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   186篇
  免费   21篇
林业   12篇
农学   10篇
  27篇
综合类   2篇
农作物   10篇
水产渔业   23篇
畜牧兽医   99篇
园艺   3篇
植物保护   21篇
  2024年   1篇
  2023年   6篇
  2022年   1篇
  2021年   12篇
  2020年   13篇
  2019年   10篇
  2018年   10篇
  2017年   10篇
  2016年   14篇
  2015年   7篇
  2014年   12篇
  2013年   20篇
  2012年   17篇
  2011年   25篇
  2010年   8篇
  2009年   7篇
  2008年   6篇
  2007年   7篇
  2006年   2篇
  2005年   4篇
  2004年   5篇
  2003年   1篇
  2002年   2篇
  2001年   1篇
  1995年   1篇
  1993年   1篇
  1992年   2篇
  1991年   1篇
  1988年   1篇
排序方式: 共有207条查询结果,搜索用时 31 毫秒
1.
The aim of this study was to identify possible effects of different vaccination strategies (concomitantly or not) against brucellosis and clostridia on intake, performance, feeding behavior, blood parameters, and immune responses of dairy heifers calves. Fifty heifers calves were enrolled [38 Gyr (Zebu, Bos taurus indicus) and 12 5/8 Holstein Gyr]. At 120 d of age, animals were randomly distributed among 3 groups: B (n = 18), vaccinated against brucellosis; C (n = 14), vaccinated against clostridia and CB (n = 18), vaccinated concomitantly for both. Rectal and thermographic temperatures were evaluated on days 1, 0, 1, 2, 3, 5, 7,10, 14, and 28 relatives to the vaccination day. Feed and water intake, body weight (BW), and feeding behavior were monitored daily by an electronic feeding system. Blood was sampled on days 0, 3, 7, 14, and 28, relative to the vaccination day for determination of glucose and -hydroxybutyrate (BHBA) concentrations. Blood sampled on day 0 (prevaccination) and on days 28 and 42 were used to evaluate the immune response against Brucella abortus and clostridia. There was an increase in rectal temperature between the first and the third day postvaccination in the 3 groups. The thermography revealed an increase of local temperature for 7 d on groups B and CB. Group C had increased local temperature for a longer period, lasting for up to 14 d. Dry mater intake was reduced for groups B and CB, but no alteration was observed for group C. No alterations regarding initial BW, final BW, average daily weight gain, and feed efficiency were observed. No differences were observed for the 3 vaccination groups for blood parameters throughout the evaluation period. The concomitant vaccination against brucellosis and clostridia led to lower neutralizing antibody titers against epsilon toxin of Clostridium perfringens and botulinum toxin type C of C. botulinum (C > CB > B). When cellular proliferation assay and serological tests to B. abortus were evaluated, no differences were observed between groups B and CB. The present results indicate that the concomitant vaccination against brucellosis and clostridia has no relevant impact on the intake, performance, and feeding behavior of dairy calves. However, the concomitant vaccination of vaccines against these 2 pathogens impacts animal immunity against clostridial infections.  相似文献   
2.
Camelids have many unique reproductive features that considerably differ from those of other domestic species. Females are induced ovulators with subsequent development of a corpus luteum (CL) with a short lifespan. Plasma progesterone concentration starts to increase on day 4, peaks on day 8–9 and, in non-pregnant animals, basal concentration is reached around day 10–11 post-induction of ovulation. Luteolytic pulses of prostaglandin F (PGF) are firstly detected on day 7 or 8 (approximately on day 5–6 after ovulation), with maximal luteolytic peaks observed between days 9 and 11 post-mating, in coincidence with a high endometrial expression of cyclooxygenase 2, a limiting enzyme in prostaglandins synthesis. Unlike other species, oxytocin seems not to be involved in the luteolytic process in these species. The CL is the main source of progesterone secretion, and its function is required to support pregnancy. Despite constant research efforts, aspects of reproduction and maternal recognition of pregnancy in camelids remain not fully understood. A transient decrease and subsequent recovery in plasma progesterone concentration are observed after day 9 post-mating in pregnant animals in association with a pulsatile release of PGF and a transitory decrease in CL vascularization. Thus, embryo recognition should occur between days 8 and 12 post-mating. In camels, conceptus tissues exhibit aromatizing activity with the capacity to synthesize large amounts of oestradiol. Similarly, llama blastocysts secrete oestradiol-17β during the preimplantation stage, with a higher production during the elongation period. An increase in the endometrial expression of oestrogen receptor α is also observed on day 12 post-mating. All these evidences suggest that oestrogen could be the signal released by the embryo at the time of its recognition in camelids. Besides, nearly 98% of pregnancies are carried out in the left horn. A decrease in the endometrial expression of mucin 1 and 16 genes has been reported, suggesting that these changes are crucial for successful embryo implantation; however, no differences have been observed between horns. Thus, maternal recognition of pregnancy in camelids is a particularly complex process that must occur in a concise time to allow the rescue of the CL and embryo survival.  相似文献   
3.
4.
The objective of this study was to determine the effect of dietary vitamin E on gilthead seabream (Sparus aurata) growth and survival, at two different highly unsaturated fatty acids (HUFAs) levels. Eighteen days old gilthead seabream larvae were fed four formulated experimental diets combining two different dietary levels of HUFAs (M: medium 2.5 + 1.5, DHA + EPA, H: high 5 + 2.5 DHA + EPA g per 100 g) with two different levels of vitamin E (M: medium 540 mg kg?1, H: high 2900 mg kg?1): MM, MH, HM, HH (HUFA/vitamin E). After 2‐week feeding trial, the average survival rate was 52.6% and there were no significant differences found among treatments. Increase in vitamin E up to high level markedly improved larval growth, particularly when dietary HUFA levels were lower, suggesting a higher protection value when these fatty acids are more limiting. At medium dietary HUFA levels, increase in vitamin E from medium to high level enhanced larval growth performance in terms of total length. Moreover, increase in vit E enhanced HUFAs content in the larval polar lipids denoting the anti‐oxidative effect of vitamin E.  相似文献   
5.
Journal of Soils and Sediments - After the greatest environmental disaster in the history of Brazil and the deposition of the iron ore tailings in alluvial regions, the process of revegetation for...  相似文献   
6.
7.
This study evaluated the effect of short-term baths with the essential oils (EOs) of Lippia sidoides, Ocimum gratissimum and Zingiber officinale on the survival, haematological, biochemical and histopathological parameters of native fish tambaqui (Colossoma macropomum), challenged with Aeromonas hydrophila. After challenge, the fish infected with A. hydrophila received therapeutic baths of 60 min, for five consecutive days. Treatments were as follows: challenged and not treated; challenged and treated with 10 mg L?1 of gentamicin; challenged and treated with EO of L. sidoides (2.5 and 5.0 mg L?1); challenged and treated with EO of O. gratissimum (5.0 and 10.0 mg L?1); challenged and treated with Z. officinale EO (5.0 and 10.0 mg L?1). The highest survival rates were 89.5% (fish treated with 5.0 mg L?1 of O. gratissimum EO) and 75.0% (fish treated with 5.0 mg L?1 of L. sidoides EO). Reductions in the haematocrit percentage, haemoglobin and erythrocyte number were observed in fish treated with L. sidoides and Z. officinale EOs compared with control fish. Mild to moderate damage to the liver tissue of fish after challenge and EO treatments were observed. It is suggested that baths containing O. gratissimum and L. sidoides EOs consist in a viable treatment to increase survival rates of C. macropomum infected with A. hydrophila.  相似文献   
8.
Leptospirosis is a zoonotic disease that occurs in humans and several animal species, including cattle, pigs, and horses, and it has a worldwide distribution. In equids, leptospirosis manifests through recurrent uveitis and abortion and other reproductive disorders. The objective of the present study was to investigate the epidemiological situation of Leptospira spp. infection in equids from the Brejo Paraibano microregion in the northeast of Brazil, that is, to assess the prevalence of and identify the major risk factors for infection. For this purpose, blood samples were taken from 257 equids (204 horses, 46 mules, and 7 donkeys), and a microscopic agglutination test (MAT) was used as serological analysis, with 24 serovars of Leptospira spp. as antigens. Antibodies were observed in 16.2% of horses, 13.0% of mules, and 28.6% of donkeys. Animals between the ages of 2.5 and 11 years had a risk of infection 0.4 times lower than those younger than 2.5 years old (odds ratio, 0.4; 95% confidence interval, 0.18-0.90). Further studies are needed to identify potential wild reservoirs and the main routes of infections.  相似文献   
9.
Summary With the aim to examine its potential as a renewable resource to decontaminate polluted soils, electron microscopy combined with X-ray microanalysis was used to investigate the localization of copper in Cannabis sativa grown in hydroponic copper-rich culture. Cu was found to accumulate preferentially in the upper leaf epidermal cells; it was also detected in spiculae and in abaxial trichomes too. Primary bast fibres seem to be not involved in copper accumulation.  相似文献   
10.
Patterns of phenotypic and phenetic variability in sixPortuguese cultivars of chestnut (Castanea sativa Mill.) are evaluated. Morphological characterisationwas based on the quantification of seventeen traits. Varianceanalysis showed significant differences among cultivars, and cultivar× year for all the traits studied, and trees within cultivarsshowed also some significant differences for some of themorphological variables. A significant correlation was obtainedbetween length of the leaf blade and the percentage of unisexual andandrogynic inflorescence with the effective thermal index,accumulated rainfall from April to October and from July to October,or the accumulated temperature below seven during the dormant period.Principal Component and cluster analysis were performed to group thecultivars, according to their similarity coefficients. For molecularcharacterisation, 125 RAPD and 157 ISSR polymorphic markers wereamplified using 28 and 7 primers respectively. High level ofcongruence among the two marker systems (r =90.5%) was obtained from comparison of pheneticsimilarities based on the percentage of shared fragments. ISSRmarkers revealed important advantages over RAPDs, due to a higheffective multiplex ratio (12.5 for ISSR compared with 2.2 forRAPD analysis) and reproducibility. Although morphological andmolecular results are comparable, slight differences are showed incluster analysis UPGMA dendrograms. Molecular analysis explainedhomonym situations among 'Martainha' and'Longal' cultivars in Portugal.  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