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   205篇
  免费   6篇
  国内免费   1篇
安全科学   21篇
废物处理   5篇
环保管理   54篇
综合类   18篇
基础理论   40篇
污染及防治   41篇
评价与监测   17篇
社会与环境   13篇
灾害及防治   3篇
  2023年   1篇
  2022年   3篇
  2021年   1篇
  2020年   2篇
  2019年   5篇
  2018年   11篇
  2017年   10篇
  2016年   12篇
  2015年   8篇
  2014年   7篇
  2013年   14篇
  2012年   10篇
  2011年   11篇
  2010年   10篇
  2009年   8篇
  2008年   20篇
  2007年   9篇
  2006年   8篇
  2005年   10篇
  2004年   2篇
  2003年   8篇
  2002年   6篇
  2001年   2篇
  2000年   1篇
  1999年   2篇
  1998年   4篇
  1997年   5篇
  1996年   4篇
  1995年   1篇
  1994年   2篇
  1993年   3篇
  1992年   1篇
  1990年   1篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1982年   3篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
排序方式: 共有212条查询结果,搜索用时 15 毫秒
11.
The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO2) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO2 production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO2 production by mineralization as well as CO2 loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of \( {0.70}_{-0.31}^{+0.27} \) to \( {1.52}_{-0.90}^{+1.09} \) Pg C yr?1 depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO2 sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO2 sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.  相似文献   
12.
The factors that compel individuals to exert the extraordinary effort needed to create high reliability—consistent error‐free performance under trying conditions—remain unspecified. Here, we propose that when individuals experience emotional ambivalence and prosocial motivation, it induces the broad thinking and other‐orientation that undergird mindful organizing and high reliability. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
13.

Problem

Falls in older persons in developing countries are poorly understood, and falls prevention and health promotion programmes for this population are largely lacking.

Methods

A systematic review was carried out of relevant literature on falls and prevention programmes, and falls prevention education, and a scan undertaken of health promotion programmes for older persons in a representative country - South Africa.

Results

Studies on the risk and prevalence of falls are largely retrospective and hospital-based, with varied methodology, including study period, sampling method and sample size. Falls prevalence is based largely on self-reports in studies on general trauma in all age groups. Falls incidence varies from 10.1% to 54%. No reports could be traced on sustained falls prevention or health promotion programmes.

Conclusion

Scant research has been conducted and little preventive education offered on falls in older persons. Adaptation of the Canadian Falls Prevention Curriculum for developing countries will help to fill gaps in knowledge and practice.

Impact on industry

With rapid increase in the populations of older persons in developing countries, research on age related disorders such as falls is required to guide policy and management of falls.  相似文献   
14.
LeBauer DS  Treseder KK 《Ecology》2008,89(2):371-379
Our meta-analysis of 126 nitrogen addition experiments evaluated nitrogen (N) limitation of net primary production (NPP) in terrestrial ecosystems. We tested the hypothesis that N limitation is widespread among biomes and influenced by geography and climate. We used the response ratio (R approximately equal ANPP(N)/ANPP(ctrl)) of aboveground plant growth in fertilized to control plots and found that most ecosystems are nitrogen limited with an average 29% growth response to nitrogen (i.e., R = 1.29). The response ratio was significant within temperate forests (R = 1.19), tropical forests (R = 1.60), temperate grasslands (R = 1.53), tropical grasslands (R = 1.26), wetlands (R = 1.16), and tundra (R = 1.35), but not deserts. Eight tropical forest studies had been conducted on very young volcanic soils in Hawaii, and this subgroup was strongly N limited (R = 2.13), which resulted in a negative correlation between forest R and latitude. The degree of N limitation in the remainder of the tropical forest studies (R = 1.20) was comparable to that of temperate forests, and when the young Hawaiian subgroup was excluded, forest R did not vary with latitude. Grassland response increased with latitude, but was independent of temperature and precipitation. These results suggest that the global N and C cycles interact strongly and that geography can mediate ecosystem response to N within certain biome types.  相似文献   
15.
Mytilus galloprovincialis (Mg), the Mediterranean blue mussel, is sympatric with the native M. trossulus (Mt) throughout much of the north Pacific, likely as the result of human introduction. We investigated the distribution of the two species and their hybrids (Mgt) in Puget Sound, Washington, to determine whether differences occur in habitat preference between the two species and hybrids. In addition, we investigated whether there were consistent size and shape differences between the native and introduced mussels and hybrids. Measurements of over 6,000 mussels from 30 sites, of which 1,460 were genotyped for a species-specific genetic marker, revealed that Mg and Mgt can be found throughout Puget Sound. Mg and Mgt were larger and exhibited a greater height:length ratio than Mt. Frequencies of Mg and Mgt were higher in subtidal habitats, such as docks, than on intertidal rocks, walls or pilings. Within intertidal habitats, Mg and Mgt were more frequent than Mt in the lower reaches of the intertidal. At slightly more than half the sites the frequency of the three genotypes accorded with random mating expectations suggesting no consistent barriers to gene flow between species. The standardized random sampling methods and simple morphometric identification techniques described here can be used to test whether the frequency of invasive mussels changes over time and space in Puget Sound.  相似文献   
16.
The Neotropical seven-spined gobies (tribe Gobiosomatini), including the Gobiosoma and Microgobius groups, constitute a speciose, monophyletic gobiid taxon. In particular, member species of the Gobiosoma group exhibit a combination of behavioral diversification and microhabitat specialization that may have played a major role in their collective rapid evolution and high rate of speciation. Functional hermaphroditism, which is common among gobiids, can promote exploitation of patchily distributed micro-niches by countering potential reductions in reproductive opportunities. However, the possible role of functional hermaphroditism in the exploitation of microhabitats and rapid speciation in the Gobiosoma group is unknown. One member species, Tigrigobius multifasciatus, is a functional hermaphrodite. Two other Gobiosoma group species are functionally gonochoric (i.e., constant-sexed), but exhibit transient hermaphroditic ovarian structure among immatures. In this study, ovarian morphology among immature and adult females of several Gobiosoma group species was examined to see if hermaphroditic gonadal features are present. Although no evidence of functional hermaphroditism in the form of precursive accessory gonadal structures (pAGS) associated with the adult ovary was found among newly examined species, all species exhibited the transient expression of hermaphroditic gonadal features associated with the immature ovary. In contrast, among six species of non-Gobiosomatini genera having no record of hermaphroditism, none exhibited similar transient hermaphroditic features associated with the immature ovary. These findings suggest that hermaphroditism may have been an ancestral trait which has been secondarily lost within some Gobiosoma group species. This study also shows that ontogenetic and morphogenic processes within the gobiid reproductive system may provide new insights into the evolution of life history traits and significantly further our understanding of the extraordinary evolutionary success of this group.  相似文献   
17.
The degree to which an individual feels connected to the natural world can be a positive predictor of pro-environmental behavior (PEB). This has led to calls to ‘reconnect to nature’ as a ‘treatment’ for PEB. What is not clear is the relationship between where one feels connected to nature and where one acts pro-environmentally. We propose that integrating spatial scale into the conceptualization of these constructs will provide insights into how different degrees of connectedness influence pro-environmental behavior. We discuss trends towards a spatial understanding of human–nature connectedness (HNC) and introduce three archetypes that highlight scalar relationships between scale of connectedness and scale of pro-environmental behavior: (1) equal interactions, (2) embedded interactions, and (3) extended interactions. We discuss potential policy and practice implications of taking a spatially explicit approach to HNC–PEB research, and propose a research agenda for investigating these scalar relationships that can inform nature as a ‘treatment’ intervention.  相似文献   
18.
Increasing epidemiological evidence has established an association between a host of adverse health effects and exposure to ambient particulate matter (PM) and co-pollutants, especially those emitted from motor vehicles. Although PM and their co-pollutants dispersion profiles near the open freeway have been extensively characterized by means of both experimental measurements and numerical simulations in recent years, such investigations near freeways with roadside barriers have not been well documented in the literature. A few previous studies suggested that the presence of roadside structures, such as noise barriers and vegetation, may impact the decay of pollutant concentrations downwind of the freeway by limiting the initial dispersion of traffic emissions and increasing their vertical mixing due to the upward deflection of airflow. Since the noise barriers are now common roadside features of the freeways, particularly those running through populated urban areas, it is pertinent to investigate the impact of their presence on the particles and co-pollutants concentrations in areas adjacent to busy roadways. This study investigated two highly trafficked freeways (I-710 and I-5) in Southern California, with two sampling sites for each freeway, one with and the other without the roadside noise barriers. Particle size distributions and co-pollutants concentrations were measured in the immediate proximity of freeways and at different distances downwind of the freeways. The results showed the formation of a “concentration deficit” zone in the immediate vicinity of the freeway with the presence of roadside noise barrier, followed by a surge of pollutant concentrations further downwind at 80–100 m away from freeway. The particle and co-pollutants concentrations reach background levels at farther distances of 250–400 m compared to 150–200 m at the sites without roadside noise barriers.  相似文献   
19.
An integrated exposure model was developed that estimates nitrogen dioxide (NO(2)) concentration at residences using geographic information systems (GIS) and variables derived within residential buffers representing traffic volume and landscape characteristics including land use, population density and elevation. Multiple measurements of NO(2) taken outside of 985 residences in Connecticut were used to develop the model. A second set of 120 outdoor NO(2) measurements as well as cross-validation were used to validate the model. The model suggests that approximately 67% of the variation in NO(2) levels can be explained by: traffic and land use primarily within 2 km of a residence; population density; elevation; and time of year. Potential benefits of this model for health effects research include improved spatial estimations of traffic-related pollutant exposure and reduced need for extensive pollutant measurements. The model, which could be calibrated and applied in areas other than Connecticut, has importance as a tool for exposure estimation in epidemiological studies of traffic-related air pollution.  相似文献   
20.
Pharmaceuticals, including the lipid regulator gemfibrozil and the non-steroidal anti-inflammatory drug diclofenac have been identified in waste water treatment plant effluents and receiving waters throughout the western world. The acute and chronic toxicity of these compounds was assessed for three freshwater species (Daphnia magna,Pseudokirchneriella subcapitata, Lemna minor) using standardised toxicity tests with toxicity found in the non-environmentally relevant mid mg L−1 concentration range. For the acute endpoints (IC50 and EC50) gemfibrozil showed higher toxicity ranging from 29 to 59 mg L−1 (diclofenac 47-67 mg L−1), while diclofenac was more toxic for the chronic D. magna 21 d endpoints ranging from 10 to 56 mg L−1 (gemfibrozil 32-100 mg L−1). These results were compared with the expression of several biomarkers in the zebra mussel (Dreissena polymorpha) 24 and 96 h after exposure by injection to concentrations of 21 and 21,000 μg L−1 corresponding to nominal concentrations of 1 and 1000 μg L−1. Exposure to gemfibrozil and diclofenac at both concentrations significantly increased the level of lipid peroxidation, a biomarker of damage. At the elevated nominal concentration of 1000 μg L−1 the biomarkers of defence glutathione transferase and metallothionein were significantly elevated for gemfibrozil and diclofenac respectively, as was DNA damage after 96 h exposure to gemfibrozil. No evidence of endocrine disruption was observed using the alkali-labile phosphate technique. Results from this suite of biomarkers indicate these compounds can cause significant stress at environmentally relevant concentrations acting primarily through oxidation pathways with significant destabilization of the lysosomal membrane and that biomarker expression is a more sensitive endpoint than standardised toxicity tests.  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