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111.
D. J. Pannell 《Agroforestry Systems》1999,45(1-3):395-411
The fundamental challenge in developing a new farming system is to have it adopted and maintained by farmers. The difficulty
of achieving widespread adoption is increased if the new farming system is complex and/or radically different to current farming
practice. This paper is a review of these issues with a focus on farming systems based on mimicry of natural ecosystems. It
is proposed that there are four conditions which are necessary for an individual farmer to adopt an innovative farming-system:
awareness of the innovation, perception that it is feasible to trial the innovation, perception that the innovation is worth
trialing, and perception that the innovation promotes the farmer's objectives. Challenges involved in meeting each of these
conditions are discussed. It is concluded that the most important challenges in developed countries are: (a) developing a
farming system that is in fact more profitable than current practice; (b) assessing whether a system is in fact more profitable
than current practice; and (c) overcoming the problem of deep uncertainty about the technology. In developing countries one
must add the additional challenges of (d) high interest rates/high discount rates; and (e) insecure or inequitable land tenure.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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生态农业建设的发展迫切需要制定出1套测定其技术进步率的方法。根据生态农业特点,对生态农业技术进步率测定方法进行了研究,提出了生态农业技术进步率测定方法。 相似文献
115.
Elizabeth A Fulton Anthony D M Smith David C Smith Ingrid E van Putten 《Fish and Fisheries》2011,12(1):2-17
There is broad consensus that the main problem facing fisheries globally is too many boats chasing too few fish. Unfortunately it is also possible to argue that there are too many proposed solutions and not enough practical answers to improving fisheries management. There is a deepening divide between those who propose alternative regulatory controls on fishers, including establishing large areas permanently closed to fishing, and those who argue for better alignment of incentives combined with broad participation of resource users in fishery management decisions (in simple terms, between top down and bottom up systems of governance). However despite the choice of policy instruments used, a consistent outcome is that resource users behave in a manner that is often unintended by the designers of the management system. Hence whilst uncertainty is broadly recognized as a pervasive feature of fisheries management, to date most of the attention has focussed on only part of that uncertainty – scientific uncertainty about the status of exploited resources. The effect of uncertainty generated on the human side of fisheries science and management has received much less attention. However, the uncertainty generated by unexpected resource user behaviour is critical as it has unplanned consequences and leads to unintended management outcomes. Using empirical evidence of unexpected resource user behaviour and reviewing current responses to unexpected management outcomes, we identify different approaches that both improve prediction of human behaviour in fisheries systems and identify management measures that are more robust to these sources of uncertainty. However, unless the micro scale drivers of human behaviour that contribute to macro scale implementation uncertainty are communicated effectively to managers and considered more regularly and in greater depth, unanticipated responses to management actions will continue to undermine management systems and threaten the sustainability of fisheries. 相似文献
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全国多环芳烃年排放量估算 总被引:17,自引:3,他引:14
根据排放因子和相关排放活动的统计资料,估算了USEPA优先污染物清单中16种PAHs的全国年排放量。结果表明,1999年16种PAHs排放总量约为9799t,其中7种致癌性PAHs排放总量约2000t。主要排放源为家庭燃煤和炼焦,两者分别占总排放量的66.6%和30.6%。在75%置信区间上,估算结果的不确定性大致为正负一个数量级。PAHs排放谱中荧蒽、蒽、芘以及高环化合物比例显著高于北美大湖地区。 相似文献
118.
J. Brian Hardaker 《Agricultural Systems》2010,103(6):345-350
The notion that we can rationalize risky choice in terms of expected utility appears to be widely if not universally accepted in the agricultural and resource economics profession. While there have been many attempts to assess the risk preferences of farmers, there are few studies of their beliefs about uncertain events encoded as probabilities. We may attribute this neglect to scepticism in the profession about the concept of subjective probability. The general unwillingness to embrace this theory and its associated methods has all too often caused researchers to focus on problems for which frequency data are available, rather than on problems that are more important where data are generally sparse or lacking. In response, we provide a brief reminder of the merits of the subjectivist approach and extract some priorities for future research should there be a change of heart among at least some of the profession. 相似文献
119.
为揭示滨海滩涂地区土壤盐分三维空间分布特点并提供相关技术方法与思路,以苏北海涂围垦区典型地块为例,综合采用三维克里格和随机模拟方法对土体盐分含量的三维空间分布进行估值、模拟与对比分析,并对土体盐分三维分布的空间不确定性进行评价。结果显示,由克里格法得到的土壤盐分空间分布具有明显平滑效应,减小了数据间的空间差异并改变了数据的空间结构;序贯高斯模拟结果整体分布相对离散,突出了原始数据分布的波动性;研究区土壤盐分随深度增加而升高,存在一定次生盐渍化风险;围垦后研究区土壤盐渍化的发生概率已有所降低,轻度盐化土和中 相似文献
120.
为提高检验结果的准确性,确定检验过程中的关键影响因素,对液相色谱法测定氟尼辛葡甲胺注射液含量进行不确定度评估。依据《中国兽药典》2020 版氟尼辛葡甲胺注射液质量标准对其含量进行测定,分析影响不确定度的因素,参照 JJF 1135 - 2005《化学分析测量不确定度评定》和JJF 1059.1-2012《测量不确定度评定与表示》中的规定及要求,对检验过程中的不确定因素进行评估,根据CNAS-GL006:2019 构建了氟尼辛含量的不确定度评估数学模型,对检测过程中各种不确定度的来源进行分析,并计算合成相对标准不确定度和扩展不确定度?氟尼辛葡甲胺注射液含量的不确定度结果表示为(102.2 ± 2.72)% ,(k = 2,置信区间为 95% ),主要来源于仪器重复性? 相似文献