全文获取类型
收费全文 | 8106篇 |
免费 | 568篇 |
国内免费 | 270篇 |
专业分类
安全科学 | 1617篇 |
废物处理 | 139篇 |
环保管理 | 3069篇 |
综合类 | 2126篇 |
基础理论 | 809篇 |
环境理论 | 10篇 |
污染及防治 | 214篇 |
评价与监测 | 334篇 |
社会与环境 | 345篇 |
灾害及防治 | 281篇 |
出版年
2023年 | 85篇 |
2022年 | 112篇 |
2021年 | 179篇 |
2020年 | 243篇 |
2019年 | 190篇 |
2018年 | 166篇 |
2017年 | 219篇 |
2016年 | 307篇 |
2015年 | 253篇 |
2014年 | 316篇 |
2013年 | 456篇 |
2012年 | 449篇 |
2011年 | 575篇 |
2010年 | 385篇 |
2009年 | 494篇 |
2008年 | 365篇 |
2007年 | 473篇 |
2006年 | 469篇 |
2005年 | 361篇 |
2004年 | 392篇 |
2003年 | 296篇 |
2002年 | 279篇 |
2001年 | 271篇 |
2000年 | 271篇 |
1999年 | 206篇 |
1998年 | 133篇 |
1997年 | 135篇 |
1996年 | 110篇 |
1995年 | 105篇 |
1994年 | 49篇 |
1993年 | 62篇 |
1992年 | 57篇 |
1991年 | 47篇 |
1990年 | 33篇 |
1989年 | 27篇 |
1988年 | 34篇 |
1987年 | 33篇 |
1986年 | 27篇 |
1985年 | 23篇 |
1984年 | 28篇 |
1983年 | 17篇 |
1982年 | 22篇 |
1981年 | 18篇 |
1980年 | 24篇 |
1979年 | 33篇 |
1978年 | 21篇 |
1975年 | 14篇 |
1973年 | 14篇 |
1972年 | 16篇 |
1971年 | 14篇 |
排序方式: 共有8944条查询结果,搜索用时 468 毫秒
831.
Conservation strategies for effective land management of protected areas using an erosion prediction information system (EPIS) 总被引:1,自引:0,他引:1
This research demonstrates the predictive modeling capabilities of a geographic information system (GIS)-based soil erosion potential model to assess the effects of implementing land use change within a tropical watershed. The Revised Universal Soil Loss Equation (RUSLE) was integrated with a GIS to produce an Erosion Prediction Information System (EPIS) and modified to reflect conditions found in the mountainous tropics. Research was conducted in the Zenzontia subcatchment of the Río Ayuquíla, located within the Sierra de Manantlán Biosphere Reserve (SMBR), México. Expanding agricultural activities within this area will accentuate the already high rate of soil erosion and resultant sediment loading occurring in the Río Ayuquíla. Two land-use change scenarios are modeled with the EPIS: (1) implementation of soil conservation practices in erosion prone locations; and (2) selection of sites for agricultural expansion which minimize potential soil loss. Confronted with limited financial resources and the necessity for expedient action, managers of the SMBR can draw upon the predictive capacity of the EPIS to facilitate rapid and informed land-use planning decisions. 相似文献
832.
Methodological Development of an Index of Coastal Water Quality: Application in a Tourist Area 总被引:2,自引:0,他引:2
With the aim of obtaining an index of coastal water quality, a methodological procedure based on numerical classification and discriminant analysis is presented. The procedure was applied to nutrient data (ammonia, nitrite, nitrate, and phosphate) analyzed along the coastal waters of a Spanish tourist area. Using numerical classification, three levels of nutrient loading were revealed, characterizing oligotrophic, mesotrophic, and potentially eutrophic waters. Discriminant analysis was shown to be an effective methodological tool in the discrimination between trophic groups. For every group, the discriminant procedure generated the centroids. The centroids representing oligotrophic and potentially eutrophic conditions were used to establish the two extremes of the continuum of mesotrophic conditions in these coastal waters: Standardizing values from -1 to 1, the centroids for oligotrophic and potentially eutrophic waters yielded an interval that defined the range of mesotrophic conditions. This interval is proposed as a water quality index. The ability of the coastal water quality index to successfully predict mesotrophic conditions was proved with random samples. 相似文献
833.
Benefits-based management seeks to provide recreation benefits for recreation participants by managing the physical environments
in which recreation occurs. This study investigates the relationship between benefits desired by visitors and the physical,
social, and managerial characteristics of settings that facilitate realization of recreation benefits. Data such as perceived
benefits from recreation experiences, setting attributes that significantly influenced perceived benefits, and sociodemographic
variables were collected from 376 visitors to Sorak-san National Park in the eastern part of the Korean peninsula. Cluster
analysis was used to group visitors' desired benefits into 12 domains: relationship with nature/scenery, escaping pressure,
learning about nature, family togetherness, introspection, exploration, autonomy/achievement, being with friends, leading
others, skills/learning, risk taking, and meeting/observing new people. Multiple regression was used to link benefit domains
with the characteristics of settings. The social attribute of recreation settings was linked to eight of the ten benefit domains.
There were two statistically strong multiple regression correlations: (1) between domain of “relationship with nature /scenery”
and the attributes “forest/water,”“attractive nature,” and “facility/maintenance” and (2) between the domain of “escaping
pressure” and the attributes “attractive nature” and “social.” The results of this study are useful to managers in their efforts
to provide recreation opportunities for visitors to achieve beneficial outcomes. 相似文献
834.
Past tree colonization dynamics of a powerline-right-of-way (ROW) corridor in the Haut-Saint-Laurent region of Quebec was studied based on the present age distribution of its tree populations. This colonization study spans 20 years, from 1977 (ROW clearance) to 1996. The sampled quadrats were classified into six vegetation types. Tree colonization dynamics were interpreted in each type, and three distinct patterns were identified. (1) Communities adapted to acidic conditions were heavily colonized by Acer rubrum, at least for the last 12 years. (2) Communities adapted to mesic or to hydric conditions were more intensely colonized in the period 1985-1987 than in the following 9 years; this past success in tree colonization may have been caused by herbicide treatments, which could have facilitated tree establishment by damaging the herbaceous and shrub vegetation. (3) Cattail, vine-raspberry, and reed-dominated communities contained few tree individuals, with almost all trees establishing between 1979 and 1990; those three vegetation types appear as the most resistant to tree invasion in the ROW studied. This study supports the need for an integrated approach in ROW vegetation management, in which the selection of vegetation treatment methods would depend on the tree colonization dynamics in each vegetation type. Minimizing disturbances inflicted on ROW herbaceous and shrub covers should be the central strategy because disturbances jeopardize natural resistance to future tree invasion, except in communities adapted to acidic conditions where the existing vegetation does not prevent invasion by A. rubrum. Many trees are surviving the successive cutting operations by producing new sprouts each time, particularly in communities adapted to mesic and hydric conditions. In these cases, mechanical cutting should be replaced by a one-time stump-killing operation, to avoid repeated and unsuccessful treatments of the same individuals over time. 相似文献
835.
For the last 20 years, human–wildlife conflicts have been rapidly increasing in towns. Although people want “greener” cities,
the expansion of disliked species causes problems that are difficult to manage and to reduce. The complexity of the numerous
factors involved in these human–wildlife relations needs the development of a comprehensive tool for urban planners. Today,
with the development of computers and geographical information systems, it is easier to analyze and combine different spatial
data as methods used for the management of risks in studies of natural hazards. Here we present a method for assessing and
mapping the risk in cases of human–wildlife conflict. An application to starling management in a town in western France will
show the efficiency of our methods to combine information given by a network of experts and to highlight higher risk sites.
The map of risk provides a spatial result useful for comprehension, communication between people and agencies, and public
education. 相似文献
836.
Sakai Y Shoji R Kim BS Sakoda A Suzuki M 《Environmental monitoring and assessment》2001,70(1-2):57-70
Among bioassays for evaluating various impacts of chemicalson humans and ecosystems, those based on culturedmammalian-cells can best predict acute lethal toxicity to humans. Weexpect them to be employed in the future in environmentalrisk management alongside mutagenicity tests and endocrine-disrupting activity tests. We recently developed adisposable bioassay device that immobilizes humanhepatocarcinoma cells in a small micropipette tip. Thisenables very quick (within 2 h) evaluation of acute lethaltoxicity to humans. For bioassay-based environmentalmanagement, 2 promising approaches have been demonstrated bythe US-EPA: toxicity identification evaluation (TIE) andtoxicity reduction evaluation (TRE). The Japanese Ministryof Environment has been supporting a multi-center validationproject, aimed at assembling a bioassay database. To makefull use of these resources, we present a numerical modelthat describes contribution of individual chemical toobserved toxicity. This will allow the selection of the mosteffective countermeasure to reduce the toxicity. Bioassay-based environmental risk management works retrospectively,whereas impact assessment using substance flow models andtoxicity databases works prospective. We expect that these 2approaches will exchange information, act complementarily,and work effectively in keeping our environment healthy inthe 21st century. 相似文献
837.
Fire occurrences and their sources were monitored in Emas National Park, Brazil (17°49′–18°28′S; 52°39′–53°10′W) from June
1995 to May 1999. The extent of burned area and weather conditions were registered. Forty-five fires were recorded and mapped
on a GIS during this study. Four fires occurred in the dry winter season (June–August; 7,942 ha burned), all caused by humans;
10 fires occurred in the seasonally transitional months (May and September) (33,386 ha burned); 31 fires occurred in the wet
season, of which 30 were caused by lightning inside the park (29,326 ha burned), and one started outside the park (866 ha
burned). Wet season lightning fires started in the open vegetation (wet field or grassy savanna) at a flat plateau, an area
that showed significantly higher fire incidence. On average, winter fires burned larger areas and spread more quickly, compared
to lightning fires, and fire suppression was necessary to extinguish them. Most lightning fires were patchy and extinguished
primarily by rain. Lightning fires in the wet season, previously considered unimportant episodes, were shown to be very frequent
and probably represent the natural fire pattern in the region. Lightning fires should be regarded as ecologically beneficial,
as they create natural barriers to the spread of winter fires. The present fire management in the park is based on the burning
of preventive firebreaks in the dry season and exclusion of any other fire. This policy does not take advantage of the beneficial
effects of the natural fire regime and may in fact reduce biodiversity. The results presented here stress the need for reevaluating
present policies and management procedures concerning fire in cerrado conservation areas. 相似文献
838.
/ Surveys focusing on solid-waste-related issues, conducted over a period of several years, provided data from independent samples of residents of a Midwestern, USA, community. The collection of these data yielded useful information about the relationship between residents' recycling motives and their attitudes toward solid waste management in light of several changes in the solid waste infrastructure of the community over that time. The initial survey assessed baseline beliefs and attitudes, while later surveys were conducted after the implementation of a community educational program and a curbside recycling program. The findings indicated that for recyclers and nonrecyclers, different motives predicted endorsement of solid waste programs and policies. Although a similar percentage of recyclers and nonrecyclers were in support of various proposed programs and policies, concern for the environment was found to be positively related to nonrecyclers' support of proposed programs, particularly before these programs were implemented. Prior to program implementation, motives other than environmental altruism were found to be related to recyclers' support of the programs. Additional findings support the idea that educational programs and increased accessibility to recycling opportunities affect the relationship between people's attitudes toward solid waste management and their recycling motives. 相似文献
839.
/ Environmental regulatory agencies are responsible for protecting human health and the environment in their constituencies. Their responsibilities include the identification, evaluation, and cleanup of contaminated sites. Leaking underground storage tanks (USTs) constitute a major source of subsurface and groundwater contamination. A significant portion of a regulatory body's efforts may be directed toward the management of UST-contaminated sites. In order to manage remedial sites effectively, vast quantities of information must be maintained, including analytical dataon chemical contaminants, remedial design features, and performance details. Currently, most regulatory agencies maintain such information manually. This makes it difficult to manage the data effectively. Some agencies have introduced automated record-keeping systems. However, the ad hoc approach in these endeavors makes it difficult to efficiently analyze, disseminate, and utilize the data. This paper identifies the information requirements for UST-contaminated site management at the Waste Cleanup Section of the Department of Environmental Resources Management in Dade County, Florida. It presents a viable design for an information management system to meet these requirements. The proposed solution is based on a back-end relational database management system with relevant tools for sophisticated data analysis and data mining. The database is designed with all tables in the third normal form to ensure data integrity, flexible access, and efficient query processing. In addition to all standard reports required by the agency, the system provides answers to ad hoc queries that are typically difficult to answer under the existing system. The database also serves as a repository of information for a decision support system to aid engineering design and risk analysis. The system may be integrated with a geographic information system for effective presentation and dissemination of spatial data. 相似文献
840.
This paper describes an application of multiple criteria analysis (MCA) in assessing criteria and indicators adapted for a
particular forest management unit. The methods include: ranking, rating, and pairwise comparisons. These methods were used
in a participatory decision-making environment where a team representing various stakeholders and professionals used their
expert opinions and judgements in assessing different criteria and indicators (C&I) on the one hand, and how suitable and
applicable they are to a forest management unit on the other. A forest concession located in Kalimantan, Indonesia, was used
as the site for the case study. Results from the study show that the multicriteria methods are effective tools that can be
used as structured decision aids to evaluate, prioritize, and select sets of C&I for a particular forest management unit.
Ranking and rating approaches can be used as a screening tool to develop an initial list of C&I. Pairwise comparison, on the
other hand, can be used as a finer filter to further reduce the list. In addition to using these three MCA methods, the study
also examines two commonly used group decision-making techniques, the Delphi method and the nominal group technique. Feedback
received from the participants indicates that the methods are transparent, easy to implement, and provide a convenient environment
for participatory decision-making. 相似文献