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   83篇
  免费   10篇
林业   9篇
农学   3篇
基础科学   1篇
  11篇
综合类   3篇
农作物   13篇
水产渔业   17篇
畜牧兽医   23篇
园艺   4篇
植物保护   9篇
  2022年   2篇
  2021年   4篇
  2020年   3篇
  2019年   4篇
  2018年   8篇
  2017年   7篇
  2016年   7篇
  2015年   6篇
  2014年   14篇
  2013年   13篇
  2012年   10篇
  2011年   7篇
  2010年   2篇
  2009年   3篇
  2008年   2篇
  1997年   1篇
排序方式: 共有93条查询结果,搜索用时 46 毫秒
41.
The study was conducted to evaluate the effects of α ‐linolenic acid (ALA) on frozen–thawed quality and fatty acid composition of bull sperm. For that, twenty‐four ejaculates obtained from three bulls were diluted in a Tris extender containing 0 (control), 3, 5, 10 and 15 ng/ml of ALA. Extended semen was incubated at 37°C for 15 min, to allow absorption of ALA by sperm cell membrane. The sample was chilled for 2 h, packed into 0.25‐ml straws and frozen in liquid nitrogen for 24 h. Subsequently, straws were thawed and evaluated for total sperm motility (computer‐assisted semen analysis), membrane functional integrity (hypo‐osmotic swelling test), viability (eosin‐nigrosin), fatty acid composition (gas chromatography) and lipid peroxidation (thiobarbituric acid‐reactive substances (TBARS)). A higher (p < 0.05) percentage of total sperm motility was observed in ALA groups 5 ng/ml (47.74 ± 07) and 10 ng/ml (44.90 ± 0.7) in comparison with control (34.53 ± 3.0), 3 ng/ml (34.40 ± 2.6) and 15 ng/ml (34.60 ± 2.9). Still, the 5 ng/ml ALA group presented a higher (p < 0.05) percentage of viable sperms (74.13 ± 0.8) and sperms with intact membrane (74.46 ± 09) than all other experimental groups. ALA concentration and lipid peroxidation in post‐thawed sperm was higher in all treated groups when compared to the control group. As such, the addition of 5 ng/ml of ALA to Tris extender improved quality of frozen–thawed bull spermatozoa.  相似文献   
42.
The study appraised the effects of Carotino oil on in vitro rumen fermentation, gas production, metabolism and apparent biohydrogenation of oleic, linoleic and linolenic acids. Carotino oil was added to a basal diet (50% concentrate and 50% oil palm frond) at the rate of 0, 2, 4, 6 and 8% dry matter of the diet. Rumen inoculum was obtained from three fistulated Boer bucks and incubated with 200 mg of each treatment for 24 h at 39°C. Gas production, fermentation kinetics, in vitro organic matter digestibility (IVOMD), volatile fatty acids (VFA), in vitro dry matter digestibility (IVDMD), metabolizable energy and free fatty acids were determined. Carotino oil did not affect (P > 0.05) gas production, metabolizable energy, pH, IVOMD, IVDMD, methane, total and individual VFAs. However, Carotino oil decreased (P < 0.05) the biohydrogenation of linoleic and linolenic acids but enhanced (P < 0.05) the biohydrogenation of oleic acid. After 24 h incubation, the concentrations of stearic, palmitic, pentadecanoic, myristic, myristoleic and lauric acids decreased (P < 0.05) while the concentration of linolenic, linoleic, oleic and transvaccenic acids and conjugated linoleic acid (CLAc9t11) increased (P < 0.05) with increasing levels of Carotino oil. Carotino oil seems to enhance the accumulation of beneficial unsaturated fatty acids without disrupting rumen fermentation.  相似文献   
43.
Ultrasonic wave timing inspection was used to detect the internal decay in standing Iranian beech trees (Fagus orientalis). To evaluate the influence of internal decay on ultrasonic velocity, healthy round sections of freshly cut fallen beech trees were selected. Holes [as heart or internal decay indicator and with different shapes (circular and slot) and locations] were manually created and progressively enlarged in the wood section disks, and ultrasonic wave velocity was measured by using a commercial ultrasonic tester (Sylvatest Duo). The results showed that ultrasonic wave velocity linearly and significantly decreased by increasing hole dimensions, and location of holes had no influence on the extent and trend of velocity decrease. Although slots covered a small volume fraction of disks, they had a greater effect on ultrasonic velocities reduction as compared with circular holes.  相似文献   
44.
This study was carried out to evaluate the antioxidative potential and quality of the meat of African catfish fed mulberry foliage extract (MFE). A total of 360 juvenile African catfish (8.4 ± 0.2 g) were fed four diets namely, basal diet (control), MFE‐2 (2 g MFE kg?1), MFE‐5 (5 g MFE kg?1) and MFE‐7 (7 g MFE kg?1) for 60 days. At the end of the experiment, muscles were excised, vacuum‐packaged and conditioned for 0, 7 and 14 days in a chiller (4°C). The meat from fish fed MFE‐5 and MFE‐7 had significantly (P < 0.05) greater total phenols content than the other dietary groups. This value reduced (P < 0.05) during storage. The DPPH‐scavenging effect of MFE‐7 increased (P < 0.05) compared with the others. It decreased (P < 0.05) during storage. The lowest POV was revealed (P < 0.05) in MFE‐7. The 2‐thiobarbituric acid‐reactive substances (TBARS) and peroxide value (POV) increased (P < 0.05) during storage. The pH value was significantly (P < 0.05) higher in MFE supplemented diets than in the control group. It is concluded that MFE at the concentration of 7 g kg?1 DM is potential dietary antioxidant supplements, to improve the quality of fish meat.  相似文献   
45.
The objective of this experiment was to determine the effects of two levels of vitamin E (100 and 300 mg/kg diet) along with two levels of lipid (9 and 14%) and their interaction on growth performance of Indian white shrimp and consequently to evaluate the fatty acid composition and lipid stability of its muscle tissue during frozen storage. Growth of juvenile Indian white shrimp was not significantly affected by dietary vitamin E and lipid levels. Muscle lipid content of shrimp fed diets with 14% lipid was significantly higher than that of with 9% lipid. Obvious effects of the increase in dietary lipid level on muscle fatty acid composition were significant decrease in proportion of 16:0 and increase in proportion of 20:5n-3. The content of vitamin E concentration in shrimp muscle reflected dietary vitamin E concentration and ranged from 6.68 to 14.8 mg/kg muscle corresponding to two (100 and 300 mg/kg) levels of vitamin E in fish diet, respectively. Subsequently, results showed that by increasing the concentration of vitamin E from 100 to 300 mg/kg in diet, the rate of lipid oxidation in the muscle tissue during frozen storage was reduced and, as a result, caused higher HUFA retention in muscle of shrimp fed diet with high lipid level.  相似文献   
46.
Physical properties of horticultural products are important in designing the sorting, transporting, processing and packaging systems. Among physical attributes, dimensions, weight, volume, projected areas and porosity are useful for designing grading systems. This study carried out on four superior walnut (Juglands regia) genotypes, which were selected from primary morphological screening of 608 genotypes in Neyriz city, Iran. G-570 with higher nut weight (12.46 g), kernel weight (8.25 g) and kernel ratio of 66.21% was a promising genotype among others. Regarding studied physical properties, G-570 was 44 mm in diameter significantly different from other genotype. In this research walnut mass was predicted by using different physical properties with linear and nonlinear models as three classifications (dimension, projected areas and volume). Results showed that the highest correlation was between models number three, two and one. Among grading system based on dimensions in walnut (first classification), minor diameter model with nonlinear relation was the best and could be considered as a good model for economical and horticultural designing systems.  相似文献   
47.
Kutum Rutilus frisii kutum is known as a valuable commercial species in the southern part of Caspian Sea. Artificial rearing of fry has been introduced as an alternative to supply kutum fry in order to restock the kutum population in the Caspian Sea. The aim of this study was to find the suitable time to transfer kutum larvae from live food to artificial feed. The experiment began on day 3 post- hatching and lasted for 21 days. Mean initial weight of larvae was 4.5 mg. Five experimental groups including Group A (zooplankton alone for 21 days), Group B (12 days zooplankton + 9 days artificial feed), Group C (8 days zooplankton + 13 days artificial feed), Group D (4 days zooplankton + 17 days artificial feed) and Group E (artificial feed alone for 21 days) were considered for this experiment. According to the obtained results, the specific growth rate of kutum larvae varied from 8.01 to 13.58% day−1, and the highest and lowest specific growth rate were found in A and E treatments, respectively. The lowest mean body weight (24.6 mg) was found in larvae fed on artificial feed for 21 days. However, survival rates of kutum larvae fed mixed zooplankton for 8 and 12 days (85.83 and 89.33%, respectively) were comparable with those of larvae fed live food during the entire experiment (91.6%). The lowest survival rate (69.16%) was found in larvae fed artificial feed during the entire experiment.  相似文献   
48.
The effects of different inclusion levels of oil palm fronds (OPF) on the fatty acid profile of the longissimus dorsi (LD), biceps femoris (BF) and infraspinatus (IS) muscle of goats fed for 100 days are described. Twenty‐four individually housed Kacang crossbred male goats (averaged 21.7 ± 0.97 kg BW) were allocated to three groups receiving either a 100% concentrate control diet (CON), diet with 25% inclusion level of OPF (HAF) or a diet with 50% inclusion of OPF. The diets were adjusted to be isocaloric and isonitrogenous and fed at 3.0% of BW daily. Samples of LD, BF and IS muscles were taken at slaughter for the determination of fatty acid profiles. The total saturated fatty acids (SFA) in the LD and BF muscles of the OPF group were significantly (p < 0.05) lower than the CON group. For all muscles, C18:3n‐3 and total n‐3 polyunsaturated fatty acid (PUFA) were significantly higher (p < 0.05) in the OPF group than the CON group with minimal impact on the C18:2n‐6 and total n‐6PUFA. Consequently, the n‐6:n‐3 ratio significantly (p < 0.05) decreased in the OPF group compared to the CON group. The LD muscle had a significantly higher conjugated linoleic acid 18:2 c19t11 compared to other muscles. There were no interactions between muscle x diet except for total SFA. It is concluded that OPF at 25–50% inclusion levels may decrease the SFA and increase the n‐3PUFA content in chevon, with no apparent adverse effects on the growth performance of the animals, can be used as a feed ingredient to support goat farming in countries that lack grazing pasture.  相似文献   
49.
The present article was conducted to evaluate the effect of in ovo injection of arginine on hatchability, immune system and caecum microflora of broiler chickens. For this reason, 300 fertile eggs were used in a completely randomized design with three experimental treatments. The experimental groups included: 1%–0.5% l -arginine (100 eggs), 2%–1% l -arginine (100 eggs), 3- control [included both sham control (injection of distilled water; 50 eggs) and control (no injection; 50 eggs)], which were injected on d 14 of incubation. After hatching, chicks of each experimental group (0.5% l -arginine, 1% l -arginine, and control groups) were randomly divided into four equal groups (as replicates) and reared for 30 days. Weight and feeding of chickens were recorded. Next, blood samples of chickens were collected on day 30 to evaluate antibody titre. Also, chickens were slaughtered on 24 and 30 days of the experiment to evaluate immune system organs and caecum microflora. Based on the results, in ovo injection of l -arginine had no significant effect on hatchability, body weight, antibody titre, spleen, bursa of Fabricius and thymus weight (p > .05). On the other hand, treatments significantly affected feed intake and feed conversion ratio (p < .05). As a novel finding, in ovo injection of l -arginine increased caecal Lactobacillus (p < .01), while decreasing Coliform and Escherichia Coli bacteria (p < .01). However, treatments did not influence caecal Enterococcus (p > .05). The overall results indicated that in ovo injection of 0.5% l -arginine had a better improving effect on caecal microflora and then considered as a recommended level of the present experiment.  相似文献   
50.
The aim of this study was evaluation of survivability, maturation rate and apoptotic gene expression of preantral follicles after vitrification and slow freezing technique. Normal mouse preantral follicles were randomly divided into three experimental groups. In the control group, follicles were cultured immediately; in the vitrification and slow freezing groups, follicles were cultured after vitrification‐warming and slow freezing‐thawing procedures. Follicular viability was assessed by using 0.4% trypan blue, and molecular evaluation of messenger RNA levels of apoptosis‐related genes was performed by the semi‐quantitative RT‐PCR method after 3 h of culture. Oocyte maturation rates were also evaluated on day 14 of culture. Survival and maturation rate in the slow freezing group were significantly lower than those in control and vitrification groups (P ≤ 0.05). Although there was no difference in Survivin expression among the three experimental groups, Bcl‐2 expression was significantly lower in the slow freezing group compared to the other groups (P ≤ 0.05). The expression of Bax, P53, Fas and Bax/Bcl2 ratio in the slow freezing group was significantly higher than control and vitrification groups (P ≤ 0.05). Preantral follicle vitrification seems to be better than slow freezing as seen in the survival, maturation and expression rates of apoptotic gene variants.  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