全文获取类型
收费全文 | 998篇 |
免费 | 47篇 |
国内免费 | 73篇 |
专业分类
林业 | 23篇 |
农学 | 56篇 |
基础科学 | 9篇 |
374篇 | |
综合类 | 427篇 |
农作物 | 39篇 |
水产渔业 | 41篇 |
畜牧兽医 | 89篇 |
园艺 | 42篇 |
植物保护 | 18篇 |
出版年
2024年 | 4篇 |
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 14篇 |
2019年 | 29篇 |
2018年 | 19篇 |
2017年 | 27篇 |
2016年 | 33篇 |
2015年 | 34篇 |
2014年 | 55篇 |
2013年 | 77篇 |
2012年 | 121篇 |
2011年 | 63篇 |
2010年 | 67篇 |
2009年 | 73篇 |
2008年 | 61篇 |
2007年 | 61篇 |
2006年 | 78篇 |
2005年 | 48篇 |
2004年 | 24篇 |
2003年 | 21篇 |
2002年 | 16篇 |
2001年 | 17篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 12篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 19篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 1篇 |
排序方式: 共有1118条查询结果,搜索用时 31 毫秒
141.
Asrat Asfaw Gebremedhen Woldegiorgis Semagn A. Kolech Gedif Mulugeta Dinka Mulugeta Abigail Ngugi 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2018,68(7):596-607
Micronutrient deficiencies in diets, including iron (Fe) and zinc (Zn), are an important public health problem across population in Ethiopia. Potato is a modest source of dietary nutrients. The purpose of this study was to assess the mineral (Fe & Zn) composition of potato germplasm in Ethiopia and grower's willingness to try new potato types. The Fe and Zn contents were assessed in peeled tubers of popular farmer varieties, and newly introduced Andean diploid group Phureja accessions and improved tetraploid clones grown in multi-location trials. Grower's preferences for the new potato types was assessed using a participatory approach. Significant variations in mineral and tuber yield traits exist among the germplasm assessed and broad-sense heritability appears to be high for most traits measured, suggesting that progress through breeding can be made among these materials. However, the slightly negative correlation of tuber yield with Fe and Zn content and user appreciation traits found in this study suggests that progress in improving crops for yield and enhanced Fe and Zn concentrations with end-user acceptable quality will be challenging. The results from this study provide baseline information on Fe and Zn composition of many popular farmer varieties in Ethiopia and end-user preference criteria for evaluating new potato varieties that would help to orient the biofortification breeding to the conditions and preference of farmers. 相似文献
142.
稻壳生物炭对矿区重金属复合污染土壤中Cd、Zn形态转化的影响 总被引:6,自引:1,他引:5
明确稻壳生物炭的农业生态效应对合理利用其修复矿区重金属复合污染土壤具有重要意义。通过盆栽试验,研究了稻壳生物炭不同施用量(0、5、10、20、50、100 g·kg~(-1))对重金属复合污染土壤p H、CEC和Cd、Zn赋存形态转化的影响。结果表明:与对照相比,稻壳生物炭的添加使土壤p H升高0.18~0.29个单位,CEC提高32.89%(5.68 cmol·kg~(-1));同时,重金属复合污染土壤中弱酸提取态Cd、Zn分别降低21.88%、19.63%,氧化态Cd、Zn分别降低24.12%、18.62%,可还原态Cd、Zn分别降低13.72%、8.97%;而使残渣态Cd、Zn分别升高115.56%、39.45%。综上所述,稻壳生物炭的添加提高了矿区重金属复合污染土壤的p H和CEC,促进了重金属复合污染土壤中Cd、Zn的弱酸提取态、可氧化态和可还原态向化学性质稳定的残渣态转化,降低了土壤重金属的有效性,实现了对重金属复合污染土壤的修复。 相似文献
143.
Identification of quantitative trait loci (QTLs) for grain mineral elements can assist in faster and more precise development of micronutrient dense rice varieties through marker-assisted breeding. In the present study, QTLs were mapped for Fe and Zn concentrations in two BC2F3 mapping populations derived from the crosses of O. sativa cv Swarna with two different accessions of O. nivara. In all, 10 and 8 QTLs were identified for grain Fe and Zn concentrations in population 1, and 7 and 5 QTLs were identified in population 2, respectively. Eighty percent of the QTLs detected in both populations were derived from O. nivara. Five QTLs for Fe and three QTLs for Zn explained more than 15% phenotypic variance either in interval or composite interval mapping. The locations of O. nivara derived QTLs such as qFe2.1, qFe3.1, qFe8.2 and qZn12.1 were consistently identified in both the populations. Epistatic interaction was observed only between RM106 and RM6 on chromosome 2 and between RM22 and RM7 on chromosome 3 for Fe concentration in population 1. Sixteen candidate genes for metal homeostasis were found to co-locate with 10 QTLs for Fe and Zn concentrations in both the populations. Most of the Fe and Zn QTLs were found to co-locate with QTLs for grain yield and grain quality traits. Some of the major effect QTLs identified can be used to improve rice grain Fe and Zn concentrations. 相似文献
144.
Interactive effects of coffee bean supplementation and waterborne zinc toxicity on growth performance,biochemical variables,antioxidant activity and zinc bioaccumulation in whole body of common carp,Cyprinus carpio L.
下载免费PDF全文
![点击此处可从《Aquaculture Nutrition》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Roasted coffee powder (RCP; Coffea arabica) is usually used as a beverage for human but there are few attempts to use it as a natural feed supplement in fish diets. In this study, common carp, Cyprinus carpio L., (11.8 ± 0.09 g) were reared in zinc (Zn)‐containing water at concentrations of 0.0 or 5.0 mg/L and cosupplemented with 0.0 or 1.0 g RCP/kg diet for 6 weeks to investigate effects of RCP supplementation, Zn exposure and their interaction on fish performance, biochemical variables, antioxidant activity and Zn bioaccumulation in whole fish body. Fish growth and feed intake were significantly affected by RCP supplementation, Zn toxicity and their interaction. However, fish fed a RCP‐supplemented diet did not exhibit better performance than those fed the RCP‐free diet and both diets produced higher fish performance than the Zn‐toxicated fish. It is noticed that RCP supplementation to Zn‐toxicated fish enhanced their growth, and feed utilization as compared to Zn‐toxicated fish alone. Fish fed control and RCP‐enriched diets showed no significant differences in biochemical variables, which were significantly altered due to waterborne Zn toxicity. Moreover, Zn reduced significantly; meanwhile, RCP supplementation increased significantly superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities. Notably, Zn exposure could reduce fish growth and antioxidant activity and increase Zn deposition in whole fish body. And RCP intake could enhance the antioxidant activity exerting a protective effect against Zn toxicity, thereby reducing Zn bioaccumulation in whole fish body. 相似文献
145.
氮磷钾锌对玉米茎基腐病及产量的影响 总被引:2,自引:0,他引:2
在小麦-玉米轮作制下,通过2 a的定位施肥后,研究了氮、磷、钾、锌对玉米茎基腐病及产量的影响。结果表明:氮是影响玉米茎基腐病的首要营养因子、钾次之,连续高量施氮处理发病最重、连续不施钾处理次之,施钾可显著减轻茎基腐病的发生;氮是影响玉米产量的首要营养因子、磷次之,在氮磷配施的基础上施用钾肥可以显著提高产量、减缓发病;连续高量施磷处理的土壤有效锌含量最低,连续高量施氮处理次之;在氮磷钾配施的基础上施用锌肥,可以显著提高产量,改善玉米后期穗位叶部性状,减轻病害发生。 相似文献
146.
147.
[目的]筛选微波消解原子分光光度法测定土壤中锌含量的最优消解液。[方法]采用微波消解原子分光光度法测定土壤中锌含量,分别用盐酸+硝酸+氢氟酸、盐酸+硝酸+双氧水作为消解液,对土壤样品进行微波消解,通过对比分析试验,优化合适的消解液。[结果]微波消解原子分光光度法测定土壤锌含量过程中,采用盐酸+硝酸+氢氟酸消解液,消解较为完全,但是吸光度异常、无规律偏高,导致试验失败;盐酸+硝酸+双氧水消解液,能溶解土壤中大部分锌元素,满足分析要求。[结论]采用盐酸+硝酸+双氧水作为消解液测定土壤锌含量满足分析精度要求。 相似文献
148.
A Robertsonian translocation from Thinopyrum bessarabicum into bread wheat confers high iron and zinc contents
下载免费PDF全文
![点击此处可从《Plant Breeding》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Development of wheat–alien translocation lines has facilitated practical utilization of alien species in wheat improvement. The production of a compensating Triticum aestivum–Thinopyrum bessarabicum whole‐arm Robertsonian translocation (RobT) involving chromosomes 6D of wheat and 6Eb of Th. bessarabicum (2n = 2x = 14, EbEb) through the mechanism of centric breakage–fusion is reported here. An F2 population was derived from plants double‐monosomic for chromosome 6D and 6Eb from crosses between a DS6Eb(6D) substitution line and bread wheat cultivar ‘Roushan’ (2n = 6x = 42, AABBDD) as female parent. Eighty F2 genotypes (L1–L80) were screened for chromosome composition. Three PCR‐based Landmark Unique Gene (PLUG) markers specific to chromosomes 6D and 6Eb were used for screening the F2 plants. One plant with a T6EbS.6DL centric fusion (RobT) was identified. A homozygous translocation line with full fertility was recovered among F3 families and verified with genomic in situ hybridization (GISH). Grain micronutrient analysis showed that the DS6Eb(6D) substitution line and T6EbS.6DL stock have higher Fe and Zn contents than the recipient wheat cultivar ‘Roushan’. 相似文献
149.
By using Particle-Induced X-ray Emission (PIXE) technique, the effect of arsenic (As) on the mineral contents and translocation in the xylem of rice (Oryza sativa L. cv. ‘Akihikari’) was studied. The results suggest that exogenous As increased the concentrations of phosphorus (P), calcium (Ca) magnesium (Mg), sulfur (S), and manganese (Mn) in xylem, while the concentrations of potassium (K) remained unchanged. The highest concentration of As to the rice roots did not have any clear effect on the translocation of P, Ca, S, and chlorine (Cl) in the xylem, indicating that the increasing concentrations of the minerals may be due to a condensation effect, resulting from the repression of water movement in xylem by As-toxicity. Among the metal micronutrients, As decreased the concentrations and translocations of iron (Fe), zinc (Zn), and copper (Cu). 相似文献
150.