全文获取类型
收费全文 | 821篇 |
免费 | 38篇 |
国内免费 | 118篇 |
专业分类
安全科学 | 47篇 |
废物处理 | 42篇 |
环保管理 | 230篇 |
综合类 | 262篇 |
基础理论 | 185篇 |
污染及防治 | 134篇 |
评价与监测 | 24篇 |
社会与环境 | 36篇 |
灾害及防治 | 17篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 15篇 |
2021年 | 16篇 |
2020年 | 24篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 22篇 |
2016年 | 34篇 |
2015年 | 30篇 |
2014年 | 34篇 |
2013年 | 40篇 |
2012年 | 40篇 |
2011年 | 71篇 |
2010年 | 41篇 |
2009年 | 96篇 |
2008年 | 76篇 |
2007年 | 52篇 |
2006年 | 64篇 |
2005年 | 27篇 |
2004年 | 33篇 |
2003年 | 33篇 |
2002年 | 18篇 |
2001年 | 16篇 |
2000年 | 25篇 |
1999年 | 17篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 25篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有977条查询结果,搜索用时 312 毫秒
281.
282.
This paper explores the positive aspects of collaboration in natural resources. Its purpose was to investigate participants'
overall attitudes about keys to successful collaboration. The sample for the study consisted of 671 participants involved
in 30 collaborative initiatives (CI) with the Forest Service. Using a mailed questionnaire, this study profiled the collaborative
initiatives investigating purpose, problems addressed, groups involved, and years in existence. Respondents were queried on
their overall perspectives on keys to successful collaboration. A total of more than 300 comments was collected from respondents
and six categories emerged: development, information exchange, organizational support, personal communication, relationships/team
building, and accomplishments. Continued research will need to explore the short- and long-term impacts of collaboration in
natural resources. 相似文献
283.
284.
285.
A. Begossi 《Regional Environmental Change》2001,2(1):1-12
This study analyzes the fishing areas or spots used by artisanal fishers of the Atlantic Forest coast. Fishers include inhabitants
of islands of the SE Atlantic Forest in Brazil. Data on fish landings were collected for different islands, in 1986 and 1989–1990,
for species caught, technology used and fishing time. Fishing spots were marked or rechecked using GPS in 1997–1999. Fishing
is performed in paddled, motorized canoes or in small boats with set gillnets or hook and line. Marine animals caught vary
from place to place and include fish, shrimp, squid and crab. Spots used are very stable in time, since they did not change
for about 10 years. Among other factors, technology limits the range of access of the fishers to the spots. An informal division
of fishing areas or spots is observed, based on the locality of residence of the fishers. The mapping and observed division
of fishing spots may be used in local management, helping to control the intrusion of industrial fishers in artisanal areas.
Local rules and discrimination of spot users may be helpful for artisanal fishers, especially in areas where conflicts with
trawlers occur. The observed long-term stability of the use of fishing spots by artisanal fishers and conflicts with other
users indicate the urgency of considering local rules for conservation purposes in Atlantic Forest coastal areas.
Electronic Publication 相似文献
286.
森林特殊火行为格局的卫星遥感研究 总被引:13,自引:4,他引:9
由于多变的天气条件,复杂的地形和植被分布,引起火行为格局的变化,借助GIS和卫星遥感技术,以1987年大兴安岭5.6大火为对策,进行火行为变化规律和火行为的时空格局研究,环境风对火行为具有决定性作用,大风期间火强度极高,过火区为火蔓延的廓道,较大的山脉对林火有阻隔作用,森林采伐改变可燃物连续性,可以改变火行为,人类扑火对大火作用不明显,小地形可产生不同火烧强度的细微结构。 相似文献
287.
G. Deckmyn H. Verbeeck M. Op de Beeck D. Vansteenkiste K. Steppe R. Ceulemans 《Ecological modelling》2008
A stand-scale forest model has been developed that dynamically simulates, besides carbon (C) and water (H2O) fluxes, wood tissue development from physiological principles. The forest stand is described as consisting of trees of different size cohorts (for example, dominant, co-dominant and suppressed trees), either of the same or of different species (deciduous or coniferous). Half-hourly C and H2O fluxes are modeled at the leaf, tree and stand level. In addition to total growth and yield, the model simulates the daily evolution of tracheid or vessel biomass and radius, parenchyma and branch development. From these data early and latewood biomass, wood tissue composition and density are calculated. Simulation of the labile C stored in the living tissues allows for simulation of trans-seasonal and trans-yearly effects, and improved simulations of long-term effects of environmental stresses on growth. A sensitivity analysis was performed to indicate the main parameters influencing simulated stem growth and wood quality at the tree and stand level. Case studies were performed for a temperate pine forest to illustrate the main model functioning and, more in particular, the simulation of the wood quality. The results indicate that the ANAFORE model is a useful tool for simultaneous analyses of wood quality development and forest ecosystem functioning. 相似文献
288.
Spatial pattern and persistence of historical fire boundaries in southern interior British Columbia 总被引:2,自引:0,他引:2
Geraldine J. Jordan Marie-Josée Fortin Kenneth P. Lertzman 《Environmental and Ecological Statistics》2008,15(4):523-535
Recent ecosystem and fire management research aims to quantify, model and understand historical fire disturbances focusing
on their frequency, size and distribution. Less attention, however, has been paid to fire boundaries and their location on
the landscape. Our study presents a spatial method to quantify the location, pattern and persistence of historical fire boundaries
using tree ring fire scar data in the lower Stein watershed (British Columbia). Data from Pinus ponderosa and Pseudotsuga menziesii collected in 35 one-hectare plots over a 412-hectare study area were analyzed for the period between 1879 and 1947 using
local spatial statistics and boundary detection techniques. Results of the analysis using local spatial statistic Moran’s
I showed significant clustering of boundaries near topographic breaks. To determine and test whether fire boundaries between
plots were persistent, we used boundary detection methods and developed a spatially restricted randomization test. The results
revealed that out of 86 possible boundary links, 8 were significantly persistent (P < 0.025) while another 8 were significantly rare (P < 0.025). These spatial methods can help determine the historical spatial configuration of persistent boundaries and can
be used to maintain natural forest dynamics.
相似文献
Geraldine J. JordanEmail: |
289.
Krzysztof Lipka 《Journal of environmental science and health. Part. B》2017,52(3):184-190
ABSTRACTThis study was carried out on the accumulation and occurrence of Ag, Al, Ba, Ca, Cd, Co, Cu, Fe, Hg, K, Mg, Mn, Na, Rb, Sr and Zn in the mushroom Amanita muscaria and forest topsoil from two lowland sites in the Tuchola Pinewoods in the north-central region and an upland site in the ?wietokrzyskie Mountains in the south-central region of Poland. Topsoil from the upland location showed Ag, Al, Ba, Ca, Cd, Co, Cu, Fe, Hg, Na and Zn at significantly higher concentration levels (pseudo-total fraction and often also the labile or extractable fraction) than at both lowland locations, where topsoil was richer in Mg, and similar in Rb. Amanita muscaria from the upland region differed from individuals collected in the lowland sites by higher concentration levels of Cd, Cu, Hg and Mn in caps. This could be related to higher concentration levels of the metallic elements in topsoil in the upland region. On other side, A. muscaria from the upland site was poorer in Co and Fe in caps, and in Ca, Co, Fe and Sr in stipes. In spite of the differences in content of the geogenic metallic elements in topsoil between the lowland and upland locations, A. muscaria from both regions was able to regulate uptake and accumulation of Ag, Al, Ba, Ca, K, Mg, Na, Rb and Zn, which were at similar concentration levels in caps but not necessarily in stipes. 相似文献
290.
The natural range of variation of ecosystems provides reference conditions for sustainable management and biodiversity conservation. We review how the understanding of natural reference conditions of boreal forests in northern Europe has changed from earlier perceptions of even-aged dynamics driven by stand-replacing disturbances towards current understanding highlighting the role of non-stand-replacing disturbances and the resultant complex forest dynamics and structures. We show how earlier views and conceptual models of forest disturbance dynamics, including the influential ASIO model, provide estimates of reference conditions that are outside the natural range of variation. Based on a research synthesis, we present a revised forest reference model incorporating the observed complexity of ecosystem dynamics and the prevalence of old forests. Finally, we outline a management model and demonstrate its use in forest ecosystem management and show how regional conservation area needs can be estimated. We conclude that attaining favourable conservation status in northern Europe’s boreal forests requires increasing emphasis on ecosystem management and conservation for old forest characteristics.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01444-3) contains supplementary material, which is available to authorized users. 相似文献