全文获取类型
收费全文 | 166295篇 |
免费 | 9323篇 |
国内免费 | 101篇 |
专业分类
林业 | 6701篇 |
农学 | 5649篇 |
基础科学 | 1035篇 |
21277篇 | |
综合类 | 24774篇 |
农作物 | 6095篇 |
水产渔业 | 8747篇 |
畜牧兽医 | 88348篇 |
园艺 | 2205篇 |
植物保护 | 10888篇 |
出版年
2020年 | 1357篇 |
2019年 | 1641篇 |
2018年 | 2642篇 |
2017年 | 2893篇 |
2016年 | 2709篇 |
2015年 | 2322篇 |
2014年 | 2861篇 |
2013年 | 6782篇 |
2012年 | 5066篇 |
2011年 | 6089篇 |
2010年 | 4164篇 |
2009年 | 4164篇 |
2008年 | 6042篇 |
2007年 | 5853篇 |
2006年 | 5444篇 |
2005年 | 5017篇 |
2004年 | 4886篇 |
2003年 | 4951篇 |
2002年 | 4507篇 |
2001年 | 5803篇 |
2000年 | 5716篇 |
1999年 | 4564篇 |
1998年 | 1827篇 |
1997年 | 1773篇 |
1996年 | 1643篇 |
1995年 | 1981篇 |
1994年 | 1659篇 |
1993年 | 1667篇 |
1992年 | 3465篇 |
1991年 | 3616篇 |
1990年 | 3603篇 |
1989年 | 3576篇 |
1988年 | 3267篇 |
1987年 | 3294篇 |
1986年 | 3228篇 |
1985年 | 3045篇 |
1984年 | 2501篇 |
1983年 | 2188篇 |
1982年 | 1461篇 |
1979年 | 2089篇 |
1978年 | 1665篇 |
1977年 | 1462篇 |
1976年 | 1403篇 |
1975年 | 1497篇 |
1974年 | 1755篇 |
1973年 | 1819篇 |
1972年 | 1792篇 |
1971年 | 1550篇 |
1970年 | 1581篇 |
1969年 | 1505篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
ABSTRACT Phylogenetic analysis revealed that isolates of Alternaria alternata causing black rot of citrus were associated with six well-supported evolutionary lineages. Isolates recovered from brown spot lesions on Minneola tangelo, leaf spot lesions on rough lemon, and healthy citrus tissue and noncitrus hosts were related closely to isolates from black-rotted fruit. Phylogenies estimated independently from DNA sequence data from an endopolygalacturonase gene (endoPG) and two anonymous regions of the genome (OPA1-3 and OPA2-1) had similar topologies, and phylogenetic analysis was performed on the combined data set. In the combined phylogeny, isolates from diverse ecological niches on citrus and noncitrus hosts were distributed in eight clades. Isolates from all lineages, regardless of ecological or host association, caused black rot in fruit inoculation assays, demonstrating that small-spored Alternaria isolates associated with different ecological niches on citrus and other plant hosts are potential black rot pathogens. These data also indicated that the fungi associated with black-rotted fruit do not form a natural evolutionary group distinct from other Alternaria pathogens and saprophytes associated with citrus. The use of the name A. citri to describe fungi associated with citrus black rot is not justified and it is proposed that citrus black rot fungi be referred to as A. alternata. 相似文献
992.
H. Hu A. Barker T. Harcourt‐Brown N. Jeffery 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2015,29(6):1456-1463
Intracranial neoplasia is commonly diagnosed in dogs and can be treated by a variety of methods, but formal comparisons of treatment efficacy are currently unavailable. This review was undertaken to summarize the current state of knowledge regarding outcome after the treatment of intracranial masses in dogs, with the aim of defining optimal recommendations for owners. This review summarizes data from 794 cases in 22 previously published reports and follows PRISMA guidelines for systematic review. A Pubmed search was used to identify suitable articles. These then were analyzed for quality and interstudy variability of inclusion and exclusion criteria and the outcome data extracted for summary in graphs and tables. There was a high degree of heterogeneity among studies with respect to inclusion and exclusion criteria, definition of survival periods, and cases lost to follow‐up making comparisons among modalities troublesome. There is a need for standardized design and reporting of outcomes of treatment for brain tumors in dogs. The available data do not support lomustine as an effective treatment, but also do not show a clear difference in outcome between radiotherapy and surgery for those cases in which the choice is available. 相似文献
993.
Rapid detection of canine parvovirus in feces using monoclonal antibodies and enzyme-linked immunosorbent assay 总被引:2,自引:0,他引:2
M M Mildbrand Y A Teramoto J K Collins A Mathys S Winston 《American journal of veterinary research》1984,45(11):2281-2284
Monoclonal antibodies were used to develop a double antibody enzyme-linked immunosorbent assay for the detection of canine parvovirus (CPV) antigen in fecal samples. The assay was specific for the hemagglutinating protein of CPV and detected as little as 1.5 ng of virus within a 15-minute incubation period. The use of monoclonal antibodies against 2 epitopes on the CPV antigen permitted the simultaneous addition of test sample and enzyme-conjugated antibody, thus considerably simplifying the manipulations required for the assay. Results were visually determined without special instrumentation. Clinical studies revealed greater than 95% correlation between enzyme-linked immunosorbent assay results and hemagglutination titers. 相似文献
994.
Nested reverse transcriptase-polymerase chain reaction (RT-PCR) for typing ruminant pestiviruses: bovine viral diarrhea viruses and border disease virus. 下载免费PDF全文
995.
REBECCA L. FRANKENY VMD DAVID A. WILSON DVM MS Diplomate ACVS NAT T. MESSER IV DVM Diplomate ABVP CYNTHIA CAMPBELL-BEGGS DVM 《Veterinary surgery : VS》1995,24(6):515-517
Jejunojejunal intussusception occurred after jejunal resection and stapled functional end-to-end anastomosis in two pony mares. In both mares, the lead point of the intussusception was the stapled functional end-to-end (FEE) anastomosis. The stapled free ends of jejunum were oversewn with an inverting suture pattern. A possible explanation for development of the intussusception was the acute angle created in the intestine by the FEE anastomsis. This angulation may have impaired flow of ingesta causing motility changes that predisposed the site to intussusception. Because the oversewn blind intestinal ends acted as the lead point for formation of the intussusception, it may be inadvisable to oversew the stapled anastomotic ends. 相似文献
996.
M.J.B.M. Weljtens P.G.H. Bijker J. Van der Plas H.A.P. Urlings M.H. Biesheuvel 《The Veterinary quarterly》2013,33(4):138-143
Summary Numerous epidemiological reports implicate foods of animal origin as vehicles of human campylobacteriosis. Pigs are probably an important reservoir of campylobacter and a potential source of human infection. In order to improve our knowledge of the epidemiology of campylobacter in pigs, the prevalence of campylobacter and its contamination of feed were monitored in eight pig farms. Faeces samples of pigs aged 11 and 22 weeks, and samples of rectal, ileal and gastric content at a slaughterhouse were collected for bacteriological examination. On 5 farms, subsequent groups of pigs housed in the same stalls was sampled, too. A selection of the campylobacter isolates was characterized with a genetic typing method (RFLP). More than 85% of the sampled porkers were shown to be intestinal carriers of campylobacter at all stages of fattening. Subsequent groups of pigs housed in the same stalls were all carriers, too. The level of campylobacters in the faeces tended to decrease as the pigs got older. There was no difference in the frequency and level of infection with campylobacter between porkers on different farms. The feeding system (wet feed versus dry pellets) did not seem to influence the prevalence of campylobacter although wet feed gave lower counts of Enterobacteriaceae in the faeces. RFLP‐typing showed a high diversity of campylobacter strains at each sampling on the farm. Similarities were seen between strains isolated during two subsequent samplings of the same group of pigs, but not between strains isolated on the same farm from subsequent groups of pigs housed in the same stall. This suggests that the piglets were already infected at a young age on the breeding farm. 相似文献
997.
Effect of Cranberry Extract on the Frequency of Bacteriuria in Dogs with Acute Thoracolumbar Disk Herniation: A Randomized Controlled Clinical Trial 下载免费PDF全文
998.
Pharmacokinetic profiles of the two major active metabolites of metamizole (dipyrone) in cats following three different routes of administration 下载免费PDF全文
B. Lebkowska‐Wieruszewska T. W. Kim B. Chea H. Owen A. Poapolathep M. Giorgi 《Journal of veterinary pharmacology and therapeutics》2018,41(2):334-339
This study was performed to determine pharmacokinetic profiles of the two active metabolites of the analgesic drug metamizole (dipyrone , MET), 4‐methylaminoantipyrine (MAA), and 4‐aminoantipyrine (AA), after intravenous (i.v., intramuscular (i.m.), and oral (p.o.) administration in cats. Six healthy mixed‐breed cats were administered MET (25 mg/kg) by i.v., i.m., or p.o. routes in a crossover design. Adverse clinical signs, namely salivation and vomiting, were detected in all groups (i.v. 67%, i.m. 34%, and p.o. 15%). The mean maximal plasma concentration of MAA for i.v., i.m., and p.o. administrations was 148.63 ± 106.64, 18.74 ± 4.97, and 20.59 ± 15.29 μg/ml, respectively, with about 7 hr of half‐life in all routes. Among the administration routes, the area under the plasma concentration curve (AUC) value was the lowest after i.m. administration and the AUCEV/i.v. ratio was higher in p.o. than the i.m. administration without statistical significance. The plasma concentration of AA was detectable up to 24 hr, and the mean plasma concentrations were smaller than MAA. The present results suggest that MET is converted into the active metabolites in cats as in humans. Further pharmacodynamics and safety studies should be performed before any clinical use. 相似文献
999.
Adult Rana pipiens pipiens (Shreber) are highly sensitive to insecticidal α-cyano-3-phenoxybenzyl esters administered subcutaneously, i.e., LD50 0.13–0.35 mg/kg for deltamethrin and the most potent isomer of each of cis-cypermethrin, fenpropathrin, and fenvalerate and 0.65 mg/kg for (1R,αS)-trans-cypermethrin. Pyrethroids lacking the α-cyano substituent [pyrethrins, S-bioallethrin, kadethrin, and the Cis- and trans-isomers of (1R)-tetramethrin, (1RS)-resmethrin, (1R)-phenothrin, and (1R)-permethrin] vary greatly in their toxicity (LD50 0.14 to > 60 mg/kg) and the trans isomers are much less toxic than the corresponding cis isomers. The trans/cis specificity is due in large part to relative detoxification rates based on synergism studies with the resmethrin and permèthrin isomers and liver pyrethroid esterase assays with the permethrin and cypermethrin isomers. Poisoning by the noncyano compounds involves hyperactivity and tremors whereas by the cyanophenoxybenzyl esters involves tonic seizures and choreoathetosis, i.e., types I and II syndromes, respectively. Picrotoxinin, t-butylbicyclophosphate, and five other small cage compounds give a third type of syndrome with clonic seizures. Diazepam and its 2′-fluoro-4-methyl-4,5-dihydro analog (RO 5-3636) are more effective than 23 other compounds tested in protecting against deltamethrin toxicity. Diazepam is most effective in alleviating the Type II syndrome, intermediate with the type I syndrome, and is not active with picrotoxinin. 相似文献
1000.
Evaluation of an in-office allergy screening test in nonatopic dogs having various intestinal parasites 下载免费PDF全文
Paradis M Lécuyer M 《The Canadian veterinary journal. La revue veterinaire canadienne》1993,34(5):293-295
An in-office allergy screening kit was evaluated in 10 dogs that had no clinical signs of atopy but had various intestinal parasites. All 10 dogs had a positive reaction to the dust mite Dermatophagoïdes farinae, and four dogs had positive reactions to at least one other group of allergens. The kit as presently marketed gives numerous false positive results in parasitized nonatopic dogs. 相似文献