全文获取类型
收费全文 | 914篇 |
免费 | 52篇 |
国内免费 | 138篇 |
专业分类
安全科学 | 13篇 |
废物处理 | 7篇 |
环保管理 | 176篇 |
综合类 | 481篇 |
基础理论 | 199篇 |
污染及防治 | 20篇 |
评价与监测 | 59篇 |
社会与环境 | 126篇 |
灾害及防治 | 23篇 |
出版年
2024年 | 5篇 |
2023年 | 14篇 |
2022年 | 39篇 |
2021年 | 20篇 |
2020年 | 22篇 |
2019年 | 24篇 |
2018年 | 20篇 |
2017年 | 23篇 |
2016年 | 39篇 |
2015年 | 33篇 |
2014年 | 39篇 |
2013年 | 59篇 |
2012年 | 45篇 |
2011年 | 63篇 |
2010年 | 67篇 |
2009年 | 56篇 |
2008年 | 57篇 |
2007年 | 49篇 |
2006年 | 67篇 |
2005年 | 45篇 |
2004年 | 34篇 |
2003年 | 43篇 |
2002年 | 39篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 27篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有1104条查询结果,搜索用时 15 毫秒
991.
Here, we show for one of the Dutch Rhine River branches that large-scale riverine ecosystem rehabilitation and related vegetation
succession may lead to up to 0.6 m higher river flood levels, because of increased hydraulic roughness. We hydraulically modeled
future succession stages of embanked floodplain vegetation, following from present ecosystem rehabilitation plans for the
124-km-long river IJssel, and found flood levels exceeding the safety levels (related to dike heights). Our models take into
account river engineering measures that are presently carried out, aimed at enhancing the river discharge capacity in order
to meet required safety standards. Our study shows that there is a pressing need for integrated hydraulic-ecological evaluation
of river engineering measures and ecosystem rehabilitation plans in the Rhine embanked floodplains. An important conclusion
also is that hydraulic evaluation of planned vegetation goals only is inadequate, because flow resistance of preceding succession
stages may be higher. 相似文献
992.
Methodological approaches to the construction of phytoecological maps are described regarding specially protected nature areas and their specific features. Such maps offer new possibilities for the assessment and analysis of current and predicted states of vegetation. 相似文献
993.
The area along the Norwegian-Russian border is threatened by air pollution from emission sources on the Kola Peninsula. A permanent network of 78 systematically chosen monitoring sites has been established in eastern Finnmark, Norway. Species abundance data from the ground vegetation have been recorded from 1320 systematically chosen permanent plots inside 66 of these sites, using frequency in subplots and visual estimates of percentage cover. Environmental variables were obtained for the whole site. Multivariate data analysis has been used to describe the variation in the species composition and to study its relation to environmental variables and pollution impact. The analyses show that much of the variation in the species composition, based on average species abundance at the sites, is well explained by different soil and climatic conditions. However, estimated SO2 deposition, Ni, and Cu in the soil, and Ni in Cladina tissue have also been found to be statistically significantly correlated with the variation in the species data, but they explain only a minor part of the variation. The pollution impact over several years may have lead to a reduced lichen cover in the bottom-layer vegetation. Further development in an either negative or positive direction can be detected by re-investigations of the monitoring sites. 相似文献
994.
Building spectral libraries for wetlands land cover classification and hyperspectral remote sensing 总被引:3,自引:0,他引:3
Recent advances in remote sensing provide opportunities to map plant species and vegetation within wetlands at management relevant scales and resolutions. Hyperspectral imagers, currently available on airborne platforms, provide increased spectral resolution over existing space-based sensors that can document detailed information on the distribution of vegetation community types, and sometimes species. Development of spectral libraries of wetland species is a key component needed to facilitate advanced analytical techniques to monitor wetlands. Canopy and leaf spectra at five sites in California, Texas, and Mississippi were sampled to create a common spectral library for mapping wetlands from remotely sensed data. An extensive library of spectra (n=1336) for coastal wetland communities, across a range of bioclimatic, edaphic, and disturbance conditions were measured. The wetland spectral libraries were used to classify and delineate vegetation at a separate location, the Pacheco Creek wetland in the Sacramento Delta, California, using a PROBE-1 airborne hyperspectral data set (5m pixel resolution, 128 bands). This study discusses sampling and collection methodologies for building libraries, and illustrates the potential of advanced sensors to map wetland composition. The importance of developing comprehensive wetland spectral libraries, across diverse ecosystems is highlighted. In tandem with improved analytical tools these libraries provide a physical basis for interpretation that is less subject to conditions of specific data sets. To facilitate a global approach to the application of hyperspectral imagers to mapping wetlands, we suggest that criteria for and compilation of wetland spectral libraries should proceed today in anticipation of the wider availability and eventual space-based deployment of advanced hyperspectral high spatial resolution sensors. 相似文献
995.
通过野外调查和室内分析,对铜陵不同弃置堆放时间的铜矿尾矿的理化性质及植被定居状况进行了研究。结果表明,随着堆放时间的推移,表层尾矿的稳定性增加,基质结构改善,持水肥能力提高,有机质,全氮、有效磷、速效钾、有效铜及水溶性盐类含量上升,pH值降低,有的甚至出现酸化现象。铜矿尾矿的植被定居状况与其堆放时间及理化性质的变化有着密切关系。 相似文献
996.
997.
VINCENT KAKEMBO 《Environmental management》2001,28(1):39-46
Spatial and temporal variations in vegetation are examined in relation to land tenure, population increase, and rainfall variation
in a part of Peddie district, Eastern Cape. Sequential aerial photographs between 1938 and 1988 are analyzed to determine
trends in vegetation and population change in three different land-tenure units. The areal extent at each date of four distinct
vegetation categories is determined using PC ARC/INFO GIS. Long-term annual rainfall trends for the area are analyzed and
juxtaposed with vegetation changes. Extensive ground-truthing exercises are carried out to verify the present condition of
vegetation condition in terms of cover and species composition. Differences in land-tenure systems are discerned as the dominant
factor controlling variations in vegetation degradation. The study also reveals that neither population changes nor rainfall
variations can explain the observed trends in vegetation degradation. Earlier injudicious land-use practices, sustained since
the turn of the last century, may provide plausible explanations for the trends and present status of vegetation degradation
in the area. 相似文献
998.
Mining activities in Rakha copper mine (Jharkhand, India) were ceased in the year 2001, leaving a huge amount of untreated
tailings in the nearby tailings pond. The copper tailings contained high concentrations of heavy metals (total Cu, Ni concentrations
1779, 564 mgkg−1, respectively), and low contents of major nutrient elements and organic matter. Tailings are often very unstable, and a potential
vegetation cover may reduce the erosion or immobilize the toxicants to surrounding environment by phytostabilization. However,
high shoot concentrations of elements might disperse them and could be harmful to grazing animals. The objective of this study
was to find out which of the three properties; low-accumulation, root accumulation or shoot accumulation of elements (Cu,
Ni, Mn, Zn, Pb, Cd and Co), occur in the semi aquatic species Ammania baccifera growing on copper tailings. Roots of this species accumulated high levels of Cu, even more than 1000 mg kg−1, DW. Metals accumulated by A. baccifera were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them.
Thus, establishment of such plant on copper tailings can be a safe method to stabilize the metals. 相似文献
999.
环境规划中植物的景观功能及其应用 总被引:11,自引:0,他引:11
本文在探讨植物的景观特点及其建造功能和观赏功能等基础上,提出了环境规划中景观规划的基本原则。结合岳阳市南湖旅游度假区的实际情况,应用景观规划的基本原则,研究了该旅游度假区的面上绿化规划和景区景点绿化规划。 相似文献
1000.
T. V. Kotova I. M. Miklyaeva G. N. Ogureeva E. G. Suslova L. V. Shvergunova 《Russian Journal of Ecology》2000,31(5):318-323
Objectives and methods of mapping the ecological state of the plant cover at different spatial levels—federal, regional, and
local—are analyzed. The maps used as examples are as follows: at the federal level, “Ecological State of Rangelands in Russia”
(1:10 000 000); at the regional level, “Vegetation of Moscow Oblast” (1:200 000); and at the local level, “Vegetation of Narofominskii
Raion” and “Current State of the Plant Cover in Narofominskii Raion” (1:50 000). 相似文献