首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   662篇
  免费   77篇
  国内免费   102篇
农学   10篇
基础科学   1篇
  12篇
综合类   264篇
农作物   3篇
水产渔业   480篇
畜牧兽医   65篇
植物保护   6篇
  2024年   5篇
  2023年   11篇
  2022年   8篇
  2021年   13篇
  2020年   21篇
  2019年   27篇
  2018年   17篇
  2017年   34篇
  2016年   31篇
  2015年   28篇
  2014年   38篇
  2013年   47篇
  2012年   68篇
  2011年   73篇
  2010年   53篇
  2009年   44篇
  2008年   39篇
  2007年   48篇
  2006年   31篇
  2005年   18篇
  2004年   22篇
  2003年   24篇
  2002年   20篇
  2001年   17篇
  2000年   17篇
  1999年   13篇
  1998年   12篇
  1997年   10篇
  1996年   9篇
  1995年   5篇
  1994年   7篇
  1993年   9篇
  1992年   5篇
  1991年   5篇
  1990年   4篇
  1988年   2篇
  1987年   2篇
  1986年   4篇
排序方式: 共有841条查询结果,搜索用时 15 毫秒
1.
为研究饲料中添加益生菌对锦鲤幼鱼生长性能和相关免疫基因表达的影响,以初始体重为248.13±4.71 g的锦鲤幼鱼为研究对象,在小型循环水养殖池进行60 d的养殖试验。对照组投喂无益生菌添加的普通商品饲料,试验组投喂在普通饲料中添加枯草芽孢杆菌(Bacillus subtilis)、丁酸梭菌(Clostridium butyricum)和粪肠球菌(Enterococcus faecalis)、枯草芽孢杆菌/丁酸梭菌/粪肠球菌(1∶1∶5)配制成的4组试验饲料,试验饲料的益生菌最终浓度为109 CFU/mL。结果表明,单一菌种或复合菌种的益生菌对锦鲤幼鱼的生长均有显著的促进作用(P<0.05),且对各组血液中酚氧化酶原(phenoloxidase activating system,proPO)、溶菌酶(lysozyme,LZM)和肝脏中抗菌肽(hepcidin)的相对表达量均显著上调(P<0.05),对各组肠道中GST相对表达量有所升高。与对照组相比,复合益生菌效果最好,增重率最高为38.13%,特定生长率提高25.58%,血液中proPO和LZM相对表达量分别升高3倍和2倍之多(P<0.05),肠道中谷胱甘肽S-转移酶(glutathione S-transferase,GST)相对表达量升高了32.45%(P<0.05),肝脏中Hepc相对表达量升高了76.82%(P<0.05)。试验结果提示,在饲料中添加单一/复合益生菌,均可有效提高锦鲤幼鱼的生长性能,以复合益生菌使用效果更好,且proPO、LZM、GST和Hepc免疫基因相对表达量在不同程度上均高于对照组,可见枯草芽孢杆菌、丁酸梭菌和粪肠球菌可以作为益生菌应用于锦鲤养殖。  相似文献   
2.
两种菊酯类农药对鲤血细胞的影响   总被引:2,自引:0,他引:2  
采用对鲤肌肉注射不同浓度的高效反式氯氰菊酯和功夫菊酯,研究了两种菊酯类农药对鲤血细胞形态、红细胞渗透脆性的影响。结果显示:随两种农药攻毒浓度增大、时间延长,鲤血细胞异形率增大。低浓度(6、60μg/kg)中毒鲤成熟红细胞大小不一,核稍有畸形,淋巴细胞、单核细胞增多,核浆界限不清,有空泡,甚至伴有核溶解的白细胞;而高浓度(600、6 000μg/kg)中毒鲤血细胞中除伴有低浓度中毒症状,还出现了染色质模糊,部分白细胞核浆界限不清,甚至溶解,退化更明显。红细胞渗透脆性亦随攻毒浓度增大、时间延长而增高,且开始溶血点的变化幅度较完全溶血点大,表明最小抵抗值更易受环境因子影响。  相似文献   
3.
为研究水环境中Ni~(2+)对鲤鱼鳃和肝脏的组织损伤,将鲤鱼(Cyprinuscarpio)暴露在Ni~(2+)浓度为0、0.55、0.62、0.72、0.83、0.96、1.09、1.25mmol/L的水环境中进行急性毒性试验,并通过组织切片观察鳃和肝脏的组织病理变化。结果显示,Ni~(2+)对鲤鱼的96h半数致死浓度(LC_(50))为0.72 mmol/L,安全浓度(SC)为0.007 2 mmol/L。高浓度Ni~(2+)(1.25 mmol/L)试验组鲤鱼的鳃小片呼吸上皮细胞坏死、脱落,肝血窦淤血,肝细胞核固缩;中低浓度Ni~(2+)(0.72~1.09mmol/L)试验组鲤鱼的鳃小片呼吸上皮水肿浮离、细胞增生,血窦充血,肝细胞胞浆空泡化。表明水环境中的Ni~(2+)浓度高于0.007 2mmol/L时会对鲤鱼的鳃和肝脏造成急性毒性,导致鳃和肝脏出现明显的组织病理变化。  相似文献   
4.
草鱼肾组织细胞系CIK的建立及其生物学特性   总被引:20,自引:3,他引:20  
作者于1982年1月开始进行草鱼肾组织单层细胞培养,至今已连续培养32个月,传至120多代,建立了细胞系,定名为草鱼肾组织细胞系(CIK)。本文介绍了原代和传代培养、细胞形态、细胞生长速度和分裂指数、细胞的保存和对温度的适应性、细胞染色体分析以及细胞系对病毒敏感性的试验和研究结果。CIK生长迅速、适应性强、以20℃-38℃生长较好,28℃左右生长稳定,pH为6.5时仍能保持致密单层,染色体数为非整倍体,众数为55。对草鱼出血病左右病毒FRV具敏感性。  相似文献   
5.
鱼肉酶解物及壳聚糖对鲤鱼涂膜保鲜效果的研究   总被引:1,自引:0,他引:1  
以感官评分、挥发性盐基氮、菌落总数、K值为指标,研究比较了鱼肉酶解物和壳聚糖为原料的涂膜液对鲤(Cyprinus carpio)(4℃)冷藏过程中品质变化的影响。结果显示:贮藏期间,对照组的感官评分显著低于各涂膜组(P<0.05)。贮藏前8 d,涂膜组能够显著抑制K值的升高(P<0.05)。鱼肉酶解物和壳聚糖涂膜组均能够显著抑制细菌的生长,而贮藏2~6 d内鱼肉酶解物涂膜鲤鱼的菌落总数显著低于壳聚糖涂膜组(P<0.05)。贮藏后期,鱼肉酶解物组能延缓TVB-N值的升高,壳聚糖涂膜组能够显著抑制TVB-N值的升高(P<0.05)。鱼肉酶解物可作为一种新的可食性涂膜材料,用于延长鲤鱼的贮藏期。  相似文献   
6.
A total of 1050 juvenile Jian carp (Cyprinus carpio var. Jian) (8.20 ± 0.02 g) were fed diets containing seven graded levels of thiamin (0.25, 0.48, 0.79, 1.06, 1.37, 1.63 and 2.65 mg kg?1) for 60 days to investigate the effects of thiamin on growth, body composition and digestive enzyme activities. Percent weight gain (PWG), feed intake and feed efficiency (FE) were the lowest in fish fed the basal diet (P < 0.05). Protein productive value and lipid productive value increased with increasing dietary thiamin levels up to 1.06 and 0.79 mg kg?1 diet, respectively (P < 0.05). Body protein and lipid increased with increasing dietary thiamin levels (P < 0.05), while moisture and ash of fish carcasses decreased with the increase in dietary thiamin supplementation (P < 0.05). Intestinal folds height had a similar trend to PWG (P < 0.05). Activities of α‐amylase, lipase, trypsin, Na+, K+‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase in intestine were all affected by the dietary thiamin (P < 0.05). In conclusion, thiamin could improve growth and intestinal enzyme activities of juvenile Jian carp. The dietary thiamin requirement of juvenile Jian carp (8.0–60.2 g) based on PWG was 1.02 mg kg?1 diet.  相似文献   
7.
Selenium is essential for the normal life processes, and all animals, including fish, need this inorganic element. In order to research the pathology of selenium deficiency in common carp, Cyprinus carpio L., 360 juvenile carp were allocated to three treatments. Each treatment containing 120 fish was randomly divided into four groups, fed with purified diets containing selenium at 0, 0.15, 0.30 and 0.45 mg kg?1. The results indicated that the morbidity and mortality rates of the test groups were negatively correlated with the level of selenium in the diets. The morbidity and mortality rates were, respectively, 46.7%, 33.3%, 13.3%, 0 and 26.7% 16.7%, 6.7%, 0. The affected fish exhibited pathological changes, such as ‘thin back disease’ and lordosis. Histologically, there was no abnormality observed in muscles, liver and pancreas. Ultrastructurally, there was swelling of the mitochondria of the cardiac muscle cells, the liver cells and renal tubular epithelial cells, with disintegration and lysis of the cristae of the mitochondria which vesiculated. Serum glutamic oxaloacetic transaminase and glutamic pyruvic transaminase levels were increased and the activity of the serum glutathione peroxidase and the serum superoxide dismutase was decreased; in contrast, the serum malonaldehyde concentration was increased.  相似文献   
8.
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   
9.
Maize gluten (a byproduct from the starch industry) was used at four different levels (5, 10, 15 and 20% w/w) replacing the fish meal, a component of supplementary diet, under a semi-intensive culture system. The impact of different diets on the physico-chemical parameters of water, growth and flesh quality of catla, Catla catla; rohu, Labeo rohita; and mrigal, Cirrhina mrigala was studied. Growth in terms of body weight gain was highest when fed a diet having 5% maize gluten (replacing fish meal at 25% level) for all the fish species. However, incorporation of maize gluten at higher levels led to decline in growth, since maize gluten is deficient in essential amino acids like methionine, lysine and threonine, etc. The flesh quality in terms of total protein, total lipid, total sugar, moisture and total ash was also determined at the termination of the experiment to see whether there was any significant variation with the incorporation of maize gluten or not.  相似文献   
10.
天然免疫系统是硬骨鱼类抵抗病毒感染的主要防御系统,三重基序(tripartite motif, TRIM)蛋白家族作为天然免疫系统的重要组成部分,参与病毒感染的免疫网络调控,其中,TRIM25已被证实在多种鱼类的免疫反应中发挥重要作用。本研究对鲤(Cyprinus carpio) trim25基因的16个拷贝进行了序列进化分析、共线性分析和功能域结构分析,并比较了各拷贝在组织中的表达和顺式调控位点的差异。序列比对和系统进化分析结果均显示,位于鲤11和12号染色上、结构完整的TRIM25的2个拷贝与金线鲃(Sinocyclocheilus grahami)和斑马鱼(Danio rerio)的TRIM25蛋白结构高度相似,与鲤科鱼类以外的其他物种的结构差异较大。基因共线性结果显示,trim25基因上下游基因在不同物种的进化过程中相对保守。鲤TRIM25蛋白的结构分析显示,在鲤TRIM25的16个拷贝中,有6个拷贝具有完整功能结构域,其中,各有5个拷贝在鲤的肝与脑组织中高表达。在构建的表达数量性状基因座(eQTL)调控网络中,在肝和脑组织中分别筛选到5个和17个顺式调控trim25基因表达的单核苷酸多态性(SNP)位点。本研究对鲤trim25基因多个拷贝的序列差异进行了比较,并对鲤与其他物种TRIM25的序列、进化关系和共线性相似度进行了比较,揭示了鲤trim25各拷贝间的结构多样性和在组织中的表达情况,筛选出了可能调控trim25基因表达的SNP位点,为今后研究鲤TRIM25相关的调控和抗病研究提供了理论依据。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号