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   67篇
  免费   3篇
  6篇
综合类   6篇
农作物   2篇
水产渔业   4篇
畜牧兽医   42篇
园艺   1篇
植物保护   9篇
  2022年   1篇
  2021年   1篇
  2018年   1篇
  2017年   2篇
  2016年   2篇
  2015年   1篇
  2012年   2篇
  2011年   3篇
  2010年   3篇
  2009年   8篇
  2008年   3篇
  2007年   4篇
  2006年   1篇
  2005年   2篇
  2003年   2篇
  2002年   5篇
  2001年   1篇
  2000年   3篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   3篇
  1994年   1篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1987年   2篇
  1978年   1篇
  1972年   2篇
  1964年   2篇
  1959年   1篇
  1957年   4篇
排序方式: 共有70条查询结果,搜索用时 15 毫秒
21.
Three 0.01m Fe(ClO4)3 Solutions of R= 0, 1, and 2, respectively, were studied over a period of 8 months, where R is referred to the HCO3?/Fe3+ mole ratio in preparation. The R= 0 solution was initially light yellow and clear but rapidly changed to a dense cloudy Suspension after a 9-day induction period. Hydrolysed species rapidly grew from <10 nm to >650 nm. Particles of intermediate size were not observed during the entire period of study. Settleable FeOOH precipi-tate was first observed in 5 weeks with 23 per cent of its iron noted as precipitate at the end of 5 months. The R= 1 and R= 2 Solutions were reddish-brown of low turbidity. Rapid hydrolysis and polymerization were observed immediately after preparation. The hydrolysed species gradually grew in size during ageing and no settleable FeOOH precipitate was observed for at least two years. A hypo-thesis based on Lamb and Jacques's model of Fe3+ hydrolysis is proposed to interpret the reactions taking place in these three Solutions. In the R= 0 solution, the initial number of nuclei for condensation is low, whereas the poten-tial supply of Fe(OH)3 is abundant. In the R= 1 and R= 2 Solutions the number of nuclei initially formed is high, whereas a limited amount of mono-meric Fe(OH)3 is available for condensation. The initial number of nuclei relative to the concentration of monomeric species is the key factor that governs the appearance and properties of these Solutions.  相似文献   
22.
 为明确一种新的香蕉(Musa sapientum)细菌性叶斑病病原菌,以云南省新平县香蕉园区发现的一种新病害为供试材料,通过分离培养、形态观察、致病性测定、生理生化试验和gyrB,16S rDNA 和 rpoB基因片段分析,对病原菌进行了鉴定。该病由克雷伯氏肺炎球菌肺炎亚种(Klebsiella pneumoniae subsp. pneumoniae)引起,病菌可侵染香蕉叶片、假茎和果实。茎干被病原菌侵入3 d后即可出现黑色小斑点,在接种部位附近呈上下方向蔓延趋势,7 d后茎干上出现大面积棕色坏死,内部组织褐变。本文在世界上首次报道克雷伯氏肺炎球菌肺炎亚种可侵染香蕉植株,引起香蕉细菌性叶斑病。  相似文献   
23.
 华丽腐霉Pythium splendens是我国对外植物检疫对象油棕苗疫病的病原菌,从海南坝王岭自然保护区长臂猿原始林区采集的土样中分离出1株腐霉菌HB0401,经形态特征和核糖体rDNA ITS1序列分析鉴定为华丽腐霉(Pythium splendens Braun)。将该菌株接到健康的油棕苗植株上,能引起典型的油棕苗疫病症状。这是第1次在海南分离到华丽腐霉(Py. splendens)并证实其为油棕苗的致病菌。  相似文献   
24.
The health safety of methylglyoxal (MGO) has been recognized as a key issue owing to its ultra-high reactivity toward some key biomolecules such as amino acids, proteins, DNA, sulfhydryl- and basic nitrogen-containing compounds, including amino-bearing neurotransmitters. In this review, we have summarized the endo- and exogenous sources of MGO and its accumulation inside the body due to high intake, abnormal glucose metabolism and or malfunctioning glyoxalases, and review the debate concerning the adverse functionality of MGO ingested from foods. Higher than normal concentrations of MGO in the circulatory system and tissues have been found to be closely associated with the production of advanced glycation end products (AGEs), increased oxidative stress, elevated inflammation and RAGE (AGE receptors) activity, which subsequently progresses to a pathological stage of human health, such as diabetes complications, cancer, cardiovascular and degenerative diseases. Having illustrated the mechanisms of MGO trapping in vivo, we advocate the development of efficient and efficacious MGO scavengers, either assisting or enhancing the activity of endogenous glyoxalases to facilitate MGO removal, or providing phytochemicals and functional foods containing them, or pharmaceuticals to irreversibly bind MGO and thus form MGO-complexes that are cleared from the body.  相似文献   
25.
26.
Autoantibodies against thyroxin (T4AA) and triiodothyronine (T3AA) are present in dogs with autoimmune thyroiditis and have been reported to interfere with immunoassays. The objectives of this study were to determine the frequency of autoantibodies and to determine whether interference occurs by T4AA, using a non-immunological method (high performance liquid chromatography, HPLC) for thyroxin (T4) measurement. Based on clinical symptoms, T4 and thyroid stimulating hormone (TSH) concentration, 1,339 dogs were divided into six groups: Group 1: hypothyroid (n = 149); Group 2: subclinical thyroiditis (n = 110); Group 3: suspicious for non thyroidal illness (n = 691); Group 4: biochemical euthyroid (n = 138); Group 5: hypothyroid dogs under substitution therapy (n = 141); Group 6: healthy dogs (n = 110). The incidence of T4AA and T3AA, determined using radiometric assay, was low (0.5% and 3.8%) and higher in hypothyroid dogs compared to dogs suspicious for hypothyroidism (Group 2-4) (p<0.05). T4AA was not detected in dogs with normal T4 and elevated TSH. T4 concentrations of T4AA positive samples determined using HPLC were comparable to results obtained by chemiluminescence immunoassay. These findings indicate that the probability of interference of T4AA leading to falsely elevated T4 concentration in the T4 assay seems to be low.  相似文献   
27.
Contents The aim of this study was to investigate the effect of sexual activity on concentrations of reproductive hormones in plasma of stallions. In the first experiment, two groups of stallions were monitored for secretion of luteinizing hormone (LH), testosterone and oestradiol from the beginning until shortly after the end of the breeding season. One group of animals were reserve stallions not used for breeding (group 1, n = 10), the other group consisted of active breeding sires (group 2, n = 8). Blood samples were withdrawn from March to August at 14-day intervals. In sexually nonactive stallions (group 1), seasonal variations in LH, testosterone and oestradiol occurred and concentrations of these hormones reached a maximum in May (p < 0.05). In the breeding stallions (group 2), no significant changes in the concentrations of these hormones were found between March and August. Concentrations of LH and testosterone were significantly lower in breeding stallions than in reserve stallions at most blood sampling times (p < 0.05). In the reserve stallions, oestradiol concentrations were significantly higher than in the breeding stallions in April and in June (p < 0.05). In a second experiment, the effect of regular sexual activity (semen collection three times per week) on the concentration of LH, testosterone and oestradiol was tested in a group of breeding stallions after a period of sexual rest for several weeks. Blood samples were taken once daily starting the day before the first semen collection was performed. Testosterone concentration significantly decreased in the first days after semen collection started (p < 0.05), while LH secretion was only transiently decreased and no effects on oestradiol concentration were found. In both experiments, semen parameters were within the normal range of fertile stallions. No correlations between the sexual drive of the stallions and concentration of reproductive hormones occurred. It can be concluded that in the stallion the secretion of reproductive hormones is influenced by sexual activity. Regular semen collection seems to inhibit testosterone release by unknown mechanisms while the effects on LH and oestradiol secretion are less pronounced.  相似文献   
28.
29.
Control of nematode parasites with reduced reliance on the use of anthelmintics was studied in 16 ewes with suckling twin lambs on contaminated pasture in Denmark. Ewes and lambs were treated with albendazole at turn-out 3 May. Ewes were removed from the groups on 26 July, and lambs were slaughtered on 11 October. The animals were allocated to 4 groups of 8 lambs and their 4 ewes. Group TS was treated with albendazole at weeks 3, 6 and 8 after turnout and set-stocked; group TM was similarly treated but moved to clean pasture in conjunction with the last drenching; group US was untreated and set-stocked, and group UM was left untreated but moved to clean pasture week 8 after turn-out. Supplementary feed was offered in June and August due to scarcity of pasture. Strategic treatments of ewes and lambs weeks 3, 6 and 8 after turn-out, with or without a move to clean pasture, were highly effective in controlling nematode infections for most of the season. This was reflected in better weight gains and carcass characteristics in the treated compared to untreated lambs, resulting in an average increase in the value of the product by 36%. The effect of moving without treatment (UM) on faecal egg counts was limited but peak pasture infectivity was reduced to less than 10% compared to the set-stocked group and weight gains of lambs were significantly better despite poor feed availability in late season. The study showed that under set-stocked conditions repeated anthelmintic treatments of both ewes and lambs in early season may ensure sufficient nematode control whereas moving animals to clean pasture without dosing was less efficient. The latter may, however, still be a viable option in organic and other production systems where routine use of anthelmintics is banned, particularly if weaning and moving are combined or a second move is performed.  相似文献   
30.
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