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   1130篇
  免费   78篇
林业   43篇
农学   32篇
基础科学   9篇
  147篇
综合类   119篇
农作物   27篇
水产渔业   92篇
畜牧兽医   678篇
园艺   17篇
植物保护   44篇
  2023年   16篇
  2022年   6篇
  2021年   31篇
  2020年   28篇
  2019年   33篇
  2018年   31篇
  2017年   23篇
  2016年   34篇
  2015年   27篇
  2014年   28篇
  2013年   56篇
  2012年   41篇
  2011年   64篇
  2010年   35篇
  2009年   37篇
  2008年   51篇
  2007年   56篇
  2006年   52篇
  2005年   55篇
  2004年   52篇
  2003年   44篇
  2002年   38篇
  2001年   21篇
  2000年   26篇
  1999年   11篇
  1998年   11篇
  1997年   10篇
  1995年   8篇
  1993年   10篇
  1992年   12篇
  1991年   11篇
  1990年   16篇
  1989年   10篇
  1988年   16篇
  1987年   17篇
  1986年   15篇
  1985年   15篇
  1984年   9篇
  1983年   11篇
  1980年   8篇
  1979年   12篇
  1978年   16篇
  1977年   9篇
  1976年   8篇
  1975年   8篇
  1973年   14篇
  1971年   6篇
  1970年   9篇
  1967年   6篇
  1966年   7篇
排序方式: 共有1208条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Avena sativa L. subsp. nudisativa has the ability to produce naked grains. Genetic studies on the naked trait of oat began over a century ago, but the genetic and molecular factors associated with the expression of this trait have not been fully clarified. The objectives of this study were to evaluate the naked trait in two oat populations of recombinant inbred lines (RILs), to determine the number of genes, to estimate the heritability, and to map genomic regions associated with the naked trait in hexaploid oat. Parental lines and RILs of each population were screened for the naked trait from plants grown in the field over a 2 year period. Based on the phenotypic data, the oat RILs were classed as naked, partially naked, partially hulled and hulled. In both populations and years, a great number of RILs showed variable expressivity for the naked trait. The genetic analysis indicated the action of a major gene (N1) with the action of modifying genes controlling the formation of naked grains. The results of the estimate of heritability show that environmental conditions do not have a great influence in determining the naked trait. The quantitative trait loci analysis detected a genomic region with a large effect on the naked trait that explained more than 50% of the phenotypic variation. Further studies are needed to validate the use of these molecular markers to assist breeding programs to select high quality and stable naked oat cultivars.  相似文献   
6.
Ruminants are major producers of meat and milk, thus managing their reproductive potential is a key element in cost-effective, safe, and efficient food production. Of particular concern, defects in male germ cells and female germ cells may lead to significantly reduced live births relative to fertilization. However, the underlying molecular drivers of these defects are unclear. Small noncoding RNAs, such as piRNAs and miRNAs, are known to be important regulators of germ-cell physiology in mouse (the best-studied mammalian model organism) and emerging evidence suggests that this is also the case in a range of ruminant species, in particular bovine. Similarities exist between mouse and bovids, especially in the case of meiotic and postmeiotic male germ cells. However, fundamental differences in small RNA abundance and metabolism between these species have been observed in the female germ cell, differences that likely have profound impacts on their physiology. Further, parentally derived small noncoding RNAs are known to influence early embryos and significant species-specific differences in germ-cell born small noncoding RNAs have been observed. These findings demonstrate the mouse to be an imperfect model for understanding germ-cell small noncoding RNA biology in ruminants and highlight the need to increase research efforts in this underappreciated aspect of animal reproduction.  相似文献   
7.
A 7-year-old male neutered domestic shorthair outdoor cat was referred for chronic left forelimb lameness, which had been treated with intra-articular injections of triamcinolone acetonide. A soft tissue swelling around the elbow joint, extending from the distal humerus to the proximal ulna, was surgically explored and biopsy samples obtained. Mycobacterium bovis was cultured from samples from the soft tissue and bone. The mycobacteria from the media were killed and the DNA extracted and tested on a multiplex real-time PCR for the absence of specific genes and the presence of mycobacterial genus markers. The PCR revealed bacillus Calmette-Guérin Danish Strain 1331; this was also isolated from the prescapular lymph node, muscle and bone, obtained at post mortem examination. Badgers had been vaccinated with the bacillus Calmette-Guérin vaccine SSI (Statens Serum Institute) in the area where the cat lived, in the spring and autumn of the previous year. To the authors' knowledge, this is the first report of infection with M. bovis bacillus Calmette-Guérin Danish Strain 1331 in a domestic cat, potentially associated with annual vaccination of badgers in the proximity of the cat's home.  相似文献   
8.
A 10‐year‐old, female spayed Shih Tzu was presented due to weight loss, increased respiratory effort and lethargy, determined to be secondary to a congenital para‐esophageal diaphragmatic defect with partial herniation of the stomach and spleen. Four days following reduction surgery of the displaced abdominal organs thoracic effusion developed. Thoracic fluid evaluation revealed a cell‐rich, protein‐poor modified transudate with neutrophils, reactive mesothelial cells, and atypical epitheloid cells which occasionally appeared to be keratinizing, consistent with neoplastic exfoliation. Thoracic effusion recurred 2 days later, with similar characteristics as the initial sample. Computed tomography (CT) indicated consolidation and displacement of the right middle and accessory lung lobes. Exploratory thoracic surgery demonstrated a thickened, hyperemic right middle lung lobe, and thickened pericardial diaphragmatic ligament. Histologic evaluation of these tissues identified a primary pulmonary adenosquamous carcinoma with intravascular and pleural invasion. Based on these cytologic, histologic, and clinical findings, we conclude that primary pulmonary carcinomas may involve superficial thoracic structures and exfoliate into a thoracic effusion.  相似文献   
9.
A multiplex real-time PCR was designed to detect and differentiate equid herpesvirus 1 (EHV-1) and equid herpesvirus 4 (EHV-4). The PCR targets the glycoprotein B gene of EHV-1 and EHV-4. Primers and probes were specific to each equine herpesvirus type and can be used in monoplex or multiplex PCRs, allowing the differentiation of these two closely related members of the Alphaherpesvirinae. The two probes were minor-groove binding probes (MGB) labelled with 6-carboxy-fluorescein (FAM) and VIC for detection of EHV-1 and EHV-4, respectively. Ten EHV-1 isolates, six EHV-1 positive clinical samples, one EHV-1 reference strain (EHV-1.438/77), three EHV-4 positive clinical samples, two EHV-4 isolates and one EHV-4 reference strain (EHV-4 405/76) were included in this study. EHV-1 isolates, clinical samples and the reference strain reacted in the EHV-1 real-time PCR but not in the EHV-4 real-time PCR and similarly EHV-4 clinical samples, isolates and the reference strain were positive in the EHV-4 real-time PCR but not in the EHV-1 real-time PCR. Other herpesviruses, such as EHV-2, EHV-3 and EHV-5 were all negative when tested using the multiplex real-time PCR. When bacterial pathogens and opportunistic pathogens were tested in the multiplex real-time PCR they did not react with either system. The multiplex PCR was shown to be sensitive and specific and is a useful tool for detection and differentiation of EHV-1 and EHV-4 in a single reaction. A comprehensive equine herpesvirus disease investigation procedure used in our laboratory is also outlined. This procedure describes the combination of alphaherpesvirus multiplex real-time PCR along with existing gel-based PCRs described by other authors.  相似文献   
10.
This article presents a historical perspective on veterinary anatomic pathology in the United Kingdom from the late nineteenth century to the present. Prior to World War II, the specialty was a rather general one that also included bacteriology and parasitology and was only slightly affected by strong Germanic developments in cell and tissue pathology. The few notable figures of this era include John McFadyean, Sidney Gaiger, and J.R.M Innes. The specialty developed strongly in the second half of the twentieth century, led by a small number of individuals, and was greatly aided by the development of specialist colleges and residency training. Key individuals of this era include W.F. Blakemore, Ernest Cotchin, R.J.M. Franklin, W.F.H. Jarrett, A.R. Jennings, and A.C. Palmer. A remarkable feature of this period has been the increased employment of veterinary pathologists in biomedical industry and in private diagnostic laboratories. While standards of pathology practice have benefited from the college initiatives, there are major financial constraints on the availability of funded training posts in the United Kingdom, and there remain considerable shortages in the supply of pathologists trained to contemporary standards. The acknowledged professional and scientific importance of veterinary pathology needs to be translated into effective financial support for the training that underpins competence in this specialty. Further developments seem likely to be dominated by advances in the technology of tissue handling, applications of molecular biology to pathology, and greater use of telepathology in teaching, in quality assurance, and in continuing professional development.  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