首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   108篇
  免费   28篇
  国内免费   1篇
林业   3篇
农学   1篇
  2篇
综合类   14篇
农作物   1篇
畜牧兽医   112篇
植物保护   4篇
  2023年   5篇
  2021年   1篇
  2020年   7篇
  2019年   3篇
  2018年   7篇
  2017年   6篇
  2016年   13篇
  2015年   8篇
  2014年   4篇
  2013年   8篇
  2012年   4篇
  2011年   3篇
  2010年   3篇
  2009年   8篇
  2007年   6篇
  2006年   5篇
  2005年   2篇
  2004年   2篇
  2003年   3篇
  2002年   5篇
  2001年   1篇
  2000年   3篇
  1999年   3篇
  1998年   7篇
  1997年   3篇
  1996年   4篇
  1995年   3篇
  1993年   1篇
  1991年   1篇
  1989年   2篇
  1988年   1篇
  1985年   1篇
  1981年   1篇
  1979年   3篇
排序方式: 共有137条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
Captive breeding of birds threatened by extinction in zoological gardens or other closed aviary centres is one of the methods allowing their protection and gene pool preservation ex situ in vivo. Such birds are usually kept in captivity lifelong and serve as parents of several new generations that can be further released into natural environment, or males are used as semen donors for artificial insemination and gene banking. Therefore, the fecundity of such flocks (number of laid egg and spermatozoa quantity and quality) is very important. The aim of this study was to evaluate the usefulness of captive kept capercaillie (Tetrao urogallus L.) as semen donors in three subsequent reproductive seasons, based on the assessment of manually collected semen quality. Male response to dorso‐abdominal massage, ejaculate volume, sperm concentration, motility and morphology were evaluated individually at three succeeding years. Depending on individual male properties and year of collection, the number of positive reactions to semen collection attempts (i.e. ending with ejaculation) varied from 44.4% to 100.0%; single ejaculate volume ranged from 10 to 300 μl, spermatozoa concentration from 10 × 106 per ml to 3520 × 106 per ml and percentage of live morphologically normal spermatozoa from 19.3 to 80.3%. The highest average value (66.7) of semen quality factor (SQF) was noted for a 2‐year‐old male (varying from 1.9 to 258.1), while the lowest for ten‐ (4.8; varying from 0.1 to 17.0) and 7‐year‐old (6.6; varying between 0.6 and 13.6). Assuming that for AI purposes, the ejaculate quality has to be at minimum 10 SQF, obtained results indicate that majority of capercaillie kept in captivity, both young (2–3 years old) and older (up to 10 years old), can be valuable semen producers in succeeding seasons.  相似文献   
105.

Background

The involvement of placental lactogen (PL) in the regulation of foetal growth has been investigated in different species by in vivo immunomodulation techniques. However, when circulating antibodies are present together with the hormone, the procedure for hormonal measurement becomes considerably complex. The aim of this study was the immunoneutralization of bovine placental lactogen (bPL) concentrations in bovine foetal circulation by direct infusion of rabbit anti-bPL purified immunoglobulins (IgG) via a foetal catheter (in vivo study). The ability of a RIA based on guinea pig anti-bPL antiserum, for the measurement of bPL concentrations in samples containing exogenous rabbit anti-bPL immunoglobulins, was also analyzed in in vitro and in vivo conditions.

Methods

Six bovine foetuses were chronic cannulated on the aorta via the medial tarsal artery. Infusion of rabbit anti-bPL IgG was performed during late gestation. Pooled rabbit anti-bPL antisera had a maximal neutralization capacity of 25 μg bPL/mL of immunoglobulin. Interference of rabbit anti-bPL immunoglobulin with radioimmunoassay measurement using guinea pig anti-bPL as primary antibody was first evaluated in vitro. Polyclonal anti-bPL antibodies raised in rabbit were added in foetal sera to produce 100 samples with known antibodies titers (dilutions ranging from 1:2,500 till 1:1,280,000).

Result(s)

Assessment of the interference of rabbit anti-bPL antibody showed that bPL concentrations were significantly lower (P < 0.05) in samples added with dilutions of rabbit antiserum lower than 1:80,000 (one foetus) or 1:10,000 (four foetuses). It was also shown that the recovery of added bPL (12 ng/mL) was markedly reduced in those samples in which exogenous rabbit anti-bPL were added at dilutions lower than 1:20,000. Concentrations of foetal bPL were determined in samples from cannulated foetuses. In foetuses 1 and 6, bPL concentrations remained almost unchanged (<5 ng/mL) during the whole experimental period. In Foetus 3, bPL concentrations decreased immediately after IgG infusion and thereafter, they increased until parturition.

Conclusion(s)

The use of a bPL RIA using a guinea pig anti-bPL as primary antiserum allowed for the measurement of bPL concentrations in foetal plasma in presence of rabbit anti-bPL IgG into the foetal circulation. Long-term foetal catheterization allowed for the study of the influence of direct infusion of anti-bPL IgG on peripheral bPL concentrations in bovine foetuses.  相似文献   
106.
The application of remote sensing technology and precision agriculture in the oil palm industry is in development. This study investigated the potential of high resolution QuickBird satellite imagery, which has a synoptic overview, for detecting oil palms infected by basal stem rot disease and for mapping the disease. Basal stem rot disease poses a major threat to the oil palm industry, especially in Indonesia. It is caused by Ganoderma boninense and the symptoms can be seen on the leaf and basal stem. At present there is no effective control for this disease and early detection of the infection is essential. A detailed, accurate and rapid method of monitoring the disease is needed urgently. This study used QuickBird imagery to detect the disease and its spatial pattern. Initially, oil palm and non oil palm object segmentation based on the red band was used to map the spatial pattern of the disease. Secondly, six vegetation indices derived from visible and near infrared bands (NIR) were used for to identify palms infected by the disease. Finally, ground truth from field sampling in four fields with different ages of plant and degrees of infection was used to assess the accuracy of the remote sensing approach. The results show that image segmentation effectively delineated areas infected by the disease with a mapping accuracy of 84%. The resulting maps showed two patterns of the disease; a sporadic pattern in fields with older palms and a dendritic pattern in younger palms with medium to low infection. Ground truth data showed that oil palms infected by basal stem rot had a higher reflectance in the visible bands and a lower reflectance in the near infrared band. Different vegetation indices performed differently in each field. The atmospheric resistant vegetation index and green blue normalized difference vegetation index identified the disease with an accuracy of 67% in a field with 21 year old palms and high infection rates. In the field of 10 year old palms with medium rates of infection, the simple ratio (NIR/red) was effective with an accuracy of 62% for identifying the disease. The green blue normalized difference vegetation index was effective in the field of 10 years old palms with low infection rates with an accuracy of 59%. In the field of 15 and 18 years old palms with low infection rates, all the indices showed low levels of accuracy for identifying the disease. This study suggests that high resolution QuickBird imagery offers a quick, detailed and accurate way of estimating the location and extent of basal stem rot disease infections in oil palm plantations.  相似文献   
107.

Background

Demodex gatoi is unique among demodectic mites. It possesses a distinct stubby appearance, and, instead of residing in the hair follicles, it dwells in the keratin layer of the epidermis, causing a pruritic and contagious skin disease in cats. Little is known of the occurrence of D. gatoi in Europe or control of D. gatoi infestation.

Case presentation

We describe D. gatoi in 10 cats, including five Cornish Rex, two Burmese, one Exotic, one Persian and one Siamese, living in six multi-cat households in different locations in Finland containing 21 cats in total. Intense pruritus was the main clinical sign. Scaling, broken hairs, alopecia and self-inflicted excoriations were also observed.Diagnosis was based on finding typical short-bodied demodectic mites in skin scrapings, skin biopsies or on tape strips. Other pruritic skin diseases, such as allergies and dermatophytoses, were ruled out. In one household, despite finding several mites on one cat, all six cats of the household remained symptomless.Amitraz used weekly at a concentration of 125-250 ppm for 2-3 months, proved successful in three households, 2% lime sulphur weekly dips applied for six weeks in one household and peroral ivermectin (1 mg every other day for 10 weeks) in one household. Previous trials in four households with imidacloprid-moxidectin, selamectin or injected ivermectin given once or twice a month appeared ineffective.

Conclusion

D. gatoi-associated dermatitis is an emerging contagious skin disease in cats in Finland. Although pruritus is common, some cats may harbour the mites without clinical signs. In addition, due to translucency of the mites and fastidious feline grooming habits, the diagnosis may be challenging. An effective and convenient way to treat D. gatoi infestations has yet to emerge.  相似文献   
108.
109.
110.
The major impacts of bovine viral diarrhoea (BVD) on cattle health and production have prompted many countries to embark on national elimination programmes. These programmes typically involve identifying and removing persistently infected (PI) cattle in infected herds and implementing biosecurity measures, such as pre- or post-movement testing. In order to design a systematic national control programme to eliminate BVD in New Zealand, which achieves the greatest benefits to the industries at the lowest cost to individual farmers, an accurate understanding is necessary of the epidemiology, economics and social motivation for BVD control in New Zealand. In this article we briefly review the pathogenesis of BVD, transmission and diagnosis of BVD virus infection, and effectiveness of vaccination. We summarise the current state of knowledge of the prevalence, risk factors for transmission, and financial impacts of BVD in New Zealand. We describe control programmes in Europe and then discuss the challenges that must be addressed to design a cost-effective national control programme to eliminate BVD in New Zealand.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号