全文获取类型
收费全文 | 148652篇 |
免费 | 7967篇 |
国内免费 | 82篇 |
专业分类
林业 | 6213篇 |
农学 | 4366篇 |
基础科学 | 933篇 |
16656篇 | |
综合类 | 28314篇 |
农作物 | 5707篇 |
水产渔业 | 6744篇 |
畜牧兽医 | 77092篇 |
园艺 | 1765篇 |
植物保护 | 8911篇 |
出版年
2018年 | 1857篇 |
2017年 | 1982篇 |
2016年 | 1858篇 |
2015年 | 1668篇 |
2014年 | 1890篇 |
2013年 | 5639篇 |
2012年 | 3756篇 |
2011年 | 4621篇 |
2010年 | 3013篇 |
2009年 | 2965篇 |
2008年 | 4552篇 |
2007年 | 4271篇 |
2006年 | 4017篇 |
2005年 | 3784篇 |
2004年 | 3825篇 |
2003年 | 3810篇 |
2002年 | 3693篇 |
2001年 | 4501篇 |
2000年 | 4523篇 |
1999年 | 3483篇 |
1998年 | 1498篇 |
1997年 | 1514篇 |
1995年 | 1717篇 |
1994年 | 1586篇 |
1993年 | 1535篇 |
1992年 | 3163篇 |
1991年 | 3439篇 |
1990年 | 3330篇 |
1989年 | 3385篇 |
1988年 | 3084篇 |
1987年 | 3083篇 |
1986年 | 3276篇 |
1985年 | 3191篇 |
1984年 | 2598篇 |
1983年 | 2419篇 |
1982年 | 1573篇 |
1981年 | 1500篇 |
1979年 | 2370篇 |
1978年 | 1941篇 |
1977年 | 1654篇 |
1976年 | 1641篇 |
1975年 | 1688篇 |
1974年 | 2155篇 |
1973年 | 2185篇 |
1972年 | 2145篇 |
1971年 | 2024篇 |
1970年 | 1946篇 |
1969年 | 1793篇 |
1968年 | 1500篇 |
1967年 | 1570篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
981.
982.
983.
The Management of Prostaglandin-controlled Breeding Programs in Beef Cattle - A Five Year Study
下载免费PDF全文
![点击此处可从《The Canadian veterinary journal. La revue veterinaire canadienne》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
984.
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
985.
986.
Hirsch VM McLaughlin BG Parent J 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(10):301-304
Lymphosarcoma in a six year old male Doberman pinscher was accompanied by hypercalcemia, generalized osteolysis and renal calcification. Tumor involvement of bone marrow was extensive. The possible pathogenesis of hypercalcemia was thought to be the result of a locally active bone-resorbing factor secreted by the tumor cells. 相似文献
987.
Joseph M Watson R 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(11):366-367
988.
This paper concerns the taxonomic status of the F38-like group (MacOwan), a prime determinant of contagious caprine pleuropneumonia (CCPP). Extensive biochemical and serological investigations on strain F38 are reported. Some complex serological relationships with other mycoplasma species are revealed. The results, taken in conjunction with earlier published work on geno-typic characters, lead to the conclusion that final classification of these organisms should await further comparative studies of a number of field strains with a related group of strains classified as M. capri-colum.The characterization of F38 confirms its partial relationship to the “M. mycoides group” of ovine/caprine/bovine mycoplasmas, and has also revealed a very close phenotypic relationship to the bovine mycoplasma serogroup 7, a finding of potential diagnostic and epidemiological importance.Key words: mycoplasmas, classification, F38-like group 相似文献
989.
Data obtained from faecal samples from 508 domestic cats and 481 dogs, previously found to have a high frequency of Sarcocystis spp. infections, were further examined to provide information on levels of sporocyst shedding and to ascertain the influence of host, environmental and seasonal factors on the prevalence of naturally acquired infections. Statistical analysis of prevalence data revealed that, of the factors examined, only host age in cats exerted any apparent influence. Infections were significantly more common in cats up to, rather than over, 6 months of age. Although they tended to be greater in dogs than cats, faecal sporocyst counts in both hosts were generally low, with the majority of infected samples containing 200 sporocysts per gram or less. In infected dogs the highest count recorded was 144,600/g with a mean of 2270/g, and in infected cats it was 11,100/g with a mean of 597/g. 相似文献
990.
Skerman TM Millar KR Sheppard AD Herceg M Hughes JM 《New Zealand veterinary journal》1983,31(4):54-57
Two groups of adult Merino sheep, initially grazed on pasture, were dosed daily with zinc sulphate (1 mg Zn/kg LW) or zinc oxide (15 mg Zn/kg LW) for six and seven weeks, respectively. On the 18th day, both groups were transferred to indoor pens together with unmedicated control sheep, and five days later the feet of all animals were infected artificially with a virulent strain of Bacteroides nodosus. By the fourth week after challenge, 85% or more of the feet challenged had developed advanced footrot, and no significant differences in the incidence and severity of lesions between dosed and un-dosed groups were recorded. Plasma zinc concentrations, monitored throughout the experiment, remained at similar levels in sheep receiving the lower dose rate and in the controls. At the higher dose rate, plasma zinc levels increased till Day 23, but thereafter declined to values comparable to those of undosed animals. At post mortem, no evidence of zinc toxicosis was found, and only the kidneys of sheep receiving the higher dosage showed a significant accumulation of zinc compared with the controls. 相似文献