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41.
In this study, the technical performance of culture, two commercially available polymerase chain reaction (PCR) tests, rapid plate agglutination (RPA) test, hemagglutination inhibition (HI) test, and eight commercially available enzyme-linked immunosorbent assays (ELISAs) were compared for the detection of avian mycoplasma infections from 3 days postinfection (d.p.i.) through 35 d.p.i. The tests were carried out on samples from specified pathogen-free layers that were infected at 66 wk of age with recent Mycoplasma synoviae (MS) and Mycoplasma gallisepticum (MG) field strains, MS and MG ATCC strains, and Mycoplasma imitans (MIM), respectively. Results showed a high percentage of positive samples in the homologous infected groups and a high percentage of negative samples (100%) in the uninfected and heterologous infected groups during 35 d.p.i. of both culture and PCR tests. For the group infected with the MG 15302 ATCC strain, serology was more sensitive than bacteriology. All MG and MS tests, with the exception of MG ELISA kit D showed a lower percentage of positive samples during 35 d.p.i. for the detection of the MG and MS ATCC strain infection compared with that of the field strains. Also, the number of cross-reactions (false positives) in the serologic tests was lower after infection with an ATCC strain than after an infection with the MG or MS field strain. Contradictory to other studies, the ELISAs and the RPA test using undiluted serum showed a relatively high number of false-positive results. The MG ELISAs (except ELISA kit D) showed more false-positive results (up to 37%) in the MIM-infected group than in the MS-infected groups. This was not unexpected, as MIM and MG have a close antigenic relationship. The results of the serologic tests in this study showed that a certain level of false-positive results can be expected in about any serologic test. Although the level of false-positive results varied between several serologic tests, this study showed that it is not advisable to rely completely on one test (system) only.  相似文献   
42.
43.
Nine calves between three and 18 weeks old with serologically confirmed natural bovine respiratory syncytial virus infection were examined clinically, radiographically and by radionuclide lung perfusion imaging. The results were compared with those from seven healthy calves. The diseased calves were euthanased and examined pathologically, virologically and bacteriologically. The clinical signs indicated that the disease was in an acute stage. Radiography of the diseased animals revealed cysts, corresponding morphologically with bullous emphysema, and infiltrations roughly corresponding in distribution with atelectatic and, or, pneumonic areas. Radionuclide lung perfusion imaging revealed no perfusion shifts between the left and right lungs and a normal perfusion pattern in five of the nine diseased calves. The abnormalities in the perfusion patterns of three calves were probably caused by anatomical disorders such as cysts and pleural adhesions, but no cause of the abnormality could be found in one calf. These findings suggest that in calves infected with bovine respiratory syncytial virus, the normal perfusion pattern is maintained until anatomical disorders occur. The pathological examination and radiography revealed that the cranioventral lung fields were particularly poorly ventilated. This finding and the normal perfusion pattern indicate that these parts of the lungs are probably the sites where shuntings and perfusion-ventilation mismatchings occur.  相似文献   
44.
A live vaccine based on an attenuated Salmonella gallinarum 9R strain is in use in a Salmonella enteritidis control program in commercial layer flocks in The Netherlands. In a field study, the potential spread of the vaccine strain from vaccinated flocks to nonvaccinated flocks has been studied after both the primary and the booster injection at four different rearing farms and at one layer farm. The vaccinated and the nonvaccinated flocks were monitored at regular intervals by bacteriologic and serologic examination. In this field study, no evidence was found for the fecal spread of the vaccine strain.  相似文献   
45.
Synchronization of the oestrous cycle of gilts using altrenogest treatment has been found to increase ovulation rate. The current experiment investigated if the increase in ovulation rate after altrenogest treatment is related to increased follicle size at the end of altrenogest treatment compared with late luteal phase follicles. Crossbred gilts (n = 15) received altrenogest during 18 days [20 mg Regumate (Janssen Animal Health, Beerse, Belgium)], starting 5-7 days after onset of first oestrus. Control gilts (n = 15) did not receive altrenogest. At days 10-12 of the oestrous cycle [i.e. in the presence of corpora lutea (CL)], average follicle development was 2.51 +/- 0.20 mm (assessed with ultrasound) in altrenogest-treated gilts and 2.58 +/- 0.16 mm in control gilts (p > 0.10). During the last days of altrenogest treatment (i.e. when CL had gone into regression), average follicle size had increased to 3.01 +/- 0.31 mm (p < 0.05). Subsequent ovulation rate was 16.6 +/- 1.7 in altrenogest treated gilts and 15.1 +/- 1.2 in control gilts (p < 0.05). Altrenogest treatment resulted in increased follicle size after regression of the CL, showing that suppression of follicle growth by altrenogest alone is less severe than suppression by endogenous progesterone (either with or without altrenogest). Altrenogest treatment also resulted in a higher ovulation rate. However, it is unclear if the increased follicle size and higher ovulation rate after altrenogest treatment are causally related, as the relation between the two on an animal level was not significant.  相似文献   
46.
Dilation of the caudal vena cava (CVC) on lateral thoracic radiographs is often interpreted as suggestive of right-sided congestive heart failure. To quantitate the clinical utility of evaluating CVC size as an indicator of right-sided heart disease, we compared the ratio of the diameter of the CVC as measured on a left lateral thoracic radiograph to the descending aorta (Ao), length of the thoracic vertebra above the tracheal bifurcation (VL), and width of the right fourth rib (R4) in 35 dogs with right heart disease and 35 control dogs. Each CVC ratio (CVC/Ao, CVC/VL, CVC/R4) was statistically larger in dogs with right heart disease. Response operating characteristic curves and likelihood ratios were used to determine ratios helpful in identifying dogs with right heart disease. A CVC/Ao > 1.50, CVC/VL > 1.30, or CVC/R4 > 3.50 are strongly suggestive of a right-sided heart abnormality in a patent.  相似文献   
47.
Separate mechanisms exist for transporting ingesta and gas from the caecum to the colon. Both involve the isolation of the cranial part of the base by a constriction cranial to the ileal papilla. This involves elevation of the floor of the base and is associated with dilation of the caecocolic ostium which at other times is closed. Contraction of the ingesta-filled cranial compartment expels some material to the colon but allows most to return to the body. Contractions which discharge gas do not result in the passage of significant amounts of ingesta. The gas expelled is at once hurried through much of the ascending colon. Any considerable reflux to the caecum is prevented by the sigmoid configuration of the caecocolic junction.  相似文献   
48.
Field dispersal studies are seldom conducted at regional scales even though reliable information on mid-range dispersal distance is essential for models of colonization. The purpose of this study was to examine the potential distance of dispersal of Rhizophora mangle propagules by comparing deposition density with landscape characteristics of mangrove forests. Propagule density was estimated at various distances to mangrove sources (R. mangle) on beaches in southwestern Florida in both high-and low-energy environments, either facing open gulf waters vs. sheltered, respectively. Remote sensing and Geographic Information Systems were used to identify source forests and to determine their landscape characteristics (forest size and distance to deposition area) for the regression analyses. Our results indicated that increasing density of propagules stranded on beaches was related negatively to the distance of the deposition sites from the nearest stands of R. mangle and that deposition was greatly diminished 2 km or more from the source. Measures of fragmentation such as the area of the R. mangle forests were related to propagule deposition but only in low-energy environments. Our results suggest that geographic models involving the colonization of coastal mangrove systems should include dispersal dynamics at mid-range scales, i.e., for our purposes here, beyond the local scale of the forest and up to 5 km distant. Studies of mangrove propagule deposition at various spatial scales are key to understanding regeneration limitations in natural gaps and restoration areas. Therefore, our study of mid-range propagule dispersal has broad application to plant ecology, restoration, and modeling.  相似文献   
49.
Li S  Tam YK  Hartman GL 《Phytopathology》2000,90(5):491-497
Fusarium solani is a soilborne plant pathogen that infects many different hosts. Within the species, there is some specialization, and a number of forma specialis have been described based on host affiliation. One of these, F. solani f. sp. glycines, infects soybean and causes sudden death syndrome. To differentiate between F. solani f. sp. glycines and other F. solani isolates, a partial sequence of the mitochondrial small subunit (mtSSU) rRNA gene was amplified by polymerase chain reaction and sequenced from 14 F. solani f. sp. glycines and 24 F. solani isolates from various plant hosts. All F. solani f. sp. glycines isolates had identical sequences. A single, unique insertion of cytosine occurred in all F. solaniisolates but not in any of the F. solani f. sp. glycines isolates. Two major lineages, distinguished by sequence divergence and the presence or absence of multiple insertions, occurred in F. solani isolates. Cladistic analysis produced a single most-parsimonious tree with three major clades. The first clade contained all F. solani f. sp. glycines isolates. A second clade grouped together all of the F. solani isolates that had only a single nucleotide insertion difference from the first clade. Genetic distance between these two clades was 0.016. A third clade was formed by five F. solaniisolates that had multiple insertions. Isolates in the third clade had a genetic distance of 0.040 from the first and second clades. Based on the sequence data, it is likely that F. solani f. sp. glycineshas a shorter evolutionary history than other F. solaniisolates that have either single or multiple nucleotide insertions. The differences in nucleotide insertions in part of the mtSSU rRNA gene between F. solani f. sp. glycinesand other F. solani isolates provide a direct and reliable way to distinguish isolates of F. solani.  相似文献   
50.
Development of durable resistance to soybean rust (SBR) is challenging due to the pathogenic diversity of Phakopsora pachyrhizi populations. The objective of this research was to investigate and confirm the genomic locations of Rpp genes in the Ugandan line UG-5 that confer resistance to different SBR pathotypes. Bulked segregant analysis revealed two genomic regions associated with resistance in a cross with rust-susceptible 'Williams 82'. Composite interval mapping in the F2 and F2:3 populations had a LOD score of 48.7 in a region 0.38 cM away from the estimated location of the Rpp1 locus on chromosome (Chr.) 18. An approximately 23-Kbp interval spanning the Rpp1 locus was flanked by SNP markers ss715632313 and ss715632318. Another interval was identified at the Rpp3 locus on Chr. 6 between markers Satt100 and ss715594488 (2.4 cM) in the F2 population and between Satt100 and ss715594874 (4.3 cM) in the F2:3 population, with a maximum LOD score of 25.6. UG-5 was thus confirmed to have SBR resistance genes at the Rpp1 and Rpp3 loci that can be pyramided into other elite cultivars.  相似文献   
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