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   27篇
  免费   2篇
  国内免费   1篇
林业   2篇
  2篇
综合类   2篇
农作物   6篇
水产渔业   8篇
畜牧兽医   6篇
园艺   1篇
植物保护   3篇
  2019年   2篇
  2018年   1篇
  2016年   1篇
  2015年   3篇
  2013年   1篇
  2012年   4篇
  2011年   5篇
  2009年   1篇
  2008年   1篇
  2007年   2篇
  2005年   1篇
  2003年   1篇
  2002年   3篇
  1998年   1篇
  1994年   1篇
  1978年   1篇
  1966年   1篇
排序方式: 共有30条查询结果,搜索用时 15 毫秒
21.
22.
Samples of 4285 individuals from a hybridSolanum phureja Juz. et Buk. —S. stenotomum Juz. (Phu-Stn) and 105 individuals ofSolanum phureja (Phu) diploid potato populations were twice inoculated with potato virus Y strain “o” (PVY°) using the air brush technique. After discarding seedlings with PVY visual symptoms both in the greenhouse and in the field, 1508 seedlings were judged to be resistant to PVY° (35.2%). Only 5.7% of the Phu seedlings were PVY° resistant compared to 35.2% of the Phu-Stn seedlings. At harvest, a mild selection pressure for yield and tuber appearance was applied and 602 Phu-Stn clones were chosen for further evaluation. Selected clones were re-evaluated for PVY° resistance in the greenhouse. Clones were mechanically inoculated twice with PVY°. Clones susceptible to PVY° were determined by visual observations, ELISA (Enzyme-linked immunosorbent assay) tests, grafting of tobacco PVY° infected shoots on potato clones, and infectivity tests usingNicotiana tabacum as a PVY° plant indicator. In the process, 224 clones were found to be extreme resistant to infection by PVY°, with an overall frequency for PVY° extreme resistance of 5.2%. In another experiment, the first year Phu-Stn PVY° resistant clones (554 clones) were mechanically inoculated twice with “common” strain of potato virus X (PVX). Similarly, we discarded clones susceptible to PVX by combining visual evaluation and ELISA with PVX re-inoculation of negative clones and an infectivity test, usingGomphrena globosa as a PVX plant indicator. After this process, seven extreme resistant and eight resistant clones to infection by PVX were found; the overall frequency of PVX extreme resistance was 1.3%. Five clones were extreme resistant to both PVY° and PVX.  相似文献   
23.
An exhaustive exploration into the metabolic content of the Mediterranean sponge Axinella-polypoides resulted in the isolation of the new betaine 5 and the new cyclonucleoside 8. The structures of the new metabolites were elucidated by spectroscopic methods assisted by computational methods. The analysis also provided evidence that the sponge does not elaborate pyrrole-imidazole alkaloids (PIAs) but, interestingly, it was shown to contain two already known cyclodipeptides, compounds 9 (verpacamide A) and 10.  相似文献   
24.
Serious losses have occurred at the U.S. Fish and Wildlife Service, Craig Brook National Fish Hatchery, East Orland, Maine, among eggs that were taken from Atlantic Salmon Salmo salar, which were held as captive broodfish during their returns to the Penobscot River, Naraguagus River, and Machias River to spawn. Bacterial isolations were attempted from external surfaces and the internal contents of individual eggs. Externally and in all cases, Pseudomonas fluorescens was the predominant bacterium associated with the surface of all eggs. These bacteria were resistant to a surface treatment of 1,667 ppm formalin for 15 min and, therefore, the monoclonal nature of P. fluorescens on egg surfaces was considered to result from its ability to resist the germicidal activity of formalin administered for antifungal treatments. Flavobacterium psychrophilum, the cause of bacterial coldwater disease, was isolated from the interior of 23.6, 18.1, and 29.2% of the dead Atlantic Salmon eggs from Penobscot River egg lots A-98, A-100, and A-101, respectively, and concentrations of this pathogen ranged from 1.0 × 103 to >5 × 108 CFU per gram of dead egg. Flavobacterium psychrophilum was also isolated from 8.3, 26.7, and 10.0% of the dead eggs from Naraguagus River egg lots N-158, N-161, and N-163, respectively, in which concentrations of this organism ranged from 1.0 × 103 to 7.5 × 108 CFU per gram of egg. This bacterium was also isolated from within 18.3% and 3.3% of the dead eggs from Machias River egg lots M-128 and M-142, respectively, and its concentrations ranged from 1.0 × 103 to 1.5 × 108 CFU per gram of egg. The finding of F. psychrophilum from within these eggs is indicative of this pathogen's widespread and persistent prevalence in Atlantic Salmon in New England.

Received December 19, 2014; accepted May 4, 2015  相似文献   

25.
Measurements of strontium-90 in waters residing on the Bahama Banks for periods between 12 and 180 days suggest that fallout rates onto these waters are substantially the same as the average rates at all fallout collection stations between 20 degrees and 30 degrees north latitude. If the amount of preciptation on the Bahama Banks is reasonably representative of the oceanic areas in this latitude band, our results support the conclusion that the amount of strontium-90 deposited per unit area of ocean surface is within a factor of 2 of that on land.  相似文献   
26.
Chemical analysis of the Mediterranean ascidian Polyandrocarpa zorritensis (Van Name 1931) resulted in the isolation of a series of molecules including two monoindole alkaloids, 3-indolylglyoxylic acid (3) and its methyl ester (4), 4-hydroxy-3-methoxyphenylglyoxylic acid methyl ester (1) and a new alkaloid we named zorrimidazolone (2). The structure of the novel compound 2 has been elucidated by spectroscopic analysis and bioactivity of all compounds has been investigated. Zorrimidazolone (2) showed a modest cytotoxic activity against C6 rat glioma cell line.  相似文献   
27.
In this study we investigated the effect of an ethanolic extract of propolis, with and without CAPE, and some of its components on cyclooxygenase (COX) activity. Propolis (0.00003-0.03%) significantly and concentration-dependently inhibited COX activity from lung homogenate of saline- or LPS-treated rats. Same results were obtained with CAPE (0.1-100 microM). COX activity from lung homogenate of saline- or LPS-treated rats was also inhibited by galangin (0.1-100 microM), although the inhibition induced by the lowest concentration was not significant. Caffeic, ferulic, cinnamic and chlorogenic acids and pinocembrin, (0.1-100 microM) did not affect COX activity. The inhibition curves showed that CAPE and propolis were equipotent inhibitors, whereas galangin was significantly (P<0.001) less potent than propolis and CAPE. In order to better investigate the role of CAPE, we tested the action of an ethanolic extract of propolis (0.00003-0.03%) without CAPE. This extract significantly and concentration-dependently inhibited COX activity from lung homogenate of saline- or LPS-treated rats, however, it resulted to be approximately 10 times less potent than the extract containing CAPE. The analysis of the inhibition curves of the extract with and without CAPE showed a significant (P<0.001) difference. These results suggest that both CAPE and galangin contribute to the overall activity of propolis, CAPE being more effective.  相似文献   
28.

Background  

Responsiveness to changing photoperiods from summer to winter seasons is an important but variable physiological trait in most temperate-zone mammals. Variation may be due to disorders of melatonin secretion or excretion, or to differences in physiological responses to similar patterns of melatonin secretion and excretion. One potential cause of nonphotoresponsiveness is a failure to secrete or metabolize melatonin in a pattern that reflects photoperiod length.  相似文献   
29.
30.
  • 1. The fishing effort and turtle catch of vessels harbouring at Lampedusa island and fishing in the wider central Mediterranean area was monitored using a voluntary logbook programme. Two large trawlers were monitored between 2003 and 2005 and six small vessels using trawl nets, pelagic longline or bottom longline were monitored in the summer 2005.
  • 2. The observed turtle catch rates of pelagic longline and bottom trawl were among the highest recorded in the basin, and high catch rates by bottom longline were observed too. This suggests that the area contains major oceanic and neritic habitats for the loggerhead turtle Caretta caretta in the Mediterranean Sea.
  • 3. When fishing effort is considered, these results suggest a very high number of captures by Italian trawlers and longliners in the area, as well as by fleets from other countries. This is reason of concern for the conservation of the loggerhead turtle within the Mediterranean Sea.
  • 4. Different fishing gear have different technical/operational characteristics affecting turtle catch and mortality and the present knowledge about associated parameters of these gear varies too.
  • 5. All this considered, specific actions are recommended: (i) an awareness campaign to fishermen to reduce post‐release mortality, (ii) technical modifications to pelagic longline gear to reduce turtle catch, (iii) further investigation into turtle bycatch in all fishing gear, with priority given to bottom longline fishing and quantification of mortality caused by trawlers, (iv) assessment of the turtle populations affected by fishing activity in the area, and (v) international cooperation in undertaking threat assessments, and implementing regulations, management measures and monitoring.
Copyright © 2007 John Wiley & Sons, Ltd.  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