全文获取类型
收费全文 | 2273篇 |
免费 | 174篇 |
国内免费 | 63篇 |
专业分类
安全科学 | 132篇 |
废物处理 | 17篇 |
环保管理 | 1045篇 |
综合类 | 609篇 |
基础理论 | 369篇 |
环境理论 | 2篇 |
污染及防治 | 51篇 |
评价与监测 | 60篇 |
社会与环境 | 129篇 |
灾害及防治 | 96篇 |
出版年
2023年 | 26篇 |
2022年 | 51篇 |
2021年 | 49篇 |
2020年 | 52篇 |
2019年 | 51篇 |
2018年 | 60篇 |
2017年 | 85篇 |
2016年 | 94篇 |
2015年 | 93篇 |
2014年 | 80篇 |
2013年 | 122篇 |
2012年 | 83篇 |
2011年 | 131篇 |
2010年 | 91篇 |
2009年 | 107篇 |
2008年 | 100篇 |
2007年 | 113篇 |
2006年 | 109篇 |
2005年 | 84篇 |
2004年 | 71篇 |
2003年 | 76篇 |
2002年 | 54篇 |
2001年 | 59篇 |
2000年 | 54篇 |
1999年 | 68篇 |
1998年 | 42篇 |
1997年 | 39篇 |
1996年 | 42篇 |
1995年 | 40篇 |
1994年 | 27篇 |
1993年 | 17篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 14篇 |
1975年 | 10篇 |
1973年 | 16篇 |
1972年 | 14篇 |
1971年 | 16篇 |
排序方式: 共有2510条查询结果,搜索用时 15 毫秒
911.
V. F. van Katwijk A. Rango A. E. Childress 《Journal of the American Water Resources Association》1993,29(5):755-766
ABSTRACT: The projected increase in the concentration of CO2 and other greenhouse gases in the atmosphere is likely to result in a global temperature increase. This paper reports on the probable effects of a temperature increase and changes in transpiration on basin discharge in two different mountain snowmelt regions of the western United States. The hydrological effects of the climate changes are modeled with a relatively simple conceptual, semi-distributed snowmelt runoff model. Based on the model results, it may be concluded that increased air temperatures will result in a shift of snowmelt runoff to earlier in the snowmelt season. Furthermore, it is shown that it is very important to include the expected change in climate-related basin conditions resulting from the modeled temperature increase in the runoff simulation. The effect of adapting the model parameters to reflect the changed basin conditions resulted in a further shift of streamflow to April and an even more significant decrease of snowmelt runoff in June and July. If the air temperatures increase by approximately 5°C and precipitation and accumulated snow amounts remain about the same, runoff in April and May, averaged for the two basins, is expected to increase by 185 percent and 26 percent, respectively. The runoff in June and July will decrease by about 60 percent each month. Overall, the total seasonal runoff decreases by about 6 percent. If increased CO2 concentrations further change basin conditions by reducing transpiration by the maximum amounts reported in the literature, then, combined with the 5°C temperature increase, the April, May, June, and July changes would average +230 percent, +40 percent, ?55 percent, and ?45 percent, respectively. The total seasonal runoff change would be +11 percent. 相似文献
912.
在界定旅游概念规划的基础上,对其内容体系进行了研究,创新性地提出了一种新的旅游概念规划内容体系,即它由背景环境解析、理念融合创新、目标定位、发展战略确定、关键策略选择五大板块组成,内容涉及到发展背景认知、区域特征分析、特殊理念识别、特有思想梳理、关键概念提取、规划目标界定、发展战略选择、主题形象提升、空间构架部署、概念分区支撑、意象设计解码、发展模式生成、旅游策略选择等13个方面,并以《重庆市千亩荷园旅游概念规划》为例,在理论和实证双重层面上证实了这套新内容体系的实践价值和存在意义. 相似文献
913.
914.
白云湖湿地生态功能区规划及保障措施 总被引:1,自引:0,他引:1
在实地调查的基础上,根据资源经济学、生态经济学的理论和方法,针对白云湖湿地资源的主要功能特点,对其各个区域的生态服务功能价值--直接利用价值和间接利用价值进行了货币化评估,由此进行湿地功能区域划分,并对各个区域进行了现状分析,从而得出最优目标,以期达到在保护好湿地生态环境的基础上进行资源的合理开发,实现湖区湿地资源的可持续利用,保证湖区经济和社会的可持续发展. 相似文献
915.
刘会建 《中国环境管理干部学院学报》2012,(5):14-16
环境监测站质量管理体系内部审核是监测站自我发现问题、分析问题、解决问题,实现质量管理体系持续改进的重要环节。通过总结当前环境监测站内审时在审核策划、实施审核、结果评价及跟踪验证等4个阶段的注意事项,提出了全面细致策划、严格实施审核、客观公正评价、深入实地验证等提高内部审核质量的对策和建议。 相似文献
916.
I. G. Mason A. K. Brooking A. Oberender J. M. Harford P. G. Horsley 《Resources, Conservation and Recycling》2003,38(4):257-269
A zero waste program was established at a university campus in response to grassroots student concern over environmental management issues. The implementation procedure consisted of initial discussions with academic and local authority staff at a university environmental forum, the formation of a working group, the preparation of a funding proposal and the establishment of an externally funded research, educational and promotional program led by an academic staff member. Support from senior management existed in the form of a written environmental policy and a signed commitment to environmental responsibility in tertiary education and university funding support followed the success of the initial funding application. Projects were typically conducted by paid research associates, assisted by student volunteers and supervised by a program leader from the academic staff. Co-operation and support from facilities management staff was obtained on an informal basis. A campus environmental committee was established in order to facilitate communication on environmental matters between the School for the Environment, senior university management, facilities management staff, academic staff and students. In order to enable full program development however, a need for linkages between all sectors involved in the program and the introduction of a formal environmental management system was identified. 相似文献
917.
城镇建设用地需求预测与配置研究 总被引:11,自引:0,他引:11
针对我国现行城镇建设用地预测方法存在的问题,对城镇建设用地预测方法进行了探索性研究;通过构建科学的建设用地需求预测方法,为土地利用规划提供科学依据。在C—D生产函数的基础上,提出了土地、资本与产出GDP的要素关系模型、恩格尔系数与人均建设用地面积关系模型和时间序列的ARIMA建设用地模型。对成都市城镇建设用地总量进行了实证分析,对4种预测方法的结果进行了定量评价,并据此提出成都市建设用地的配置方案。 相似文献
918.
Linking linear programming and spatial simulation models to predict landscape effects of forest management alternatives 总被引:1,自引:0,他引:1
Forest management planners require analytical tools to assess the effects of alternative strategies on the sometimes disparate benefits from forests such as timber production and wildlife habitat. We assessed the spatial patterns of alternative management strategies by linking two models that were developed for different purposes. We used a linear programming model (Spectrum) to optimize timber harvest schedules, then a simulation model (HARVEST) to project those schedules in a spatially explicit way and produce maps from which the spatial pattern of habitat could be calculated. We demonstrated the power of this approach by evaluating alternative plans developed for a national forest plan revision in Wisconsin, USA. The amount of forest interior habitat was inversely related to the amount of timber cut, and increased under the alternatives compared to the current plan. The amount of edge habitat was positively related to the amount of timber cut, and increased under all alternatives. The amount of mature northern hardwood interior and edge habitat increased for all alternatives, but mature pine habitat area varied. Mature age classes of all forest types increased, and young classes decreased under all alternatives. The average size of patches (defined by age class) generally decreased. These results are consistent with the design goals of each of the alternatives, but reveal that the spatial differences among the alternatives are modest. These complementary models are valuable for quantifying and comparing the spatial effects of alternative management strategies. 相似文献
919.
Barbara A. Smolko Roy R. Huberd Nancy Tam‐Davis 《Journal of the American Water Resources Association》2002,38(4):981-994
ABSTRACT: Since 1989, the government of Pierce County, Washington, has prepared four watershed action plans. The watersheds cover almost 800,000 acres and include about 600,000 residents and diverse land uses, from the city of Tacoma to Mount Rainier National Park. The primary purpose of these plans was to address water quality impacts from nonpoint sources of pollution and to protect beneficial uses of water. Pierce County has experienced problems such as shellfish bed closures and the Federal Clean Water Act Section 303(d) listing of local water bodies as a result of declining water quality. Pierce County achieved improvements by engaging diverse groups of stakeholders in generating solutions to nonpoint sources of water pollution through our watershed planning process. Using participatory methods borrowed from private industry, Pierce County was able to reach consensus, build trust, maximize participation, facilitate learning, encourage creativity, develop partnerships, shorten time frames for the planning processes, and increase the level of commitment participants had to implementing the plans. As a result, the earliest plans have a high rate of voluntary implementation. This indicates that the process and methodology used to develop watershed plans has a significant, if not critical, impact on their success. 相似文献
920.
Scott A. Sheeder Jeremy D. Ross Toby N. Carlson 《Journal of the American Water Resources Association》2002,38(4):1027-1040
ABSTRACT: Many studies can be found in the literature pertaining to the effects of urbanization on surface runoff in small watersheds and the hydrologic response of undeveloped watersheds. However, an extensive literature review yielded few published studies that illustrate differing hydrologic responses from multiple source areas within a watershed. The concepts discussed here are not new, but the methods used provide a unique, basic procedure for investigating stormwater hydrology in topographically diverse basins. Six storm hydrographs from three small central Pennsylvania watersheds were analyzed for this paper; five are presented. Two important conclusions are deduced from this investigation. First, in all cases we found two distinct peaks in stream discharge, each representing different contributing areas to direct discharge with greatly differing curve numbers and lags representative of urban and rural source regions. Second, the direct discharge represents only a small fraction of the total drainage area with the urban peak becoming increasingly important with respect to the rural peak with the amount of urbanization and as the magnitude of the rain event decreases. 相似文献