全文获取类型
收费全文 | 99篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 2篇 |
丛书文集 | 2篇 |
教育与普及 | 2篇 |
理论与方法论 | 13篇 |
现状及发展 | 20篇 |
研究方法 | 10篇 |
综合类 | 51篇 |
自然研究 | 1篇 |
出版年
2020年 | 1篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 8篇 |
2011年 | 14篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 11篇 |
2007年 | 4篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有101条查询结果,搜索用时 15 毫秒
91.
Klaus Regenauer-Lieb Andrew Bunger Hui Tong Chua Arcady Dyskin Florian Fusseis Oliver Gaede Rob Jeffrey Ali Karrech Thomas Kohl Jie Liu Vladimir Lyakhovsky Elena Pasternak Robert Podgorney Thomas Poulet Sheik Rahman Christoph Schrank Mike Trefry Manolis Veveakis Bisheng Wu David A. Yuen Florian Wellmann Xi Zhang 《地球科学学刊》2015,(1)
Deep geothermal from the hot crystalline basement has remained an unsolved frontier for the geothermal industry for the past 30 years. This poses the challenge for developing a new un-conventional geom... 相似文献
92.
The ion selectivity of pumps and channels is central to their ability to perform a multitude of functions. Here we investigate the mechanism of the extraordinary selectivity of the human voltage-gated proton channel, H(V)1 (also known as HVCN1). This selectivity is essential to its ability to regulate reactive oxygen species production by leukocytes, histamine secretion by basophils, sperm capacitation, and airway pH. The most selective ion channel known, H(V)1 shows no detectable permeability to other ions. Opposing classes of selectivity mechanisms postulate that (1) a titratable amino acid residue in the permeation pathway imparts proton selectivity, or (2) water molecules 'frozen' in a narrow pore conduct protons while excluding other ions. Here we identify aspartate 112 as a crucial component of the selectivity filter of H(V)1. When a neutral amino acid replaced Asp?112, the mutant channel lost proton specificity and became anion-selective or did not conduct. Only the glutamate mutant remained proton-specific. Mutation of the nearby Asp?185 did not impair proton selectivity, indicating that Asp?112 has a unique role. Although histidine shuttles protons in other proteins, when histidine or lysine replaced Asp?112, the mutant channel was still anion-permeable. Evidently, the proton specificity of H(V)1 requires an acidic group at the selectivity filter. 相似文献
93.
94.
Transient cyclical methylation of promoter DNA 总被引:3,自引:0,他引:3
Kangaspeska S Stride B Métivier R Polycarpou-Schwarz M Ibberson D Carmouche RP Benes V Gannon F Reid G 《Nature》2008,452(7183):112-115
95.
Often the data units are described with discrete distributions (work described with citation distribution over time, population
pyramid described as age-sex distribution etc.).When the set of such units is very large, appropriate clustering methods can
reveal the typical patterns hidden in the data. 相似文献
96.
DT Jones N Jäger M Kool T Zichner B Hutter M Sultan YJ Cho TJ Pugh V Hovestadt AM Stütz T Rausch HJ Warnatz M Ryzhova S Bender D Sturm S Pleier H Cin E Pfaff L Sieber A Wittmann M Remke H Witt S Hutter T Tzaridis J Weischenfeldt B Raeder M Avci V Amstislavskiy M Zapatka UD Weber Q Wang B Lasitschka CC Bartholomae M Schmidt C von Kalle V Ast C Lawerenz J Eils R Kabbe V Benes P van Sluis J Koster R Volckmann D Shih MJ Betts RB Russell S Coco GP Tonini U Schüller V Hans N Graf YJ Kim C Monoranu 《Nature》2012,488(7409):100-105
Medulloblastoma is an aggressively growing tumour, arising in the cerebellum or medulla/brain stem. It is the most common malignant brain tumour in children, and shows tremendous biological and clinical heterogeneity. Despite recent treatment advances, approximately 40% of children experience tumour recurrence, and 30% will die from their disease. Those who survive often have a significantly reduced quality of life. Four tumour subgroups with distinct clinical, biological and genetic profiles are currently identified. WNT tumours, showing activated wingless pathway signalling, carry a favourable prognosis under current treatment regimens. SHH tumours show hedgehog pathway activation, and have an intermediate prognosis. Group 3 and 4 tumours are molecularly less well characterized, and also present the greatest clinical challenges. The full repertoire of genetic events driving this distinction, however, remains unclear. Here we describe an integrative deep-sequencing analysis of 125 tumour-normal pairs, conducted as part of the International Cancer Genome Consortium (ICGC) PedBrain Tumor Project. Tetraploidy was identified as a frequent early event in Group 3 and 4 tumours, and a positive correlation between patient age and mutation rate was observed. Several recurrent mutations were identified, both in known medulloblastoma-related genes (CTNNB1, PTCH1, MLL2, SMARCA4) and in genes not previously linked to this tumour (DDX3X, CTDNEP1, KDM6A, TBR1), often in subgroup-specific patterns. RNA sequencing confirmed these alterations, and revealed the expression of what are, to our knowledge, the first medulloblastoma fusion genes identified. Chromatin modifiers were frequently altered across all subgroups. These findings enhance our understanding of the genomic complexity and heterogeneity underlying medulloblastoma, and provide several potential targets for new therapeutics, especially for Group 3 and 4 patients. 相似文献
97.
Comparing resemblance measures 总被引:4,自引:0,他引:4
In the paper some types of equivalences over resemblance measures and some basic results about them are given. Based on induced partial orderings on the set of unordered pairs of units a dissimilarity between two resemblance measures over finite sets of units can be defined. As an example, using this dissimilarity standard association coefficients between binary vectors are compared both theoretically and computationally.Extended version of the paper presented at DISTANCIA'92, June 22–26, 1992, Rennes, France. This work was supported in part by the Ministry for Science and Technology of Slovenia, J2-6191-101-94. We would like to thank the editor and two anonymous referees for numerous remarks and suggestions that significantly improved the presentation of the material. 相似文献
98.
Irina I. Zaitseva Monica Hultcrantz Vladimir Sharoyko Malin Flodström-Tullberg Sergei V. Zaitsev Per-Olof Berggren 《Cellular and molecular life sciences : CMLS》2009,66(23):3787-3795
Pancreatic beta cell damage caused by pro-inflammatory cytokines interleukin-1β (IL-1β), interferon-γ (IFNγ) and tumor necrosis factor-α (TNFα) is a key event in the pathogenesis of type 1 diabetes. The suppressor of cytokine signaling-1 (SOCS-1) blocks IFNγ-induced signaling and prevents diabetes in the non-obese diabetic mouse. Here, we investigated if SOCS-1 overexpression in primary beta cells provides protection from cytokine-induced islet cell dysfunction and death. We demonstrate that SOCS-1 does not prevent increase in NO production and decrease in glucose-stimulated insulin secretion in the presence of IL-1β, IFNγ, TNFα. However, it decreases the activation of caspase-3, -8 and -9, and thereby, promotes a robust protection from cytokine-induced beta cell death. Our data suggest that SOCS-1 overexpression may not be sufficient in preventing all the biological activities of IFNγ in beta cells. In summary, we show that interference with IFNγ signal transduction pathways by SOCS-1 inhibits cytokine-stimulated pancreatic beta cell death. 相似文献
99.
Societal needs for greater security require dramatic improvements in the sensitivity of chemical and biological sensors. To meet this challenge, increasing emphasis in analytical science has been directed towards materials and devices having highly nonlinear characteristics; semiconducting organic polymers (SOPs), with their facile excited state (exciton) transport, are prime examples of amplifying materials. SOPs have also been recognized as promising lasing materials, although the susceptibility of these materials to optical damage has thus far limited applications. Here we report that attenuated lasing in optically pumped SOP thin films displays a sensitivity to vapours of explosives more than 30 times higher than is observed from spontaneous emission. Critical to this achievement was the development of a transducing polymer with high thin-film quantum yield, a high optical damage threshold in ambient atmosphere and a record low lasing threshold. Trace vapours of the explosives 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT) introduce non-radiative deactivation pathways that compete with stimulated emission. We demonstrate that the induced cessation of the lasing action, and associated sensitivity enhancement, is most pronounced when films are pumped at intensities near their lasing threshold. The combined gains from amplifying materials and lasing promise to deliver sensors that can detect explosives with unparalleled sensitivity. 相似文献
100.
Vladimir V. Frolkis 《Cellular and molecular life sciences : CMLS》1981,37(10):1043-1046