全文获取类型
收费全文 | 118363篇 |
免费 | 7290篇 |
国内免费 | 338篇 |
专业分类
林业 | 5026篇 |
农学 | 4485篇 |
基础科学 | 885篇 |
15411篇 | |
综合类 | 17949篇 |
农作物 | 4440篇 |
水产渔业 | 6421篇 |
畜牧兽医 | 62159篇 |
园艺 | 1536篇 |
植物保护 | 7679篇 |
出版年
2020年 | 1067篇 |
2019年 | 1316篇 |
2018年 | 2123篇 |
2017年 | 2402篇 |
2016年 | 2173篇 |
2015年 | 1845篇 |
2014年 | 2289篇 |
2013年 | 5162篇 |
2012年 | 3869篇 |
2011年 | 4649篇 |
2010年 | 3131篇 |
2009年 | 3130篇 |
2008年 | 4539篇 |
2007年 | 4146篇 |
2006年 | 4025篇 |
2005年 | 3503篇 |
2004年 | 3333篇 |
2003年 | 3363篇 |
2002年 | 3121篇 |
2001年 | 4292篇 |
2000年 | 4176篇 |
1999年 | 3205篇 |
1998年 | 1274篇 |
1997年 | 1324篇 |
1996年 | 1115篇 |
1995年 | 1314篇 |
1994年 | 1158篇 |
1993年 | 1096篇 |
1992年 | 2328篇 |
1991年 | 2489篇 |
1990年 | 2351篇 |
1989年 | 2398篇 |
1988年 | 2098篇 |
1987年 | 2071篇 |
1986年 | 2113篇 |
1985年 | 1981篇 |
1984年 | 1596篇 |
1983年 | 1361篇 |
1979年 | 1517篇 |
1978年 | 1189篇 |
1976年 | 999篇 |
1975年 | 1137篇 |
1974年 | 1286篇 |
1973年 | 1279篇 |
1972年 | 1186篇 |
1971年 | 1077篇 |
1970年 | 1101篇 |
1969年 | 1117篇 |
1968年 | 1003篇 |
1967年 | 1035篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
R. J. Rogers S. G. Knott † F. W. Eaves R. C. Clague ‡ 《Australian veterinary journal》1978,54(12):562-565
SUMMARY A severe cattle mortality in which 132 out of 340 animals died on a property in southern Queensland was investigated. Clinical signs shown by affected animals included fever, inappetance, depression, lethargy, salivation, diarrhoea, ataxia, and ulceration of the oral cavity. The most common lesions seen at autopsy of 6 affected animals were ulceration of the tongue, gums, dental pad and buccal mucosa, linear ulceration of the caudal third of the oesophagus, mild catarrhal enteritis and necrosis of lymph nodes draining areas of ulceration. Bovine herpesvirus type 1 (BHV 1) was isolated from 3 out of 5 animals from which virus isolation was attempted. BHV 1 was recovered from oesophageal ulcers, retropharyngeal lymph nodes, blood clot, and swabs from ulcers in the oral cavity but not from spleen, liver or mesenteric lymph node. Serum neutralising (SN) antibody to BHV 1 was detected in 4 out of 12 affected animals in the second of paired serum samples but not in the first. Mucosal Disease (MD) virus was not recovered from any of 17 animals from which isolation was attempted but moderate MD SN titres, without a rise on paired sera, were detected in affected animals. Fever, depression, inappetance, ulceration of the upper alimentary tract, and adrenal necrosis were produced in 2 susceptible animals following inoculation with third passage cell culture fluid containing BHV 1. A serological response to BHV 1, but not to MD virus was detected in one of the cattle infected experimentally. 相似文献
992.
993.
N H Nabbut 《American journal of veterinary research》1978,39(5):893-895
Animal feed-additive samples (n = 300) were examined for the presence of salmonellae, using the selenite-F broth-enrichment method followed by subculturing on Salmonella-Shigella and brilliant green agar with sulfadiazine selective agar plates. Samples consisted of a variety of feed additives: 119 bone meal samples, 77 meat meal samples, 40 fish meal samples, and 64 miscellaneous meal samples. Results of examination found 49 (41.2%) of the bone meal samples, 6 (7.8%) of the meat meal samples and 2 (5%) of the fish meal samples contained salmonellae. Of 57 isolates representing 24 serotypes, 4 most frequently isolated serotypes were Salmonella meleagridis (35.1%), Salmonella tennessee (7%), Salmonella chester (5.2%), and Salmonella senftenberg (5.2%). This study shows a high Salmonella-contamination rate of bone meal compared with meat meal and fish meal samples. Of 12 known positive bone meal samples that were examined, 100% of 25-g samples, compared with 70% to 100% of 2.5-g samples and 30% to 90% of 0.25-g samples and 30% to 90% of 0.25-g samples, were positive for salmonellae. 相似文献
994.
995.
P J Ihrke R M Schwartzman K McGinley L N Horwitz R R Marples 《American journal of veterinary research》1978,39(9):1487-1489
Quantitative and qualitative bacterial assays were performed on the skin of 15 normal and 32 seborrheic dogs. Nonionic detergent scrubs were made on areas demarcated by glass sidearm cylinders. Quantitative analysis was accomplished by the serial dilution technique, and the bacteria were identified by individual and colonial morphology and by enzyme production. Areas measured on control dogs had a markedly lower total bacterial count than similar areas measured on seborrheic animals. Control dogs had a flora consisting primarily of coagulase-negative cocci, whereas seborrheic dogs usually had a cutaneous flora composed primarily of Stahylococcus aureus, coagulase-positive. 相似文献
996.
J S Brar D W Johnson C C Muscoplat R E Shope J C Meiske 《American journal of veterinary research》1978,39(2):241-244
The immune response to modified live-virus bovine viral diarrhea (BVD) vaccine and infectious bovine rhinotracheitis (IBR) vaccine was examined in calves that had received passive maternal antibodies to these viruses. Blood serum samples from vaccinated and control (nonvaccinated) calves were examined for more than 1 year to determine the rate of decline of passive anti-BVD and anti-IBR antibodies and the effect that vaccination had on these antibody titers. The control calves lost their antibodies to BVD and IBR viruses at the rate of one half their remaining antibody titer every 21 days. Calves serologically responded to BVD vaccine at a time when maternal antibody titers remained between 1:96 and 1:20. However, animals did not seroconvert to the IBR vaccine until maternal antibodies had decreased and become undetectable. Evidence is presented to show that although passive immunity will inhibit IBR vaccination, priming for a secondary response will occur so that on subsequent vaccination, at a time when maternal antibodies have disappeared, the animals will respond anamnestically to IBR vaccination. 相似文献
997.
998.
The development of bovine leukemia virus (BLV) infection was studied in 14 noninfected young adult cattle exposed to 25 to 30 BLV-infected cows in an area of approximately 0.5 ha. Of 7 cattle (group 1) exposed beginning in July and August (midsummer) of 1976, 4 were infected by October, and all 7 by November (4 months' exposure). Of 7 cattle (group 2) exposed from February 1977 (midwinter), all remained negative for 3 months, and only 1 was positive after 6 months. By October 1977, however, 4 cattle in this group were infected, indicating that contact transmission of BLV is prevalent during the summer months. This, and the fact that BLV-infected lymphocytes were recovered from tabanids allowed to feed on a BLV-positive cow, supports the idea that bloodsucking insects play a major role in the spread of BLV. 相似文献
999.
1000.
An in utero technique was developed that allows direct access to the canine fetus for experimentation. This procedure reduces the need for fetal manipulation and umbilical blood flow compromise and reduces fetal fluid loss. In pregnant bitches, uterine horns could be delivered through a ventral midline incision. By manipulating the fetal membranes, and positioning the fetuses through them, electrodes could be inserted subcutaneously in the fetuses. Electrocardiograms satisfactory for interpretation were obtained from as many as 4 fetuses in a bitch for periods up to postoperative week 3. 相似文献