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961.
962.
RICHARD D. BRODEUR ELIZABETH A. DALY ROBERT A. SCHABETSBERGER KATHRYN L. MIER 《Fisheries Oceanography》2007,16(5):395-408
The feeding habits of juvenile coho salmon, Oncorhynchus kisutch, in the northern California Current were examined using samples from two different time periods (1980–85 and 1998–2003) of highly contrasting oceanographic conditions. The goal was to test the influence of interannual and interdecadal changes in taxonomic composition of prey, feeding intensity, and size spectra of teleost prey. Analyses were done for samples taken both early in the summer (June) shortly after the salmon enter the ocean, and also in late summer (September) following some ocean residency. Fish prey dominated coho salmon diets by weight during most years, but this trend was more pronounced during the 1980–85 sampling period. In terms of numerical composition, the diets were more variable on an interannual basis, but decapod larvae and euphausiids were important prey in most years. Pteropods and copepods were important prey during weak upwelling or El Niño years, whereas euphausiids were important during strong upwelling or otherwise highly productive years. Hyperiid amphipods comprised a substantial proportion of the diets only in 2000. Coho salmon showed highly significant differences in prey composition among years or between decades both in weight and numerical composition. The percentage of empty stomachs was highly variable by year in both June and September, but was significantly different only for September between decades. In contrast, an index of feeding intensity did not show many significant changes in either comparison. However, the relative size ratios for fish prey consumed were highly variable by year, and larger than average fish prey were consumed during 1998, leading to the highest feeding intensity observed. 相似文献
963.
基层农机工作要适应时代的需要,其管理职能也要随之做出相应调整,由过去的管理型向管理服务型转变.既要管理好农机安全生产及农机有序合理流动,又要搞好服务,当好农机教练员,做好农机推广工作,成为一名合格农机服务员,主动为机手和经销商及厂家搭起桥梁和纽带,促进农机的发展. 相似文献
964.
运用文献资料法、运动学测试法、对比分析法,对两组(14名)不同水平的跳远运动员起跳腿各关节工作性质及能力进行对比研究,并对起跳阶段运动员身体重心运动(时间、速度、空间)特征进行分析。研究显示:跳远起跳阶段髋关节工作为先等长收缩再离心收缩,不是缓冲外界负荷的主要关节;不同水平运动员膝、踝关节缓冲、蹬伸工作能力呈显著性差异,踝关节对提高重心垂直速度的贡献不显著;运动员水平越高蹬伸时间指数、水平速度转变率越高,重心轨迹曲线越平滑。 相似文献
965.
《Communications in Soil Science and Plant Analysis》2012,43(12):1463-1477
Applicability of various chemical extracts was investigated as quantity (Q) factors to determine cadmium (Cd), zinc (Zn), and copper (Cu) desorption quantity–intensity (Q/I) relationships in soils. The metal extracts were sums of sequential metal fractions (except the residual fraction) using Tessier's (TSE) and Community Bureau of Reference (BCR) procedures and various single chemical extracts: 1.0 M potassium nitrate (KNO3), 1.0 M magnesium nitrate [Mg(NO3)2], 1.0 M magnesium chloride (MgCl2), and 0.11 M acetic acid (CH3COOH) solutions. Water-extractable metal was applied as a fixed intensity (I) factor. The TSE or BCR metal fractions were significantly correlated with diethylenetriaminepentaacetic acid (DTPA)–extractable metals, and all the metal desorption Q/I curves were linearly fitted. However, most of metal BC values estimated by using the single chemical extracts were very low and did not have consistent trends for target metals. Only 0.11 M CH3COOH-extractable metals might be reliable. Therefore, TSE and BCR metal fractions can be applicable to replace DTPA-extractable metals, and 0.11 M CH3COOH-extractable metals might also be useful. 相似文献
966.
刘敏娟 《农业图书情报学刊》2009,21(4):210-212
从网络环境对文献资源建设工作带来的影响出发,探讨了文献资源工作者适应新时期发展的需要进行继续教育的必要性、工作人员应具备的素质以及继续教育的途径等问题。 相似文献
967.
提升读者的服务功能拓展高校图书馆采编工作 总被引:1,自引:0,他引:1
韩葆青 《农业图书情报学刊》2009,21(9):232-234
针对高校图书馆的发展趋势和采编工作的现状,提出了拓展采编工作、更新服务内容的新想法。 相似文献
968.
《Plant Production Science》2013,16(4):522-528
AbstractThe contents of major nutrient components, and the composition and contents of medicinal substances were examined in Houttuynia cordata cultivated under field conditions and treated with natural light at full intensity, 40% intensity, and 20% intensity from sprouting to harvesting. The results indicated that the yield of the aboveground portion per unit area was highest at a 40% intensity and lowest at 20% intensity. The yield of the underground portion per unit area was highest under full intensity and lowest at a 20% intensity. As light intensity was reduced, protein and water content increased, while the contents of soluble sugar and fat, the contents of volatile oils both the aboveground and underground portion decreased. The total flavonoid content in both the aboveground and underground portions decreased with diminishing light intensity, but the composition of these flavonoids was hardly affected. In summary, although proper shading can increase the yield and the contents of some nutrients in H. cordata, this treatment reduces the net contents of medicinal components such as volatile oils and flavonoids, as well as the contents of active components. Therefore, it is necessary to provide sufficient light when growing H. cordata for medicinal and functional food purposes, but the crop may be treated with appropriate shading or intercropped when grown as food. 相似文献
969.
东方之星-LSC2204Q-11捞砂车是采用铰接式轮式拖拉机底盘改制而成的,具有作业灵活,转移方便,越野性能好,行驶和工作挡位多等特点,很好地满足了油田作业需求。 相似文献
970.
几种生态因子对银纹夜蛾实验种群的影响 总被引:2,自引:0,他引:2
本文以主要质量指标对比了用人工半合成饲料与天然饲料饲养银纹夜蛾的结果,表明人工半合成饲料明显优于天然饲料。研究了幼虫饲养密度对存活的影响,四龄末幼虫存活率与一龄幼虫密度呈抛物线关系,化蛹率、蛹重与五幼虫密度呈直线下降关系,相对湿度、夜间光照强度、食物等对成虫生殖有显著影响。 相似文献