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801.
本文通过林业建设环境分析、论证,提出一江两河地区综合防护林体系建设的战略构想:在认真保护、科学经营现有森林资源的基础上,以拉萨河、雅鲁藏布江中段、年楚河谷地为主线,重点建设沿江防护林带,构成防护林体系的主要骨架;在河谷农田草场加速防护林网建设,完成防护林体系的网络结构;依土地条件积极营造薪炭林,适当发展用材林和四旁植树(含林卡和经济果树等),完善防护林体系的带网片结,建立起我国高原最大的综合防护林体系,保护好地理环境独特的高寒农业区和“世界第三极”。 相似文献
802.
803.
杨树是黄土高原的主要树种之一。本文根据阴山东段不同立地条件下25年生的四种杨树解析木生长量资料,与该地区同时期气候因素进行了关联分析,按关联度大小,选取了八个气候因素作为聚类因子,再将关联度归一化,求得各因子的权重,表示各气候因素对树木生长作用的大小。最后根据黄土高原西部68个气象站1951—1980年的气候资料,应用动态聚类分析法,把黄土高原西部地区划分成几个不同类型林业气候区,区划结果与实际考察基本相符合。 相似文献
804.
Lasco Rodel D. Pulhin Florencia B. 《Mitigation and Adaptation Strategies for Global Change》2000,5(1):81-97
Tropical forests in countries like thePhilippines are important sources and sinks of carbon(C). The paper analyzes the contribution of Philippineforests in climate change mitigation. Since the 1500s,deforestation of 20.9 M ha (106 ha) of Philippineforests contributed 3.7 Pg (1015 g) of C to theatmosphere of which 2.6 Pg were released this century. At present, forest land uses store 1091 Tg(1012 g) of C and sequester 30.5 Tg C/yr whilereleasing 11.4 Tg C/yr through deforestation andharvesting. In the year 2015, it is expected that thetotal C storage will decline by 8% (1005 Tg) andtotal rate of C sequestration will increase by 17%(35.5 Tg/yr). This trend is due to the decline innatural forest area accompanied by an increase intree plantation area. We have shown that uncertaintyin national C estimates still exists because they arereadily affected by the source of biomass and Cdensity data. Philippine forests can act as C sink by:conserving existing C sinks, expanding C stocks, andsubstituting wood products for fossil fuels. Here weanalyze the possible implications of the provisions ofthe Kyoto Protocol to Philippine forests. Finally, wepresent current research and development efforts ontropical forests and climate change in the Philippinesto improve assessments of their role in the nations Cbudgets. 相似文献
805.
Laturnus F Fahimi I Gryndler M Hartmann A Heal MR Matucha M Schöler HF Schroll R Svensson T 《Environmental science and pollution research international》2005,12(4):233-244
- DOI: http:/dx.doi.org/10.1065/espr2005.06.262
Goal, Scope and Background The anthropogenic environmental emissions of chloroacetic acids and volatile organochlorines have been under scrutiny in
recent years because the two compound groups are suspected to contribute to forest dieback and stratospheric ozone destruction,
respectively. The two organochlorine groups are linked because the atmospheric photochemical oxidation of some volatile organochlorine
compounds is one source of phytotoxic chloroacetic acids in the environment. Moreover, both groups are produced in higher
amounts by natural chlorination of organic matter, e.g. by soil microorganisms, marine macroalgae and salt lake bacteria,
and show similar metabolism pathways. Elucidating the origin and fate of these organohalogens is necessary to implement actions
to counteract environmental problems caused by these compounds.
Main Features While the anthropogenic sources of chloroacetic acids and volatile organochlorines are relatively well-known and within human
control, knowledge of relevant natural processes is scarce and fragmented. This article reviews current knowledge on natural
formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soils, with particular emphasis
on processes in the rhizosphere, and discusses future studies necessary to understand the role of forest soils in the formation
and degradation of these compounds.
Results and Discussion Reviewing the present knowledge of the natural formation and degradation processes of chloroacetic acids and volatile organochlorines
in forest soil has revealed gaps in knowledge regarding the actual mechanisms behind these processes. In particular, there
remains insufficient quantification of reliable budgets and rates of formation and degradation of chloroacetic acids and volatile
organochlorines in forest soil (both biotic and abiotic processes) to evaluate the strength of forest ecosystems regarding
the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale.
Conclusion It is concluded that the overall role of forest soil as a source and/or sink for chloroacetic acids and volatile organochlorines
is still unclear; the available laboratory and field data reveal only bits of the puzzle. Detailed knowledge of the natural
degradation and formation processes in forest soil is important to evaluate the strength of forest ecosystems for the emission
and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale.
Recommendation and Perspective As the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil can
be influenced by human activities, evaluation of the extent of this influence will help to identify what future actions are
needed to reduce human influences and thus prevent further damage to the environment and to human health caused by these compounds. 相似文献
806.
Yoshihiro Nagahama Katsuhisa Suzuki 《Atmospheric environment (Oxford, England : 1994)》2007,41(40):9570-9579
Total column abundances of CO, HCN, C2H6, and C2H2 have been retrieved from infrared solar spectra observed at Moshiri (44.4°N) and Rikubetsu (43.5°N) in northern Japan from 1997 to 2005. The spectra were recorded with high spectral resolution ground-based Fourier transform infrared (FTIR) spectrometers and total column abundances were calculated by SFIT1 version 1.09e. Deviations of these species relative to their seasonal mean values (ΔCO, ΔHCN, ΔC2H6, and ΔC2H2) were derived, which showed short-time enhancements in 1998, 2002, and 2003. Good correlations among ΔCO, ΔHCN, ΔC2H6, and ΔC2H2 in a few months of each year were seen. Since the number of forest fires in Siberia had large enhancements in 1998, 2002, and 2003, trajectory analyses were performed in order to assess the influence of forest fires and it was confirmed that air masses passing over the location of burning points in Siberia reached Moshiri and Rikubetsu. This paper shows that enhancements of these species were driven by biomass burning in Siberia. 相似文献
807.
扁刺栲在两种类型林分中的生长过程分析 总被引:5,自引:0,他引:5
通过对扁刺栲—华木荷林区针阔混交林、次生阔叶林的群落调查以及扁刺栲的树干解析.研究结果表明:(1)扁刺栲在针阔混交林与次生阔叶林中,胸径快速生长期分别在a8~12和a10~14之间,生长高峰值分别出现在a10和a12,最大值分别为1.07cm和0.85cm.(2)扁刺栲在针阔混交林与次生阔叶林中,树高快速生长期分别在a6~10和a10~14之间,生长高峰值分别出现在a8和a10,最大值分别为0.55m和0.56m.(3)在针阔混交林中,16a生扁刺栲单株材积达0.0134m^3,而在次生阔叶林中只有0.0103m^3.在分析不同林分中扁刺栲生长差异及其原因的基础上,建议对次生阔叶林经营应采用动态管理. 相似文献
808.
The Northwest Forest Plan: Origins, Components, Implementation Experience, and Suggestions for Change 总被引:5,自引:0,他引:5
JACK WARD THOMAS JERRY F. FRANKLIN† JOHN GORDON‡ K. NORMAN JOHNSON§ 《Conservation biology》2006,20(2):277-287
Abstract: In the 1990s the federal forests in the Pacific Northwest underwent the largest shift in management focus since their creation, from providing a sustained yield of timber to conserving biodiversity, with an emphasis on endangered species. Triggered by a legal challenge to the federal protection strategy for the Northern Spotted Owl ( Strix occidentalis caurina ), this shift was facilitated by a sequence of science assessments that culminated in the development of the Northwest Forest Plan. The plan, adopted in 1994, called for an extensive system of late-successional and riparian reserves along with some timber harvest on the intervening lands under a set of controls and safeguards. It has proven more successful in stopping actions harmful to conservation of old-growth forests and aquatic systems than in achieving restoration goals and economic and social goals. We make three suggestions that will allow the plan to achieve its goals: (1) recognize that the Northwest Forest Plan has evolved into an integrative conservation strategy, (2) conserve old-growth trees and forests wherever they occur, and (3) manage federal forests as dynamic ecosystems. 相似文献
809.
810.
Pamela R. Veltkamp Kristen J. Hansen Robert M. Barkley Robert E. Sievers 《Environmental geochemistry and health》1996,18(2):77-80
Various organic compounds in aerosol particles in ambient air near a coniferous forest fire in Boulder, Colorado were identified as molecular markers of wood burning and forest fires. Particle samples were collected by filtering small volumes of air. The samples were analysed using thermal desorption followed by gas chromatographic separation and detection, a highly sensitive analytical method. Several compounds unique to softwood combustion were identified in the samples. Additionally, a predominance of odd-carbon-numbered n-alkanes over the corresponding even-carbon-numbered n-alkanes was observed. This predominance is a well-documented molecular pattern indicative of epicutical waxes in plants. 相似文献