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农田烟粉虱寄主植物调查初报   总被引:12,自引:2,他引:10  
2001~2002年通过调查福州、漳州农田烟粉虱寄主范围,记录农田烟粉虱寄主植物17科62种(变种).其中豆科7种、茄科6种、十字花科8种、葫芦科9种、菊科10种、苋科4种、藜科4种、旋花科2种、锦葵科2种、、大戟科2种、柳叶草科2种、蓼科1种、玄参科1种、番杏科1种、大麻科1种、免丝子科1种、伞形花科1种。农田烟粉虱寄主植物主要以蔬菜作物和农田阔叶杂草为主。  相似文献
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农田氧化亚氮排放系数的研究   总被引:11,自引:1,他引:10       下载免费PDF全文
通过调研多年来国内外农田N2O排放的研究结果,建立了农田N2O年度排放数据库,并分析了N2O排放与各环境因子之间的关系.相关分析表明, N2O排放与温度及降水呈显著正相关,与土壤pH值、有机碳及氮含量无显著相关.依据政府间气候变化专门委员会对农田N2O排放系数的定义和确定方法,用年平均气温及降水量对其进行修正.结果表明,经平均气温修正后的排放系数并不减小农田N2O排放的估计误差,但用年降水量进行修正后能减小平均相对误差16%左右.  相似文献
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Linear models for field trials, smoothing and cross-validation   总被引:1,自引:0,他引:1  
GREEN  PETER J. 《Biometrika》1985,72(3):527-537
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First-order intrinsic autoregressions and the de Wijs process   总被引:1,自引:0,他引:1  
Besag  Julian; Mondal  Debashis 《Biometrika》2005,92(4):909-920
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20 0 2年 4月至 2 0 0 3年 4月利用直接观察法对匈牙利平原农田环境中狍的集群行为进行了研究 ,结果显示平均群体数量在寒冷的秋冬季节较大 ,最大群体数量也具有类似的变动趋势 ,2 0 0 3年 2月最大群体有 92 - 94只 ,并保持集群长达 2 0d ,在冷季以大于 5只的群体所占百分比较高。 2 0 0 2年 4月和 2 0 0 3年 3月集群开始解散 ,雄性个体在 2 0 0 2年 6、 7月的交配期独居或保持家庭小群 ,雌性主要与幼体构成家庭群。生活在小片林地的群体数量小于农田群体 ,作者认为农田平原环境的开阔性结构和繁殖生理状态是导致狍群体较大和集群行为变化的近因  相似文献
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To evaluate the effect of human activities on the amount of nitrogen (N) transported to the Three Gorges Dam (TGD), we have developed and applied a model to estimate the riverine N transport from watersheds draining into the upper Changjiang River basin. By using this model and a database of agricultural statistics, we study the temporal and spatial changes in N inputs to watersheds and surface waters. The total amount of N transported to the surface drainage waters from the agro-ecosystem in 2000 showed a 2.9-fold increase over that in 1980. Considering a constant (37%) loss rate from the river, the annual amount of N transported to the TGD from the agro-ecosystem of the Changjiang river upper basin was about 0.35 × 106, 0.47 × 106, 0.59 × 106, 0.64 × 106 and 1.01 × 106 t in 1980, 1985, 1990, 1995, and 2000, respectively. Further, the transported amount of new anthropogenic reactive N approximately quadrupled in 2000, while the amount of riverine N due to rural human waste varied slightly. Of the total N transported to surface drainage waters in 10 watersheds in 2000, the Jialingjiang watershed accounted for 35%; the TGD region, 15%; and the Toujiang, Wujiang and Minjiang watersheds, 11% each. In 1980, the N sources were concentrated in the rural areas surrounding Chendu City and Chongqing City; however, these sources considerably expanded in the 1990s. The increased use of synthetic fertilizers and the decrease in the fertilizer N-use efficiency are implicated as major causal factors of increased riverine N transport; the calculated amount of N transported to the main tributaries agrees well with previously reported data.  相似文献
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Summary The K/Ca ratios of six dominant perennial herbs on two abandoned agricultural fields in souther Ontario, Canada, were determined for June and September. Differential uptake of potassium and calcium conformed to root cation exchange theory, suggesting at least one possible mechanism influencing interspecific variability in mineral element composition of successional plants. K/Ca ratios were generally lowest for the legume, highest for the three gramineous species, and intermediate for the two dicotyledonous forbs.  相似文献
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