全文获取类型
收费全文 | 431篇 |
免费 | 33篇 |
专业分类
林业 | 6篇 |
农学 | 10篇 |
基础科学 | 3篇 |
20篇 | |
综合类 | 67篇 |
农作物 | 10篇 |
水产渔业 | 6篇 |
畜牧兽医 | 326篇 |
园艺 | 4篇 |
植物保护 | 12篇 |
出版年
2023年 | 4篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 13篇 |
2016年 | 6篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 34篇 |
2012年 | 15篇 |
2011年 | 18篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 16篇 |
2006年 | 26篇 |
2005年 | 9篇 |
2004年 | 20篇 |
2003年 | 8篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 18篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1994年 | 6篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1968年 | 3篇 |
1967年 | 5篇 |
1966年 | 2篇 |
排序方式: 共有464条查询结果,搜索用时 15 毫秒
1.
2.
3.
All horticultural production in Botswana is irrigated, as average rainfall is less than average reference evapotranspiration in all parts of the country for all of the year, and most of the irrigation in the country is used for horticultural crops. In the main, the water used for irrigation comes from groundwater, and much of this can be classified as moderately saline. A survey was carried out of 60 cabbage farmers in five regions of the country to identify the level of salinity of irrigation water and the irrigation practices used. It was concluded that there was no relationship between the irrigation rate (average irrigation depth divided by average irrigation interval) and the salinity of the water used or the salinity of the soil, such that some farmers were over-irrigating and others under-irrigating. This means that water is being wasted and yields are likely to be reduced. In addition, there is a risk of long-term build-up of salinity and soil degradation. 相似文献
4.
Journal of Plant Diseases and Protection - A broad range of different Fusarium (F.) species is associated with Fusarium head blight (FHB) on barley and the corresponding negative effects in... 相似文献
5.
Köhler H Gyra H Zimmer K Dräger KG Burkert B Lemser B Hausleithner D Cubler K Klawonn W Hess RG 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2001,48(3):185-195
After immunization of four calves with a live modified Mycobacterium paratuberculosis vaccine the course of the humoral and cell mediated immune reactions was studied during a 2-year clinical investigation. Furthermore, the possibility of shedding of the vaccine strain and the influence of the vaccination on the tuberculin skin test was determined. In addition to standard procedures recently developed diagnostic methods (antibody enzyme-linked immunosorbent assay, interferon-gamma test, polymerase chain reaction) were used. A cell-mediated immune reaction, reflected in an increased, specifically induced, interferon-gamma production developed much earlier (1-2 weeks post-immunization) than humoral immunity (8-16 weeks post-gamma immunization). While the increase in antibody titres was transient, declining to extremely low levels 48-60 weeks post-immunization, cell-mediated immunity remained detectable until the end of the investigation. Spread of the vaccine strain into the body and shedding were never detected during the whole course of the study except for one colon site in one calf. As late as 2 years after vaccine application positive or doubtful skin reactions against M. bovis purified protein derivative were measured, reflecting possible interference of the immunization with the diagnosis of bovine tuberculosis. At the end of the investigation, a positive cell-mediated immune reaction was detected the control animal although clinical, pathological and bacteriological examinations gave no indication for a mycobacterial infection. 相似文献
6.
In a feeding trial, rabbits allotted in 3 experimental groups were fed rations containing 2.09, 9.83 and 19.5 mg selenium/kg feed in the form of selenium-enriched alfalfa green meal pellets. The selenium enrichment was done by foliar application (spraying) of the 20--25 cm high plant stand with 2.5 kg SeO2 per hectare in watery solution. The control animals were given normal alfalfa green meal pellets of 0.16 ppm selenium content. Toxicity and lethality, tolerance limit and nutritive effect of the pellets were studied. Plant-assimilated selenium was found to be converted more efficiently by the animal organism than was selenium from inorganic compounds (higher retention rate, better gain in body weight and lower feed expenditure). Therefore, the selenium supply to farm animals should be improved by feeding crops that were given selenium dressings. 相似文献
7.
A nine-year-old, intact female dalmatian with diabetes mellitus and a renal abscess is described. The renal abscess was treated surgically by nephrectomy, and the diabetes mellitus resolved with ovariohysterectomy. Abdominal ultrasound and ultrasound-guided aspiration of the abscess were helpful in establishing a diagnosis. To the authors' knowledge, this is the first report of a renal abscess in a dog with diabetes mellitus. 相似文献
8.
The owners of 135 pet birds were surveyed by questionnaire to determine their birds' weekly food consumption. The birds were divided into six food groups on the basis of the amounts of seeds, formulated products and human food they consumed. The formulated products and seeds were analysed for their nutrient content by two independent laboratories, the nutrient content of the human foods was obtained from a standard nutrition reference, and each bird's nutrient intake was estimated. The dietary content of individual nutrients was then compared with the estimated maintenance requirements for pet birds. Birds consuming less than approximately 50 per cent of their diets as formulated products had inadequate intakes of vitamins A and D3, and calcium. Diets high in human food were low in protein, energy, vitamins and minerals. Diets high in seed were excessive in fat and deficient in vitamins A and D3, and calcium. 相似文献
9.
10.
Hess M Prusas C Bergmann V Mazaheri A Raue R 《Berliner und Münchener tier?rztliche Wochenschrift》2000,113(5):202-208
Fowl adenoviruses of the serotype 4 from Germany were characterised by restriction enzyme analysis in comparison to isolates from Asia, South America and the FAV4 reference strain KR5. Only strain Da60 which was isolated from a psittacine aviary was identical with the reference strain KR5. None of the isolates was identical with the highly pathogenic strains from India and Ecuador. One-day-old chicks were infected orally and intramuscularly with the reference strain KR5, the psittacine isolate Da60 and isolate K1013 from Ecuador. Whereas no mortality was seen with the two strains KR5 and Da60, the mortality with K1013 was 100%. The main pathological signs were a swollen liver with necrosis and a lymphocyte depletion with a loss of the follicle structure. To investigate a second subject of avian adenovirus epizootiology several FAVs were characterized serologically and with PCR which was combined with the digestion of the PCR products. Including the reference strains, both methods were compared. It was shown that the digestion of the PCR products allows a clear attribution to a specific serotype, which underlines the usefulness of this method for diagnostic purposes. 相似文献