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781.
Many marshes in the Gulf Coast Chenier Plain, USA, are managed through a combination of fall or winter burning and structural
marsh management (i.e., levees and water control structures; hereafter SMM). The goals of winter burning and SMM include improvement
of waterfowl and furbearer habitat, maintenance of historic isohaline lines, and creation and maintenance of emergent wetlands.
Although management practices are intended to influence the plant community, effects of these practices on primary productivity
have not been investigated. Marsh processes, such as vertical accretion and nutrient cycles, which depend on primary productivity
may be affected directly or indirectly by winter burning or SMM. We compared Chenier Plain plant community characteristics
(species composition and above- and belowground biomass) in experimentally burned and unburned control plots within impounded
and unimpounded marshes at 7 months (1996), 19 months (1997), and 31 months (1998) after burning. Burning and SMM did not
affect number of plant species or species composition in our experiment. For all three years combined, burned plots had higher
live above-ground biomass than did unburned plots. Total above-ground and dead above-ground biomasses were reduced in burned
plots for two and three years, respectively, compared to those in unburned control plots. During all three years, belowground
biomass was lower in impounded than in unimpounded marshes but did not differ between burn treatments. Our results clearly
indicate that current marsh management practices influence marsh primary productivity and may impact other marsh processes,
such as vertical accretion, that are dependent on organic matter accumulation and decay. 相似文献
782.
McComas KA 《Environmental management》2001,27(1):135-147
One of the more traditional ways to involve citizens in environmental management in the United States is to hold a public
meeting. Yet public meetings are also frequently criticized for stereotypical weaknesses, including a concern that citizens
who attend public meetings do not accurately represent citizens who do not attend. To examine this concern in the context
of local waste management problems, this study investigates whether citizens who attend public meetings differ from citizens
who do not attend meetings. In the spring of 1998, residents in two New York communities facing local waste management problems
received mailed questionnaires. Those surveyed included citizens who had previously attended state-sponsored public meetings
about the waste sites and citizens who lived within one mile of the respective waste sites but had not attended any meetings.
A comparison of demographic characteristics showed that, in both communities, citizens who attended meetings tended to report
higher incomes and have children living at home. In one community, previous meeting participants tended to perceive greater
risks from the waste site. In both communities, participants were less likely to consider certain sources of information about
the waste sites, including the state environmental agency, state health agency, and the industries, as credible. Regardless
of whether they had previously attended public meetings, respondents who perceived the risks as greater also perceived the
sources as less credible. The conclusions suggest some potential challenges to effective communication at public meetings,
including overcoming widespread skepticism and heightened concern among audience members. 相似文献
783.
Undamming Rivers: A Review of the Ecological Impacts of Dam Removal 总被引:26,自引:4,他引:22
Bednarek AT 《Environmental management》2001,27(6):803-814
Dam removal continues to garner attention as a potential river restoration tool. The increasing possibility of dam removal
through the FERC relicensing process, as well as through federal and state agency actions, makes a critical examination of
the ecological benefits and costs essential. This paper reviews the possible ecological impacts of dam removal using various
case studies.
Restoration of an unregulated flow regime has resulted in increased biotic diversity through the enhancement of preferred
spawning grounds or other habitat. By returning riverine conditions and sediment transport to formerly impounded areas, riffle/pool
sequences, gravel, and cobble have reappeared, along with increases in biotic diversity. Fish passage has been another benefit
of dam removal. However, the disappearance of the reservoir may also affect certain publicly desirable fisheries.
Short-term ecological impacts of dam removal include an increased sediment load that may cause suffocation and abrasion to
various biota and habitats. However, several recorded dam removals have suggested that the increased sediment load caused
by removal should be a short-term effect. Preremoval studies for contaminated sediment may be effective at controlling toxic
release problems.
Although monitoring and dam removal studies are limited, a continued examination of the possible ecological impacts is important
for quantifying the resistance and resilience of aquatic ecosystems. Dam removal, although controversial, is an important
alternative for river restoration. 相似文献
784.
In a recent paper, it was suggested that one of the reasons behind the decline in public regard toward British Columbia's
environmental movement was an increasingly negative portrayal of them by the print media. To investigate this suggestion,
we undertook a content analysis of print media reporting of forestry and environmental activities in the province's most widely
read newspaper, the Vancouver Sun, during 1993 and 1997. We hypothesized that if the print media did contribute to the decline in public regard toward the
environmental movement, we would find increasingly negative coverage of the environmental movement over the periods studied.
We also hypothesized that this would be accompanied by a decrease in the frequency of articles dealing with issues consistent
with the agenda of the environmental movement. We were not able to provide support for our initial hypothesis, nor did we
observe a decrease in coverage emphasizing the environmental issues. We did, however, observe an increase in coverage of articles
emphasizing typically proindustry issues with many more articles written with a proforestry slant in 1997 than articles written
in 1993. This suggests that there had been an agenda shift from environmentally oriented concerns in British Columbia to those
associated with the forest industry. As an explanation for the agenda shift, we point to changes in the management and reporting
philosophy at the Vancouver Sun, the emergence of an organized, proindustry counterframing strategy by the BC Forest Alliance, and the implementation of
several government policies aimed at regulating the activities of the forest industry. 相似文献
785.
Assessing Landscape Health: A Case Study from Northeastern Italy 总被引:17,自引:0,他引:17
Bertollo P 《Environmental management》2001,27(3):349-365
This article investigates the concept of biophysical landscape health for what are termed “highly governed landscapes.” It
proposes a definition of landscape health along with a preliminary diagnostic model and methods. The idea of landscape health
derives from the emerging integrative science of ecosystem health, which seeks to diagnose ecosystem condition as humans diagnose
human health. Highly governed landscapes, such as the reclaimed areas of coastal northeastern Italy, are landscapes that have
been subject to even greater degrees of human manipulation than normal cultural landscapes. These highly altered landscapes
are not easily served by existing environmental paradigms and concepts of health are seen to have numerous advantages. This
paper condenses a broader investigation of landscape health into three main sections. A brief review of the literature is
followed by a case study, which details two different phases of landscape transformation in the Lower Piave area of northeastern
Italy. A definition and general parameters of biophysical landscape health are then presented after this background stage.
Some key parameters of biophysical health include absence of distress and risk factors, sustainability, biodiversity, resilience,
and balance. For certain parameters, a preliminary landscape health diagnostic framework is presented that includes potential
diagnostic methods and thresholds based on findings from this case study. At the paper's conclusion, a summary diagnostic
model is presented, which suggests a process needed to implement landscape health assessment into practice. 相似文献
786.
Thapa GB 《Environmental management》2001,27(5):667-679
Mountain watersheds, comprising a substantial proportion of national territories of countries in mainland South and Southeast
Asia, are biophysical and socioeconomic entities, regulating the hydrological cycle, sequestrating carbon dioxide, and providing
natural resources for the benefit of people living in and outside the watersheds. A review of the literature reveals that
watersheds are undergoing degradation at varying rates caused by a myriad of factors ranging from national policies to farmers'
socioeconomic conditions. Many agencies—governmental and private—have tried to address the problem in selected watersheds.
Against the backdrop of the many causes of degradation, this study examines the evolving approaches to watershed management
and development. Until the early 1990s, watershed management planning and implementation followed a highly centralized approach
focused on heavily subsidized structural measures of soil conservation, planned and implemented without any consultation with
the mainstream development agencies and local people. Watershed management was either the sole responsibility of specially
created line agencies or a project authority established by external donors. As a consequence, the initiatives could not be
continued or contribute to effective conservation of watersheds. Cognizant of this, emphasis has been laid on integrated,
participatory approaches since the early 1990s. Based on an evaluation of experiences in mainland South and Southeast Asia,
this study finds not much change in the way that management plans are being prepared and executed. The emergence of a multitude
of independent watershed management agencies, with their own organizational structures and objectives and planning and implementation
systems has resulted in watershed management endeavors that have been in complete disarray. Consistent with the principle
of sustainable development, a real integrated, participatory approach requires area-specific conservation programs that are
well incorporated into integrated socioeconomic development plans prepared and implemented by local line agencies in cooperation
with nongovernment organizations (NGOs) and concerned people. 相似文献
787.
研究并比较了广东酸雨地区鹤山丘陵综合实验站区内不同类型森林降水的化学特征.结果表明,和大气降水相比,针阔叶林林内降水除NO3外其它离子含量都明显增加,马尾松针叶林冠层穿透雨和树干径流中离子含量增加倍数最高分别为34倍和12倍,阔叶林穿透雨和树干径流中离子含量增加倍数最高分别为8倍和10倍,针叶林降水比阔叶林降水离子富集程度较为显著.林内降水中马尾松针叶林树干径流离子总含量小于穿透雨离子总含量,阔叶林穿透雨离子总含量小于树干径流离子总含量.不同阔叶林型林内降水中离子含量是不同的.针叶林林内降水有进一步酸化趋势.林内降水离子富集导致森林冠层正负电荷数不平衡,营养离子大量淋失,使林冠层养分亏损. 相似文献
788.
采用低与高两个浓度组,进行慢与急性致毒效应实验结果表明,在低浓度组(0.5-30mg/L)锯缘青蟹没有发生急性毒性死亡的现象,但其摄食量呈现减少;在高浓度组(63~500mg/L)锯缘青蟹出现急性中毒死亡,且死亡率随毒物浓度的增加而上升,测得苯胺对锯缘青蟹的24hLC50为151±69mg/L;48h LC50为91.2±5.2mg/L.在致毒浓度范围内,锯缘青蟹对苯胺积累的富集因子接近1.6,这表明生物体与海水浓度之间存在某种配比平衡的关系。 相似文献
789.
790.
A case study of microwave processing of metal hydroxide sediment sludge from printed circuit board manufacturing wash water 总被引:2,自引:0,他引:2
The large quantity of wash water used in the electroplating and etching process in the manufacturing of printed circuit boards (PCBs) contains a high level of heavy metal ions (Cu++, Zn++, Ni++, Cr+++, Pb++). These potentially toxic ions are removed from the wash water effluent through a polyelectrolyte flocculation and hydroxide precipitation process during which a hydroxide sediment sludge rich in metal ions and polymers is generated. This sediment sludge possesses some unique characteristics and properties in terms of composition, fine particle size distribution, high specific surface area, and a tendency to agglomerate after drying. Direct disposal of this classified “special waste” (Department of Environment of Northern Ireland, The Special Waste Regulations, Northern Ireland, 1998) at landfill sites may cause serious soil and underground water pollution through a gradual ionic leaching process. This paper describes an experimental investigation, exploratory in nature, which employs microwave radiation for detoxification of the sediment sludge through microwave heating, drying and metal ion immobilization within the sediment solids. The effectiveness of microwave assisted binding and immobilization of the metal ions within the sediment solids was studied in conjunction with an evaluation of microwave energy efficiency in comparison to the more conventional convective heating and drying processes. Given a sufficient amount of microwave radiation, leaching of Cu2+ and Pb2+ was reduced by 2700% and 1080%, respectively, over a period of 12 weeks, and further leaching was not detectable within six months at simulated local landfill aqueous conditions. This paper also attempts, through experimental observation, to add to the very limited understanding of the complex interactions and binding of free metal ions with the polymeric materials and metal hydroxides under the influence of an electromagnetic field. The high specific surface of the sediment solids and their adsorption properties were further explored and characterized in a study of adsorption of reactive dyes by the microwave processed solids. 相似文献