全文获取类型
收费全文 | 178453篇 |
免费 | 9628篇 |
国内免费 | 129篇 |
专业分类
林业 | 7832篇 |
农学 | 5738篇 |
基础科学 | 1093篇 |
22300篇 | |
综合类 | 29227篇 |
农作物 | 7137篇 |
水产渔业 | 8954篇 |
畜牧兽医 | 91612篇 |
园艺 | 2486篇 |
植物保护 | 11831篇 |
出版年
2019年 | 1671篇 |
2018年 | 2651篇 |
2017年 | 3018篇 |
2016年 | 2718篇 |
2015年 | 2412篇 |
2014年 | 2880篇 |
2013年 | 7132篇 |
2012年 | 5468篇 |
2011年 | 6508篇 |
2010年 | 4158篇 |
2009年 | 4200篇 |
2008年 | 6134篇 |
2007年 | 5785篇 |
2006年 | 5471篇 |
2005年 | 5711篇 |
2004年 | 5391篇 |
2003年 | 5347篇 |
2002年 | 4593篇 |
2001年 | 5346篇 |
2000年 | 5327篇 |
1999年 | 4302篇 |
1998年 | 1890篇 |
1997年 | 1790篇 |
1996年 | 1665篇 |
1995年 | 1970篇 |
1994年 | 1783篇 |
1993年 | 1633篇 |
1992年 | 3488篇 |
1991年 | 3701篇 |
1990年 | 3545篇 |
1989年 | 3530篇 |
1988年 | 3262篇 |
1987年 | 3209篇 |
1986年 | 3328篇 |
1985年 | 3261篇 |
1984年 | 2648篇 |
1983年 | 2364篇 |
1979年 | 2479篇 |
1978年 | 2005篇 |
1977年 | 1738篇 |
1976年 | 1772篇 |
1975年 | 1881篇 |
1974年 | 2229篇 |
1973年 | 2208篇 |
1972年 | 2095篇 |
1971年 | 1933篇 |
1970年 | 1886篇 |
1969年 | 1902篇 |
1968年 | 1638篇 |
1967年 | 1702篇 |
排序方式: 共有10000条查询结果,搜索用时 189 毫秒
291.
Serum amyloid A protein concentration measured by radial immunodiffusion in Abyssinian and non-Abyssinian cats 总被引:1,自引:0,他引:1
S P DiBartola J A Reiter J B Cornacoff G J Kociba M D Benson 《American journal of veterinary research》1989,50(8):1414-1417
Serum amyloid A (SAA) protein concentration was determined by use of radial immunodiffusion (RID) in 4 groups of cats: Abyssinian cats with amyloidosis, healthy Abyssinian cats without clinical evidence of amyloidosis, hospitalized non-Abyssinian cats, and clinically normal non-Abyssinian cats. Mean SAA concentration in Abyssinian cats with amyloidosis was significantly (P = 0.05) higher than mean SAA concentration in healthy Abyssinian cats without clinical evidence of amyloidosis and in hospitalized non-Abyssinian cats. Mean SAA concentration in clinically normal non-Abyssinian cats was significantly (P = 0.05) lower than mean SAA concentration in healthy Abyssinian cats without clinical evidence of amyloidosis and in hospitalized non-Abyssinian cats. Affected and healthy Abyssinian cats, however, could not reliably be distinguished on the basis of SAA concentration, because of the wide range of SAA values in these 2 groups of cats. 相似文献
292.
Effects of epidural xylazine on EEG responses to surgical stimulation during isoflurane anaesthesia in dogs 总被引:1,自引:0,他引:1
K. A. Otto S. Piepenbrock B. Rischke C. Bötel† 《Veterinary anaesthesia and analgesia》1997,24(1):33-38
The effects of epidural administration of 250 μg/kg xylazine on EEG responses to surgical stimulation of 5 different intensities were evaluated during isoflurane anaesthesia for an experimental orthopaedic procedure in dogs. The dogs were assigned randomly to one of 2 treatment groups receiving either xylazine (n = 4) or equal volumes of sterile water (n = 4) (control group) epidurally. Intense surgical stimulation during removal of a bone graft from the dorsoiliac spine of the ileum was associated with a significantly (P = 0.0339) higher increase in EEG alpha/delta ratio after epidural administration of sterile water than after epidural injection of 250 μg/kg of xylazine. In addition, the preincision baseline values for 80% spectral edge frequency were significantly (P = 0.0339) lower in the xylazine group compared to control dogs. Our results suggest that epidural administration of 250 μg/kg of xylazine during orthopaedic procedures in dogs exerts antinociceptive effects which may be in part mediated by a supraspinal effect of xylazine. 相似文献
293.
294.
J Jieyuan P B Spradbrow 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1992,39(5):388-390
Chickens were given various fowlpox vaccines on food pellets--a commercial vaccine (strain M), and the same strain after a single passage on chorio-allantoic membrane or in chicken embryo fibroblasts. All three oral vaccines induced antibodies at levels similar to those induced by commercial strain M administered to the wingweb. The oral vaccine derived from chorio-allantoic membrane gave protection similar to that obtained with vaccine administered by the wingweb, but this required a thousandfold more virus. 相似文献
295.
296.
T Ishida A Taniguchi S Matsumura T Washizu I Tomoda 《Veterinary immunology and immunopathology》1992,35(1-2):15-22
Eleven feline immunodeficiency virus (FIV) infected asymptomatic carrier (AC) cats were observed for 2 years for development of acquired immunodeficiency syndrome (AIDS). Four of the 11 (36.4%) showed progression of the clinical stage. Persistent generalized lymphadenopathy was noted in three cats as the first sign of illness after the AC phase, while the other showed lymphadenopathy with signs of AIDS-related complex. In all four cats the AIDS-related complex stage lasted for 10 months or longer, and two showed progression of the disease into AIDS. The two cats showing AIDS illnesses died within approximately 1 year after they had developed persistent generalized lymphadenopathy. Pathology confirmed the diagnosis of AIDS characterized by the presence of depletion lesions in the lymphoid organs, and of severe infections of an opportunistic nature. The overall mortality of FIV infected AC cats during a 2 year period was two out of 11 (18.2%). These cats showed decreased concanavalin A mitogen response of peripheral blood mononuclear cells as the disease progressed. 相似文献
297.
Two outbreaks of the egg drop syndrome were observed in quail flocks maintained on a farm together with chickens. The decrease in egg production ranged from 10.6 per cent to 50.6 per cent, and the number of soft-shelled eggs increased with the decline in egg production. In both the outbreaks haemagglutination inhibiting antibodies to EDS-76 virus were detected. Fluorescent viral antigen specific to EDS-76 virus was also detected in the lining epithelial and glandular cells of the uterus. 相似文献
298.
299.
Sera from 74,502 cattle from 3087 farms in England and Wales were tested for the presence of antibodies against Hypoderma bovis in the spring of 1988. Twenty-nine positive sera were identified on 18 premises and these animals were treated; an examination of 6030 sera taken from 108 neighbouring herds identified another 17 seropositive animals on 10 farms in Devon, Cornwall, Lancashire, Shropshire and Powys, indicating that these counties still harbour populations of warble fly. 相似文献
300.
A W Mills 《Veterinary Clinics of North America: Small Animal Practice》1992,22(6):1297-1307
The impact and relevance of dentistry in a general feline practice is detailed. Hospital policy and protocol are described for client education, preanesthetic evaluation, dental procedures, and recall programs. A discussion of commonly observed feline dental problems is included. 相似文献