全文获取类型
收费全文 | 1331篇 |
免费 | 75篇 |
国内免费 | 1篇 |
专业分类
林业 | 64篇 |
农学 | 25篇 |
基础科学 | 16篇 |
215篇 | |
综合类 | 174篇 |
农作物 | 41篇 |
水产渔业 | 50篇 |
畜牧兽医 | 703篇 |
园艺 | 23篇 |
植物保护 | 96篇 |
出版年
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 26篇 |
2018年 | 21篇 |
2017年 | 22篇 |
2016年 | 27篇 |
2015年 | 24篇 |
2014年 | 31篇 |
2013年 | 44篇 |
2012年 | 55篇 |
2011年 | 76篇 |
2010年 | 43篇 |
2009年 | 33篇 |
2008年 | 59篇 |
2007年 | 59篇 |
2006年 | 53篇 |
2005年 | 46篇 |
2004年 | 37篇 |
2003年 | 47篇 |
2002年 | 37篇 |
2001年 | 39篇 |
2000年 | 26篇 |
1999年 | 28篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1992年 | 17篇 |
1991年 | 31篇 |
1990年 | 23篇 |
1989年 | 13篇 |
1988年 | 20篇 |
1987年 | 23篇 |
1986年 | 14篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 17篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 18篇 |
1974年 | 10篇 |
1973年 | 25篇 |
1972年 | 19篇 |
1971年 | 12篇 |
1970年 | 9篇 |
1969年 | 10篇 |
1967年 | 11篇 |
1966年 | 15篇 |
排序方式: 共有1407条查询结果,搜索用时 15 毫秒
1.
The study describes plumage modifications and specific feather malformations, as related to the domestication process of different poultry species. The modifications include naked necks, leg feathering, frizzle feathering, silky feathering, fat quills, and feather abnormalities caused by behavioural hypertrophies. Most of these plumage modifications correspond to the breed standard for exhibition poultry fancy. However, they impair the normal function of these animals. The negative influences comprise disorders in social behaviour, loss of typical plumage functions and disabilities of normal mobility, as well as genetic defects and pathogenic predispositions. 相似文献
2.
Red foxes ( Vulpes vulpes ) are a major pest species in Europe and Australia. Traditional methods of control such as hunting or poisoning are no longer sufficient or feasible. As with domestic dogs and cats, prolactin (PRL) in the vixen is an essential luteotropin during the second half of gestation. Hence, PRL inhibitors such as cabergoline have been used to induce abortions. Eighteen mated silver fox vixens (three groups of six foxes each) were treated orally with a placebo of paraffin oil (I), or with 15 μ g/kg cabergoline in feed once (II) or twice (III), on day 30 (I and II) or days 30 and 32 (III) post-coitum. Blood samples were taken prior to and after treatments and concentrations of PRL and progesterone (P4 ) were determined. Normal parturitions were observed in five of six, five of six and two of six vixens in groups I, II and III, respectively. In group III plasma concentrations of PRL and P4 decreased significantly but only temporarily. This drop in hormone concentrations was more pronounced in the vixens that did not carry to term. In conclusion, doses in excess of 15 μ g/kg of cabergoline are likely to prevent the development of fetuses to term in pregnant vixens. 相似文献
3.
Expression of β2-integrin on monocytes and blood polymorphonuclear leukocytes in the periparturient period in dairy cows 下载免费PDF全文
Araceli Diez-Fraile Luc Duchateau Evelyne Meyer Christian Burvenich 《Canadian journal of veterinary research》2003,67(3):235-238
The hypothesis that an altered expression of CD11/CD18 on bovine circulating monocytes, polymorphonuclear leukocytes (PMN), or both, contributes to an increased mastitis susceptibility in periparturient cows was tested. Expression of CD18 and CD11a, -b, -c on bovine monocytes and PMN were assessed in 8 Friesian-Holstein cows by flow cytometry from 2 wk before calving to 5 wk after calving. Minor changes in adhesion molecule expression levels were detected throughout the experimental period. Compared with PMN, monocytes exhibited an expression level that was similar for CD18, higher for CD11a and CD11c, but lower for CD11b. Differences in density may reflect the relative importance of these adhesion molecules on both leukocyte types. In this study, the decreased number of milk resident macrophages and PMN observed during the periparturient period could not be attributed to changes of CD11/CD18 levels on circulating leukocytes. 相似文献
4.
5.
Piero Roggero Hervé Lot Sylvie Souche Riccardo Lenzi Robert G. Milne 《European journal of plant pathology / European Foundation for Plant Pathology》2003,109(3):261-267
Big-vein disease (BV) of lettuce has been attributed to infection by Lettuce big-vein virus (LBVV), vectored by the soil fungus Olpidium brassicae. The finding of a second soil-borne virus in lettuce, Mirafiori lettuce virus (MiLV), led to a re-investigation of the role of LBVV in big-vein disease, with evidence emerging that both MiLV and LBVV are vectored by O. brassicae, and that MiLV, not LBVV, is the cause of BV (Lot et al. (2002), Phytopathology 92: 288–293). The two viruses have coat proteins of similar size but have different morphologies and are serologically unrelated. We tested individual lettuce plants in BV-prone fields and protected crops in France and Italy for the presence of the two viruses, using DAS-ELISA and antisera specific for each virus. Both MiLV and LBVV were found at high incidence, often together but sometimes separately. Symptoms were frequently found to be associated with MiLV alone or both viruses, but rarely LBVV alone. However, no absolute correlation emerged, because sometimes MiLV was present in the absence of symptoms, and vice versa. To clarify the situation, individual lettuce plants were examined over a period of time in two further surveys. In surveys of protected crops in France, plants with big-vein were always ELISA-positive for MiLV, or else symptomless plants positive for MiLV were later seen to develop big-vein symptoms. Presence or absence of LBVV appeared to have no effect on symptom development. In surveys of open fields in Italy, all combinations were found: presence of both viruses, apparent absence of both viruses, or presence of each one alone, in plants that developed BV. At the end of the observation period, nearly all plants had BV and contained both viruses. 相似文献
6.
7.
8.
Long‐term follow‐up of renal function assessing serum cystatin C in dogs with diabetes mellitus or hyperadrenocorticism 下载免费PDF全文
9.
10.
Ohlschläger S Spolders M Meyer U Flachowsky G 《Berliner und Münchener tier?rztliche Wochenschrift》2007,120(5-6):226-231
At the Institute of Animal Nutrition of the Federal Agricultural Research Centre (FAL) in Braunschweig a feeding trial with 30 first lactating cows (German Holstein) was realised in 2004 for a complete lactation. All animals received a diet based on maize- and grass-silage ad libitum at the rate of 60:40 (DM-base) and concentrate depending on their milk yield.The animals were fed with energy and protein as recommended (GfE 2001) and were kept in loose housing. After calving they were split randomly into two feeding groups with 15 animals each. Group 1 was fed a concentrate according to the recommendations of the GfE (2001), whereas group 2 was offered the same concentrate with roughly the double amount of calcium, magnesium, phosphorus, copper, zinc, beta-carotene and vitamins A and E. To study the influence of the different concentrates on the serum concentrations of minerals and vitamins, blood, feed and milk samples were regularly taken and analysed in the course of lactation. Significantly higher blood concentrations were detected for phosphorus, zinc and vitamin E in group 2, but therefore a direct influence of the feeding on the blood concentrations was detected only for zinc and vitamin E. Over the whole lactation the average milk yield of group 1 was 2.6 kg/day higher and the average milk fat content was reduced about 0.6 percent points compared to group 2. 相似文献