rates were highly variable across the 52 sites, with water ranging from 4 to 125 kg ha−1 year−1 with a mean of 22 kg N ha−1 year−1 and soil from 5 to 84 kg N ha−1 year−1 with a mean of 20 kg N ha−1 year−1. Considerable variation in NH3–N sorption across the study area reflects the effects of size, direction (upwind or downwind) and proximity of nearby livestock operations or other NH3 sources and operators’ activities around the sampling sites. The NH3 sorption rate at each site also varied considerably in response to weather conditions. The high rate of NH3 input poses a direct risk of surface water eutrophication in intensive livestock operation areas. If fertilizer recommendations are not reduced to account for NH3 sorption by soil, excess N may also contribute to eutrophication through runoff and leaching.  相似文献   
48.
Good governance is of paramount importance to the success of parks and protected areas. This research utilized a questionnaire for 10 principles of governance to evaluate the outsourcing model used by British Columbia Provincial Parks, where profit-making corporations provide all front country visitor services. A total of 246 respondents representing five stakeholder groups evaluated the model according to each principle, using an online survey. Principal component analysis resulted in two of the 10 principles (equity and effectiveness) each being split into two categories, leading to 12 governance principles. Five of the 12 criteria received scores towards good governance: effectiveness outcome; equity general; strategic vision; responsiveness; and effectiveness process. One criterion, public participation, was on the neutral point. Six criteria received scores below neutral, more towards weak governance: transparency; rule of law; accountability; efficiency; consensus orientation; and, equity finance. The five stakeholder groups differed significantly on 10 of the 12 principles (P < .05). The 2 exceptions were for efficiency and effectiveness process. Seven of the 12 criteria followed a pattern wherein government employees and contractors reported positive scores, visitors and representatives of NGOs reported more negative scores, and nearby residents reported mid-range scores. Three criteria had government employees and contractors reporting the most positive scores, residents and visitors the most negative scores, and NGO respondents reporting mid-range scores. This research found evidence that perceptions of governance related to this outsourcing model differed significantly amongst various constituent groups.  相似文献   
49.
50.
城市道路绿化带不同植物叶片附尘对大气污染的磁学响应   总被引:3,自引:1,他引:2  
隆茜  周菊珍  孟颉  达良俊 《环境科学》2012,33(12):4188-4193
对上海市金沙江路两侧绿化带内24个常绿植物叶片样品进行了磁性与重金属测试,以探讨城市道路绿化带不同植物叶片附尘对大气污染的磁学响应.结果表明,χ、SIRM值分别在(4~59)×10-8m3.kg-1和(496~6 114)×10-6Am2.kg-1之间变化,S-300 mT在89%~98%之间变动.所有植物样品中χARM/χ〈4,χARM/SIRM〈30×10-5mA-1.磁性参数表明,植物叶片附尘以亚铁磁性矿物为主,磁性矿物颗粒以假单畴(PSD)-多畴(MD)为主.重金属元素Zn、Cu、Pb含量与反映亚铁磁性矿物含量的χ、SIRM、χARM呈显著正相关,可以将磁性参数SIRM作为叶片重金属元素的替代指标.推荐在上海地区广泛种植的广玉兰作为道路植物污染的指示植物。  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