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991.
The effect of uncertainty on the cost-effectiveness of alternative chains of stand establishment in northern Finland was examined.
The data were from a reforestation study of Scots pine (Pinus sylvestris L.) consisting of 288 sample plots, which were measured with respect to regeneration success. The study design included four
site-preparation methods (patch scarification, ploughing, prescribed burning and disk trenching) combined with three reforestation
methods (sowing, planting with containerized seedlings and planting with bare-rooted transplants). Initial reforestation density
was 2,500 spots or seedlings per hectare, and the regeneration success was modeled as probability with two thresholds, namely
500 and 1,100 saplings. On formerly spruce-dominated as well as pine-dominated sites the most cost-effective chain was ploughing
and planting with containerized seedlings, when threshold was 1,100 saplings per hectare. However, with threshold of 500 saplings
the best performer was ploughing and direct sowing on both sites. 相似文献
992.
Lloyd C. Irland 《European Journal of Forest Research》2010,129(5):777-786
The UN’s Millennium Development Goals (MDGs) and other regional and national policy commitments have motivated an upsurge
of interest in concepts and practical methods for monitoring forest conditions and trends at very wide geographic scales.
Two approaches to sustainability assessment at a global level are reviewed here. One consists of monitoring change in forest
conditions over time—the so-called Criteria and Indicators (C&I) approach. Another approach compares nations at a given point
in time. An example is the Yale Environmental Performance Index (EPI). Both approaches yield insights. It is widely recognized,
though, that severe data weaknesses afflict forest information over much of the world. These weaknesses include weak or absent
information on wood consumption in many regions, poor area estimates, and weak or absent information on key ecological conditions
in forests. The purpose of this essay is to introduce these efforts at global assessment, and to argue that an entirely new
discipline is needed to supply the information needed. The focus of this new discipline would be to design an ecologically
based set of definitions for forest and related ecosystems, and then to build and implement the optimum combination of satellite
measurements, air photo interpretation, and field plot measurements needed to measure world forest resource conditions and
trends. Examples of this new approach are already appearing. This argument is addressed to members of the global forest policy
community concerned with assessment, and to scientists, technologists, and managers in the many technical fields already engaged
on one or another aspect of measuring and monitoring forest conditions at a national and regional scale. 相似文献
993.
994.
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996.
Pascale Affolter Ulf Büntgen Jan Esper Andreas Rigling Pascale Weber Jürg Luterbacher David Frank 《European Journal of Forest Research》2010,129(3):289-298
Tree rings from the Alpine area have been widely used to reconstruct variations in summer temperature. In contrast, estimates
of changes in the hydrological cycle are rather scarce. In order to detect altitudinal and species-specific patterns of growth
responses to anomalous dry and wet conditions, a large network of 53 tree-ring width site chronologies along the Rhone valley
(Valais, Switzerland) covering the 1751–2005 period was compiled and analyzed. A total of 1,605 measurement series from four
conifer species—pine, larch, spruce, fir—were detrended to allow inter-annual to multi-decadal scale variability to be preserved.
Site chronologies were combined to four altitudinal (colline: <800 m asl, sub-montane: 800–1,000 m asl, montane: 1,000–1,450 m
asl, sub-alpine: >1,450 m asl) and species-specific mean time-series. These records were compared with temperature, precipitation,
and drought (scPDSI) data. Among the altitudinal records, the colline chronologies showed highest correlation with June precipitation
and scPDSI (0.5 and 0.7). Altitudinal effects, via control on climatic conditions, were superimposed upon species-specific
characteristics in affecting tree growth and response to moisture variations. In particular, species-specific differences
affected the significance level of drought response, with decreasing drought sensitivity towards higher elevations. Growth
conditions were found to be optimal at ~1,300 m asl, with precipitation/drought limiting tree growth below and temperature
above. Common years of extreme drought and low growth for the colline sites occurred in 1921, 1944, 1976, 1992, and 1998.
Our results demonstrate the potential of lower elevation conifers for reconstructing long-term changes in Alpine hydro-climate. 相似文献
997.
Sustainable development and sustainable forestry: analogies,differences, and the role of flexibility 总被引:1,自引:1,他引:1
Various approaches have been developed to achieve sustainability in forestry, under changing social needs and, consequently,
changing definitions of sustainability. This has led to the confusing situation in which various groups have different understandings
of the meaning of ‘sustainability’. Likewise, the concepts utilized to achieve sustainability, often with a poorly defined
objective, are sometimes not clear and/or inconsistent as a systematic overview regarding definitions and concepts is lacking.
Based on a literature review, this paper discusses related terms such as sustainability, sustained yield management, sustainable
forestry, sustainable forest management and sustainable development: their history, concepts and relationships, from a European
perspective. Finally, flexibility is proposed as a solution to overcome the identified shortcomings at all scales, while focussing
on the enterprise level. The origin of the sustainability concept in forestry was first driven by forest experts, while participatory
elements have been considered since the more recent idea of sustainable development. Since then, much effort has been made
to achieve intragenerational fairness by creating an improved participatory process. Concurrently, the original idea of sustainable
forestry as long-term and future-oriented management, considering future generations’ needs fell behind. An increasing standing
timber volume in Europe and the discussion on climate change brought new interest in how to cope with risks in the context
of pervasive future uncertainties within the scope of promoting sustainable development. Although the consideration of risk
has been concentrated on as a topic in forest science in recent years, studies have mainly focused on the enhancement of forest
resistance against disturbances. However, precaution and risk avoidance alone are probably insufficient to achieve an improved
sustainable development that focuses on intergenerational fairness, as these more defensive approaches may disregard important
management opportunities involved with an uncertain future. A perhaps more promising approach, the idea of future options
and the ability to respond to changing social and biophysical circumstances (i.e. flexibility) as criteria for sustainable
development have only shown a shadowy existence up to now. To further develop the consistency of sustainability concepts,
a shift of sustainability approaches from continuity towards flexibility options is proposed. 相似文献
998.
中国与“一带一路”国家木质家具贸易现状及趋势 总被引:1,自引:0,他引:1
鉴于地理距离和区域消费习惯对家具贸易影响程度较大,文中按照地理位置差异将“一带一路”地区分为6大板块,利用世界贸易中心(ITC)数据库2013—2017年中国与“一带一路”国家木质家具贸易数据进行分析发现:中国与“一带一路”国家木质家具贸易总额不断增长,贸易顺差较大,进出口市场分布不均,出口产品种类相对集中,进口产品较分散;为提高我国木质家具在“一带一路”国家的竞争力提出如下建议:制定战略规划以支撑国家“一带一路”倡议,优化产品设计以满足差异化需求,依托大型基础建设项目推进木质家具生产与销售,以高科技赋能家具产业和产品,重视木质家具产品的设计保护,加强政府政策引导。 相似文献
999.
在酸性土壤中,铝对林木的毒害是限制林木生长、降低林木生产力、进而导致森林退化的主要因素之一。目前,国内外在林木铝毒害及耐铝机制方面已有较多的研究,但关于林木耐铝的生理和分子机制的综述性报道很少。文中综述了近年来林木对铝的富集、铝对林木生理和分子水平上的毒害等方面的研究进展,总结了林木耐铝的生理机制和分子机制,简要介绍了外源添加物对林木耐铝毒的调控机制,提出了今后有关林木铝毒需进一步研究的重点,以期为林木铝毒的深入研究提供参考以及为缓解我国酸性土壤林木铝毒害及森林的健康持续经营提供参考。 相似文献
1000.
对淬火前的热挤压棒用不同的冷拉拔量进行拉拔,结果表明;冷拉拔量对棒材的组织和性能有不同的影响.当变形量达到10%时,经淬火后的棒材其组织是均匀的细晶组织. 相似文献