全文获取类型
收费全文 | 274篇 |
免费 | 13篇 |
专业分类
林业 | 23篇 |
农学 | 2篇 |
10篇 | |
综合类 | 50篇 |
农作物 | 5篇 |
水产渔业 | 5篇 |
畜牧兽医 | 182篇 |
园艺 | 5篇 |
植物保护 | 5篇 |
出版年
2023年 | 3篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 12篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 22篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 16篇 |
1997年 | 16篇 |
1996年 | 15篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1967年 | 1篇 |
1959年 | 2篇 |
1958年 | 3篇 |
1956年 | 2篇 |
排序方式: 共有287条查询结果,搜索用时 31 毫秒
61.
The adoption of precision farming (PF) was studied on the basis of personal interviews conducted at several agricultural exhibitions
in Germany. Between 6.65% and 11% of the interviewed farmers used PF. The majority used data collection techniques such as
GPS-based area measurement and soil sampling rather than variable rate application techniques such as site-specific sowing
and fertilising. Roughly half the farmers interviewed knew about PF. About 7–10% of them intended to start using PF in the
future. The results indicated that a large number of farmers did not even know what PF meant. In order to get more insight
into this situation, several interviews were conducted with farmers already using PF techniques. A further study in 2005 of
PF education in Germany indicated that, especially at vocational and technical schools, the subject was only covered to a
small extent although the aim was to give a better coverage in future. At higher education levels, such as at universities
and technical colleges, the teaching of PF was clearly better established. In order to promote awareness of PF among farmers,
information and teaching materials adapted to the relevant educational levels were developed and tried out at training events.
The main topics addressed were parallel tracking systems, site-specific nitrogen fertilising, yield mapping in grain production
and the use of PDAs in crop farming. Finally, preliminary survey results are presented showing how knowledge about PF can
best lead to its adoption and transfer into daily practice. 相似文献
62.
E. Müller G. Moser H. Bartenschilager H. Geldermann 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2000,117(3):189-202
The genetic diversity between European Wild Boar, Pietrain and Meishan and their crossbred generations are described on the basis of performance traits for growth, carcass composition and meat quality. Using the results of 1333 pigs, the highest growth rates were found in crossbred generations, indicating positive heterosis effects. In carcass composition, high meat content is associated with Pietrain and high fat content with Meishan alleles. Weights of organs were greatest in Wild Boar, the weight of the head was greatest in Meishan. Meat quality and stress resistance parameters point to superior gene effects in Wild Boar and Meishan. Crossbred animals of these genetically diverse pig sources generate the maximum variability for all traits, help to demonstrate the range of values for the specified breeds of pig and allow an efficient analysis of the genes influencing performance traits. 相似文献
63.
The farrowing rates resulting from matings on different days of the week were determined for a 2800-sow intensive piggery in both 1983 and 1984. The results showed that sows mated early in the week achieved a significantly higher farrowing rate than sows mated late in the week (P less than 0.0001). During the seasonal (summer to autumn) infertility period, Wednesday matings resulted in a poor farrowing rate whereas for the rest of the year farrowing rates following Wednesday matings were similar to those for Sunday Monday and Tuesday matings. Consistent results were obtained for data from both years. It is proposed that the stress of regrouping unmated sows on Wednesday to accommodate newly weaned sows is responsible for this decrease in fertility. This study illustrates how detailed analysis of farrowing rates on a day of mating basis can identify a problem which is otherwise masked by weekly data. 相似文献
64.
The comparative pathogenicity of four serovars of Actinobacillus (Haemophilus) pleuropneumoniae 总被引:1,自引:0,他引:1
The pathogenicity of 2 isolates of each of serovars 7, 3, 1 and 2 of Actinobacillus pleuropneumoniae was tested by intranasal inoculation into 60, 6-week-old large white pigs. Four dose rates varying from 0.27 to 560 x 10(6) organisms per pig with 10-fold serial dilutions were used. Surviving pigs were necropsied 7 days after inoculation. The proportion of pigs dying and developing gross lesions following infection was significantly greater for pigs given serotype 1 than for each of the other 3 serotypes, which did not differ significantly from each other. Twelve of 16 pigs given either of the 2 isolates of serovar 1 died after acute illness and 1 of 44 pigs given either of the 2 isolates each of serovars 7, 3 and 2 died. Pigs given serovar 1 showed high temperatures, severe respiratory distress, frothy haemorrhagic nasal discharge and weight loss. Lung lesions were produced in all 16 pigs given serovar 1, in 7 of 14 pigs given serovar 7, 7 of 14 pigs receiving serovar 3 and in 5 of 16 pigs given serovar 2. The lethal infections were characterised by a severe acute fibrinohaemorrhagic necrotising pleuropneumonia, whereas non-lethal cases had lung lesions ranging from necrotising purulent pleuropneumonia to abscessation. Significant differences between isolates in proportions of tissues culture positive for A. pleuropneumoniae for serovars 7 and 2, but not for serovars 3 and 1 suggested that isolates may vary in virulence within serovars, but more detailed studies are needed to clarify this point. 相似文献
65.
66.
The acute toxicity for sheep of 3 alkaloids that occur in Phalaris acquatica was examined by intravenous and oral administration. The lowest tested dose rates that produced clinically observed signs were, for 5-methoxy dimethyltryptamine, 0.1 mg/kg body weight intravenously and 40 mg/kg orally; for gramine, 10 mg/kg intravenously and 500 mg/kg orally; and for hordenine, 20 mg/kg intravenously and 800 mg/kg orally. All induced the clinical signs observed in the nervous form of phalaris toxicity, but none induced the cardiac, sudden death, syndrome. 相似文献
67.
68.
69.
Effect of age, weaning and diet on digestive enzyme levels in the piglet 总被引:27,自引:0,他引:27
M D Lindemann S G Cornelius S M el Kandelgy R L Moser J E Pettigrew 《Journal of animal science》1986,62(5):1298-1307
Thirty-seven pigs were used to evaluate the effects of age and weaning on the level of protease in the gastric mucosa and trypsin, chymotrypsin, amylase and lipase in the pancreas. There was a positive allometry of the pancreas and gastric mucosa associated with age and with weaning to a solid diet. Increases with age in total activity of chymotrypsin, trypsin, amylase and gastric proteases were due to increases in both tissue weight and enzyme activity per gram of tissue. A general depression in pancreatic enzymatic activities, but not in gastric proteolytic activity, was found during the first week following weaning. Forty pigs were used in a second trial to evaluate the effects of age and weaning diet on the same digestive enzymes. Total activity of all enzymes assayed increased with time postweaning. Increases in total activity of lipase and chymotrypsin were due primarily to increased pancreatic weight postweaning. Amylase, trypsin and gastric protease increases were due both to increased tissue weight and increased activity per gram of tissue. There were no effects of diet on the weight of gastric mucosa or the level of activity of the gastric proteases. Pigs fed a diet containing 20% whey had larger pancreases (P less than .10) at slaughter and a greater, but nonsignificant, mean activity per gram of pancreas for all pancreatic enzymes. It appears that the pig has sufficient pancreatic and gastric enzyme activity so that performance should not be limited, with the possible exception of the period shortly after weaning. However diet digestibility and subsequent pig performance may be more directly related to the extent of release of these enzymes into the intestine and the conditions that exist therein. 相似文献
70.