全文获取类型
收费全文 | 181149篇 |
免费 | 10008篇 |
国内免费 | 117篇 |
专业分类
林业 | 7781篇 |
农学 | 5876篇 |
基础科学 | 1168篇 |
22875篇 | |
综合类 | 30096篇 |
农作物 | 7146篇 |
水产渔业 | 9052篇 |
畜牧兽医 | 92559篇 |
园艺 | 2421篇 |
植物保护 | 12300篇 |
出版年
2019年 | 1706篇 |
2018年 | 2571篇 |
2017年 | 2918篇 |
2016年 | 2678篇 |
2015年 | 2276篇 |
2014年 | 2843篇 |
2013年 | 7101篇 |
2012年 | 5218篇 |
2011年 | 6441篇 |
2010年 | 4187篇 |
2009年 | 4318篇 |
2008年 | 6319篇 |
2007年 | 5987篇 |
2006年 | 5564篇 |
2005年 | 5256篇 |
2004年 | 4986篇 |
2003年 | 5194篇 |
2002年 | 4709篇 |
2001年 | 5541篇 |
2000年 | 5536篇 |
1999年 | 4445篇 |
1998年 | 1952篇 |
1997年 | 1904篇 |
1996年 | 1745篇 |
1995年 | 2104篇 |
1994年 | 1838篇 |
1993年 | 1734篇 |
1992年 | 3526篇 |
1991年 | 3774篇 |
1990年 | 3666篇 |
1989年 | 3704篇 |
1988年 | 3397篇 |
1987年 | 3327篇 |
1986年 | 3468篇 |
1985年 | 3325篇 |
1984年 | 2777篇 |
1983年 | 2434篇 |
1982年 | 1690篇 |
1979年 | 2569篇 |
1978年 | 2022篇 |
1977年 | 1772篇 |
1976年 | 1792篇 |
1975年 | 1901篇 |
1974年 | 2254篇 |
1973年 | 2311篇 |
1972年 | 2170篇 |
1971年 | 2048篇 |
1970年 | 1975篇 |
1969年 | 1951篇 |
1967年 | 1764篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
911.
912.
A method for the control of ovine footrot is described which utilises the most appropriate measures to suit the circumstances for individual properties. This approach was used to eradicate the disease from three Central Otago fine-wool properties wintering in excess of 35,000 sheep on widely differing classes of land. This programme incorporates the use of proven.techniques and suitable planning together with input from the rural veterinarian, who plays an important role in demonstration and advising on control measures. 相似文献
913.
The serological identity of 234 strains of Yersinia pseudotuberculosis recovered from domestic animals and birds in New Zealand was determined by slide agglutination test. Thirty strains were also examined by tube agglutination test. The strains were isolated from cattle (56), sheep (8), deer (117), goats (13), pigs (7), rabbits (6), guinea pigs (5), and aviary species of birds (22). All strains were isolated from animals or birds which had died or shown signs of ill health and amongst which diarrhoea was a common feature. Serotype I accounted for 23% (53) of strains, serotype II for 13% (30) of strains and serotype III for 64% (151) of strains. It was concluded that further investigations on the prevalence and serological identity of strains recovered from clinically healthy animals mav provide useful information in assessing the significance of various serotypes as a cause of disease in livestock. 相似文献
914.
915.
Whole bloods from weaned lambs with severe selenium responsive unthriftiness usually contain <5 ng Se/ml. Mildly or moderately affected lambs have blood levels of 5-10 ng/ml. Selenium responsive infertility in ewes appears to be associated with whole blood selenium levels below 10 ng/ml. 相似文献
916.
917.
G Castrucci F Frigeri S Ranucci M Ferrari V Cilli B Pedini P Nettleton F Caleffi V Aldrovandi A J Herring 《Comparative immunology, microbiology and infectious diseases》1984,7(1):1-10
Three strains (479 C, 778 TL, 982 LE) of infectious bovine rhinotracheitis (IBR) virus isolated from latently infected calves were compared with the prototype strain of IBR virus (LA strain) in studies which included restriction endonuclease analysis, experimental infection, and reciprocal cross protection tests in cattle. From the restriction endonuclease analysis it appeared that the 3 "latent" viruses were derived from the same isolate, and that it differed slightly from the LA strain. However, latency does not seem to have affected the pathogenicity or the immunogenicity of the virus. This is demonstrated by the identical clinical and virologic response of calves subjected to experimental infection with the various strains under study, and by the finding that when the LA strain and a "latent" strain (982 LE) were tested in cross protection tests in cattle, they proved to be mutually protective. 相似文献
918.
- An enzymatic ‘reaction rate’ micro-method for the rapid routine estimation of D-B-hydroxybutyrate (D-B-HOB) in ruminant plasma, using an I.L. Multistat III centrifugal analyzer, is described.
- Reaction conditions were optimized to give a linear response for plasma D-B-HOB concentrations between 100 and 2500 μmoles per litre, at 30°C and pH 9.0.
- For the standardized method the within-run and between-run coefficients of variation for deproteinised ovine plasma were consistently less than 3.5%.
- There was good agreement between plasma concentrations obtained by the present method and both original U.V. end-point technique (r=0.927b=0.950) and a colorimetric end-point procedure (r=0.937. b=0.879).
- Utreated ovine and bovine plasma consistently exhibited high ‘blank’ activity and this was directly correlated with plasma lactate dehydrogenase (LDH) activity in both species (r=0.971; p<0.001 and r=0.949; p<0.001 respectively). The distribution of LDH activity in man was similar to sheep but, contrastingly, non-specific interference was extremely low in human plasma and unrelated to LDH. Horse, chicken and rat had negligible ‘blank” activity and comparatively low LDH levels. In both cattle and sheep non-specific interference was abolished by perchloric acid precipitation. In the sheep subtraction of ‘blank’ activity gave D-H-HOB concentrations for untreated plasma comparable to those in deproteinised samples. However, in the bovine, D-B-HOB levels remained significantly (t=6.44; p<0.001) higher even after ‘blank’ correlation. In contrast to man and other non-ruminants, perchloric acid precipitation is essential in ruminants to avoid false overestimation of plasma D-B-HOB levels.
- Plasma with EDTA as anticoagulant and serum gave concentrations of D-B-HOB approximately 60% lower, than samples containing heparin or oxalate/fluoride. However, heparin was associated with much higher (up to 50%) non-specific NAD rduction than oxalate/fluoride.
- High levels of acetoacetate (400–1000 μmoles per litre) reduced the recovery of D-B-HOB from ovine plasma by less than 10%. This effect was negated by the inclusion of hydrazine hydrates in the reaction mixture. Perchlorate ion concentrations above 25 μmoles per litre per test dramatically inhibited the assay in ovine plasma, and therefore precipitation conditions must be carefully controlled.
- Plasma with oxalate/fluoride as anticoagulant showed the greatest stability in storage; 24 hours at room temperature, one week at +4°C and at least one month at ?20°C.
919.
Guy PA 《New Zealand veterinary journal》1984,32(6):81-84
Ollulanus tricuspus is a parasite of the stomach of domestic cats and other animals, with a worldwide distribution. It can sometimes cause severe gastritis. Fifty-five cat stomachs were examined for O.tricuspis using three techniques. O.tricuspis was found in seven stomachs (13%) from adult cats; the number of parasites recovered from individual cats ranged from 9 to 119 (mean 54). The prevalence was higher than that previously recorded in New Zealand. Repeated dilution and sedimentation of the stomach contents and mucosal washings was found to be the most reliable detection method, being positive in all of the detected infections. Pepsin/HCI digestion of the stomach mucosa detected only 71% and punch sampling of the mucosa only 29% of these infections. This contrasts with an overseas study indicating that, in heavily infected cats, these techniques are similar in sensitivity. No macroscopic lesions were seen in the stomachs of infected cats. 相似文献
920.
Clinical hypocalcaemia was associated with single doses of three oi more days; supply of zinc oxide to dairy cows for facial eczema control. Experimental hand dosing of a single dose of zinc oxide (40 and 120 mg Zn/kg b wt) to Jersey cows caused a significant drop in serum calcium concentration at 24 h followed by a rise to concentrations higher than controls at subsequent samplings over four days. At the highest zinc dose rate, 78% of serum calcium values were equal to or lower than the lowest control value at 24 h post dosing. Serum magnesium concentrations had a reciprocal relationship to the calcium levels at all samplings. Serum zinc concentrations were most elevated over the 48 h post dosing, returning to normal levels at the fifth day. Following the highest zinc dose milk yields were reduced by approximately 1.5 kg milk/cow/day for 48 h. Similar results were obtained when cows grazed pasture on which large amounts of zinc oxide had been sprayed. 相似文献