全文获取类型
收费全文 | 776篇 |
免费 | 29篇 |
国内免费 | 4篇 |
专业分类
安全科学 | 26篇 |
废物处理 | 32篇 |
环保管理 | 193篇 |
综合类 | 54篇 |
基础理论 | 198篇 |
环境理论 | 2篇 |
污染及防治 | 238篇 |
评价与监测 | 36篇 |
社会与环境 | 24篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 19篇 |
2017年 | 18篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 14篇 |
2013年 | 84篇 |
2012年 | 21篇 |
2011年 | 30篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 35篇 |
2007年 | 44篇 |
2006年 | 45篇 |
2005年 | 25篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1998年 | 11篇 |
1997年 | 22篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1974年 | 7篇 |
1970年 | 3篇 |
1969年 | 3篇 |
排序方式: 共有809条查询结果,搜索用时 49 毫秒
61.
62.
63.
Wallace B. Smith Jack R. McDonald 《Journal of the Air & Waste Management Association (1995)》2013,63(2):168-172
Theories of particle charging based on boundary value solutions to the diffysional equation may not be applicable to electrostatic precipitators where the ion density is rarely more than an order of magnitude greafer than the particle concentration. A new charging equation, based on kinetic theory, is presented which evaluates the charging rate in terms of the probability of collisions between the flust particles and ions. In the presence of an external electric field, the surface of the particle is divided into three charging regions, and separate charging rates are calculated for each region. The total charging rate is the sum of these three individual rates. For large particles and high electric fields, this theory predicts essentially the same charging rate as the classical field charging equation of Rohmann and Pauthenier. For low electric fields, the theory reduces to White’s diffusional charging equation. Agreement is within 25% of Hewitt’s experimental results over the entire range of variables where data are available. For practical charging times, agreement is within 15%. 相似文献
64.
Hector Gutierrez-Bañuelos William E. Pinchak Byeng R. Min Gordon E. Carstens Robin C. Anderson Luis O. Tedeschi 《Journal of environmental science and health. Part. B》2013,48(4):360-365
Pathogenic bacteria attached to the hide or shed in the feces of cattle at slaughter can contaminate carcasses intended to be processed for human consumption. Therefore, new pre-harvest interventions are needed to prevent the carriage and excretion of foodborne pathogens in cattle presented to the processing plant. The objectives of this study were to examine the antimicrobial effects of hydrolysable tannin-rich chestnut and condensed tannin-rich mimosa extracts on bacterial indicators of foodborne pathogens when applied as a hide-intervention and as a feed additive to feedlot cattle. Water (control) or solutions (3 % wt/vol) of chestnut- and mimosa-extract treatments were sprayed (25 mL) at the left costal side of each animal to a 1000 cm2 area, divided in four equal quadrants. Hide-swabs samples obtained at pre-, 2-min, 8-h, and 24-h post-spray application were cultured to enumerate Escherichia coli/total coliforms and total aerobic plate counts. In a second experiment, diets supplemented without (controls) or with (1.5 % of diet dry matter) chestnut- or mimosa-extracts were fed during a 42–day experimental feeding period. Weekly fecal samples starting on day 0, and rumen fluid obtained on days 0, 7, 21 or 42 were cultured to enumerate E.coli/total coliforms and Campylobacter. Tannin spray application showed no effect of treatment or post-application-time (P> 0.05) on measured bacterial populations, averaging 1.7/1.8, 1.5/1.6 and 1.5/1.7 (log10 CFU/cm2) for E. coli/total coliforms, and 4.0, 3.4 and 4.2 (log10CFU/cm2) in total aerobes for control, chestnut and mimosa treatments, respectively. Mean (± SEM) ruminal E. coli and total coliform concentrations (log10 CFU/mL) were reduced (P< 0.01) in steers fed chestnut-tannins (3.6 and 3.8 ± 0.1) in comparison with the controls (4.1 and 4.2 ± 0.1). Fecal E. coli concentrations were affected by treatment (P< 0.01), showing the highest values (log10 CFU/g) in fecal contents from mimosa-fed steers compared to controls (5.9 versus 5.6 ± 0.1 SEM, respectively). Total coliforms (log CFU/g) showed the highest values (P< 0.01) in feces from chestnut- and mimosa-fed steers (6.0 and 6.1 ± 0.1 respectively) in comparison with controls (5.7 ± 0.1). Fecal Campylobacter concentrations (log10CFU/g) were affected by treatment (P< 0.05), day (P< 0.001) and their interaction (P< 0.01) with the controls having lower concentrations than chestnut- and mimosa-fed steers (0.4, 1.0, and 0.8 ± 0.3, respectively). It was concluded that under our research conditions, tannins were not effective in decreasing measured bacterial populations on beef cattle hides. Additionally, chestnut tannin reduced E. coli and total coliforms within the rumen but the antimicrobial effect was not maintained in the lower gastrointestinal tract. Further research is necessary to elucidate the possible antimicrobial effects of tannins at site-specific locations of the gastrointestinal tract in beef cattle fed high-grain and high-forage diets. 相似文献
65.
Joris Mergaert Caroline Anderson Ann Wouters Jean Swings 《Journal of Polymers and the Environment》1994,2(3):177-183
The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) [P(3HB)] or copolymers with 10% [P(3HB-co-10%3HV)] and 20% [P(3HB-co-20%3HV)] 3-hydroxyvaleric acid was studied in small household compost heaps. Degradation was measured through loss of weight (surface erosion) and changes in molecular weight and mechanical strength. It was concluded, on the basis of weight loss and loss of mechanical properties, that P(3HB) and P(3HB-co-3HV) plastics were degraded in compost by the action of microorganisms. No decrease inM
w could be detected during the degradation process. The P(3HB-co-20%3HV) copolymer was degraded much faster than the homopolymer and P(3HB-co-10%3HV). One hundred nine microbial strains capable of degrading the polymersin vitro were isolated from the samples used in the biodegradation studies, as well as from two other composts, and identified. They consisted of 61 Gram-negative bacteria (e.g.,Acidovorax facilis), 10 Gram-positive bacteria (mainlyBacillus megaterium), 35Streptomyces strains, and 3 molds. 相似文献
66.
The Toxics Release Inventory (TRI) created by the 1986 Emergency Planning and Community Right-to-Know Act initially received
limited attention. During the early years of its implementation, the TRI has become the basis for a national experiment in
voluntaristic problem solving among citizens and industry, but that process of environmental democracy hinges on citizens'
ability to actually acquire, understand, and apply the new data on industrial toxic emissions. A national study of TRI-using
organizations in the public and private sectors reveals that effective citizen access depends in part on the efforts of intermediary
public interest groups to bridge individual needs and right-to-know data. Although the TRI has had early success as a supplement
to conventional command and control regulation, questions exist about the extent to which state and federal government should
or must provide special efforts to make environmental information access work for citizens. 相似文献
67.
This study concerns design features of urban parking lots which can increase the perception of such areas as both safe and attractive. College students evaluated the attractiveness and perceived security associated with 180 scenes of parking lots adjacent to commercial and multi-family residential structures in Atlanta and Athens, Georgia, U.S.A. High intergroup correlations (r > 0·90) indicated the reliability of evaluations of both perceived features. Regressions of physical features on perceived security ratings and attractiveness ratings yielded highly predictive models (R2 = 0·76 and 0·80, respectively). For both sets of ratings a Maintenance and Design factor accounted for the most variance. Although attractiveness ratings were higher as the total amount of vegetation increased in a scene, security was in general rated higher only when vegetation was well maintained and appeared to be installed as part of a landscape design. Attractiveness was generally higher for multi-family residential scenes than for commercial scenes. Perceived security was higher for frontal views of structures, especially when entrances were proximate to the viewer. Research implications are discussed in terms of the impact of natural features in urban areas for increasing attractiveness and reducing fear of crime. 相似文献
68.
A series of studies examined the effects of labelled meaning on affective response to housing scenes. Students at Ohio State University assessed their feelings towards imagined housing (public or private) and cities (Memphis, Houston and San Francisco). Expected differences in the affective quality were found. Responses to color photographs of specific housing scenes labelled as either private condominiums or public housing were obtained. Differences in scene-affect as a function of labelled meaning were found. Responses to housing scenes labelled as located in either Memphis, Houston or San Francisco revealed no differences in scene-affect as a function of label meaning. This latter finding was confirmed in a non-repeated measure examination. Differences in the fittingness, potency or relevance of the information provided may account for the pattern of findings. 相似文献
69.
The author describes his background and relationship to the behavioral geography revolution at Clark. Key events included the independent invention of ‘turf maps’, the Place Perception Project of Blaut, Stea and McCleary, and the synergy of an exceptional cluster of faculty and students. The influence of the revolution on the author's own research has resulted in a radical redirection of effort toward applied research on children's environmental behavior, geographic learning, and participatory design methods in particular. 相似文献
70.
The starch content and its composition have important consequences for the yield of the harvested crop and the materials extracted from it. The functional properties of the foods or other processed materials derived from these crops are also affected by the structure and composition of the starch. Recently, genetic engineering has been used to produce plants with an elevated starch content, achieved by transforming the plant with a mutated bacterial gene coding for an ADPglucose pyrophosphorylase that is active in the presence of metabolites which inhibit the plant enzyme. Besides the practical implications of these results, this experiment provided direct evidence for the regulatory role of the ADPglucose pyrophosphorylase in starch synthesis. Other bacterial enzymes, such as glycogen synthase and branching enzyme, could be introduced in order to modify starch structure. However, a more elegant (but longer-term) approach would be to learn enough about the structure-function relationships of the plant enzymes so that the product of their action could be changed. To achieve this objective, much more will have to be learned about the enzymes involved in the biosynthesis of starch than is presently known. Here, the basic properties of starch and the current research approaches to understanding its biosynthesis are described, together with a perspective of how genetic manipulation of starch structure may be achieved.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts. 相似文献