全文获取类型
收费全文 | 2618篇 |
免费 | 78篇 |
国内免费 | 974篇 |
专业分类
安全科学 | 189篇 |
废物处理 | 158篇 |
环保管理 | 205篇 |
综合类 | 1300篇 |
基础理论 | 460篇 |
污染及防治 | 1014篇 |
评价与监测 | 124篇 |
社会与环境 | 96篇 |
灾害及防治 | 124篇 |
出版年
2024年 | 1篇 |
2023年 | 45篇 |
2022年 | 121篇 |
2021年 | 92篇 |
2020年 | 77篇 |
2019年 | 94篇 |
2018年 | 82篇 |
2017年 | 113篇 |
2016年 | 136篇 |
2015年 | 174篇 |
2014年 | 223篇 |
2013年 | 269篇 |
2012年 | 201篇 |
2011年 | 221篇 |
2010年 | 204篇 |
2009年 | 180篇 |
2008年 | 171篇 |
2007年 | 148篇 |
2006年 | 157篇 |
2005年 | 111篇 |
2004年 | 94篇 |
2003年 | 80篇 |
2002年 | 88篇 |
2001年 | 118篇 |
2000年 | 78篇 |
1999年 | 71篇 |
1998年 | 73篇 |
1997年 | 52篇 |
1996年 | 41篇 |
1995年 | 40篇 |
1994年 | 31篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有3670条查询结果,搜索用时 218 毫秒
991.
关于旅游城市化问题的初步探讨——以长江三角洲都市连绵区为例 总被引:12,自引:0,他引:12
城市化发展的动力带动 ,城市旅游资源的富集 ,人口、经济的集聚与扩散 ,旅游供需关系的结合 ,旅游者对城市旅游目的地的选择行为 ,政策的导向 ,旅游业的发展和交通设施的完善等因素 ,导致了旅游城市化现象的产生。以长江三角洲都市连绵区为例 ,分析了旅游城市化进程中还存在发展思路不明 ,破坏旅游景观和生态环境 ,旅游规划与城市规划、城市发展不相适应 ,人口管理比较混乱 ,用地功能分区不明显 ,土地资源浪费严重等问题。提出了旅游城市化的发展对策 相似文献
992.
Distribution and migration of 95Zr in a tea plant/soil system 总被引:3,自引:0,他引:3
(95)Zr is a primary radionuclide in the radioactive liquid efflux from a pressurized water reactor and one of the main radionuclides released after nuclear accidents. The fission yield of (95)Zr is as high as 6.2%, however, its environmental behavior has not been well documented. An experiment was conducted to evaluate the accumulation and distribution of (95)Zr in a tea plant/soil system. (95)Zr was accumulated primarily in the trunk of tea plants after being taken up from the soil. The radioactivity concentration of (95)Zr in the trunk increased slowly with time, then it reached a dynamic equilibrium 14 days after application. The radioactivity concentration of (95)Zr in the other parts of the tea plant was very low; only slighter greater than the detection limit. The results indicated that (95)Zr was not readily translocated in the tea plant. About 98.9% of applied (95)Zr was found to concentrate in the upper 5 cm layer after being sprayed onto the soil surface. The results indicated that (95)Zr could not readily move downwards with percolating water due to strong adsorption to surface soil. 相似文献
993.
Indicators to distinguish between fecal coliforms of human and animal origin were investigated in water from storm sewer outfalls to a coastal lake during wet and dry weather. The ratio of fecal coliform relative to fecal streptococci count was used as the microbiological indicator. Concentrations of human-activities originated caffeine, anionic surfactant, fluoride, and fluorescence whitening agent (FWA) were used as chemical indicators. The ratio of fecal coliform to fecal streptococci ranged from 0.2 to 3.0, during wet weather making it difficult to interpret the origin of fecal pollution. However, concentrations of caffeine, anionic surfactant, fluoride, and FWA in storm water outflow during wet weather were much higher than those in the lake water during dry weather, indicating the presence of human waste at storm water outfall. Strong correlation between fecal coliform counts and chemical parameter values further indicated the human contribution to the fecal coliform count. In addition, a strong correlation among the chemical parameters suggested that only one of them is needed as chemical tracer to detect the presence of human input. 相似文献
994.
995.
996.
997.
Adsorption of Pb and Cd in the presence and absence of organochlorine pesticides (OCPs) on natural surface coatings (NSCs), which were collected in the Nanhu Lake in Changchun, China, was measured in order to investigate the effect of the OCPs on the adsorption of heavy metals on the NSCs. Adsorption of Pb/Cd was carried out under controlled laboratory conditions (mineral salt solution with defined species, ionic strength 0.05 mol/l, 25 degrees C and pH 6.0) with initial Pb and Cd concentrations ranging from 0.2 to 2.5 mol/l. The classical Langmuir adsorption isotherm was applied to estimate the equilibrium coefficients of the adsorption of Pb and Cd on the NSCs. Adsorption interference between Pb/Cd and the OCPs on the NSCs indicated that the adsorption of Pb/Cd on the NSCs was influenced by the OCPs, and competitive adsorption between Pb and the OCPs was observed while adsorption of Cd was enhanced by addition of the OCPs. Adsorption data fit the Langmuir isotherm well for the NSCs treated with the OCPs at different equilibrium concentrations. The results showed that the amount of adsorbed Pb decreased by more than 40% while the amount of adsorbed Cd increased by over 60% with an increase in the initial concentrations of the OCPs ranging from 0 to 5.0 microg/l and that adsorption of Pb/Cd on the NSCs was strongly affected by the OCPs. This preliminary study highlights the importance of the OCPs on the NSCs in controlling the transport, fate, biogeochemistry, bioavailability and toxicity of trace metals in aquatic environments. 相似文献
998.
郭英杰 《中国环境管理干部学院学报》2008,18(3)
从秦皇岛市海港区城市游憩绿地存在的空间分布不均匀、设计不完善、疏于管理、服务设施不足等问题出发,提出了从宏观调控、游憩绿地设计、管理、法制、可持续发展和建设投入角度发展海港区城市游憩绿地的对策,从而提高城市人居环境质量,充分发挥城市游憩绿地系统在整个城市绿地系统中的重要地位。 相似文献
999.
Yanhui Wang Pengtao Yu Wei Xiong Zhenxi Shen Mingchun Guo Zhongjie Shi Apeng Du Liangmin Wang 《Journal of the American Water Resources Association》2008,44(5):1086-1097
Abstract: The increase of coverage of forest/vegetation is imperative to improve the environment in dry‐land areas of China, especially for protecting soil against serious erosion and sandstorms. However, inherent severe water shortages, drought stresses, and increasing water use competition greatly restrict the reforestation. Notably, the water‐yield reduction after afforestation generates intense debate about the correct approach to afforestation and forest management in dry‐land areas. However, most studies on water‐yield reduction of forests have been at catchment scales, and there are few studies of the response of total evapotranspiration (ET) and its partitioning to vegetation structure change. This motivates us to learn the linkage between hydrological processes and vegetation structure in slope ecosystems. Therefore, an ecohydrological study was carried out by measuring the individual items of water balance on sloping plots covered by different vegetation types in the semiarid Liupan Mountains of northwest China. The ratio of precipitation consumed as ET was about 60% for grassland, 93% for shrubs, and >95% for forestland. Thus, the water yield was very low, site‐specific, and sensitive to vegetation change. Conversion of grassland to forest decreased the annual water yield from slope by 50‐100 mm. In certain periods, the plantations at lower slopes even consumed the runon from upper slopes. Reducing the density of forests and shrubs by thinning was not an efficient approach to minimize water use. Leaf area index was a better indicator than plant density to relate ET to vegetation structure and to evaluate the soil water carrying capacity for vegetation (i.e., the maximum amount of vegetation that can be supported by the available soil water for an extended time). Selecting proper vegetation types and plant species, based on site soil water condition, may be more effective than the forest density regulation to minimize water‐yield reduction by vegetation coverage increase and notably by reforestation. Finally, the focuses in future research to improve the forest‐water relations in dry‐land areas are recommended as follows: vegetation growth dynamics driven by environment especially water conditions, coupling of ecological and hydrological processes, further development of distributed ecohydrological models, quantitative relation of eco‐water quota of ecosystems with vegetation structures, multi‐scaled evaluation of soil water carrying capacity for vegetation, and the development of widely applicable decision support tools. 相似文献
1000.
Bioaccumulation and physiological effects of tetrabromobisphenol A in coontail Ceratophyllum demersum L 总被引:2,自引:0,他引:2
Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants. In the present study, the accumulation of TBBPA and its consequent biological responses were examined in coontail (Ceratophyllum demersum L.) over 14 days' exposure. Most of the TBBPA was accumulated after 4d exposure and TBBPA concentration in plant increased with increasing TBBPA concentration in growth solution (R(2)=0.99). By using electron paramagnetic resonance (EPR), we found that the TBBPA exposure significantly increased total free radicals generation in the plants. A good positive relationship (R(2)=0.99) was found between the free radicals formation and accumulation level of TBBPA in plant. Lipid peroxidation was enhanced and chlorophyll content showed declined after TBBPA exposure. The activities of superoxide dismutase (SOD), peroxidase (POD), and the contents of glutathione were also detected. The results suggest that TBBPA accumulation in C. demersum induces oxidative stress and the level of tolerance depends on the antioxidative capacity of the plants. 相似文献