全文获取类型
收费全文 | 2131篇 |
免费 | 70篇 |
国内免费 | 226篇 |
专业分类
林业 | 18篇 |
农学 | 51篇 |
基础科学 | 7篇 |
84篇 | |
综合类 | 777篇 |
农作物 | 27篇 |
水产渔业 | 31篇 |
畜牧兽医 | 1397篇 |
园艺 | 11篇 |
植物保护 | 24篇 |
出版年
2024年 | 7篇 |
2023年 | 21篇 |
2022年 | 53篇 |
2021年 | 94篇 |
2020年 | 73篇 |
2019年 | 87篇 |
2018年 | 47篇 |
2017年 | 102篇 |
2016年 | 90篇 |
2015年 | 90篇 |
2014年 | 111篇 |
2013年 | 90篇 |
2012年 | 179篇 |
2011年 | 162篇 |
2010年 | 134篇 |
2009年 | 146篇 |
2008年 | 126篇 |
2007年 | 135篇 |
2006年 | 108篇 |
2005年 | 86篇 |
2004年 | 93篇 |
2003年 | 75篇 |
2002年 | 56篇 |
2001年 | 35篇 |
2000年 | 48篇 |
1999年 | 35篇 |
1998年 | 30篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有2427条查询结果,搜索用时 109 毫秒
991.
992.
993.
This study was designed to investigate the antibiotic resistance, colicinogeny, serotyping and atypical biochemical characteristics of 41 Shiga toxin-producing Escherichia coli (STEC) strains detected using polymerase chain reaction from 90 E. coli strains isolated from 46 diarrhoeic calves. The STEC strains belonged to 14 different serogroups. Seventeen per cent of the STEC strains carried the eaeA gene while 14.28% of the 49 non-STEC strains were eaeA positive. Twenty eight (68.29%) of the 41 STEC strains were rhamnose non-fermentors. All the STEC strains revealed resistance to at least three of the antibiotics tested. 100% resistance was found against kanamycin and cephalexin followed by cephaloridine, enrofloxacin, amikacin, ampicillin, tetracycline, ceftiofur, ciprofloxacin, colistin and co-trimoxazole. Eighteen (44%) of the STEC strains produced colicin and all these colicinogenic strains were resistant to three or more antibiotics. Eleven STEC strains (26.82%) showed urease activity. The results of this study suggest that diarrhoeic calves are an important reservoir of STEC strains that are potentially pathogenic for farm animals and humans. Moreover, rhamnose fermentation, colicinogeny and atypical biochemical behaviour, such as urease activity, may serve as important markers or diagnostic tools for epidemiological surveys to trace the source of infection in disease outbreaks. 相似文献
994.
Jacob ME Parsons GL Shelor MK Fox JT Drouillard JS Thomson DU Renter DG Nagaraja TG 《Zoonoses and public health》2008,55(3):125-132
Escherichia coli O157 is an important foodborne pathogen and asymptomatic cattle serve as major reservoirs for human infection. We have shown a positive association between feeding distiller's grains and E. coli O157 prevalence in feedlot cattle. The objective of this study was to determine the effect of feeding dried distiller's grain (DDG) on faecal shedding of E. coli O157 in calves experimentally inoculated with E. coli O157. Holstein calves (five per treatment group), fed steam-flaked corn-based high-grain diets supplemented with 0% (control) or 25% DDG, were orally inoculated with a five-strain mixture (6 x 10(9) CFU/calf) of nalidixic acid-resistant (NalR) E. coli O157. Faecal samples were taken three times per week for 6 weeks to determine the prevalence and concentration of Nal E. coli O157. At the end of the study (day 43), calves were euthanized and necropsied. Ruminal, caecum, colon, and rectal contents, and rectoanal mucosal swab (RAMS) samples were collected at necropsy to determine NalR E. coli O157 concentration. There was a trend for an interaction between treatment and faecal sampling day. The concentration of NalR E. coli O157 in the faeces was significantly higher in faecal samples from calves fed DDG compared with control calves on days 35, 37, 39 and 42. At necropsy, the concentration of NalR E. coli O157 was higher in the caecum (P = 0.01), colon (P = 0.03) and rectum (P = 0.01) from calves fed DDG compared with control animals. The number of sites at necropsy positive for NalR E. coli O157 was higher in calves fed DDG compared with calves in the control treatment (P < 0.001). Our results indicate that E. coli O157 gut persistence and faecal prevalence increased in calves fed DDG, which potentially have important implications for food safety. 相似文献
995.
Bailiff NL Westropp JL Nelson RW Sykes JE Owens SD Kass PH 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2008,37(3):317-322
Background: It has been suggested that diseases that promote isosthenuria predispose to urinary tract infections because of a lack of the common bacteriostatic properties present in concentrated urine. Objectives: The purpose of this study was to assess the clinicopathologic risk factors for positive urine culture outcome in cats with chronic kidney disease (CKD), diabetes mellitus (DM), uncontrolled hyperthyroidism (HT), or lower urinary tract disease (LUTD). Methods: For this retrospective study, medical records of all cats in which a urinalysis and aerobic bacterial urine culture were performed between January 1995 and December 2002 were reviewed. Signalment, body weight, and clinicopathologic data were recorded. Based on the medical records, cats were diagnosed with CKD, DM, HT, or LUTD. Prevalence odds ratios and 95% confidence intervals were calculated using logistic regression. Multivariate models were created for each variable of interest while controlling for the confounding effect of disease group. Results: Six hundred fourteen cats met the criteria for inclusion in the study. Overall, positive urine cultures were identified in 16.9% of cats with CKD, 13.2% of cats with DM, 21.7% of cats with HT, and 4.9% of cats with clinical signs of LUTD. Decreasing urine specific gravity was not associated with positive urine culture when controlled for disease but pyuria, bacteriuria, and hematuria were all associated with positive urine culture outcome. Persians, females, increasing age, and decreasing body weight were all associated with positive urine culture outcome. Conclusions: Performing a urine culture sample based solely on the presence of isosthenuria does not seem warranted. Further studies are warranted to help identify host predisposing factors for urinary bacterial colonization in cats with these diseases. 相似文献
996.
997.
Escherichia coli O157:H7 – Discerning Facts from Fiction: An Integrated Research and Extension Project for Multiple Audiences
下载免费PDF全文
![点击此处可从《Zoonoses and public health》网站下载免费的PDF全文](/ch/ext_images/free.gif)
D. A. Moore D. R. Smith W. M. Sischo K. Heaton T. E. Besser 《Zoonoses and public health》2016,63(1):72-81
The O157:H7 (EcO157) epidemiology of Shiga‐toxin‐producing Escherichia coli (STEC) in cattle is complex, and myths about pre‐harvest control are perpetuated. The objectives of this project were to identify perpetuated misinformation and inform four audiences about evidence‐based risks and pre‐harvest control of EcO157 by addressing: (i) EcO157 epidemiology and pre‐harvest control; (ii) how food safety policy is created; and (iii) how to present accurate information about EcO157. An environmental scan using a daily Internet search helped identify themes for education. A literature review of pre‐harvest control measures contributed to the development of educational materials (fact sheets, website, web presentations and conferences). Conference 1 was a webinar with 315 registrants, 10 countries including 41 US states and four Canadian provinces. Most participants felt confident in using their new knowledge, more than half felt confident enough to answer EcO157 questions from the public and many would recommend the recorded version of the webinar to colleagues. Conference 2 was live in the Washington, DC, area with most participants employed by the US government. All agreed that they better understood pre‐harvest control, how food safety policy was made, and were confident they could create an effective message about STEC pre‐harvest control. Videos were posted and received 348 Internet visitors within 2 months. Conference 3 was a webinar with a live audience and Twitter feeds, targeting people who give nutrition advice. Almost all ranked the programme good to excellent and relevant to their work. About 25% indicated that they would share: ‘grass‐fed beef is not safer than grain‐fed’, 25% would share information on effectiveness of cattle vaccines, and 14% would share information on message mapping. Across all conferences, major changes in knowledge included the following: there is no additional risk of EcO157 shedding from grain‐fed versus grass‐fed cattle, pre‐harvest vaccination is efficacious, and production systems (pasture versus confinement) do not affect EcO157 shedding rates. 相似文献
998.
DENG Bo-xiong LIU Qing DENG An-yuan LI Wen-wen SONG Zhi-gang YU Qiong CHEN Guang-fen LIU Shu-huang LIU Ya-gang 《中国畜牧兽医》2016,43(1):235-241
To analyze the pathogenicity and biological characteristics of duck E.coli, 27 strains of duck pathogenic E.coli were isolated from dead ducks with the typical characterize of colibacillosis by isolation and culture, physical and chemical properties identification in Xichang city.O serotype identification, drug sensitivity test and virulence associated genes were detected in 27 strains of duck pathogenic E.coli.The result showed that the predominant serotypes were O119, O86, O126, O142 and O44, which accounted for 55.56%.O119 was the epidemic and pathogenic serotype in this farm, which accounted for 40.74% in 27 strains of duck pathogenic E.coli.Through the drug sensitivity test of 20 kinds of clinical commonly used drugs, we found that all strains were sensitive to amikacin, gentamicin and polymyxin B.Besides, 10 drugs(ceftriaxone, etc) were lightly sensitive.However, these strains were resistant to 5 kinds of drugs(rifampicin, etc).The detection result of PCR about virulence associated genes indicated that the positive of iutA, hlyF, Iss, IroN, ompT, fyuA, irp 2, Tsh and papA genes were 100.00%, fimC and K 99 genes were 59.26% and 7.40%, respectively.The results provided an important reference for effective prevention and control of duck colibacillosis, and laid the foundation for further study of E.coli. 相似文献
999.
GAI Dong-xue REN Hong-lin LU Shi-ying HU Pan MENG Xian-mei LIU Xi SONG De-gang JIN Wen ZHANG Song CHANG Jiang LIU Yan-yan LIU Zeng-shan 《中国畜牧兽医》2016,43(2):493-498
In order to detect viable E.coli in milk,a new PMA-qPCR method was established.The influences of different PMA concentration,dark incubation time,exposure time on dead bacteria inhibition effect were determined by detection of the cell numbers of viable and heat-killed E.coli suspensions at concentration of 1×108 CFU/mL through fluorescence quantitative PCR (qPCR) method.The results showed that qPCR assay could specifically detect E.coli,and the viable E.coli must be exposed to 90 ℃ for 30 s in water bath to be lethal.The best treatment was 10 μg/mL PMA with 15 min of dark incubation time and 10 min of exposure time.This treatment could inhibit dead cell signals to a largest extend,while had little impact on aviable cells.The stability of PMA-qPCR assay was kept while the concentration of bacteria was more than 1×108 CFU/mL.The regression equation of standard curve was y=-3.356x+47.413,R2=0.9989,the lowest detection limit was 103 CFU/mL.The result of adding assay was agreed with the actual situation.This study laid a foundation for using of PMA-qPCR to detect the viable E.coli in food. 相似文献
1000.
Erjie Tian Chunli Chen Wanjun Hu Yusong Miao Ishfaq Muhammad Qiaomei Zhang Yuhao Liu Liang Xu Jiaxin Bao Liangjun Ding Jichang Li 《Journal of veterinary pharmacology and therapeutics》2019,42(5):556-563
Avian pathogenic Escherichia coli could cause localized and systemic infection in the poultry, and danofloxacin is usually used to treat avian colibacillosis through oral administration. To promote prudent use of danofloxacin and reduce the emergence of drug‐resistant E. coli strains, it is necessary to understand the population pharmacokinetics (PopPK) of danofloxacin in chicken intestines. In this study, reversed‐phase high performance liquid chromatography (HPLC) with fluorescence detection was used to detect the concentrations of danofloxacin in the contents of duodenum, jejunum, and ileum of the healthy and infected chickens after single oral administration (5 mg/kg body weight). Then, the PopPK of danofloxacin in intestines were analyzed using NONMEM software. As a result, a two‐compartment PK model best described the time‐concentration profile of duodenal, jejunal, and ileal contents. Interestingly, absorption rate (Ka), distribution volume (V), and clearance (CL) for danofloxacin from duodenal, jejunal to ileal contents were sequentially decreased in the healthy chickens. However, the trend of Ka, V, and CL of danofloxacin was changed dramatically in the intestine of infected chickens. Ka and V of danofloxacin in the jejunum were higher than in the ileum and duodenum. Compared with healthy chickens, Ka and V of danofloxacin in the duodenum decreased significantly, while increased in jejunum, respectively. It has been noted that Ka decreased and V increased in the ileum of infected chickens. Besides, CL in the duodenum, jejunum, and ileum of infected chickens was, respectively, lower than those of healthy chickens. Interestingly, the relative bioavailability (F) of danofloxacin in the ileum was relatively higher in both healthy and infected chickens. In addition, F in the duodenal, jejunal, and ileal contents of infected chickens was respectively higher than healthy chickens. In summary, the PopPK for danofloxacin in infected chicken intestines was quite different from healthy chickens. The absorption, distribution, and clearance of danofloxacin in healthy chickens decreased from duodenum to jejunum and to ileum. Moreover, the pharmacokinetic characteristics in the intestine of infected chickens changed significantly, and the pharmacokinetic characteristics in the ileum can be used as a representative of all intestinal segments. 相似文献