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   777篇
  免费   65篇
  国内免费   61篇
林业   16篇
农学   16篇
基础科学   2篇
  23篇
综合类   257篇
农作物   49篇
水产渔业   94篇
畜牧兽医   371篇
园艺   5篇
植物保护   70篇
  2024年   5篇
  2023年   13篇
  2022年   32篇
  2021年   55篇
  2020年   58篇
  2019年   55篇
  2018年   30篇
  2017年   47篇
  2016年   34篇
  2015年   40篇
  2014年   53篇
  2013年   49篇
  2012年   43篇
  2011年   42篇
  2010年   51篇
  2009年   38篇
  2008年   28篇
  2007年   40篇
  2006年   37篇
  2005年   27篇
  2004年   21篇
  2003年   10篇
  2002年   16篇
  2001年   14篇
  2000年   14篇
  1999年   8篇
  1998年   4篇
  1997年   6篇
  1996年   5篇
  1995年   7篇
  1994年   2篇
  1993年   1篇
  1992年   2篇
  1991年   4篇
  1990年   2篇
  1988年   1篇
  1987年   1篇
  1982年   1篇
  1979年   2篇
  1977年   1篇
  1976年   1篇
  1956年   2篇
  1955年   1篇
排序方式: 共有903条查询结果,搜索用时 142 毫秒
71.
Antibiotic resistance is a major emerging global public health threat. Farmers in the Khartoum state are believed to misuse antibiotics in animal farming leading to daily exposure to resistant bacteria and antibiotic residues. Hence, farmers are at potential risk exposure to bacteria, zoonotic infection and toxicity. We hypothesized that farmers' misuse of antibiotics could be due to their ignorance of the importance of optimal use of antibiotics, the potential health hazards and the economical waste associated with antibiotic misuse practices. In the present study, we investigated knowledge and practices among farmers regarding antibiotic use and resistance. For this purpose, a cross-sectional study was conducted in Khartoum state where data were collected from 81 farmers using structured interviews. Data were analysed both quantitatively and qualitatively. Fifty-two per cent of farmers were uneducated or had studied for < 6 years. The majority reported antibiotic use for treatment and prevention while only 5% stated use for growth promotion. Antibiotic group treatment for both sick and healthy animals was commonly practiced among most farmers. The most commonly used group of antibiotics was the quinolones, which was reported by one-third. Only 30% of the farmers had heard of antibiotic resistance and provided their definition. Almost half were not aware of the commonly transferred zoonotic infections between humans and animals. The farmers consume 1-2 meals/day from their own farm products. A significant association between low education, poor knowledge of farmers on antibiotic use, antibiotic resistance and zoonotic infections was found. This association may play a vital role in the present practiced misuse of antibiotics. Our findings on farmers' practices could be used as baseline information in defining the gaps related to antibiotic use and resistance in animal farming in Sudan. It can thus serve as a foundation for future interventions.  相似文献   
72.
通过对TTC法中指示菌株嗜热链球菌的分离及分离菌抗生素敏感性的分析,对57份不同来源、不同品牌的牛乳样中抗生素残留进行了检测。结果表明,分离菌对氨苄西林(AMP)耐药;12份牛乳样有抗生素残留,2份乳样可疑;指示菌的耐药性对牛乳中抗生素残留的检测有影响。  相似文献   
73.
蚯蚓抗菌的免疫生态学机制   总被引:1,自引:0,他引:1       下载免费PDF全文
 蚯蚓具有独特的抗菌免疫防御体系,论文从蚯蚓的防御屏障、蚯蚓的细胞免疫和蚯蚓的体液免疫三个方面对蚯蚓的免疫防御体系进行了综述。  相似文献   
74.
研究卡那霉素、潮霉素、头孢霉素和羧苄青霉素对剑麻愈伤组织生长、不定芽分化及生根的影响,并确定抑制农杆菌生长的头孢霉素、羧苄青霉素的质量浓度。结果表明:潮霉素明显抑制剑麻愈伤组织生长和不定芽分化,卡那霉素次之,头孢霉素和羧苄青霉素相对较小;4种抗生素均能抑制剑麻生根,其抑制效果依次为头孢霉素>卡那霉素>羧苄青霉素>潮霉素。头孢霉素和羧苄青霉素的浓度大于200 mg/L时,农杆菌生长完全被抑制。在筛选剑麻转化体时,卡那霉素和潮霉素的使用浓度分别以100、50 mg/L为宜,羧苄青霉素和头孢霉素的使用浓度均为200 mg/L。  相似文献   
75.
Pseudomonas aeruginosa represents an opportunistic pathogen for animals and humans that is often associated with high disease morbidity and, at times, mortality. Captive reptiles have been shown to be reservoirs of P. aeruginosa strains that can be sources of exposure to humans that come in contact with these animals. In this study, the prevalence of P. aeruginosa among subclinical captive reptile species and the antimicrobial sensitivity of bacterial isolates were investigated. Sixty-five oral swabs were collected from captive reptiles belonging to 15 different species in which no overt signs of disease were evident. From this group of animals, 46 (70.8%) isolates were identified as P. aeruginosa. All of the P. aeruginosa strains were shown to have a wide range of antibiotic resistance. At present, there is a paucity of data regarding the prevalence of P. aeruginosa in various reptile species; therefore, continued scientific investigations are indicated to determine the significance of P. aeruginosa infection as it relates to captive reptile species.  相似文献   
76.
Summary

Cellular changes in spleens of mature fowl in relation to both the primary and secondary humoral antibody response following experimentalEDS'76 virus infection were studied. The influence of splenectomy on humoral antibody response was also examined.

Experimental fowl had been naturally infected with fowl adenovirus (FAV) but did not possess precipitins to these viruses at the time of EDS’ 76 virus infection. Since EDS'76 infection provokes a recall of the group antibody to FAV, this infection simultaneously induces a primary response against EDS’ 76 virus and a secondary response due to the recall of the group antibody to FAV.

HI and precipitating antibodies toEDS'76 virus (primary response) werefirst detected at 6 and 8 days p.i. respectively. Curves of HI, precipating and neutralising antibody titres were biphasic; the first peak (IgM peak) occurred at 10–11 days p.i., the second (IgG peak) at 16–28 days p.i.

Precipitating antibodies to FAV (secondary response) were demonstrated from 4 days p.i. The curve of these antibody titres was also biphasic, with peaks at the same times as in the primary response.

Based on HI and AGP testing of primary and secondary immune response in both splenectomised and non‐splenectomised fowl it is concluded that in the primary response the spleen of the adult fowl is involved significantly in only IgM secretion, while in the secondary response it is likely that bothIgM and IgG are secreted in considerable amounts.

Clusters of lymphoblasts and plasmablasts were observed at 3 days p.i. in the red pulp. It is very likely that antigen‐antibody complexes are formed from that time and circulate bound to the surface of lymphocytes. These antigen‐loaded lymphocytes are ‘picked up’ from the blood stream by

– red pulp macrophages, leading to enhanced formation of lymphoblasts in the red pulp. Great numbers of these cells (which are very probably IgM secreting cells) were present on days 6 and 7 p.i., but were no longer detectable after day 10 p.i.

– macrophages of the macrophagalellipsoidal corona (MEC), leading to significant enlargement of the periellipsoidal lymphoid tissue(PELT) by an increase of the number of lymphocytes observedfrom days 4–12 p.i. The MEC was significantly enlarged from 7–12 days p.i., very likely due to an increased number of macrophages.

Following deposition of antigen in the white pulp, formation of follicles begins. The number of small, intact follicles includingfollicle precursors increasedfrom 6 days p.i. From 15 days p.i. to the end of the experiment both the number and size of follicles increased significantly.

Uptake and processing of antigen by macrophages is probably accompanied by death of some of these cells. This might explain the degenerative changes observed in large mesenchymal cells, probably macrophages, at 3 and 5 days p.i. in the red pulp and at 5 and 6 days especially in the MEC. Splenitis which was present at 3 and 5 days p.i. and oedema observed in and around ellipsoidal cells at 5 days p.i. may be due to mediators released from these degenerative macrophages.

A significantly increased number of follicles with lymphoblasts was seen from 2–15 days p.i. while lymphoblasts and plasmablasts were present in the PELT from 5–15 days p.i., but predominantly at 6 and 7 days p.i. It is likely that disruption of follicles and blast transformation of white pulp lymphoid cells are secondary response events. White pulp lymphoblastsand plasmablastsare probably IgG secreting cells.

Splenomegaly was observed at 3, 5 and 6 days after infection and was mainly due to swelling of red pulp macrophages and infiltration of granulocytes in the red pulp. Ellipsoidal and periellipsoidal changes could contribute to the splenomegaly at 5 and 6 days p.i.  相似文献   
77.
78.
采用"粉末炭活性污泥法+Fenton试剂"强化处理抗生素生产废水,与"普通活性污泥法"进行了对比试验。结果表明:"普通活性污泥法"处理抗生素生产废水后有机污染物COD平均浓度为759mg/L,平均去除率89.1%,达不到该药厂废水排放标准,而"粉末炭活性污泥法+Fenton试剂"强化处理抗生素生产废水后有机污染物COD平均浓度186mg/L,平均去除率为97.3%,完全达到该药厂排放标准。  相似文献   
79.
Abstract

AIM: To describe the patterns of use of antimicrobial drugs by veterinary surgeons treating commonly presented bacterial infections in companion animals in New Zealand.

METHODS: A postal survey of 800 randomly selected companion animal veterinarians practicing in New Zealand was conducted between August and December 2008. Data were collected regarding the antimicrobials prescribed for recent cases of skin, ear and urinary tract infections; the use of culture and susceptibility testing; and veterinarian characteristics such as proportion of time spent treating companion animals and recent attendance at continuing professional development (CPD) events. Potential associations within the data were explored using extended mosaic plots and multivariable regression models.

RESULTS:Completed surveys from 393 respondents were available for analysis, providing data on systemic antimicrobial drug use for 1,799 cases of presumptive bacterial infections. The most frequently prescribed drugs were amoxicillin-clavulanic acid (864 cases, 48%), cephalexin (558, 31%), and fluoroquinolones (198, 11%). Of 359 cases of canine superficial pyoderma, 157 (44%) were treated with amoxicillin-clavulanic acid and 155 (43%) were treated with cephalexin with median reported treatment durations of 7 and 10 days, for these two drugs respectively. Culture and susceptibility tests had been used in 376 of 1,984 (19%) of all reported cases and 160 (43%) of these were suspected urinary tract infections. Practitioners that spent 100% of their time treating companion animals and who had attended a CPD course related to companion animals within the 12 months prior to completing the survey were more likely to submit a sample for culture and susceptibility testing and to prescribe longer courses of antimicrobials for the treatment of canine pyoderma than practitioners who spent less than 100% of their time treating companion animals and had not attended a CPD course in the last 12 months.

CONCLUSIONS: Broad-spectrum drugs considered by the World Health Organisation to be critically important for human health, such as fluoroquinolones and amoxicillin-clavulanic acid, are amongst the most frequently prescribed antimicrobials in companion animal medicine, and these drugs are often prescribed without submitting a sample for culture and susceptibility testing.

CLINICAL RELEVANCE: Many cases of superficial pyoderma were treated for less than the recommended duration of 21 days, which may contribute to a higher rate of recurrent pyoderma and the development of drug resistance within the causal bacteria. Veterinarians should be aware that the use of fluoroquinolones, in particular, should be based upon the results of a culture and susceptibility test.  相似文献   
80.
The mean serum folate concentrations of Large White sows were compared between one group of 13 animals, 43–80 days pregnant and another group of 9 animals at weaning when the litters were 28–30 days old. The mean concentration was higher in sows at weaning (p<0.05) and the lowest levels were found in sows no more than 51 days pregnant (p<0.05).  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