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   271篇
  免费   18篇
林业   5篇
农学   15篇
基础科学   7篇
  25篇
综合类   14篇
农作物   10篇
水产渔业   23篇
畜牧兽医   164篇
园艺   5篇
植物保护   21篇
  2022年   2篇
  2021年   9篇
  2020年   4篇
  2019年   5篇
  2018年   8篇
  2017年   7篇
  2016年   10篇
  2015年   5篇
  2014年   9篇
  2013年   13篇
  2012年   17篇
  2011年   20篇
  2010年   7篇
  2009年   9篇
  2008年   18篇
  2007年   13篇
  2006年   14篇
  2005年   11篇
  2004年   15篇
  2003年   9篇
  2002年   9篇
  2001年   10篇
  2000年   10篇
  1999年   5篇
  1998年   4篇
  1997年   2篇
  1996年   1篇
  1993年   1篇
  1992年   5篇
  1991年   3篇
  1990年   5篇
  1989年   1篇
  1988年   3篇
  1987年   5篇
  1986年   5篇
  1985年   6篇
  1984年   1篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1967年   1篇
排序方式: 共有289条查询结果,搜索用时 15 毫秒
41.
Strawberry is rich in anthocyanins, which are responsible for the red color, and contains several colorless phenolic compounds. Among the colorless phenolic compounds, some, such as hydroxycinammic acid derivatives, emit blue-green fluorescence when excited with ultraviolet (UV) light. Here, we investigated the effectiveness of image analyses for estimating the levels of anthocyanins and UV-excited fluorescent phenolic compounds in fruit. The fruit skin and cut surface of 12 cultivars were photographed under visible and UV light conditions; colors were evaluated based on the color components of images. The levels of anthocyanins and UV-excited fluorescent compounds in each fruit were also evaluated by spectrophotometric and high performance liquid chromatography (HPLC) analyses, respectively and relationships between these levels and the image data were investigated. Red depth of the fruits differed greatly among the cultivars and anthocyanin content was well estimated based on the color values of the cut surface images. Strong UV-excited fluorescence was observed on the cut surfaces of several cultivars, and the grayscale values of the UV-excited fluorescence images were markedly correlated with the levels of those fluorescent compounds as evaluated by HPLC analysis. These results indicate that image analyses can select promising genotypes rich in anthocyanins and fluorescent phenolic compounds.  相似文献   
42.
Because it is expected to induce cross-reactive serum and mucosal antibody responses, mucosal vaccination against highly pathogenic avian influenza (HPAI) is potentially superior to conventional parenteral vaccination. Here, we tested whether intraocular vaccination with an inactivated AI virus induced protective antibody responses in chickens. Chickens were inoculated intraocularly twice with 104 hemagglutination units of an inactivated H5N1 HPAI virus. Four weeks after the second vaccination, the chickens were challenged with a lethal dose of the homologous H5N1 HPAI virus. Results showed that most of the vaccinated chickens mounted positive antibody responses. The median serum hemagglutination inhibition titer was 1:80. Addition of CpG oligodeoxynucleotide 2006 or cholera toxin to the vaccine did not enhance serum antibody titers. Cross-reactive anti-hemagglutinin IgG, but not IgA, was detected in oropharyngeal secretions. In accordance with these antibody results, most vaccinated chickens survived a lethal challenge with the H5N1 HPAI virus and did not shed the challenge virus in respiratory or digestive tract secretions. Our results show that intraocular vaccination with an inactivated AI virus induces not only systemic but also mucosal antibody responses and confers protection against HPAI in chickens.  相似文献   
43.
GM2 gangliosidosis variant 0 (human Sandhoff disease) is a lysosomal storage disease caused by simultaneous deficiencies of acid beta-hexosaminidase (Hex) A and Hex B due to an abnormality of beta-subunit, a common component in these enzyme molecules, which is coded by the HEXB gene. In the present study, a retrospective diagnosis was performed in 2 previous suspected cases of feline Sandhoff-like disease using a DNA test to detect the causative mutation identified previously in 4 cats in 2 other families of Japanese domestic cats. Enzymic analysis was also performed using stored leukocytes and plasma collected from the subject families in order to investigate the usefulness of enzymic diagnosis and genotyping of carriers. The DNA test suggested that the 2 cases were homozygous recessive for the mutation. Consequently, 6 cats homozygous for the same mutation have been found in 4 separate locations of Japan, suggesting that this mutant allele may be spread widely in the Japanese domestic cat populations. In enzymic analysis, Hex A and Hex B activities in leukocytes and plasma measured using 4-methylumbelliferyl N-acetyl-beta-D-glucosaminide as a substrate were negligible in affected cats, compared with those in normal and carrier cats. However, there was a wide overlap in enzyme activity between normal and carrier cats. Therefore, it was concluded that enzymic analysis is useful for diagnosis of affected cats, but is not acceptable for genotyping of carriers.  相似文献   
44.
In the canine liver with portosystemic shunts (PSS), focal lesions consisting of cells with cytoplasmic brown pigments and lipid vacuoles are often observed in the hepatic parenchyma. Termed lipogranulomas, their histopathological characteristics have been little studied. In the present study, we examined liver biopsy samples from 144 dogs (age: 3 months-16 years; 65 PSS and 79 non-PSS cases), and investigated the histopathological characteristics, incidence, and density of lipogranulomas. Lipogranulomas were detected histopathologically in 55.4% of PSS dogs. The lesions were then grouped into 3 types according to the amount of cytoplasmic lipid vacuoles and brown pigments. The pigments were positive for Berlin blue, PAS, and Sudan black B, but negative with the Hall method. The majority of the cells were immunohistochemically positive for macrophage scavenger receptor, class A (MSR-A), while no cells were positive for hepatocyte-antigen and albumin. The cytoplasmic pigments were recognized as electron-dense microgranular materials by electron microscopy. The incidence of lipogranulomas was significantly higher in the PSS group than non-PSS group when dogs less than 1 year old were excluded. The lipogranuloma density in the liver was significantly higher in the PSS group. It is concluded that lipogranulomas are frequently observed in liver biopsies of canine PSS especially in dogs more than 1 year old. The lesions consisted of Kupffer cells and/or macrophages, and the cytoplasmic brown pigments are ceroid and hemosiderin. The pathogenesis of lipogranuloma in PSS needs to be clarified.  相似文献   
45.
Two cats showing chronic vomiting, diarrhea and weight loss were found to have leukocytosis with marked eosinophilia. Both cats were diagnosed with hypereosinophilic syndrome by the findings of increased eosinophils and their precursors in the bone marrow, eosinophilic infiltration into multiple organs, and exclusion of other causes for eosinophilia. Although cytoreductive chemotherapy with hydroxycarbamide and prednisolone was performed, these two cats died 48 days and 91 days after the initial presentation.  相似文献   
46.
The cover image, by K. Sakai et al., is based on the Original Article Association of tumour‐infiltrating regulatory T cells with adverse outcomes in dogs with malignant tumours, DOI: 10.1111/vco.12383 .

  相似文献   

47.
To investigate the reproductive traits and diel activity ofMonochamus saltuarius, 14 pairs of the adults were reared and observed at each of 20°C and 25°C. Both sexes were more active at 25°C than at 20°C irrespective of the presence or absence of light. A diel change in behavior during 24 h was found on 33% of a total of 48 observations of three age classes of both sexes. No significant difference was found in the mean longevity between sexes or between the two temperature conditions. The time required for reproductive maturation showed no significant difference within the same sex when reared at 20°C and 25°C. The mean oviposition period was significantly longer at 25°C (28.8 days) than at 20°C (12.2 days). The mean lifetime fecundity was significantly greater at 25°C than at 20°C. There was no significant difference in the oviposition ratio (number of eggs deposited/number of oviposition wounds excavated), oviposition rate or hatchability for females between the two temperature conditions.  相似文献   
48.
Limited access to aquatic populations hinders estimation of their status and establishment of effective management measures. We propose a modified surplus production model to cope with this problem. The model provides population parameters and biological reference points from a time series of annual accessible abundance data. Simulation tests showed that the model provided biological reference point estimates with little bias when sufficiently long time series were available. Even for short time series, we could obtain nearly unbiased estimates by providing information on the exploitation rate at the maximum sustainable yield (F MSY). As an application, we fit the modified surplus production model to 7-year accessible biomass estimates of a local population of Japanese spiky sea cucumber Apostichopus japonicus using a Bayesian approach. The results indicated that the stock in the area studied was likely to have experienced recent overfishing and had a high probability of being overfished in the future.  相似文献   
49.
Quantitative correlation between molecular similarity and receptor-binding activity of neonicotinoid insecticides such as imidacloprid and acetamiprid was studied by using a method of similarity index and semi-empirical molecular orbital calculations. A series of compounds having an aromatic ring and a cyclic or acyclic amine moiety with an electron-withdrawing group were subjected to the similarity-activity analysis. Energy-minimum structures and electrostatic properties of the molecules were obtained by MNDO-PM3. The electrostatic similarity of each molecule compared with the most active compounds was found to correlate significantly with the binding activity to nicotinic acetylcholine receptor (nAChR) in honey bee when the two molecules were superimposed to maximize the molecular shape similarity by simplex procedure. This indicates that molecular similarity in terms of electrostatic properties is important for activity, as well as superimposability in terms of molecular shape. A schematic model of interaction between neonicotinoids and nAChR is proposed according to the results of similarity-activity analyses. © 1998 SCI.  相似文献   
50.
ABSTRACT

In this study, the functional components of 19 microalgae and 6 bivalve species were investigated in the context of the application in bivalve feeding and human health food. Principal component analysis was performed to detect any association between the functional components and individual microalgal species or taxonomic group. The proportions of the functional components differed depending on the taxonomic group or species of microalga. The genera Cheatoceros, Thalassiosira, and Isochrysis contained high concentrations of fucosterol and fucoxanthin, which are present in large amounts in brown algae. Diatoms, haptophytes, and eustigmatophytes, which are used as feed for bivalves, were rich in fucosterol and eicosapentenoic acid (EPA); further, haptophytes were rich in docosahexaenoic acid (DHA). In addition, the microalgae associated with red tide, i.e., the raphidophytes, were found to be rich in fucoxanthin, β-sitosterol, and EPA, whereas dinoflagellates were rich in DHA. Seven bivalve species also contained high concentrations of fucosterol, EPA, and DHA, as did microalgae, which were used to feed by bivalves. These results are useful in selecting microalgae effectively as feed of the bivalves.  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