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451.
During April 2007, forest land per capita in the United States dropped below 1 ha. This is the result of a rather static area
of forest land in the United States for the past 100 years combined with population growth. The US now joins the ranks of
most countries (77%) having forest land per capita below 1 ha. The combination of an increasing human population with stable
or increasing per capita natural resource utilization may place even more demand on resources derived from forest land in
the future. The forest land per capita should be expected to continue its downward trend unless substantive demographic, resource
utilization, and land-use changes occur. 相似文献
452.
The article considers the impact of introducing government co-management policy in the form of Joint Forest Management (JFM) in an area with a five-decade-old self-organized community forest management system in Orissa, India. We ask a question that appears not to have been previously examined: What happens when JFM replaces an already existing community forest management arrangement? Our comparison of the JFM arrangement with the self-organized community forest management regime (pre- and post-2002 in a selected village) provides three conclusions: (1) The level of villager participation in forest management has declined, along with the erosion of the bundle of common rights held by them; (2) multiple institutional linkages between the village and outside agencies, and reciprocal relations with neighboring villages have been abandoned in favor of a close relationship with the Forestry Department; and (3) the administration of the forestry resource has become politicized. We conclude that the “one-size-fits-all” approach of the JFM, with its pre-packaged objectives and its narrow scope of forest management, is likely to limit experimentation, learning, and institutional innovation that characterizes community forest management. 相似文献
453.
Habitat fragmentation is the focus of much conservation concern and associated research. In some countries, such as Britain, the main phase of fragmentation occurred centuries ago and the focus of conservation management is now on restoration and recovery. Scenario studies have suggested that spatial targeting is preferable if landscape scale restoration is to be achieved, and that this should bring greater benefits than site-focussed activities but this has rarely been tested in practice. In Britain, woodland expansion has been encouraged through a number of financial incentives, which have evolved from instruments that encouraged almost any addition to the potential woodland resource, to grant schemes that have set out to restore connectivity to remnant ancient woodland. This study assessed the degree of de-fragmentation achieved by woodland expansion on the Isle of Wight and in particular the success of spatial targeting of new woodland planting implemented through grant aid in the JIGSAW (Joining and Increasing Grant Scheme for Ancient Woodland) scheme. Five steps in the re-development of broad-leaved woodland were tested using eight indicators - six commonly used landscape metrics, and two ecologically scaled indicators derived from application of least-cost network evaluation. Only half of the measures indicated de-fragmentation over the whole sequence of five steps. However, the spatial targeting did appear successful, when compared to equivalent untargeted grant-aided woodland expansion, and resulted in positive change to six of the eight indicators. We discuss the utility of the indicators and ways in which future targeting could be supported by their application. 相似文献
454.
Management of public lands occurs today with high levels of scrutiny and controversy. To succeed, managers seek the support,
involvement, and endorsement of the public. This study examines trust as an indicator of managerial success and attempts to
identify and measure the components that most influence it. A review of trust literature yielded 14 attributes that were hypothesized
to contribute to trust, grouped into the three dimensions of Shared Norms and Values, Willingness to Endorse, and Perceived
Efficacy. Operationalizing these attributes and dimensions, a telephone survey was administered to a sample of Montana, USA,
residents living adjacent to the Bitterroot National Forest (n = 1,152). Each of the attributes was measured in the context of federal lands fire and fuel management. Structural equation
modeling showed that all 14 attributes were found to be influential contributors to levels of trust. Results suggest that
if managers are to maintain or increase levels of public trust, they need to consider each of trust’s attributes as they make
social, ecological, and economic resource decisions. 相似文献
455.
Palmer JF 《Journal of environmental management》2008,89(3):167-183
The scenic effects of clearcutting have been a volatile issue for the American public for much of the past century. A better understanding of the scenic perceptions associated with the cumulative visible effects of clearcutting should contribute to better decisions about its use. This study evaluates the scenic impacts of simulated alternative clearcutting management systems for the White Mountain National Forest. Alternatives represented an unharvested view, and views with removal of 1–5% of the timber every 12 years using either scattered or concentrated clearcut units of 5, 15 and 30 acres in two viewsheds. A random sample of local citizens, four groups of opinion leaders, and US Forest Service employees evaluated these alternatives. Each factor accounts for significant differences in scenic value. All groups rated the scenic value of unharvested scenes very high. All groups find a large drop in scenic value with the introduction of even the least intense harvesting activity. All groups indicated a statistically significant decrease in visual quality as the intensity of harvesting increases. This effect continues throughout the range of harvesting intensities until the level of sustainable yield is reached. In addition, patches 12–15 acres in size were preferred to larger and smaller ones. 相似文献
456.
淡竹森林公园地处括苍山脉中部,保存有括苍山脉最好、最完整的常绿阔叶林,是浙中和浙东沿海区域原生性最强的原始次生森林。在系统调查的基础上,分析得出淡竹森林公园旅游资源的6大特点——风景资源品味较高,天然常绿阔叶林景观较典型,水体景观多姿多彩,山体和岩体景观奇妙,森林环境优异,山区风情较淳厚;提出了淡竹森林公园旅游开发的5条基本思路,即依法开发、保护为先,体现特色与周边景区互补相结合,突出重点与循序发展相结合,旅游产品应以自然性休闲型为主导,塑造主题旅游形象,强化宣传促销。 相似文献
457.
458.
459.
氯化钾交换—中和滴定法测定森林土壤交换性酸的研究 总被引:4,自引:0,他引:4
用Ⅰmol/L氯化钾交换-中和滴定法测定森林土壤交换性酸含量时,氯化钾淋洗液淋洗土壤时间建议定在50min左右,且用中速滤纸过滤淋洗液。 相似文献
460.
Biogenic volatile organic compounds (BVOCs) have significant effects on atmospheric chemistry, ozone formation and secondary organic aerosol formation. Considering few investigations about BOVCs emissions in north China where is facing serious air pollution in recent years, emissions of various BVOCs from 24 dominant forest species in Beijing were measured from June to September in 2018, using a dynamic headspace sampling method. More than one hundred BVOCs in the collected samples were identified by using an automatic thermal desorption-gas chromatography/mass spectrometry, and their emission rates based on leaf biomass were calculated. Isoprene and monoterpenes were verified to be the dominant BVOCs emitted from the tree species, accounting for more than 50% of the total BVOCs. Generally, broad-leaved species displayed high isoprene emission rates, especially the Platanus occidentalis (21.36 µg/(g?hr)), Robinia pseudoacacia (11.55 µg/(g?hr)), and Lonicera maackii (9.17 µg/(g?hr)), while coniferous species emitted high rates of monoterpenes, such as Platycladus orientalis (27.18 µg/(g?hr)), Pinus griffithii (23.11 µg/(g?hr)), and Pinus armandii (7.42 µg/(g?hr)). High emission rates of monoterpenes from the broad-leaved species of Buxus megistophylla (13.07 µg/(g?hr)) and Ligustrum vicaryi (5.74 µg/(g?hr)), and high isoprene emission rate from the coniferous tree of Taxus cuspidata (5.86 µg/(g?hr)) were also observed. The emission rates of sesquiterpenes from each tree were usually 10–100 times smaller than those of isoprene and monoterpenes. Additionally, relatively high emission rates of oxygenated volatile organic compounds and other alkenes than isoprene and monoterpenes were also found for several tree species. 相似文献