全文获取类型
收费全文 | 156183篇 |
免费 | 8347篇 |
国内免费 | 81篇 |
专业分类
林业 | 6596篇 |
农学 | 4851篇 |
基础科学 | 1078篇 |
18362篇 | |
综合类 | 28510篇 |
农作物 | 6166篇 |
水产渔业 | 7388篇 |
畜牧兽医 | 80027篇 |
园艺 | 1914篇 |
植物保护 | 9719篇 |
出版年
2018年 | 1964篇 |
2017年 | 2137篇 |
2016年 | 2039篇 |
2015年 | 1769篇 |
2014年 | 2092篇 |
2013年 | 5875篇 |
2012年 | 4012篇 |
2011年 | 4934篇 |
2010年 | 3280篇 |
2009年 | 3298篇 |
2008年 | 4980篇 |
2007年 | 4608篇 |
2006年 | 4416篇 |
2005年 | 4156篇 |
2004年 | 4221篇 |
2003年 | 4155篇 |
2002年 | 4036篇 |
2001年 | 4826篇 |
2000年 | 4887篇 |
1999年 | 3795篇 |
1998年 | 1722篇 |
1997年 | 1671篇 |
1996年 | 1549篇 |
1995年 | 1854篇 |
1994年 | 1770篇 |
1993年 | 1680篇 |
1992年 | 3403篇 |
1991年 | 3600篇 |
1990年 | 3625篇 |
1989年 | 3507篇 |
1988年 | 3309篇 |
1987年 | 3280篇 |
1986年 | 3407篇 |
1985年 | 3297篇 |
1984年 | 2715篇 |
1983年 | 2481篇 |
1982年 | 1643篇 |
1981年 | 1558篇 |
1979年 | 2497篇 |
1978年 | 2009篇 |
1977年 | 1688篇 |
1976年 | 1631篇 |
1975年 | 1713篇 |
1974年 | 2093篇 |
1973年 | 2215篇 |
1972年 | 2151篇 |
1971年 | 2078篇 |
1970年 | 1945篇 |
1969年 | 1826篇 |
1967年 | 1613篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A strategy for control of bovine leukemia virus infection: test and corrective management 总被引:2,自引:2,他引:0 下载免费PDF全文
Ruppanner R Behymer DE Paul S Miller JM Theilen GH 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(6):192-195
Test and corrective management was applied in one dairy herd (130 milking cows) to control bovine leukemia virus infection. It consisted of: raising uninfected calves in order to establish a pool of uninfected replacement heifers, preventing transmission of bovine leukemia virus through transfer of blood from animal to animal and closing the herd. Regular herd testing was combined with selected changes in herd management. These procedures have been followed since January 1979. Prevalence of antibodies (as determined by gel-immunodiffusion) has declined markedly since the program was implemented. 相似文献
992.
993.
The duration of immunity to an inactivated adjuvanted canine parvovirus vaccine. A 52 and 64 week postvaccination challenge study 总被引:1,自引:1,他引:0 下载免费PDF全文
Povey RC Carman PS Ewert E 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(8):245-248
Dogs were successfully isolated for a period of either 52 or 64 weeks following vaccination with an inactivated, adjuvanted canine parvovirus-2 vaccine. Antibody persisted in all ten vaccinated dogs, although in one case by 52 weeks postvaccination only virus neutralizing antibody, and not hemagglutination-inhibiting antibody, could be detected. Sentinel unvaccinated dogs housed alongside the vaccinated dogs throughout the study remained free of canine parvovirus-2 antibody until challenged. Upon oral challenge with canine parvovirus-2 infected material all unvaccinated dogs developed one or more signs of canine parvovirus-2 disease, shed virus and developed antibody. None of the vaccinated dogs became overtly sick. Of the five vaccinated dogs challenged 52 weeks after vaccination, three shed virus and one showed a significant rise in antibody. At 64 weeks after vaccination only one of the five challenged dogs shed virus and showed a boost in antibody titer. 相似文献
994.
995.
996.
997.
The Management of Prostaglandin-controlled Breeding Programs in Beef Cattle - A Five Year Study 下载免费PDF全文
Wenkoff M Crowe-Swords PR 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(2):50-53
A herd of 180 beef cows was synchronized with prostaglandin and bred by artifical insemination for five successive years. Factors influencing the success or failure of estrus synchronizing programs were identified, including the management of nutrition, postpartum interval, cow age and artificial insemination technology. Specific recommendations on the management of prostaglandin-controlled breeding programs resulted in improving the pregnancy rates from 33% in year 1 to 67% in year 5. Improved management and close veterinary supervision were shown to improve the success of an estrus synchronization program. 相似文献
998.
Alkaline phosphatase (APase) activity in tissue samples, with adherent bacteria, was measured from two sites in the rumen and from two sites in the abomasum of 57 yearling Angus and Hereford bulls and heifers fed a high or a low energy diet. In the rumen, APase activity was higher at the caudoventral blind sac than at the dorsal sac in animals of both breeds fed the high energy diet and in Angus bulls fed the low energy diet, but the reverse was observed in Hereford bulls fed the low-energy diet (P less than .01). In the abomasum, APase levels were higher for bulls than heifers (P less than .01) and higher at the fundic than at the pyloric region (P less than .01). Morphological studies also showed that rumen samples from animals fed a high energy diet exhibited a more widely distributed APase activity and an increase in the digestive recycling of epithelial cells that produced some "pitting" of the tissue. The higher APase activity of the epithelial tissue of animals fed the high energy diet may be explained by the greater rate of cell death and renewal indicated by the higher mitotic index reported by other researchers who have studied the cell cycle of the rumen epithelium in ruminants fed high and low energy diets. 相似文献
999.
A condition resembling chronic malignant catarrhal fever was seen in a 9-month-old pet sika hind (Cervus nippon). From an initial acute depression, pyrexia, and anorexia, the condition progressed to include hypopyon, keratitis, lethargy, loss of condition, sloughing of one hoof and eventually death after seven weeks. There were multiple, 5 to 8mm diameter dark-red nodules throughout the mesenteries and mediastinum, along abdominal organ ligaments, and about the uterus and kidneys. Histopathology showed the nodules to be organising vascular thrombi. Concurrent perivascular mononuclear infiltrations and intravascular thrombi in many tissues confirmed that the condition was malignant catarrhal fever. 相似文献
1000.