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   250篇
  免费   8篇
  国内免费   2篇
安全科学   22篇
废物处理   11篇
环保管理   50篇
综合类   26篇
基础理论   72篇
污染及防治   51篇
评价与监测   10篇
社会与环境   8篇
灾害及防治   10篇
  2021年   2篇
  2020年   2篇
  2019年   4篇
  2018年   6篇
  2017年   7篇
  2016年   7篇
  2015年   12篇
  2014年   5篇
  2013年   19篇
  2012年   9篇
  2011年   19篇
  2010年   8篇
  2009年   6篇
  2008年   10篇
  2007年   8篇
  2006年   10篇
  2005年   8篇
  2004年   9篇
  2003年   6篇
  2002年   11篇
  2001年   3篇
  2000年   7篇
  1999年   6篇
  1998年   2篇
  1997年   3篇
  1996年   2篇
  1995年   3篇
  1994年   4篇
  1993年   4篇
  1992年   3篇
  1991年   3篇
  1988年   1篇
  1987年   2篇
  1985年   6篇
  1984年   6篇
  1982年   2篇
  1981年   3篇
  1980年   4篇
  1979年   4篇
  1978年   3篇
  1977年   5篇
  1976年   2篇
  1975年   3篇
  1974年   3篇
  1972年   2篇
  1971年   1篇
  1970年   3篇
  1969年   1篇
  1960年   1篇
排序方式: 共有260条查询结果,搜索用时 515 毫秒
31.
The prevalence of diversity training has not been matched by empirical research on its effectiveness. Among the most notable gaps are an absence of attention to its impact on discrimination and limited consideration of organizational‐level factors. Results from employee surveys across 395 healthcare organizations reveal an effect of the extent of diversity training in organizations on ethnic minorities' experiences of discrimination. In addition, the results demonstrate that the consequences of ethnic discrimination for individuals' job attitudes are influenced by organizational‐level phenomenon. These findings highlight the importance of attending to ethnic discrimination as an outcome of diversity training with implications for employee attitudes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
32.
Background: Alcohol use is pervasive among motorists on the road in Ghana; however, we do not know the extent to which this behavior is implicated in road accidents in this country.

Objectives: The main objective of this research was to establish the prevalence of alcohol in the blood of nonfatally injured casualties in the emergency departments (EDs) in northern Ghana.

Method: Participants were injured road traffic crash victims, namely, pedestrians, cyclists, motorcyclists, and drivers seeking treatment at an ED. The study sites were 2 level III trauma centers located in Wa and Bolgatanga. Participants were screened for alcohol followed by breath tests for positive participants using breathalyzers.

Results: Two hundred and sixty-two accident victims visited EDs, 58% of whom were in Wa. Among the victims, 41% were hospitalized and 57% experienced slight injuries. The vast majority (76%) of the casualties were motorcyclists, 13% were pedestrians, 8% were cyclists, and 2% were drivers. Casualties who had detectable alcohol in their blood were predominantly vulnerable road users. In all, 34% of participants had detectable blood alcohol concentrations (BACs) and the mean BAC for all casualties who tested positive and could give definitive BACs was 0.2265 (226 mg/dl). The prevalence of alcohol use was 53% among cyclists, 34% among motorcyclists, 21% among pedestrians, and 17% among drivers. Male casualties were more likely to test positive for alcohol than females. In addition, the prevalence of alcohol was significantly higher among injured casualties in Bolgatanga compared to Wa.

Conclusion: There was a high prevalence of alcohol use among nonfatally injured casualties in northern Ghana and injury severity increased with BAC. AUDIT screening in the hospital, alcohol consumption guideline, road safety education with an emphasis on minimizing or eliminating alcohol consumption, and enhanced enforcement of the BAC limit among motorists are recommended.  相似文献   

33.
Drought is a significant natural hazard that slowly evolves over time. Because of its character, drought is difficult to monitor and impacts are often poorly documented. Agriculture is one of the most sensitive sectors that are prone to drought. The objective of this research is to assess the impacts of drought on soybean production and revenue in Kentucky. Soybeans are one of Kentucky’s most important commodities. In this study, impacts of 1930–1931, 1940–1942, 1952–1955, 1987–1988, 1999–2000, and 2007 droughts were considered. It was found that over the recent years, up to 56 % of the revenue from soybeans was lost due to drought. During the first half of the twentieth century, revenue loss reached up to 77 %. This research is valuable to the general public as well as planners and policy makers. Proper documentation of impacts of past droughts will help identify drought vulnerabilities and results in better risk management and mitigation.  相似文献   
34.
Alldredge  A. L.  King  J. M. 《Marine Biology》1985,84(3):253-260
The distance demersal zooplankton (mobile, benthic organisms which periodically emerge from the benthos and move up into the water column) swim vertically above the bottom at night was measured quantitatively on a subtidal sand flat in the Gulf of California during July, 1979. Three patterns of migration were observed: (1) small-bodied animals, including copepods, ostracods and the amphipod Metaceradocus occidentalis, remained within 30 cm of the bottom except at full moon when a significantly higher proportion of these animals swam up at least 1 m into the water column, (2) syllid polychaetes swam up at least 2 m into the water column irregardless of the phase of the moon, and (3) large-bodied forms (animals >2 mm) swam throughout the water column but in gradually decreasing abundances nearer the surface. Since nocturnally foraging planktivorous fishes feed primarily on the large-bodied, readily visible animals, we had predicted that these large forms would remain near the relative safety of the benthos. However, the movement of the larger demersal zooplankton higher into the water column than the smaller, less visible forms, suggests that factors other than predation, possibly dispersal, may be major selective pressures governing the distance demersal zooplankton swim above the benthos.  相似文献   
35.
36.
The coralline alga Phymatolithon calcareum was dredged from 13 m in the Kattegatt, Baltic Sea, in December, 1980, and its rate of calcification was measured by 45Ca++-uptake methods. Light-saturated calcification rates at 5°C ranged from 15.8 g CaCO3 g-1 dry wt h-1 for the basal parts of the plants to 38.7 g CaCO3 g-1 dry wt h-1 for the tips. These age gradients were not apparent when calcification rates were expressed on the basis of surface area. Experiments with salinity (10, 20, 30) and temperature (0°, 5°, 10°, 20°C) indicated that optimum conditions for calcification were at 30 S and at temperatures above 10°C. Salinity had a greater influence on calcification rate than did temperature, and there was a positive relationship between salinity and calcification rate at all temperatures. In 6 mo old cultures, salinity was again the important factor, with all plants remaining healthy at 30 except those at the highest temperature (20°C). These trends, and the low calcification rates at 10S (4.6 g CaCO3 g-1 dry wt h-1 at 5°C to 8.6 g CaCO3g-1 dry wt h-1 at 20°C) suggest that low salinity may be the explanation for the general absence of P. calcareum from the brackish waters of the Baltic Sea. Short-term experiments in which salinity was kept constant while Ca++ concentration was altered, and experiments in which salinity was varied and Ca++ concentration kept constant, suggest that it is the calcium ion concentration and not salinity per se which affects calcification rates.  相似文献   
37.
This paper presents the results of a preliminary study on the uptake of 45Ca in the mesoskeleton of the gorgonian Eunicella papillosa (Octocorallia). Hourly seawater aliquots over 12 h periods displayed considerable fluctuations of activity with time, reflecting a disappearance and reappearance of tracer during the experiment. Analysis of total coenenchyme mass showed an initial rapid but fluctuating uptake of tracer and a progressive decrease with time. Distinct differences in the calcification rate of specific growth regions of the coral were detected, the rate being higher in branch tips than in lower branch regions. Chase experiments on colonies previously incubated for 24 h revealed that up to 45% of the tracer taken up during labelling were returned to the seawater. A comparison of the tracer content of the coenenchyme and the calcite spicules revealed that up to 70% of the calcium taken up remained in the coral tissue. Quantification of isotopic exchange phenomena with dead corals and isolated spicules emphasized the importance of the live coral tissue as a barrier and regulator of Ca uptake. The results are discussed in the light of the limitations of radioisotope techniques for the determination of calcification rates, and an attempt to compare rates with data in the literature is made.  相似文献   
38.
Assessing Land-Use Impacts on Natural Resources   总被引:3,自引:1,他引:2  
/ Much information is available on changes that occur in natural resources from both spatially-explicit data on environmental conditions and models of the interactions of these conditions and resources with human activities. The strategy for assessing land-use impacts on natural resources developed in this paper provides a framework for using relevant data and models to address questions of how management practices can promote both use and protection of resources. This assessment strategy integrates spatially explicit environmental data using geographic information systems (GIS) with computer models that simulate changes in land cover in response to land-use impacts. The computer models also simulate susceptibility of species to changes in habitat suitability and landscape patterns. The approach is applied to management of limestone barrens on the Oak Ridge Reservation in East Tennessee. Potential limestone barrens habitats are identified by overlaying appropriate soils, geology, slope, and land-use/land-cover conditions. Their validity is tested against known sites containing rare species that occur in these habitats. The location of habitats at risk in the aftermath of human activities is determined by using an available area model that identifies the size and proximity of sites that particular types of species can no longer use as habitat. The resulting risk map can be used in land management planning. The approach uses readily available in situ and remotely sensed data and is applicable to a wide range of locations and land-use scenarios. This approach can be refined based on needs identified by land managers and on the sensitivity of the results to the resolution of available resource information.KEY WORDS: Land management; Assessment; Habitat characterization; Limestone barrens; Ecological modeling; Geographic information systems  相似文献   
39.
Modeling the impact of ozone x drought interactions on regional crop yields   总被引:3,自引:0,他引:3  
The influence of soil moisture stress on crop sensitivity to O3 was evaluated for corn (Zea mays L.), cotton (Gossypium hirsutum L.), soybean (Glycine max L. Merr.), and wheat (Triticum aestivum L.) grown in the United States. This assessment was accomplished by using yield forecasting models to estimate the influence of soil moisture deficits on regional yield and a previously developed model to predict moisture stress x O3 interactions. Reduced crop sensitivity to O3 was predicted for those regions and years for which soil moisture stress reduced yield. The models predicted a drought-induced reduction in crop sensitivity to O3 of approximately 20% for the 1979 to 1983 period; i.e. a hypothetical O3-induced yield reduction of 5% for adequately watered crops would have been reduced to a 4% effect by the 1979 to 1983 distribution of soil moisture deficits. However, predicted drought effects varied between crops, regions, and years. Uncertainties in the model predictions are also discussed.  相似文献   
40.
Much attention is being directed to the measurement and modeling of surface-atmosphere exchanges of CO2 for different surface types. However, as yet, few measurements have been conducted in cities, even though these environments are widely acknowledged to be major sources of anthropogenic CO2. This paper highlights some of the challenges facing micrometeorologists attempting to use eddy covariance techniques to directly monitor CO2 fluxes in urban environments, focusing on the inherent variability within and between urban areas, and the importance of scale and the appropriate height of measurements. Results from a very short-term study of CO2 fluxes, undertaken in Chicago, Illinois in the summer of 1995, are presented. Mid-afternoon minimum CO2 concentrations and negative fluxes are attributed to the strength of biospheric photosynthesis and strong mixing of local anthropogenic sources in a deep mixed layer. Poor night-time atmospheric mixing, lower mixed layer depths, biospheric respiration, and continued missions from mobile and fixed anthropogenic sources, account for the night-time maxima in CO2 concentrations. The need for more, longer-term, continuous eddy covariance measurements is stressed.  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