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   141篇
  免费   8篇
林业   4篇
农学   17篇
基础科学   2篇
  39篇
农作物   37篇
水产渔业   17篇
畜牧兽医   21篇
园艺   4篇
植物保护   8篇
  2023年   2篇
  2022年   5篇
  2021年   7篇
  2020年   10篇
  2019年   14篇
  2018年   11篇
  2017年   14篇
  2016年   15篇
  2015年   6篇
  2014年   8篇
  2013年   23篇
  2012年   6篇
  2011年   7篇
  2010年   2篇
  2009年   6篇
  2008年   2篇
  2007年   3篇
  2005年   3篇
  2003年   2篇
  2002年   1篇
  2001年   1篇
  1992年   1篇
排序方式: 共有149条查询结果,搜索用时 31 毫秒
61.
Dysplastic features of erythroid and megakaryocytic lineages were observed in a cat with acute erythroid leukemia. We demonstrated that flow cytometry analysis of the expression of glycophorin A and CD71 by neoplastic cells can be helpful in the diagnosis of this type of feline leukemia.  相似文献   
62.
This study evaluated the effects of diets containing 20, 40, 60, 80 and 100 mg kg?1 diet astaxanthin or canthaxanthin on Pethia conchonius (Hamilton, 1822) pigmentation. A completely randomized experimental design was developed with ten treatments and three replicates. Three hundred rosy barb with a mean weight of 0.92 ± 0.06 g were assigned to thirty aquaria for period of eight weeks. Carotenoid contents of fish fed canthaxanthin were always lower than those fed astaxanthin. Yellowness (b*) was not affected by pigments. While Luminosity (L*) decreased in fish fed astaxanthin diets, this parameter increased by feeding on canthaxanthin. The most pronounced effect was higher a* values in fish fed astaxanthin. Astaxanthin retention rate was higher than that of canthaxanthin. The present results demonstrate that canthaxanthin cannot be considered as a proper replacement with astaxanthin. Inclusion of 80 and 100 mg astaxanthin kg?1 diet can be suitable dietary levels to ensure pigmentation and this condition may improve market value of rosy barb.  相似文献   
63.
Sheep have been used as translational models of human postnatal testicular development. However, the morphometric features of the normal developing testis in sheep embryos have not been previously investigated using stereology. The objective of the present work was to establish normal quantitative parameters for fetal testicular tissue components in sheep, using unbiased design-based stereological methods. Twenty-four sheep embryos were divided into four gestational age groups (9–11, 12–14, 15–17 and 18–20 weeks of gestation) on the basis of the embryos’ crown-rump length. Isotropic, systematic uniform random sections of the left testes were obtained by employing the orientator method. Testicular total volume, the absolute and proportional volumes occupied by the seminiferous tubules and interstitial tissue, as well as the seminiferous tubule length, were estimated using the point-counting system and the unbiased counting frame principle. All the parameters, with the exception of the interstitial tissue's fractional volume, gradually increased along with gestational age, with the maximum increase especially seen in the late fetal stages. The proportional volume of the interstitial tissue, on the other hand, showed a decreasing trend along with increasing gestational age. The absolute volume of the testes, of the seminiferous tubules and of the interstitial tissue, and the length of the seminiferous tubules showed a significant (p< 0.05) positive linear correlation with gestational age. Several similarities were observed with human testicular embryogenesis. The stereological data emerging from the present study might prove useful as basic contribution to the fields of andrology and embryology and stimulate further research in these areas.  相似文献   
64.
65.
66.
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   
67.
Fisheries Science - Illipe Shorea macrophylla is a riverine fruit naturally eaten by Malaysian mahseer Tor tambroides and other riverine cyprinids. The effects of crude illipe oil on the growth...  相似文献   
68.
Despite efforts made, forage yield of smooth bromegrass has increased slowly over the last 50 years of breeding. It therefore seems necessary to investigate more on the genetic basis of agro-morphological traits in this cool-season, highly drought resistant grass. The present study was aimed at estimation of total genetic variance, narrow-sense heritability, general combining ability, phenotypic and genotypic correlation among different quantitative traits in half-sib (HS) families derived from polycross of 25 smooth bromegrass genotypes that were mainly originated from Iran. Families differed significantly for all of the agro-morphological and quality traits measured. Narrow sense heritability ( ${\text{h}}_{\text{n}}^{2}$ ) ranged from about 0.2 (plant height) to 0.7 (day to inflorescence emergence and day to anthesis). Moderate to high heritability for forage dry matter yield (0.42) indicates that phenotypic selection for this trait can be successful. A wide range of general combining ability was observed for most of the studied traits, especially those related to forage yield. Relatively low genetic variation and heritability for crude protein and also negative correlation of this trait with forage yield, indicates a low probability of improving forage yield and quality simultaneously.  相似文献   
69.
The improvement of sugar-related factors is associated with root traits in sugar beet. The objectives of the present study were to assess variations of sugar- and root yield (RY)-related traits and to estimate general (GCA) and specific (SCA) combining abilities of several lines, testers and hybrids under various environmental conditions. A line × tester mating design was used to develop 28 hybrids from seven lines × four testers. Presently, root- and sugar-related traits were recorded in parental lines, hybrids and five local ('Pars', 'Torbat' and 'Ekbatan') and international ('Kermit' and 'Tous') check varieties in the eight combinations of location and growing season. Mean RY and sugar yield (SY) were 44.81 t/ha and 7.57 t/ha, respectively. Genotypes tested had 16.91% sugar content (SC) and 13.64% white sugar content (WSC) across trials. No one genotype was found to have high levels for all traits, but several had above mean sugar-related or RY traits. L7T2 as the best hybrid for RY and SY yielded 37.0% and 34.4% more than the checks’ mean, whereas ratios for the best hybrid (L7T4) for SC and WSC were 8.2% and 4.3%, respectively. Additive variance was significant for all traits, whereas dominance component was only significant for RY. Several parental lines had stable GCA effects with respect to direction and magnitude for WSC, RY and SC in environments. L7 and T2 for RY and SY and L3 and T4 for SC and WSC were identified as the best combiners with high GCA effects, and their use might increase favourable alleles in further breeding programmes for traits tested. Estimated heritability for the combined environments was lower for sugar-related traits (54.01%–59.39%) compared with those for RY traits (73.68%–74.21%). Overall, given heritability and additive variances estimated the identification of environmentally stable GCA and SCA effects and might help to increase efficiency of selection of superior cultivars with respect to sugar traits.  相似文献   
70.
To study the genetic variation, heritability and genetic correlations of some agro-morphological traits in tall fescue, 25 parents from a genetically broad-base germplasm were polycrossed and their respective half-sib families were generated. Clonally propagated parents and their half-sib families were grown as spaced single plants using a randomized complete-block design with three replications, and observed for seven traits in 2006 and 2007. The estimates of broad-sense heritability were moderate to high for the traits studied. Narrow-sense heritability estimates from analyses of progenies and from regression of half-sib (HS) progenies on parents suggested that genetic variation for these traits was largely controlled by additive gene action. Association of dry matter yield (DMY) with plant height, number of fertile shoot, curbs width and spring growth was positive and significant. With the exception of number of days to pollination, correlation coefficients of the traits between the parents and offspring were not significant. Based on parent-offspring regression, genetic gain from selection for DMY was high, demonstrating genetic potential for improving this trait. Overall, there was high genetic variation and moderate heritability for most traits in the tall fescue populations evaluated. In conclusion, to improve herbage yield, selection would be more effective based on forage yield components.  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