首页 | 官方网站   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   401篇
  免费   11篇
  国内免费   3篇
环境安全   415篇
  2023年   2篇
  2022年   8篇
  2021年   8篇
  2020年   6篇
  2019年   11篇
  2018年   9篇
  2017年   18篇
  2016年   15篇
  2015年   12篇
  2014年   12篇
  2013年   27篇
  2012年   16篇
  2011年   15篇
  2010年   17篇
  2009年   26篇
  2008年   15篇
  2007年   24篇
  2006年   13篇
  2005年   20篇
  2004年   13篇
  2003年   20篇
  2002年   13篇
  2001年   4篇
  1999年   8篇
  1998年   6篇
  1997年   5篇
  1996年   6篇
  1995年   4篇
  1994年   4篇
  1993年   3篇
  1992年   2篇
  1991年   3篇
  1990年   3篇
  1988年   3篇
  1987年   4篇
  1986年   4篇
  1985年   2篇
  1984年   3篇
  1983年   2篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1978年   3篇
  1977年   3篇
  1976年   2篇
  1974年   2篇
  1972年   2篇
  1971年   1篇
  1956年   1篇
  1954年   1篇
排序方式: 共有415条查询结果,搜索用时 31 毫秒
11.
For (134/137)Cs, and many other soil contaminants, research into transfer to plants has focused on particular crops and phytoremediation candidates, producing uptake data for a small proportion of all plant taxa. Despite the significance of differences in uptake between plant taxa, the capacity of soil-to-plant transfer models to predict them is currently confined to those taxa for which data exist, there being no method to predict uptake by other taxa. We used residual maximum likelihood (REML) analysis on data from experiments (including 89 plant taxa from China plus 32 phytoremediation candidates) together with data from the literature, to construct a database of relative (134/137)Cs concentrations in 273 plant taxa. The REML (134/137)Cs concentrations in plants are not normally distributed but significantly clustered. Analysis of variance (ANOVA), coded with a recent ordinal phylogeny for flowering plants, showed that plant taxa do not behave independently for (134/137)Cs concentration because 42 and 15% of inter-taxa differences are associated with phylogeny above the species and ordinal level, respectively. In general, Eudicots, and especially the Caryophyllales, Asterales, and Brassicales, have high (134/137)Cs concentrations, while the Fabales and Magnoliids, in particular Poales, have low (134/137)Cs concentrations. Plants of the stress-tolerant ruderal (S-R) growth strategy sensu Grime have, in general, high concentrations of Cs, while those of the competitive (C) and generalist (C-S-R) strategies have low concentrations, although these effects are less pronounced than those of phylogeny. Plant phylogeny and growth strategy might thus be used to predict a significant portion of inter-taxa differences in plant uptake of (134/137)Cs.  相似文献   
12.
Natural resource and wildlife managers must balance the disparate priorities of a diversity of stakeholders. To manage these priorities, a firm understanding of topics salient to the public is needed. The media often report on issues of importance to the public; therefore, these reports may be a useful measure of public interest. However, efficient methods for distinguishing diverse topics related to a wildlife management issue reported in the media and changes in the salience of those topics have been lacking. We used latent Dirichlet allocation, a Bayesian mixture model, to quantitatively assess the salience of topics surrounding the gray wolf (Canis lupus), which was reintroduced to Idaho (U.S.A.) in 1995. We analyzed articles published from 1960 to 2015 in an Idaho newspaper. We identified 6 distinct topics associated with gray wolves: policy, hunting, biological status, implementation of management, recovery, and human-wolf conflict. The salience of topics pre- and postreintroduction of wolves (1995) and pre- and postdelisting of wolves from the U.S. Endangered Species Act (2009) differed significantly, underscoring that these events were turning points in how issues were being publicly discussed and framed. Articles written by the local reporters were more likely to report on topics regarding conflict between humans and wolves, whereas articles sourced from a national outlet reported more on topics pertaining to wolf policy and biological status. In the context of managing a contentious, far-ranging, and long-lived wildlife species, our methods can help guide the location and timing of a suite of management strategies (e.g., media relation plans and stakeholder engagement) that promote human-wildlife coexistence across different landscapes.  相似文献   
13.
The provision of ecosystem services is a prominent rationale for urban greening, and there is a prevailing mantra that ‘trees are good’. However, understanding how urban trees contribute to sustainability must also consider disservices. In this perspective article, we discuss recent research on ecosystem disservices of urban trees, including infrastructure conflicts, health and safety impacts, aesthetic issues, and environmentally detrimental consequences, as well as management costs related to ecological disturbances and risk management. We also discuss tradeoffs regarding species selection and local conservation concerns, as well as the central role of human perception in the interpretation of ecosystem services and disservices, particularly the uncritical assertion that ‘everybody loves trees’. Urban forestry decision-making that fails to account for disservices can have unintended negative consequences for communities. Further research is needed regarding life cycle assessments, stakeholder decision-making, return-on-investment, and framings of services and disservices in urban forestry.  相似文献   
14.
Environmental Science and Pollution Research - Plastics are synthetic polymers known for their outstanding durability and versatility, and have replaced traditional materials in many applications....  相似文献   
15.
Poor early-life nutrition could reduce adult reproductive success by negatively affecting traits linked to sexual attractiveness such as song complexity. If so, this might favor strategic mate choice, allowing males with less complex songs to tailor their mating tactics to maximize the reproductive benefits. However, this possibility has been ignored in theoretical and empirical studies. By manipulating the micronutrient content of the diet (e.g., low or high) during the postnatal period of male zebra finches, we show for the first time (1) that males reared on a poor (low) micronutrient diet had less complex songs as adults; (2) that these males, in contrast to the high micronutrient diet group, were more selective in their mating strategies, discriminating against those females most likely to reduce their clutch size when paired with males having less complex songs; and (3) that by following different mating strategies, males reared on the contrasting diets obtained similar reproductive benefits. These results suggest that early-life dietary conditions can induce multiple and long-lasting effects on male and female reproductive traits. Moreover, the results seem to reflect a previously unreported case of adaptive plasticity in mate choice in response to a nutritionally mediated reduction in sexual attractiveness.  相似文献   
16.
The Fourth International Conference on Fluidized Bed Combustion (FBC) was held at The MITRE Corporation in McLean, VA, December 9 to 11, 1975. With attendees from Great Britain, West Germany, Japan, Canada, and Sweden, the conference apparently fulfilled its international scope and intent.

The objectives of the conference were to review the current state of technology in FBC, to promote technical information exchange on FBC and related areas, and to generate a useful technical information base for further FBC development. Throughout the conference, the goal of commercialization was repeatedly emphasized.

Sponsored by the U.S. Energy Research and Development Administration (ERDA) and coordinated by MITRE, this meeting was the most comprehensive event in the seven year series of conferences on this subject according to attendees. ERDA, the government’s lead agency in FBC technology development, is the principal sponsor and coordinator of the National Fluidized Bed Combustion Program with the goal of advancing the commercialization time frame for FBC. Prior conferences in this series were hosted by the Environmental Protection Agency (EPA) at about two year intervals at Hueston Woods, Ohio. The last EPA conference was held in October 1972.  相似文献   
17.
Residential interior door positions influence the pollutant concentrations that result from short-term indoor sources, such as cigarettes, candles, and incense. To elucidate this influence, we reviewed past studies and conducted new experiments in three residences: a single-story 714 m3 ranch-style house, a 510 m3 two-story split-level house, and a 200 m3 two-story house. During the experiments, we released sulfur hexafluoride or carbon monoxide tracer gas over short periods (≤30 min) and measured concentrations in the source room and at least one other (receptor) room for various interior door opening positions. We found that closing a door between rooms effectively prevented transport of air pollutants, reducing the average concentration in the receptor room relative to the source room by 57–100% over exposure periods of 1–8 h. When intervening doors were partially or fully open, the reduction in average concentrations ranged from 3% to 99%, varying as a function of door opening width and the distance between source and receptor rooms.  相似文献   
18.
Safety climate   总被引:12,自引:0,他引:12  
Safety climate, the objective measurement of attitudes and perceptions toward Occupational Health & Safety (OH&S) issues, has been largely ignored and measures such as lost time and frequency rate have been used to determine the efficacy of OH&S programs. Yet, it is clear that measuring the precursors of accidents identified in a safety climate analysis provides a powerful proactive management tool. This paper reports on safety climate factors found in clerical and service organizations in Australia. Concurrent validity studies are reported. In contradistinction to published studies, it is argued that safety climate factors are not stable across organizations. The significance of this for planning and assessing the efficacy of OH&S programs is discussed. It is concluded that although safety climate factors are not stable, the safety climate factor pattern identified in organizations provides a powerful management tool for designing OH&S programs.  相似文献   
19.
Applications of linear programming to water quality and water quantity problems are discussed, and a fairly comprehensive sample of recent literature in these areas is reviewed. Basic elements of linear programming are also discussed. Emphasis is placed on the elements of linear programming that make it a useful tool for analyzing water resource problems and the basic features of various water resource problems that render them amenable to meaningful analysis by linear programming.  相似文献   
20.
Graduated licensing has been implemented in many U.S. states to reduce teenage driver crash involvement. The goal is to introduce teenagers gradually to driving before allowing full, unrestricted licensure. Tennessee, one of the states that introduced graduated licensing, implemented a program to influence both driving by teenagers during the learner stage and restrictions imposed by parents after licensure. In addition to a standard welcome letter, booklets and reminder cards were mailed to parents of teenagers who had just obtained their learner's permits. The booklets and cards were designed to assist parents in becoming more actively involved in their children's driving experiences. The effects of three different approaches (welcome letter only, letter plus booklet, and letter plus booklet plus reminder cards) on parental involvement, teenage crashes, and teenage citations were assessed based on telephone interviews with parents. Although the parents said the booklets and reminder cards were helpful and should continue to be sent to other parents, there were no discernible effects on teenage practice driving and reported parental involvement during the learner stage. Nor was there any measurable influence on restrictions imposed by parents after licensure. It is unknown whether the standard welcome letter affected parental involvement, but overall supervised driving exceeded the state requirements by a substantial margin.  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-23

京公网安备 11010802026262号