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Responses to a single or repeated infection with 7000 infective larvae of Haemonchus contortus were studied in an experiment using a total of 106 3-month-old lambs with AA, AB or BB haemoglobin (Hb) genotypes. Results were assessed by faecal egg counts, adult worm counts, haematocrit values, haemoglobin concentrations, total serum protein and serum antibody IgG1 and IgA ELISA titres. None of these parameters showed a strong relationship to the Hb type. The prevalence of low responder (greater than 500 worms) and of high responder (less than 50 worms) animals in groups AA, AB and BB Hb types was 3.8 and 34.6, 20.6 and 35.2, 28.1 and 43.7%, respectively, suggesting that the responsiveness to nematode infection is under the control of gene(s) not closely linked with those determining the Hb genotype. Worm counts of a primary infection are more subject to variation than those of a secondary infection. There is a strong relationship between adult worm counts and faecal egg counts taken close to the time of slaughter. In living animals low and high responder discrimination can be based on individual faecal egg counts around 50 days after a secondary infection. Haematocrit values proved to be of little value in the low and high responder selection. In this regard neither Hb concentration nor total serum protein values are of practical significance. In 3-month-old lambs primary infection induced partial immunity which could prevent the establishment of a part of the secondary infection, irrespective of the presence or absence of the primary worm population. The development of immunity was not associated with an increase of serum IgG1 and IgA antibody levels. Specific antibody production was not influenced by Hb types. Mean antibody levels of low responder lambs showed no difference from those of high responders. Thus, serum IgG1 and IgA levels are of no predictive value in identifying lambs which are genetically resistant to Haemonchus infection.  相似文献   
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ABSTRACT Despite the fact that nonemployment income makes up approximately one-third of all personal income, its impact on local area economies has not been closely examined. This study uses Michigan county data to examine the impact of nonemployment income on nonbasic income over a twenty-seven-year period. This impact is compared to the impact of basic income by employing regression analysis to estimate comparative multiplier effects for both types of income. Nonemployment income is found to have a significant impact on nonbasic income, particularly in metropolitan and nonmetropolitan urban counties, where its impact appears to be stronger than that of basic income.  相似文献   
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The lungs of 71 calves used in two grazing studies were examined for lungworms with a perfusion method combined with a modified Baermann method. The numbers of worms recovered from the lungs were 11,630 in total, 7495 adults, 872 juvenile fifth stage larvae (L5) and 3263 inhibited L5. The percentages found after perfusion were 78.9 per cent in total, 91.8 per cent adults, 78.6 per cent juvenile L5 and 49.6 per cent inhibited L5. The perfusion method seemed adequate and rapid for recovering the adult and juvenile stages but not the inhibited stage. For estimating the numbers of inhibited larvae a combination of perfusion with the Baermann technique is necessary.  相似文献   
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An infection with second-stage larvae of the warble-fly H. diana in a horse is described. The second-stage larvae were incapable of developing into the third stage, because horses are unsuitable hosts and because the infected horse was treated with an insecticide. Since the horse was used for dragging trees in the forests, the infection was likely contracted via contact with H. diana, a normal parasite of roe deer in the Netherlands.  相似文献   
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Performance indicators are variables used to calculate on a continuous basis the operational level of a surveillance network's priority activities. A 10-step process was developed to enable network coordinators to identify specific performance indicators to help them monitor their networks. The methodology was based on a listing of surveillance activities, the definition and choice of network's global priority objectives, the construction of performance indicators and monitoring tables and the implementation of the system within the network. This process was implemented for the bovine clinical digestive salmonellosis surveillance network in France (RESSAB). The process produced a list of 26 activities synthesized into 15 global objectives, from which 12 were retained as priority objectives. This made it possible to develop 12 performance indicators. Indicators retrospectively calculated for the year 2003 indicated that RESSAB was operating according to the objectives set by the network's stakeholders and its financial supporter. The methodology was implemented successfully and was not very time consuming (12 person-days) or expensive. The decision makers and actors in the network quickly appropriated the system. The methodology can thus be considered validated through this example. Nevertheless, the risks inherent in the use of performance indicators must be addressed by ensuring the relevance of the selected indicators through external assessment and by prioritizing an internal and participatory approach to avoid a misuse of the performance indicators. In addition, considering that performance indicators address only the operation of the network, relevance of surveillance procedure should be addressed by external evaluation.  相似文献   
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Contagious caprine pleuropneumonia (CCPP) is a major threat to goat farming in developing countries. Its exact distribution is not well known, despite the fact that new diagnostic tools such as PCR and competitive ELISA are now available. The authors developed a study of the molecular epidemiology of the disease, based on the amplification of a 2400 bp long fragment containing two duplicated gene coding for a putative membrane protein. The sequence of this fragment, obtained on 19 Mycoplasma capricolum subsp. capripneumoniae (Mccp) strains from various geographical locations, gave 11 polymorphic positions. The three mutations found on gene H2prim were silent and did not appear to induce any amino acid modifications in the putative translated protein. The second gene may be a pseudogene not translated in vivo, as it bore a deletion of the ATG codon found in the other members of the "Mycoplasma mycoides cluster" and as the six mutations evidenced in the Mccp strains would induce modifications in the translated amino acids. In addition, an Mccp strain isolated in the United Arab Emirates showed a deletion of the whole pseudogene, a further indication that this gene is not compulsory for mycoplasma growth. Four lineages were defined, based on the nucleotide sequence. These correlated relatively well with the geographical origin of the strains: North, Central or East Africa. The strain of Turkish origin had a sequence similar to that found in North African strains, while strains isolated in Oman had sequences similar to those of North or East African strains. The latter is possibly due to the regular import of goats of various origins. Similar molecular epidemiology tools have been developed by sequencing the two operons of the 16S rRNA gene or by AFLP. All these various techniques give complementary results. One (16S rRNA) offers the likelihood of a finer identification of strains circulating in a region, another (H2) of determining the geographical origin of the strains. These tools can make a very useful contribution to understanding the epidemiology of CCPP.  相似文献   
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