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   811篇
  免费   40篇
林业   117篇
农学   12篇
基础科学   2篇
  212篇
综合类   74篇
农作物   22篇
水产渔业   22篇
畜牧兽医   330篇
园艺   9篇
植物保护   51篇
  2021年   12篇
  2020年   13篇
  2019年   11篇
  2018年   12篇
  2017年   20篇
  2016年   11篇
  2015年   13篇
  2014年   27篇
  2013年   51篇
  2012年   36篇
  2011年   54篇
  2010年   23篇
  2009年   22篇
  2008年   50篇
  2007年   46篇
  2006年   39篇
  2005年   37篇
  2004年   36篇
  2003年   38篇
  2002年   20篇
  2001年   20篇
  2000年   13篇
  1999年   20篇
  1998年   7篇
  1997年   6篇
  1996年   5篇
  1995年   7篇
  1993年   8篇
  1991年   6篇
  1990年   7篇
  1989年   9篇
  1988年   5篇
  1987年   9篇
  1986年   8篇
  1985年   6篇
  1984年   7篇
  1983年   4篇
  1981年   4篇
  1978年   4篇
  1976年   7篇
  1975年   4篇
  1973年   4篇
  1972年   6篇
  1971年   5篇
  1970年   6篇
  1969年   4篇
  1966年   8篇
  1965年   7篇
  1935年   4篇
  1932年   5篇
排序方式: 共有851条查询结果,搜索用时 562 毫秒
1.
Twenty‐nine Staphylococcus sciuri strains isolated from free‐living insectivores and rodents were comparatively analysed for their biochemical capacities and their SmaI macrorestriction patterns. The 29 S. sciuri isolates represented 21 different biotypes and 22 different SmaI macrorestriction types. This observation confirmed that S. sciuri isolates obtained from insectivores and rodents living in natural environments constituted a heterogeneous population. Cluster analysis revealed that the macrorestriction patterns and the biochemical profiles matched in some cases. However, S. sciuri isolates that exhibited the same or closely related biochemical profiles were also found to be associated with different macrorestriction patterns. Analysis of the 29 S. sciuri isolates for their plasmid content and their sensitivity to antimicrobial agents showed that most of the isolates were plasmid‐free and susceptible to all antimicrobial agents tested.  相似文献   
2.
Staphylococcus hyicus-cultures, isolated from piglets and cattle with skin lesions were investigated for their plasmid content and their resistance to antimicrobial agents and heavy metals. Several plasmids of different sizes could be detected in most of the 32 "porcine" S. hyicus-isolates, whereas none of the 20 "bovine" S. hyicus-cultures possessed any plasmid. The "porcine" S. hyicus-isolates were much more resistant to antimicrobial substances than the "bovine" S. hyicus-cultures. However, the "porcine" and "bovine" S. hyicus-cultures did not differ in their resistance to heavy metals.  相似文献   
3.
A small chloramphenicol resistance (Cm) plasmid of 4.65 kB could be detected in an "equine" Staphylococcus sciuri-culture. This plasmid, designated as pSC3, was identified by interspecific protoplast transformation. On the basis of restriction endonuclease analyses a detailed restriction map of pSC3 could be constructed. This allowed structural comparisons of pSC3 with Cm-plasmids of other staphylococcal species from infections of humans and animals and identification of pSC3 as a member of the pC 221-family of staphylococcal Cm-plasmids. The pSC3-plasmid encoded an inducible chloramphenicol acetyltransferase as confirmed by enzymatic assays. This enzyme could be demonstrated in cell-free lysates of Cm-induced pSC3-transformants.  相似文献   
4.
A total of 33 Staphylococcus hyicus-cultures from piglets with exudative epidermatitis were analyzed for the presence of antibiotic resistance plasmids. Four small plasmids encoding resistances to chloramphenicol, macrolide-lincosamide-antibiotics, streptomycin or tetracyclines could be identified in plasmid-curing and plasmid-transformation experiments. For further characterization these plasmids were digested with restriction endonucleases. This led to the construction of a specific restriction map for each of the 4 plasmids. On the basis of their restriction maps, these 4 antibiotic resistance plasmids from "porcine" S. hyicus-cultures were compared with the respective resistance plasmids of other staphylococcal species from infections of humans and animals.  相似文献   
5.
6.
7.
8.
OBJECTIVE: To evaluate the use of computed tomography (CT) for detection of pneumonia in snakes. ANIMALS: 8 clinically normal Indian pythons (Python molurus) and 5 pythons with evidence of respiratory tract disease. PROCEDURES: Preliminary examinations (clinical examination, conventional radiography, and microbiologic examination of a transtracheal wash sample) were performed. The lungs of each snake were then examined by use of CT performed in accordance with a standardized protocol. Structures of the lungs were assessed, and thickness and attenuation of the parenchyma were determined. RESULTS: It was possible to assess lung parenchyma in all pythons. Mean +/- SD attenuation in healthy pythons was -744.4 +/- 47.1 Hounsfield units. Significant differences were not evident between the right and left lungs or among measurement areas within a lung. In all Indian pythons with clinical signs of dyspnea and microbiologic detection of pathogens, hyperattenuation of the alveolar tissue was evident. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of the results revealed the benefit of CT for use in the diagnosis of pneumonia in snakes. A standardized protocol and reference values were established as a basis for CT assessment of the lungs of snakes.  相似文献   
9.
At the Institute of Animal Nutrition of the Federal Agricultural Research Centre (FAL) in Braunschweig a feeding trial with 30 first lactating cows (German Holstein) was realised in 2004 for a complete lactation. All animals received a diet based on maize- and grass-silage ad libitum at the rate of 60:40 (DM-base) and concentrate depending on their milk yield.The animals were fed with energy and protein as recommended (GfE 2001) and were kept in loose housing. After calving they were split randomly into two feeding groups with 15 animals each. Group 1 was fed a concentrate according to the recommendations of the GfE (2001), whereas group 2 was offered the same concentrate with roughly the double amount of calcium, magnesium, phosphorus, copper, zinc, beta-carotene and vitamins A and E. To study the influence of the different concentrates on the serum concentrations of minerals and vitamins, blood, feed and milk samples were regularly taken and analysed in the course of lactation. Significantly higher blood concentrations were detected for phosphorus, zinc and vitamin E in group 2, but therefore a direct influence of the feeding on the blood concentrations was detected only for zinc and vitamin E. Over the whole lactation the average milk yield of group 1 was 2.6 kg/day higher and the average milk fat content was reduced about 0.6 percent points compared to group 2.  相似文献   
10.
A total of 417 isolates of Escherichia coli collected from five animal species/organ system combinations from swine [urinary/genital tract (UGT) incl. mastitis metritis agalactia syndrome], horses [genital tract (GT)] and dogs/cats [respiratory tract (RT), UGT and gastrointestinal tract (GIT)] were analysed quantitatively for their susceptibility against different antimicrobial agents by determination of minimum inhibitory concentrations. Regardless of which animal species the strains originated from, resistance appeared most frequently against sulfamethoxazole (18-59%), tetracycline (14-54 %), and ampicillin (14-39%). High percentages of intermediate isolates were observed for cephalothin (39-46 %). In general, low prevalences of resistance were detected for amoxicillin/clavulanic acid (1-4%), gentamicin (1-9%), and cefazolin (0-11%). Generally speaking, the antimicrobial resistance situation among E. coli isolates from horses and small animals is relatively good.  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