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   69篇
  免费   11篇
林业   6篇
农学   9篇
  19篇
综合类   1篇
农作物   9篇
水产渔业   2篇
畜牧兽医   24篇
园艺   3篇
植物保护   7篇
  2021年   2篇
  2019年   4篇
  2018年   7篇
  2017年   9篇
  2016年   5篇
  2015年   4篇
  2014年   3篇
  2013年   5篇
  2012年   9篇
  2011年   8篇
  2010年   2篇
  2009年   1篇
  2008年   2篇
  2007年   6篇
  2006年   3篇
  2005年   1篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  1998年   2篇
  1997年   1篇
  1985年   2篇
排序方式: 共有80条查询结果,搜索用时 15 毫秒
1.
The direct effects of alpha- and beta-adrenergic agents on PRL and beta-endorphin (beta-END) secretion in vitro by porcine pituitary cells have been investigated. Pituitary glands were obtained from mature gilts, which were ovariectomised (OVX) one month before slaughter. Ovariectomised gilts, assigned to four groups, were primed with: (1) vehicle (OVX); (2) and (3) oestradiol benzoate (EB; 2.5 mg/100 kg b.w.) at 30-36 h (OVX+EB I) and 60-66 h (OVX+EB II) before slaughter, respectively; and (4) progesterone (P4; 120 mg/100 kg b.w.) for 5 consecutive days before slaughter (OVX+P4). Isolated anterior pituitary cells were submitted to 3.5 h incubation in the presence of GnRH, alpha- and beta-adrenergic agonists [phenylephrine (PHEN) and isoproterenol (ISOP), respectively], or alpha- and beta-adrenergic blockers [phentolamine (PHENT) and propranolol (PROP), respectively]. The culture media were assayed for PRL (exp. I) and beta-endorphin-like immunoreactivity (beta-END-LI) (experiment II). In experiment I, GnRH did not influence PRL release by pituitary cells in all experimental groups. Some of tested doses of adrenergic agonists, PHEN and ISOP, increased PRL release from pituitary cells of OVX gilts, but not from those of OVX+EB I animals. In the OVX+EB II group, PHEN alone, but ISOP with PROP, potentiated PRL secretion by the cells. In OVX+P4 animals, PHEN alone or in combination with PHENT and also ISOP alone or with PROP enhanced PRL output from the cells. In experiment II, addition of GnRH increased beta-END-LI release from pituitary cells only in the OVX+EB II group. PHEN and PHENT potentiated beta-END-LI secretion by pituitary cells in OVX+EB II and OVX+P4 groups, while ISOP and PROP increased beta-END-LI secretion by the cells of OVX and OVX+EB II animals. In turn, in the OVX+EB I group, effect of PHENT and PROP on PRL secretion by pituitary cells was inhibitory. In conclusion, our results suggest that adrenergic agents can modulate PRL and beta-END secretion by porcine pituitary cells in a manner dependent on the hormonal status of gilts.  相似文献   
2.
3.
The objective of this study was to assess the effect of relaxing massage on the heart rate (HR) and heart rate variability (HRV) in young racehorses during their first racing season. In the study, 72 Purebred Arabian racehorses were included. The study was implemented during the full race season. The horses from control and experimental groups were included in regular race training 6 days a week. The horses from the experimental group were additionally subject to the relaxing massage 3 days a week during the whole study. HR and HRV were assumed as indicators of the emotional state of the horses. The measurements were taken six times, every 4‐5 weeks. The HRV parameters were measured at rest, during grooming and saddling the horse and during warm‐up walking under a rider. The changes of the parameters throughout the season suggest that the relaxing massage may be effectively used to make the racehorses more relaxed and calm. Moreover, the horses from the experimental group had better race performance records.  相似文献   
4.
The effects of two polyphenolic flavonoids (flavanone naringenin and flavonol quercetin) on development, fecundity, and mortality of the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), were determined in vitro, on an artificial diets. Also determined in vitro (DC EPG method), on sucrose–agarose gels, were the effects of flavonoids on the probing and feeding behavior of adult apterae. When added to a liquid diet, higher concentrations of studied flavonoids increased the developmental time, the pre-reproductive period, and mortality and decreased fecundity and the intrinsic rate of natural increase of A. pisum. In most events associated with stylet activity (as indicated by EPG waveform g-C), differences in probing behavior did not statistically differ between the control gel and those with flavonoids; quercetin at 10, 100, and 1,000 µg cm?3 prolonged the number of gel penetrations; and quercetin only at 10,000 μg cm?3 prolonged the time the first g-C waveform was observed. Addition of flavonoids to the gels generally reduced passive ingestion from fluids of the gels (EPG waveform g-E2). At higher concentrations (>1,000 µg cm?3) the flavonoids completely stopped salivation (EPG waveform g-E1) and passive ingestion from fluids of the gels (EPG waveform g-E2). In events associated with active ingestion (EPG waveform g-G), however, differences in feeding behavior did not statistically differ between the control gel and those with flavonoids. The present findings demonstrate detrimental effects of the flavanone naringenin and flavonol on the behavior of the pea aphid. This can be employed in a biotechnological projects for plant breeding resistant to herbivores, including aphids.  相似文献   
5.
The tillage system, which joins soil tillage, fertilisation, and seed sowing in one pass of a machine, is rarely used in cereal cultivation. This research aimed to study whether strip-till and conventional tillage (post-harvest ripping and mixing of stubble, ploughing, pre-sowing fertilisation, and seedbed preparation) differ in plant density, yield components, and grain yield of winter barley cultivated on Cambisol in a region with low rainfall, the annual average is about 500?mm. To reach this aim, a two-year, large-plot experiment was conducted in a production field. The soil within the field was spatially variable in texture, moisture, and chemical and biological properties, CV 2.3% do 29.6%. Strip-till had lower within-field spatial variability of winter barley grain yield than conventional tillage. The standard deviation was 0.36?t?ha?1, 0.67?t?ha?1 in the first year and 0.12?t?ha?1, 0.30?t?ha?1 in the second year, respectively. During the period of limited rainfall, strip-till had greater uniformity of plants after emergence; after the winter with low air temperature and a low amount of snow, it had greater plant density. Thus, strip-till can reduce variability of plants and their yield within a field, especially in adverse environmental conditions.  相似文献   
6.
The PPR‐B gene is responsible for male‐fertility restoration of the Ogura‐type male‐sterile radish plants, and it is located in the complex Rfo locus in the vicinity of similar PPR‐A gene and PPR‐C pseudogene. The aim of this study was to identify PPR‐B alleles and understand the structure of the Rfo locus in radish breeding lines. Five lines of radish with normal male‐fertile cytoplasm were tested. The entire PPR‐B gene was amplified, sequenced and allelic PPR‐B sequences were identified. The results indicated that the maintainer lines 7, 15 and 21 contained a non‐restoring form of PPR‐B protein. A unique PPR‐B was found in lines 24/15 and 31 that are restorer and maintainer lines, respectively. The substitutions might be responsible for the loss of a restoring function of the PPR‐B‐31 allele. Amplification of the PPR‐A/PPR‐B and PPR‐B/PPR‐C intergenic regions allowed to identify rearrangements within Rfo locus. Obtained results confirm the wide allelic variation within the Rfo locus, as well as high genetic complexity of the fertility restoration mechanism in radish.  相似文献   
7.
8.
The nuclear male sterility gene ms8 is expected to facilitate the production of sweet pepper (Capsicum annuum L.) hybrids as it provides means for hybridization without the labor-intensive hand emasculation of female inbred lines. The development of molecular markers linked to ms8 locus will help the breeding practice for the selection of hybrid parental lines. In this study, F2 population resulting from a cross between the sweet pepper male sterile line 320 and the male fertile variety Elf was used to identify DNA markers linked to the ms8 locus. With the use of RAPD–BSA technique, seven markers linked to the ms8 locus were found. Four of them were converted into SCAR markers. In addition, two COSII/CAPS markers linked to the ms8 locus were identified. Comparative mapping with reference pepper maps indicated that the ms8 locus is located on the lower arm of the pepper chromosome P4. Identified markers are useful for molecular breeding, however, at present markers tightly linked to ms8 locus are still lacking. Identification of molecular markers linked to the ms8 locus and determination of its chromosomal localization are useful for fine mapping and also provide the perspective for ms8 gene cloning.  相似文献   
9.
Starting from (R)-(+)- and (S)-(-)-pulegone, enantiomeric pairs of esters and lactones with the p-menthane system were obtained. The Claisen rearrangement of allylic alcohols and iodolactonization of gamma,delta-unsaturated acids were the key steps of syntheses presented. The structures of compounds were determined by both spectroscopic and crystallographic methods. Some of the synthesized compounds are characterized by interesting odoriferous properties.  相似文献   
10.
Selected primitive and modern wheat species were evaluated on the basis of their carotenoid composition and effects of the genotype and environment on lutein using spectrometry and liquid chromatography. Carotenoids in the wheat extracts were identified and confirmed on the basis of their UV/vis and mass spectra compared with those of authentic standards. The protonated molecule (M + 1)+ at m/z 569 was the predominant ion for zeaxanthin compared to the fragment ion at m/z 551 for lutein. A similar carotenoid profile was obtained for the wheat species investigated, but significant differences were observed in the concentration of carotenoids. Einkorn (Triticum monococcum) exhibited the highest level of all-trans-lutein, averaging 7.41 microg/g with small amounts of all-trans-zeaxanthin, cis-lutein isomers, and beta-carotene. Durum, Kamut, and Khorasan (Triticum turgidum) had intermediate levels of lutein (5.41-5.77 microg/g), while common bread or pastry wheat (Triticum aestivum) had the lowest content (2.01-2.11 microg/g). Lutein in einkorn appeared to be influenced significantly by environmental growing conditions.  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