全文获取类型
收费全文 | 184646篇 |
免费 | 9742篇 |
国内免费 | 123篇 |
专业分类
林业 | 7274篇 |
农学 | 5378篇 |
基础科学 | 1280篇 |
20772篇 | |
综合类 | 35583篇 |
农作物 | 6948篇 |
水产渔业 | 8748篇 |
畜牧兽医 | 93923篇 |
园艺 | 2199篇 |
植物保护 | 12406篇 |
出版年
2018年 | 2096篇 |
2017年 | 2304篇 |
2016年 | 2178篇 |
2015年 | 1887篇 |
2014年 | 2298篇 |
2013年 | 6537篇 |
2012年 | 4469篇 |
2011年 | 5580篇 |
2010年 | 3495篇 |
2009年 | 3508篇 |
2008年 | 5489篇 |
2007年 | 5240篇 |
2006年 | 5155篇 |
2005年 | 4816篇 |
2004年 | 4701篇 |
2003年 | 4760篇 |
2002年 | 4655篇 |
2001年 | 5435篇 |
2000年 | 5245篇 |
1999年 | 4333篇 |
1998年 | 1777篇 |
1997年 | 1817篇 |
1995年 | 2087篇 |
1994年 | 1919篇 |
1993年 | 1829篇 |
1992年 | 3881篇 |
1991年 | 4033篇 |
1990年 | 4146篇 |
1989年 | 4134篇 |
1988年 | 3845篇 |
1987年 | 3898篇 |
1986年 | 3975篇 |
1985年 | 3852篇 |
1984年 | 3276篇 |
1983年 | 2921篇 |
1982年 | 2001篇 |
1981年 | 1884篇 |
1980年 | 1823篇 |
1979年 | 2985篇 |
1978年 | 2490篇 |
1977年 | 2184篇 |
1976年 | 1962篇 |
1975年 | 2123篇 |
1974年 | 2782篇 |
1973年 | 2767篇 |
1972年 | 2777篇 |
1971年 | 2550篇 |
1970年 | 2412篇 |
1969年 | 2167篇 |
1967年 | 1903篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Twenty-nine pruritic, atopic dogs were entered into a double-blind, placebo-controlled, crossover study to evaluate the efficacy of an investigational antiallergenic compound, AHR-13268. Fourteen dogs were evaluated by a veterinary dermatologist (at intervals) and the owner (daily). Fifteen dogs were evaluated only by the owner. The mean (+/- SE) owner scores for pruritus, erythema, and lesions with placebo treatment (higher score = worse signs) were 3.24 (+/- 0.12), 2.73 (+/- 0.12), and 2.61 (+/- 0.09), respectively. With drug treatment, the corresponding scores were 2.89 (+/- 0.12), 2.50 (+/- 0.12), and 2.25 (+/- 0.09). Scores for pruritus and lesions (but not erythema) were significantly better with drug treatment than with placebo treatment. Investigator scores showed similar trends, but the differences were not great enough to be statistically significant. Overall, 11/29 (38%) owners reported their dogs had moderate or better improvement from drug capsules, and 4/29 dogs (14%) improved on placebo capsules. A variety of adverse effects were reported following both drug (9/29 dogs) and placebo (8/29 dogs) capsule administration, but were mild and well tolerated. Results of this study indicate that AHR-13268 has potential for empiric treatment of allergic inhalant dermatitis in some dogs. 相似文献
152.
G. J. Glova 《Ecology of Freshwater Fish》2003,12(4):247-253
Abstract – The interaction between brown trout ( Salmo trutta ; fork length (FL) range 255–390 mm) and inanga ( Galaxias maculatus ; FL range 55–115 mm) was tested during summer through autumn in an artificial stream consisting of a single run-riffle-pool sequence with a natural food supply. Each experimental trial lasted for 15 days, and consisted of two brown trout and 50 inanga collected fresh from a nearby stream, with each species given prior residence in four replicate tests, totalling eight trials in all. In addition, two control trials (each 10 days), with 50 inanga in each, were run. Brown trout almost exclusively occupied the pool, whereas inanga occupied all habitat types, although in different proportions, when tested with and without brown trout. The proportion of inanga in the pool was appreciably lower in the experimental trials with brown trout than in the control trials with no brown trout; prior residence had no significant effect on inanga habitat use. Mortality of inanga attributable to predation by brown trout ranged from 0 to 40% with a mean of 14.5 ± 4.7%. The results suggest that habitat use and survival of inanga populations in small streams can be adversely affected by brown trout. 相似文献
153.
P R Widders S C Dowling R P Gogolewski J W Smith L B Corbeil 《Research in veterinary science》1989,46(2):212-217
Bovine antibody responses to Haemophilus somnus were compared on the basis of clinical and bacteriological findings. Serum IgG1 and IgM antibody titres were significantly increased in clinically normal cattle that were bacteriologically positive for H somnus from the nasal or vaginal mucosae compared with clinically normal, negative cows. IgG2 titres did not differ significantly between these two groups. However, IgG2 antibody was significantly higher in animals with H somnus disease (pneumonia or abortion) than in clinically normal cattle (whether bacteriologically positive or negative), while IgG1 and IgM titres did not differ between diseased and bacteriologically positive, clinically normal cattle. These antibody trends were duplicated in experimental H somnus abortion or pneumonia, with the greatest response occurring within the IgG2 subclass. Cattle vaccinated systemically with killed whole H somnus produced a predominant IgG2 response with minimal IgG1 and IgM responses. These results demonstrate that IgG2 antibody is consistently elevated in H somnus disease, and suggest that this response may be useful in discriminating diseased from asymptomatic cattle. 相似文献
154.
Bilateral nephrolithiasis with intermittent ureterolithiasis was diagnosed in a 7-year old Holstein cow. Two episodes of ureterolithiasis resulted in severe azotemia which resolved after spontaneous movement of the stone. A third episode of obstruction one year after the initial episode resulted in rupture of one kidney, necessitating euthanasia. The histopathological examination of the kidney was diagnostic for chronic pyelonephritis. Corynebacterium sp. was cultured from a nephrolith. In this case it is believed that the chronic pyelonephritis predisposed to the calculi formation. 相似文献
155.
156.
157.
Effect of a new pelleting process on the level of contamination of poultry mash by Escherichia coli and Salmonella 总被引:2,自引:0,他引:2
R H McCapes H E Ekperigin W J Cameron W L Ritchie J Slagter V Stangeland K V Nagaraja 《Avian diseases》1989,33(1):103-111
The efficacy of a new pelleting process in eliminating naturally occurring Escherichia coli and salmonella from poultry mash was assessed by comparing the microbial load in raw and processed mash. Instead of using steam produced in a boiler, the new process conditioned mash in an Original Vertical Conditioner with steam and other hot gases generated by direct combustion in a Vaporator. E. coli was isolated from 72-100% of samples of raw mash in all trials, and the mean number of colony-forming units of E. coli/g of samples was 6.8 +/- 4.0 X 10(4). Salmonellae (S. senftenberg, S. bredeney, and S. mbandaka) were isolated from 5-10% of samples of raw mash utilized in three of the seven trials. Within limitations of the sampling and analytical tests utilized, the new pelleting process eliminated salmonella from all mash in which the organism was known to be present but eliminated E. coli in only three trials. The process appeared to be 100% effective against both organisms when mash entering the pellet mill from the conditioner had a temperature of 85.7 C and a moisture content of 14.5% and had been retained and treated with steam and hot gases for 4.1 minutes. 相似文献
158.
Y Zhou V Moennig C O Coulibaly J Dahle B Liess 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1989,36(1):76-80
Monoclonal antibodies against hog cholera and bovine viral diarrhoea viruses were assayed on organ tissue sections of experimentally infected animals. The animals had been infected simultaneously with both viruses. The antibodies were tested using an indirect immunofluorescence test and an indirect enzyme immunoassay with a biotin/streptavidin/peroxidase detection system. A polyclonal hyperimmune serum was used as a control in direct immunofluorescence tests. Both techniques based on monoclonal antibodies were more sensitive and more specific than the conventional test, the enzyme immunoassay being more sensitive than the immunofluorescence test. Small amounts of BVD viral antigen were demonstrable with monoclonal antibodies in most organ tissues. 相似文献
159.
160.