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   139篇
  免费   70篇
  国内免费   47篇
安全科学   9篇
废物处理   4篇
环保管理   11篇
综合类   91篇
基础理论   88篇
污染及防治   22篇
评价与监测   16篇
社会与环境   6篇
灾害及防治   9篇
  2023年   5篇
  2022年   3篇
  2021年   10篇
  2020年   6篇
  2019年   4篇
  2018年   62篇
  2017年   11篇
  2016年   12篇
  2015年   7篇
  2014年   8篇
  2013年   17篇
  2012年   10篇
  2011年   8篇
  2010年   14篇
  2009年   11篇
  2008年   3篇
  2007年   3篇
  2006年   7篇
  2005年   5篇
  2004年   5篇
  2003年   7篇
  2002年   3篇
  2001年   9篇
  2000年   8篇
  1999年   3篇
  1996年   1篇
  1995年   4篇
  1994年   3篇
  1993年   1篇
  1991年   2篇
  1990年   2篇
  1985年   1篇
  1982年   1篇
排序方式: 共有256条查询结果,搜索用时 15 毫秒
201.
Land‐use change is the largest proximate threat to biodiversity yet remains one of the most complex to manage. In British Columbia (BC), where large mammals roam extensive tracts of intact habitat, continued land‐use development is of global concern. Extant mammal diversity in BC is unrivalled in North America owing, in part, to its unique position at the intersection of alpine, boreal, and temperate biomes. Despite high conservation values, understanding of cumulative ecological impacts from human development is limited. Using cumulative‐effects‐assessment (CEA) methods, we assessed the current human footprint over 16 regional ecosystems and 7 large mammal species. Using historical and current range estimates of the mammals, we investigated impacts of human land use on species’ persistence. For ecosystems, we found that bunchgrass, coastal Douglas fir, and ponderosa pine have been subjected to over 50% land‐use conversion, and over 85% of their spatial extent has undergone either direct or estimated indirect impacts. Of the mammals we considered, wolves were the least affected by land conversion, yet all species had reduced ranges compared with historical estimates. We found evidence of a hard trade‐off between development and conservation, most clearly for mammals with large distributions and ecosystems with high levels of conversion. Rather than serve as a platform to monitor species decline, we strongly advocate these data be used to inform land‐use planning and to assess current conservation efforts. More generally, CEAs offer a robust tool to inform wildlife and habitat conservation at scale.  相似文献   
202.
Reducing costs and increasing benefits for rural communities coexisting with large carnivores is necessary for conservation of jaguar (Panthera onca) and puma (Puma concolor). To design acceptable incentives, stakeholders must be involved in the process. We conducted an innovative, structured, group communication process based on a Delphi technique as a template for identifying potential incentives. Community workshops with 133 members of 7 communities and surveys with 25 multidisciplinary experts from government, nongovernmental organizations, and academia provided iterative data to design a plan of incentives through 4 rounds of discussion. The final product integrated 862 ideas into 6 types of incentives: organization of communities, mechanisms for improved dialogue, citizen technical assistance, green labeling for community products, payment for the ecosystem service of biodiversity, and an assessment of financial alternatives. We used quantitative and qualitative techniques to indicate support for decisions about the design of incentives, which reduced researcher subjectivity. The diverse incentives developed and the cooperation from multiple stakeholders resulted in an incentive plan that integrated issues of governance, equity, and social norms.  相似文献   
203.
Most examples that support the substitution‐habitat hypothesis (human‐made habitats act as substitutes of original habitat) deal with birds and mammals. We tested this hypothesis in 14 amphibians by using percentage occupancy as a proxy of habitat quality (i.e., higher occupancy percentages indicate higher quality). We classified water body types as original habitat (no or little human influence) depending on anatomical, behavioral, or physiological adaptations of each amphibian species. Ten species had relatively high probabilities (0.16–0.28) of occurrence in original habitat, moderate probability of occurrence in substitution habitats (0.11–0.14), and low probability of occurrence in refuge habitats (0.05–0.08). Thus, the substitution–habitat hypothesis only partially applies to amphibians because the low occupancy of refuges could be due to the negligible human persecution of this group (indicating good conservation status). However, low occupancy of refuges could also be due to low tolerance of refuge conditions, which could have led to selective extinction or colonization problems due to poor dispersal capabilities. That original habitats had the highest probabilities of occupancy suggests amphibians have a good conservation status in the region. They also appeared highly adaptable to anthropogenic substitution habitats.  相似文献   
204.
Systematic reviews are an increasingly popular decision‐making tool that provides an unbiased summary of evidence to support conservation action. These reviews bridge the gap between researchers and managers by presenting a comprehensive overview of all studies relating to a particular topic and identify specifically where and under which conditions an effect is present. However, several technical challenges can severely hinder the feasibility and applicability of systematic reviews, for example, homonyms (terms that share spelling but differ in meaning). Homonyms add noise to search results and cannot be easily identified or removed. We developed a semiautomated approach that can aid in the classification of homonyms among narratives. We used a combination of automated content analysis and artificial neural networks to quickly and accurately sift through large corpora of academic texts and classify them to distinct topics. As an example, we explored the use of the word reintroduction in academic texts. Reintroduction is used within the conservation context to indicate the release of organisms to their former native habitat; however, a Web of Science search for this word returned thousands of publications in which the term has other meanings and contexts. Using our method, we automatically classified a sample of 3000 of these publications with over 99% accuracy, relative to a manual classification. Our approach can be used easily with other homonyms and can greatly facilitate systematic reviews or similar work in which homonyms hinder the harnessing of large text corpora. Beyond homonyms we see great promise in combining automated content analysis and machine‐learning methods to handle and screen big data for relevant information in conservation science.  相似文献   
205.
Biodiversity offsetting aims to compensate for development‐induced biodiversity loss through commensurate conservation gains and is gaining traction among governments and businesses. However, cost shifting (i.e., diversion of offset funds to other conservation programs) and other perverse incentives can undermine the effectiveness of biodiversity offsetting. Additionality—the requirement that biodiversity offsets result in conservation outcomes that would not have been achieved otherwise—is fundamental to biodiversity offsetting. Cost shifting and violation of additionality can go hand in hand. India's national offsetting program is a case in point. Recent legislation allows the diversion of offset funds to meet the country's preexisting commitments under the United Nations Framework Convention on Climate Change (UNFCCC) and United Nations Convention on Biological Diversity (CBD). With such diversions, no additional conservation takes place and development impacts remain uncompensated. Temporary additionality cannot be conceded in light of paucity of funds for preexisting commitments unless there is open acknowledgement that fulfillment of such commitments is contingent on offset funds. Two other examples of perverse incentives related to offsetting in India are the touting of inherently neutral offsetting outcomes as conservation gains, a tactic that breeds false complacency and results in reduced incentive for additional conservation efforts, and the clearing of native vegetation for commercial plantations in the name of compensatory afforestation, a practice that leads to biodiversity decline. The risks accompanying cost shifting and other perverse incentives, if not preempted and addressed, will result in net loss of forest cover in India. We recommend accurate baselines, transparent accounting, and open reporting of offset outcomes to ensure biodiversity offsetting achieves adequate and additional compensation for impacts of development.  相似文献   
206.
Although marine protected areas can simultaneously contribute to biodiversity conservation and fisheries management, the global network is biased toward particular ecosystem types because they have been established primarily in an ad hoc fashion. The optimization of trade‐offs between biodiversity benefits and socioeconomic values increases success of protected areas and minimizes enforcement costs in the long run, but it is often neglected in marine spatial planning (MSP). Although the acquisition of spatially explicit socioeconomic data is perceived as a costly or secondary step in MSP, it is critical to account for lost opportunities by people whose activities will be restricted, especially fishers. We developed an easily reproduced habitat‐based approach to estimate the spatial distribution of opportunity cost to fishers in data‐poor regions. We assumed the most accessible areas have higher economic and conservation values than less accessible areas and their designation as no‐take zones represents a loss of fishing opportunities. We estimated potential distribution of fishing resources from bathymetric ranges and benthic habitat distribution and the relative importance of the different resources for each port of total catches, revenues, and stakeholder perception. In our model, we combined different cost layers to produce a comprehensive cost layer so that we could evaluate of trade‐offs. Our approach directly supports conservation planning, can be applied generally, and is expected to facilitate stakeholder input and community acceptance of conservation.  相似文献   
207.
A modern challenge for conservation biology is to assess the consequences of policies that adhere to assumptions of stationarity (e.g., historic norms) in an era of global environmental change. Such policies may result in unexpected and surprising levels of mitigation given future climate‐change trajectories, especially as agriculture looks to protected areas to buffer against production losses during periods of environmental extremes. We assessed the potential impact of climate‐change scenarios on the rates at which grasslands enrolled in the Conservation Reserve Program (CRP) are authorized for emergency harvesting (i.e., biomass removal) for agricultural use, which can occur when precipitation for the previous 4 months is below 40% of the normal or historical mean precipitation for that 4‐month period. We developed and analyzed scenarios under the condition that policy will continue to operate under assumptions of stationarity, thereby authorizing emergency biomass harvesting solely as a function of precipitation departure from historic norms. Model projections showed the historical likelihood of authorizing emergency biomass harvesting in any given year in the northern Great Plains was 33.28% based on long‐term weather records. Emergency biomass harvesting became the norm (>50% of years) in the scenario that reflected continued increases in emissions and a decrease in growing‐season precipitation, and areas in the Great Plains with higher historical mean annual rainfall were disproportionately affected and were subject to a greater increase in emergency biomass removal. Emergency biomass harvesting decreased only in the scenario with rapid reductions in emissions. Our scenario‐impact analysis indicated that biomass from lands enrolled in the CRP would be used primarily as a buffer for agriculture in an era of climatic change unless policy guidelines are adapted or climate‐change projections significantly depart from the current consensus.  相似文献   
208.
污泥和餐厨垃圾联合干法中温厌氧消化性能研究   总被引:8,自引:3,他引:5  
采用完全混合式反应器R1~R5(进料脱水污泥与餐厨垃圾的湿重混合比分别为1:0、4:1、3:2、2:3和0:1),在半连续运行的状态下,考察了停留时间(solid retention time,SRT)为20 d时脱水污泥和餐厨垃圾混合干法厌氧消化的产气性能、有机质降解性能和系统稳定性.结果表明,随着进料中餐厨垃圾所占比例的增大,系统的产气率和甲烷产率呈上升趋势,产气中甲烷含量呈下降趋势,污泥中添加餐厨垃圾有助于在利用原有消化罐容积的前提下显著提高有机负荷和体积产气率.餐厨垃圾比例越大,混合物料的水解速率常数越大,有机质降解率越高,R1~R4中有机质水解速率常数分别为0.25、0.61、1.09和1.56 d-1,有机质降解率分别为37.4%、50.6%、60.7%和68.2%,水解速率差异是导致VS降解率不同的主要原因.随着餐厨垃圾比例的增大,系统内pH、总碱度(total alkalinity,TA)、总氨氮(total ammonia nitrogen,TAN)和游离氨氮(free ammonianitrogen,FAN)呈下降趋势,当污泥中添加的餐厨垃圾提高60%时,系统内pH、总碱度、总氨氮和游离氨氮分别下降6%、16%、22%和75%.游离氨和Na+分别是影响污泥和餐厨垃圾单独干法消化稳定性的重要因素,污泥和餐厨垃圾混合消化可降低潜在抑制性物质的浓度,显著提高系统稳定性.  相似文献   
209.
基于Landsat 8影像估算新安江水库总悬浮物浓度   总被引:9,自引:4,他引:5  
总悬浮物(total suspended matter,TSM)直接决定着水下光场分布,进而影响水体的初级生产力,其浓度也是水质和水环境评价的重要参数之一.本研究构建了基于Landsat 8影像数据的较为清洁的新安江水库TSM的遥感估算模型,并给出了该水体TSM浓度的空间分布特征.结果表明,对该水体TSM浓度较为敏感波段为Landsat 8第二、三和八波段,线性相关的决定系数分别为0.37、0.51和0.42.然而,以上任何一个波段都无法单独用于准确地提取该区TSM浓度,而利用以上3个波段构建的多元回归模型能够给出较为准确的估算结果,模型决定系数为0.92,平均相对误差为11%,均方根误差为0.16mg·L-1.新安江水库TSM浓度整体较低,变化范围为0.04~24.54 mg·L-1,平均浓度为2.19 mg·L-1.高浓度部分位于湖的边缘区以及一些湖湾枝杈,如:枫树岭水域、汾口水域、威坪水域、安阳水域、大墅水域、临岐水域等,主要是受入湖河流以及邻近水域采砂活动的影响.因此研究认为利用Landsat 8数据的3个波段,采用多元回归模型能够较好地估算较清洁水体的TSM浓度.  相似文献   
210.
2004~2015年北京市清洁点臭氧浓度变化特征   总被引:4,自引:1,他引:3  
利用2004~2015年北京市自动监测网络O3浓度数据,综合探讨了北京市清洁点定陵站O3浓度的变化特征,结果表明,定陵站2004~2015年O31h浓度整体呈上升的趋势,年均浓度增长率为4.40 μg·m-3,定陵站O38h浓度整体呈下降的趋势,年均浓度增长率为-1.0 μg·m-3,5~9月O38h平均浓度增长率为-1.5 μg·m-3. 近3年来定陵站O38h重度污染天数增加明显,O3污染形势严峻. 定陵站每年6月左右O3浓度达到一年中的峰值,日变化上15:00~18:00左右出现小时浓度峰值且O3日峰值浓度是中心城区的1.01~1.56倍;不同年份5~9月定陵站O3日峰值浓度与城区站明显存在1 h滞后的现象,定陵站峰值浓度与城区峰值浓度之差近年来明显缩小,这可能一方面与O3区域污染输送有关,另一方面可能与北京市城镇化扩张有关.  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