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   29篇
  免费   11篇
综合类   8篇
农作物   1篇
畜牧兽医   31篇
  2020年   1篇
  2018年   1篇
  2017年   2篇
  2016年   2篇
  2015年   2篇
  2014年   1篇
  2013年   5篇
  2012年   2篇
  2011年   1篇
  2009年   3篇
  2006年   1篇
  2001年   1篇
  1999年   2篇
  1998年   2篇
  1997年   2篇
  1996年   3篇
  1995年   1篇
  1991年   2篇
  1990年   2篇
  1987年   1篇
  1986年   2篇
  1971年   1篇
排序方式: 共有40条查询结果,搜索用时 31 毫秒
1.
An absorbed enzyme immunoassay (EIA) test for Johne's disease in cattle was developed in which absorption of cross-reacting antibodies occurred as a rapid reaction in solution rather than overnight with whole organisms and a subsequent centrifugation step. Total test time was reduced to less than 2 h with a minimum of manipulations. The test was evaluated in cattle herds from Johne's disease-endemic and Johne's disease-free regions of Australia. Specificity was 99.8%. Calculations of sensitivity were affected by the history of the herd under test. However, the EIA detected in excess of 80% of animals before onset of clinical disease and 65% of faecal shedders were EIA positive on, or before, first detection of Mycobacterium paratuberculosis in their faeces. The test should aid epidemiological studies and be a useful tool in the management and control of Johne's disease.  相似文献   
2.
Malignant hyperthermia (MH) is a hypermetabolic and hypercontractile syndrome triggered by anesthesia or various stressors that cause a sustained increase in sarcoplasmic ionized Ca. Susceptibility is apparently inherited in an autosomal dominant pattern. The primary molecular defect results in hypersensitive ligand-gating of the Ca-release channel of sarcoplasmic reticulum (SR) in skeletal muscle: channel opening is stimulated by abnormally low concentrations of agonist. We attribute MH to a mutation in the gene for the fast twitch muscle isoform of the Ca-channel, resulting in the expression of a cardiac-like isoform in fast muscle. Syndromes with some resemblance to MH can occur due to other genetic or acquired imbalances in Ca-flux across SR that favor net release of Ca. Either defective uptake or release can be detected as increased sensitivity of muscle to the contracture-producing effects of caffeine and halothane. Thus, caffeine and/or halothane contracture tests for MH-susceptibility may give false positives when there is decreased Ca-uptake, such as in muscular dystrophies. Ca-channel hypersensitivity and decreased Ca-uptake activity can be detected by assays using isolated SR. Functional assays using lymphocytes are being assessed as potential replacements for muscle contracture tests. Polymorphism analysis of proteins or nucleic acids for the MH or closely-linked genes has been used to trace the inheritance of MH-susceptibility.  相似文献   
3.
Measurements of electrical conductivity at high pressure and temperature were taken on the lower mantle phase magnesiowustite with varying Fe3+ content. Although previous measurements at atmospheric pressure suggest Fe2+-Fe3+ hopping (small polaron) as the dominant conductivity mechanism, the present experiments show a change in charge transport mechanism with temperature. The lower temperature measurements are consistent with small polaron conduction, but at higher temperatures, which are more applicable to the lower mantle, a large polaron mechanism is suggested. Because these mechanisms have different temperature and compositional dependencies, this transition has important implications for extrapolation to mantle conditions.  相似文献   
4.
Pulsed laser deposition (PLD) is a conceptually and experimentally simple yet highly versatile tool for thin-film and multilayer research. Its advantages for the film growth of oxides and other chemically complex materials include stoichiometric transfer, growth from an energetic beam, reactive deposition, and inherent simplicity for the growth of multilayered structures. With the use of PLD, artificially layered materials and metastable phases have been created and their properties varied by control of the layer thicknesses. In situ monitoring techniques have provided information about the role of energetic species in the formation of ultrahard phases and in the doping of semiconductors. Cluster-assembled nanocrystalline and composite films offer opportunities to control and produce new combinations of properties with PLD.  相似文献   
5.
6.
AIMS: To assess the sensitivity and specificity of a bulk tank milk (BTM) antibody enzyme-linked immunosorbent assay (ELISA) to detect likely infection of a dairy herd with bovine vi- ral diarrhoea virus (BVDV). The ELISA was subsequently used to estimate the prevalence of likely infected herds in parts of the North Island of New Zealand.

METHODS: BTM samples from 724 randomly selected dairy herds in the Waikato, Bay of Plenty and Northland regions of New Zealand were tested for BVDV antibodies. From this group, 20 herds were again randomly selected from each of the quartiles of the ELISA percentage inhibition (%INH) result. From each participant herd, serum from 15 randomly selected calves aged 6–18 months and 15 cows was collected and tested using an indirect blocking ELISA for BVDV antibodies.

RESULTS: Among serum results from calves from 50 herds available for analysis, 34 (68%) herds were classified as likely non-infected (0-3 seropositive among 15 calves) and 16 (32%) as likely infected (5–15 seropositive among 15 calves). Receiver- operator characteristic (ROC) analysis identified an optimal cut-off for BTM of 80%INH associated with 81% sensitivity and 91% specificity for likely herd infection. The prevalence of BVDV antibodies in cows within herds and %INH for BVDV in bulk milk were positively correlated (p<0.01). The association between bulk milk %INH and the prevalence of BVDV antibodies in calves was stronger than the same association in cows. Based on the threshold of 80%INH, the 95% confidence interval (CI) for prevalence of likely infection in the 724 herds in the Waikato, Bay of Plenty and Northland regions of New Zealand was 12–17%. Vaccination against BVDV was not significantly associated with the likely infection status of the herd based on prevalence of BVDV antibodies among calves.

CONCLUSION: An ELISA test result for BVDV antibodies in BTM ≥80%INH can be used as a threshold to indicate the presence of likely infection with BVDV in dairy herds in New Zealand, with 81% sensitivity and 91% specificity.  相似文献   
7.
Because of the importance of reproduction in stock breeding systems, it is necessary to find selection criteria that increase reproductive efficiency. The aim of this study was to estimate genetic parameters for the probability of conception on first service (PROB) in Murrah heifers, and its association with other traits of economic interest [age at first calving (AFC), service period, calving interval and milk yield at 270 days], with the purpose of evaluating their use as selection criteria. Reproductive information and first lactation records of 1200 Murrah heifers were used to perform two‐trait analyses between PROB and the other characteristics. Bayesian inference was used to estimate the variance components, considering PROB as threshold and the other as linear factors. The results demonstrate that this trait has heritability of 0.15, indicating the possibility of a genetic gain by using it for selection. With respect to the genetic correlation estimates, the only high‐magnitude association was with AFC (?0.899), which is the current criterion indicating sexual precocity of females. In the light of the parameters estimated, the first‐service pregnancy rate is an alternative for indication of sexual precocity, although presenting a smaller genetic gain than the current standard AFC. Nevertheless, additional research should be conducted regarding this trait to assess the economic importance of its use in dairy buffalo production systems.  相似文献   
8.

Background  

The Resource Dispersion Hypothesis (RDH) proposes a mechanism for the passive formation of social groups where resources are dispersed, even in the absence of any benefits of group living per se. Despite supportive modelling, it lacks empirical testing. The RDH predicts that, rather than Territory Size (TS) increasing monotonically with Group Size (GS) to account for increasing metabolic needs, TS is constrained by the dispersion of resource patches, whereas GS is independently limited by their richness. We conducted multiple-year tests of these predictions using data from the long-term study of badgers Meles meles in Wytham Woods, England. The study has long failed to identify direct benefits from group living and, consequently, alternative explanations for their large group sizes have been sought.  相似文献   
9.
This study tested the hypothesis that calcium-release from sarcoplasmic reticulum isolated from malignant hyperthermia swine had abnormal concentration-dependency on release modulators. Halothane stimulated half-maximal calcium-release at similar concentrations for malignant hyperthermia and control sarcoplasmic reticulum (0.10 +/- 0.04 mM). However, concentrations causing half-maximal calcium-release were lower for malignant hyperthermia sarcoplasmic reticulum (P less than 0.001) by an order of magnitude for Ca2+ (28.1 +/- 8.3 versus 1.23 +/- 0.45 nM), adenosine triphosphate (0.33 +/- 0.09 versus 0.023 +/- 0.014 mM) and caffeine (7.79 +/- 1.56 versus 0.80 +/- 0.44 mM). Half-maximal inhibition by Mg2+ occurred at threefold higher concentrations for malignant hyperthermia sarcoplasmic reticulum (0.23 +/- 0.02 versus 0.78 +/- 0.17 mM). The Ca2+-sensitivity curves for calcium-release by sarcoplasmic reticulum isolated from heterozygotes for the malignant hyperthermia-defect were indistinguishable from the averages of the curves for controls and malignant hyperthermia-homozygotes. Results of this study suggest that malignant hyperthermia is initiated due to a hypersensitive calcium-release mechanism which is inherited in an autosomal, codominant pattern and may be diagnosed using calcium-release sensitivity-tests on isolated sarcoplasmic reticulum.  相似文献   
10.

Objective

To evaluate the feasibility and effectiveness of mesotherapy in dogs compared with a positive control group.

Study design

Experimental, randomized, blinded study.

Animals

Fifteen working police dogs with chronic back pain.

Methods

Animals were divided randomly into control (CG; n = 5) and treatment groups (TG; n = 10). A combination of 140 mg lidocaine, 15 mg dexamethasone and 20 mg thiocolchicoside was administered to group TG along with a 70-day course of a placebo, administered as if it was carprofen. Carprofen was administered to Group CG for 70 days, at a dose adjusted to their weight. On day 0, an intradermal injection of Ringer’s lactate was also administered. Both groups were rested for 3 days and resumed normal activity over a 5-day period. Response to treatment, measured by the Canine Brief Pain Inventory (CBPI) and the Hudson Visual Analogue Scale (HVAS), was evaluated before treatment (T0), after 15 days (T1) and 1 (T2), 2 (T3), 3 (T4), 4 (T5) and 5 (T6) months. Results were compared using a Mann–Whitney test or a paired samples t test.

Results

When comparing CBPI results, no differences were found between groups TG and CG at T0 through T3 and in T6 and T7. Differences were observed in CBPI sections after the discontinuation of carprofen: at T4 [p = 0.02 for Pain Interference Score (PIS) and p = 0.03 for Pain Severity Score (PSS)] and T5 (p = 0.16 for PIS and p = 0.03 for PSS), with group TG having overall better results. Individual treatment results were considered successful in one dog of group CG (20%), whereas in group TG, success was higher (ranging from 78% at T1 to 22% at T7). No significant differences were registered with the HVAS.

Conclusions and clinical relevance

Mesotherapy may be a promising treatment option for canine musculoskeletal-related pain. Further studies are required.  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