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Markus Kautz Kai DworschakAxel Gruppe Reinhard Schopf 《Forest Ecology and Management》2011,262(4):598-608
Spatio-temporal dispersal of pest species such as bark beetles plays a key role in their population ecology and outbreak dynamics. Understanding the underlying patterns is crucial for applying appropriate management strategies.In contrast to most existing studies which focus on dispersing beetles, we analysed patches of killed trees resulting from bark beetle infestation. The study was based on a 22-year time series of annually captured colour-infrared (CIR) images of the Bavarian Forest National Park (Germany), where Ips typographus L. (Coleoptera, Curculionidae, Scolytinae) propagates undisturbed by human activity. Newly infested patches comprising at least 5 spruce trees were identified in every time step. This investigation of spatio-temporal spread of infestations primarily focused on (i) parameterizing the size and shape of infestation patches, (ii) modelling an infestation gradient and (iii) evaluating the risk of subsequent infestations on landscape scale. We developed a GIS-based distance ring approach to quantify the distance relation of subsequent infestations, including the distribution of potential hosts.Infestation spread was revealed to be strongly distance dependent, following an inverse power law function: on average 65% of new infestations occurred within a 100 m radius of the previous year’s infestations, and 95% within 500 m. ‘Distance’ proved to be a major determinant of I. typographus dispersal on the landscape scale in each time step of the 22-year series we investigated. Infestation distance thus describes the outcome of beetle dispersal very accurately. The time series showed two alternating periods of epidemic and non-epidemic infestation. These gradation stages did not affect the size and shape of infested patches, but epidemics correlated significantly with a higher percentage of infestations within short distances. Additionally, the resulting infestation risk is highly sensitive to the gradation stage, particularly within the first 100 m around source spots where it increases up to 30%.Our study therefore contributes to a better understanding of the outbreak dynamics of I. typographus and suggests concentrating efficient bark beetle management on areas in the close vicinity of previous years’ infestations. 相似文献
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在农业信息资源数据库的支持下,利用JSP软件开发技术,建立了农业与农村远程教育系统,该系统包括远程课堂,子系统、课件点播子系统、实用技术子系统、系统管理子系统等4个子系统。论文着重阐述系统的主要功能、系统的技术架构、主要数据库结构及关键技术,并对系统的进一步完善和应用作了探讨。 相似文献
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四川省开县山区农业气候资源的质量评价 总被引:2,自引:0,他引:2
在确定了山区农业气候资源质量综合评价原则的基础上,建立评价的指标体系和评价标准,进而提出综合指数、模糊判别、希尔伯特空间距离系数等3种评价方法.本文以四川省开县为例,给出了农业气候资源环境质量的定量评价结果,并对3种评价方法进行了讨论和比较. 相似文献
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聚类分析的基本思想是研究的样品或指标(变量)之间存在着的程度不同的相似性(亲疏关系),根据一批样的多个观测指标,具体找出一些能够度量样品或指标之间相似程度的统计量,以此为划分类型的依据,将一些相似程度较大的样品(或指标)聚合在同一类,而将关系疏远的聚合在不同的类,把不同的类型一一划出来,形成一个由小到大的分类系统。最后将整个分类系统绘制成一张聚类图(或称谱系图),并由聚类图进行分类。 相似文献
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农民是将农业科学技术转化为生产力的最终应用者,农村实用技术远程培训可以提高农民应用农业科学技术的效率。对闽南农村实用技术远程培训的现状及成效进行调研后,笔者叙述了农村实用技术远程培训对促进特色农业产业、无公害蔬菜产业、沼气技术产业发展,对促进新农村建设、农村劳动力转移、农民增收致富产生的显著作用,并分析了远程培训存在的亟待解决的问题,提出了采用多渠道弥补远程培训的不足之处,开展区域特色农业远程培训,分层次进行远程培训以满足不同文化水平农民的技术需求、开阔农民的视野、转变农民的观念的对策与建议。 相似文献
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Philip A. Stephens Candy A. d''Sa Claudio Sillero-Zubiri Nigel Leader-Williams 《Biological conservation》2001,100(3):307-322
Large mammals, both wild and domestic, were censused in four study areas in Bale Mountains National Park (BMNP), southern Ethiopia, from April until August 1997, using established road counts, horse-back counts and systematic transects, a new approach to censusing large mammals in BMNP. Data collected since 1983 were also examined to indicate trends in mammalian abundance. Civil unrest following the government changeover in 1991 disrupted management of BMNP, leading to an increase in human settlement and livestock densities. The effect of these factors on BMNP's wildlife is assessed and discussed. Most large mammalian wildlife has declined since 1983 but signs of recovery for some species in recent years are positive. The fates of two charismatic endemics are emphasised. BMNP's current population of mountain nyala (Tragelaphus buxtoni, an endangered antelope) was estimated to be between 1100 and 1300. This is lower than estimates for the late 1980s, but shows an increase from very low levels recorded following social turmoil during the government changeover in 1991. Data on the Ethiopian wolf (Canis simensis, a critically endangered canid) also indicate positive trends in abundance, following severe declines between 1989 and 1992 due to rabies epizootics. Action to reduce human utilisation of parts of BMNP is urgently required to prevent further degradation of the environment and to safeguard the future of both the mountain nyala and Ethiopian wolf. 相似文献