全文获取类型
收费全文 | 1081篇 |
免费 | 104篇 |
专业分类
林业 | 67篇 |
农学 | 17篇 |
基础科学 | 3篇 |
107篇 | |
综合类 | 128篇 |
农作物 | 34篇 |
水产渔业 | 50篇 |
畜牧兽医 | 693篇 |
园艺 | 35篇 |
植物保护 | 51篇 |
出版年
2023年 | 13篇 |
2022年 | 17篇 |
2021年 | 26篇 |
2020年 | 34篇 |
2019年 | 52篇 |
2018年 | 45篇 |
2017年 | 41篇 |
2016年 | 43篇 |
2015年 | 29篇 |
2014年 | 45篇 |
2013年 | 58篇 |
2012年 | 78篇 |
2011年 | 99篇 |
2010年 | 48篇 |
2009年 | 35篇 |
2008年 | 77篇 |
2007年 | 62篇 |
2006年 | 56篇 |
2005年 | 38篇 |
2004年 | 49篇 |
2003年 | 49篇 |
2002年 | 46篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1926年 | 3篇 |
1916年 | 1篇 |
1914年 | 1篇 |
1909年 | 2篇 |
1900年 | 1篇 |
1883年 | 1篇 |
排序方式: 共有1185条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
Rankin AJ Krohne SG Glickman NW Glickman LT Stiles J 《American journal of veterinary research》2002,63(5):750-756
OBJECTIVES: To determine whether aqueous humor flare, measured by use of laser flaremetry, was proportional to aqueous humor protein concentration and to use laser flaremetry to evaluate disruption of the blood-aqueous barrier (BAB) in cats. ANIMALS: 30 healthy adult cats. PROCEDURE: Laser flaremetry values for all eyes were compared with aqueous humor protein concentrations determined by use of a Coomassie blue microprotein assay. Laser flaremetry was then performed on both eyes before (0 hours) and 4, 8, and 26 hours after initiation of topical application of 2% pilocarpine (q 8 h) to 1 eye of 9 cats or paracentesis of the anterior chamber of 1 eye of 8 cats. Intraocular pressure and pupil size were also determined. Aqueous humor protein concentration was extrapolated from flare values by use of linear regression. RESULTS: There was a linear relationship between flare values and aqueous humor protein concentrations. Topical application of 2% pilocarpine and paracentesis of the anterior chamber caused a breakdown of the BAB that was detected by use of laser flaremetry. The highest mean flare readings after application of pilocarpine or paracentesis were 24.4 and 132.8 pc/ms, respectively, which corresponded to aqueous humor protein concentrations of 85.5 and 434.9 mg/dl, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Paracentesis of the anterior chamber resulted in a more severe breakdown of the BAB in cats than topical application of 2% pilocarpine. Laser flaremetry may be a useful clinical method to detect increases in aqueous flare and, hence, disruptions of the BAB in cats. 相似文献
25.
The results of closing intraoperative cultures from 27 canine total hip replacements (THR) were reviewed. The relationship between these culture results and presurgical and surgical factors, and the short- and long-term success of THR were assessed. Eleven out of 27 cases had a positive culture, but none of these 11 cases were diagnosed with periprosthetic infection at follow-up examination. The duration of the clinical signs of hip disease prior to THR was significantly greater for those cases with a positive culture (P=0.034). The incidence of positive cultures was not related to surgical success. 相似文献
26.
ABSTRACT As a first step toward analysis of genetic variation and population structure in Peronospora tabacina, we used a collection of random genomic DNA fragments to survey for restriction fragment length polymorphisms (RFLPs) in DNA from a collection of isolates from Kentucky and other tobacco-growing regions of the United States. Also included in the study were isolates from the wild tobacco species, Nicotiana repanda, and from ornamental tobacco, N. alata. In a preliminary survey using DNA from 10 pathogen isolates, no polymorphisms were detected at six single-copy DNA loci using 22 probe-enzyme combinations. Moderately repetitive and highly repetitive regions of the genome were also remarkably similar between isolates, with only 6 of 15 different probes identifying genetic differences. Some of the polymorphic probes were then used to analyze a larger collection of isolates, most of which were from Kentucky. This resulted in the identification of very few additional polymorphisms, indicating that the population of P. tabacina that infects the Kentucky tobacco crop is genetically very homogeneous. The low level of polymorphism detected in this study overall, suggests that genetic variability may be lacking in P. tabacina populations throughout the United States. Two of the RFLP markers gave hybridization patterns that were consistent with P. tabacina being diploid. Frequencies of alleles at these loci and linkage disequilibrium between different marker loci indicated that genetic recombination does not occur frequently in the pathogen population. DNA polymorphisms that were identified in this study enabled us to differentiate the pathogen population into at least 10 haplotypes. One isolate was analyzed in detail and was shown to be genetically stable through several rounds of single-spore isolation and through several pathogenic cycles. 相似文献
27.
ABSTRACT Peronospora tabacina is an obligately parasitic oomycete that causes blue mold, a devastating disease of tobacco. Genetic studies of this pathogen have been hampered by the lack of molecular markers. We generated a set of molecular markers for P. tabacina by collecting sporangiospores from infected tobacco leaves, extracting spore DNA, and cloning it in a plasmid vector. The resulting clones were then used to probe DNA from a collection of P. tabacina isolates to survey for polymorphisms. Most probes gave unexpected hybridization patterns with signal intensities that varied significantly from one DNA sample to another or between different DNA preparations of the same isolate. These results indicated that certain DNA preparations contained DNA from a source other than P. tabacina, which in turn suggested that some probes might have been derived from contaminating organisms present in the spore suspensions. Therefore, we characterized the inserts of several recombinant plasmids to determine their origins. Sequence analysis revealed that several of the inserts encoded peptides with similarity to bacterial proteins, suggesting that they were derived from bacterial contaminants. Of the remaining clones, five exhibited similarity to retroelements, one resembled eukaryotic helicase genes, and nine had no similarity to sequences in the databases. These were postulated to be true P. tabacina DNA clones. Verification of the origin of each probe was achieved by filtering a spore suspension, extracting DNA from the retentate and filtrate, and probing Southern blots of these DNA samples. These experiments confirmed the probe origins predicted by sequence analysis, resulting in the generation of 20 different restriction fragment length polymorphism probes that are specific for P. tabacina DNA. These probes should enable identification of reliable genetic markers for population studies of the blue mold organism. 相似文献
28.
Grooters AM Leise BS Lopez MK Gee MK O'Reilly KL 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2002,16(2):142-146
Pythiosis (caused by the aquatic oomycete Pythium insidiosum) is a devastating and often fatal cause of either severe transmural gastroenteritis or locally invasive subcutaneous disease in dogs living in the southeastern United States. Although early diagnosis is essential for successful treatment, tools available for this task are limited. Therefore, we developed and evaluated an enzyme-linked immunosorbent assay (ELISA) for the detection of anti-P insidiosum antibodies in canine serum. A soluble mycelial extract of P insidiosum was utilized as antigen in the ELISA, which was used to evaluate serum from 43 dogs with pythiosis, 8 dogs with lagenidiosis (another canine oomycosis), 16 dogs with nonoomycotic fungal or algal infections, 22 dogs with nonfungal gastrointestinal or skin disease, and 55 healthy dogs. Results were expressed as percent positivity (PP) relative to a strong positive control serum run on each plate. Medians and ranges for each of the 5 groups were as follows: pythiosis (81.7%, 50.6-98.5%), lagenidiosis (17.3%, 11.3-29.2%), other fungal or algal infections (8.2%, 4.7-15.4%), nonfungal gastrointestinal or skin disease (6.2%, 3.9-20.7%), and healthy dogs (6.7%, 3.0-15.2%). When using a cutoff value of 40% PP, the sensitivity and specificity of the ELISA both were 100%. In addition, ELISA values measured after successful surgical therapy in 2 dogs showed a decrease of anti-P insidiosum antibody concentrations into the normal range as early as 2 months after treatment. We conclude that the ELISA is a sensitive and specific test for the diagnosis of canine pythiosis, and may be a useful tool for monitoring response to medical or surgical therapy. 相似文献
29.
Brian J McCluskey Brandy Burgess James Glover Hailu Kinde Sharon Hietala 《Journal of veterinary diagnostic investigation》2006,18(3):296-299
The use of sentinel chickens in establishing the negative status of commercial poultry flocks depopulated due to exotic Newcastle disease (END) is considered to be an economically beneficial process. However, the costs and benefits of using sentinel chickens in noncommercial operations are in question. The objective of this study was to use sentinel chickens to evaluate whether adequate cleaning and disinfection coupled with an appropriate time period without susceptible poultry species on the premises would eliminate END virus from a noncommercial poultry operation and preclude the need for placement of sentinels in previously infected operations before declaring them free of virus. Noncommercial poultry operations were selected from the 2002 to 2003 END outbreak database. Operations included in the study had one or more isolations of END virus (ENDV) from cloacal or oropharyngeal swabs of birds on the premises. A total of 546 birds were placed on 53 premises. All sentinel birds sampled after placements were negative by virus detection methods and serologic tests. Results of this study indicate that time and the application of appropriate cleaning and disinfection procedures will adequately mitigate the risk of viable virus persisting in noncommercial poultry operations. In the future, this information may eliminate the need for sentinel bird placement to ensure virus free status of premises before repopulation, thereby decreasing the costs of END eradication. 相似文献
30.
Danelle M Okeson Shirley Yeo Llizo Christine L Miller Amy L Glaser 《Journal of zoo and wildlife medicine》2007,38(2):240-244
West Nile virus has been associated with numerous bird mortalities in the United States since 1999. Five avian species at three zoological parks were selected to assess the antibody response to vaccination for West Nile virus: black-footed penguins (Spheniscus demersus), little blue penguins (Eudyptula minor), American flamingos (Phoenicopterus ruber), Chilean flamingos (Phoenicopterus chilensis), and Attwater's prairie chickens (Tympanuchus cupido attwateri). All birds were vaccinated intramuscularly at least twice with a commercially available inactivated whole virus vaccine (Innovator). Significant differences in antibody titer over time were detected for black-footed penguins and both flamingo species. 相似文献