全文获取类型
收费全文 | 117389篇 |
免费 | 7182篇 |
国内免费 | 325篇 |
专业分类
林业 | 4936篇 |
农学 | 4405篇 |
基础科学 | 875篇 |
15257篇 | |
综合类 | 17918篇 |
农作物 | 4455篇 |
水产渔业 | 6171篇 |
畜牧兽医 | 61727篇 |
园艺 | 1517篇 |
植物保护 | 7635篇 |
出版年
2020年 | 1047篇 |
2019年 | 1299篇 |
2018年 | 2077篇 |
2017年 | 2361篇 |
2016年 | 2131篇 |
2015年 | 1821篇 |
2014年 | 2252篇 |
2013年 | 5025篇 |
2012年 | 3810篇 |
2011年 | 4584篇 |
2010年 | 3075篇 |
2009年 | 3098篇 |
2008年 | 4474篇 |
2007年 | 4091篇 |
2006年 | 3961篇 |
2005年 | 3424篇 |
2004年 | 3269篇 |
2003年 | 3283篇 |
2002年 | 3036篇 |
2001年 | 4202篇 |
2000年 | 4124篇 |
1999年 | 3179篇 |
1998年 | 1270篇 |
1997年 | 1366篇 |
1996年 | 1137篇 |
1995年 | 1301篇 |
1994年 | 1155篇 |
1993年 | 1096篇 |
1992年 | 2319篇 |
1991年 | 2478篇 |
1990年 | 2349篇 |
1989年 | 2394篇 |
1988年 | 2091篇 |
1987年 | 2067篇 |
1986年 | 2107篇 |
1985年 | 1974篇 |
1984年 | 1586篇 |
1983年 | 1351篇 |
1979年 | 1511篇 |
1978年 | 1187篇 |
1976年 | 997篇 |
1975年 | 1134篇 |
1974年 | 1283篇 |
1973年 | 1277篇 |
1972年 | 1182篇 |
1971年 | 1074篇 |
1970年 | 1098篇 |
1969年 | 1106篇 |
1968年 | 1001篇 |
1967年 | 1029篇 |
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
881.
Dimski DS Brooks CL Johnson SE 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1990,19(2):40-44
Type III procollagen peptide (P-3-P) is a serum marker for hepatic fibrosis in humans. The utility of a commercially available radioimmunoassay for P-3-P was evaluated in the dog. The specificity of the assay was assessed by polyacrylamide gel electrophoresis (PAGE) of canine serum and purified bovine P-3-P, followed by Western immunoblotting with rabbit aniti-P-3-P serum. The sensitivity was assessed by performing the radioimmunoassay on dilutions of sera from 22 dogs. Polyacrylamide gel electrophoresis of purified bovine P-3-P and sera from two dogs suspected of having elevated P-3-P concentrations revealed no homologous bands of staining. Western immunoblotting showed marked cross-reactivity of the high antisera concentrations with several components of the serum proteins, but none corresponding to the purified P-3-P. All tested sera from dogs had minimal competitive binding with radiolabeled P-3-P in the radioimmunoassay. Dilution curves of dog sera did not parallel either the standard curve or the dilution curve of a known test human serum. There were no statistically different P-3-P concentrations in any of the groups of dogs studied. It was concluded that currently available radioimmunoassay kits for the measurement of P-3-P in the human are not applicable in the dog. Seemingly, the structure or metabolism of canine P-3-P may vary significantly from that of the bovine or human, limiting the sensitivity and specificity of this assay in the dog. 相似文献
882.
The efficacy of a topical formulation of ivermectin against naturally acquired gastro-intestinal nematodes in weaner cattle was evaluated. At slaughter, 14-15 days after treatment, burdens of Ostertagia spp, Trichostrongylus axei and Oesophagostomum radiatum were significantly lower in the treated calves than in the untreated controls (p<0.01). Efficacies (based on geometric mean worm burdens of treated and control groups) were 99.6%, 95.1% and 100% respectively. The sizes of the Cooperia spp and Trichuris ovis burdens in the treated group did not differ significantly at the 5% level of confidence from those in the control group. 相似文献
883.
D'Allaire S Leman AD 《The Canadian veterinary journal. La revue veterinaire canadienne》1990,31(8):581-583
This investigation was conducted to study boar culling patterns in swine breeding herds. Data were obtained from 84 swine breeding herds and included 440 boars that were culled. Each producer was involved for 12 consecutive months, and recorded every boar that was removed from the herd, the date, and the reason for culling. The annual culling rate for the 84 farms averaged 59.4% ± 6.4 (SEM). The correlation coefficient between boar and sow culling was 0.52 (p <0.0001). Removal was the result of being overweight (47%), reproductive problems (18%), leg problems (12%), death (7%), and other diseases (4%). From the annual culling rate, the average breeding life of boars was estimated at 20 months. From this study, we concluded that the annual culling rate for boars in commercial herds was high and related to several different factors. 相似文献
884.
885.
Ribble CS 《The Canadian veterinary journal. La revue veterinaire canadienne》1990,31(10):679-681
886.
887.
888.
Chalmers GA Nation PN Pritchard J 《The Canadian veterinary journal. La revue veterinaire canadienne》1990,31(4):292-295
Terminal ileitis was diagnosed in three flocks of lambs in different areas of Alberta. Salient clinical features in affected lambs were progressive emaciation with diarrhea, and in some lambs, frequent abdominal stretching. Postmortem findings included thickening of the ileal, and in some animals, the jejunal, cecal and colonic mucosa as a result of mucosal infiltrates of many lymphocytes and fewer plasma cells, eosinophils, globular leukocytes, and neutrophils. Hyperplasia of intestinal lymphoid tissue was prominent in most affected lambs. The cause of the condition is unknown. 相似文献
889.
890.