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   1082篇
  免费   16篇
  国内免费   21篇
安全科学   34篇
废物处理   39篇
环保管理   238篇
综合类   131篇
基础理论   208篇
环境理论   2篇
污染及防治   364篇
评价与监测   66篇
社会与环境   33篇
灾害及防治   4篇
  2023年   8篇
  2022年   14篇
  2021年   20篇
  2020年   5篇
  2019年   15篇
  2018年   20篇
  2017年   27篇
  2016年   28篇
  2015年   20篇
  2014年   31篇
  2013年   177篇
  2012年   45篇
  2011年   45篇
  2010年   48篇
  2009年   59篇
  2008年   46篇
  2007年   56篇
  2006年   69篇
  2005年   38篇
  2004年   31篇
  2003年   32篇
  2002年   35篇
  2001年   6篇
  2000年   15篇
  1999年   8篇
  1998年   4篇
  1997年   16篇
  1996年   6篇
  1995年   13篇
  1994年   14篇
  1993年   11篇
  1992年   11篇
  1991年   8篇
  1990年   10篇
  1989年   6篇
  1988年   4篇
  1987年   7篇
  1986年   7篇
  1985年   4篇
  1984年   5篇
  1983年   10篇
  1982年   10篇
  1981年   14篇
  1980年   4篇
  1979年   4篇
  1978年   5篇
  1977年   7篇
  1976年   5篇
  1972年   7篇
  1967年   4篇
排序方式: 共有1119条查询结果,搜索用时 31 毫秒
961.
The prevalence of toxicopathic liver lesions in demersal fish on the San Pedro Shelf, California was determined for a 15-year period (1988–2003). Fish livers were sampled at fixed locations as part of the Orange County Sanitation Districts (OCSD) ocean monitoring program. Histopathological examination of selected fish liver tissues was studied to determine whether the wastewater discharge had affected fish health. The prevalence of toxicopathic lesion classes neoplasms (NEO), preneoplastic foci of cellular alteration (FCA), and hydropic vacuolation (HYDVAC) varied among species and locations. For all species sampled, severe lesions occurred in 6.2% of the fish examined (n = 7,694). HYDVAC (4.1%) was the most common toxicopathic lesion type followed by FCA (1.4%) and NEO (0.7%). HYDVAC occurred only in white croaker (Genyonemus lineatus), accounting for 84.8% of the toxicopathic lesions for this species. Prevalence of HYDVAC, NEO, and FCA in white croaker was 15.2, 2.0, and 0.7%, respectively. The prevalence of HYDVAC and NEO in white croaker increased with age and size but there was no sexual difference. A linear regression model was used for hypothesis testing to account for significant differences in fish size (and age for croakers) at the different sampling locations. This analysis showed that for HYDVAC there was no spatial or location effect for lesion rate or size/age of onset. For NEO, the model predicted that white croaker near the wastewater outfall may acquire these lesions at a smaller size/younger age, and at a higher rate, than at other sites. However, this result may be biased due to the unequal size frequency distributions and the low prevalence of NEO in white croaker at the different sampling sites. Bigmouth sole (Hippoglossina stomata) had a prevalence of FCA and NEO of 1.3 and 0.35%, respectively, but the prevalence and distribution of lesions was too few for statistical testing. There was no sexual difference for lesion prevalence in hornyhead turbot (Pleuronichthys verticalis) and the prevalence of FCA and NEO was 3.4 and 0.37%, respectively. FCA prevalence increased with size in hornyhead turbot and there were no significant spatial differences for lesion rates and fish size at lesion onset. Overall, consistent spatial differences for lesion prevalence were not demonstrated and highlight the analytical difficulties of detecting a possible point source impact when the effect is rare, correlated with the size/age structure of the population, and may be caused by exposure to unknown multiple sources. Thus, the usefulness of liver histopathology as a point-source monitoring tool is best applied to where the spatial scale of impact generally exceeds the home range of the target species.  相似文献   
962.
We present the results of a replicated before‐after‐control‐impact study on 33 streams to test the effectiveness of riparian rules for private and State forests at meeting temperature criteria in streams in western Oregon. Many states have established regulatory temperature thresholds, referred to as numeric criteria, to protect cold‐water fishes such as salmon and trout. We examined across‐year and within‐year patterns of exceedance at control and treatment stream temperature probes. Determining whether an exceedance at the downstream end of a harvest was unambiguously related to harvest proved surprisingly difficult. The likelihood of a site exceeding its numeric criterion appeared related, in part, to the site's preharvest temperature range. Four control reaches as well as three preharvest treatment reaches exceeded their numeric criteria, necessitating additional analysis to evaluate timber harvest impacts. Nine percent of sites (3 of 33) both exceeded their numeric criteria and exhibited a potential harvest effect (16.7% of private sites [3 of 18], 0% of State sites [0 of 15]). After harvest, exceedances were typically observed in only the first of the two post‐harvest years. These findings highlight the importance of including temporal and spatial controls in temperature assessments of numeric criteria when the assessment's purpose is to determine whether exceedances are related to human activities.  相似文献   
963.
As the concept of sustainability broadens to include social aspects, sustainability organisations must embrace strategies that allow them to more effectively address community issues and procedural concerns. Biosphere reserves (BRs) and model forests (MFs) advocate strongly for community engagement to achieve place-based sustainability; in practice, however, these organisations have had variable success in effectively engaging community residents and addressing their needs and interests. In this paper, we offer a framework for place-based governance for sustainability that is used to compare strategies used in BRs and MFs operating in the Maritime Provinces of Canada with the operations of Vibrant Communities, an anti-poverty organisation that operates locally in Saint John, New Brunswick. We draw attention to three imperatives: comprehensive understanding, community empowerment, and community-based outcomes, and five procedural drivers: local leadership, strong networks, diverse community engagement, learning together, and information sharing. Based on our results, we provide greater clarity on processes that address the imperatives and mobilise the drivers of effective place-based governance for sustainability. Our results suggest that there is a need for theory and practice to advance beyond current understandings of sustainability governance to enhance the capacity of organisations seeking to implement community-based sustainability strategies.  相似文献   
964.
The persistence and fate of chlorpyrifos and its two metabolites, chlorpyrifos-oxon and the 3, 5, 6-trichloro-2-pyridinol (TCP) break-down product were investigated on kale and collard leaves under field conditions. A simultaneous extraction and quantification procedure was developed for chrorpyrifos and its two main metabolites. Residues of chlorpyrifos, chlorpyrifos oxon, and TCP were determined using a gas chromatograph (GC) equipped with an electron capture detector (GC/ECD). Chlorpyrifos metabolites were detectable up to 23 days following application. Residues were confirmed using a GC equipped with a mass selective detector (GC/MSD) in total ion mode. Initial residues of chlorpyrifos were greater on collard (14.5 µg g?1) than kale (8.2 µg g?1) corresponding to half-lives (T1/2) values of 7.4 and 2.2 days, respectively. TCP, the hydrolysis product, was more persistent on collards with an estimated T1/2 of 6.5 days compared to kale (T1/2 of 1.9 days).  相似文献   
965.
Consensus-based multi-stakeholder forms of environmental governance involving government, private and civil society actors, have become popular for advancing sustainability, but have been criticized for failing to achieve procedural justice objectives including recognition, participation and strengthening capabilities. Yet, how such models have functioned within non-governmental organizations dedicated to advancing sustainability has been underexplored. This paper assesses the procedural elements of consensus-based multi-stakeholder models used within Canadian biosphere reserves and model forests, two organizations working to address environment and sustainability issues. We draw on strategic documents and semi-structured interviews from five organizations in Canada to analyze their governance structures and processes against a framework for procedural justice. We find the organizational structure reproduces elitism and professionalism associated with stakeholder models more generally and reproduces challenges associated with recognition, participation and building capabilities found in other stakeholder approaches. Meeting broader sustainability challenges requires organizations to address procedural justice issues in addition to their traditional environmental concerns.  相似文献   
966.
A new sensitive technique for the quantification of formaldehyde (HCHO) and total aldehydes has been developed in order to monitor these compounds, which are known to be involved in air quality issues and to have health impacts. Our approach is based on a colorimetric method where aldehydes are initially stripped from the air into a scrubbing solution by means of a turning coil sampler tube and then derivatised with 3-methylbenzothiazolinone-2-hydrazone in acid media (pH?=??0.5). Hence, colourless aldehydes are transformed into blue dyes that are detected by UV–visible spectroscopy at 630 nm. Liquid core waveguide LCW Teflon® AF-2400 tube was used as innovative optical cells providing a HCHO detection limit of 4 pptv for 100 cm optical path with a time resolution of 15 min. This instrument showed good correlation with commonly used techniques for aldehydes analysis such as DNPH derivatisation chromatographic techniques with off-line and on-line samplers, and DOAS techniques (with deviation below 6 %) for both indoor and outdoor conditions. This instrument is associated with simplicity and low cost, which is a prerequisite for indoor monitoring.  相似文献   
967.
Olympic shooters discharge, annually, thousands of tons of lead shot which pose toxic risks to animals and may pollute both surface and ground waters. Non-toxic steel shot is an acceptable and effective substitute, but International Shooting Sports Federation (ISSF) rules prevent its adoption. The present policy and rules of the ISSF on lead shot use contravene the International Olympic Committee (IOC) Charter position on environmental protection. The United Nations Environment Programme (UNEP), a formal Olympic partner on environmental protection, has no stated policy on contamination from lead ammunition, despite having declared lead a Priority Area for remedial action, and is pressing to remove lead from the global human environment. The IOC Sport and Environment Commission and UNEP could examine the continued use of lead shot ammunition and advise the IOC Executive Board on appropriate changes in policy and rules that could halt the massive lead shot contamination of shooting range environments world-wide.  相似文献   
968.
The kinetics of the oxidation of sucralose, an emerging contaminant, and related monosaccharides and disaccharides by ferrate(VI) (Fe(VI)) were studied as a function of pH (6.5-10.1) at 25°C. Reducing sugars (glucose, fructose, and maltose) reacted faster with Fe(VI) than did the non-reducing sugar sucrose or its chlorinated derivative, sucralose. Second-order rate constants of the reactions of Fe(VI) with sucralose and disaccharides decreased with an increase in pH. The pH dependence was modeled by considering the reactivity of species of Fe(VI), (HFeO(4)(-) and FeO(4)(2-)) with the studied substrates. Second-order rate constants for the reaction of Fe(VI) with monosaccharides displayed an unusual variation with pH and were explained by considering the involvement of hydroxide in catalyzing the ring opening of the cyclic form of the carbohydrate at increased pH. The rate constants for the reactions of carbohydrates with Fe(VI) were compared with those for other oxidant species used in water treatment and were briefly discussed.  相似文献   
969.
970.
Emissions factors are important for estimating and characterizing emissions from sources of air pollution. There is no quantitative indication of uncertainty for these emission factors, most factors do not have an adequate data set to compute uncertainty, and it is very difficult to locate the data for those that do. The objectives are to compare the current emission factors of Electric Generating Unit NOx sources with currently available continuous emission monitoring data, develop quantitative uncertainty indicators for the Environmental Protection Agency (EPA) data quality rated emission factors, and determine the possible ranges of uncertainty associated with EPA's data quality rating of emission factors. EPA's data letter rating represents a general indication of the robustness of the emission factor and is assigned based on the estimated reliability of the tests used to develop the factor and on the quantity and representativeness of the data. Different sources and pollutants that have the same robustness in the measured emission factor and in the representativeness of the measured values are assumed to have a similar quantifiable uncertainty. For the purposes of comparison, we assume that the emission factor estimates from source categories with the same letter rating have enough robustness and consistency that we can quantify the uncertainty of these common emission factors based on the qualitative indication of data quality which is known for almost all factors. The results showed that EPA's current emission factor values for NOx emissions from combustion sources were found to be reasonably representative for some sources; however AP-42 values should be updated for over half of the sources to reflect current data. The quantified uncertainty ranges were found to be 25-62% for A rated emission factors, 45-75% for B rated emission factors, 60-82% for C rated emission factors, and 69-86% for D rated emission factors, and 82-92% for E rated emission factors.  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