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   172篇
  免费   35篇
林业   2篇
农学   1篇
基础科学   4篇
  6篇
综合类   17篇
农作物   3篇
畜牧兽医   168篇
园艺   1篇
植物保护   5篇
  2018年   2篇
  2016年   2篇
  2015年   6篇
  2014年   5篇
  2013年   5篇
  2012年   9篇
  2011年   11篇
  2010年   7篇
  2009年   10篇
  2008年   10篇
  2007年   8篇
  2005年   8篇
  2004年   3篇
  2003年   6篇
  2002年   5篇
  2001年   1篇
  2000年   2篇
  1999年   3篇
  1998年   4篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1992年   5篇
  1991年   5篇
  1990年   5篇
  1989年   4篇
  1988年   3篇
  1987年   6篇
  1986年   6篇
  1985年   7篇
  1983年   3篇
  1982年   3篇
  1981年   3篇
  1980年   2篇
  1979年   3篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
  1975年   2篇
  1974年   1篇
  1973年   7篇
  1972年   6篇
  1971年   2篇
  1970年   2篇
  1969年   2篇
  1968年   2篇
  1967年   3篇
  1966年   1篇
  1938年   1篇
排序方式: 共有207条查询结果,搜索用时 250 毫秒
1.
Three commonly used keratin monoclonal antibodies (MAB)--AE1:AE3, CAM 5.2, and MAK-6--were compared with routinely used cytokeratin antibody. The expression of these antibodies was analyzed in several tissues obtained from clinically normal dogs and in a variety of neoplasms from dogs. Using appropriate enzymatic digestion, paraffin-embedded tissues processed in routine manner retained their typical keratin expression. Differentiated and poorly differentiated epithelial neoplasms, lymphomas, and melanomas were studied by use of the avidin-biotin-peroxidase technique. All 4 of the aforementioned antibodies had similar staining profiles. Of 3 anaplastic carcinomas, 2 had positive reaction to all 4 antibodies. All lymphomas, plasma cell tumors, and amelanotic melanomas had negative reaction to MAK-6, CAM 5.2, AE1:AE3, and cytokeratin MAB. Three basal cell epitheliomas had positive reaction to all 4 antibodies, whereas 1 basal cell tumor with a solid pattern had negative staining reaction. Two carcinoids had negative reaction to all markers and 1 of 2 malignant chemodectomas and 1 transitional cell carcinoma had staining reaction to only AE1:AE3 MAB. Comparing the 4 antibodies, use of AE1:AE3 MAB produced the strongest staining intensity followed by cytokeratin, MAK-6, and CAM 5.2 MAB. All 4 antibodies had low background staining. In conclusion, AE1:AE3 and MAK-6 MAB are as useful as cytokeratin MAB for identification of poorly differentiated epithelial neoplasms in dogs and cats.  相似文献   
2.
Post-weaning Escherichia coli diarrhea (PWECD) in Ontario was investigated using a case-control study involving 50 Ontario nurseries. The clinical signs and the impact on productive parameters were determined by means of a producer survey. The hemolytic E. coli serogroups involved in PWECD (O149:K91:K88) were examined in this study. Based on a polymerase chain reaction test, the hemolytic E. coli from 82% of the case herds were positive for 3 enterotoxins (STa, STb, and LT), those from 12% of the case herds were positive for STb and LT only, and those from one herd (6%) were positive for 3 enterotoxins, as well as for verotoxin and F18 pili. The E. coli involved in disease were resistant to multiple antibiotics. Case farms commonly used a wide variety of antibiotics either in the feed or water, or as injectable drugs. The most common antibiotic used to treat PWECD on the study farms was apramycin, but evidence of resistance to this antibiotic was noted. The PWECD problem was commonly seen within a week of weaning but onset of diarrhea was reported as late as the grower-finisher stage. Growth rate was poorer in case herds and mortality was higher than in control herds, demonstrating that PWECD is an economically important disease in Ontario.  相似文献   
3.
4.
Summary Effects of weekly (W) and fortnightly (F) irrigation schedules on established stands of lucerne (Medicago sativa L.) grown on gypsum treated (G) and untreated (C) heavy clay soil were investigated. Two irrigations were applied under the fortnightly regime and four under the weekly schedule during a single cutting cycle. Growth and light interception were measured during both the vegetative and mature phases of growth.Leaf expansion, light interception and dry matter production were greater under treatments W G and W C, with yield increasing from 3.4 t ha–1 under the fortnightly schedule to 5.0 t ha-1 with weekly irrigation. Gypsum treatment was effective under the more frequent irrigation schedule. Specific leaf area and the proportion of stem were both increased by treatments W G and W C. The responses to irrigation were therefore characteristic of those elicited by a more favourable plant moisture status. Growth was analysed in terms of light interception, the efficiency of utilisation of intercepted light, the proportion of the daily dry matter gain retained by the leaves and leaf expansion. The analysis demonstrated that impaired leaf expansion contributed to a decline of approximately 15% in yield, and that impaired efficiencies of utilisation of intercepted light contributed to losses of approximately 30% under the less frequent irrigation schedule.A comparison of growth rates and efficiencies of energy conversion with published data showed that satisfactory rates of growth and levels of productivity were achieved on the heavy soils of the local region using gypsum treatment and the more frequent irrigation schedule.  相似文献   
5.
Rice culture of a toxigenic strain of Aspergillus ochraceus was fed at a concentration of 25% to weanling pigs for 10 days. The clinicopathological abnormalities reflected renal damage. Activities of lactic dehydrogenase, glutamic-oxaloacetic transaminase and isocitrate dehydrogenase were increased in the urine but not in the serum. Serum concentrations of urea nitrogen and creatinine were high. Cellular and granular casts, blood, protein, and glucose were in the urine of pigs fed toxic diet. Serum concentrations of K+, Na+ and Cl- were unchanged, but concentrations of these electrolytes were reduced in the urine.  相似文献   
6.
Ochratoxicosis in Beagle dogs. II. Pathology   总被引:2,自引:0,他引:2  
  相似文献   
7.
8.
Experimental aflatoxicosis in young swine   总被引:1,自引:0,他引:1  
  相似文献   
9.
ABSTRACT Hydathodes of tomato leaves served as extremely efficient infection courts for the bacterial canker pathogen, Clavibacter michiganensis subsp. michiganensis. Chlorotic lesions developed at the tips of leaflet lobes about 2 weeks after inoculation of guttation droplets. Lesions expanded along the leaflet margins and became necrotic. Movement of C. michiganensis subsp. michiganensis from the inoculated leaflet into the rachis was slow and erratic. Histological observations revealed that pathogen populations first developed within large intercellular spaces lying beneath the stomata, which serve as water pores in tomato hydathodes. Bacteria were first observed within vessels of the large marginal fimbriate veins 7 days after inoculation. By 14 days after inoculation, large populations could be seen within the vessels; and by 21 days after inoculation, tissue collapse was widespread and masses of bacteria could be seen in the intercellular spaces and within necrotic cells.  相似文献   
10.
Linkages among genes for production of Escherichia coli heat-stable enterotoxin (ST), drug resistance, K99 antigen, and colicin were investigated in 2 bovine and 3 porcine strains of enterotoxigenic E coli. In conjugation experiments, all 5 isolates transferred enterotoxigenicity and the ability to produce K99; 4 of the 5 isolates also transferred antibiotic resistance markers, and 3 colicinogenic strains transmitted the ability to produce colicin. In 2 of the 3 colicin-producing strains, the genes for colicin were located along with those for K99 and ST on a single plasmid. One of these 2 strains transferred the genes for tetracycline resistance and production of both mouse-active ST (STa) and mouse-inactive ST, whereas the other transmitted the gene(s) for STa only. Transformation studies with the 3rd strain revealed that the K99 determinant resided on a 22-megadalton (Mdal)R plasmid, and that STa and colicin production were on a 65-Mdal plasmid. Analysis of the plasmids from the transformation experiments revealed that the larger plasmid was conjugative and the smaller plasmid was nonconjugative; stable cointegrate formation occurred between these 2 plasmids. Genetic information coding for the production of STa and K99 were also present on a single plasmid of approximately 80 Mdal in both noncolicinogenic strains.  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