全文获取类型
收费全文 | 1519篇 |
免费 | 127篇 |
专业分类
林业 | 82篇 |
农学 | 67篇 |
基础科学 | 8篇 |
251篇 | |
综合类 | 125篇 |
农作物 | 88篇 |
水产渔业 | 156篇 |
畜牧兽医 | 702篇 |
园艺 | 28篇 |
植物保护 | 139篇 |
出版年
2023年 | 13篇 |
2022年 | 34篇 |
2021年 | 58篇 |
2020年 | 77篇 |
2019年 | 80篇 |
2018年 | 86篇 |
2017年 | 72篇 |
2016年 | 71篇 |
2015年 | 47篇 |
2014年 | 78篇 |
2013年 | 69篇 |
2012年 | 112篇 |
2011年 | 110篇 |
2010年 | 45篇 |
2009年 | 50篇 |
2008年 | 61篇 |
2007年 | 59篇 |
2006年 | 48篇 |
2005年 | 46篇 |
2004年 | 58篇 |
2003年 | 46篇 |
2002年 | 26篇 |
2001年 | 28篇 |
2000年 | 14篇 |
1999年 | 21篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 17篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1981年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1974年 | 6篇 |
1973年 | 8篇 |
1971年 | 8篇 |
1970年 | 5篇 |
1969年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有1646条查询结果,搜索用时 15 毫秒
61.
A dentigerous cyst was diagnosed in the right rostral maxilla of a 6-month-old Siamese cat affecting the maxillary right canine tooth. The deciduous maxillary right canine tooth was extracted and the dentigerous cyst wall was curetted. The permanent tooth was not removed, however it was mobile following the surgical procedure. Examination 6-months following surgery indicated appropriate development of the tooth with no mobility or periodontal pocket formation. The maxillary right canine tooth had an abnormal shape but was functional with an acceptable appearance. 相似文献
62.
Hanel RM Crawford PC Hernandez J Benson NA Levy JK 《American journal of veterinary research》2003,64(5):538-543
OBJECTIVE: To determine whether passive transfer of IgG in neonatal kittens affects plasma opsonic capacity and neutrophil phagocytic and oxidative burst responses to bacteria in vitro. ANIMALS: 22 kittens from 6 specific pathogen-free queens. PROCEDURE: Kittens were randomized at birth into the following treatment groups: colostrum-fed, colostrum-deprived, or colostrum-deprived supplemented with feline or equine IgG. Blood samples were collected at intervals from birth to 56 days of age. Plasma IgG concentrations were determined by radial immunodiffusion assay. Neutrophil function was assessed by a flow cytometry assay providing simultaneous measurement of bacteria-induced phagocytosis and oxidative burst. The opsonic capacity of kitten plasma was determined in an opsonophagocytosis assay with bacteria incubated in untreated or heat-inactivated plasma. RESULTS: Among treatment groups, there were no significant differences in neutrophil phagocytic and oxidative burst responses to bacteria or opsonic capacity of plasma. In all samples of plasma, inactivation of complement and other heat-labile opsonins significantly reduced the opsonic capacity. Plasma IgG concentrations in kittens did not correlate with neutrophil function or plasma opsonic capacity before or after inactivation of complement. CONCLUSIONS AND CLINICAL RELEVANCE: The plasma opsonic capacity and neutrophil phagocytic and oxidative burst responses in vitro of kittens receiving passive transfer of IgG via colostrum intake or IgG supplementation and those deprived of colostrum were similar. The alternate complement pathway or other heat-labile opsonins may be more important than IgG in bacterial opsonization and phagocytosis. 相似文献
63.
Paranhos-Silva M Oliveira GG Reis EA de Menezes RM Fernandes O Sherlock I Gomes RB Pontes-de-Carvalho LC dos-Santos WL 《Veterinary parasitology》2003,114(2):97-111
In this study, we compare the development of infection and/or disease in Beagle dogs intradermally infected with Leishmania chagasi, in the presence or absence of Lutzomyia longipalpis saliva, with those of intravenously infected animals.Spleen samples of all the animals inoculated with parasites had positive polymerase chain reaction tests for Leishmania DNA. Positive spleen cultures for Leishmania were detected earlier (P < or = 0.018) and were more frequent (five out of the five animals) in intravenously infected animals than in the intradermally infected animals, in presence (two out of the six animals) or absence (three out of the five animals) of salivary gland lysate of L. longipalpis. Significant increase in serum antibodies against Leishmania was observed only in the intravenously infected group (P = 0.004). In addition, dogs with infection confirmed by isolation of amastigotes or detection of parasite DNA were, nevertheless, negative for anti-Leishmania antibodies up to 5 months or more after infection. Only animals of the intravenously infected group developed progressive decreases in hematocrit (Pearson r = -0.8076, P = -0.0026) and hemoglobin (Pearson r = -0.8403, P = 0.0012) during the infection period. No significant difference in the course of infection was observed between groups of intradermally infected animals. The data presented herein confirms that the intradermal inoculation of dogs with Leishmania produces an asymptomatic form of infection. It also fails to show an advantage in using L. longipalpis saliva as an infection-enhancing agent in experimental canine leishmaniasis. 相似文献
64.
Three cases of equine subcutaneous pythiosis with dissemination to the internal organs were investigated. The subcutaneous lesions were observed on the mammary gland, nostrils and limbs of the infected horses. Histopathological analysis of the infected tissues revealed a strong eosinophilic reaction, with macrophages, mast cells and giant cells. Sparsely septated hyphal filaments of 4-6 microm diameter were identified in the center of the eosinophilic areas. Specific fluorescent antibody against Pythium insidiosum confirmed the hyphae in the infected tissues in three examined horses. In one of the three cases, the DNA sequences amplified from the infected subcutaneous tissues and internal organs, revealed that P. insidiosum's 18S SSU rDNA amplicons shared 100% identity with those sequences deposit in GenBank. This is the first report confirming by immunochemical and genetic techniques that P. insidiosum can disseminated from superficial to deep structures. 相似文献
65.
Lee IT Levy JK Gorman SP Crawford PC Slater MR 《Journal of the American Veterinary Medical Association》2002,220(5):620-622
OBJECTIVE: To determine prevalence of FeLV infection and serum antibodies against feline immunodeficiency virus (FIV) in unowned free-roaming cats. DESIGN: Cross-sectional serologic survey. ANIMALS: 733 unowned free-roaming cats in Raleigh, NC, and 1,143 unowned free-roaming cats in Gainesville, Fla. RESULTS: In Raleigh, overall prevalence of FeLV infection was 5.3%, and overall seroprevalence for FIV was 2.3%. In Gainesville, overall prevalence of FeLV infection was 3.7%, and overall seroprevalence for FIV was 4.3%. Overall, FeLV prevalence was 4.3%, and seroprevalence for FIV was 3.5%. Prevalence of FeLV infection was not significantly different between males (4.9%) and females (3.8%), although seroprevalence for FIV was significantly higher in male cats (6.3%) than in female cats (1.5%). CONCLUSIONS AND CLINICAL RELEVANCE: Prevalence of FeLV infection and seroprevalence for FIV in unowned free-roaming cats in Raleigh and Gainesville are similar to prevalence rates reported for owned cats in the United States. Male cats are at increased risk for exposure to FIV, compared with female cats. 相似文献
66.
Carvalho R Passos LM Martins AS 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2000,47(5):351-359
In this study, a multiplex polymerase chain reaction (PCR) procedure was developed for differentiation of strains and field isolates of equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4). Specific oli-gonucleotide primers were combined to amplify the thymidine kinase (TK) gene region of EHV-1 and EHV-4, which would yield fragments of different lengths for each virus in the same amplification reaction. The specificity of the largest PCR amplicon for EHV-4 was confirmed by restriction digestion with HindIII. The multiplex PCR proved to be a fast and sensitive method for typing EHV-1 and EHV-4 isolates and for detection and differentiation of both viruses in field samples in which infectious virus is no longer available. The sensitivity was improved by combining cycling optimization and visualization of PCR products in ethidium bromide and silver-stained acrylamide gels. 相似文献
67.
Christine V Fiorello Mark W Cunningham Shauna L Cantwell Julie K Levy Erin M Neer Kenneth Conley Paul M Rist 《Journal of zoo and wildlife medicine》2007,38(2):317-322
A free-ranging, adult male Florida panther (Puma concolor coryi) was immobilized and evaluated for hematuria following routine capture. Prior to anesthetic recovery, the panther was fitted with a telemetry collar. After an initially quiet recovery, the panther began thrashing in the transport cage, and was again immobilized. Pink foam was evident from the nostrils, and crackles were ausculted over the chest, indicating pulmonary edema. Postobstructive pulmonary edema was diagnosed based on history, clinical signs, radiographic evaluation, and blood gas analysis. The animal was treated intensively for several hours with diuretics, oxygen, and manual ventilation. The panther responded rapidly to therapy and was released back into the wild 48 hr after presentation. Postobstructive pulmonary edema, also called negative-pressure pulmonary edema, may be underrecognized in veterinary medicine. In this case, the telemetry collar, in conjunction with anesthetic recovery in a small transport crate, may have contributed to tracheal obstruction. Wildlife veterinarians and biologists should be aware of the risk of airway obstruction when placing tracking collars, and animals should be continuously monitored during anesthetic recovery to ensure the presence of a patent airway. 相似文献
68.
69.
ABSTRACT Monoconidial isolates of the fungus causing gray leaf spot of maize were obtained from diseased leaves collected throughout the United States and analyzed for genetic variability at 111 amplified fragment length polymorphism (AFLP) loci. Cluster analysis revealed two very distinct groups of Cercospora zeae-maydis isolates. Both groups were found to be relatively uniform internally with an average genetic similarity among isolates of approximately 93 and 94%, respectively. The groups were separated from each other by a genetic distance of approximately 80%, a distance greater than that separating each group from the sorghum pathogen, C. sorghi (67 to 70%). Characteristics and dimensions of conidia and conid-iophores produced on infected plants or nutrient media were unreliable criteria for taxonomic differentiation of isolates composing the two groups of C. zeae-maydis. Nucleotide sequences of 5.8S ribosomal DNA (rDNA) and the internal transcribed spacer (ITS) regions were identical within each group but different between the two groups and different from C. sorghi. Restriction fragment length polymorphisms generated by digestion of the 5.8S rDNA and ITS regions with TaqI readily distinguished each group and C. sorghi. Isolates in one group were generally distributed throughout maize-producing regions of the United States; isolates in the other group were localized in the eastern third of the country. Both types were present in the same fields at some locations. The genetic distance based on AFLP profiles and different ITS nucleotide sequences between the two morphologically indistinguishable groups indicate that they are sibling species. Although it is unlikely that breeding for resistance to gray leaf spot will be confounded by local or regional variation in the pathogen, a vigilant approach is warranted, because two pathogenic species exist with unknown abilities to evolve new pathotypes. 相似文献
70.
Mediterranean fruit fly, Ceratitis capitata (Wied.), is a major pest of fruits and vegetables throughout the region, reduces yield of marketable fruit and limits exports. The Arava Medfly Eradication Project (AMEP) was initiated in 1997, and serves as a pilot effort to begin implementing the sterile insect technique in the Near East. It could become a model for future implementation of the proposed EASTMED project, a plan conceived and planned by the International Atomic Energy Agency in 1994–1995 with input of regional experts. The target area lies in the Arava Valley between the Dead Sea and the Red Sea. AMEP activities include host mapping, population monitoring and suppression followed by weekly releases of sterile flies. This project will lead to permanent establishment and maintenance of Medfly free areas. In addition, new technologies are being tested under local conditions. This includes use of tsl male-only strains of medflies, aerial releases with a chilled insect release machine, female attractants and new trap designs. At present, the project relies upon long-distance shipping of pupae from Madeira, Portugal and Guatemala rather than local sources. The medfly population on the Israeli side of the Arava valley, was monitored in 132 trimedlure loaded traps. It dropped by July 1999 to 0.04 flies per trap per day from the pre-eradication level of 0.71 flies per trap per day in July 1998. In June 1999, only 19% of the traps captured wild flies as compared to 40% of the traps in June 1997. As medfly does not respect international boundaries, transboundary co-operation is a key factor for successful implementation. Current project status and plans for future expansion within Israel, Jordan and the Palestinian Authority will be presented. 相似文献