全文获取类型
收费全文 | 1766篇 |
免费 | 109篇 |
国内免费 | 180篇 |
专业分类
林业 | 241篇 |
农学 | 256篇 |
基础科学 | 127篇 |
165篇 | |
综合类 | 620篇 |
农作物 | 175篇 |
水产渔业 | 88篇 |
畜牧兽医 | 197篇 |
园艺 | 59篇 |
植物保护 | 127篇 |
出版年
2024年 | 11篇 |
2023年 | 27篇 |
2022年 | 49篇 |
2021年 | 72篇 |
2020年 | 62篇 |
2019年 | 75篇 |
2018年 | 51篇 |
2017年 | 62篇 |
2016年 | 55篇 |
2015年 | 54篇 |
2014年 | 71篇 |
2013年 | 85篇 |
2012年 | 104篇 |
2011年 | 112篇 |
2010年 | 81篇 |
2009年 | 71篇 |
2008年 | 76篇 |
2007年 | 75篇 |
2006年 | 56篇 |
2005年 | 58篇 |
2004年 | 57篇 |
2003年 | 111篇 |
2002年 | 164篇 |
2001年 | 137篇 |
2000年 | 70篇 |
1999年 | 53篇 |
1998年 | 21篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 24篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 16篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 13篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1945年 | 1篇 |
1935年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有2055条查询结果,搜索用时 31 毫秒
41.
Xiao‐Qing Dong Gui‐Juan Qu Yu‐Ke Chen Gui‐Qin Wang Dan Jiang 《Aquaculture Research》2019,50(7):1752-1761
A 60‐day feeding trial was conducted to examine the effects of different levels (0, 100, 200, 400 and 600 mg/kg) of antimicrobial peptides on growth, protease activity of foregut, the morphology of foregut villi and related genes mRNA expression level in the common carp (Cyprinus carpio). The results showed that the feed of antimicrobial peptides promote common carp growth, and the optimal dosage of antimicrobial peptides is 200–333 mg/kg in the common carp feed. The protease activity of 200 and 400 mg/kg groups were significantly higher than the control and other groups (p < 0.05). The foregut villus height with 100, 200 and 400 mg/kg antimicrobial peptide groups were significantly higher than control group (p < 0.05). The crypt depth of 200 and 400 mg/kg antimicrobial peptide groups were significantly lower than control group (p < 0.05). The ratio of villus height and crypt depth of 100, 200 and 400 mg/kg antimicrobial peptide groups were significantly higher than control group (p < 0.05). The ratio with 600 mg/kg group was significantly lower than the control group (p < 0.05). The IGF‐I gene expression level of 200 mg/kg and 400 mg/kg groups were significantly higher than the control group and 600 mg/kg group (p < 0.05). The IL‐1β gene expression level of 100 mg/kg and 200 mg/kg groups were significantly higher than the control group (p < 0.05). These results indicated up‐regulation of growth and immune related genes in antimicrobial peptides fed common carp. Correlation analysis showed that IGF‐I mRNA and IL‐1β mRNA were positively correlated with SGR. IL‐1β mRNA and FCR were significantly negative correlated. It indicated that growth and immune gene common regulated the growth of the carp under antimicrobial peptides intervention. In conclusion, antimicrobial peptides can improve growth and related genes mRNA expression in the common carp. Further studies using molecular biological technique or immunologic methods are required to conclude that antimicrobial peptides are beneficial in common carp. 相似文献
42.
Production of inbred larvae through self‐fertilization using oocytes and cryopreserved sperm from the same individuals after sex reversal in eastern oyster Crassostrea virginica
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The eastern oyster Crassostrea virginica can change sex which makes self‐fertilization possible if sperm can be cryopreserved. In this study, small (~1 year old) and large (~2–3 years old) oysters were biopsied for sperm collection. Survival of the biopsied oysters after 1 year was 50% for small oysters and 17% for large oysters. Oocytes were collected from sex‐reversed females, and self‐fertilized with cryopreserved sperm. Of the 24 cryopreserved samples, 14 individuals had ≤1% fertility when crossed with oocytes from unrelated females, indicating that the cryopreserved sperm had reduced fertility. The other 10 individuals had a fertility of 39 ± 25% when crossed with oocytes from unrelated females (non‐selfing), but showed a significantly lower success of self‐fertilization (12 ± 16%) (P = 0.008), while aliquots of the same oocytes had a fertilization of 83 ± 11% when crossing with fresh sperm. Larvae were produced at day 3 in the self‐fertilized families (12–94% of the fertilized oocytes), and survived to eyed‐larvae stage at days 11–14. Genotyping with 9 microsatellite markers confirmed that the larvae resulted from self‐fertilization in four families. This study demonstrated the feasibility of creating self‐fertilized inbred lines of oysters by use of non‐lethal sperm collection and cryopreservation. 相似文献
43.
Impacts of diet on hindgut microbiota and short‐chain fatty acids in grass carp (Ctenopharyngodon idellus)
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yao Tong Hao Shan Gong Wu Ivan Jakovlić Hong Zou Wen Xiang Li Gui Tang Wang 《Aquaculture Research》2017,48(11):5595-5605
Diet is known to influence intestinal microbiota in fish, but the specifics of these impacts are still poorly understood. Different protein/fibre ratio diets may result in differing structures and activities of gut microbiota. We examined the hindgut microbiome of grass carp (Ctenopharyngodon idellus) fed three different diets: fish meal (FM, high protein – low fibre), Sudan grass (SG, high fibre – low protein) and compound feed (CF, intermediate). Microbial profiles of fish fed on FM were significantly different from profiles of fish fed CF and SG (F = 18.85, p < .01). Cetobacterium, known to be positively associated with protein digestion, was the dominant microbial group in FM samples (approximately 75.7%), while Lachnospiraceae and Erysipelotrichaceae, thought to be involved in fermentation of plant polysaccharides, were dominant in CF and SG samples (46.8% and 42.9% respectively). Network analyses indicated that the abundance of Lachnospiraceae and Erysipelotrichaceae was in a significantly positive correlation (r = .895, p = .001). Short‐chain fatty acid (SCFA) levels may indicate that the digestibility of diet by microbiota in the grass carp gut decreased from FM to SG (FM>CF>SG). Overall low SCFA levels indicate that hindgut fermentation probably provides a low proportion of energy requirements in grass carp. 相似文献
44.
Microsatellites have become the preferred molecular markers for strain selection and genetic breeding in fish. In this study
a total of 105 microsatellites were isolated and identified in gibel carp (Carassius auratus gibelio) by microsatellite sequence searches in GenBank and other databases and by screening and sequencing of positive clones from
the genomic library enriched for AG and GATA repeats. Moreover, nineteen microsatellites were randomly selected to design
locus-specific primer pairs, and these were successfully used to identify and discriminate different cultured strains of gibel
carp including strains A, D, L, and F. Three different types of microsatellite pattern were distinguished by the number and
length of fragments amplified from the 19 primer pairs, and some microsatellite primer pairs were found to produce different
microsatellite patterns among strains and strain-specific fragments. In addition, some duplicated alleles were also detected
in two microsatellite patterns. Therefore, the current study provides direct molecular markers to discriminate among different
cultured strains for selective breeding and aquaculture practice of gibel carp. 相似文献
45.
46.
47.
48.
播期和密度对冬小麦籽粒产量和营养品质及生理指标的影响 总被引:16,自引:1,他引:16
为了研究播期和密度对冬小麦籽粒产量和营养品质及生理指标的影响,以中筋小麦中任1号为材料,在大田条件下进行不同播期和密度试验.结果表明,旗叶展开后0~28 d,早播和适播的小麦叶绿素含量高于晚播,生育后期晚播比早播和适播叶绿素含量高,叶绿素含量在不同密度处理间差异不显著.晚播比早播和适播旗叶平均含氮量分别高7%和4%,旗叶含氮量在不同密度处理间差异不显著.播期对籽粒产量及其构成因素有显著影响,籽粒产量和蛋白质产量以适播处理最高,在不同密度处理间除穗粒数差异显著外,其余均不显著.播期对清蛋白、醇溶蛋白和总蛋白含量有显著影响,对球蛋白和谷蛋白含量影响不显著,总蛋白含量以A2播期处理最高.除球蛋白外,总蛋白及其他组分舍量在密度处理问差异均不显著,以B1处理最高.研究结果说明,籽粒产量和蛋白质产量以A2B2处理最高,营养品质以A281处理最佳.旗叶展开后21 d时,旗叶叶绿素含量与清蛋白和球蛋白含量呈极显著或显著正相关(r=0.73**,r=0.57*). 相似文献
49.
为探讨面粉白度与色泽相关因子的遗传特性及相互关系,选择11个在面粉白度等性状方面具有不同特点的小麦品种作亲本,按5×6不完全双列杂交设计组配杂交组合,对30个F1杂种和11个亲本的面粉白度与色泽相关因子进行了分析。结果表明,面粉白度、黄色素含量、多酚氧化酶活性在亲本表型值与其一般配合力效应值间存在显著的正相关。在亲本表型值间和一般配合力效应值间,面粉白度与黄色素含量均呈显著负相关,与多酚氧化酶活性间无显著相关性。面粉白度、黄色素含量和多酚氧化酶活性的广义遗传力和狭义遗传力都较高,主要受基因加性效应影响,适合在早代进行选择。德麦3号、济麦22号和济麦20号都能较好地降低后代的黄色素含量和多酚氧化酶活性,是小麦白度育种中较适宜选择的亲本。在优质中强筋小麦育种中,不应过分追求面粉的白度和亮度,但可通过对低多酚氧化酶活性和低黄色素含量的选择,培育面粉色泽优良的小麦新品种。 相似文献
50.
我国春麦区部分小麦品种品质状况分析 总被引:20,自引:6,他引:20
1999年将 38份春小麦品种 (品系 )种植于内蒙古呼和浩特 ,对其磨粉品质和面包烘烤品质进行了评价。结果表明 ,我国春小麦品种的面包烘烤品质较差 ,不同地区品种间品质差异较大 ,辽宁和内蒙品种的磨粉品质和面包烘烤品质优于其它地区的品种。回归分析表明 ,蛋白质含量和单位蛋白质含量的面包体积决定了面包体积总变异的 99.9% ,硬度、沉淀值和吸水率对面包总分有重要作用。品种的出粉率主要取决于 1心槽路出粉率 ,2心和 1皮槽路出粉率对出粉率贡献也较大。高分子量麦谷蛋白亚基 (HMW GS)Glu A1和Glu D1位点的等位变异与品质性状密切相关。面包烘烤品质的改良应在分析HMW GS的基础上 ,将硬度作为选择指标之一 ,适当提高蛋白质含量 ,重点加强对沉淀值的选择 相似文献