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1.
青冈常绿阔叶林凋落物分解过程中营养元素动态   总被引:12,自引:0,他引:12       下载免费PDF全文
应用分解袋法研究了浙江建德青冈常绿阔叶林凋落物分解过程中的养分动态.结果表明,在2a的分解过程中,各凋落物元素的年均释放率为C 27.91%~44.06%,N 30.77%~39.58%,P 33.33%~42.86%,K 42.31%~48.19%,Ca 18.67%~36.22%,Mg 35.71%~47.22%,Mn 25.00%~37.50%,Cu 3.80%~16.21%,Zn -17.52%~26.60%.K和Mg流动性较大,Zn、Cu和Ca相对稳定,P、Zn、Cu、Ca、N和Mn在分解过程中有不同程度累积.干物质残留量与N、Ca、Mn、Cu和Zn的残留率呈负相关,与C、K和Mg呈正相关.C、N主要以线性衰减方式释放,P和Mg主要以复合函数方式释放,K主要以对数方式释放,Ca、Mn、Cu和Zn残留率具有3种以上的最优模型.Cu、Zn、Ca和Mn对干物质的分解有促进作用.C:N比是预示分解速率的最理想指标.枯叶中C:N比对于N固持和矿化的分界值在20:1左右,C:P比对于P的净矿化的临界值在600:1左右.  相似文献
2.
Yang JL  Li YY  Zhang YJ  Zhang SS  Wu YR  Wu P  Zheng SJ 《Plant physiology》2008,146(2):602-611
Rice (Oryza sativa) is the most aluminum (Al)-resistant crop species among the small-grain cereals, but the mechanisms responsible for this trait are still unclear. Using two rice cultivars differing in Al resistance, rice sp. japonica 'Nipponbare' (an Al-resistant cultivar) and rice sp. indica 'Zhefu802' (an Al-sensitive cultivar), it was found that Al content in the root apex (0-10 mm) was significantly lower in Al-resistant 'Nipponbare' than in sensitive 'Zhefu802', with more of the Al localized to cell walls in 'Zhefu802', indicating that an Al exclusion mechanism is operating in 'Nipponbare'. However, neither organic acid efflux nor changes in rhizosphere pH appear to be responsible for the Al exclusion. Interestingly, cell wall polysaccharides (pectin, hemicellulose 1, and hemicellulose 2) in the root apex were found to be significantly higher in 'Zhefu802' than in 'Nipponbare' in the absence of Al, and Al exposure increased root apex hemicellulose content more significantly in 'Zhefu802'. Root tip cell wall pectin methylesterase (PME) activity was constitutively higher in 'Zhefu802' than in 'Nipponbare', although Al treatment resulted in increased PME activity in both cultivars. Immunolocalization of pectins showed a higher proportion of demethylated pectins in 'Zhefu802', indicating a higher proportion of free pectic acid residues in the cell walls of 'Zhefu802' root tips. Al adsorption and desorption kinetics of root tip cell walls also indicated that more Al was adsorbed and bound Al was retained more tightly in 'Zhefu802', which was consistent with Al content, PME activity, and pectin demethylesterification results. These responses were specific to Al compared with other metals (CdCl(2), LaCl(3), and CuCl(2)), and the ability of the cell wall to adsorb these metals was also not related to levels of cell wall pectins. All of these results suggest that cell wall polysaccharides may play an important role in excluding Al specifically from the rice root apex.  相似文献
3.
陆地生态系统植被氮磷化学计量研究进展   总被引:10,自引:0,他引:10       下载免费PDF全文
刘超  王洋  王楠  王根轩 《植物生态学报》2012,36(11):1205-1216
 因化学功能的耦合和元素的不可替代性, 植物对N、P的需求和利用存在严格的比例。植物N、P化学计量在不同功能群、生长地区、生长季、器官之间以及环境梯度下存在明显的变化规律。多数研究从N、P浓度、N:P及N、P间异速指数等角度分析了植物化学计量变化规律, 并探讨其在全球范围内的具体数值。为增进对植物响应全球变化的理解, 该文综述了N、P化学计量的影响因素及其机理的最新研究进展, 并指出未来拟重点研究的方向。  相似文献
4.
 基于24 hm2古田山中亚热带常绿阔叶林长期监测样地调查资料, 采用Ripley的K函数点格局分析等方法, 具体分析了古田山常绿阔叶林优势树种甜槠(Castanopsis eyrei)与木荷(Schima superba)不同年龄阶段的空间分布格局以及它们之间的空间关联性。结果表明: 两种优势物种在总体上及不同年龄阶段主要呈聚集分布, 且随年龄阶段的增加, 聚集程度有降低的趋势。两物种在大尺度直观上有明显的生境偏好。两种优势物种的幼树、小树与大树和老树主要呈空间负相关或无空间关联性, 与中树呈空间正相关。甜槠中树与大树、大树与老树主要呈空间正相关, 而甜槠的中树与老树呈空间负相关。木荷中树与大树和老树、大树与老树均呈现空间负相关或无关联。我们发现古田山优势物种通过密度制约和Janzen-Connell效应释放空间, 为其他物种共存提供了条件, 密度制约和Janzen-Connell效应可能是古田山样地甜槠和木荷空间格局形成的重要原因。  相似文献
5.
烟粉虱的分类地位及在中国的分布   总被引:9,自引:0,他引:9       下载免费PDF全文
烟粉虱广泛分布于全球热带和亚热带地区。近20多年,烟粉虱的一些遗传群入侵世界各地,严重危害作物生产。烟粉虱遗传结构的多样性和复杂性早已被关注,但其分类地位,尤其是烟粉虱到底是一个包含多个生物型的种还是一个包含许多隐种的物种复合体,一直颇受争议。近几年,有关烟粉虱种系发生和系统学的研究取得长足进展,有证据推论其是一个包含至少31个隐种的物种复合体,但生殖隔离证据仍显不足,种系发生分析结果也因仅依据COI一个基因而受到质疑。因此,在大多数从事烟粉虱研究的同行接受其为一个物种复合体的概念的同时,仍有同行沿用生物型的概念。在我国境内已先后报道了包括13个本地种和2个全球入侵种在内的15个烟粉虱隐种。本地种主要分布在我国南部及包括海南岛和台湾岛的东南沿海地区,隐种的多样性由南向北逐渐降低。入侵种“中东一小亚细亚1”隐种(MEAMl)(即“B型”)和“地中海”隐种(MED)(即“Q型”)分别于20世纪90年代中后期和2003年前后入侵我国,并在许多地区迅速取代了本地种而占据优势地位。全国范围内的调查数据显示,这2个入侵种可在大部分区域共同存在,但自2005年以来,MED在许多地区陆续取代MEAMl,这很可能与MED对大量使用的新烟碱类杀虫剂有较强抗性有关。本文还讨论了烟粉虱隐种复合体分类所面临的命名等难题以及大范围抽样调查的数据偏差问题。  相似文献
6.
Li X  Mo X  Shou H  Wu P 《Plant & cell physiology》2006,47(8):1112-1123
In Arabidopsis, lateral root formation is a post-embryonic developmental event, which is regulated by hormones and environmental signals. In this study, via analyzing the expression of cyclin genes during lateral root (LR) formation, we report that cytokinins (CTKs) inhibit the initiation of LR through blocking the pericycle founder cells cycling at the G(2) to M transition phase, while the promotion by CTK of LR elongation is due to the stimulation of the G(1) to S transition. No significant difference was detected in the inhibitory effect of CTK on LR formation between wild-type plants and mutants defective in auxin response or transport. In addition, exogenously applied auxin at different concentrations could not rescue the CTK-mediated inhibition of LR initiation. Our data suggest that CTK and auxin might control LR initiation through two separate signaling pathways in Arabidopsis. The CTK-mediated repression of LR initiation is transmitted through the two-component signal system and mediated by the receptor CRE1.  相似文献
7.
L. Wu  H. Qiao  Y. Li  L. Li   《Phytomedicine》2007,14(10):652-658
Ischemic heart diseases have been the leading cause of death in both developed and developing countries over the past decades. The aim of this study was to investigate the cardioprotective effects of the complex preparation (called Shenge), made of puerarin (isolated from Pueraria lobata Ohwi., also called Kudzu) and Danshensu (isolated from the Chinese herb, Salvia miltiorrhiza), on acute ischemic myocardial injury in rats and its underlying mechanisms. The left anterior descending (LAD) coronary artery was occluded to induce myocardial ischemia in the hearts of SD rats. Shenge was injected into the tail vein 15 min after occlusion at doses of 0, 30, 60, or 120 mg/kg body wt. ST elevation was then measured at 60, 120, and 240 min after Shenge administration. The ischemic size, serum levels of creatine kinase isoenzyme-MB (CK-MB), lactate dehydrogenase (LDH), superoxide dismutase (SOD) and malondialdehyde (MDA), and ST elevation were measured after the rats were sacrificed. Shenge decreased ST elevation induced by acute myocardial ischemia, reduced ischemic size, serum levels of CK-MB, LDH and MDA, and increased serum activity of SOD in a dose-dependent manner. The combined use of puerarin and Danshensu at a ratio of 1:1 showed the most effective activity. In conclusion, Shenge exerts significant cardioprotective effects against acute ischemic myocardial injury in rats, likely through its antioxidant and anti-lipid peroxidation properties, and thus may be an effective and promising medicine for both prophylaxis and treatment of ischemic heart disease.  相似文献
8.
Zhou J  Jiao F  Wu Z  Li Y  Wang X  He X  Zhong W  Wu P 《Plant physiology》2008,146(4):1673-1686
Previous research has demonstrated that AtPHR1 plays a central role in phosphate (Pi)-starvation signaling in Arabidopsis thaliana. In this work, two OsPHR genes from rice (Oryza sativa) were isolated and designated as OsPHR1 and OsPHR2 based on amino acid sequence homology to AtPHR1. Their functions in Pi signaling in rice were investigated using transgenic plants. Our results showed that both OsPHR1 and OsPHR2 are involved in Pi-starvation signaling pathway by regulation of the expression of Pi-starvation-induced genes, whereas only OsPHR2 overexpression results in the excessive accumulation of Pi in shoots under Pi-sufficient conditions. Under Pi-sufficient conditions, overexpression of OsPHR2 mimics Pi-starvation stress in rice with enhanced root elongation and proliferated root hair growth, suggesting the involvement of OsPHR2 in Pi-dependent root architecture alteration by both systematic and local pathways. In OsPHR2-overexpression plants, some Pi transporters were up-regulated under Pi-sufficient conditions, which correlates with the strongly increased content of Pi. The mechanism behind the OsPHR2 regulated Pi accumulation will provide useful approaches to develop smart plants with high Pi efficiency.  相似文献
9.
红托竹荪菌托多糖的提取及抗肿瘤活性的初步研究   总被引:8,自引:0,他引:8       下载免费PDF全文
赵凯  王飞娟  潘薛波  朱诚 《菌物学报》2008,27(2):289-296
红托竹荪菌托经热水提取、酒精沉淀、脱蛋白后的粗多糖,其得率远大于其菌丝体和子实体的其他部位及香菇子实体.菌托粗多糖进一步用DEAE纤维素柱和Sephadex G-75分离纯化,得到两个组分DRVP1与DRVP2,对分离得到的主要多糖通过高效液相色谱(HPLC)、红外光谱(IR)等进行结构分析.DRVP1的相对分子质量(Mr)为1.47×104,红外光谱数据显示为β-型甘露糖苷.体外试验表明,红托竹荪菌托多糖的组分DRVP1对小鼠S180肉瘤有一定的抑制作用.  相似文献
10.
Mesenchymal stem cells: a promising candidate in regenerative medicine   总被引:7,自引:0,他引:7  
Mesenchymal stem cells were initially characterized as plastic adherent, fibroblastoid cells. In recent years, there has been an increasing focus on mesenchymal stem cells since they have great plasticity and are potential for therapeutic applications. Mesenchymal stem cells or mesenchymal stem cell-like cells have been shown to reside within the connective tissues of most organs. These cells can differentiate into osteogenic, adipogenic and chondrogenic lineages under appropriate conditions. A number of reports have also indicated that these cells possess the capacity to trans-differentiate into epithelial cells and lineages derived from the neuro-ectoderm, and in addition, mesenchymal stem cells can migrate to the sites of injury, inflammation, and to tumors. These properties of mesenchymal stem cells make them promising candidates for use in regenerative medicine and may also serve as efficient delivery vehicles in site-specific therapy.  相似文献
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