全文获取类型
收费全文 | 457篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 39篇 |
废物处理 | 22篇 |
环保管理 | 82篇 |
综合类 | 103篇 |
基础理论 | 90篇 |
环境理论 | 2篇 |
污染及防治 | 79篇 |
评价与监测 | 25篇 |
社会与环境 | 16篇 |
灾害及防治 | 11篇 |
出版年
2023年 | 10篇 |
2021年 | 10篇 |
2020年 | 17篇 |
2019年 | 6篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 18篇 |
2015年 | 23篇 |
2014年 | 13篇 |
2013年 | 27篇 |
2012年 | 37篇 |
2011年 | 39篇 |
2010年 | 21篇 |
2009年 | 28篇 |
2008年 | 28篇 |
2007年 | 24篇 |
2006年 | 23篇 |
2005年 | 14篇 |
2004年 | 11篇 |
2003年 | 17篇 |
2002年 | 15篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 10篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有469条查询结果,搜索用时 62 毫秒
461.
PROBLEM: This study involved a quasi-induced exposure analysis of 4 years of crashes involving older drivers in the state of Kentucky. METHOD: Single- and multivehicle crashes were disaggregated according to the number of passengers: (a) no passenger, (b) one passenger, and (c) two or more passengers. RESULTS: Overall, the presence of two or more passengers was found to negatively impact the probability that drivers 75 years of age or older were at fault in crashes. Several potential factors were studied for interactive effects with passengers: vehicle occupant gender mix, time of the day, road curvature, grade, and number of lanes. The negative impact of passengers increased for some geometric road conditions. However, older drivers were found to be safer at night when carrying two or more passengers. The presence or absence of passengers was not found to affect the 65- to 74-year-old driver group. Groups of male vehicle occupants with a 75+ male driver were found to have high single-vehicle crash rates. IMPACT: These results are among the first to directly consider the effect of passengers on the crash-causing propensity of older drivers and the findings suggest more work is warranted to consider causes for the crash rate differences. 相似文献
462.
Summary Experimental reductions of productivity on feeding territories of Anna's hummingbirds (Calypte anna) decreased intrusion rate. This trend contrasts with the absence of strong correlations between intrusion rate and productivity in previous experimental studies. Consideration of sample sizes, productivity rates, and time-dependent influences on intrusion rate (e. g., day-to-day changes in weather) indicates that this difference resulted from the more natural spatial distribution of artificial flowers used in this study.
Offprint requests to: P.W. Ewald 相似文献
463.
Determining the viability of marine protists using a combination of vital, fluorescent stains 总被引:1,自引:0,他引:1
Determining the viability of protists and small microzooplankton has long been a focus of studies in marine biology and ecology.
It is especially relevant in the issue of shipborne invasive species, and impending international guidelines and various national
regulations on the allowable concentrations of organisms in discharged ballast water have spurred the growth of an industry
that develops and manufactures ballast water management systems. The success of management systems and ability of ships to
meet ballast water discharge standards is determined by the number of viable organisms in treated water. Here, we propose
combining two vital, fluorescent stains (fluorescein diacetate [FDA] and 5-chloromethylfluorescein diacetate [CMFDA]) with
direct microscopic observation to enumerate viable organisms ≥10 and <50 μm in minimum dimension (nominally protists). This
approach was validated in four locations in the United States to determine the efficacy of the stains. Although the accuracy
of the stains varied by geographic location and the taxonomic composition of the planktonic assemblage, combining fluorescent
stains is a robust, powerful tool that can be optimized for the species present at each location. While this method was developed
for analyzing viable organisms in treated ballast water, it may also be used or adapted for any field of research that examines
a broad taxonomic range of autotrophic and heterotrophic plankton. 相似文献
464.
After nearly a century of height suppression, willows (Salix spp.) in the northern range of Yellowstone National Park, U.S.A., are increasing in height growth as a possible consequence of wolf (Canis lupus) restoration, climate change, or other factors. Regardless of the drivers, the recent release of this rare but important habitat type could have significant implications for associated songbirds that are exhibiting declines in the region. Our objective was to evaluate bird response to releasing willows by comparing willow structure and bird community composition across three willow growth conditions: height suppressed, recently released, and previously tall (i.e., tall prior to the height increase of released willows). Released and previously tall willows exhibited high and similar vertical structure, but released willows were significantly lower in horizontal structure. Suppressed willows were significantly shorter and lower in horizontal cover than released or previously tall willows. Bird richness increased along a gradient from lowest in suppressed to highest in previously tall willows, but abundance and diversity were similar between released and previously tall willows, despite lower horizontal cover in the released condition. Common Yellowthroat (Geothlypis trichas) and Lincoln's Sparrow (Melospiza lincolnii) were found in all three growth conditions; however, Yellow Warbler (Dendroica petechia), Warbling Vireo (Vireo gilvus), Willow Flycatcher (Empidonax traillii), and Song Sparrow (Melospiza melodii) were present in released and previously tall willows only. Wilson's Warbler (Wilsonia pusilla) was found in previously tall willows only, appearing to specialize on tall, dense willows. The results of our a priori habitat models indicated that foliage height diversity was the primary driver of bird richness, abundance, and diversity. These results indicate that vertical structure was a more important driver of bird community variables than horizontal structure and that riparian and willow-dependent bird species have responded positively to increased willow growth in the region. 相似文献
465.
466.
Mackechnie C Maskell L Norton L Roy D 《Journal of environmental monitoring : JEM》2011,13(10):2687-2691
Environmental monitoring is essential for assessing the current state of the environment, measuring impacts of environmental pressures and providing evidence to government. Recent UK government announcements have indicated an increased role for 'Big Society' in monitoring. In this paper, we review available literature concerning the use of citizen science for monitoring, present examples of successful volunteer monitoring work and highlight important issues surrounding the use of volunteers. We argue that in order to ensure that environmental monitoring continues to be effective it is important to learn from examples where volunteers are currently used, acknowledging constraints and identifying potential approaches which will help to maximise both their engagement and data quality. Effective partnerships between environmental monitoring organisations and volunteers may thus aid the UK in developing robust coordinated monitoring systems that will be less vulnerable to funding variances. 相似文献
467.
Modeling Agricultural Nonpoint Source Pollution Using a Geographic Information System Approach 总被引:3,自引:0,他引:3
Agricultural non-point source (NPS) pollution, primarily sediment and nutrients, is the leading source of water-quality impacts to surface waters in North America. The overall goal of this study was to develop geographic information system (GIS) protocols to facilitate the spatial and temporal modeling of changes in soils, hydrology, and land-cover change at the watershed scale. In the first part of this article, we describe the use of GIS to spatially integrate watershed scale data on soil erodibility, land use, and runoff for the assessment of potential source areas within an intensively agricultural watershed. The agricultural non-point source pollution (AGNPS) model was used in the Muddy Creek, Ontario, watershed to evaluate the effectiveness of management strategies in decreasing sediment and nutrient [phosphorus (P)] pollution. This analysis was accompanied by the measurement of water-quality parameters (dissolved oxygen, pH, hardness, alkalinity, and turbidity) as well as sediment and P loadings to the creek. Practices aimed at increasing year-round soil cover would be most effective in decreasing sediment and P losses in this watershed. In the second part of this article, we describe a method for characterizing land-cover change in a dynamic urban fringe watershed. The GIS method we developed for the Blackberry Creek, Illinois, watershed will allow us to better account for temporal changes in land use, specifically corn and soybean cover, on an annual basis and to improve on the modeling of watershed processes shown for the Muddy Creek watershed. Our model can be used at different levels of planning with minimal data preprocessing, easily accessible data, and adjustable output scales. 相似文献
468.
Torpor and basking in a small arid zone marsupial 总被引:3,自引:3,他引:0
The high energetic cost associated with endothermic rewarming from torpor is widely seen as a major disadvantage of torpor.
We tested the hypothesis that small arid zone marsupials, which have limited access to energy in the form of food but ample
access to solar radiation, employ basking to facilitate arousal from torpor and reduce the costs of rewarming. We investigated
torpor patterns and basking behaviour in free-ranging fat-tailed dunnarts Sminthopsis crassicaudata (10 g) in autumn and winter using small, internal temperature-sensitive transmitters. Torpid animals emerged from their resting
sites in cracking soil at ∼1000 h with body temperatures as low as 14.6°C and positioned themselves in the sun throughout
the rewarming process. On average, torpor duration in autumn was shorter, and basking was less pronounced in autumn than in
winter. These are the first observations of basking during rewarming in S. crassicaudata and only the second direct evidence of basking in a torpid mammal for the reduction of energetic costs during arousal from
torpor and normothermia. Our findings suggest that although overlooked in the past, basking may be widely distributed amongst
heterothermic mammals. Therefore, the energetic benefits from torpor use in wild animals may currently be underestimated. 相似文献
469.
Lisa A. Totten Georgiy Stenchikov Cari L. Gigliotti Nilesh Lahoti Steven J. Eisenreich 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):7940-7952
Atmospheric transport and deposition of polychlorinated biphenyls (PCBs) is an important problem for ecosystems around the world. Data from several monitoring networks demonstrate that atmospheric PCB concentrations are dramatically elevated in urban areas compared to rural or background regions, such that these urban emissions of PCBs support the regional and global transport and deposition of PCBs to more remote areas. Identifying and controlling the sources of urban atmospheric PCBs is thus essential in minimizing the regional and global transport and deposition of these compounds. From December 1999 to November 2000, gas-phase PCB concentrations were measured at two monitoring locations, 8 km apart, within the New York City metropolitan area, at Jersey City and Bayonne, NJ. Concentrations, congener patterns, and temporal patterns of PCBs differ dramatically at the two sites, suggesting that a significant source of atmospheric PCBs exists within 8 km of the Bayonne site, resulting in spikes in gas-phase PCB concentration at Bayonne that are not observed at Jersey City. The Regional Atmospheric Model System (RAMS) coupled with the Hybrid Particle and Concentration Transport model (HYPACT) was used to estimate that the PCB source near Bayonne emits a flux of ΣPCBs on the order of 100 g d−1. Extrapolation of this source magnitude to the area of New York City suggests that this urban area emits at least 300 kg yr−1 ΣPCBs to the regional atmosphere, similar in magnitude to the flow of ΣPCB out of the Upper Hudson River into the New York/New Jersey Harbor. 相似文献