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   118篇
  免费   4篇
  国内免费   1篇
林业   20篇
农学   3篇
基础科学   1篇
  16篇
综合类   4篇
水产渔业   32篇
畜牧兽医   34篇
植物保护   13篇
  2021年   2篇
  2020年   3篇
  2019年   4篇
  2018年   2篇
  2017年   3篇
  2016年   2篇
  2015年   4篇
  2014年   5篇
  2013年   2篇
  2012年   7篇
  2011年   10篇
  2010年   4篇
  2009年   5篇
  2008年   11篇
  2007年   10篇
  2006年   7篇
  2005年   9篇
  2004年   3篇
  2003年   4篇
  2002年   4篇
  2001年   4篇
  2000年   3篇
  1999年   3篇
  1998年   4篇
  1996年   1篇
  1994年   1篇
  1992年   1篇
  1988年   1篇
  1987年   1篇
  1985年   2篇
  1983年   1篇
排序方式: 共有123条查询结果,搜索用时 21 毫秒
51.
52.
Continuous high intensity training may induce alterations to enzyme activities related to glucose and lipid metabolism in horses. In our study, five Thoroughbred race horses (3 male and 2 female, avg age=5 yrs old) were compared against five riding horses (1 male, 1 female, 3 gelding, avg age=13 yrs old) in terms of energy metabolism, by examining plasma malate (MDH) and lactate (LDH) dehydrogenase activities and M/L ratio. MDH is involved in NADH and ATP generation, whereas LDH can convert NADH back into NAD(+) for ATP generation. An increase in plasma M/L ratio can reflect heightened energy metabolism in the liver and skeletal muscle of horses adapted to continuous intensive exercise. Moreover, plasma lipid metabolism analytes (adiponectin, NEFA, total cholesterol (T-Cho), and triglycerides (TG)) can reflect changes to lipolysis rate, which can also indicate a change in energy metabolism. Overall, race horses demonstrated increased MDH and LDH activity in plasma (4x and 2x greater, respectively), in addition to a plasma M/L ratio twice as high as that of riding horses (2.0 vs 1.0). In addition, race horses also demonstrated significantly higher levels of plasma NEFA (50% greater), TG (2x greater), and T-Cho (20% greater) as compared to riding horses. Therefore, race horse muscles may have adapted to prolonged high intensity endurance exercise by gaining a higher oxidative capacity and an increased capacity for fat utilization as an energy source, resulting in heightened energy metabolism and increased rate of lipid mobilization.  相似文献   
53.
Generic equations are proposed for stem, branch and foliage biomass of individual trees in even-aged pure stands of Cryptomeria japonica, Chamaecyparis obtusa and Larix kaempferi. Biomass data was collected from a total of 1,016 individual trees from 247 stands throughout Japan, and five regression models were assessed by root mean square error, mean bias, fit index (FI), and AIC. The results show that a power equation using diameter at breast height (dbh) and height is the most suitable for all species and components. This equation is more accurate than the familiar power equation that uses ‘dbh2 height’, and it expresses the greater volume of branch and foliage mass of trees with a lower height/diameter ratio. A power equation using dbh is more reasonable for models with dbh as the only independent variable and more accurate than a power equation using ‘dbh2 height’ for estimating branch and foliage mass. Estimating error for branch and foliage mass is larger than that for stem mass, but the entire aboveground biomass can be estimated with an error of less than 19%, except in the case of small trees with dbh less than 10 cm.  相似文献   
54.
Indigestible oligosaccharides have been shown to normalize blood glucose and insulin concentration thereby promoting good health and preventing diseases, such as diabetes. Transglucosidase (TG, α-glucosidase, enzyme code (EC) 3.2.1.20) is an enzyme capable of converting starch to oligosaccharides, such as iso-malto-oligosaccharides from maltose, via the action of amylase. The aim of this study was to evaluate whether oral administration of TG with maltose or dextrin is capable of reducing post-prandial serum glucose concentration in experimentally streptozotocin (STZ)-induced diabetic dogs fed on a high-fiber diet. Five healthy and five STZ-induced diabetic dogs were employed in this study. TG supplementation with dextrin or maltose had no detrimental effect in healthy dogs. In fact, TG and dextrin exhibited a flatlined serum glucose pattern, while reducing mean post-prandial serum insulin and glucose concentration as compared to control diet alone. When TG supplementation was tested in STZ-induced diabetic dogs under the context of a high fiber diet, a 13.8% and 23.9% reduction in mean glucose concentration for TG with maltose and dextrin, respectively was observed. Moreover, TG with dextrin resulted in a 13% lower mean post-prandial glucose concentration than TG with maltose, suggesting that dextrin may be a more efficient substrate than maltose when used at the same concentration (1 g/kg). Our results indicate that TG supplementation with diet can lead to lower postprandial glucose levels versus diet alone. However, the efficacy of TG supplementation may depend on the type of diet it is supplemented with. As such, TG administration may be useful for preventing the progression of diabetes mellitus and in its management in dogs.  相似文献   
55.
The development of a layout plan for a new plant with the aid of genetic algorithms was studied to place the machines so that the plant floor was effectively utilized and the operation would not be impeded. Genetic algorithms are search algorithms based on the mechanics of natural evolution and natural genetics to solve problems in engineering fields. Simulation with the aid of genetic algorithms was undertaken step by step. The first seven hundred strings (chromosomes) were generated at random to organize an initial population. Each string consisted of 40 bits (genes), which represented characteristics of machines (x- andy-coordinates and inlet and outlet formations of materials on machines) in the binary coding. Then the simulation was undertaken by repeating selection, crossover, reproduction, and mutation of strings until all strings were saturated with the highest evaluation (fitness of chromosomes to environments in the case of creatures). Under some limitations, an acceptable layout plan of the modeled plant involving four wood-processing machines was obtained according to evaluation indices.Part III of this series appeared inMokuzai Gakkaishi 37: 702–710, 1991.Part of this report was presented at the 47th annual meeting of the Japan Wood Research Society, Kocht, April 1997  相似文献   
56.
The thermal diffusivity, specific heat, and thermal conductivity of 13 species of wood were measured by means of the laser flash method to investigate the thermal properties of wood during the heating process. The temperature ranged from room temperature to 270°C in air or under vacuum. The thermal diffusivity varied little during the heating process up to 240°C. The values in air were larger than those under vacuum. There was a linear relation between the specific heat and the ambient temperature, and the specific heat under vacuum was larger than that in air at high temperature. The thermal conductivity increased with density and the ambient temperature. To discuss the effects of the atmospheric conditions on the thermal constants of wood, a theoretical model of thermal conductivity was proposed and its validity examined, where the wood was assumed to be a uniformly distributed material composed of cell walls and air.Part of this paper was presented at the 47th annual meeting of Japan Wood Research Society at Kochi, April 1997  相似文献   
57.
A method for measuring the viscoelastic properties of wood under high temperature and high pressure steam was developed using a testing machine with a built-in autoclave. A newly developed load cell capable of resisting a steam pressure of 16kgf/cm2 and a temperature of 200°C was installed in the autoclave. This load cell could be used to determine precisely the loads while steaming at temperatures from 100°C to 200°C. In addition to load-detection problems, it was necessary to avoid the nonuniform thermal degradation of wood during the measurement process under steaming at high temperatures. This nonuniform degradation could be minimized by shortening the time required for the wood to attain thermal equilibrium using specimens conditioned to the fiber saturation point. According to this method, a stress relaxation curve for sugi (Cryptomeria japonica D. Don) wood being compressed while steaming at 180°C was obtained. The stress was seen to decrease rapidly with time, reaching almost zero at 3000s.  相似文献   
58.
The effects of alcohol extract of soybean meal on growth performance, digestibility, and pancreatic enzyme and bile acid status of yellowtail Seriola quinqueradiata were studied. Fish were fed one of the following for 8 weeks: a fish meal (FM) control diet (FMD), a defatted soybean meal diet (SBMD), an alcohol-extracted SBM diet (ExSBMD), an ExSBMD with alcohol-extract diet (ExSBM + ExtD), and an FMD with alcohol-extract diet (FM + ExtD). Growth performance was significantly inferior in fish fed with SBM, ExSBM + ExtD, and FM + ExtD compared to FMD- or ExSBMD-fed fish. Total bile acid levels, and trypsin and lipase activities in the anterior intestine were significantly lower in fish fed with SBM, ExSBM + ExtD, and FM + ExtD than in fish fed with ExSBMD and FMD, despite similar values in gallbladder or pyloric caeca. Cholecystokinin mRNA levels of the former diet-fed fish were significantly lower than those of FMD- or ExSBMD-fed fish. Lipid and protein digestibility of fish fed with SBMD, ExSBM + ExtD, and FM + ExtD was significantly reduced in comparison with that of fish fed with FMD or ExSBMD. These findings indicate that the alcohol extract of soybean meal inhibited the secretion of bile acids and pancreatic enzymes by a decrease of cholecystokinin stimulation. This inhibition seemed to be responsible for a low growth performance through impairment of the assimilation of lipid and protein.  相似文献   
59.
A series of novel 3‐(2,4,6‐trisubstituted phenyl)uracil derivatives has been synthesised and assayed for insecticidal/acaricidal activity. The assay indicated certain requirements for optimal insecticidal activity, which can be summarised as follows: (a) the substituents on the phenyl ring should possess hydrophobicity and electron‐withdrawing properties, and the sum of their volumes determines the level of activity; (b) the substituent at the 6‐position on the uracil ring should also possess electron‐withdrawing properties and hydrophobicity, together with the correct volume; (c) the 1‐position on the uracil ring should be unsubstituted for activity against Nephotettix cincticeps and Epilachna vigintioctopunctata, but substituents with length C3 to C4 may be optimal for activity against Tetranychus urticae; (d) certain substituents at the 5‐position of the uracil ring give activity against E vigintioctopunctata and T urticae, but not against N cincticeps; (e) a thiocarbonyl group at the 2‐position of the uracil ring is less effective than a carbonyl group. Of the compounds assayed, 3‐(2,6‐dichloro‐4‐trifluoromethylphenyl)‐6‐trifluoromethyluracil showed high activity against all the species assayed. © 2000 Society of Chemical Industry  相似文献   
60.
Two groups of red sea bream (average body weight 85 g) were fed to satiation fish meal (FM) or FM‐free soy protein concentrate (SPC)‐based diet (FM‐sat and SPC groups respectively). A third group (FM‐pair) was fed the same amount of FM as of SPC fed to SPC‐sat group for 6 weeks. Growth rate of SPC group was significantly slower than of FM‐sat and FM‐pair groups (p < 0.05). Feed conversion ratios of FM‐sat and FM‐pair groups were similar and were better than that of SPC group (p < 0.05). Visceral fat somatic index of SPC group was significantly lower than of the other groups (p < 0.05), while that of the latter two groups were similar. Plasma triglyceride of FM‐sat and FM‐pair groups was similar and lower than the level of SPC group (p < 0.05). Trypsin activity in hepatopancreas of SPC group was significantly lower than that of other groups (p < 0.05). We suggest a low growth of SPC group was not simply related to low‐feed intake. Feeding of a FM‐free SPC‐based diet may reduce lipid accumulation and consequently lead to low‐growth performance, in red sea bream.  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