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   2389篇
  免费   200篇
  国内免费   807篇
安全科学   443篇
废物处理   23篇
环保管理   377篇
综合类   1344篇
基础理论   599篇
环境理论   6篇
污染及防治   160篇
评价与监测   164篇
社会与环境   174篇
灾害及防治   106篇
  2024年   25篇
  2023年   96篇
  2022年   105篇
  2021年   133篇
  2020年   111篇
  2019年   133篇
  2018年   135篇
  2017年   142篇
  2016年   178篇
  2015年   136篇
  2014年   132篇
  2013年   279篇
  2012年   180篇
  2011年   203篇
  2010年   141篇
  2009年   160篇
  2008年   112篇
  2007年   156篇
  2006年   134篇
  2005年   99篇
  2004年   88篇
  2003年   97篇
  2002年   73篇
  2001年   57篇
  2000年   48篇
  1999年   30篇
  1998年   26篇
  1997年   23篇
  1996年   19篇
  1995年   19篇
  1994年   24篇
  1993年   15篇
  1992年   8篇
  1991年   4篇
  1990年   7篇
  1989年   4篇
  1988年   8篇
  1987年   4篇
  1985年   3篇
  1984年   3篇
  1983年   6篇
  1982年   2篇
  1981年   9篇
  1980年   6篇
  1979年   4篇
  1978年   2篇
  1977年   4篇
  1974年   3篇
  1973年   2篇
  1972年   3篇
排序方式: 共有3396条查询结果,搜索用时 734 毫秒
781.
On Developing Bioindicators for Human and Ecological Health   总被引:5,自引:0,他引:5  
Risk assessors and risk managersgenerally either examine ecological health (usingbioindicators) or human health (using biomarkers ofexposure or effect). In this paper we suggest thatit is possible and advantageous to developbioindicators that can be used to assess exposureand effect for both human and non-human receptors. We describe the characteristics of suitablebioindicators for both human and ecological health,using mourning doves (Zenaida macroura),raccoons (Procyon lotor), and bluefish (Pomatomus saltatrix) as examples, and list thegeneral characteristics of other species that wouldmake them useful indicators for assessing both humanand ecological health. Bioindicators can beused cross-sectionally to assess the status ofecosystems and risk as well as longitudinally formonitoring changes or evaluating remediation. Forboth human and ecological risk assessment, there arethree sets of characteristics to consider whenselecting bioindicators: biological relevance,methodological relevance, and societal relevance. An indicator which fails to fulfill these is notlikely to be considered cost-effective and is likelyto be abandoned. The indicator should be readilymeasured and must measure an important range ofimpacts. For long-term support of a bioindicator,the indicator should be easily understood, and becost effective. We suggest that bioindicators thatcan also be used for both ecological and humanhealth risk assessment are optimal.  相似文献   
782.
In any ecological risk assessment, afull complement of the relevant members of theecosystems being studied should be considered. Reptiles in general, and snakes in particular, areimportant although often neglected components ofterrestrial and aquatic ecosystems and should beincluded in any study on environmental contamination. By neglecting reptiles, the risks posed by aparticular contaminant cannot be fully assessed. Since all snakes are secondary, tertiary, and toppredators, they are susceptible to the bioaccumulationof environmental contaminants. Their unique lifehistories make their roles in food webs diverse andimportant, and they are crucial to the properfunctioning of many ecological processes. We reviewand summarize organic and inorganic contaminant andradionuclide/radiation residue and lethal andsublethal effects data for snakes to stress theimportance of snakes and encourage their inclusion inecological risk assessments, to demonstrate thepaucity of available contaminant data on snakes andreveal the main information gaps, to encourage furtherecotoxicological studies on snakes, and to facilitatethe use of existing snake contaminant data inecological risk assessments. This review is the mostcomprehensive review currently available on theeffects on and accumulation of environmentalcontaminants in snakes.  相似文献   
783.
Estimates of crown transparency calculated using the semi-automatic image analysis system CROCO were compared withthe visual estimates of survey teams from 12 European countries.For each of five European species (Norway spruce (Picea abies (L.) Karst.), silver fir (Abies alba Mill.), Scotspine (Pinus sylvestris L.), beech (Fagus sylvatica L.), oak (Quercus robur L.)) 15 trees were assessed. In 64\% of the comparisons, CROCO estimates and the survey teams' scores differed significantly, while differences between countries were significant in 58 % of all comparisons. We calculated Spearman's rank correlation and the standard deviation of the differences between CROCO and each country and between pairs of countries. We then computed the medians for CROCO and each country. CROCO and only a few countries hadfor all species a higher median correlation and lower median standard deviation than the median for the comparison between countries. In addition no country had a consistently higher correlation or lower standard deviation than CROCO. We concludethat CROCO can provide more consistent and less variable estimates of crown transparency than visual assessments and that it can serve as a reference to detect differences in visualtransparency assessments between countries over time.  相似文献   
784.
Our knowledge of global climate change has many uncertainties.Whether global air temperature will increase, by how much, and when,are subject to debate, but there is little doubt that troposphericconcentrations of several trace gases are increasing. While possibleincreases in the average air temperature is a product of these changes,the increases in the trace gases alone will have an effect on agriculture.Increases in the ambient concentrations of carbon dioxide are expectedto have a positive net effect on crop production. In contrast, anyincreases in the penetration of surface-level ultraviolet-B (280–320 nm)radiation, and known increases in surface ozone concentrations, areconsidered to have adverse effects on certain crops. Our presentknowledge of the joint effects on crops of elevated levels of carbondioxide, ultraviolet-B radiation and ozone, and possible alterations in airtemperature and precipitation patterns, is virtually zero. Therefore, anypredictions of the effects of global climate change on agriculture aresubject to significant uncertainties. In contrast, coupling of climatechange (only temperature and precipitation) models to crop productionhas led to a number of future scenarios. In spite of theirpresent limitations, results from these efforts can be useful in planningfor future agriculture.  相似文献   
785.
在枯水期和丰水期,对秦皇岛市15个典型入海排污口污水进行生物效应监测,选用发光细菌(费歇尔弧菌)、藻类(中肋骨条藻)、甲壳类(卤虫)、鱼类(海水青鳉幼鱼) 4种不同的生物毒性测试生物对污水进行短期急性毒性测试。结果表明:排海污水的毒性大小易受雨水稀释影响;海水青鳉幼鱼对污水最为敏感,其次为卤虫和中肋骨条藻,费歇尔弧菌敏感性最低。对排海污水毒性评估结果与理化指标的相关性分析进一步表明,仅仅依靠理化指标来评估污水的环境影响具有局限性。  相似文献   
786.
Ozone biomonitoring is a detection and monitoring techniquethat involves documenting ozone-induced visible injury toknown ozone-sensitive species under conditions of ambientexposure. The USDA Forest Service administers a long-term,nationwide ozone biomonitoring program to address public andscientific concerns about ozone impacts on forest health. Asystematic grid is used as the basis for biomonitoring sitelocations. At each site, trained field crews evaluate amaximum of thirty plants of up to six species and record the amount and severity of leaf-injury on individualplants. Injury from ozone was found more often on biomonitoring sites in the eastern Unites States than in theinterior or west-coast areas. Further results from thenortheast reveal that in any year, there is a higherpercentage of ozone-injured plants with more severe symptomsin areas with relatively high ozone concentrations than inareas with relatively low ozone. In very dry years (e.g.,1999) the percentage of injured plants and injury severityestimates are both sharply reduced even though ambient ozoneexposures are high. These findings demonstrate thatbiomonitoring data provide meaningful evidence of when highozone concentrations during the growing season have biologicalsignificance. Any assessment of ozone stress in the forestenvironment must include both biomonitoring (i.e., plantresponse) and air quality data to be complete.  相似文献   
787.
In her recent Counter-Reply to my views, Evelyn Pluhar defends her use of literature on nutrition and restates her argument for moral vegetarianism. In his Vegan Ideal article, Gary Varner claims that the nutrition literature does not show sufficient differences among women, men, and children to warrant concern about discrimination. In this response I show how Professor Pluhar continues to draw fallacious inferences: she begs the question on equality, avoids the main issue in my ethical arguments, argues from irrelevancies, misquotes her sources, equivocates on context, confuses safety with morality, appeals to fear, confuses correlation with cause, fails to evaluate scientific studies, draws hasty conclusions from insufficient data, ignores a large amount of data which would call her views into question, does not follow good scientific or moral argumentation, objectionably exceeds the limits of her expertise, and resorts to scapegoating. I also argue that Professor Varner fails to make his case because he offers virtually no evidence from scientific studies on nutrition, relies on outdated and fallacious sources, makes unsupported claims, ignores evidence that would contravene his claims, draws hasty conclusions based on weakly supported hypotheses rather than facts, employs a double standard, appeals to ignorance, does not evaluate arguments from his sources, and makes anad hominem attack on a respected nutritionist when his focus should be on evaluating the evidence and arguments from the scientific studies themselves. Neither Varner nor Pluhar have responded sufficiently to the real issue in my arguments, that of discrimination and bias in the vegan ideal.  相似文献   
788.
生态系统健康评价的研究进展   总被引:4,自引:0,他引:4  
回顾了生态系统健康的概念,阐述了水生态系统健康评价的三种指标体系:指示物种指标体系、结构功能指标体系、V-O-R指标体系.其中,结构功能指标体系从选取指标和指标分类两方面进行了方法归纳,分析了生态系统健康的几种评价方法,以及讨论了生态系统健康研究中存在的问题和发展趋势.  相似文献   
789.
张文渊 《环境科技》2003,16(2):28-29
自然环境的优劣,会直接影响人体的健康。在良好的环境中,人们所依赖的物质是不受污染的,自然环境的物质中所含微量元素和微量元素对维持人类生命、保护人体健康起到了一定的基础作用。  相似文献   
790.
室内空气污染对人体健康影响与防护对策   总被引:1,自引:0,他引:1  
韦秀丽 《云南环境科学》2005,24(Z1):175-177
介绍了室内空气污染的定义、室内空气中常见的污染物及其主要来源,分析了室内空气中主要污染物对人体健康的影响, 提出了保护室内环境的对策.  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