全文获取类型
收费全文 | 278篇 |
免费 | 12篇 |
国内免费 | 16篇 |
专业分类
林业 | 16篇 |
农学 | 54篇 |
基础科学 | 1篇 |
19篇 | |
综合类 | 136篇 |
农作物 | 29篇 |
水产渔业 | 1篇 |
畜牧兽医 | 8篇 |
园艺 | 39篇 |
植物保护 | 3篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 18篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 23篇 |
2012年 | 17篇 |
2011年 | 31篇 |
2010年 | 14篇 |
2009年 | 30篇 |
2008年 | 12篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1990年 | 5篇 |
1987年 | 1篇 |
排序方式: 共有306条查询结果,搜索用时 0 毫秒
101.
102.
本文研究了高变性芝麻饼粕中含硒量、生物效能、溶解性、分布及存在形式等特性,并采用 D 型大柱凝胶电泳分析其可溶性蛋白硒络合分子量范围为21KD-30KD。 相似文献
103.
为探究Cu对铜排斥型经济植物黄花月见草生长和生理特性的影响,以铜积累型植物海州香薷和铜敏感植物芝麻为对照,通过水培试验研究了Cu(50μmol·L-1)胁迫对三种植物根系生长、根尖质膜完整性、叶片叶绿素含量、膜透性、渗透调节物质含量、有机酸含量、必需营养元素吸收的影响。结果表明:Cu胁迫下三种植物根系生长均受到显著抑制,但黄花月见草和海州香薷的根尖质膜完整性较好,而芝麻的根尖质膜完整性受到严重伤害;Cu胁迫导致芝麻叶片细胞膜透性增加了130%、叶绿素含量相对于对照降低了6.9%,但对黄花月见草和海州香薷叶片膜透性、叶绿素含量没有影响。Cu胁迫下,三种植物体内苹果酸含量均显著增加;海州香薷和芝麻叶片中脯氨酸含量分别上升了37%和73%,而黄花月见草叶片脯氨酸含量变化不大。三种植物体内Cu积累与Zn、Fe、Mn的积累呈显著正相关,与Ca、K积累呈负相关。此外,通过盆栽试验发现,土壤中总铜含量不高于700 mg Cu·kg-1土对黄花月见草种子千粒重、种子油含量、油中γ-亚麻酸含量均没有显著影响,且种子铜含量符合国家食品卫生标准(GBT 5009.13—2003)。低廉的生产成本和较高的经济效益使得黄花月见草在合理利用Cu污染土壤中具有推广价值。 相似文献
104.
Kurt Möller Johann Habermeyer Volker Zinkernagel Hans-Jürgen Reents 《Potato Research》2006,49(4):281-301
For organic potato producers, the two main challenges are disease and nutrient management. Both are limited by regulations
that on the one hand prohibit the use of chemical fertilizers, especially nitrogen, and on the other hand prohibit most synthetic
pesticides. Late blight caused by Phytophthora infestans is commonly thought to be the most yield-reducing factor. However, because there is no really effective fungicide available
to control late blight, there are virtually no yield loss data available for organic farming conditions. In this paper, the
state of the art of organic potato tuber growth under on-farm conditions with respect to disease and nutrient management is
summarized by field trials and on-farm surveys on commercial organic crops carried out in the years 1995–1998. Soil nitrogen
(N) levels, plant N uptake, disease development of P. infestans and potato yield were measured. Results indicated that N availability was most important in limiting yields in organic potato
crops. From on-farm data, a model including disease development, growth duration of the crops until foliage decay and different
parameters related to N status of the crop could explain 73% of the observed variation in yield. Only 25% of this variation
in yield could be attributed to the influence of late blight. Differences in N availability explained 48%. In conclusion,
several points emerged from the results. In organic farming, yields are mainly limited by nutrient availability in spring
and early summer. The effects of late blight on yields may often be overestimated and cannot be deduced from results in conventional
farming because of the strong interaction with nutrient status. Depending on N availability, tubers stop growing between mid-July
(70–90 kg N ha−1 uptake), the end of July (110–140 kg N ha−1 uptake) and mid-August (140–180 kg N ha−1 uptake) due to N limitations. The higher the N status of a potato crop, the longer the growing period needed to achieve the
attainable yield and the higher the probability that late blight stops further tuber growth and becomes the key tuber-yield-limiting
factor. In the second part of this paper, the interactive effects of soil N availability and the impact of P. infestans on yield in the presence and absence of fungicides from 1996 to 1998 for mid-early main crops are reported. An empirical
schematic model of disease impact depending on N availability was developed. 相似文献
105.
Abstract White yam (Dioscorea rotundata cv. Olonko) was grown consecutively for three growing seasons, i.e. from February to October of 1975, 1976 and 1977, and treated with six levels of nitrogen, viz: 0, 40, 60, 120, 160 and 200 kg N/ha in the field. Leaf samples were taken at four stages of growth as follows: vegetative, tuber formation, tuber development and tuber maturation, and analyzed for NO3‐N, P, K, Ca and Mg. Increasing nitrogen fertilization consistently increased leaf‐NO3‐N, particularly at the vegetative stages of growth, while no consistent trend was established for leaf‐P. Leaf‐K was increased at low rate of nitrogen fertilization during tuber formation and maturation whereas leaf‐Ca increased only at tuber maturation in the presence of higher rates of nitrogen fertilization. There was a marked increase in leaf‐Mg at all stages of growth when N treatment was increased to 200 kg N/ha. A positive correlation (r = 0.84???) was obtained for leaf‐K at the vegetative growth stage with tuber yield, while leaf‐Mg was positively correlated with tuber yield at vegetative (r = 0.46?), tuber formation (r = 0.50?) and tuber development (r = 0.67??) stages. All other elements were negatively correlated with yield at all stages of growth. Tuber yield was highest at the 200 kg N/ha treatment. 相似文献
106.
V.S. Harikumar 《Archives of Agronomy and Soil Science》2013,59(3):347-359
The abundance and composition of arbuscular mycorrhizal fungi (AMF) are generally low under managed agroecosystems in comparison to natural ecosystems. The objective of the study was to determine the composition and species richness of AMF associated with sesame under traditional low-input cropping system in Kerala, India. Wide variability in root colonization by AMF as well as spore density in the rhizosphere existed in sesame. Correlation between frequency of colonization (F%) and spore density as well as between these variables and soil characteristics showed a negative relationship. The fungal variables were influenced by soil factors such as pH, soil organic carbon (OC) and available nutrients. Frequency of colonization was positively correlated (P < 0.01) with soil pH and potassium (K) and negatively correlated with OC, nitrogen (N) and phosphorus (P). AM spore density was positively correlated with OC, N and P and negatively correlated with pH and K. Ten taxa of AMF belonging to the genera Acaulospora, Diversispora, Funneliformis, Gigaspora, Glomus and Scutellospora were associated with sesame, with the predominance of Funneliformis and Acaulospora in both frequency and relative abundance over a wider soil nutrient range. Soil characteristics appear to have a profound influence on the composition and species richness of AMF under traditional low-input cropping systems. 相似文献
107.
[目的]确定脱毒甘薯[Ipomoea batatas(L)Lam.]育苗时适宜的种薯大小。[方法]设1个对照和13个处理,其中对照为混装(50-500g种薯占重量的85%,500-700g为15%),13个处理的种薯重量分别为50-100、101-150、151-200、201-250、251-300、301-350、351-400,401-450、451-500、501-550、551-600、601-650、651-700g。[结果]种薯大小对出苗数量和质量有一定影响。50-200g薯块出苗最多,较对照差异显著,50-100g薯块薯苗茎细且鲜重小,均与其他处理差异显著。200-300g薯块采苗数虽和对照差异不显著,但是与100-200g薯块采苗数量和质量相差不大。[结论]综合分析认为,对于脱毒忻薯2号,在生产上100-300g薯块作为种薯育苗比较适宜。 相似文献
108.
109.
芝麻资源群体结构及含油量关联分析 总被引:5,自引:1,他引:4
【目的】推测芝麻资源群体材料的遗传变异、群体结构和分子亲缘关系,通过关联分析检测群体中影响含油量表型的位点,为芝麻高油育种及开展其它性状关联分析等提供科学依据。【方法】利用20对SSR引物、43对SRAP引物及16对AFLP引物,对来自芝麻核心品的216份芝麻资源进行遗传多样性分析、群体结构分析和含油量性状关联分析。【结果】共检测到338个等位变异,群体遗传多样性为0.2493、多态性信息含量为0.2090。群体结构分析将216份芝麻资源分为2个亚群(POP1和POP2);其中,174份资源(80.56%)归属POP1亚群,42份资源(19.44%)归属POP2亚群。POP1亚群的遗传多样性(0.2180)、多态性信息指数(0.1840)等指标值都低于POP2亚群(分别为0.3190和0.2561),表明POP2亚群内种质遗传变异更为丰富。AMOVA分析表明,亚群内的遗传变异(86.83%)极显著高于亚群间的遗传变异(13.17%)(P<0.001)。关联分析重复检测出2年环境下与含油量性状极显著关联的分子标记8个(P<0.01)。这8个标记的性状变异解释率变幅为0.0343(标记M20E16-8)-0.0587(标记SSR12-2),总的变异解释率为0.2846(2008年)和0.3801(2009年)。【结论】以216份来自中国芝麻核心品的资源构成自然群体,群体结构简单、遗传变异较为丰富,可以用于开展芝麻重要目标性状的关联作图。应用关联分析方法在2个年度环境下重复检出8个标记与含油量性状极显著关联(P<0.01),这些标记可能与含油量性状存在稳定、可靠相关联。 相似文献
110.