全文获取类型
收费全文 | 3949篇 |
免费 | 173篇 |
国内免费 | 205篇 |
专业分类
林业 | 898篇 |
农学 | 254篇 |
基础科学 | 38篇 |
499篇 | |
综合类 | 1752篇 |
农作物 | 172篇 |
水产渔业 | 152篇 |
畜牧兽医 | 157篇 |
园艺 | 333篇 |
植物保护 | 72篇 |
出版年
2024年 | 28篇 |
2023年 | 45篇 |
2022年 | 65篇 |
2021年 | 90篇 |
2020年 | 94篇 |
2019年 | 113篇 |
2018年 | 66篇 |
2017年 | 136篇 |
2016年 | 194篇 |
2015年 | 121篇 |
2014年 | 187篇 |
2013年 | 221篇 |
2012年 | 283篇 |
2011年 | 344篇 |
2010年 | 288篇 |
2009年 | 293篇 |
2008年 | 235篇 |
2007年 | 232篇 |
2006年 | 229篇 |
2005年 | 185篇 |
2004年 | 144篇 |
2003年 | 102篇 |
2002年 | 96篇 |
2001年 | 86篇 |
2000年 | 69篇 |
1999年 | 47篇 |
1998年 | 50篇 |
1997年 | 38篇 |
1996年 | 35篇 |
1995年 | 39篇 |
1994年 | 39篇 |
1993年 | 20篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 26篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有4327条查询结果,搜索用时 15 毫秒
81.
82.
藤本月季组织培养快繁研究 总被引:17,自引:2,他引:17
该文是对最新引进的荷兰优良藤本月季进行组织培养快速繁殖研究.经过试验对比,筛选出适合多数品种增殖分化的培养基及生根培养基.最佳的继代增殖培养基为MS+6BA0.5~1.0mg·L-1,适宜的生根培养基为1/2MS+IBA0.2mg·L-1,生根率达100%.在试管苗的移栽试验中摸索了移栽基质等与成活率的关系,使移栽成活率达98%以上. 相似文献
83.
Laetitia Herrmann Lambert Bräu Agnès Robin Henri Robain Wanpen Wiriyakitnateekul Didier Lesueur 《Archives of Agronomy and Soil Science》2016,62(7):1041-1048
Rubber tree is a very important crop in Thailand, representing an essential source of income for farmers. In the past two decades, rubber tree plantations have been greatly expanding in unfavorable areas, where climate conditions are difficult and soil fertility is very poor. To optimize latex yields, mineral fertilizers have been widely used. A better understanding of the roles of the biological compartment in soil fertility is essential to determine alternative management practices to sustain soil fertility and optimize latex yields. Arbuscular mycorrhizal fungi (AMF) are widely recognized as beneficial for plants, mainly through their role in improving plant nutrient uptake. The objective of this study was to assess the AMF populations in rubber tree plantations and the impact of both soil characteristics and plantation age on these communities. Our results showed that all rubber trees were highly colonized, regardless of the soil structure and nutrient contents. AMF colonization was not affected by the age of the trees, suggesting that maintaining the symbiosis is likely to be beneficial at all stages. A better understanding and management of the microbial communities would contribute to maintaining or restoring soil fertility, leading to a better tree growth and optimized latex yield. 相似文献
84.
根据多年的试验实践,总结出适合于公路绿化的6种乔灌木意杨、银杏、金叶千头柏、蜀桧栀子花和红叶小蘖,并介绍了这些树种的生长特性以及最适宜的扦插繁殖技木,将对今后的公路绿化有一定参考价值。 相似文献
85.
Two complementary studies were performed to examine (1) the effect of 18 years of nitrogen (N) fertilization, and (2) the effects of N fertilization during one growing season on soil microbial community composition and soil resource availability in a grassland ecosystem. N was added at three different rates: 0, 5.44, and 27.2 g N m−2 y−1. In both studies, Schizachyrium scoparium was the dominant plant species before N treatments were applied. Soil microbial communities from each experiment were characterized using fatty acid methyl ester (FAME) analysis. Discriminant analysis of the FAMEs separated the three N fertilizer treatments in both experiments, indicating shifts in the composition of the microbial communities. In general, plots that received N fertilizer at low or high application rates for 18 years showed increased proportions of bacterial FAMEs and decreased fungal FAMEs. In particular, control plots contained a significantly higher proportion of fungal FAMEs C18:1(cis9) and C18:2(cis9,12) and of the arbuscular mycorrhizal fungal (AMF) FAME, C16:1(cis11), than both of the N addition treatment plots. A significant negative effect of N fertilization on the AMF FAME, C16:1(cis11), was measured in the short-term experiment. Our results indicate that high rates of anthropogenic N deposition can lead to significant changes in the composition of soil microbial communities over short periods and can even disrupt the relationship between AMF and plants. 相似文献
86.
以‘霍巴’海棠(Malus‘Hopa’)的茎尖和带腋芽的幼嫩茎段为外植体,建立了比较高效的‘霍巴’海棠组培快繁体系。结果表明:‘霍巴’海棠茎尖及茎段外植体在MS+6-BA0.1mg/L+IAA 0.2mg/L+3%蔗糖+0.48%琼脂(pH 5.8)培养基上生长状况较好;将其组培苗在WPM+6-BA 0.5mg/L+NAA 0.1mg/L+ZT 0.01mg/L+3%蔗糖+0.48%琼脂(pH 5.8)培养基上继代培养40d左右,继代增殖系数均可达到3.0左右;再经1/2 WPM+NAA0.8mg/L+1.5%蔗糖+0.48%琼脂(pH 5.8)培养基生根壮苗后,移栽成活率可达97.5%。 相似文献
87.
生菜叶中磷含量的光谱定量分析 总被引:1,自引:0,他引:1
为快速、准确检测生菜叶内的磷含量,提出了应用光谱技术结合化学计量法无损检测生菜叶内磷含量的方法。通过获取不同施磷量下生菜叶片于波长350~2500nm处的反射光谱,对光谱数据进行5点平滑和一阶导数变换后,利用联合区间偏最小二乘算法(siPLS)提取了与生菜叶磷元素相关的4个特征波段,即950~1070nm, 1430~1549nm,1906~2025nm和2144~2263nm。进一步利用连续投影算法(SPA)对全光谱波段和4个特征波段进行特征波长提取,分别筛选出变量63个和25个。分别对4个特征波段、63个和25个特征波长进行主成分降〖JP2〗维,当主成分数分别为7、5和4时,隐含层神经元数分别为7、5和3时,建立了siPLS+BPANN,SPA+BPANN,siPLS+〖JP〗SPA+BPANN生菜叶磷含量检测模型。研究结果表明:siPLS+SPA+BPANN模型的预测结果优于其他模型,验证集相关系数为0.911,验证均方根误差为479mg/kg。 相似文献
88.
百合的9 个优良品种快速繁殖条件优化的研究表明,不同百合品种的鳞片分化小鳞茎能力有一定差异,高者达 86.0% ,低者仅13.0% ;低温处理可大大提高鳞片的分化率;不同部位的百合鳞片分化小鳞茎的能力不一,分化能力大小依次为下部、中部、上部;生长调节剂组合对百合鳞片分化能力和小鳞茎增殖也有较大的影响,最适宜鳞片分化的组合为 B A 0.5 m g· L- 1+ N A A 0.5 m g· L- 1,最佳的小鳞茎增殖的组合为 B A 1.0m g· L- 1+ N A A 0.1 m g· L- 1;适当提高蔗糖质量浓度对鳞茎的形成有促进作用,以100 g· L- 1效果最好. 相似文献
89.
CHEN Bi-hua Forestry Biotechnology Research Development Center Fujian Academy of Forestry Sciences Fuzhou P. R. China Key Laboratory of Timber Forest Breeding Cultivation for Mountainous Areas in Southern China State Forestry Administration P. R. China 《中国林学(英文版)》2009,(3)
In this study a reliable protocol was developed for the establishment of commercial in vitro cultures of Tripterygium wilfordii Hook f.. Juvenile shoots from one-year-old elite plants were used as the source of explants. New axillary shoots were obtained after 30 days of culture on a MS medium supplemented with BAP (2.0 mg·L–1) and NAA (0.1 mg·L–1). The optimal multiplication medium was a modified MS medium supplemented with BAP (1.0 mg·L–1) and NAA (0.1 mg·L–1). This yielded a multiplication rate of 2.4 fo... 相似文献
90.
黄颡鱼的生物学特性与养殖技术 总被引:6,自引:0,他引:6
通过对黄颡鱼的生物学特性、繁殖技术、苗种培育技术、养殖技术、放养模式、病害防治技术的系统研究,探明了黄颡鱼的食性、溶氧需求、温度适应性、盐度耐受性等生物学特性,报道了黄颡鱼繁殖与苗种培育措施,提出池塘养殖所需配套技术及常见病害防治技术。 相似文献