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   159篇
  免费   3篇
  国内免费   1篇
安全科学   16篇
废物处理   5篇
环保管理   37篇
综合类   15篇
基础理论   27篇
污染及防治   37篇
评价与监测   19篇
社会与环境   4篇
灾害及防治   3篇
  2023年   2篇
  2022年   1篇
  2021年   2篇
  2020年   5篇
  2019年   2篇
  2018年   4篇
  2017年   4篇
  2016年   1篇
  2015年   4篇
  2014年   7篇
  2013年   14篇
  2012年   5篇
  2011年   9篇
  2010年   5篇
  2009年   8篇
  2008年   14篇
  2007年   12篇
  2006年   9篇
  2005年   5篇
  2004年   5篇
  2003年   9篇
  2002年   4篇
  2001年   1篇
  2000年   3篇
  1999年   3篇
  1998年   3篇
  1996年   4篇
  1995年   3篇
  1994年   1篇
  1993年   3篇
  1991年   3篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1982年   1篇
  1977年   1篇
排序方式: 共有163条查询结果,搜索用时 359 毫秒
51.
Awareness of the ISO 14000 standards is increasing around the world. There is a general acceptance of the need for such standards to promote environmental protection and international trade, but concerns exist regarding potential trade barriers. This article provides some insights into the varying attitudes toward ISO 14000 in countries from all parts of the globe.  相似文献   
52.
Mink (Mustela vison) carcasses were collected from local commercial trappers from fall 1998 to spring 2003 from tributaries and marshes within 4.8km from the shores of Lakes Erie and St. Clair, including the Wheatley Harbour and St. Clair River Areas of Concern (AOCs), as well as from inland sites (8 to 40km from shore). Liver concentrations, on a lipid weight basis, of chlorinated hydrocarbons were measured and compared among sites and to tissue concentrations of mink from two previous collections from similar sites over the past 25 years. Mink from the western Lake Erie sites, which included the Wheatley Harbour AOC, had significantly higher concentrations of sum PCBs and PCB Aroclors than those from the St. Clair corridor or inland sites, with concentrations from the rest of Lake Erie being intermediate. Dieldrin concentrations were also significantly higher in western Lake Erie than many other sites, and those of oxychlordane and mirex also tended to be higher (0.05 < p < 0.1). There were no differences in contaminant concentrations between the St. Clair River AOC and the downstream non-AOC Lake St. Clair site, with the exception of slightly higher levels of octachlorostyrene (OCS). Concentrations of PCBs and other chlorinated hydrocarbons in mink showed a general decrease over the past two decades. In contrast, PCBs and some organochlorine pesticides tended to increase, significantly so with oxychlordane, in western Lake Erie mink over the same time period. DDE declined at all sites. Currently, mink liver PCB concentrations are within the range associated with reproductive impairment, as determined from captive mink studies, in 11.7% of all animals collected from the Lakes Erie and St. Clair basin overall, but in almost 40% of individuals from western Lake Erie.  相似文献   
53.
A trickling filter/solid contact (TF/SC) biological secondary treatment plant with chlorine disinfection serving a suburban population of 740,000 was assessed for environmental estrogens. Weekly grab samples were taken at established sampling points and analyzed for various pertinent environmental estrogens including industrial chemicals, and natural and synthetic steroidal estrogens. Additionally, human estrogen receptor (hER) activity and capacity to elicit intersex/sex reversal for the wastewater was monitored using a recombinant yeast assay and whole fish exposures, respectively. hER activity levels varied from 76 to 106 ng/L E2 equivalents in the primary effluent, and were reduced by 25% by biological treatment. For the primary and final effluent no evidence of sex reversal or intersex was apparent in any of the treatment groups (1%, 3%, 10%, or 100%) based on genetic sex determinations and histological examination of the gonads in alevin from 28 d exposed chinook salmon (Oncorhynchus tshawytscha) eggs.  相似文献   
54.
In 2006 the Massachusetts Toxics Use Reduction Institute conducted a study to determine if states could identify safer alternatives to five chemicals of concern. The chemicals investigated included di (2-ethylhexyl) phthalate (DEHP), formaldehyde, hexavalent chromium, lead and perchloroethylene. First, the Institute developed a methodology for assessing alternatives to these five chemicals that allowed it to quickly determine priority uses and alternatives to assess and to research the pertinent decision criteria, which included performance, technical, financial environmental and human health parameters. The methodology included important feedback from stakeholders in the state, which helped to focus and enhance the value of the work. Second, the Institute implemented the methodology over a ten month period. Based on the activities conducted by the Institute, safer alternatives were identified for each of the priority uses associated with the five chemicals studied. This report summarizes the methodology employed and provides examples of the results for one of the five chemicals, namely DEHP. The experience of the Institute and the information contained in this report indicates that alternatives assessment was a useful approach to organizing and evaluating information about chemicals and alternatives.  相似文献   
55.
Sperm transfer via spermatophores is common among organisms living in mesopsammic environments, and is generally considered to be an evolutionary adaptation to reproductive constraints in this habitat. However, conclusions about adaptations and trends in insemination across all interstitial taxa cannot be certain as differences in mode of insemination via spermatophores do exist, details of insemination are lacking for many species, and evolutionary relationships in many cases are poorly known. Opisthobranch gastropods typically transfer sperm via reciprocal copulation, but many mesopsammic Acochlidia are aphallic and transfer sperm via spermatophores, supposedly combined with dermal fertilisation. The present study investigates structural and functional aspects of sperm transfer in the Mediterranean microhedylacean acochlid Pontohedyle milaschewitchii. We show that spermatophore attachment is imprecise. We describe the histology and ultrastructure of the two-layered spermatophore and discuss possible functions. Using DAPI staining of the (sperm-) nuclei, we document true dermal insemination in situ under the fluorescence microscope. Ultrastructural investigation and computer-based 3D reconstruction from TEM sections visualise the entire spermatozoon including the exceptionally elongate, screw-like keeled sperm nucleus. An acrosomal complex was not detected. From their special structure and behaviour we conclude that sperm penetrate epithelia, tissues and cells mechanically by drilling rather than lysis. Among opisthobranchs, dermal insemination is limited to mesopsammic acochlidian species. In this spatially limited environment, a rapid though imprecise and potentially harmful dermal insemination is discussed as a key evolutionary innovation that could have enabled the species diversification of microhedylacean acochlidians.  相似文献   
56.
Molecular Systematics and the Conservation of Rare Species   总被引:10,自引:0,他引:10  
Abstract: Despite the tradition of systematic biology as the science of diversity, systematics has until recently contributed relatively little to the theory and practice of conservation biology. We identify four areas in which systematics could contribute to the conservation of rare plant species: (1) species concepts, (2) the identification of lineages worthy of conservation, (3) the setting of conservation priorities, and (4) the effects of hybridization on the biology and conservation of rare species. Species concepts that incorporate history and reflect phylogeny ultimately will be more useful for preserving biodiversity than those that do not. Phylogenetic analyses involving conspecific populations often reveal multiple lineages that may warrant protection as evolutionarily distinct units. Phylogenetic information also should be considered in setting priorities for conservation. Systematics provides the tools for inferring relationships among organisms and, in conjunction with biogeography, for identifying those areas that harbor many actively speciating groups. Hybridization may lead to the extinction of a rare species, but in other cases, ironically, artificial hybridization with a more widespread congener may be the only way to preserve the gene pool of a rare species. We appeal to systematists to contribute actively to both conservation theory and practice, and we call for the integration of systematics in the establishment of conservation priorities and the development of strategies to preserve Earth's biota.  相似文献   
57.
Although the transactional model of the stress process (Lazarus, 1966, 1993; Lazarus and Folkman, 1984, 1987) continues to be utilized in a significant amount of stress research, much of the current literature on job stress focuses on pinpointing objective stressors. This paper examines Lazarus' transactional appraisal approach and includes a specific discussion of the process by which employees' attributions regarding stressors and the resulting emotions significantly influence their choices of coping mechanisms. Given that a single work event can be interpreted in a variety of ways, the role of individuals' cognitive processing is being ignored by much of the current empirical stress research. This paper examines and highlights the importance of the cognitive and emotional components within the organizational stress process. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   
58.
The CA Department of Pesticide Regulation (CDPR) and the CA Air Resources Board monitored 40 pesticides, including five degradation products, in Parlier, CA, to determine if its residents were exposed to any of these pesticides and, if so, in what amounts. They included 1,3-dichloropropene, acrolein, arsenic, azinphos-methyl, carbon disulfide, chlorpyrifos and its degradation product, chlorthalonil, copper, cypermethrin, diazinon and its degradation product, dichlorvos, dicofol, dimethoate and its degradation product, diuron, endosulfan and its degradation product, S-ethyl dipropylcarbamothioate (EPTC), formaldehyde, malathion and its degradation product, methyl isothiocyanate (MITC), methyl bromide, metolachlor, molinate, norflurazon, oryzalin, oxyfluorfen, permethrin, phosmet, propanil, propargite, simazine, SSS-tributylphosphorotrithioate, sulfur, thiobencarb, trifluralin, and xylene. Monitoring was conducted 3 days per week for a year. Twenty-three pesticides and degradation products were detected. Acrolein, arsenic, carbon disulfide, chlorpyrifos, copper, formaldehyde, methyl bromide, MITC, and sulfur were detected in more than half the samples. Since no regulatory ambient air standards exist for these pesticides, CDPR developed advisory, health-based non-cancer screening levels (SLs) to assess acute, subchronic, and chronic exposures. For carcinogenic pesticides, CDPR assessed risk using cancer potency values. Amongst non-carcinogenic agricultural use pesticides, only diazinon exceeded its SL. For carcinogens, 1,3-dichloropropene concentrations exceeded its cancer potency value. Based on these findings, CDPR has undertaken a more comprehensive evaluation of 1,3-dichloropropene, diazinon, and the closely related chlorpyrifos that was frequently detected. Four chemicals—acrolein, arsenic, carbon disulfide, and formaldehyde—sometimes used as pesticides were detected, although no pesticidal use was reported in the area during this study. Their presence was most likely due to vehicular or industrial emissions.  相似文献   
59.
60.
An operating Pd//D2O, Li+, Cl//Pt cell, placed in an external electrostatic field, yielded unexpected results, viz. (i) Morphological changes in the form of discrete sites exhibiting molten-like features, i.e. features that require substantial energy expenditure. (ii) Presence of elements (Al, Mg, Ca, Si, Zn, ...) that could not be extracted from cell components and deposited on discrete sites. The cell design and the experimental protocol assuring reproducibility is described in detail.  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