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61.
62.
在对安徽省岳西、金寨、责池等11个县(市、区)1991—1992年马尾松飞播造林播区,开展飞播当年出苗调查和飞播3a后成效调查的基础上,通过收集飞播造林当年至成效调查前气象实况数据,就飞播造林成效与气象因子进行逐步回归分析,找出影响飞播造林成效的主导因子,并进行了进一步分析。 相似文献
63.
通过1980~1987年秋季在大连老铁山、山东省长岛县大黑山岛及青岛浮山的观察研究,确认猛禽的迁徙与气候、天气有着密切的关系。猛禽迁徙通常选择在风力三级(14 km/h)以上西北风或南风的有利天气条件下顺风或侧顺风迁徒。这种大气环流形势在天气图上的反映是地面冷锋过境后当天或次日。冷锋过境前的天气特征是偏南风或西南风,气温升高,冷锋过境后风向转为西或西北风,同时气温下降,气压升高,风速加大。5~6级西北风(30~40 km/h)天气会出现猛禽大规模迁徙过境。故在猛禽的研究中,可根据这种天气变化模式进行猛禽迁徙的预报。 相似文献
64.
在小麦收获时期,若遇到天气变化,小麦可收获时间窗会发生改变,若还按原调度方案,将造成大量农田延迟收获,从而给农户带来损失。为避免或降低因天气变化给农户带来损失,本文考虑天气变化导致的农田收获时间窗变动的应急调度问题。基于天气变化导致的农田可作业时间窗实际缩短的情况,综合考虑收获机转移时间、提前到达等待时间和延迟时间,建立因天气变化导致的时间窗变动的收获机多目标应急调度模型,引入农田收获应急度函数,确定应急农田,将可作业时间窗和下雨时间有交集的农田重新根据应急度排序进行优先调度。针对此模型特点对遗传算法进行改进,设计基于改进遗传算法的收获机应急调度算法,采用两级多段编码方式及单点交叉方式,使算法可以有效避免局部最优,能够很好地实现全局收敛。通过动态改变原收获机收获路线,为应急农田优先提供收获服务,从而提高农机合作社服务能力,减少农户损失。实例仿真结果证明了模型和算法的可行性。 相似文献
65.
《国际水土保持研究(英文)》2022,10(3):355-370
Rainfall is the main cause of erosion of Brazilian soils, which makes assessing the rainfall erosivity factor (RE) and the erosivity density (ED) fundamental for soil and water conservation. Therefore, the objectives of this study were: i) to estimate the RE and ED for São Paulo State, Brazil, using synthetic series of pluviographic data; ii) to define homogeneous regions regarding rainfall erosivity; and iii) to generate regression models for rainfall erosivity estimates in each of the homogeneous regions. Synthetic series of pluviographic data were initially obtained on a sub-daily scale from the daily rainfall records of 696 rainfall gauges. The RE values were then estimated from the synthetic rainfall data, and ED was calculated from the relationship between erosivity and rainfall amounts. Monthly and annual maps for RE and ED were obtained. Hierarchical clustering analysis was used to define homogeneous regions in terms of rainfall erosivity, and regionalized regression models for estimating RE were generated. The results demonstrate high spatial variability of RE in São Paulo, where the highest annual values were observed in the coastal region. December to March concentrate approximately 60% of the intra-annual erosivity. The highest values of annual ED were observed in regions with intense agricultural activity. The definition of five homogeneous regions concerning the rainfall erosive potential evidenced distinct seasonal patterns of the spatial distribution of erosivity. Finally, the high predictive accuracy of the regionalized models obtained characterizes them as essential tools for reliable estimates of rainfall erosivity, and contribute to better soil conservation planning. 相似文献
66.
对雾霾的定义、雾霾的区别与联系以及雾霾天气形成的原因进行了阐述,并提出了减少雾霾天气的解决对策,为改善城市环境空气质量提供一定的参考依据。 相似文献
67.
根据本溪市区46年气象资料的统计分析,总结出了该地区雷暴天气气候规律和特征,并分析了该地区因雷暴天气灾害频发,造成农业诸多方面灾情,影响和破坏了粮食产量质量及农业基础设施;同时,提出利用雷暴天气规律和特征,指导农业生产活动,并提出防御对策。 相似文献
68.
69.
Probably the most known and best studied type of plant resistance to pathogenic infections is the hypersensitive response (HR), a form of localized programmed cell death associated with restriction or killing of pathogens that often leads to macroscopically visible localized tissue necrosis. It is generally assumed that cell death and resistance within the HR are physiologically and genetically linked. However, there has been considerable speculation about whether cell death is an absolute requirement for resistance conditioned by the HR. This review discusses the relation of cell death and resistance in the HR, in particular, the importance of cell death in this process. We intend to focus on the increasing amount of research evidence showing that in several plant-pathogen interactions, the two main components of the HR – resistance and cell death – can be physiologically, genetically and temporally uncoupled. In other words, HR should be considered as a combination of resistance and cell death responses, where cell death may be dispensable for plant disease resistance. The varying contribution of these two components (i.e. cell death and resistance) generates an array of defense strategies differing in efficiency. Thus, a very early and rapid defense response seems to contribute to the development of macroscopically symptomless (extreme) resistance, while a moderately early defense response results in resistance with the concomitant development of controlled and limited cell and tissue death (HR). Accordingly, a delayed and failed attempt by the host to elicit resistance responses would result in massively stressed plant tissues (e.g. “systemic HR”) and a partial or almost complete loss of control over pathogen invasion. The dynamic nature of resistance responses in plants implies that resistance can be effective with or without cell death but its outcome and efficiency may depend primarily on the timing and speed of the host response. 相似文献
70.
介绍了使用JDBC实现自动气象站分中心站的气象要素信息检索,程序运用B/S体系结构,遵循MVC设计思想,采用Model2模式进行开发,为了提高程序的运行速度,在数据库中创建了存储过程。 相似文献