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排序方式: 共有78条查询结果,搜索用时 15 毫秒
1.
选取年龄、胎次、品种基本一致的哺乳母猪20头,随机分成对照组和试验组,试验分两批进行,每批10头.在相同的环境条件下,母猪自由饮水,饲喂同一哺乳母猪料.母猪分娩后4 d内,采用原场饲养制度,逐步增加哺乳母猪采食量,第5天开始,对照组采用不限量饲喂,试验组采用限量和添加哺乳母猪补充料的饲喂方式,仔猪21日龄断奶.结果显示两组仔猪21日龄的断奶窝重、母猪断奶后再发情时间和母猪哺乳失重等差异均不显著(P>0.05). 相似文献
2.
Andrew W. Farnham Norman F. Janes Bhupinder P. S. Khambay 《Pest management science》1989,25(2):205-218
Synthesis of a range of 1-, 2-and 3-phenyl, benzyl and phenethyl substituted cyclopentanols and cyclopentylmethyl alcohols and related unsaturated compounds is reported. Results of bioassays of their esters with known pyrethroidal acids against two species of insect lead to recognition of some structure-activity relationships in this series. The distance and relative orientation between the alcoholic and aryl functions appears crucial, but in other respects the nature of the spacer group between them is less important. The most effective alcoholic components are based on cyclopentenes. 相似文献
3.
Ahmet E. Baydar Michael Elliott Andrew W. Farnham Norman F. Janes Bhupinder P. S. Khambay 《Pest management science》1988,23(3):247-257
Optimisation of activity within the structural constraints defined by the preceding work, by varying the substituents on phenyl in the acid fragment (10 variations), the nature of the group fulfilling the dimethyl function (three variations), the central linking group (four variations) and the presence or absence of a 4-fluoro substituent in the alcohol fragment, has led to achiral compounds as active as bioresmethrin against houseflies and mustard beetles. Statistical analysis of the effects has shown that particular combinations, for instance the cyclopropyl form of dimethyl with a central E-alkene group (but not a central ether group), lead to higher activity than expected. 4-Fluoro substitution enhances activity more strongly against mustard beetles. Difluorocyclopropyl compounds are on average slightly more active than cyclopropyl analogues. 相似文献
4.
Michael Elliott Richard L. Elliott Norman F. Janes Bhupinder P. S. Khambay David A. Pulman 《Pest management science》1986,17(6):691-700
Over 100 benzyl esters of pyrethroidal acids were synthesised and tested for insecticidal activity to establish detailed structure–activity relationships in compounds with side-chains similar to those in the natural pyrethrins. Alkenyl, and corresponding alkynyl, side-chains were effective, both at the 3- and 4-positions, as were side-chains with extended substitution in either E or Z forms. A cyano group at the α-position increases activity if the side-chain is at C-3, but lowers it drastically if the substituent is at C-4. Similarly, methyl groups at C-2 and/or C-6 may increase activity whether the unsaturated side-chain is at C-3 or C-4, but only in the absence of an α-cyano group. 相似文献
5.
Logendra LS Gianfagna TJ Specca DR Janes HW 《HortScience : a publication of the American Society for Horticultural Science》2001,36(5):893-896
Limited-cluster production systems may be a useful strategy to increase crop production and profitability for the greenhouse tomato (Lycopersicon esculentum Mill). In this study, using an ebb-and-flood hydroponics system, we modified plant architecture and spacing and determined the effects on fruit yield and harvest index at two light levels. Single-cluster plants pruned to allow two leaves above the cluster had 25% higher fruit yields than did plants pruned directly above the cluster; this was due to an increase in fruit weight, not fruit number. Both fruit yield and harvest index were greater for all single-cluster plants at the higher light level because of increases in both fruit weight and fruit number. Fruit yield for two-cluster plants was 30% to 40% higher than for single-cluster plants, and there was little difference in the dates or length of the harvest period. Fruit yield for three-cluster plants was not significantly different from that of two-cluster plants; moreover, the harvest period was delayed by 5 days. Plant density (5.5, 7.4, 9.2 plants/m2) affected fruit yield/plant, but not fruit yield/unit area. Given the higher costs for materials and labor associated with higher plant densities, a two-cluster crop at 5.5 plants/m2 with two leaves above the cluster was the best of the production system strategies tested. 相似文献
6.
Rockwool is an excellent growing medium for the hydroponic production of tomato; however, the standard size rockwool blocks [4 x 4 x 2.5 inches (10 x 10 x 6.3 cm) or 3 x 3 x 2.5 inches (7.5 x 7.5 x 6.3 cm)] are expensive. The following experiments were conducted with less expensive minirock wool blocks (MRBs), on rayon polyester material (RPM) as a bench top liner, to reduce the production cost of tomatoes (Lycopersicon esculentum) grown in a limited-cluster, ebb and flood hydroponic cultivation system. Fruit yield for single-cluster plants growing in MRBs [2 x 2 x 1.6 inches (5 x 5 x 4 cm) and 1.6 x 1.6 x 1.6 inches (4 x 4 x 4 cm)] was not significantly different from plants grown in larger sized blocks (3 x 3 x 2.5 inches). When the bench top was lined with RPM, roots penetrated the RPM, and an extensive root mat developed between the RPM and the bench top. The fruit yield from plants on RPM was significantly increased compared to plants without RPM due to increases in fruit size and fruit number. RPM also significantly reduced the incidence of blossom-end rot. In a second experiment, single- and double-cluster plants were grown on RPM. Fruit yield for double-cluster plants was 40% greater than for single-cluster plants due to an increase in fruit number, although the fruit were smaller in size. As in the first experiment, fruit yield for all plants grown in MRBs was not significantly different from plants grown in the larger sized blocks. MRBs and a RPM bench liner are an effective combination in the production of limited-cluster hydroponic tomatoes. 相似文献
7.
Dipterous blood-sucking insects (horseflies, black flies, gnats, midges) have negative impacts on the performance of draught horses in forest enterprises. For the protection of these animals, the following preparations were applied at the interval of 24 hours: diethyltoluamide, Oxamat (N,N-diethyloxamine acid, USSR) and Stomoxin (synthetic pyrethroid, product of the firm Wellcome, England). In the course of 66 working days, the performance of test animals treated with 10% water emulsion of diethyltoluamide increased by 49.25 cu. m. of skidded wood, i.e. by 0.74 cu. m. wood per horse/day (21.65%), as compared with the control group. The daily savings of prime costs per test horse/day made 16.99 Kcs (Czechoslovak crowns). In comparison with the control group, the performance of horses treated with 5% water emulsion of Oxamat increased by 85.50 cu. m. wood, i.e. by 1.29 cu. m. wood per horse/day (38.00%). Stomoxin at the concentration of 0.05% acted as a good insecticide but had no marked repellent effect. The results of this study document that the production of effective repellents should be introduced in the Czechoslovak Socialist Republic. 相似文献
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