全文获取类型
收费全文 | 473篇 |
免费 | 10篇 |
国内免费 | 16篇 |
出版年
2023年 | 6篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 17篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 22篇 |
2005年 | 18篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 21篇 |
1998年 | 19篇 |
1997年 | 24篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 18篇 |
1991年 | 16篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有499条查询结果,搜索用时 15 毫秒
121.
Red cabbage is a source of health beneficial substances with antioxidant and antigenotoxic properties. HPLC analysis specifying
the content of the investigated extract indicated that mainly anthocyanins (ATH) were responsible for its abilities. Cytological
research was conducted with two experimental models: plant tissues—meristematic cells of Vicia faba, and animal tissue elements—human lymphocytes. Positive influence of ATH extract on mitotic activity of Vicia cells exposed to Cu2+ stress, and inhibitory effect of ATH on cytotoxic actions of Cu2+ on lymphocytes were demonstrated. In all experimental series with ATH application in combinations with Cu2+, mitotic index (MI) were higher than those obtained for only Cu2+ stressed tissues. Preincubation in ATH before Cu2+ stress had the best effect. Similarly, after ATH applications in all tested series decrease in frequency of micronuclei (MN)
appearance was noticed in comparison with only Cu2+ stressed material. In the case of Vicia cells ATH acted effectively even applied after Cu2+ stress. It suggests that this ATH mixture not only prevents and limits but also heals the cytological injury caused by Cu2+ stress. 相似文献
122.
Assimilate efflux from vacuum-infiltrated leaf slices (spinach, barley) into a buffered solution was examined in relation to Ca+ + -activity and osmotic conditions. Efflux from isolated mesophyll protoplasts and from a unicellular green alga (Eremosphaera viridis de Bary) was also measured.In the presence of Ca+ +, assimilate efflux from leaf slices was small (1 to 5 % of the total carbon fixation rate, depending on osmotic conditions). Efflux was drastically stimulated by addition of Ca+ + -chelators. If expressed as µmol carbon mg-1 chlorophyll h-1, it reached 50 % of the assimilation rate. Efflux from protoplasts or algae was slow and insensitive to Ca+ + chelators at concentrations which caused fast efflux from leaf slices.Assimilate efflux from leaf slices was rather unspecific. Both in the tissue and the surrounding medium, sucrose was the most abundantly labelled compound (70 to 80 % of total soluble labelled material).A 50 % decrease of efflux was observed when turgor pressure was lowered by addition of sorbitol (200 to 300 mosmol kg-1). At extremely high sorbitol concentrations (> 1500 mosmol kg-1) efflux increased again and was relatively less stimulated by EDTA.It is suggested that assimilate efflux from leaf slices is mainly diffusion through open veins and/or plasmodesmata. When these symplastic connections are closed by addition of Ca+ +, the remaining transmembrane flux into the apoplast is small. Thus, assimilate movement from the mesophyll to the phloem appears to be symplastic, not apoplastic as suggested in the literature. 相似文献
123.
124.
Koralewska A Posthumus FS Stuiver CE Buchner P Hawkesford MJ De Kok LJ 《Plant biology (Stuttgart, Germany)》2007,9(5):654-661
The uptake and distribution of sulfate in BRASSICA OLERACEA, a species characterised by its high sulfate content in root and shoot, are coordinated and adjusted to the sulfur requirement for growth, even at external sulfate concentrations close to the K (m) value of the high-affinity sulfate transporters. Plants were able to grow normally and maintain a high sulfur content when grown at 5 or 10 microM sulfate in the root environment. Abundance of mRNAs for the high affinity sulfate transporters, BolSultr1;1 and BolSultr1;2, were enhanced at 相似文献
125.
海水胁迫对菠菜叶绿素代谢的影响 总被引:2,自引:0,他引:2
以耐海水品种‘荷兰3号’和海水敏感品种‘圆叶菠菜’为试验材料,采用营养液栽培,研究海水胁迫对菠菜叶绿素代谢的影响。结果表明,海水胁迫下,2个菠菜品种叶片的叶绿素a(Chl a)、叶绿素b(Chl b)和总叶绿素含量以及叶绿素合成前体———原叶绿素酸(Pchl)、镁原卟啉IX(Mg-proto IX)、原卟啉IX(Proto IX)和尿卟啉原III(UroIII)含量均明显降低,而胆色素原(PBG)和δ-氨基酮戊酸(ALA)积累,‘圆叶菠菜’的变化幅度大于‘荷兰3号’。海水胁迫下,‘荷兰3号’叶片的叶绿素酶(Chlase)活性无显著变化,胆色素原脱氨酶(PBGD)和尿卟啉原III合酶(UROS)活性在胁迫第3天显著下降,而‘圆叶菠菜’Chlase活性显著上升,PBGD和UROS活性显著下降。研究发现,在海水胁迫条件下,菠菜叶片的叶绿素合成代谢受阻,受阻位点位于PBG→UroIII的转化过程,其中‘圆叶菠菜’的受阻程度大于‘荷兰3号’;耐海水品种‘荷兰3号’叶片叶绿素含量降低主要由叶绿素合成代谢受阻引起,而海水敏感品种‘圆叶菠菜’叶绿素含量的降低则是由叶绿素合成受阻和叶绿素降解共同作用的结果。 相似文献
126.
Changes in the conformation of spinach thylakoid membranes were monitored in 5-doxyl stearic acid (SAL)-treated thylakoid
membranes in the presence of various anions (Cl−, Br−, I−, NO2
−, SO4
2−, PO4
3−). The presence of anions made the thylakoid membrane more fluid. The extent of change in membrane fluidity differed with
different anion and was reversible. 相似文献
127.
BACKGROUND AND AIMS: Plant shoots form a sink for NH3, and are able to utilize it as a source of N. NH3 was used as a tool to investigate the interaction between foliar N uptake and root N uptake. To what extent NH3 can contribute to the N budget of the plant or can be regarded as a toxin, was investigated in relation to its concentration and the N supply in the root environment. METHODS: Brassica oleracea was exposed to 0, 4 and 8 microL L(-1) NH3, with and without nitrate in the nutrient solution. Growth, N compounds, nitrate uptake rate, soluble sugars and cations were measured. KEY RESULTS: In nitrate-sufficient plants, biomass production was not affected at 4 microL L(-1) NH3, but was reduced at 8 microL L(-1) NH3. In nitrate-deprived plants, shoot biomass was increased at both concentrations, but root biomass decreased at 8 microL L(-1) NH3. The measured nitrate uptake rates agreed well with the plant's N requirement for growth. In nitrate-sufficient plants nitrate uptake at 4 and 8 microL L(-1) NH3 was reduced by 50 and 66 %, respectively. CONCLUSIONS: The present data do not support the hypothesis that NH3 toxicity is caused by a shortage of sugars or a lack of capacity to detoxify NH3. It is unlikely that amino acids, translocated from the shoot to root, are the signal metabolites involved in the down-regulation of nitrate uptake, since no relationship was found between changes in nitrate uptake and root soluble N content of NH3-exposed plants. 相似文献
128.
129.
青花菜雄性不育相关基因BoDHAR的克隆与表达分析 总被引:2,自引:0,他引:2
以一个与甘蓝显性核不育相关的差异表达片段的序列为信息探针,通过在NCBI与TAIR网站数据库中进行同源EST序列搜索,经人工拼接、RT-PCR、PCR克隆与序列分析,获得了青花菜脱氢抗坏血酸还原酶DHARdehydroascorbatereductase基因的cDNA与DNA全长序列,命名为BoDHAR。并利用双链接头介导PCR的染色体步行技术(genomewalking)克隆了其上游644bp的5′端序列。所获的BoDHAR基因全长1486bp,存在两个内含子,DNA编码区序列633bp,编码210个氨基酸;序列分析表明BoDHAR与同源基因AT1G19570.1cDNA序列有82.3%的一致性,推导的氨基酸序列有79.6%的一致性;编码的水溶性蛋白存在多个磷酸化位点;5′端上游区存在明显的转录调控序列。半定量RT-PCR结果表明BoDHAR在可育系花蕾中的表达量明显高于不育系花蕾,在花药中的表达明显高于其它部位。 相似文献
130.