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   129篇
  免费   22篇
  国内免费   3篇
林业   8篇
农学   12篇
基础科学   1篇
  11篇
综合类   11篇
农作物   4篇
水产渔业   4篇
畜牧兽医   91篇
园艺   2篇
植物保护   10篇
  2023年   2篇
  2021年   1篇
  2020年   4篇
  2019年   2篇
  2018年   11篇
  2017年   8篇
  2016年   3篇
  2015年   6篇
  2014年   10篇
  2013年   21篇
  2012年   4篇
  2011年   4篇
  2010年   2篇
  2009年   10篇
  2008年   4篇
  2007年   5篇
  2006年   2篇
  2005年   5篇
  2004年   1篇
  2003年   3篇
  2002年   3篇
  2001年   3篇
  2000年   2篇
  1999年   5篇
  1998年   6篇
  1997年   4篇
  1996年   4篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1987年   2篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1974年   1篇
  1966年   1篇
  1963年   1篇
排序方式: 共有154条查询结果,搜索用时 15 毫秒
111.
The present investigation was aimed to study the changes in various physio-chemical attributes in petals of two different rose species, Rosa damascena Mill and Rosa bourboniana Desport differing in flowering behaviour from small bud (stage 1) till full bloom (stage 8). In both rose species fresh weight, dry weight and moisture content were maximum during full bloom. Electrical conductivity of the petal diffusates reached maximum at full bloom with significantly higher values in R. damascena. In both the species, starch content declined as the flower reached its full bloom stage with maximum reducing sugar content during this period. With progressive increase in petal growth, total protein and RNA declined. The results showed that in both the species peroxidase (POX) and catalase (CAT) activity were lower during full bloom with high activity of invertase and lipoxygenase (LOX) at this period. The present study indicates that lipid peroxidation induced membrane permeability could partly be the result of higher lipoxygenase activity during full bloom. The possible significance of these findings is discussed in relation to flower development in the two diverse rose species.  相似文献   
112.
113.
The activity of protease(s) was observed separately in cytosolic and membrane-bound protease(s) from male and female Hae monchus contortus (Nematoda: Trichostrongylidae). Different fractions showed optimum protease activity at 37 degrees C, pH 8.5 and 8.0 mg casein concentration. The female fractions had a particularly high activity of protease(s) in comparison with the male fractions, especially of membrane-bound enzymes in the anterior half. Inhibition, activation studies revealed the presence of four kinds of protease(s) in cytosolic and membrane-bound fractions. Protease(s) in different fractions are purified to a greater extent by higher concentrations of saturated ammonium sulphate solution, i.e. ranging from 50 to 65%. The purification study revealed the presence of multiple forms of protease(s) in cytosolic and membrane-bound extracts of H. contortus.  相似文献   
114.
Chlamydia gallinacea is a recently described bacterial species in a genus known to infect and cause disease in animals and humans. Our report describes the identification of C. gallinacea infection in free‐range laying chickens (Gallus gallus) in Australia, and the identification of C. gallinacea infection in a parrot, a wild Australian galah (Eolophus roseicapillus). There is currently little knowledge of the effects of C. gallinacea infection on avian hosts, but it has been linked to respiratory disease in humans and could potentially cause similar disease in other species. Our report highlights the need for further study and surveillance of Chlamydia species in both wild and domestic hosts in Australia.  相似文献   
115.
The aim of this study was to develop a competitive inhibition ELISA (CI-ELISA) for detection of antibodies to bovine viral diarrhea virus (BVDV) using the helicase domain of NS3 (non-structural) protein and monoclonal antibody (MAb) against it and to estimate its sensitivity and specificity using two commercial ELISA kits as independent references. The 45-kDa helicase domain of NS3 protein of BVDV was expressed in Escherichia coli and 18MAbs were developed against it. MAb-11G8 was selected for use in CI-ELISA on the basis of maximum inhibition (90%) obtained with BVDV type 1 infected calf serum. Based on the distribution of percent inhibition of known negative sera (n=166), a cut-off value was set at 40% inhibition. In testing 914 field serum samples of cattle (810) and buffaloes (104), the CI-ELISA showed a relative specificity of 95.75% and 97.38% and sensitivity of 96% and 94.43% with Ingenesa kit and Institut Pourquier kit, respectively. This study proved that the use of helicase domain of NS3 (45-kDa) is equally good as the whole NS3 protein (80-kDa) used in commercial kits for detection of BVDV antibodies in cattle and buffaloes.  相似文献   
116.
The aim of this study was to examine foetal organs and placental tissue to establish a correlation between the changes in the composition of these structures associated with their maturation and the ultrasonographic characteristics of the images. Twenty‐four pregnant ewes were included in the study. Ultrasonography assessments were performed in B‐mode, from the ninth gestational week until parturition. The lungs, liver and kidneys of foetuses and placentomes were located in transverse and longitudinal sections to evaluate the echogenicity (hypoechoic, isoechoic, hyperechoic or mixed) and echotexture (homogeneous and heterogeneous) of the tissues of interest. For quantitative evaluation of the ultrasonographic characteristics, it was performed a computerized image analysis using a commercial software (Image ProPlus®). Mean numerical pixel values (NPVs), pixel heterogeneity (standard deviation of NPVs) and minimum and maximum pixel values were measured by selecting five circular regions of interest in each assessed tissue. All evaluated tissues presented significant variations in the NPVs, except for the liver. Pulmonary NPVmean, NPVmin and NPVmax decreased gradually through gestational weeks. The renal parameters gradually decreased with the advancement of the gestational weeks until the 17th week and later stabilized. The placentome NPVmean, NPVmin and NPVmax decreased gradually over the course of weeks. The hepatic tissue did not show echogenicity and echotexture variations and presented medium echogenicity and homogeneous echotexture throughout the experimental period. It was concluded that pixels numerical evaluation of maternal‐foetal tissues was applicable and allowed the identification of quantitative ultrasonographic characteristics showing changes in echogenicity related to gestational age.  相似文献   
117.
Highly pathogenic avian influenza viruses (HPAIV) of H5N1 subtype are a major global threat to poultry and public health. Export of poultry products, such as chicken and duck meat, is a known source for the cross‐boundary spread of HPAI H5N1 viruses. Humans get infected with HPAI H5N1 viruses either by close contact with infected poultry or through consumption of fresh/undercooked poultry meat. Skeletal muscle is the largest soft tissue in chicken that has been shown to contain virus during systemic HPAIV infection and supports productive virus infection. However, the time between infection of a chicken with H5N1 virus and presence of virus in muscle tissue is not yet known. Further, it is also not clear whether chicken infected with low doses of H5N1 virus that cause non‐fatal subclinical infections continue to accumulate virus in skeletal muscle. We investigated the amount and duration of virus detection in skeletal muscle of chicken experimentally infected with different doses (102, 103 and 104 EID50) of a HPAI H5N1 virus. Influenza viral antigen could be detected as early as 6 hr after infection and live virus was recovered from 48 hr after infection. Notably, chicken infected with lower levels of HPAI H5N1 virus (i.e., 102 EID50) did not die acutely, but continued to accumulate high levels of H5N1 virus in skeletal muscle until 6 days post‐infection. Our data suggest that there is a potential risk of human exposure to H5N1 virus through meat from clinically healthy chicken infected with a low dose of virus. Our results highlight the need to implement rigorous monitoring systems to screen poultry meat from H5N1 endemic countries to limit the global spread of H5N1 viruses.  相似文献   
118.
Sugarcane is one of the most important crops in the tropical and sub-tropical regions worldwide because it supplies over half of the world’s sugar. The main goal of sugarcane breeding programs is releasing new cultivars with improved sugar content, disease resistance and agronomic traits. Molecular markers linked to the sugar yield would greatly facilitate the development of sugarcane cultivars with higher sugar content. In this study, quantitative trait loci (QTL) associated with sugar and yield related traits were identified using a segregating F1 population derived from two Saccharum spp. hybrids. Specifically, BRIX, POL, recoverable sugar content (SC), fiber content (FC), moisture content (MC), juice purity, stalk diameter (SD), and stalk weight (SW) data were collected from a replicated field trial of a bi-parental population. A total of 36 and nine QTL for sugar and yield related traits, respectively were identified using a high density genetic map with markers developed by genotyping-by-sequencing. Of the 45 detected QTL, seven QTL were associated with each of the three sugar related traits BRIX, POL, and SC; six QTL with FC and MC; three QTL with juice purity; four QTL with SD; and five QTL with SW. The QTL explained a total of phenotypic variations of 70.90, 61.80, 61.68, 68.67, 91.62, 33.00, 49.91, and 64.49% for BRIX, POL, SC, FC, MC, purity, SD, and SW, respectively. Upon validation, markers from the identified QTL would be useful in marker-assisted selection for selecting superior cultivars with these traits.  相似文献   
119.
OBJECTIVES: To determine the prevalence of Toxoplasma gondii in a population of domestic cats in Melbourne. DESIGN: An ELISA assay was used to measure T gondii antibody titres in 103 cats from north-eastern Melbourne. Cats were obtained from outer suburban areas (less than 30 km from the Melbourne GPO) and from rural areas (more than 30 km from the Melbourne GPO). RESULTS: Thirty-nine percent of cats were positive for T gondii IgG. Older cats tended to have higher antibody titres. There was no significant difference in the T gondii antibody titres between males and females, or between cats living in urban areas and cats from rural areas. CONCLUSIONS: A significant proportion of cats from Melbourne have been exposed to Toxoplasma. This may have implications for the health of wildlife and humans.  相似文献   
120.
Viral encephalopathy and retinopathy disease caused by betanodavirus, genus of the family Nodaviridae, affects marine, wild and farmed species including sea bass, one of the most important farmed species in Europe. This work describes a reliable and sensitive indirect ELISA assay to detect betanodavirus in biological samples using a polyclonal antiserum (pAb 283) against the 283/I09 virus strain, the most common red‐spotted grouper nervous necrosis virus (RGNNV) genotype in the Mediterranean area, and a capture‐based ELISA using a monoclonal antibody (mAb 4C3) specific to a common epitope present on the capsid protein. Using adsorbed, purified VERv preparation, the detection limit of indirect ELISA was 2 μg mL?1 (3 × 105 TCID50 per mL), whereas for capture‐based ELISA, the sensitivity for the antigen in solution was 17 μg mL?1 (35 × 105 TCID50 per mL). The capture‐based ELISA was employed to detect VERv in brain homogenates of in vivo infected sea bass and resulted positive in 22 of 32 samples, some of these with a high viral load estimates (about 1.1 × 108 TCID50 per mL). The ELISA system we propose may be helpful in investigations where coupling of viral content in fish tissues with the presence of circulating VERv‐specific IgM is required, or for use in samples where PCR is difficult to perform.  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