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151.
Does kriging predict weed distributions accurately enough for site‐specific weed control? 总被引:1,自引:0,他引:1
Numerous studies have demonstrated the patchy distribution of weeds within fields. The majority of these studies have used discrete sampling, recording weed densities at the intersections of regular grids. In this study, Avena spp. seedlings were recorded on square grids at four sites. The data were then divided into test and real data sets using the whole, two-thirds and one-half of the data to evaluate the consistency of global variogram models and accuracy of ordinary kriging estimates. Kriging provided poor weed density estimates at both very low and high densities, i.e. data were smoothed when compared with true values. Grid sampling took considerable time and, therefore, money to complete, whereas continuous sampling with multispectral imagery (performed at one site) was much quicker and at a finer resolution. It is suggested that sampling systems that collect continuous rather than discrete data are currently more appropriate for site-specific weed management. 相似文献
152.
油松毛虫卵(块)和蛹种群简单随机抽样最适样方大小的确定方法 总被引:1,自引:0,他引:1
在种群空间格局的研究的基础上,采用7种方法对同松毛虫卵(块)和蛹种群简单随机抽样技术中最适样方大小的确定问题进行了研究,结果表明,无论是卵(块)抑或蛹种群,都是在u=1时抽样误差最低,即以单株油松为样方时最为适宜,此外,文中还列出了考虑抽样花费时确定最适样方式大小的各种方法,并讨论了有关问题。 相似文献
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154.
大螟蔗田枯心苗的空间分布型及抽样技术研究 总被引:2,自引:0,他引:2
为了确定大螟蔗田枯心苗的空间分布型与抽样技术,采用聚集度指标法、Iwao回归分析法和Taylor幂法则分析了甘蔗枯心苗的空间分布型,根据Iwao的理论抽样数模型确定了蔗田枯心苗的最适理论抽样数。甘蔗枯心苗的空间分布呈聚集分布,基本成分是个体群,个体间相互吸引,个体群在蔗田呈聚集分布。聚集程度随密度的升高而增加,聚集原因可能是由于甘蔗自身特性和大螟为害等环境因子作用或其中一个原因引起的。5种抽样方法均可用于蔗田抽样调查。用Iwao的理论抽样数模型计算出蔗田枯心苗的理论抽样数模型为:D=0.1时,n=230.470 0/m+0.980 0,D=0.2时,n=57.617 5/m+0.245 0,D=0.3时,n=25.607 8/m+0.108(m为枯心苗平均密度)。本文为开展大螟测报和防治提供了理论依据。 相似文献
155.
为准确评估浙江省森林植被生物量,以2009年浙江省森林资源连续清查第一手野外调查数据为数据源,以样地为评估基本单元,采用单株生物量模型法(乔木,毛竹Phyllostachys edulis,杂竹,下木和灌木),单位面积生物量模型法(草本)和单位面积生物量法(矮化乔木林、灌木经济林),测算了样地水平的森林植被生物量.在此基础上,运用系统抽样统计方法,将样地水平微观数据转换到全省宏观尺度,评估了全省总体的森林植被生物量,提供了主要评估结果的估计精度和估计区间.结果显示:2009年,浙江省森林植被总生物量为37 010.732×104t.主要森林植被类型中,乔木林群落为29 096.269×104t,竹林群落3 762.964×104t,灌木林群落1 747.953×104t.在P<0.05的可靠性保证下,森林植被总生物量估计精度为96.64%,估计区间为35 767.171×104~38 254.293×104t;乔木林群落9558%,估计区间为27 810.214×104~30 382324×1 04t;竹林群落89.13%,估计区间为3 353.930×104~4 171.998×104t;灌木林群落90.00%,估计区间为1 573.158×104~1 922.748×104t.可见,采用以上方法测算的浙江省各类森林植被生物量评估结果,均有很高的精度保证和较好可信度. 相似文献
156.
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158.
Mirkena T Duguma G Willam A Wurzinger M Haile A Rischkowsky B Okeyo AM Tibbo M Solkner J 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2012,129(3):244-253
Based on the results of participatory approaches to define traits in the breeding objectives, four scenarios of ram selection and ram use were compared via deterministic modelling of breeding plans for community-based sheep breeding programmes in four diverse agro-ecological regions of Ethiopia. The regions (and production systems) were Afar (pastoral/agro-pastoral), Bonga and Horro (both mixed crop-livestock) and Menz (sheep-barley). The schemes or scenarios differed in terms of selection intensity and duration of ram use. The predicted genetic gains per year in yearling weight (kilograms) were comparable across the schemes but differed among the breeds and ranged from 0.399 to 0.440 in Afar, 0.813 to 0.894 in Bonga, 0.850 to 0.940 in Horro, and 0.616 to 0.699 in Menz. The genetic gains per year in number of lambs born per ewe bred ranged from 0.009 to 0.010 in both Bonga and Horro. The predicted genetic gain in the proportion of lambs weaned per ewe joined was nearly comparable in all breeds ranging from 0.008 to 0.011. The genetic gain per year in milk yield of Afar breed was in the order of 0.018 to 0.020 kg, while the genetic gain per generation for greasy fleece weight (kg) ranged from 0.016 to 0.024 in Menz. Generally, strong selection and shorter duration of ram use for breeding were the preferred options. The expected genetic gains are satisfactory but largely rely on accurate and continuous pedigree and performance recording. 相似文献
159.
《Scandinavian Journal of Forest Research》2012,27(1-4):545-567
Satellite data were used in developing methods for forest inventory and mapping in a cooperation project involving Finland, Norway and Sweden. A goal was to improve the technical competence in forestry remote sensing in those countries. Landsat TM‐ and simulated SPOT‐imageries were classified using, e.g., filtered input data and contextual classifiers. The relative area distribution of usual forest classes was estimated at an acceptable accuracy. A two‐phase sampling scheme was introduced for compartmentwise (in‐place) inventories. The first phase involves analysis of satellite data, the second phase measurement of field plots. Correlations between satellite‐ and field‐measured values of various forest characteristics were relatively high, close to those obtained using aerial photo interpretation. 相似文献
160.
不同取样尺度农田土壤速效养分空间变异特征初步研究 总被引:14,自引:1,他引:13
以3种取样间距(100m、50m、25m)进行网格取样,对土壤速效养分的空间变异性进行研究。结果表明:取样间距对土壤速效养分的含量水平、变异系数影响不显著;取样间距对合理取样数目具有一定的影响,合理取样数目分别为:碱解氮(71)、速效磷(36)、速效钾(18)。土壤速效养分的空间变异性主要受结构因素影响,但碱解氮与速效磷受随机因素影响强于速效钾。利用Kriging内插法绘制了不同取样间距土壤速效养分的等值线图。 相似文献