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   5644篇
  免费   383篇
  国内免费   744篇
林业   227篇
农学   1034篇
基础科学   53篇
  335篇
综合类   2693篇
农作物   827篇
水产渔业   178篇
畜牧兽医   1096篇
园艺   198篇
植物保护   130篇
  2024年   35篇
  2023年   163篇
  2022年   258篇
  2021年   285篇
  2020年   265篇
  2019年   321篇
  2018年   202篇
  2017年   292篇
  2016年   356篇
  2015年   349篇
  2014年   406篇
  2013年   384篇
  2012年   468篇
  2011年   451篇
  2010年   344篇
  2009年   351篇
  2008年   299篇
  2007年   314篇
  2006年   220篇
  2005年   200篇
  2004年   108篇
  2003年   126篇
  2002年   94篇
  2001年   78篇
  2000年   47篇
  1999年   44篇
  1998年   47篇
  1997年   40篇
  1996年   30篇
  1995年   33篇
  1994年   34篇
  1993年   24篇
  1992年   23篇
  1991年   13篇
  1990年   15篇
  1989年   14篇
  1988年   10篇
  1987年   5篇
  1986年   9篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1981年   2篇
  1978年   1篇
  1963年   2篇
  1962年   2篇
  1956年   3篇
排序方式: 共有6771条查询结果,搜索用时 15 毫秒
81.
试验选用30kg商品猪60头,随机分为4组,设1个对照组及3个试验组,试验组分别在对照组基础上每100kg日粮添加50g、100g、150g甜菜碱,探讨甜莱碱对育肥猪生长性能及胴体品质效果。表明,甜菜碱能有效地促进商品猪生长、改善胴体品质。添加剂量以每100 kg日粮中添加100g~150g甜菜碱较为适宜。  相似文献   
82.
微卫星序列是以1~6个短核苷酸为基本重复单位的重复序列,呈共显性、重复性好、多态性丰富和操作简单,在基因定位与QTL分析、亲权分析、分子标记辅助选择等方面应用广泛.本文综述了与肉牛部分经济性状(生长发育性状、胴体性状、肉质性状、多胎性状和出生重)相关的微卫星标记研究进展.  相似文献   
83.
The experiment was aimed to investigate the effects of dietary alfalfa powder on the growth performance,body size,slaughter performance,organ index and meat quality of Siji geese.A total of 256 15-day-old geese (half male and half female) with similar body weight were randomly divided into four groups with 4 replicates of 16 geese each.The geese in control group were fed with corn-soybean meal-based diet (control diet),and geese in the experimental groups were fed the basal diet replaced with 10%,20% and 30% alfalfa powder,respectively.The results showed that,compared with the control group,dietary alfalfa powder supplementation had no significant effect on the average daily intake,average daily gain,feed conversion ratio,body oblique length,keel length,shin circumference,semi diving length,chest width and shin length (P>0.05),and also had no effect on the carcass ratio,half-eviscerated carcass ratio and pectoral muscle ratio (P>0.05).However,dietary 20% and 30% alfalfa powder supplementation significantly increased the chest depth (P<0.05),dietary 30% alfalfa powder significantly decreased the full-eviscerated carcass ratio (P<0.05),and dietary 10% alfalfa powder significantly increased the leg muscle ratio (P<0.05) of geese.In addition,dietary alfalfa powder significantly decreased the abdominal fat ratio (P<0.05),raised the growth index of liver,jejunum,ileum,and cecum (P<0.05),and increased the water loss rate of pectoral muscle and leg muscle (P<0.05) compared with the control group.Dietary 10% and 30% alfalfa powder significantly increased duodenal growth index (P<0.05) of geese.In conclusion,dietary alfalfa powder supplementation might improve the slaughter performance (increase chest depth and leg muscle ratio,reduce abdominal fat rate) and organ growth index (increase the growth index of liver,duodenum,jejunum,ileum and cecum).However,dietary alfalfa powder increased water loss rates in pectoral muscle and leg muscle,and 30% alfalfa powder reduced the full-eviscerated carcass ratio of geese.The appropriate supplementation level of alfalfa powder was recommended at 10% in the present study.  相似文献   
84.
将广义线性混合模型(GLMM)引入动物离散性状的遗传分析及个体的遗传评定,初步比较了GLMM方法与一般线性方法(LM)的估计效果。模拟研究的性状为单阈值二项分类性状,选用的连接函数为对数连接μi=eη/(1+eη),方差函数为V(μi)=μ(i1-μi)/n,试验设计为全同胞-半同胞混合家系,参数估计采用Fisher迹法。结果表明:GLMM方法能较准确地估计公畜的个体育种值,在个体的遗传评定效果方面要明显优于常规的线性方法,其预测的育种值排序结果与真实育种值的排序之间存在极显著的相关性(P<0.001)。  相似文献   
85.
Due to the several advantages expected from growing self-compatible almond cultivars, breeding programmes have recently introduced self-compatibility as an important trait. However, doubts have arisen regarding the capability of the newly obtained self-compatible almonds to produce good yields in monovarietal plantations, and the commercial quality of the fruits from self-pollination. For this reason, in the last years several studies have been conducted to evaluate fruit set and fruit traits following self- and cross-pollination of self-compatible almonds. Their results showed inconsistencies for fruit set and for some of the fruit traits studied. Thus, while some studies showed no differences between both pollination types for any of the fruit traits, others clearly showed important differences with the detriment of self-pollination for commercially important fruit traits. The fact that some of these studies evaluated a low number of individuals and/or fruit traits, implies the need of a more complete study. In this work, 10 fruit traits were studied in 26 self-compatible almonds following self-pollination by bagging and open pollination treatments. In general, and despite a few individuals showed differences between both pollination types for two of the traits, the results showed no influence of self-pollination in fruit quality.  相似文献   
86.
桑白毛虫在重庆市一年发生2代,越冬后的蛹在5月中旬进入羽化期.第1代桑白毛虫各虫态历期:卵期3.9天,幼虫期21.2天(25.99℃),蛹期61.5天,成虫寿命5~7天;幼虫发生盛期在5月中旬~6月中旬,每头幼虫全龄食桑量9234.73mg,经6个龄期而化蛹;成虫羽化盛期在8月下旬~9月上旬,每雌平均产卵量447粒,雌:雄=1:1.48.第2代桑白毛虫幼虫发生期从8月下旬开始至11月底结束,盛期在10月中旬~11月中旬,幼虫全龄经过46.22天(17.48℃),幼虫食桑量与第1代相近似,化蛹期集中在气温较低(15℃~16℃)的11月份.  相似文献   
87.
This study was aimed to analyze the genetic variation of insulin-like growth factor binding protein 2 (IGFBP2) gene effect on meat quality traits in pigs. A pair of primer was designed,which based on DNA sequence of IGFBP2 gene (GenBank accession No.:BV727778). The genetic polymorphism of IGFBP2 gene was detected by PCR-RFLP in Sujiang pig, Jiangquhai pig and Landrace pig, and the association between IGFBP2 gene polymorphism and meat quality traits in three pig breeds was analyzed. The results showed that three genotypes (AA, AB and BB) were detected. The Chi-square test results showed that the genotype distribution of three pig breeds was in Hardy-Weinberg equilibrium (P > 0.05). The polymorphism information content (PIC) were moderately polymorphic in three pig breeds. According to the association analysis of different genotypes, significant difference was found in color value, intramuscular fat content and marbling, the color value (except for Jianquhai pig) and intramuscular fat content of AA genotype were significantly higher than AB and BB genotypes (P < 0.05), the marbling of AA and AB genotypes was significantly higher than BB genotype (P < 0.05). In conclusion,the polymorphism of IGFBP2 gene intron 3 had significant effects on meat quality traits, and was candidate gene for the potential impact on meat quality traits of pigs.  相似文献   
88.
^60Co-γ射线诱发的8个灿温敏核不育系水稻叶色突变系可分为三种类型,即叶色突变高温表达型、低温表达型及温钝型。  相似文献   
89.
通过3种生物有机肥和牛粪在糯米香茶上的应用研究,发现3种生物有机肥均能改善农艺性状和感官品质并提高茶叶产量。其中金葵子生物有机肥处理效果稍好;恒丰生物有机肥处理效果居中;沃野诺丰生物有机肥处理效果稍差。  相似文献   
90.
采用PCR-RFLP技术检测H-FABP基因5′上游区1125~1817区段HinfⅠ酶切位点在撒坝猪群体中的多态性分布,并采用最小二乘分析模型初步统计分析检测位点多态性与部分生产性能的相关性。结果表明,H-FABP基因等位基因H及基因型Hh在群体中占优势,频率分别为0.6022和0.4194;H-FABP基因在群体中处于Hardy-Weinberg平衡状态;H-FABP基因检测位点基因型间在生长和繁殖性状上不存在不利影响。  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