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   3786篇
  免费   251篇
  国内免费   485篇
林业   6篇
农学   67篇
基础科学   84篇
  281篇
综合类   1553篇
农作物   8篇
水产渔业   21篇
畜牧兽医   2487篇
园艺   11篇
植物保护   4篇
  2024年   18篇
  2023年   65篇
  2022年   129篇
  2021年   268篇
  2020年   186篇
  2019年   261篇
  2018年   106篇
  2017年   181篇
  2016年   185篇
  2015年   177篇
  2014年   215篇
  2013年   208篇
  2012年   289篇
  2011年   279篇
  2010年   207篇
  2009年   218篇
  2008年   172篇
  2007年   243篇
  2006年   166篇
  2005年   138篇
  2004年   109篇
  2003年   102篇
  2002年   72篇
  2001年   78篇
  2000年   63篇
  1999年   64篇
  1998年   35篇
  1997年   30篇
  1996年   20篇
  1995年   29篇
  1994年   27篇
  1993年   26篇
  1992年   30篇
  1991年   17篇
  1990年   24篇
  1989年   21篇
  1988年   8篇
  1987年   10篇
  1986年   5篇
  1982年   5篇
  1981年   1篇
  1980年   2篇
  1979年   7篇
  1978年   5篇
  1977年   3篇
  1976年   2篇
  1975年   1篇
  1974年   8篇
  1973年   2篇
  1956年   5篇
排序方式: 共有4522条查询结果,搜索用时 15 毫秒
81.
To reveal the relationship between inhibin-α(INHA) gene and the reproductive traits of Congjiang Xiang pig, INHA gene was cloned and sequenced taking the genomic DNA of Congjiang Xiang pigs as templates by polymerase chain reaction(PCR) method.The polymorphisms of INHA gene were tested in Congjiang Xiang pig populations with high-litter size and low-litter size using allele-specific PCR(AS-PCR) method.The expression profile of INHA gene in ovaries was detected from Congjiang Xiang pigs with high-litter yiled or low-litter yiled by Real-time PCR method.The complete coding region of INHA gene was 1095 bp in length, which coded for 364 amino acid residues.Compared with the known sequence, two candidate sites, G359A and A373G, were found out from exon 2 region of INHA gene in Congjiang Xiang pig.After investigation for the two sites in a large population, the frequency of alleles between two populations was not significant and without obvious relativity with the litter yiled of Congjiang Xiang pig.However, the INHA mRNA level in the ovary of Congjiang Xiang pig with high-litter yiled was higher than that with low-litter yiled.It suggested that INHA gene was much conserved, INHA gene expression level might be concerned for the regulation of ovary growth and follicle development in Congjiang Xiang pig breed.  相似文献   
82.
To study the expression pattern of THBS3 gene in different tissues and during skeletal muscle development, the THBS3 gene expression in different tissues and skeletal muscles during prenatal periods (33, 45, 65, 70 and 90 d) and postnatal periods (0, 9, 30, 60, 120 and 160 d) from Landrace and Tongcheng pigs were detected by Real-time quantification PCR.The results showed that THBS3 gene widely expressed in all tissues examined, exhibiting similar spatial expression patterns with expression peaks in lung in both pig breeds except in stomach and intestine.Moreover, although THBS3 gene showed a significant higher expression level in gestation than after birth in Landrace and Tongcheng pigs (P<0.05), it exhibited different expression patterns between Landrace and Tongcheng pigs, the expression peak was detected at gestation day 45 in Landrace pig, while was detected at gestation day 65 in Tongcheng pig.The results suggested that THBS3 gene involved in skeletal muscle growth and development in pigs, as well as the regulation of asynchronization of skeletal muscle development in different pig breeds.  相似文献   
83.
Immunogenic properties and mycoplasmal pneumonia of swine (MPS) lung lesions were compared between the immunity‐selected Large White line and the non‐selected Large White line. The selected Large White line showed a higher level of pulmonary MPS lesions compared with the non‐selected Large White line. Subsequent to vaccination, the percentage of natural killer cells and T cells (CD3+CD4+CD8 and CD3+CD4?CD8+ T cells) were significantly increased in the non‐selected line but remained unchanged in the immunity‐selected Large White line. Secretion of Mycoplasma hyopneumoniae vaccine‐specific immunoblogulin G and phagocyte activity in peripheral blood were significantly higher in the immunity‐selected Large White line than in the non‐selected line. Expression of interleukin (IL)‐4 and IL‐6 messenger RNA in hilar lymph nodes was significantly lower in the immunity‐selected Large White line than in the non‐selected line. However, expression of IL‐10 in all immune tissues was significantly higher in the immunity‐selected Large White line. These results suggest that the selection for high immunity was not effective in increasing resistance to MPS lung lesions.  相似文献   
84.
85.
Three experiments were conducted to assess the response of weaned pigs to organic acid SF3, which contains 34% calcium formate, 16% calcium lactate, 7% citric acid and 13% medium chain fatty acids. Dietary treatments had no effect on growth performance of piglets (21‐day weaning) fed the commercial prestart diet for 1 week before receiving the experimental diets supplemented with SF3 at 0, 3 or 5 g/kg diet (Exp. 1), whereas diarrhea frequency averaged across a week was decreased by SF3 supplementation (5 g/kg diet) in piglets fed the experimental diets immediately after weaning (Exp. 2). In Exp. 3, piglets (28‐day weaning) were fed the control (containing pure colistin sulfate and enramycin, respectively, at 20 mg/kg diet) for 1 week and then were fed the control or SF3‐supplemented (5 g/kg diet) diet for 2 weeks. The SF3‐fed piglets had greater apparent ileal digestibility of calcium and dry matter, while also demonstrating greater overall gross energy, up‐regulated jejunal expression of sodium‐glucose cotransporter‐1 and transforming growth factor‐β, down‐regulated jejunal expression of tumor necrosis factor (TNF)‐α, higher ileal Lactobacillus, with lower total bacteria content, lower plasma TNF‐α but higher IgG levels than the control‐fed piglets. Collectively, SF3 consumption improved diarrhea resistance of weaned pigs by improving nutrient digestibility, piglet immunity and intestinal bacteria profile. © 2016 Japanese Society of Animal Science  相似文献   
86.
87.
建立超高效液相色谱-串联质谱法测定猪牛组织中甲基盐霉素残留量。猪、牛组织中残留的甲基盐霉素,经乙腈溶液提取,硅胶固相萃取柱净化,超高效液相色谱-串联质谱法测定,外标法定量。甲基盐霉素在5 ng/mL~250 ng/mL的浓度范围内呈现良好的线性关系,甲基盐霉素在猪、牛肌肉、肝脏、肾脏、脂肪中的检测限均为2.5μg/kg,定量限均为5.0μg/kg,猪牛肌肉、肝脏、肾脏、脂肪中5.0 ng/g~100 ng/g添加浓度范围内的回收率均值为71.9%~88.4%,批内批间RSD值均<15%。  相似文献   
88.
猪场生产管理系统的设计与实现   总被引:1,自引:0,他引:1  
养猪业是我国农村经济支柱产业,随着猪场管理的集约化程度不断得到提高,对生产过程的优化和管理提出了更高的要求.将信息技术应用到猪场生产管理中对提高猪场的生产管理水平、降低生产成本,提高经济效益具有重要意义.为此,在对猪场业务进行深入分析的基础上,提出了猪场生产管理系统设计框架,把该系统划分为生猪管理、猪舍管理、用户管理、成本管理4大部分,并采用自顶向下的模块化的设计和面向对象的程序设计方法开发了一套完整的信息系统.  相似文献   
89.
猪氟烷测验的研究   总被引:5,自引:0,他引:5  
  相似文献   
90.
猪额窦的发育与其年龄的增长成正相关。湖北白猪Ⅲ系的额窦发育也遵循这一规律。它在胎儿期,额骨的鼻额部汉是一层柔软骨板,出生后形成骨松质,到15公斤体重时,骨松质开始形成小腔室,30公斤体重时,形成主窦和许多侧窦,以后主窦加大并向后伸展,侧窦逐渐融合与主窦相通,到90—120公斤体重阶段,主窦和侧窦合并向额骨后端伸展,到达两眼眶后缘的连线。随着年龄的增长还可扩大到顶骨。在这一进展的过程中,通城猪(早熟品种)额窦发育最快,长白猪的较慢,湖北白猪Ⅲ系则界于两者之间,这与它全身发育界于两者之间是一致的。说明额窦的发育与品种的成熟程度有密切关系。从这一点出发,也可看出湖出白猪Ⅲ系生长发育的成熟程度界于两者之间而偏早熟。它属于优良的瘦肉猪新品种之一。  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