全文获取类型
收费全文 | 175篇 |
免费 | 17篇 |
国内免费 | 23篇 |
专业分类
215篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 5篇 |
2012年 | 10篇 |
2011年 | 10篇 |
2010年 | 12篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 16篇 |
2006年 | 10篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1983年 | 2篇 |
1979年 | 2篇 |
排序方式: 共有215条查询结果,搜索用时 15 毫秒
51.
Xiaolei Zhao Shouqiang Zhong Xiaoyu Zuo Meihua Lin Jiheng Qin Yizhao Luan Naizun Zhang 《基因组蛋白质组与生物信息学报(英文版)》2014,12(1):31-38
Many cancers apparently showing similar phenotypes are actually distinct at the molecular level,leading to very different responses to the same treatment.It has been recently demonstrated that pathway-based approaches are robust and reliable for genetic analysis of cancers.Nevertheless,it remains unclear whether such function-based approaches are useful in deciphering molecular heterogeneities in cancers.Therefore,we aimed to test this possibility in the present study.First,we used a NCI60 dataset to validate the ability of pathways to correctly partition samples.Next,we applied the proposed method to identify the hidden subtypes in diffuse large B-cell lymphoma (DLBCL).Finally,the clinical significance of the identified subtypes was verified using survival analysis.For the NCI60 dataset,we achieved highly accurate partitions that best fit the clinical cancer phenotypes.Subsequently,for a DLBCL dataset,we identified three hidden subtypes that showed very different 10-year overall survival rates (90%,46% and 20%) and were highly significantly (P =0.008) correlated with the clinical survival rate.This study demonstrated that the pathwaybased approach is promising for unveiling genetic heterogeneities in complex human diseases. 相似文献
52.
Burkart S Manderscheid R Wittich KP Löpmeier FJ Weigel HJ 《Plant biology (Stuttgart, Germany)》2011,13(2):258-269
An arable crop rotation (winter barley-sugar beet-winter wheat) was exposed to elevated atmospheric CO(2) concentrations ([CO(2) ]) using a FACE facility (Free-Air CO(2) Enrichment) during two rotation periods. The atmospheric [CO(2) ] of the treatment plots was elevated to 550 ppm during daylight hours (T>5°C). Canopy transpiration (E(C) ) and conductance (G(C) ) were measured at selected intervals (>10% of total growing season) using a dynamic CO(2) /H(2) O chamber measuring system. Plant available soil water content (gravimetry and TDR probes) and canopy microclimate conditions were recorded in parallel. Averaged across both growing seasons, elevated [CO(2) ] reduced E(C) by 9%, 18% and 12%, and G(C) by 9%, 17% and 12% in barley, sugar beet and wheat, respectively. Both global radiation (Rg) and vapour pressure deficit (VPD) were the main driving forces of E(C) , whereas G(C) was mostly related to Rg. The responses of E(C) and especially G(C) to [CO(2) ] enrichment were insensitive to weather conditions and leaf area index. However, differences in LAI between plots counteracted the [CO(2) ] impact on E(C) and thus, at least in part, explained the variability of seasonal [CO(2) ] responses between crops and years. As a consequence of lower transpirational canopy water loss, [CO(2) ] enrichment increased plant available soil water content in the course of the season by ca. 15 mm. This was true for all crops and years. Lower transpirational cooling due to a [CO(2) ]-induced reduction of E(C) increased canopy surface and air temperature by up to 2 °C and 0.5 °C, respectively. This is the first study to address effects of FACE on both water fluxes at canopy scale and water status of a European crop rotation. 相似文献
53.
Phospholipids are major building blocks for biological membranes. In addition, metabolites derived from their degradation are important signals in major cellular events, such as proliferation and apoptosis. The concept of lipid signaling in cells is derived mainly from the measurement of change in the concentration of lipid molecules. However, these changes in concentration are only a small part of the underlying metabolic change induced by a perturbation in the cell. In contrast, metabolic kinetic studies documenting product-precursor relationships and turnover rates are useful in elucidating the responsible mechanisms. Historically, metabolic studies of phospholipids in cells have been carried out with pulse or pulse-chase methods using radioactive isotopes. While these studies provide valuable information, their scope is restricted by inherent limitations. In this paper we describe a method using [1,2,3,4-13C(4)]palmitate as the tracer for studying the metabolic kinetics of the molecular species of diacylglycerol, ceramide, phosphatidylcholine, and sphingomyelin. After growing cells in the presence of labeled palmitate complexed to serum albumin, the lipids are extracted and separated into lipid classes. After enzymatic hydrolysis, diacylglyerols and ceramides as bis-trimethylsilyl derivatives are determined quantitatively with capillary column gas chromatography. Internal standards for each lipid class are used in the procedure. In addition, the isotopic enrichments of the lipid molecular species are determined with gas chromatograph-mass spectrometry. We applied this method to the study of HL60 cells. Different turnover rates were found for various molecular species. In addition, the sn-1 and sn-2 acyl groups appear to be synthesized at different rates for different molecular species. Other information, such as chain elongation and desaturation, might also be derived through the use of this method. 相似文献
54.
María?M.?LópezEmail author Edson?Bertolini Antonio?Olmos Paola?Caruso María?Teresa?Gorris Pablo?Llop Ramón?Penyalver Mariano?Cambra 《International microbiology》2003,6(4):233-243
Detection of harmful viruses and bacteria in plant material, vectors or natural reservoirs is essential to ensure safe and sustainable agriculture. The techniques available have evolved significantly in the last few years to achieve rapid and reliable detection of pathogens, extraction of the target from the sample being important for optimising detection. For viruses, sample preparation has been simplified by imprinting or squashing plant material or insect vectors onto membranes. To improve the sensitivity of techniques for bacterial detection, a prior enrichment step in liquid or solid medium is advised. Serological and molecular techniques are currently the most appropriate when high numbers of samples need to be analysed. Specific monoclonal and/or recombinant antibodies are available for many plant pathogens and have contributed to the specificity of serological detection. Molecular detection can be optimised through the automatic purification of nucleic acids from pathogens by columns or robotics. New variants of PCR, such as simple or multiplex nested PCR in a single closed tube, co-operative-PCR and real-time monitoring of amplicons or quantitative PCR, allow high sensitivity in the detection of one or several pathogens in a single assay. The latest development in the analysis of nucleic acids is micro-array technology, but it requires generic DNA/RNA extraction and pre-amplification methods to increase detection sensitivity. The advances in research that will result from the sequencing of many plant pathogen genomes, especially now in the era of proteomics, represent a new source of information for the future development of sensitive and specific detection techniques for these microorganisms. 相似文献
55.
Microprotoplast isolation, enrichment and fusion for partial genome transfer in plants 总被引:1,自引:0,他引:1
K. S. Ramulu P. Dijkhuis H. A. Verhoeven I. Famelaer J. Blaas 《Physiologia plantarum》1992,85(2):315-318
Somatic hybridization using protoplasts with whole genomes has often resulted in complex hybrids with many unwanted chromosomes or genes. Several researchers have attempted to reduce the number of undesired chromosomes through irradiation of the donor protoplasts, but so far without much success. Alternatively, micropro-toplasts containing one or a few chromosomes can be used for partial genome transfer, as has been demonstrated in human and other mammalian cell systems using microcells. Recently, we have optimized the 'microprotoplast system' for several donor cell lines (potato, Nicotiana , sugar beet) carrying various genetic markers, such as kanamycin resistance, β-glucuronidase, nitrate reductase deficiency, hormone autotrophy, opines, etc. Protocols were developed to obtain higher yields of micro-protoplasts as well as to enrich sub-diploid microprotoplasts containing one or a few chromosomes. These microprotoplasts were fused with whole mesophyll protoplasts of recipient lines using polyethylene glycol. Various requirements for lines used as donor and recipient partners in microprotoplast-protoplast fusions are described. The results are discussed in the context of partial genome transfer. 相似文献
56.
采用Biolog和变性梯度凝胶电泳(DGGE)技术研究了不同苯酚浓度培养对焦化废水处理厂反硝化池生物膜样品中微生物群落结构和代谢类型的影响。DGGE结果表明, 不同浓度苯酚和不同培养方式富集培养后, 细菌16S rDNA的部分条带分布谱形发生改变, 还有部分条带只受到了苯酚浓度变化的影响; 富集培养过程中由于碳源组成相对焦化废水简单, DGGE条带所代表的优势微生物多样性有所降低。Biolog试验结果表明, 生物膜样本的细菌群落代谢能力最强; 低浓度苯酚富集后的样品能利用的底物碳源类型最丰富。对Biolog试验结果的主成分分析显示, 相同浓度苯酚富集培养后的细菌群落代谢功能多样性相似, 但从DGGE结果看出其结构组成产生了变化。富集培养使样品微生物群落的代谢功能发生改变, 低浓度的苯酚富集增加了群落中微生物的代谢类型。而不同条件获得的分离物其苯酚降解能力的初步分析也表明, 富集与分离条件对苯酚降解菌的分离能力和得到的菌株特性具有差别。 相似文献
57.
Ida Autiero Menotti Ruvo Roberto Improta Luigi Vitagliano 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(4):1006-1016
Background
Aptamers are RNA/DNA biomolecules representing an emerging class of protein interactors and regulators. Despite the growing interest in these molecules, current understanding of chemical-physical basis of their target recognition is limited. Recently, the characterization of the aptamer targeting the protein-S8 has suggested that flexibility plays important functional roles. We investigated the structural versatility of the S8-aptamer by molecular dynamics simulations.Methods
Five different simulations have been conducted by varying starting structures and temperatures.Results
The simulation of S8-aptamer complex provides a dynamic view of the contacts occurring at the complex interface. The simulation of the aptamer in ligand-free state indicates that its central region is intrinsically endowed with a remarkable flexibility. Nevertheless, none of the trajectory structures adopts the structure observed in the S8-aptamer complex. The aptamer ligand-bound is very rigid in the simulation carried out at 300?K. A structural transition of this state, providing insights into the aptamer-protein recognition process, is observed in a simulation carried out at 400?K. These data indicate that a key event in the binding is linked to the widening of the central region of the aptamer. Particularly relevant is switch of the A26 base from its ligand-free state to a location that allows the G13-C28 base-pairing.Conclusions
Intrinsic flexibility of the aptamer is essential for partner recognition. Present data indicate that S8 recognizes the aptamer through an induced-fit rather than a population-shift mechanism.General significance
The present study provides deeper understanding of the structural basis of the structural versatility of aptamers. 相似文献58.
Investigating unidentified weak-acting lectins is important for understanding glycan-related phenomena. We have developed an improved screening method for weak-acting lectins using glycan-conjugated magnetic beads (or glycobeads) involving a partial washing method and named it the mild enrichment procedure. Weak-acting lectins exist in equilibrium between bound lectin and free lectin produced by dissociation, whereas most tight-binding lectin exists in a bound state. The conventional washing step, in which the solution phase is replaced, may remove dissociated lectin from around the glycobeads; therefore, we attempted to leave a buffer space around the glycobeads to maintain the association–dissociation equilibrium of weak-acting lectins. Our results revealed that our mild enrichment procedure for screening for weak interactions, such as maltose–concanavalin A (Ka ∼ 104 M−1) and lactose–peanut agglutinin (Ka ∼ 103 M−1) interactions, was more effective than conventional batch methods. 相似文献
59.
60.
Thongaram T Hongoh Y Kosono S Ohkuma M Trakulnaleamsai S Noparatnaraporn N Kudo T 《Extremophiles : life under extreme conditions》2005,9(3):229-238
The first proctodeal (P1) segment in the hindgut of certain higher termites shows high alkalinity. We examined the bacterial diversity of the alkaline P1 gut segments of four species of higher termites by T-RFLP and phylogenetic analyses based on PCR-amplified 16S rRNA genes. The bacterial community of the P1 segment was apparently different from that of the whole gut in each termite. Sequence analysis revealed that Firmicutes (Clostridia and Bacilli) were dominant in the P1 segments of all four termites; however, the phylogenetic compositions varied among the termites. Although some of the P1 segment-derived sequences were related to the sequences previously reported from the alkaline digestive tracts of other insects, most of them formed phylogenetic clusters unique to termites. Such termite P1 clusters were distantly related to known bacterial species as well as to sequences reported from alkaline environments in nature. We successfully obtained enrichment cultures of Clostridia- and Bacilli-related bacteria, including putative novel species under anaerobic alkaline conditions from the termite guts. Our results suggest that the alkaline gut region of termites harbors unique bacterial lineages and are expected to be a rich reservoir of novel alkaliphiles yet to be cultivated. 相似文献