全文获取类型
收费全文 | 145篇 |
免费 | 8篇 |
国内免费 | 23篇 |
专业分类
安全科学 | 5篇 |
废物处理 | 7篇 |
环保管理 | 29篇 |
综合类 | 39篇 |
基础理论 | 34篇 |
污染及防治 | 13篇 |
评价与监测 | 9篇 |
社会与环境 | 39篇 |
灾害及防治 | 1篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 12篇 |
2012年 | 5篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有176条查询结果,搜索用时 437 毫秒
11.
Erik Krznaric Jan H.L. Wevers Jaco Vangronsveld 《Environmental pollution (Barking, Essex : 1987)》2009,157(5):1581-1588
Soil metal pollution can trigger evolutionary adaptation in soil-borne organisms. An in vitro screening test showed cadmium adaptation in populations of Suillus luteus (L.: Fr.) Roussel, an ectomycorrhizal fungus of pine trees. Cadmium stress was subsequently investigated in Scots pine (Pinus sylvestris L.) seedlings inoculated with a Cd-tolerant S. luteus, isolated from a heavy metal contaminated site, and compared to plants inoculated with a Cd-sensitive isolate from a non-polluted area. A dose-response experiment with mycorrhizal pines showed better plant protection by a Cd-adapted fungus: more fungal biomass and a higher nutrient uptake at high Cd exposure. In addition, less Cd was transferred to aboveground plant parts. Because of the key role of the ectomycorrhizal symbiosis for tree fitness, the evolution of Cd tolerance in an ectomycorrhizal partner such as S. luteus can be of major importance for the establishment of pine forests on Cd-contaminated soils. 相似文献
12.
Forest ecosystems may be actively managed toward heterogeneous stand structures to provide both economic (e.g., wood production
and carbon credits) and environmental benefits (e.g., invasive pest resistance). In order to facilitate wider adoption of
possibly more sustainable forest stand structures, defining growth expectations among alternative management scenarios is
crucial. To estimate the effect of tree size and spatial distributions on growth for forest structures commonly considered
in uneven-aged forest stand management, large (0.2 ha+) plots were established in 14 uneven-aged ponderosa pine stands in
eastern Montana. All study trees were stem-mapped and measured for diameter and 10-year sapwood and basal area increment.
A generalized growth model was developed to predict both total and merchantable 10-year basal area increment for nine hypothetical
stand structures [three diameter distributions (reverse-J, irregular, flat) × three spatial distributions (clumpy, partial
clumpy, uniform)]. Results indicate that the size and spatial distributions of individual trees have a considerable effect
on overall stand growth. The greatest total stand growth was in stands with reverse “J” shaped tree size distributions, while
the greatest merchantable stand growth was in stands with “flat” diameter distributions and uniform spatial distributions.
Through better comprehension of generalized uneven-aged stand growth dynamics, forest managers may better assess the effects
of alternative stand structures on stand growth while providing forest stand structures that may be more resilient in a changing
climate. 相似文献
13.
Steven W. Leavitt Austin Long 《Journal of the American Water Resources Association》1989,25(2):341-347
ABSTRACT: Stomatal closure during periods of moisture deficiency should theoretically lead to elevated 13C/12C ratios as reduction of available CO2 leads to diminished photosynthetic discrimination against 13C in favor of 12C. Stable-carbon isotope ratio chronologies developed from 5-yr tree-ring groups at 17 sites in six southwestern states were tested for a drought relationship by first fitting a spline curve to each chronology to remove the long-term trend and calculating indices as the ratio of actual to spline curve value. The time series of “Del Indices” so developed are significantly correlated with 5-yr mean Palmer Hydrological Drought Indices (post-1930 period) and reconstructed July Palmer Drought Severity Indices from respective areas. Overall, in the period since 1790, the driest pentads were 1900–04 and 1960–64, whereas the wettest were 1980–84 and 1915–19. Maps of drought represented for two pentads seem to be reasonable representations, although spatial correlations of Del Indices with PHDI were generally not significant. These Del Index drought reconstructions may provide a useful measure of past physiological response to drought (stomatal closure), although the present cost of analysis would prevent this from being a routine method. 相似文献
14.
ABSTRACT: The relative abundance of small mammals in five forest land cover types on the upper Coastal Plain of north Mississippi was determined. Burrowing mammals accounted for one-half of the total captures; one shrew species that accounted for over one-fourth of the total captures had a strong affinity for well-stocked pine plantations. The opportunity for detention and retention of rainfall was enhanced by burrowing activity. Reductions of stormflow volumes 12 to 15 years after replacing poor quality, upland hardwoods with loblolly pine were only partially explained by increased interception of rainfall; much of the residual reductions are postulated to be due to small mammal burrows. Small mammal activity deserves further study as an important aspect of forest land hydrology. 相似文献
15.
本文在西藏高山松进行的采脂试验和对松脂及其加工产品松香,松节油的成分,含量和质量分析的基础上,论述了西藏高山松松脂资源潜在的质量优势及其潜在的经济效益,据此结合西藏的实际,对开发利用高山松松脂资源的前景作了分析并提出了几点建议。 相似文献
16.
17.
Monitoring environmental pollution in Erzurum by chemical analysis of Scots pine (Pinus sylvestris L.) needles 总被引:3,自引:0,他引:3
Pollution distribution maps of copper (Cu), zinc (Zn) and lead (Pb) for Erzurum province were developed on the basis of chemical analysis of Scots pine (Pinus sylvestris L.) needles collected from randomly selected sampling points during 2 years. The maps show deposition zones for the studied elements and could help in identification of sources and directions of air pollution dispersion. This study indicated that vegetation in Erzurum was greatly endangered by sulphur dioxide (SO(2)), whereas Zn does not pose an immediate threat to vegetation in most of the country's territory. However, in the city center, main and secondary road agglomeration, very high pollution with Pb and Cu could limit growth. Higher levels of SO(2) measured in some areas of Erzurum might be harmful for human and animal health. Results of this study indicated that Scots pine needles were not contaminated by Zn. 相似文献
18.
Advantages of the informal assessment of biodiversity based on the phytosociological spectrum (the ratio of species associated with different higher units of ecological-floristic classification in the cenoflora) are demonstrated in a study of pine forests of the Southern Urals (classes Vaccinio-Piceetea, Brachypodio-Betuletea, and Querco-Fagetea). The phytosociological spectrum reflects environmental conditions better than formal estimations of , , and -diversity. 相似文献
19.
N. A. Kalashnik 《Russian Journal of Ecology》2008,39(4):261-271
The level of chromosome aberrations at different stages of mitosis has been studied in the seed sprout meristem of four conifer species growing in the Southern Urals in areas differing in the kind and degree of industrial pollution. The results provide evidence for the adverse effect of pollution on the chromosomal machinery of these species. With respect to environmental quality assessment, the Scots pine is the most sensitive indicator species among conifers growing in the Southern Urals and analysis of chromosome aberrations in anaphase-telophase cells is most effective among the cytogenetic methods tested. 相似文献
20.
Environmental conditions causing stress have a significant effect on the generative organs of Scotch pine. The parameters characterizing pine pollen are subject to significant interannual variations and are closely connected with weather and climatic conditions in the period of pollen formation. Airborne pollutants affect the quality of pine pollen, which is especially apparent in the years favorable for the formation of microspores. The ability of Scotch pine pollen to germinate and form pollen tubes in the regions with different technogenic loads proved to be significantly lower than in tree stands of the background areas. 相似文献