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   647篇
  免费   32篇
  国内免费   9篇
安全科学   30篇
废物处理   19篇
环保管理   159篇
综合类   88篇
基础理论   221篇
污染及防治   113篇
评价与监测   32篇
社会与环境   16篇
灾害及防治   10篇
  2023年   5篇
  2022年   17篇
  2021年   13篇
  2020年   23篇
  2019年   18篇
  2018年   21篇
  2017年   39篇
  2016年   24篇
  2015年   23篇
  2014年   29篇
  2013年   44篇
  2012年   41篇
  2011年   47篇
  2010年   38篇
  2009年   32篇
  2008年   34篇
  2007年   36篇
  2006年   26篇
  2005年   20篇
  2004年   19篇
  2003年   21篇
  2002年   17篇
  2001年   10篇
  2000年   7篇
  1999年   10篇
  1998年   9篇
  1997年   10篇
  1996年   3篇
  1995年   7篇
  1994年   5篇
  1993年   4篇
  1992年   4篇
  1991年   2篇
  1990年   4篇
  1989年   6篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   4篇
  1982年   3篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
  1976年   1篇
  1971年   1篇
排序方式: 共有688条查询结果,搜索用时 281 毫秒
41.
Invasive species, range-expanding species, genetically modified organisms (GMOs), synthetic organisms, and emerging pathogens increasingly affect the human environment. We propose a framework that allows comparison of consecutive stages that such novel organisms go through. The framework provides a common terminology for novel organisms, facilitating knowledge exchange among researchers, managers, and policy makers that work on, or have to make effective decisions about, novel organisms. The framework also indicates that knowledge about the causes and consequences of stage transitions for the better studied novel organisms, such as invasive species, can be transferred to more poorly studied ones, such as GMOs and emerging pathogens. Finally, the framework advances understanding of how climate change can affect the establishment, spread, and impacts of novel organisms, and how biodiversity affects, and is affected by, novel organisms.  相似文献   
42.
Bone metabolism is a tightly regulated process that controls bone remodeling and repair in addition to maintaining circulating calcium and phosphate levels. It has been shown that certain organohalogen contaminants may adversely impact bone tissue metabolism and structure in wildlife species. However, exceedingly few studies have addressed the bone-related effects of organohalogen exposure in birds. The objective of the present study was to investigate the associations between markers of bone metabolism and structural integrity, and concentrations of established and current-use halogenated flame retardants (FRs) in ring-billed gulls (Larus delawarensis) nesting in a known FR hotspot area in the St. Lawrence River (Montreal, Canada). Bone metabolism was assessed using plasma calcium and inorganic phosphate levels, and alkaline phophatase activity, while bone (tarsus; trabecular and cortical sections) structure quality was examined using the percentage of bone tissue comprised in the total bone volume (Bv/Tv) and bone mineral density (BMD). Bv/Tv and BMD of the tarsus tended (not significant) to be positively associated with circulating calcium levels in male ring-billed gulls. Moreover, concentrations of FRs in male bird liver (brominated diphenyl ether (BDE)-154, -183, -201, and -209) and plasma (BDE-209) were negatively correlated with trabecular and cortical BMD of the tarsus. These correlative associations may suggest light demineralization of bone tissue associated with FR exposure in male ring-billed gulls. Present findings provide some evidence that bone (tarsus) metabolism and mineral composition may be impacted in high FR-exposed (mainly to PBDEs) ring-billed gulls breeding in the highly urbanized Montreal region.  相似文献   
43.

Problem

Motorized recreational vehicle (MRV)-related injuries can result in severe medical and financial consequences. The objective of this study was to describe the epidemiology, and clinical and financial impact of MRV-related injuries in Ohio.

Method

Probabilistically linked statewide Emergency Medical Services (EMS) and hospital (inpatient and emergency department) data for 2003 and 2004 were examined. Record pairs with a MRV-related E-code (E821-E823, E825) were included in this study.

Results

There were 2,893 patients with MRV-related injuries, who had linked EMS and hospital records, resulting in more than $15 million in hospital charges and 1,921 inpatient days of hospitalization. The male-to-female ratio was nearly 4:1, and 19% were younger than 16. Almost 82% of cases were not wearing a helmet; there was a trend of decreasing helmet use with increasing age. Mean (SE) inpatient hospital charges and length of stay (LOS) were $22,218 ($1,290) and 3.8 (0.2) days, respectively. The mean (SE) Injury Severity Score (ISS) for inpatients was 9.2 (0.4). Individuals injured on a street/highway were 3.20 times more likely to sustain an ISS ≥ 16 (95% CI: 1.03, 9.88; p = 0.044) and 3.05 times more likely to sustain a traumatic brain injury (TBI) (95% CI: 1.17, 7.94; p = 0.024) than those who were injured at a place designated for sport or recreation. Children aged 12 to 15 and young adults aged 16 to 25 were 2.47 and 2.14 times more likely, respectively, to sustain a TBI than adults aged 36 or older (aged 12 to 15: 95% CI: 1.13, 5.38; p = 0.024; aged 16 to 25: 95% CI: 1.26, 3.64; p = 0.005). Higher ISS was associated with both higher total charges (p < 0.001) and longer LOS (p < 0.001).

Discussion

This study demonstrates that MRV-related injuries are an important public health problem in Ohio, with a substantial clinical and financial impact.

Impact on Industry

Enactment and enforcement of statewide MRV safety legislation and training of MRV users offer valuable opportunities to prevent these costly injuries.  相似文献   
44.
PROBLEM: Federal policy recommends environmental strategies as part of a comprehensive workplace violence program in healthcare and social services. The purpose of this project was to contribute specific, evidence-based guidance to the healthcare and social services employer communities regarding the use of environmental design to prevent violence. METHOD: A retrospective record review was conducted of environmental evaluations that were performed by an architect in two Participatory Action Research (PAR) projects for workplace violence prevention in 2000 and, in the second project in 2005. Ten facility environmental evaluation reports along with staff focus group reports from these facilities were analyzed to categorize environmental risk factors for Type II workplace violence. RESULTS: Findings were grouped according to their impact on access control, the ability to observe patients (natural surveillance), patient and worker safety (territoriality), and activity support. DISCUSSION: The environmental assessment findings reveal design and security issues that, if corrected, would improve safety and security of staff, patients, and visitors and reduce fear and unpredictability. IMPACT ON INDUSTRY: Healthcare and social assistance employers can improve the effectiveness of violence prevention efforts by including an environmental assessment with complementary hazard controls.  相似文献   
45.
46.
Land management decisions have extensively modified land use and land cover in the Zambezi Region. These decisions are influenced by land tenure classifications, legislation, and livelihoods. Land use and land cover change is an important indicator for quantifying the effectiveness of different land management strategies. However, there has been no evidence on whether protected or communal land tenure is more affected by land use and land cover changes in southern Africa and particularly Namibia. Our study attempted to fill this gap by analyzing the relationship between land use and land cover change and land tenure regimes stratified according to protected and communal area in the Zambezi Region. Multi-temporal Landsat TM and ETM+ imagery were used to determine the temporal dynamics of land use and land cover change from 1984 to 2010. The landscape showed distinctive modifications over the study period; broad trends include the increase in forest land after 1991. However, changes were not uniform across the study areas. Two landscape development stages were deduced: (1) 1984–1991 represented high deforestation and gradual increase in shrub land; (2) 1991–2000 and 2000–2010 represented lower deforestation and slower agropastoral expansion. The results further show clear patterns of the dynamics, magnitude, and direction of land use and land cover change by tenure regime. The study concluded that land tenure has a direct impact on land use and land cover, since it may restrict some activities carried out on the land in the Zambezi Region.  相似文献   
47.
Forty-eight air-filter samples (PM10) were analysed to identify the concentration level of partially leached metals (PLMs; As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and V) from Puebla City, México. Samples were collected during 2008 from four monitoring sites: (1) Tecnológico (TEC), (2) Ninfas (NIN), (3) Hermanos Serdán (HS) and (4) Agua Santa (AS). The results indicate that in TEC, As (avg. 424 ng m?3), V (avg. 19.2 ng m?3), Fe (avg. 1,202 ng m?3), Cu (avg. 86.6 ng m?3), Cr (41.9 ng m?3) and Ni (18.6 ng m?3) are on the higher side than other populated regions around the world. The enrichment of PLMs is due to the industrial complexes generating huge dust particles involving various operations. The results are supported by the correlation of metals (Mn, Cd and Co) with Fe indicating its anthropogenic origin and likewise, As with Cd, Co, Fe, Mn, Pb and V. The separate cluster of As, Fe and Mn clearly signifies that it is due to continuous eruption of fumaroles from the active volcano Popocatépetl in the region.  相似文献   
48.
Fishing and habitat degradation have increased the extinction risk of sharks, and conservation strategies recognize that survival of juveniles is critical for the effective management of shark populations. Despite the rapid expansion of marine protected areas (MPAs) globally, the paucity of shark‐monitoring data on large scales (100s–1000s km) means that the effectiveness of MPAs in halting shark declines remains unclear. Using data collected by baited remote underwater video systems (BRUVS) in northwestern Australia, we developed generalized linear models to elucidate the ecological drivers of habitat suitability for juvenile sharks. We assessed occurrence patterns at the order and species levels. We included all juvenile sharks sampled and the 3 most abundant species sampled separately (grey reef [Carcharhinus amblyrhynchos], sandbar [Carcharhinus plumbeus], and whitetip reef sharks [Triaenodon obesus]). We predicted the occurrence of juvenile sharks across 490,515 km2 of coastal waters and quantified the representation of highly suitable habitats within MPAs. Our species‐level models had higher accuracy (? ≥ 0.69) and deviance explained (≥48%) than our order‐level model (? = 0.36 and deviance explained of 10%). Maps of predicted occurrence revealed different species‐specific patterns of highly suitable habitat. These differences likely reflect different physiological or resource requirements between individual species and validate concerns over the utility of conservation targets based on aggregate species groups as opposed to a species‐focused approach. Highly suitable habitats were poorly represented in MPAs with the most restrictions on extractive activities. This spatial mismatch possibly indicates a lack of explicit conservation targets and information on species distribution during the planning process. Non‐extractive BRUVS provided a useful platform for building the suitability models across large scales to assist conservation planning across multiple maritime jurisdictions, and our approach provides a simple for method for testing the effectiveness of MPAs.  相似文献   
49.
50.
This paper provides a performance evaluation of the real-time, CONUS-scale National Air Quality Forecast Capability (NAQFC) that supported, in part, its transition into operational status. This evaluation focuses primarily on discrete forecasts for the maximum 8-h O3 concentrations covering the 4-month period, June through September, 2007, using measurements obtained from EPA's AIRNow network. Results indicate that the 2007 NAQFC performed as well or better than previous configurations, despite the expansion of the forecast domain into the western half of the nation that is dominated by complex terrain. The mean, domain-wide, season-long correlation was 0.70. When examined over time, the domain-wide correlations exhibit a fairly consistent nature, with values exceeding 0.60 (0.70) over 90% (55%) of the days. The NAQFC systematically over-predicted the 8-h O3 concentrations, continuing a trend established by earlier NAQFC configurations, though to a lesser degree. The summer-long mean forecast value of 53.2 ppb was 4.2 ppb higher than the observed value, resulting in a domain-wide Normalized Mean Bias (NMB) of 8.7%. Most of the over-prediction is associated with observed concentrations less than 50 ppb. In fact the model tends to under-predict when concentrations exceed 70 ppb. As with the bias, the error associated with the latest configuration was also lower. The summer-long Root Mean Square Error of 13.0 ppb (Normalized Mean Error (NME) = 20.4%) represented marked improvements over earlier forecasts. Examination of the spatial distribution of both the NMB and NME reveals that the NAQFC was generally within 25% for the NME and 25% for the NMB over a majority of the domain. Several areas of poorer performance, where the NMB and NME often exceed 25% and in some cases 50%, were noted. These areas include southern California, where the NAQFC tended to under-predict concentrations (especially on weekends) and the southeast Atlantic and Gulf coasts regions, where the model over-predicted. Subsequent analysis revealed that the incorrect temporal allocation of precursor emissions was likely the source of the under-prediction in southern California, while inaccurate simulation of PBL heights likely contributed to the over-prediction in the coastal regions.  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