全文获取类型
收费全文 | 29732篇 |
免费 | 335篇 |
国内免费 | 247篇 |
专业分类
安全科学 | 999篇 |
废物处理 | 1453篇 |
环保管理 | 3941篇 |
综合类 | 4469篇 |
基础理论 | 7748篇 |
环境理论 | 8篇 |
污染及防治 | 7348篇 |
评价与监测 | 2125篇 |
社会与环境 | 2043篇 |
灾害及防治 | 180篇 |
出版年
2023年 | 140篇 |
2022年 | 261篇 |
2021年 | 319篇 |
2020年 | 195篇 |
2019年 | 243篇 |
2018年 | 435篇 |
2017年 | 460篇 |
2016年 | 719篇 |
2015年 | 531篇 |
2014年 | 854篇 |
2013年 | 2463篇 |
2012年 | 1015篇 |
2011年 | 1349篇 |
2010年 | 1102篇 |
2009年 | 1144篇 |
2008年 | 1410篇 |
2007年 | 1329篇 |
2006年 | 1207篇 |
2005年 | 1079篇 |
2004年 | 1037篇 |
2003年 | 990篇 |
2002年 | 933篇 |
2001年 | 1091篇 |
2000年 | 768篇 |
1999年 | 482篇 |
1998年 | 363篇 |
1997年 | 383篇 |
1996年 | 397篇 |
1995年 | 465篇 |
1994年 | 394篇 |
1993年 | 343篇 |
1992年 | 376篇 |
1991年 | 355篇 |
1990年 | 326篇 |
1989年 | 322篇 |
1988年 | 295篇 |
1987年 | 241篇 |
1986年 | 247篇 |
1985年 | 247篇 |
1984年 | 267篇 |
1983年 | 254篇 |
1982年 | 268篇 |
1981年 | 221篇 |
1980年 | 165篇 |
1979年 | 181篇 |
1978年 | 162篇 |
1977年 | 133篇 |
1975年 | 137篇 |
1973年 | 167篇 |
1972年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
321.
MICHAEL A. SCHUETT 《Environmental management》1997,21(2):239-246
/ This study intended to explore the perceptions of mountain bikingmanagement through a mail survey of state park directors in all 50 states.With a 100% response rate, it was found that 47 states permit mountainbiking in their state parks, however, few state parks have formalized plansto manage this outdoor activity. The management policies that do exist arenot followed on a statewide basis but vary within each state and at eachstate park. Many states have worked cooperatively with local mountain bikingclubs to develop and maintain mountain bike trails, promote rider education,and provide volunteer patrols on trails. The issue of user conflict surfacedwith almost three-fourths of the managers responding that conflict existedbetween mountain bikers and other trail users. This preliminary study shouldprompt further research with on-site managers focusing on the use ofmanagement plans for mountain biking, cooperation between managers and usergroups, and user conflict. It is recommended that an Internet-basedinformation clearinghouse or discussion group be made available to landmanagers by a national bicycling organization.KEY WORDS: Mountain biking; State parks; State park directors;Recreation resource management 相似文献
322.
RONALD R. SCHNABEL JOHN A. SHAFFER WILLIAM L. STOUT LEONARD F. CORNISH 《Environmental management》1997,21(2):283-290
/ Denitrification in riparian ecosystems can reduce the amount ofnitrogen transported from farm fields to streams. In this study, we examinedenitrification in four riparian ecosystems common to the Valley and Ridgephysiographic province in Pennsylvania, USA. The sites exhibit differentvegetation, are underlain by different rock types, and are downgradient offarm fields. Mean site denitrification rates ranging from 0.6 to 1.9 &mgr;gN/kg soil/day were measured using intact core incubation techniques. Thethree riparian sites covered with grass each exhibited greaterdenitrification rates than the wooded site. Denitrification rate wascorrelated with moisture content but not with nitrate-N or organic carboncontents. Denitrification rates were greatest near the soil surface and atpositions nearest the stream. Rates decreased uniformly with distance awayfrom the stream and also with depth in the soil for each site. While patternsof nitrate-N, moisture, and organic carbon content differ among the sites,their combined effects on denitrification support the observed, consistentdenitrification rate pattern.KEY WORDS: Denitrification; Riparian ecosystems 相似文献
323.
WILLIAM E. HOGSETT JAMES E. WEBER DAVID TINGEY ANDREW HERSTROM E. HENRY LEE JOHN A. LAURENCE 《Environmental management》1997,21(1):105-120
/ The risk tropospheric ozone poses to forests in the United States is dependent on the variation in ozone exposure across the distribution of the forests in question and the various environmental and climate factors predominant in the region. All these factors have a spatial nature, and consequently an approach to characterization of ozone risk is presented that places ozone exposure-response functions for species as seedlings and model-simulated tree and stand responses in a spatial context using a geographical information systems (GIS). The GIS is used to aggregate factors considered important in a risk characterization, including: (1) estimated ozone exposures over forested regions, (2) measures of ozone effects on species' and stand growth, and (3) spatially distributed environmental, genetic, and exposure influences on species' response to ozone. The GIS-based risk characterization provides an estimation of the extent and magnitude of the potential ozone impact on forests. A preliminary risk characterization demonstrating this approach considered only the eastern United States and only the limited empirical data quantifying the effect of ozone exposures on forest tree species as seedlings. The area-weighted response of the annual seedling biomass loss formed the basis for a sensitivity ranking: sensitive-aspen and black cherry (14%-33% biomass loss over 50% of their distribution); moderately sensitive-tulip popular, loblolly pine, eastern white pine, and sugar maple (5%-13% biomass loss); insensitive-Virginia pine and red maple (0%-1% loss). In the future, the GIS-based risk characterization will include process-based model simulations of the three- to 5-year growth response of individual species as large trees with relevant environmental interactions and model simulated response of mixed stands. The interactive nature of GIS provides a tool to explore consequences of the range of climate conditions across a species' distribution, forest management practices, changing ozone precursors, regulatory control strategies, and other factors influencing the spatial distribution of ozone over time as more information becomes available.KEY WORDS: Ecological risk assessment; GIS; Ozone; Risk characterization; Forests; Trees 相似文献
324.
Integration of Environmental Assessment into the Regional Development Planning Process of the Galilee 总被引:2,自引:0,他引:2
/ The Galilee region on the northern edge of Israel constitutes more than 15% of the state's territory, supplies more than half of its drinking water needs, and is an important recreational resource and destination for Israelis. One of the main objectives of the plan for the Galilee was to devise a regional physical and economic development strategy for the years 1992-2007 that would arrest the trend of emigration of its residents, attract newly arrived immigrants to the region, and at the same time protect natural resources and environmental quality. This paper is limited to discussion of the environmental aspects of the plan. It analyzes spatial concepts for distribution of projected population growth, evaluates environmental impacts of alternative plans, and proposes a decision-making framework and tools for minimizing natural resources loss from development at the local level. Assessment of potential environmental impacts generated quantitative data of natural resources areas. Application of the data in the plan evaluation stage showed that the alternative that concentrated most of the new development in central Galilee was the second-best choice environmentally, but was preferred as the best choice for overall qualities. The planning study offers an alternative environmental impact assessment (EIA) process to the one presently used in Israel by incorporating environmental considerations at the initial plan-making stage and not at the plan-approval stage. It demonstrated that in order to be effective, environmental assessment and land-use planning should be seen as one effort that is integrated from the start and in each stage of the plan-making process.KEY WORDS: Environmental assessment; Development planning; Galilee 相似文献
325.
326.
J. V. Bonta C. R. Amerman T. J. Harlukowicz W. A. Dick 《Journal of the American Water Resources Association》1997,33(4):907-917
ABSTRACT: A study was conducted to determine the effects of mining and reclaiming originally undisturbed watersheds on surface-water hydrology in three small experimental watersheds in Ohio. Approximately six years of data were collected at each site, with differing lengths of premining (Phase 1), mining and reclamation (Phase 2), and post-reclamation (Phase 3) periods. Mining and reclamation activities showed no consistent pattern iii base-flow, and caused slightly more frequent higher daily flow volumes. Phase 2 activities can cause reductions in seasonal variation in double mass curves compared with Phase 1. Restoration of seasonal variations was noticeably apparent at one site during Phase 3. The responses of the watersheds to rainfall intensities causing larger peak flow rates generally decreased due to mining and reclamation, but tended to exceed responses observed in Phase 1 during Phase 3. Natural Resources Conservation Service (NRCS) curve numbers increased due to mining and reclamation (Phase 2), ranging from 83 to 91. During Phase 3, curve numbers remained approximately constant from Phase 2, ranging from 87 to 91. 相似文献
327.
Until now no structured methodology existed for attuning environmental considerations to the business strategy of companies. The Environmental Competence Centre of Philips Sound & Vision in The Netherlands has developed and tested a methodology for this purpose. This methodology, called Selection of STRrategic Environmen Tal CHallenges (STRETCH), has proven to lead to promising results and should therefore be actively promoted. In this article, the authors show how the application of STRETCH provides the possibility of meeting three main objectives: First, focusing on the incorporation of environmental aspects into the company's business strategy can elicit innovations that may enhance the competitive position of the company by cost reduction and/or higher market shares. Second, the environmental opportunities and threats to be expected in the future can be anticipated in an earlier phase. Through this proactive approach a company can avoid external criticism and take the lead in environmental priority setting. Third, by applying the STRETCH methodology even higher eco-efficiencies are expected to be reached than through incremental, step-by-step environmental improvements. 相似文献
328.
329.
Christopher A. Janicak 《Journal of Safety Research》1996,27(4):233-239
This study examined employers′ perceived knowledge of the Hazard Communication Standard (HCS) requirements prior to the inspection in which they were cited for an HCS violation. A lack of staff available to implement the HCS program was identified as having a significant impact upon compliance (p < 01). The perceived difficulty with compliance was also examined by the violations received by the organization. Those organizations cited for failing to have a written program identified a lack of staff available to implement the HCS requirements as having a greater impact upon compliance than those not cited for written program violations (p < 05). Suggested methods for improving the overall compliance with the HCS may include using the many compliance resources available through insurance companies, safety organizations, and state programs. Areas for further research include identifying the availability, use, and effectiveness of the outside safety and health compliance resources. 相似文献
330.
More than 1500 manufactured gas plant (MGP) sites exist throughout the U.S. Many are contaminated with coal tar from coal-fueled gas works which produced ‘town gas’ from the mid-1800s through the 1950s.1,2 Virtually all old U.S. cities have such sites. Most are in downtown areas as they were installed for central distribution of manufactured gas. While a few sites are CERCLA/Superfund, most are not. However, the contaminants and methods used for remediation are similar to those used for Superfund clean-ups of coal tar contamination from wood-treating and coke oven facilities. Clean-up of sites is triggered by regulatory pressure, property transfers and re-development as well as releases to the environment — in particular, via groundwater migration. Due to utility de-regulation, site clean-ups may also be triggered by sale of a utility or of a specific utility site to other utilities. Utilities have used two approaches in dealing with their MGP sites. The first is ‘do nothing and hope for the best’. History suggests that, sooner or later, these sites become a bigger problem via a release, citizen lawsuit or regulatory/public service commission intervention. The second, far better approach is to define the problem now and make plans for waste treatment or immobilization. This paper describes recent experience with a high capacity/low cost thermal desorption process for this waste and reviews non-thermal technology, such as bio-treatment, capping, recycling, and dig and haul. Cost data is provided for all technologies, and a case study for thermal treatment is also presented. 相似文献