全文获取类型
收费全文 | 274篇 |
免费 | 14篇 |
国内免费 | 85篇 |
专业分类
安全科学 | 12篇 |
废物处理 | 5篇 |
环保管理 | 30篇 |
综合类 | 227篇 |
基础理论 | 61篇 |
环境理论 | 1篇 |
污染及防治 | 18篇 |
评价与监测 | 8篇 |
社会与环境 | 8篇 |
灾害及防治 | 3篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 9篇 |
2013年 | 16篇 |
2012年 | 12篇 |
2011年 | 18篇 |
2010年 | 18篇 |
2009年 | 20篇 |
2008年 | 9篇 |
2007年 | 17篇 |
2006年 | 18篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 20篇 |
2001年 | 22篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 12篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1984年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有373条查询结果,搜索用时 703 毫秒
21.
Andreas Behrends Sonja Riediger Sascha Grube Burkhard Poeggeler Chandana Haldar Rüdiger Hardeland 《Journal of environmental science and health. Part. B》2013,48(6):599-606
The redox-active quinalphos main metabolite, 2-hydroxyquinoxaline, is particularly effective under excitation by light. We have studied the photocatalytic destruction of melatonin and its precursors, because the cytoprotective indoleamine has been detected in high quantities in mammalian skin. In photooxidation reactions, in which melatonin, N-acetylserotonin and serotonin are destroyed by 2-hydroxyquinoxaline, the photocatalyst is virtually not consumed. Rates of melatonin and serotonin destruction are not changed by the singlet oxygen quencher 1,4-diazabicyclo-(2,2,2)-octane, indicating that this oxygen species is not involved in the primary reactions, so that the persistence of 2-hydroxyquinoxaline has to be explained by redox cycling. This should imply formation of an organic radical, presumably the quinoxaline-2-oxyl radical, from which 2-hydroxyquinoxaline is regenerated by electron abstraction from indolic radical scavengers. Electron donation by 2-hydroxyquinoxaline is demonstrated by reduction of the 2,2′-azino-bis-(3-ethylbenzthiazolinyl-6-sulfonic acid) cation radical under ultrasound excitation. The compound 2-hydroxyquinoxaline interacts with the specific superoxide anion scavenger Tiron. Formation of oligomeric products from melatonin and serotonin is strongly inhibited by sodium dithionite. Products from photocatalytic indolamine conversion are predominantly dimers and oligomers. No kynuramines were detected in the case of serotonin oxidation, and melatonin's otherwise prevailing oxidation product N 1-acetyl-N 2-formyl-5-methoxykynuramine, another cytoprotective metabolite, is only formed in relatively small quantities. The proportion between products from melatonin is changed by 1,4-diazabicyclo-(2,2,2)-octane: singlet oxygen, also formed under the influence of excited 2-hydroxyquinoxaline, only affects secondary reactions. 相似文献
22.
四川东部沱江乡茎瘤芥产地的地球化学特征 总被引:2,自引:0,他引:2
通过对四川省东部沱江乡茎瘤芥产区土壤的地球化学特征研究和茎瘤芥产区的土壤测试分析,并将其与全国土壤背景值比较,摸清了茎瘤芥产区土壤的元素本底特征。沱江乡茎瘤芥产区土壤Zn、Fe、Mn、Mg、K、B、P元素含量高于全国土壤平均含量,有益元素Mo、Ca、Si、Se均比全国平均值低,重金属Cr、Hg、Cd、Pb含量比全国平均值高,As元素含量则低于全国平均值水平,产区土壤中存在的Cd元素超出国家环境质量一级标准,但符合二级土壤质量标准,其他元素符合绿色蔬菜产地环境标准。 相似文献
23.
Subsurface agricultural drainage waters from western San Joaquin Valley, California, were found to contain elevated concentrations of the element selenium in the form of selenate. In 1978, these drainage waters began to replace previous input to Kesterson Reservoir, a pond system within Kesterson National Wildlife Refuge; this substitution was completed by 1982. In the 1983 nesting season, unusual rates of deformity and death in embryos and hatchlings of wild aquatic birds (up to 64% of eared grebe and American coot nests) occurred at the refuge and were attributed to selenium toxicosis. Features necessary for contamination to have taken place included geologic setting, climate, soil type, availability of imported irrigation water, type of irrigation, and the unique chemical properties of selenium. The mechanisms of biogeochemical cycling raise questions about other ecosystems and human exposure. 相似文献
24.
Jirka ;imnek Diederik Jacques Martinus Th. Van Genuchten Dirk Mallants 《Journal of the American Water Resources Association》2006,42(6):1537-1547
Abstract: The transport of reactive contaminants in the subsurface is generally affected by a large number of nonlinear and often interactive physical, chemical, and biological processes. Simulating these processes requires a comprehensive reactive transport code that couples the physical processes of water flow and advective-dispersive transport with a range of biogeochemical processes. Two recently developed coupled geochemical models that are both based on the HYDRUS-1D software package for variably saturated flow and transport are summarized in this paper. One model resulted from coupling HYDRUS-1D with the UNSATCHEM module. While restricted to major ion chemistry, this program enables quantitative predictions of such problems as analyzing the effects of salinity on plant growth and the amount of water and amendments required to reclaim salt-affected soil profiles. The second model, HPI, resulted from coupling HYDRUS-1D with the PHREEQC biogeochemical code. The latter program accounts for a wide range of instantaneous or kinetic chemical and biological reactions, including complexation, cation exchange, surface complexation, precipitation dissolution and/or redox reactions. The versatility of HP1 is illustrated in this paper by means of two examples: the leaching of toxic trace elements and the transport of the explosive TNT and its degradation products. 相似文献
25.
Md. Abdullah Yousuf Al Harun Joshua Johnson Md. Nazim Uddin Randall W. Robinson 《环境科学学报(英文版)》2015,27(7):1-11
Decomposition of plant litter is a fundamental process in ecosystem function, carbon and nutrient cycling and, by extension, climate change. This study aimed to investigate the role of temperature on the decomposition of water soluble phenolics(WSP), carbon and soil nutrients in conjunction with the phytotoxicity dynamics of Chrysanthemoides monilifera subsp. monilifera(boneseed) litter. Treatments consisted of three factors including decomposition materials(litter alone, litter with soil and soil alone), decomposition periods and temperatures(5–15, 15–25and 25–35°C(night/day)). Leachates were collected on 0, 5, 10, 20, 40 and 60 th days to analyse physico-chemical parameters and phytotoxicity. Water soluble phenolics and dissolved organic carbon(DOC) increased with increasing temperature while nutrients like SO-24 and NO-13 decreased. Speed of germination, hypocotyl and radical length and weight of Lactuca sativa exposed to leachates were decreased with increasing decomposition temperature. All treatment components had significant effects on these parameters. There had a strong correlation between DOC and WSP, and WSP content of the leachates with radical length of test species. This study identified complex interactivity among temperature, WSP, DOC and soil nutrient dynamics of litter occupied soil and that these factors work together to influence phytotoxicity. 相似文献
26.
贵阳市土壤地球化学背景与生态环境分析 总被引:1,自引:0,他引:1
通过1∶250 000多目标区域地球化学调查,获得了贵阳市及邻区表、深层土壤中54项化学指标的地球化学背景值、基准值等参数。研究区总体土壤环境呈中偏酸性,对生态环境影响较大。土壤化学物质组成丰富,地球化学背景分布不均匀。除活动性强的化学组分对成土母质有分异外,多数化学组分对成土母质继承性显著。表层土壤有机碳、全碳、硫、氮、硒、氟和汞、镉、砷等的地球化学背景值显著高于深层土壤和我国其它城市地球化学基准值。前者适宜发展生态富硒特色农业,后者表明土壤环境安全形势严峻。土壤地球化学背景为生态环境评价和其它相关学科研究提供了科学基础,由此提出生态环境保护和利用建议。 相似文献
27.
28.
通过对湘西北地区黑色泥灰岩风化剖面(DM剖面)中Cr、Ni、Cu、Zn、Cd、Pb、Th、U 8种重金属元素地球化学特征的研究,并与区域上发育于黑色页岩的2条风化剖面的对比分析,初步揭示了黑色泥灰岩风化剖面中重金属富集的地球化学机制。结果表明:(1)与黑色页岩相比,黑色泥灰岩风化成土过程中重金属元素普遍呈现出低背景、高富集的地球化学特征。(2)黑色泥灰岩风化剖面的形成,是在基岩中碳酸盐快速溶蚀的基础上(基岩的酸溶相含量为78.57%),由酸不溶相进一步演化的结果。在此过程中,对于无明显外源输入的元素Cr、Ni、Cu、Zn、Pb、Th、U,一方面,赋存在酸溶相的部分随碳酸盐的淋失而亏损甚至强烈亏损(其中Th相对惰性);另一方面,残余在酸不溶相的部分因基岩中大量碳酸盐的淋失而显著富集,且随风化剖面的演化未显示出进一步的亏损。因此,这些元素在风化剖面中的富集是绝对(强烈)亏损和显著相对富集的综合结果。对于Cd,存在明显的外源输入,可能主要以水溶态形式带入并大量淀积在剖面下部。(3)在黑色泥灰岩风化剖面,有机质(OM)不是重金属元素的主要赋存介质,其对重金属元素地球化学行为的影响有限。(4)黑色泥灰岩发育的土壤中,Cu和Cd的平均含量分别为54.58 mg/kg和0.58 mg/kg,高于农用地土壤污染风险筛选值,特别是Cd,对土壤生态环境可能形成不利影响,应引起关注。 相似文献
29.
Fingerprinting Global Climate Change and Forest Management Within Rhizosphere Carbon and Nutrient Cycling Processes 总被引:2,自引:0,他引:2
As one of the two Principal Subject Editors for ESPR Subject Area 1 'Terrestrial Ecology and Biology / Soil and Sediments: Toxicology-related Subjects' (see pp 287-293), the senior author and his colleague, Dr Chen, present an example of sub-category 4 'Environmental studies of pesticides, air pollution, and management strategies for forestry and plant ecosystems'. Thereby, they inform the ESPR community about the new Australian research project concerning the fingerprints of global climate change (GCC) and forest management on rhizosphere carbon and nutrient cycling and, subsequently, present an overview on the GCC and forest management fingerprints. 相似文献
30.
AbstractObjective: The number of e-bike users has increased significantly over the past few years and with it the associated safety concerns. Because e-bikes are faster than conventional bicycles and more prone to be in conflict with road users, e-bikers may need to perform avoidance maneuvers more frequently. Braking is the most common avoidance maneuver but is also a complex and critical task in emergency situations, because cyclists must reduce speed quickly without losing balance. The aim of this study is to understand the braking strategies of e-bikers in real-world traffic environments and to assess their road safety implications. This article investigates (1) how cyclists on e-bikes use front and rear brakes during routine cycling and (2) whether this behavior changes during unexpected conflicts with other road users.Methods: Naturalistic data were collected from 6 regular bicycle riders who each rode e-bikes during a period of 2 weeks, for a total of 32.5?h of data. Braking events were identified and characterized through a combined analysis of brake pressure at each wheel, velocity, and longitudinal acceleration. Furthermore, the braking patterns obtained during unexpected events were compared with braking patterns during routine cycling.Results: In the majority of braking events during routine cycling, cyclists used only one brake at a time, favoring one of the 2 brakes according to a personal pre-established pattern. However, the favored brake varied among cyclists: 66% favored the rear brake and 16% the front brake. Only 16% of the cyclists showed no clear preference, variously using rear brake, front brake, or combined braking (both brakes at the same time), suggesting that the selection of which brake to use depended on the characteristics of the specific scenario experienced by the cyclist rather than on a personal preference. In unexpected conflicts, generally requiring a larger deceleration, combined braking became more prevalent for most of the cyclists; still, when combined braking was not applied, cyclists continued to use the favored brake of routine cycling. Kinematic analysis revealed that, when larger decelerations were required, cyclists more frequently used combined braking instead of single braking.Conclusions: The results provide new insights into the behavior of cyclists on e-bikes and may provide support in the development of safety measures including guidelines and best practices for optimal brake use. The results may also inform the design of braking systems intended to reduce the complexity of the braking operation. 相似文献