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   1316篇
  免费   354篇
  国内免费   299篇
安全科学   92篇
废物处理   33篇
环保管理   99篇
综合类   632篇
基础理论   809篇
污染及防治   155篇
评价与监测   85篇
社会与环境   19篇
灾害及防治   45篇
  2024年   1篇
  2023年   13篇
  2022年   36篇
  2021年   36篇
  2020年   33篇
  2019年   51篇
  2018年   119篇
  2017年   89篇
  2016年   96篇
  2015年   111篇
  2014年   129篇
  2013年   154篇
  2012年   134篇
  2011年   144篇
  2010年   112篇
  2009年   103篇
  2008年   71篇
  2007年   58篇
  2006年   56篇
  2005年   55篇
  2004年   46篇
  2003年   43篇
  2002年   31篇
  2001年   30篇
  2000年   25篇
  1999年   21篇
  1998年   19篇
  1997年   18篇
  1996年   22篇
  1995年   20篇
  1994年   14篇
  1993年   14篇
  1992年   17篇
  1991年   6篇
  1990年   3篇
  1989年   6篇
  1988年   8篇
  1987年   2篇
  1985年   3篇
  1984年   3篇
  1983年   3篇
  1982年   2篇
  1981年   2篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1975年   1篇
  1974年   2篇
  1971年   1篇
排序方式: 共有1969条查询结果,搜索用时 125 毫秒
991.
Political transitions often trigger substantial environmental changes. In particular, deforestation can result from the complex interplay among the components of a system—actors, institutions, and existing policies—adapting to new opportunities. A dynamic conceptual map of system components is particularly useful for systems in which multiple actors, each with different worldviews and motivations, may be simultaneously trying to alter different facets of the system, unaware of the impacts on other components. In Myanmar, a global biodiversity hotspot with the largest forest area in mainland Southeast Asia, ongoing political and economic reforms are likely to change the dynamics of deforestation drivers. A fundamental conceptual map of these dynamics is therefore a prerequisite for interventions to reduce deforestation. We used a system‐dynamics approach and causal‐network analysis to determine the proximate causes and underlying drivers of forest loss and degradation in Myanmar from 1995 to 2016 and to articulate the linkages among them. Proximate causes included infrastructure development, timber extraction, and agricultural expansion. These were stimulated primarily by formal agricultural, logging, mining, and hydropower concessions and economic investment and social issues relating to civil war and land tenure. Reform of land laws, the link between natural resource extraction and civil war, and the allocation of agricultural concessions will influence the extent of future forest loss and degradation in Myanmar. The causal‐network analysis identified priority areas for policy interventions, for example, creating a public registry of land‐concession holders to deter corruption in concession allocation. We recommend application of this analytical approach to other countries, particularly those undergoing political transition, to inform policy interventions to reduce forest loss and degradation.  相似文献   
992.
Tanzania, arguably mainland Africa's most important nation for conservation, is losing habitat and natural resources rapidly. Moving away from a charcoal energy base and developing sustainable finance mechanisms for natural forests are critical to slowing persistent deforestation. Addressing governance and capacity deficits, including law enforcement, technical skills, and funding, across parts of the wildlife sector are key to effective wildlife protection. These changes could occur in tandem with bringing new models of natural resource management into play that include capacity building, corporate payment for ecosystem services, empowering nongovernmental organizations in law enforcement, greater private‐sector involvement, and novel community conservation strategies. The future of Tanzania's wildlife looks uncertain—as epitomized by the current elephant crisis—unless the country confronts issues of governance, embraces innovation, and fosters greater collaboration with the international community.  相似文献   
993.
Funding for species conservation is insufficient to meet the current challenges facing global biodiversity, yet many programs use expensive single‐species recovery actions and neglect broader management that addresses threatening processes. Arid Australia has the world's worst modern mammalian extinction record, largely attributable to competition from introduced herbivores, particularly European rabbits (Oryctolagus cuniculus) and predation by feral cats (Felis catus) and foxes (Vulpes vulpes). The biological control agent rabbit hemorrhagic disease virus (RHDV) was introduced to Australia in 1995 and resulted in dramatic, widespread rabbit suppression. We compared the area of occupancy and extent of occurrence of 4 extant species of small mammals before and after RHDV outbreak, relative to rainfall, sampling effort, and rabbit and predator populations. Despite low rainfall during the first 14 years after RHDV, 2 native rodents listed by the International Union for Conservation of Nature (IUCN), the dusky hopping‐mouse (Notomys fuscus) and plains mouse (Pseudomys australis), increased their extent of occurrence by 241–365%. A threatened marsupial micropredator, the crest‐tailed mulgara (Dasycercus cristicauda), underwent a 70‐fold increase in extent of occurrence and a 20‐fold increase in area of occupancy. Both bottom‐up and top‐down trophic effects were attributed to RHDV, namely decreased competition for food resources and declines in rabbit‐dependent predators. Based on these sustained increases, these 3 previously threatened species now qualify for threat‐category downgrading on the IUCN Red List. These recoveries are on a scale rarely documented in mammals and give impetus to programs aimed at targeted use of RHDV in Australia, rather than simply employing top‐down threat‐based management of arid ecosystems. Conservation programs that take big‐picture approaches to addressing threatening processes over large spatial scales should be prioritized to maximize return from scarce conservation funding. Further, these should be coupled with long‐term ecological monitoring, a critical tool in detecting and understanding complex ecosystem change.  相似文献   
994.
榄普一线500 k V线路由于地线覆冰严重,多次出现线路跳闸、地线断裂等事故,因此需要将架空地线取消。结合行波法和ATP-EMTP电磁暂态分析,对取消地线前后榄普一线的耐雷强度进行了仿真计算。计算结果表明,取消地线后雷击基本都变为绕击,并且绕击耐雷强度和反击耐雷强度均有所降低,需要采用其他防雷措施进行保护。  相似文献   
995.
A 1H-nuclear magnetic resonance (NMR) spectroscopy with multivariate analysis was applied to detect the toxicity of antiacetylcholinesterase insecticides, methomyl (methyl (1E)-N-(methylcarbamoyloxy)ethanimidothioate) and methidathion (3-(dimethoxyphosphinothioyl sulfanylmethyl)-5-methoxy-1,3,4-thiadiazol-2-one), using zebrafish (Danio rerio) and Chinese bleak (Aphyocypris chinensis). Generally, methomyl and methidathion have been believed not to highly accumulate in fish tissues. However, these pesticides showed their toxicity by altering patterns of whole-body metabolites in neurotransmitter balance, energy metabolism, oxidative stress, and muscle maintenance in low concentrations. We used Pearson correlation analysis to contextualize the metabolic markers in pesticide treated groups. We observed that the positive correlations of choline with acetate and betaine in untreated control were shifted to null correlations showing acetylcholinesterase specific toxicity. This research demonstrated the applicability and potential of NMR metabolomics in detecting toxic effects of insecticide with a modicum of concentrations in aquatic environment.  相似文献   
996.
The Adriatic and Ionian Region is an important area for both strategic maritime development and biodiversity conservation in the European Union (EU). However, given that both EU and non‐EU countries border the sea, multiple legal and regulatory frameworks operate at different scales, which can hinder the coordinated long‐term sustainable development of the region. Transboundary marine spatial planning can help overcome these challenges by building consensus on planning objectives and making the trade‐offs between biodiversity conservation and its influence on economically important sectors more explicit. We address this challenge by developing and testing 4 spatial prioritization strategies with the decision‐support tool Marxan, which meets targets for biodiversity conservation while minimizing impacts to users. We evaluated these strategies in terms of how priority areas shift under different scales of target setting (e.g., regional vs. country level). We also examined the trade‐off between cost‐efficiency and how equally solutions represent countries and maritime industries (n = 14) operating in the region with the protection‐equality metric. We found negligible differences in where priority conservation areas were located when we set targets for biodiversity at the regional versus country scale. Conversely, the prospective impacts on industries, when considered as costs to be minimized, were highly divergent across scenarios and biased the placement of protection toward industries located in isolation or where there were few other industries. We recommend underpinning future marine spatial planning efforts in the region through identification of areas of national significance, transboundary areas requiring cooperation between countries, and areas where impacts on maritime industries require careful consideration of the trade‐off between biodiversity conservation and socioeconomic objectives.  相似文献   
997.
Limited knowledge of dispersal for most organisms hampers effective connectivity conservation in fragmented landscapes. In forest ecosystems, deadwood‐dependent organisms (i.e., saproxylics) are negatively affected by forest management and degradation globally. We reviewed empirically established dispersal ecology of saproxylic insects and fungi. We focused on direct studies (e.g., mark‐recapture, radiotelemetry), field experiments, and population genetic analyses. We found 2 somewhat opposite results. Based on direct methods and experiments, dispersal is limited to within a few kilometers, whereas genetic studies showed little genetic structure over tens of kilometers, which indicates long‐distance dispersal. The extent of direct dispersal studies and field experiments was small and thus these studies could not have detected long‐distance dispersal. Particularly for fungi, more studies at management‐relevant scales (1–10 km) are needed. Genetic researchers used outdated markers, investigated few loci, and faced the inherent difficulties of inferring dispersal from genetic population structure. Although there were systematic and species‐specific differences in dispersal ability (fungi are better dispersers than insects), it seems that for both groups colonization and establishment, not dispersal per se, are limiting their occurrence at management‐relevant scales. Because most studies were on forest landscapes in Europe, particularly the boreal region, more data are needed from nonforested landscapes in which fragmentation effects are likely to be more pronounced. Given the potential for long‐distance dispersal and the logical necessity of habitat area being a more fundamental landscape attribute than the spatial arrangement of habitat patches (i.e., connectivity sensu strict), retaining high‐quality deadwood habitat is more important for saproxylic insects and fungi than explicit connectivity conservation in many cases.  相似文献   
998.
卫星降雨产品作为缺资料或无资料地区估算流域降雨径流的一种途径,适用性尚需大量实验研究。以澴水花园流域为研究区,综合评估了TRMM(3B42V7)、TRMM_RT(3B42V7)、PERSIANN CDR和CMORPH 4个卫星降雨产品在流域平均雨量计算与径流模拟中的精度,设置多方案与多种水文模拟情景全面检验各降雨产品的可靠性与适用性。研究表明:(1)在研究期2002~2013年,没有一个卫星降雨产品对所有精度评价指标均表现最优,PERSIANN始终表现为最差;(2)各卫星降雨产品对于不同年代和不同统计时段的精度差异明显,且一般汛期精度高于全年精度。各年代精度最高的卫星降雨产品在年与汛期尺度上与实测雨量相关系数均超过0.9;(3)各卫星降雨产品对有雨日降雨探测能力较强,但空报率较高,所有卫星降雨产品对于年最大1 d、3 d和7 d降雨估算误差较大,无法达到可利用精度;(4)采用卫星降雨产品进行径流模拟时,以相应的卫星降雨进行水文模型参数率定可获得更高的模拟精度。TRMM_RT与CMORPH日径流模拟精度较好,CMORPH月径流模拟精度较好。总体而言,CMORPH更适用于径流模拟。对于典型的3场大洪水模拟结果表明,TRMM_RT和CMORPH对洪峰与洪量(径流深)的模拟精度相对较高。  相似文献   
999.
Growing resource demands by humans, invasive species, natural hazards, and a changing climate have created broad‐scale impacts and the need for broader‐extent conservation activities that span ownerships and even political borders. Implementing regional‐scale conservation brings great challenges, and learning how to overcome these challenges is essential for maintaining biodiversity (i.e., richness and evenness of biological communities) and ecosystem functions and services across scales and borders in the face of system change. We administered an online survey to examine factors potentially driving perspectives of protected‐area (PA) managers regarding coordination with neighboring PAs and other stakeholders (i.e., stakeholder coordination) for conserving biodiversity and ecosystem services during the next decade within diverse regions across Europe. Although >70% (n = 58) of responding PA managers indicated that climate change and invasive species are relevant for their PAs, they gave <50% probability that these threats could be mitigated through stakeholder coordination. They thought there was a >60% probability (n = 85) that stakeholder coordination would take place with the aim to improve conservation outcomes. Consistent with the foundation on which many European PAs were established, managers viewed maintaining or enhancing biodiversity as the most important (>70%; n = 61) expected benefit. Other benefits included maintaining or enhancing human resources and environmental education (range of Bayesian credibility intervals [CIs] 57–93%). They thought the main barriers to stakeholder coordination were the lack of human and economic resources (CI 59–67% chance of hindering; n = 64) followed by communication and interstakeholder differences in political structures and laws (CI 51–64% probability of hindering). European policies and strategies that address these hindering factors could be particularly effective means of enabling implementation of green infrastructure networks in which PAs are the nodes.  相似文献   
1000.
The frequently discussed gap between conservation science and practice is manifest in the gap between spatial conservation prioritization plans and their implementation. We analyzed the research‐implementation gap of one zoning case by comparing results of a spatial prioritization analysis aimed at avoiding ecological impact of peat mining in a regional zoning process with the final zoning plan. We examined the relatively complex planning process to determine the gaps among research, zoning, and decision making. We quantified the ecological costs of the differing trade‐offs between ecological and socioeconomic factors included in the different zoning suggestions by comparing the landscape‐level loss of ecological features (species occurrences, habitat area, etc.) between the different solutions for spatial allocation of peat mining. We also discussed with the scientists and planners the reasons for differing zoning suggestions. The implemented plan differed from the scientists suggestion in that its focus was individual ecological features rather than all the ecological features for which there were data; planners and decision makers considered effects of peat mining on areas not included in the prioritization analysis; zoning was not truly seen as a resource‐allocation process and not emphasized in general minimizing ecological losses while satisfying economic needs (peat‐mining potential); and decision makers based their prioritization of sites on site‐level information showing high ecological value and on single legislative factors instead of finding a cost‐effective landscape‐level solution. We believe that if the zoning and decision‐making processes are very complex, then the usefulness of science‐based prioritization tools is likely to be reduced. Nevertheless, we found that high‐end tools were useful in clearly exposing trade‐offs between conservation and resource utilization.  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