全文获取类型
收费全文 | 2553篇 |
免费 | 263篇 |
国内免费 | 710篇 |
专业分类
安全科学 | 405篇 |
废物处理 | 35篇 |
环保管理 | 296篇 |
综合类 | 1514篇 |
基础理论 | 494篇 |
环境理论 | 1篇 |
污染及防治 | 151篇 |
评价与监测 | 61篇 |
社会与环境 | 374篇 |
灾害及防治 | 195篇 |
出版年
2024年 | 18篇 |
2023年 | 65篇 |
2022年 | 130篇 |
2021年 | 126篇 |
2020年 | 126篇 |
2019年 | 129篇 |
2018年 | 108篇 |
2017年 | 132篇 |
2016年 | 137篇 |
2015年 | 131篇 |
2014年 | 116篇 |
2013年 | 163篇 |
2012年 | 206篇 |
2011年 | 242篇 |
2010年 | 166篇 |
2009年 | 190篇 |
2008年 | 145篇 |
2007年 | 186篇 |
2006年 | 144篇 |
2005年 | 143篇 |
2004年 | 107篇 |
2003年 | 99篇 |
2002年 | 71篇 |
2001年 | 52篇 |
2000年 | 68篇 |
1999年 | 47篇 |
1998年 | 46篇 |
1997年 | 38篇 |
1996年 | 32篇 |
1995年 | 28篇 |
1994年 | 35篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有3526条查询结果,搜索用时 109 毫秒
891.
沈阳商业城火灾及灾后修复 总被引:1,自引:0,他引:1
介绍了发生在沈阳商业城的火灾及灾后调查、检测和加固情况,从中得到一些有意义的看法。 相似文献
892.
TEKLE K 《Environmental management》1999,23(4):419-427
/ Understanding the problems of land degradation and seeking long-lasting solutions to these problems should be one of the central concerns of countries such as Ethiopia where agriculture is the mainstay of no less than 85% of the population. To this end, the collaboration of policy makers, researchers, donor agencies, and the local people is indispensable. In this paper an attempt is made to discuss the causes of land degradation and the reasons for the failure in the endeavors made to solve the problems. Possible solutions, which may help to ameliorate the situation, are also suggested. The study deals with South Wello (a region in northern Ethiopia), but the assessment is, by and large, a reflection of most of the highlands in the country. KEY WORDS: Agroforestry; Donor agencies; Food for work; Hillside closures; Land rehabilitation; Local participation; Population growth; Reforestation 相似文献
893.
This article describes and tests a systems theory-based policy indicators model. The framework is used to examine propositions
about linkages between states' ecological-spatial characteristics and subsequent selected solid waste management (SWM) -related
environmental policies. It was hypothesized that state characteristics of: (1) population density (used as a garbage-per-land
area index), (2) population convergence within urban areas, and (3) percent population change in the interval 1980–1985, could
jointly explain state variation in both the number and the vigor of SWM policy outputs. Greater levels of spatial pressure
were proposed to be related directly to more numerous, more convincing policies. Proposals are grounded in the literature
of organizational search theory, crisis stimulation, and technological pressure.
Results revealed that the sociospatial model in fact could explain a reasonable proportion of policy variation across states.
However, not all hypotheses are supported. Population change shows an indirect, rather than the anticipated direct, relationship
with policy output levels. In addition, when used in the model as a pollution intensity index, population density failed to
contribute significantly to an explanation of differences in state SWM policy levels. The analysis raises questions about
changes occurring over time in the nature and direction of linkages between sociospatial measures and policy responses. This
study suggests that strengthening policy indicator models may require questioning key assumptions and theoretical bases, conducting
longitudinal studies, and factoring in political, economic, and other policy environment forces. 相似文献
894.
Mammalian communities were studied on 10 surface mines over a four year period. The size and composition of these communities varied among the different areas. The size, composition, and spatial distribution of these mammalian communities were related to the structure of the plant community, and native plant species were of greater importance in determining size and composition of these communities than were those used in reclamation. 相似文献
895.
There is abundant evidence that many factors can influence the toxicity of a particular pollutant including environmental fluctuations, season of the year, stage in life cycle, size, and sex. All of these factors should be assessed before making a judgment of the effect on natural populations. Such an assessment can be conceptualized using a simple population model through whichcontrol gates operate as functions of 1). the direct self-maintainance feedback from existing adult population biomass and 2). the recruitment of new individuals due to the maturation of larvae. By extracting general principles of organismic response to pollutants it is possible to incorporate the information into large-scale ecosystem models which would serve as working tools for answering environmental decision-making problems. 相似文献
896.
旅皖国内旅游者消费结构初探 总被引:14,自引:0,他引:14
分析比较了2001年旅皖国内旅游者消费结构的特点和原因,认为国内旅游者消费结构以刚性旅游消费为主,弹性旅游消费比重较低;普遍具有较强的住宿、餐饮消费偏好,购物、娱乐是消费弱项.为引导旅游者关注弹性消费,实现消费结构合理化,促进安徽省旅游业产业结构的优化升级和经济效益的持续增长,应构建形式多样的大众娱乐设施,丰富旅游景区的娱乐功能,提升旅游商品档次和销售能力,建设多功能购物街,多方位营造安全的旅游消费环境. 相似文献
897.
九华山国内客源市场空间结构与出游行为研究 总被引:6,自引:3,他引:6
在实地调查的基础上,分析了九华山国内客源市场空间结构及其演变特征,得出国内客源市场集中程度降低、客源吸引力不断增强、波浪式推进的演变结论,并探讨了九华山旅游行为空间模式主要以单一目的地旅游模式和区域旅游模式为主,根据旅游意向调查结果显示,九华山与黄山在客源市场方面具有较强的互补性。 相似文献
898.
899.
空间结构展示了一个国家建筑科技新成果和实力 ,由于建筑业的特殊性 ,其安全性备受关注。笔者阐述了空间结构的施工特点以及施工中人为错误的成因和对工程的影响 ,通过对人为错误与建筑风险造价关系的分析 ,提出了控制人为错误的对策为 :适当提高结构设计可靠度水平和加强施工过程的管理 ,减少人为错误的发生 ,对遏制工程质量事故具有指导意义。 相似文献
900.
Smith JG 《Environmental management》2003,32(1):77-92
Recovery of the benthic macroinvertebrate community in a small east Tennessee stream impacted by fly ash discharges from a power plant was investigated over a period of 6.5 years. The rate of recovery was greatest in the first 2 years after an initial 75% reduction in coal use led to a similar reduction in ash discharges and associated contaminants; further recovery followed after all fly ash discharges ceased. Recovery of the stream progressed through two phases. In the first phase, which lasted for approximately the first 2 years, most density and richness metrics increased considerably. In the second phase of recovery, the increases in metric values were followed by declines before fluctuating in and out of the lower reference ranges for the metrics. Detrended correspondence analyses and indicator species analyses showed that changes in species composition and community structure were ongoing throughout the second phase. Thus, the first phase was characterized by species additions, while the second phase involved species replacements and shifts in community dominants. Further recovery of the macroinvertebrate community will probably depend on additional flushing of fly ash deposits from the streambed and flood plain, because their continued presence reduces habitat quality in the stream and serves as a potential source of contaminants. Further recovery also may be limited by the availability of vagile species in nearby watersheds. 相似文献