全文获取类型
收费全文 | 1098篇 |
免费 | 56篇 |
国内免费 | 2篇 |
专业分类
林业 | 92篇 |
农学 | 72篇 |
基础科学 | 22篇 |
300篇 | |
综合类 | 57篇 |
农作物 | 132篇 |
水产渔业 | 98篇 |
畜牧兽医 | 280篇 |
园艺 | 20篇 |
植物保护 | 83篇 |
出版年
2023年 | 18篇 |
2022年 | 31篇 |
2021年 | 40篇 |
2020年 | 56篇 |
2019年 | 66篇 |
2018年 | 73篇 |
2017年 | 78篇 |
2016年 | 67篇 |
2015年 | 26篇 |
2014年 | 46篇 |
2013年 | 111篇 |
2012年 | 67篇 |
2011年 | 72篇 |
2010年 | 52篇 |
2009年 | 42篇 |
2008年 | 46篇 |
2007年 | 28篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 20篇 |
2003年 | 14篇 |
2002年 | 19篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1959年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有1156条查询结果,搜索用时 578 毫秒
81.
The B1 strain of Newcastle disease virus (NDV-B1), which is nonpathogenic for newly hatched chickens, killed embryos when it was used to inoculate chicken eggs at embryonation day 18. Treatment of NDV-B1 with an alkylating agent, ethylmethane sulfonate (EMS) markedly reduced the pathogenicity of the virus for 18-day-old chicken embryos. Eggs inoculated with the modified virus (NDV-B1-EMS) hatched, and the virus was isolated from lungs and spleen of 1-day-old chickens. The hatched chickens developed antibody to NDV and were protected against challenge exposure (at 4 weeks of age) with a highly virulent GB-Texas strain of NDV. Presence of maternal antibody to NDV in embryonating eggs did not influence the protective ability of NDV-B1-EMS, which also induced protective immunity when administered to 4-week-old chickens. The 50% protective dose of NDV-B1-EMS in maternal antibody-negative and -positive embryos was calculated to be 10.77 and 17.70 embryo 50% lethal doses, respectively. Results of the study indicated that NDV-B1-EMS may be used as an embryo vaccine to protect chickens against Newcastle disease. 相似文献
82.
83.
84.
Summary A pilot health monitoring system was started in 1990 to develop statistically valid data for use in estimating the disease frequencies in dairy cattle and buffaloes. This paper presents the design of the monitoring programme and frequencies of selected diseases. Eighty herds were selected with typical livestock management practices of the farmers in the area. Veterinary assistants visited the farms once a month for 12 months to collect livestock inventory, production, disease and preventive treatment data. The incidence density method was used as a measure of disease frequency.In adults, breeding problems, mastitis and gastro-intestinal problems were the highest reported conditions. Respiratory problems were the commonest in young stock. The calves of both species frequently had gastro-intestinal and respiratory disease conditions. Most of the calf crop of both species were lost within the first 3 months of life.
Monitoreo De Problemas De Salud Bovina En Hatos Lecheros Pequenos En El Territorio Capital De Islamabad
Resumen Se inició un sistema de monitoreo piloto en 1990, con el propósito de desarrollar datos estadísticos válidos para estimar la frecuencia de enfermedades en ganado lechero y en búfalos. Este artículo presenta el diseño del programa de monitoreo y la frecuencia de las enfermedades seleccionadas. Se seleccionaron ochenta hatos con el manejo típico de los ganaderos del área. Los veterinarios visitaron las fincas una vez al mes durante 12 meses para colectar información. El método de densidad en la incidencia fue usado para medir la frecuencia de enfermedades.En adultos, las condiciones más frecuentemente encontradas fueron problemas de fertilidad, mastitis y problemas gastrointestinales. Las afecciones respiratorias fueron el común denominador en jóvenes. Los terneros de ambas especies se encontraron frecuentemente con problemas gastrointestinales y respiratorios, conjuntamente, siendo la mortalidad extremadamente alta en los 3 primeros meses de vida para ambas especies.
Gestion Des Problemes De Sante Bovine De Petits Troupeaux Laitiers Sur Le Territoire De Islamabad: Schema, Donnees Et Frequences De La Maladie
Résumé Un système pilote de gestion de la santé a débuté en 1990 pour développer des données statistiquement valables pour être utilisées dans l'estimation de la fréquence des maladies de bovins laitiers et de buffles. Cet article présente le schéma du programme de gestion et les fréquences des maladies sélectionnées. Quatre vingt troupeaux ont été choisis; leur élevage était conduit selon la méthode propre aux fermiers de la région. Des assistants vétérinaires ont visité les fermes une fois par mois durant 12 mois pour relever les données sur l'inventaire du bétail, la production, les maladies et les traitements préventifs. L'importance de l'incidence a été utilisée comme méthode pour mesurer la fréquence des maladies. Chez les adultes, les problèmes prédominants dans les conditions indiquées concernaient la reproduction, les mammites et des troubles gastrointestinaux. Les problèmes respiratoires étaient les plus communs chez le jeune bétail. Les veaux des deux espèces présentaient fréquemment des troubles respiratoires et gastrointestinaux. La majorité de la production de veaux des deux espèces étaient perdue dans les trois premiers mois de vie.相似文献
85.
The interactions between six insecticides (indoxacarb, cypermethrin, chlorpyrifos, azinphosmethyl, tebufenozide and chlorfenapyr) and three potential synergists, (piperonyl butoxide (PBO), S,S,S-tributyl phosphorotrithioate (DEF) and diethyl maleate (DEM)) were studied by dietary exposure in a multi-resistant and a susceptible strain of the obliquebanded leafroller, Choristoneura rosaceana (Harris). The synergists did not produce appreciable synergism with most of the insecticides in the susceptible strain. Except for tebufenozide, PBO synergized all the insecticides to varying degrees in the resistant strain. A very high level of synergism by PBO was found with indoxacarb, which reduced the resistance level from 705- to 20-fold when PBO was administered alone and to around 10-fold when used in combination with DEF. DEF also synergized indoxacarb, cypermethrin, chlorpyrifos, azinphosmethyl and tebufenozide in the resistant strain. DEM produced synergism of indoxacarb, chlorpyrifos, azinphos-methyl and chlorfenapyr in the resistant strain. DEM was highly synergistic to cypermethrin, and to some extent to tebufenozide in both the susceptible and resistant strains equally, implying that detoxification by glutathione S-transferases was not a mechanism of resistance for these insecticides. The high level of synergism seen with DEM in the case of cypermethrin may be due to an increase in oxidative stress resulting from the removal of the antioxidant, glutathione. These studies indicate that enhanced detoxification, often mediated by cytochrome P-450 monooxygenases, but with probable esterase and glutathione S-transferase contributions in some cases, is the major mechanism imparting resistance to different insecticides in C. rosaceana. 相似文献
86.
Zoonotic risk of Toxocara canis infection through consumption of pig or poultry viscera 总被引:1,自引:0,他引:1
The potential zoonotic risk of Toxocara canis infections from consumption of swine or poultry viscera containing larvae was assessed using a pig model. Two groups of six pigs were fed either fresh swine viscera (group FS) or poultry viscera (FP) containing around 3500 Toxocara larvae. Another two groups of six pigs were fed swine viscera (PS) or poultry viscera (PP) preserved at 4 degrees C for 1 week. All pigs were necropsied 14 days after the exposure. Liver white spots were counted and T. canis specific IgG antibodies were measured by ELISA. Larval burdens were assessed in the mesenteric lymph nodes, liver, lungs, brain, tongue, and eyes. All recipient pigs exhibited several white spots on the liver surface and detectable antibody levels. Larvae were recovered predominantly from the lungs, but also from the mesenteric lymph nodes and the liver, a few larvae were found in the brain and tongue of the pigs. Two larvae were found in the eyes of two pigs in group FS. Mean percentages of total larval recoveries in groups FS, FP, PS, and PP were 75.3, 63.6, 42.6, and 18.8%, respectively. Significantly higher numbers of larvae were recovered from pigs given swine viscera than pigs given poultry viscera. The preservation at 4 degrees C for 1 week caused a significant reduction in the larval infectivity overall, nevertheless, the recoveries remained substantial. The fact that larvae migrating in swine or poultry organs and tissues have high infectivity in pigs even after preservation at 4 degrees C for 1 week, suggests that human infection with T. canis might easily occur following consumption of raw or undercooked dishes, either fresh or refrigerated, prepared from swine or poultry organs and tissues harbouring T. canis larvae. 相似文献
87.
88.
Molecular and phenotypical characterization of Clostridium perfringens isolates from poultry flocks with different disease status 总被引:1,自引:0,他引:1
Gholamiandekhordi AR Ducatelle R Heyndrickx M Haesebrouck F Van Immerseel F 《Veterinary microbiology》2006,113(1-2):143-152
Due to the diminished use of growth-promoting antibiotics in the European Union, Clostridium perfringens induced necrotic enteritis and subclinical disease have become important threats to poultry health. A study was set up to genotypically and phenotypically characterise C. perfringens isolates from poultry flocks with different health status. Animals from healthy flocks were sampled by cloacal swabs, while intestinal and liver samples of animals suffering from necrotic enteritis were analysed. A total of 27 isolates was obtained from 23 broiler flocks without clinical problems and 36 isolates were obtained from 8 flocks with clinical problems. Using PFGE typing, high genetic diversity was detected between isolates from different flocks. Isolates derived from flocks where disease outbreaks occurred were clonal within each flock, but each flock harboured a different clone. All isolates were of toxin type A. Isolates from 5 out of 35 PFGE types carried the cpb2 gene, encoding the beta2 toxin, and isolates from 2 out of 35 PFGE types harboured the cpe gene, encoding the enterotoxin. In vitro alpha toxin production for all isolates was quantified by enzyme-linked immunosorbent assay. It was shown that in vitro alpha toxin production of C. perfringens isolates from diseased flocks was not higher than in vitro alpha toxin production from isolates derived from healthy flocks. 相似文献
89.
Polymorphism analysis of BMPR1B gene by forced RFLP and PCR-SSCP techniques and expression of the mutation in introgressed sheep 总被引:2,自引:0,他引:2
The present study was conducted to screen Kashmir valley sheep with history of prolificacy for the presence of FecB mutation. Forced polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) and single strand conformation
polymorphism (SSCP) techniques were employed to detect any polymorphism present in bone morphogenetic protein receptor type
1B (BMPR1B) gene. Further, it was aimed at introgressing the FecB mutation into nonprolific noncarrier sheep. A 140-bp fragment of BMPR1B gene was amplified from isolated genomic DNA and subjected to forced RFLP with restriction enzyme AvaII. Three different RFLP patterns were identified. SSCP analysis showed one-to-one correspondence with RFLP patterns. Sequencing
of the samples showing different patterns revealed that the wild (+) and mutant (B) alleles were different by a single nucleotide
substitution in the form of A109G from wild to mutant allele. It led to change in amino acid from Glutamine (Q) to Arginine
(R) from wild to mutant allele. The mutation was only detected in NARI-Suwarna and their crosses; all Kashmir valley sheep
with prolific history lacked it. The + allele was abundant in the studied population. The FecB mutation was introgressed in nonprolific noncarrier sheep by crossing ewes with NARI-Suwarna rams possessing the mutation.
First generation crossing produced heterozygous (B+) progeny. Some of the F1 heterozygous ewes gave birth to twins when mated to unrelated NARI-Suwarna rams. It showed that FecB mutation was successfully expressing in those crosses. 相似文献
90.
Molecular detection of Theileria spp. in sheep and vector ticks in the North Khorasan Province, Iran
A survey was carried in North Khorasan Province, Iran in 2010–2011, designed to identify Theileria spp. infections of both sheep and ticks. The tick species were also examined. Ninety sheep from different flocks were clinically examined, and blood samples and ixodid ticks were collected. Light microscopy of blood smears revealed Theileria spp. infection in 37 (41.1 %), while 74 (82.2 %) of blood samples were positive using semi-nested PCR. Theileria ovis, Theileria lestoquardi, and mixed infection were detected in 63/90 (70 %), 5/90 (5.5 %), and 6/90 (6.6 %) of samples, respectively. Of the 434 ticks that were collected, the most prevalent species was Rhipicephalus turanicus (69.3 %) followed by Hyalomma marginatum turanicum (18.4 %), Dermacentor marginatus (6.4 %), and Rhipicephalus bursa (5.7 %). The ticks were separated into 42 tick pools, and the salivary glands were dissected out in 0.85 % (w/v) saline under a stereomicroscope and examined using semi-nested PCR. Three pools of H. marginatum turanicum salivary glands were infected with T. ovis and T. lestoquardi, and one pool of R. turanicus was infected with T. ovis. Based on these results, it is concluded that the prevalence of T. ovis is higher than T. lestoquardi and that H. marginatum turanicum and R. turanicus are likely vectors of T. lestoquardi and T. ovis in this area. 相似文献