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   115篇
  免费   14篇
农学   4篇
  2篇
综合类   7篇
农作物   6篇
水产渔业   25篇
畜牧兽医   74篇
植物保护   11篇
  2022年   1篇
  2019年   1篇
  2018年   1篇
  2017年   2篇
  2016年   1篇
  2015年   2篇
  2014年   3篇
  2013年   9篇
  2012年   2篇
  2011年   1篇
  2009年   3篇
  2008年   1篇
  2007年   5篇
  2006年   2篇
  2005年   2篇
  2004年   6篇
  2003年   6篇
  2002年   7篇
  2001年   1篇
  2000年   3篇
  1999年   4篇
  1998年   3篇
  1997年   4篇
  1996年   4篇
  1995年   3篇
  1994年   3篇
  1993年   2篇
  1992年   8篇
  1991年   3篇
  1990年   3篇
  1989年   4篇
  1988年   5篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   3篇
  1979年   1篇
  1978年   2篇
  1976年   3篇
  1975年   1篇
  1973年   1篇
  1971年   2篇
  1970年   2篇
  1968年   2篇
  1967年   2篇
  1966年   1篇
排序方式: 共有129条查询结果,搜索用时 31 毫秒
101.
A high degree of virulence diversity has been maintained in the population of Puccinia graminis f. sp. tritici (Pgt) in northwestern United States. Although Berberis vulgaris is present in the region and Pgt has been isolated from aecial infections on B. vulgaris, the population is too diverse to be explained by the limited presence of B. vulgaris alone. Since 2008, we have isolated P. graminis from aecial infections on fruits of Mahonia repens and Mahonia aquifolium from northwestern United States. These two native woody shrub species, widely distributed in western North America, were once classified as resistant to P. graminis based on artificial inoculations. By isolating P. graminis from aecia, we established that M. repens and M. aquifolium along with B. vulgaris (albeit infrequent) serve as the alternate hosts ofP. graminis in the region. The isolates of P. graminis from Mahonia of North America had diverse virulence patterns and most of the isolates could be differentiated on Morocco, Line E, Chinese Spring, Little Club, LMPG-6, Rusty, and other genotypes that are considered to be universally susceptible to most Pgt isolates. This discovery explained the persistence of virulence diversity of Pgt observed in isolates derived from uredinia on cereal crops in the region. In addition to cereal crops, uredinial stage of the P. graminis population is sustained by wild grasses, especially Elymus glaucus, a native grass sharing the same habitat with the rusted Mahonia spp. Although virulence to some important stem rust resistance genes was observed in some isolates derived from Mahonia of North America when tested against single stem rust resistance gene stocks, the overall virulence is very limited in these isolates. This is likely a result of limited selection pressure on the rust population. In contrast to northwestern United Sates, the Pgt population in east of the Rocky Mountains of North America has declined steadily with a single race, QFCSC, being predominant in the last decade. This decline is likely due to a combination of factors, of which a lack of sexual recombination in the region is perhaps the most important one.  相似文献   
102.
Production of shrimp in inland ponds supplied by water from saline aquifers is a potential new aquaculture industry in Alabama. Examination of 2,527 well records of the Geological Survey of Alabama and the United States Geological Survey and samples from 35 wells revealed 238 wells with chloride concentration of 125 mg/L chloride or more in 11 counties of central and west-central Alabama. Chloride concentrations varied from 136 mg/L to 94,000 mg/L. The highest chloride concentrations were from wells in Washington, Choctaw, and Clarke Counties. However, 83% of the saline-water wells in Dallas, Hale, Greene, Marengo, Wilcox, and Sumter Counties were supplied by aquifers of the Eutaw, Gordo, McShan, and undifferentiated Eutaw-McShan formations. Water from these wells had an average and standard deviation of 1,238 ± 615 mg/L chloride. Based on the frequency of saline-water wells, the number of wells with chloride concentrations above 700 mg/L (about 2 ppt salinity), and well depths, it was concluded that Hale, Greene, Marengo, and Sumter Counties have the greatest potential for saline-water aquaculture. Contour maps for chloride concentrations and depths of wells in these four counties were prepared to better delineate this potential water source for aquaculture. There were, however, areas in Lowndes, Tuscaloosa, and Wilcox Counties with saline ground water suitable for inland aquaculture.  相似文献   
103.
OBJECTIVE: To compare a recently developed recombinant MSP-5 competitive inhibition ELISA with a card agglutination test for detection of antibodies to Anaplasma marginale and Anaplasma centrale in Australian cattle. MATERIALS AND METHODS: The ELISA was compared with the card agglutination test using 208 sera from cattle in Anaplasma-free herds, 86 sera from cattle experimentally infected with A marginale or A centrale and 757 sera from cattle in areas endemic for A marginale. RESULTS: The specificity of the ELISA, based on testing 208 sera from cattle in Anaplasma-free areas, was 99.5%, and the sensitivities for detection of antibodies to A marginale and A centrale in sera from the experimentally infected cattle were 98.0% and 100%, respectively. For the same sets of sera, the specificity of the card agglutination test was 98.6% and the sensitivities for detection of antibodies to A marginale and A centrale were 98.0% and 100%, respectively. For the 757 sera collected from cattle in areas endemic for A marginale, the agreement between the ELISA and the card agglutination test depended on the positive threshold selected for the ELISA. The maximum achievable agreement was 91.5% (kappa = 0.73; 95% confidence interval 0.66, 0.79). CONCLUSION: We conclude that the competitive inhibition ELISA is a useful alternative to the card agglutination test for detection of A marginale or A centrale infection in cattle. The assay should be particularly useful for epidemiological applications such as prevalence studies and control programs.  相似文献   
104.
An analytical method has been developed that uses electron capture/gas-liquid chromatography to determine Mirex in serum containing polychlorinated biphenyls (PCBs) (Aroclor 1260). With this method, 0.2 ppb Mirex can be determined in 4 mL serum that also contains 10 ppb PCBs. The method provides approximately 70% recovery of Mirex at 1.0 and 3.5 ppb. The coefficients of variation are 4.5 and 4.6% at 1.0 and 3.5 ppb, respectively. In a cooperative study with the Ohio Department of Health, the Centers for Disease Control used this method to determine the extent of exposure of Salem, OH, residents to Mirex. Confirmation of Mirex was obtained by using high resolution gas chromatography and high resolution mass spectrometry.  相似文献   
105.
Extract

Tuberculosis has been described in seven species of pinnipeds. Based on host preference, phenotype and genetic and antigenic testing, the causal bacterium has been classified as a distinct species, Mycobacterium pinnipedii, within the M. tuberculosis complex. An adult male New Zealand sea lion (Phocarctos hookeri) was found dead on the Otago coastline in mid 2005. Gross necropsy revealed multiple caseous foci throughout the lungs, subcutaneous and thoracic lymph nodes, and mesenteric lymph nodes. Histopathological examination showed granulomatous lesions containing numerous intra-lesional acid fast organisms. The organism was confirmed as being a member of the M. tuberculosis complex, based on restriction enzyme analysis. Spoligotyping is pending. This is the first confirmed case of mycobacterial disease in a New Zealand sea lion.  相似文献   
106.
Abstract

AIM: To determine whether viable Mycobacterium avium subsp. paratuberculosis (Map) is present in skeletal muscle and blood in ewes with and without Johne's disease confirmed histologically.

METHODS: A total of 51 mixed-aged ewes in poor body condition from a farm with a history of clinical Johne's disease were culled and examined at necropsy. BACTEC radiometric culture was performed on samples of skeletal muscle from the biceps femoris, mononuclear cells in peripheral blood (hereafter referred to as blood), and ileum. Histological sections and Ziehl-Neelsen (ZN)-stained impression smears of terminal ileum and mesenteric lymph nodes were examined. Ewes were defined as having confirmed Johne's disease if there was histopathological evidence typical of the disease within the ileum and adjacent lymph nodes.

RESULTS: Eighteen of 21 (86%) ewes with confirmed clinical Johne's disease were culture-positive for Map from sites peripheral to the alimentary tract, comprising 15 from skeletal muscle and 13 from blood. Five of 30 (17%) ewes that did not have Johne's disease were culture-positive, with four from skeletal muscle and one from blood. The likelihood that ewes with confirmed Johne's disease had systemic Map infection compared with ewes without was determined as OR=30 (95% CI=6.3–142.0; p<0.001).

CONCLUSION: The prevalence of Map infection of skeletal muscle and blood in ewes with confirmed Johne's disease was 71% and 62% respectively, and in unaffected ewes was 13% for muscle and 3% for blood.

CLINICAL RELEVANCE: Skeletal muscle and blood are potential sources of exposure of humans to Map, and the risk appears higher from sheep with Johne's disease.  相似文献   
107.
Objective To compare the postoperative analgesic and sedative properties of buprenorphine and morphine in cats. Study Design Prospective, randomized, blinded study. Animals Thirty‐two domestic cats undergoing surgery. Methods Cats received pre‐anaesthetic medication with acepromazine (0.05 mg kg?1) given intramuscularly and were randomly allocated to group M and given morphine (0.1 mg kg?1) intramuscularly (IM) or to group B and given buprenorphine (0.01 mg kg?1) IM. Anaesthesia was induced with propofol and maintained with halothane in oxygen and nitrous oxide. Pain and sedation scores using visual analogue scales, and heart and respiratory rates, were measured immediately before, and 30, 60, 120, 180, 300 and 420 minutes after anaesthesia. Results Pain scores were significantly lower at 60, 120 and 180 minutes after anaesthesia in group B. Group B also had higher heart rates at 30 minutes. There were no other statistically significant differences between the groups. Clinical relevance Buprenorphine (0.01 mg kg?1) appeared to provide better postoperative analgesia than morphine (0.1 mg kg?1) and may also have a longer duration of action.  相似文献   
108.
Mechanisms of recovery from Herpesvirus infections -a review.   总被引:4,自引:1,他引:3       下载免费PDF全文
A variety of specific immunological mechanisms have been shown to be effective at neutralizing herpesviruses or destroying herpesvirus infected cells. These include both humoral and cell mediated immune responses or combinations thereof. Thus, it is genarlly accepted that humoral immunity is probably responsible for preventing reinfection whereas cellular immunity, mediated by T lymphocytes or by the interaction of antibody and Fc receptor bearing cells, is more important in recovery from infections. In addition to these specific responses to herpesvirus infection, a number of nonspecific cellular and humoral components have been shown to inhibit the progression of virus replication and therefore, have been implicated in assisting the host in the recovery process. The various interactions and counteractions between the various nonspecific and specific components of the immune response are discussed with respect to their role in recovery from both primary and recurrent disease as well as how they may eventually be manipulated so as to control herpesvirus recrudescent disease.  相似文献   
109.
SUMMARY A decision analysis model was designed to evaluate the cost effectiveness of a vaccination program for preventing endemic or epidemic porcine parvovirus (PPV) Induced reproductive failure in a 100-sow pig herd. The results showed that the cost of vaccination was less than the cost incurred by continuing endemic PPV infection, or the cost of a severe epidemic. A long term vaccination program is a cost effective method for controlling PPV-induced reproductive failure in pig herds suffering endemic and epidemic PPV infection.  相似文献   
110.
J. Bae  S. H. Jansky  D. I. Rouse 《Euphytica》2008,164(2):385-393
Verticillium wilt (VW) of potato, caused primarily by the fungus Verticillium dahliae, results in yield loss and is therefore an important soil-borne disease. Resistance to VW exists in potato germplasm and is used by breeders during cultivar development. Breeders could make more rapid progress toward the development of VW resistant clones if they had an effective early generation selection strategy. The purpose of this study was to determine whether selection for VW resistance could be carried out in the first tuber generation on single hills. One hundred and fifty-two clones from 19 families were planted as single hills on a V. dahliae-infested field. Each plant was scored for vine maturity, VW symptom expression, yield, stem colonization (colony forming units (cfu), in dried basal stem segments) and incidence (percent infected stems). In the second clonal generation, which consisted of replicated four-hill plots, stem colonization scores and incidence values were used to identify clones which were more resistant than a moderately resistant cultivar and others which were more susceptible than a susceptible cultivar. The efficiency and reliability of the single-hill selection strategy, based on symptoms and yield, was then determined by comparison to the four-hill results. We determined that the best single-hill selection strategy was negative selection (discard clones with the lowest performance) with low stringency, based on yield.  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