全文获取类型
收费全文 | 261篇 |
免费 | 2篇 |
专业分类
林业 | 43篇 |
农学 | 1篇 |
58篇 | |
综合类 | 11篇 |
农作物 | 2篇 |
水产渔业 | 49篇 |
畜牧兽医 | 86篇 |
园艺 | 1篇 |
植物保护 | 12篇 |
出版年
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 24篇 |
2012年 | 16篇 |
2011年 | 17篇 |
2010年 | 4篇 |
2009年 | 10篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 16篇 |
2005年 | 34篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1993年 | 1篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有263条查询结果,搜索用时 15 毫秒
1.
Tomoya TAKAHASHI Akihiro MORI Hitomi ODA Isao MURAYAMA Mitsuhiko KOUNO Toshinori SAKO 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2021,83(2):260
Changes in lipoprotein profiles occur in dairy cows during the periparturient period and in cows with transition cow disease. Here, the lipoprotein profiles of Holstein–Friesian dairy cows during the periparturient period were obtained by anion-exchange, high-performance liquid chromatography to evaluate the usefulness of lipoprotein profile evaluation during the periparturient period and in cows with fatty liver and milk fever. Lipoprotein levels (including total and high- (HDL-C) and low-density lipoprotein (LDL-C) cholesterol) in 10 healthy cows were low 4 weeks prepartum, with the lowest values at calving or within 1 week of calving; the values increased at 8 weeks postpartum. The lipoprotein levels were measured in 16 cows diagnosed with fatty liver (n=10) or milk fever (n=6) and compared to 10 healthy dairy cows. A significant difference was observed in HDL-C between healthy cows (at calving and 1 week postpartum), and the fatty liver and milk fever cows. Cows with fatty liver and milk fever had a lower mean HDL-C than the 10 healthy dairy cows at calving and 1 week postpartum. HDL-C might be a good indicator of energy balance for differentiating healthy cows from those with transition cow disease. 相似文献
2.
3.
A carbonaceous sorbent was prepared from the wood of Japanese larch (Larix leptolepis) by dehydration with concentrated sulfuric acid in a 69% yield. The abilities of the sorbent to remove Cr(VI) from aqueous
solutions were investigated. Research parameters included the initial solution pH, temperature, and initial concentration
of Cr(VI) in solution. The removal of Cr(VI) was highly solution pH dependent and was mainly governed by physicochemical sorption
under weak acidic conditions. The equilibrium data fit well in the Langmuir isotherm model. The Langmuir constants were calculated
at different temperatures, and the sorption capacity increased with rising temperature, indicating the endothermic nature
of the Cr(VI) sorption onto the sorbent. The desorption experiments suggest that the Cr(VI) sorption is generally irreversible,
owing to strong interaction of HCrO
4
−
with the active sites of the sorbent. 相似文献
4.
Antifeedant activity of some flavonoids and their related compounds against the subterranean termiteCoptotermes formosanus Shiraki was examined with nochoice tests and two-choice tests. The activities of these compounds were evaluated in relation to their chemical structures. All flavonoids tested showed antifeedant activity, whereas catechinic acid, possessing no A-ring or pyran ring in the molecule, showed feeding-preference activity. For the structure-activity relations, it was found that compounds containing two hydroxyl groups at C-5 and C-7 in A-rings showed high antifeedant activity. Furthermore, the presence of a carbonyl group at C-4 in the pyran rings of the compounds was necessary for the occurrence of high activity. 3-Hydroxyflavones and 3-hydroxyflavanones with 3,4-dihydroxylated B-rings exhibited higher activity than those with 4-hydroxylated B-rings.Part of this paper was presented at the 49th annual meeting of the Japan Wood Research Society, Tokyo, April 1999 相似文献
5.
Kouichi Ichihara Tosimi Tanaka Isao Sawaguchi Shuji Umeda Katsumi Toyokawa 《Journal of Forest Research》1996,1(1):45-49
This study examines a method for designing an optimum profile of a forest road in a short matter of time. In this method,
a genetic algorithm (GA) searches for points where the gradient changes and dynamic programing (DP) designs the longitudinal
slope. This method can be applied to the ground heights of an actual forest road. The evaluation function of the DP assesses
the total expenditure. The inverse of this function is the fitness function. Crossover and mutation are operators of an evolution
simulation of a GA. They are each repeated 20 times and 420 profiles are designed and assessed, all within about 10 min. A
comparison of the profile designed by the GA with that of an actual forest road shows only one section where the formation
level differed substantially. Overall, both profiles seem to show a high degree of correspondence. From this result, we believe
that the profile designed by the GA is best, or the one of the best. A conventional method takes about 65 h to calculate all
changing points of gradients. However, by using the GA, the calculation time was reduced to about 1/389 that of the coventional
method, showing that the method which uses the GA through the profile design is very useful. 相似文献
6.
Summary A light microscopic (LM) visual technique to determine the polyethylenimine (PEI) distribution in a wood-PEI composite was studied by the adsorption of acid red or the circulation of Cu(II) ion with PEI in the composite. The amount of the adsorbed dye or Cu(II) on the composite increased linearly with an increase in the PEI content of the wood-PEI. The dyed composites were observed with LM under monochromatic light, corresponding to their absorption maxima at 560 nm for acid red and at 640 nm for copper chelate. The microscopic image was photographically recorded and the negative was subjected to densitometric analysis. At a polymer content lower than 4% in the composite, about 70% of total polymer was located in the middle lamella region, leaving only 30% in the secondary wall. With increasing PEI content of the composite, the concentration in the secondary wall increased, and about 80% of the polymer was located in the secondary wall at a PEI content of 27%. There were no noticeable differences between the amount of polymer detected by dyeing with acid red and by chelating with Cu(II). From the results of the line analysis of the intensity of the characteristic X-ray of uranium, the distribution of the PEI in the cell wall agreed closely with that determined by the LM method. It was concluded that the LM visual technique to determine the PEI location in the wood-PEI composite by dyeing with acid red or by chelating with Cu(II) is a simple and reliable method. 相似文献
7.
Isao Sawaguchi Shunji Shimizu Kouichi Ichihara Katsumi Toyokawa Osamu Ohkawabata 《Journal of Forest Research》1997,2(1):15-19
The growing condition of afforestation trees and damage to lower-story trees caused by felling and hauling of upper-story
trees in a multi-storied forest in Peninsular Malaysia was surveyed. Seventy months have passed since the planting ofAcacia mangium upperstory trees, which have grown 233 m3/ha in volume. The growth ofShorea leprosula thirty-five months after planting of lower-story trees have reached 5.54 m in height. However, as the ratio of height to
basal diameter exceeds 100:1, trees are tapering to a considerable degree. A backhoe was installed in order to fell the upper-story
trees. From the results of logging, the damage ratio estimation of the lower-story trees was simulated by using the Monte
Carlo method. The damage ratio differed considerably depending on planting patterns, height of upper-story trees and felling
skills. The results of this survey proved that the felling and hauling of upper-story trees would be technically feasible
in the future, except when one row upper-story trees and one row lower-story trees method were employed. 相似文献
8.
The bark of Japanese cedar (Cryptomeria japonica D. Don) was heated in an N2 atmosphere at 300–900C for 3h to investigate the surface properties of the pyrolyzed residuces and their ability to remove trichloroethylene (TCE) from aqueous solutions. The specific surface areas (S
N) and total pore volumes (V
N) of the pyrolyzed barks steadily increased with rising pyrolysis temperature; no significant differences in the average pore diameters (D
N) were observed at higher temperatures (600–900C). The adsorption capacities of the pyrolyzed residues for TCE were determined under batch mode conditions using an aqueous solution containing 500g TCE dm–3. The adsorption data were well fitted to the Freundlich equation. The adsorption capacity of the bark pyrolyzed at 900C was about five times larger than that of commercial activated carbon.This study was presented at the 10th International Symposium on Wood and Pulping Chemistry, Yokohama, June 1999 相似文献
9.
This paper presents a probabilistic method of evaluating the final moisture content (MC) of lumber obtained at the end of the kiln-drying process. The final MC data of three different drying tests conducted in past studies were analyzed using the bootstrap method. Target MC was tentatively set below 20 % in the analysis. Two characteristic parameters representing the final MC were estimated with bootstrap confidence intervals. These parameters were the standard deviation (SD) and the percentage of the population that met the MC requirement of less than 20 % (P 20). The histograms of the final MC and the subsequent goodness-of-fit tests revealed that the final MC data of two drying tests did not follow any classical probability distributions, including Normal, Log-Normal, Weibull, and Gamma distributions, thus indicating the need for nonparametric statistics. The uncertainty of the final MC could be evaluated with the estimated SD and P 20. After deriving the relationships between P 20 and the corresponding probability that P 20 is not achieved, we demonstrated how such relationships could provide a kiln operator with information to facilitate better decision-making in optimizing a drying schedule. 相似文献
10.
Shuichi Doi Masakazu Aoyama Shigeru Yamauchi Yasuji Kurimoto 《Journal of Wood Science》2005,51(5):526-530
We investigated the effects of high-temperature drying schedules (120°–130°C) on decay and termite feeding of Japanese larch
timbers. Thermogravimetric analysis was conducted to investigate changes of the wood components. Decay and termite feeding
tests showed that specimens dried under high-temperature schedules were susceptible against a decaying fungus Fomitopsis palustris and attacks from termites Coptotermes formosanus and Reticulitermes speratus. These drying schedules changed chemical components, which were suggested by the thermal analytical result compared to the
control sample. The results of this study indicated that the acceleration of termite feeding takes place even under temperatures
that are comparatively lower than that used in our previous research in which 170°C steaming treatment was applied to Japanese
larch wood. Decay durability against a brown rot fungus also decreased, possibly from production of low molecular weight fragments
when hemicellulose decreased during the high-temperature drying processes. 相似文献