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   1124篇
  免费   88篇
  国内免费   170篇
安全科学   178篇
废物处理   14篇
环保管理   130篇
综合类   362篇
基础理论   322篇
环境理论   1篇
污染及防治   211篇
评价与监测   17篇
社会与环境   122篇
灾害及防治   25篇
  2024年   1篇
  2023年   20篇
  2022年   33篇
  2021年   41篇
  2020年   44篇
  2019年   38篇
  2018年   30篇
  2017年   37篇
  2016年   44篇
  2015年   48篇
  2014年   38篇
  2013年   80篇
  2012年   91篇
  2011年   134篇
  2010年   68篇
  2009年   93篇
  2008年   73篇
  2007年   73篇
  2006年   83篇
  2005年   43篇
  2004年   43篇
  2003年   45篇
  2002年   37篇
  2001年   28篇
  2000年   26篇
  1999年   17篇
  1998年   7篇
  1997年   14篇
  1996年   15篇
  1995年   12篇
  1994年   7篇
  1993年   5篇
  1992年   4篇
  1991年   2篇
  1990年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1984年   2篇
  1981年   1篇
  1980年   1篇
排序方式: 共有1382条查询结果,搜索用时 140 毫秒
41.
The concept of time perspective balance has attracted increased attention from scholars in the past decade, reflected in published evidence suggesting positive outcomes ranging from enhanced mood to life satisfaction for those individuals possessing balance among their past, present, and future time perspectives, and assumedly able to shift their time perspective to match situational demands. In this paper, we consider the notion of time perspective balance in an organizational setting within which much consequential adaptation often occurs—the team environment—and explore different configurations of time perspective balance in teams facing dynamic task contexts. Drawing from work on situational awareness, we first consider the mechanism by which time perspective balance likely influences individual adaptation in dynamic task-focused situations. Next, we postulate what types of team configurations—ones with more balanced time perspective uniformity or ones with more time perspective variety—might be more appropriate in dynamic contexts given key team conditions. We illustrate our analysis with examples from healthcare team settings and offer ideas for future research.  相似文献   
42.
Spatial synchrony, defined as the correlated fluctuations in abundance of spatially separated populations, can be caused by regional fluctuations in natural and anthropogenic environmental population drivers. Investigations into the geography of synchrony can provide useful insight to inform conservation planning efforts by revealing regions of common population drivers and metapopulation extinction vulnerability. We examined the geography of spatial synchrony and decadal changes in these patterns for grassland birds in the United States and Canada, which are experiencing widespread and persistent population declines. We used Bayesian hierarchical models and over 50 years of abundance data from the North American Breeding Bird Survey to generate population indices within a 2° latitude by 2° longitude grid. We computed and mapped mean local spatial synchrony for each cell (mean detrended correlation of the index among neighboring cells), along with associated uncertainty, for 19 species in 2, 26-year periods, 1968–1993 and 1994–2019. Grassland birds were predicted to increase in spatial synchrony where agricultural intensification, climate change, or interactions between the 2 increased. We found no evidence of an overall increase in synchrony among grassland bird species. However, based on the geography of these changes, there was considerable spatial heterogeneity within species. Averaging across species, we identified clusters of increasing spatial synchrony in the Prairie Pothole and Shortgrass Prairie regions and a region of decreasing spatial synchrony in the eastern United States. Our approach has the potential to inform continental-scale conservation planning by adding an additional layer of relevant information to species status assessments and spatial prioritization of policy and management actions. Our work adds to a growing literature suggesting that global change may result in shifting patterns of spatial synchrony in population dynamics across taxa with broad implications for biodiversity conservation.  相似文献   
43.
近年来,长三角地区灰霾天气持续增多,空气细颗粒物污染问题日益突出。基于2013年1月至2015年5月长三角地区及周边缓冲区内共214个空气质量监测站点PM2.5逐时监测数据,运用普通克里金插值方法,从年、季、月尺度上分析了PM2.5的空间分布格局和时间动态变化。结果表明:(1)2 a来,长三角地区PM2.5浓度空间分布明显呈现整体北部高南部低,局部地区略有突出的分布特征;长三角地区PM2.5浓度年均值为57.08μg/m3;其中,江苏省PM2.5的年均值为三省市最高,为65.84μg/m3;其次为上海市,年均值为53.87μg/m3;浙江省PM2.5的年均值较小,为51.53μg/m3。(2)从季节尺度分析,长三角地区PM2.5浓度变化表现出冬春季高,夏秋季低的变化趋势;这与区域内冬季风向来源、降水稀少、气象扩散条件差有着密切的关系; (3)长三角地区月浓度变化大致呈U形分布; 12月份PM2.5浓度最高; 3月份以后, PM2.5浓度开始呈逐步下降趋势;在5~9月份,区域PM2.5处于"U"字的谷底,其中6月份夏收时期秸秆焚烧、气象等因素导致PM2.5浓度有略微升高;进入10月份后迅速攀升,且11、12月份呈现持续升高态势。  相似文献   
44.
绿色发展是我国"十三五"时期五大发展理念之一,是解决我国发展与保护矛盾的根本途径。系统动力学是模拟宏观社会经济发展趋势和政策效力的常用分析工具,本文对系统动力学在中国区域绿色发展政策仿真中的应用进行了梳理。研究显示:系统动力学应用的区域范围方面,该方法全面应用于从国家直至县域等各个尺度的区域绿色发展研究,区域绿色发展通常被分解为经济、社会、资源、环境等子系统;应用的主要领域方面,水土资源、能源、水环境、固废治理、绿色产业等领域应用较多,大气环境、绿色消费等领域应用相对较少;方法的改进和完善方面,软系统分析法、各类优化方法和地理信息系统与系统动力学的集成应用日益普遍。文末根据文献梳理情况,提出未来应在决策变量设计、历史数据挖掘、环境系统对经济系统的反馈等方面进行方法改进。  相似文献   
45.
This paper explores the relationship between government spending and environmental quality using panel data for 94 countries for the period 1970–2008. We identify and estimate three distinct channels that comprise the total direct effect of government expenditure on air pollution, namely a marginal effect, an effect conditional on economic growth and an effect conditional on institutional quality. Since adjustment rate of emissions to their equilibrium level is slow due to technological and institutional reasons, we explicitly take into account dynamics by applying appropriate econometric methods. The results demonstrate that there is a significant alleviating direct effect of government expenditure on SO2 and NOx emissions, which increases with the level of economic growth and democracy. However, there is no evidence of a significant effect on pollutants with more global impact on the environment and human health, like N2O and CO2, implying that the adoption of international environmental treaties is required in this case.  相似文献   
46.
Eradication of introduced mammalian predators from islands has become increasingly common, with over 800 successful projects around the world. Historically, introduced predators extirpated or reduced the size of many seabird populations, changing the dynamics of entire island ecosystems. Although the primary outcome of many eradication projects is the restoration of affected seabird populations, natural population responses are rarely documented and mechanisms are poorly understood. We used a generic model of seabird colony growth to identify key predictor variables relevant to recovery or recolonization. We used generalized linear mixed models to test the importance of these variables in driving seabird population responses after predator eradication on islands around New Zealand. The most influential variable affecting recolonization of seabirds around New Zealand was the distance to a source population, with few cases of recolonization without a source population ≤25 km away. Colony growth was most affected by metapopulation status; there was little colony growth in species with a declining status. These characteristics may facilitate the prioritization of newly predator‐free islands for active management. Although we found some evidence documenting natural recovery, generally this topic was understudied. Our results suggest that in order to guide management strategies, more effort should be allocated to monitoring wildlife response after eradication. Conductores de la Recuperación de Poblaciones de Aves Marinas en Islas de Nueva Zelanda después de la Erradicación de Depredadores  相似文献   
47.
Conflicts between local people's livelihoods and conservation have led to many unsuccessful conservation efforts and have stimulated debates on policies that might simultaneously promote sustainable management of protected areas and improve the living conditions of local people. Many government‐sponsored payments‐for‐ecosystem‐services (PES) schemes have been implemented around the world. However, few empirical assessments of their effectiveness have been conducted, and even fewer assessments have directly measured their effects on ecosystem services. We conducted an empirical and spatially explicit assessment of the conservation effectiveness of one of the world's largest PES programs through the use of a long‐term empirical data set, a satellite‐based habitat model, and spatial autoregressive analyses on direct measures of change in an ecosystem service (i.e., the provision of wildlife species habitat). Giant panda (Ailuropoda melanoleuca) habitat improved in Wolong Nature Reserve of China after the implementation of the Natural Forest Conservation Program. The improvement was more pronounced in areas monitored by local residents than those monitored by the local government, but only when a higher payment was provided. Our results suggest that the effectiveness of a PES program depends on who receives the payment and on whether the payment provides sufficient incentives. As engagement of local residents has not been incorporated in many conservation strategies elsewhere in China or around the world, our results also suggest that using an incentive‐based strategy as a complement to command‐and‐control, community‐ and norm‐based strategies may help achieve greater conservation effectiveness and provide a potential solution for the park versus people conflict.  相似文献   
48.
By rapidly modifying key habitat components, habitat restoration is at risk of producing attractive cues for animals without providing habitats of sufficient quality. As such, individual fitness components, such as reproduction, could be reduced and restored habitats could become ecological traps. This risk notably appears by using artificial constructions in restoration projects, yet few studies have evaluated their efficacy in a robust way. We investigated this by analyzing 154 islets that were created or restored to improve the conservation status of 7 colonial Laridae species in the South of France. From 2007 to 2016, we compared occupancy dynamics and breeding parameters of these species between the restored sites and 846 unmanaged nesting sites. We also explored species’ preference for different nesting site characteristics and their respective effect on breeding parameters. Restored nesting sites were 2–9 times as attractive as unmanaged sites for all species except the Black-headed Gull (Chroicocephalus ridibundus). Colonization probability was up to 100 times higher in sites already used by other species the previous year and increased with distance to the shore until >0.2 when distance was over 250 m. Abandonment probability was 29–70% lower when breeding was successful the previous year in all species except the Sandwich Tern (Thalasseus sandvicensis). Productivity and breeding success probability were 2 times higher on managed sites. Distance from the shore was an important attractive characteristic of artificial nesting sites in all species. Other nesting site characteristics had species-specific effects on colonization, abandonment, and breeding success. Our results indicate that managed nesting sites are successful conservation tools for colonial Laridae in the Mediterranean and do not act as ecological traps. Our study showed that testing the ecological trap hypothesis is a robust way to evaluate the success of restoration projects of breeding habitats.  相似文献   
49.
Ramus K  Kopinke FD  Georgi A 《Chemosphere》2012,86(2):138-143
The effect of dissolved humic substances (DHS) on the rate of water-gas exchange of two volatile organic compounds was studied under various conditions of agitation intensity, solution pH and ionic strength. Mass-transfer coefficients were determined from the rate of depletion of model compounds from an apparatus containing a stirred aqueous solution with continuous purging of the headspace above the solution (dynamic system). Under these conditions, the overall transfer rate is controlled by the mass-transfer resistance on the water side of the water-gas interface. The experimental results show that the presence of DHS hinders the transport of the organic molecules from the water into the gas phase under all investigated conditions. Mass-transfer coefficients were significantly reduced even by low, environmentally relevant concentrations of DHS. The retardation effect increased with increasing DHS concentration. The magnitude of the retardation effect on water-gas exchange was compared for Suwannee River fulvic and humic acids, a commercially available leonardite humic acid and two synthetic surfactants. The observed results are in accordance with the concept of hydrodynamic effects. Surface pressure forces due to surface film formation change the hydrodynamic characteristics of water motion at the water-air interface and thus impede surface renewal.  相似文献   
50.
Modifications of black carbons and their influence on pyrene sorption   总被引:2,自引:0,他引:2  
Zhang W  Wang L  Sun H 《Chemosphere》2011,85(8):1306-1311
Sorption of pyrene on black carbons (BCs) obtained by heating sawdust at two temperatures (400 and 700 °C, denoted as 400BC and 700BC, respectively), as well as on modified BCs (via oxidation, oximation, and hydrolysis) was studied to investigate the role of BC structural characteristics in sorption of hydrophobic organic compounds. Pyrene was bound strongly by 700BC and 400BC, with organic carbon normalized distribution coefficients (Koc) of 105.04-105.86 and 104.65-105.16, respectively, at equilibrium pyrene concentrations of 10-100 μg L−1. Both chemical composition and pore distribution of the two BCs changed after modifications, which led to changes in their sorption characteristics for pyrene. After modifications, the linearity of pyrene sorption isotherm increased for 700BC but decreased for 400BC. For 700BC, both oxidation and oximation reduced pyrene sorption, with Koc decreasing by 69.1-73.7% and 18.7-33.9%, respectively, whereas hydrolysis did not exert a significant influence. For 400BC, oxidation and hydrolysis reduced Koc by 2.28-25.9% and 29.2-33.9%, respectively, while oximation increased Koc. In most cases, the change in sorption capacity could be explained by the changes in C content and type, polarity, surface area, and micropore volume of the BCs; however, the role of conformation (the accessibility to sorption sites) could not be ignored.  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