全文获取类型
收费全文 | 8695篇 |
免费 | 385篇 |
国内免费 | 699篇 |
专业分类
安全科学 | 485篇 |
废物处理 | 138篇 |
环保管理 | 2435篇 |
综合类 | 3258篇 |
基础理论 | 1036篇 |
环境理论 | 5篇 |
污染及防治 | 225篇 |
评价与监测 | 234篇 |
社会与环境 | 1682篇 |
灾害及防治 | 281篇 |
出版年
2024年 | 26篇 |
2023年 | 74篇 |
2022年 | 176篇 |
2021年 | 212篇 |
2020年 | 186篇 |
2019年 | 157篇 |
2018年 | 165篇 |
2017年 | 261篇 |
2016年 | 276篇 |
2015年 | 235篇 |
2014年 | 281篇 |
2013年 | 578篇 |
2012年 | 505篇 |
2011年 | 590篇 |
2010年 | 438篇 |
2009年 | 406篇 |
2008年 | 390篇 |
2007年 | 543篇 |
2006年 | 584篇 |
2005年 | 454篇 |
2004年 | 415篇 |
2003年 | 414篇 |
2002年 | 402篇 |
2001年 | 327篇 |
2000年 | 341篇 |
1999年 | 262篇 |
1998年 | 195篇 |
1997年 | 161篇 |
1996年 | 122篇 |
1995年 | 106篇 |
1994年 | 90篇 |
1993年 | 81篇 |
1992年 | 47篇 |
1991年 | 27篇 |
1990年 | 32篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 17篇 |
1986年 | 21篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 20篇 |
1981年 | 12篇 |
1980年 | 22篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1975年 | 10篇 |
1973年 | 10篇 |
1971年 | 14篇 |
排序方式: 共有9779条查询结果,搜索用时 31 毫秒
231.
Strategies for sustainable development of the small-scale gold and diamond mining industry of Ghana 总被引:1,自引:0,他引:1
The small-scale gold and diamonds mining industry is of great importance to Ghana. Since its regularization in 1989 the sector has produced and sold over 1.5 million troy ounces of gold and 8.0 million carats of diamonds. During the same period the sector also provided direct employment to over 100,000 people and improved the socioeconomic life of many individuals and communities. However, these were largely achieved at a cost to the environment in areas where mining is carried out and there is the need to develop the industry in a sustainable manner. This paper looks at the developments in the small-scale gold and diamonds mining industry in Ghana and proposes some strategies on how the concepts of sustainable development could be applied to the industry. 相似文献
232.
Gerard McMahon Jerad D. Bales James F. Coles Elise M. P. Giddings Humbert Zappia 《Journal of the American Water Resources Association》2003,39(6):1529-1546
ABSTRACT: This paper presents the results of a study on the use of continuous stage data to describe the relation between urban development and three aspects of hydrologic condition that are thought to influence stream ecosystems—overall stage variability, stream flashiness, and the duration of extreme‐stage conditions. This relation is examined using data from more than 70 watersheds in three contrasting environmental settings—the humid Northeast (the metropolitan Boston, Massachusetts, area); the very humid Southeast (the metropolitan Birmingham, Alabama, area); and the semiarid West (the metropolitan Salt Lake City, Utah, area). Results from the Birmingham and Boston studies provide evidence linking increased urbanization with stream flashiness. Fragmentation of developed land cover patches appears to ameliorate the effects of urbanization on overall variability and flashiness. There was less success in relating urbanization and streamflow conditions in the Salt Lake City study. A related investigation of six North Carolina sites with long term discharge and stage data indicated that hydrologic condition metrics developed using continuous stage data are comparable to flow based metrics, particularly for stream flashiness measures. 相似文献
233.
研究了柴油机掺烧液化石油气(LPG)以降低黑烟排放的技术方案,并开发出了一种以独特型板调节装置为特征的机械控制式柴油/LPG双燃料供给系统。发动机不改变原有结构加装该系统后即成为柴油/LPG双燃料发动机,可以同时燃烧柴油和LPG两种燃料,并且在整个工作范围内,随着工况变化能够按照预先优化设定的型板型线规律而自动调节柴油/LPG供给量比例,使烟度降低50%以上,同时满足经济性、动力性以及操作性能等要求,此外,也可以切换为单独燃烧柴油,而不改变发动机的原有性能。该系统结构简单、成本低廉,非常适合于改装城市在用公交车,降低其黑烟排放。 相似文献
234.
Oliveira Amauri P. Bornstein Robert D. Soares Jacyra 《Water, Air, & Soil Pollution: Focus》2003,3(5-6):3-15
The major topographic, mesoscale, and urban influences on the wind patterns of the City of São Paulo are characterized using one year of surface wind velocity data observed at 11 surface stations within its urban limits. The data was used to study the diurnal and annual variations of wind velocity and horizontal wind divergence within the city. Results showed that the circulation over the investigated area is dominated by three major factors: sea breeze; mountain-valley circulations; and urban effects, such as roughness, building-barrier, and urban heat island. The sea breeze was found to be the dominant feature of the monthly-averaged diurnal variation of São Paulo surface winds during the eight warmest months of the year. The sea breeze front induces a velocity minimum at the time of its passage and a post-frontal afternoon velocity maximum. Mountain-valley thermal effects on the flow can be seen in the temporal divergence/convergence patterns. These thermal effects tend to be more important during colder months, at night, and when the wind velocities are low. Nighttime downslope convergent flows are present over the city during winter and spring and daytime upslope divergent flows are present over the city during summer months. 相似文献
235.
Occurence and Distribution of Polycyclic Aromatic Hydrocarbons in Ankara Precipitation 总被引:1,自引:0,他引:1
Urban atmospheric environment contains many trace organic pollutants that are related to the incomplete fuel combustion in domestic heating, industrial plants and automobile traffic. Removal of these pollutants from the atmosphere takes place through wet and dry deposition as well as chemical transformations. In this study, concentrations of polycyclic aromatic hydrocarbons (PAHs) in wet deposition samples were determined at an urban site of Turkey. Wet and dry deposition samples were collected using Andersen Rain Sampler. The sampler was modified accordingly for the collection of organic pollutants. Collected samples were preconcentrated by using solid phase extraction (SPE) disks and consecutively analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Among the 13 compounds quantified in this study, anthracene, fluoranthene, and pyrene were found more frequently and at elevated concentrations (202, 271 and 260 ng L-1 mean concentrations, respectively).Concentrations of PAHs were found to be high in winter period. 相似文献
236.
237.
Georgios E. Pavlikakis Vassilios A. Tsihrintzis 《Journal of the American Water Resources Association》2003,39(2):277-288
ABSTRACT: The Ecosystem Management (EM) process belongs to the category of Multi‐Criteria Decision Making (MCDM) problems. It requires appropriate decision support systems (DSS) where “all interested people” would be involved in the decision making process. Environmental values critical to EM, such as the biological diversity, health, productivity and sustainability, have to be studied, and play an important role in modeling the ecosystem functions; human values and preferences also influence decision making. Public participation in decision and policy making is one of the elements that differentiate EM from the traditional methods of management. Here, a methodology is presented on how to quantify human preferences in EM decision making. The case study of the National Park of River Nestos Delta and Lakes Vistonida and Ismarida in Greece, presented as an application of this methodology, shows that the direct involvement of the public, the quantification of its preferences and the decision maker's attitude provide a strong tool to the EM decision making process. Public preferences have been given certain weights and three MCDM methods, namely, the Expected Utility Method, Compromise Programming and the Analytic Hierarchy Process, have been used to select alternative management solutions that lead to the best configuration of the ecosystem and are also socially acceptable. 相似文献
238.
介绍了活性灭火剂(ACP)的历史发展、灭火原理、配方原则、对配方要求和使用场合。可使读者对ACP获得较全面的了解。 相似文献
239.
240.
泥石流输沙对小江中下游河床演变的影响 总被引:4,自引:1,他引:4
对小江中下游近90km河床及两岸泥石流进行了调查研究。得到:泥石流输沙年际和季节变化大;泥石流高强度的输沙造成小江河床特殊的平面和剖面特征;泥石流堵塞小江河道,对纵比降有再造作用;泥沙使小江河床以年均20cm~50cm速度抬升。 相似文献