全文获取类型
收费全文 | 3558篇 |
免费 | 125篇 |
国内免费 | 185篇 |
专业分类
安全科学 | 116篇 |
废物处理 | 34篇 |
环保管理 | 1235篇 |
综合类 | 1270篇 |
基础理论 | 409篇 |
环境理论 | 2篇 |
污染及防治 | 107篇 |
评价与监测 | 84篇 |
社会与环境 | 570篇 |
灾害及防治 | 41篇 |
出版年
2023年 | 21篇 |
2022年 | 52篇 |
2021年 | 56篇 |
2020年 | 69篇 |
2019年 | 56篇 |
2018年 | 63篇 |
2017年 | 102篇 |
2016年 | 106篇 |
2015年 | 87篇 |
2014年 | 98篇 |
2013年 | 197篇 |
2012年 | 149篇 |
2011年 | 201篇 |
2010年 | 141篇 |
2009年 | 123篇 |
2008年 | 130篇 |
2007年 | 192篇 |
2006年 | 158篇 |
2005年 | 182篇 |
2004年 | 181篇 |
2003年 | 170篇 |
2002年 | 145篇 |
2001年 | 116篇 |
2000年 | 146篇 |
1999年 | 149篇 |
1998年 | 91篇 |
1997年 | 82篇 |
1996年 | 65篇 |
1995年 | 78篇 |
1994年 | 59篇 |
1993年 | 56篇 |
1992年 | 54篇 |
1991年 | 39篇 |
1990年 | 26篇 |
1989年 | 13篇 |
1988年 | 24篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1983年 | 8篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 12篇 |
1972年 | 11篇 |
1971年 | 17篇 |
排序方式: 共有3868条查询结果,搜索用时 953 毫秒
331.
长江流域的鱼类资源及其保护对策 总被引:40,自引:7,他引:33
刘健康|曹文宣 《长江流域资源与环境》1992,1(1):3-23
长江水系的鱼类约有300种,其中鲤科鱼类占半数以上,主要的经济鱼类多数属于鲤科。对不同江段的鱼类资源作了简介,并提出了相应的保护措施。上游江段以维护生物多样性,保护特有种为主,需要建立鱼类自然保护区;中游应保证主要经济鱼类的自然繁殖条件,加强珍稀鱼类的人工繁殖放流工作,同时对湖泊幼鱼资源进行保护;下游应注意保持江水质量,严格遵守工业废水排放标准;河口江段应规定幼鲟保护期,建议每年6月15日至7月31日停止一切损害幼鲟资源的渔捞作业。 相似文献
332.
关于中国土地资源人口承载力问题的思考 总被引:4,自引:0,他引:4
朱国宏 《中国人口.资源与环境》1996,6(1):18-22
土地资源的人口承载力问题也就是生存空间问题,它关系到人类未来的生存与发展问题,历来受学术界的注目。20世纪70年代联合国粮农组织(FAO)曾主持了一项大型的发展中地区土地资源人口承载力问题的研究,80年代后期,中国科学院—国家计委自然资源综合考察委员会也主持了一项大型的中国土地资源生产能力及人口承载量研究。相应地还有一系列有关中国未来的生存与发展和人口承载力问题的探讨。本文从中国人地关系变化的角度介入这一讨论,分析中国远期的土地资源是否超载的问题。 相似文献
333.
我国矿产资源利用的环境问题及对策 总被引:4,自引:0,他引:4
徐强 《中国人口.资源与环境》1995,5(1):33-37
矿产资源利用过程中靠成的环境问题是我国经济建设速发展所面临的一个现实问题本文全面地分析了矿产资源利用对环境影响的各个方面,分析了我国矿产资源环境问题的一些特点,提出了八个方面的对策建议。 相似文献
334.
335.
Atsushi?TerazonoEmail author Aya?Yoshida Jianxin?Yang Yuichi?Moriguchi Shin-ichi?Sakai 《Journal of Material Cycles and Waste Management》2004,6(2):82-96
In this article, we clarify the current status of Japanese exports and Chinese imports of secondary resources. A total of around 10 million metric tons (t) of secondary resources are exported annually from Japan to China, Hong Kong, and Korea. Hong Kong plays the role of a transshipment point, especially regarding the trade in plastic waste, and China imports much from the USA and Japan, often through Hong Kong. The secondary resources exported from Japan include both byproducts from manufacturing processes and end-of-life products or materials. The great demand in China, and the difference in prices between countries, drive this transboundary shipment, although Japan has enacted various recycling laws that were implicitly intended to promote domestic recycling. In China, the imported secondary resources are recycled, usually by means of primitive and low-cost hand labor. The greatest concern is whether there are still improper (illegal or polluting) recycling activities in China. International material cycles should prevent environmental pollution and ensure efficient resource utilization. To that end, the following measures are needed: cooperative control of the trade of secondary resources between countries, the alignment of domestic laws with the regulations in other countries based on the actual trade activities, and the realization of sound practices for global resources management. 相似文献
336.
Environmental implications of changes in the levels of lakes in the Ethiopian Rift since 1970 总被引:1,自引:0,他引:1
The Ethiopian rift is characterized by a chain of lakes of various sizes and hydrological and hydrogeological settings. The rift lakes and feeder rivers are used for irrigation, soda extraction, commercial fish farming, and recreation, and they support a wide variety of endemic birds and wild animals. The levels of some of these lakes have changed dramatically over the last three decades. Lakes that are relatively uninfluenced by human activities (Langano and Abaya) remain stable except for the usual inter-annual variations, strongly influenced by rainfall. Some lakes have shrunk due to excessive abstraction of water; others have expanded due to increases in surface runoff and groundwater flux from percolated irrigation water. Lakes Abiyata and Beseka, both heavily impacted by human activities, show contrasting lake level trends: the level of Abiayata has dropped by about 5 m over three decades because of the extraction of water for soda and an upstream diversion for irrigation. Beseka has expanded from an area of 2.5 to 40 km2 over the last three decades because of increased groundwater inputs from percolated irrigation water. Lake Awassa has risen slightly due to land use changes resulting in increased runoff in its catchment. This paper addresses these lake level changes and their environmental repercussions, based on evidence from hydrometeorological records, hydrogeological field mapping supported by aerial photography and satellite imagery interpretations, water balance estimation, and hydrological modeling. A converging evidence approach is used to reconstruct the temporal and spatial variations of lake levels. The results reveal that the major changes in the rift valley are mainly related to anthropogenic factors. These changes appear to have grave environmental consequences for the fragile rift ecosystem. These consequences demand the very urgent implementation of integrated basin wide water management practice. 相似文献
337.
Istanbul has experienced rapid increases in population to more than 12 million people, which has created infrastructure problems of water supply and wastewater treatment and disposal. In this article, the achievements and approaches of the Istanbul Water and Sewerage Administration (ISKI) to solve the water shortage problem and to improve services are summarized. Istanbul had a very severe water shortage problem in 1994 because of ignorance of the implementation of the needed projects. After reviewing the reasons and causes of the problem, new priority criteria adopted after 1994 are given. Following the implementation of the projects determined according to the aforementioned criteria, water supplied has exceeded the water demand. The added capacity is equal to one to three times of the capacity built up to 1994 for water treatment, service reservoirs, pumping stations, transmission lines, and the water distribution network; water quality has been improved the meet local and international potable water standards. Unaccounted for water has been reduced from 60% to 27%. The percentage of treated wastewater has been increased from 10% to 90% in 8 years, resulting in drastic improvements and rehabilitation of the Golden Horn and coastal water quality. Through improved customer services, complaints were reduced from 33% in 1994 to 0.3%. Some of the main criteria and the approaches behind this success are summarized.
Published online 相似文献
338.
339.
Agricultural Land Use Effects on Sediment Loading and Fish Assemblages in Two Minnesota (USA) Watersheds 总被引:1,自引:1,他引:0
We examined the relationship between water quality and fish communities within two agricultural areas using a computer simulation model. Our analyses focused on a coolwater stream, Wells Creek in southeastern Minnesota, and a warmwater stream, the Chippewa River in western Minnesota. We used the Agricultural Drainage and Pesticide Transport (ADAPT) model in relation to land use to calculate instream suspended sediment concentrations using estimates of sediment delivery, runoff, baseflow and streambank erosion, and quantified the effects of suspended sediment exposure on fish communities. We predicted the effects of agricultural practices on stream fish communities under several possible land use scenarios, with reference to current conditions. Land use changes led to reductions in sediment loading of up to 84% in Wells Creek and 49% in the Chippewa River. The reduction in sediment loading across scenarios may be directly related to a reduction in runoff by about 35% in both study areas. We found a 98% decrease in lethal concentrations of suspended sediment on fish in Wells Creek with an increase in conservation tillage, riparian buffers, and permanent vegetative cover. However, the effects of suspended sediment did not significantly decrease in the Chippewa River. This difference between study areas was likely due to differences in tolerance to suspended sediment between coolwater and warmwater fish communities and differences in topography, runoff and bank erosion between the two streams.
The Minnesota Cooperative Fish and Wildlife Research Unit is jointly sponsored by the US Geological Survey, the University of Minnesota, the Minnesota Department of Natural Resources, and the Wildlife Management Institute. 相似文献
340.
"开放型"区域资源策略探析--以浙江省为例 总被引:1,自引:0,他引:1
本文从区域资源安全的内涵出发,以浙江省为研究对象,在分析了省域资源条件及供给现状的基础上,提出了构建“开放型”区域资源安全体系的总体思路。 相似文献