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排序方式: 共有279条查询结果,搜索用时 11 毫秒
1.
用氟乐灵和精稳杀得或高效盖草能进行桑苗圃除草,用草甘磷和乙草胺混合进行桑园除草,可有效地防除杂草。  相似文献   
2.
选择9头母牛先行人工授精、7天后再移植冷冻胚胎以生产双犊。试验结果表明,母牛产双犊达44.44%(P<0.01)。提示:采用A(I人工授精)+ET(胚胎移植)是提高母牛双犊率的有效技术措施之一。  相似文献   
3.
丑洋  郭琴 《农业工程》2018,8(1):53-56
农村住宅建设是新农村建设的重要组成部分,在农村经济、社会、生态和文化发展等方面发挥着重要作用。从生态住宅建设角度出发,借鉴国外农村住宅建设经验,依据我国农村住宅建设现状,通过国内外农村住宅建设对比分析,总结国外农村生态住宅建设对我国的启示。   相似文献   
4.
秈粳稻杂交育种研究   总被引:5,自引:0,他引:5  
作者研究了秈粳杂种的生育特性及结实性等经济性状的遗传变异,认为以出穗期为主要指标进行选择,结合其他性状的变异动态,逐步确立优良系统,有助于提高选择的效率,和建立较为合理的杂交育种程序与方法。  相似文献   
5.
Using the hard clam farms in Yunlin, Taiwan as examples, this study analyzes the effects of culture area, stocking density, and shrimp and fish polyculture on the cost efficiency (CE) of hard clam farming. A data envelopment analysis (DEA) is used to estimate the farms' technical efficiency (TE), allocative efficiency (AE), and CE values. The findings show that the mean TE, AE, and CE values of hard clam farms are 0.74, 0.57, and 0.43, respectively. The TE value is higher than the AE value, which indicates that cost inefficiency is mainly attributable to poor AE. Tobit regression results suggest that there are positive relationships between CE and both culture area and operator experience. Hard clam stocking density and age of the operators have negative effects on CE. Hard clam culture areas larger than 2 ha and a stocking density of 1.1–1.2 million hard clams per hectare have higher CEs than smaller culture areas and smaller or larger stocking densities. The use of sand shrimp, white shrimp, kuruma shrimp, and grass shrimp for polyculture and the use of milkfish and silver sea bream for polyculture are both associated with high CEs.  相似文献   
6.
This study evaluated the reproductive performance of gilts inseminated at three intervals before ovulation (0-12, 13-23, 24-30 h) with sperm doses (SD) stored for 0-48 and 96-120 h. A total of 218 PIC Camborough 22 gilts were inseminated once with SD of 1.5 x 10(9) sperms. Pregnant gilts (n = 166) were slaughtered 30.8 +/- 3.7 days after artificial insemination. The number of corpora lutea (CL) and total embryos (TE) was counted. Pregnancy rates (PR) were analysed by chi-square test. TE and embryonic survival (ES), obtained as the ratio between viable embryos and CL, were analysed by GLM procedure (SAS) and mean values were compared by Tukey's test. Pregnancy rate was similar among artificial insemination-ovulation (AIOV) intervals when semen was stored for 0-48 h. However, the lowest PR was observed in the 24-30 h AIOV interval with storage time (ST) of 96-120 h (p < 0.05). There was a significant effect of the interaction between ST and AIOV (p < 0.05) on TE and ES variables. Total embryos and ES did not differ (p > 0.05) among AIOV intervals in ST of 0-48 h. However, gilts inseminated at 24-30 h AIOV interval with ST of 96-120 h showed a reduction of 6.7 embryos (p < 0.05) compared with gilts in the same interval inseminated with semen stored for 0-48 h. ES for the 24-30 h AIOV interval and ST of 96-120 h was lower than that observed in the other groups (p < 0.05).  相似文献   
7.
A program of research named Towards an Integrative Biology (TAIB) has recently been promoted by the International Union of Biological Sciences, involving multidisciplinary and interdisciplinary research. Studies of Miscanthus plants which emphasized the TAIB theme were undertaken. Miscanthus species are the most widely distributed and dominant species in Taiwan, growing everywhere from the coastal to mountainous areas, and from agricultural to polluted land. Particularly, the grasses grow well in habitats under environmental stresses. Physiological and genetic adaptations are fundamental mechanisms for these grasses' survival in stressful environments. Findings based on field measurements and laboratory analyses were able to elucidate some of the mechanisms of grasses adapted to stressful environments. Adaptive radiation occurred when most niches were open during the postglacial periods. Particularly, population discontinuity of the grasses was found on the Orchid and Green islets of Taiwan. Likewise, Miscanthus sinensis var. glaber and var. formosanus occupied lands from low to middle elevations of Taiwan, while Miscanthus transmorrisonensis appeared in the highlands above 2400 m. Phylogenetically, Miscanthus has evolved into various ecotypes, varieties and species in Taiwan as well as in other parts of Asia. The grass then evolved into Miscanthus floridulus , M. sinensis var. formosanus , Miscanthus flavidus , then to M. transmorrisonensis . Furthermore, the phylogeny of the Miscanthus sinensis complex of Taiwan was reconstructed by cladistic analysis on nucleotide sequences of nuclear ribosomal DNA internal transcribed spacers (nrDNA ITS) region and atpB - rbc L non-coding spacer of the chloroplast DNA. Rooted at M . floridulus the monophyly of M . sineneis was significantly supported by molecular evidence. The origin of this complex could be dated to the last glacial withdrawal about 20 000 years ago.  相似文献   
8.
红皮云杉嫩枝扦插繁殖技术的研究   总被引:9,自引:0,他引:9  
本文描述了红皮云杉嫩枝扦插繁殖技术。通过试验筛选出1种适合于红皮云杉嫩枝扦插的基质(插壤),2种使生根率达98%且根系发育良好的生根剂。同时,提出了把握扦播时机,合理运用生根剂浓度及处理时间的方法和技术措施。  相似文献   
9.
Large scale P. radiata monoculture has been in existence in New Zealand for over 60 years. During this time a number of damaging diseases (e. g. Sirex-Amylostereum, Dothistroma, Armillaria, Cydaneusma needle cast. Sphaeropsis die-back etc.) have occurred but the impact was by no means devastating as these diseases are either controllable or in some the losses were deemed acceptable. As a large proportion of the biomass produced before age 10–12 is waste-thinned, the acceptable level of disease loss is thereby very high. The practice of clear felling and short rotation reduces some of the disease risks common in other forest systems. Outlook for future disease threat is discussed with respect to current trends toward clonal forestry and the possible arrival of additional exotic pathogens.  相似文献   
10.
The pro-oxidant activities of baicalein, morin, myricetin, quercetin, and rutin were examined in various cell-containing systems including human platelets, rat vascular smooth muscle cells, human umbilical vein endothelial cells (HUVECs), human THP-1 cells, and fibroblast cells. Electron spin resonance (ESR) results showed that only baicalein generated hydroxyl radicals in a resting human platelet suspension, whereas the other flavonoids showed no effects on any of the resting cell systems. A low concentration of arachidonic acid (AA) increased the intensity of hydroxyl radicals, but a high concentration inhibited it. Collagen and thrombin, platelet aggregatory agents that can cause the release of AA by platelets, enhanced baicalein-induced hydroxyl radical formation, whereas ADP and U44619 showed no significant effects. Quinacrine and 5,8,11,14-eicosatetraenoic trifluoromethyl ketone, both PLA2 inhibitors, significantly attenuated baicalein-induced hydroxyl radical formation. These results suggest that baicalein-induced hydroxyl radical formation is associated with AA metabolite enzymes in human platelets. The formation of hydroxyl radicals was significantly inhibited by lipoxygenase inhibitors including nordihydroguaiaretic acid, (-)-epicatechin, (-)-epicatechin gallate, and hinokitiol, but was not affected by desferroxamine or the heme protein inhibitors KCN and NaN3. On the other hand, semiquinone free radicals were generated when baicalein was incubated with horseradish peroxidase/H2O2 or platelets/AA. The semiquinone radicals formed in the platelets/AA system could be extensively inhibited by desferroxamine, diethylenetriaminepentaacetic acid, KCN, and NaN3, indicating that prostaglandin H synthase (PGHS)-peroxidase may be involved. The results of this study led to the proposal that baicalein induces hydroxyl radical formation via 12-lipoxygenase and induces semiquinone radical formation via PGHS-peroxidase in human platelets.  相似文献   
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