全文获取类型
收费全文 | 2280篇 |
免费 | 355篇 |
国内免费 | 1287篇 |
专业分类
安全科学 | 287篇 |
废物处理 | 18篇 |
环保管理 | 185篇 |
综合类 | 2403篇 |
基础理论 | 332篇 |
污染及防治 | 186篇 |
评价与监测 | 236篇 |
社会与环境 | 146篇 |
灾害及防治 | 129篇 |
出版年
2024年 | 41篇 |
2023年 | 134篇 |
2022年 | 227篇 |
2021年 | 260篇 |
2020年 | 255篇 |
2019年 | 193篇 |
2018年 | 176篇 |
2017年 | 173篇 |
2016年 | 191篇 |
2015年 | 219篇 |
2014年 | 189篇 |
2013年 | 207篇 |
2012年 | 263篇 |
2011年 | 219篇 |
2010年 | 165篇 |
2009年 | 142篇 |
2008年 | 90篇 |
2007年 | 134篇 |
2006年 | 123篇 |
2005年 | 99篇 |
2004年 | 75篇 |
2003年 | 69篇 |
2002年 | 56篇 |
2001年 | 40篇 |
2000年 | 37篇 |
1999年 | 17篇 |
1998年 | 25篇 |
1997年 | 17篇 |
1996年 | 18篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有3922条查询结果,搜索用时 15 毫秒
991.
Recent attention has focused on resource management initiatives at the watershed scale with emphasis on collaborative, locally driven, and decentralized institutional arrangements. Existing literature on limited selections of well-established watershed-based organizations has provided valuable insights. The current research extends this focus by including a broad survey of watershed organizations from across the United States as a means to estimate a national portrait. Organizational characteristics include year of formation, membership size and composition, budget, guiding principles, and mechanisms of decision-making. These characteristics and the issue concerns of organizations are expected to vary with respect to location. Because this research focuses on organizations that are place based and stakeholder driven, the forces driving them are expected to differ across regions of the country. On this basis of location, we suggest basic elements for a regional assessment of watershed organizations to channel future research and to better approximate the organizational dynamics, issue concerns, and information needs unique to organizations across the country. At the broadest level, the identification of regional patterns or organizational similarities may facilitate the linkage among organizations to coordinate their actions at the much broader river basin or ecosystem scale. 相似文献
992.
993.
The Ecological and Environmental Characteristics and Conservation of the Wetlands in the Changjiang Estuary, China 总被引:2,自引:0,他引:2
The natural wetlands in the Changjiang Estuary, China are important ecologically. The total area of the wetlands in the Changjiang Estuary amounts to 215000 ha. The wetlands consist of littoral and sandy estuarine island areas, and are rich in biological resources. There are 136 species of vascular plant, 150 species of bird, and 68 species of benthic macro-invertebrate in the wetlands. However, the wetland in the Changjiang Estuary is a vulnerable ecosystem. Development of the wetland is mainly influenced by intensive human reclamation, pollution, movement of sediments in the Changjiang River, and the effects of tides and waves. Investigations have shown that maintaining biodiversity, providing resources for the living organisms, purifying environments and resisting natural hazards could be regarded as important functions for the protection of the wetlands. It is proposed that sustainable principles should be supported in developing the wetlands in the future. 相似文献
994.
关于中国塔里木河流域若干问题的辨识 总被引:4,自引:0,他引:4
塔里木河流域的水量及水质变化 ,生态环境质量的优劣 ,生态需水量的估算、整治目标的确定等问题 ,一直是该流域资源环境和社会经济的核心问题。对其近 40年来水文观测资料的时间序列进行分析 ,三源流区的水资源量逐年递增 2× 1 0 7m3,但干流上游阿拉尔来水量每年递减 3× 1 0 7m3。水质的劣变特征亦较明显。通过构建生态脆弱性指数 ,定量评价流域生态环境质量表明 ,干流下游已属于生态环境严重受损区。用潜水蒸发和定额法的原理估算植被耗水 ,提出了维护干流区生态环境在不同目标年的生态需水量。认为应当在水资源承载力和环境容量的阈限内 ,合理确定科学的保护方案 相似文献
995.
996.
文章通过对青海野生大黄的生态环境、分布状况、群落特征、开发现状、存在问题的分析和论述,提出未来青海野生大黄资源开发必须遵从生态保护为先,生态、生产、经济、社会效益共同持续的原则,强化资源保护和基础技术研究,加大人工驯化裁培力度,不断满足日益增长的市场需求。 相似文献
997.
Pollution characteristics of the recent sediments in the Hangzhou section of the Grand Canal, China 总被引:4,自引:0,他引:4
Spatial distribution of heavy metals, arsenic and organic matter in recent sediments in the Hangzhou section of the Grand Canal and their relationships were analyzed. The results showed that the concentrations of heavy metals and organic matters varied widely along the canal, and the average geological accumulation factors decreased in the following orders: organic carbon(2.6), zinc(2.1 ), cadmium(2.0), copper( 1.5), lead(1.1), nitrogen(0.9), mercury (0.8), phosphorus(0.4), arsenic(0.2) and chromium(0). Content of heavy metals and organic carbon in the top 10 cm layer were lower than that of lower layers, except for mercury and organic carbon in the S9 section. Contents of organic carbon in the top 50 cm layer of the mud sediments are significantly higher than those undemeath. In the bottom mud layer, there is a concentration peak of the pollutants. In the mud sediments of the canal, cadmium mainly occurred in the Fe and Mn oxide fraction, copper in the organic fraction, lead in the Fe and Mn oxide fraction, and zinc in the carbonate and the Fe and Mn oxide fraction. 相似文献
998.
Questionnaire surveys and subjective evaluations on residential environment were performed in order to grasp the main factors of residential environment of small local cities. The suitable evaluation index system was established, and the regional residential environment characteristics and personal residential preference types were analyzed, so that their influence on residential environment evaluation could be grasped. The results can be applied to the residential environment planning, construction and monitoring of local cities. 相似文献
999.
Aerobic heterotrophic granular sludge was cultivated in a sequencing batch shaking reactor(SBSR) in which a synthetic wastewater containing glucose as carbon source was fed. The characteristics of the aerobic granules were investigated. Compared with the conventional activated sludge flocs, the aerobic granules exhibit excellent physical characteristics in terms of settleability, size, shape, biomass density, and physical strength.Scanning electron micrographs revealed that in mature granules little filamentous bacteria could be found, rod-shaded and coccoid bacteria were the dominant microorqanisms. 相似文献
1000.