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   51篇
  免费   0篇
  国内免费   1篇
系统科学   3篇
现状及发展   8篇
研究方法   9篇
综合类   29篇
自然研究   3篇
  2021年   1篇
  2019年   2篇
  2018年   2篇
  2017年   3篇
  2016年   1篇
  2014年   1篇
  2013年   2篇
  2012年   4篇
  2011年   3篇
  2008年   5篇
  2007年   6篇
  2006年   6篇
  2005年   3篇
  2004年   3篇
  2003年   1篇
  2002年   5篇
  2000年   1篇
  1999年   1篇
  1966年   2篇
排序方式: 共有52条查询结果,搜索用时 15 毫秒
31.
This paper is devoted to the construction of one-Lee weight codes and two-Lee weight codes over F p + vF p (v 2 = v) with type \({p^{2{k_1}}}{p^{{k_2}}}{p^{{k_3}}}\) based on two different distance-preserving Gray maps from ((F p + vF p ) n , Lee weight) to (F p 2n , Hamming weight), where p is a prime. Moreover, the authors prove that the obtained two-Lee weight codes are projective only when p = 2.  相似文献   
32.
We identified association of restless legs syndrome (RLS) with PTPRD at 9p23-24 in 2,458 affected individuals and 4,749 controls from Germany, Austria, Czechia and Canada. Two independent SNPs in the 5' UTR of splice variants expressed predominantly in the central nervous system showed highly significant P values (rs4626664, P(nominal/lambda corrected) = 5.91 x 10(-10), odds ratio (OR) = 1.44; rs1975197, P(nominal/lambda corrected) = 5.81 x 10(-9), OR = 1.31). This work identifies PTPRD as the fourth genome-wide significant locus for RLS.  相似文献   
33.
We carried out whole-genome homozygosity mapping, gene expression analysis and DNA sequencing in individuals with isolated mitochondrial ATP synthase deficiency and identified disease-causing mutations in TMEM70. Complementation of the cell lines of these individuals with wild-type TMEM70 restored biogenesis and metabolic function of the enzyme complex. Our results show that TMEM70 is involved in mitochondrial ATP synthase biogenesis in higher eukaryotes.  相似文献   
34.
Friml J  Wiśniewska J  Benková E  Mendgen K  Palme K 《Nature》2002,415(6873):806-809
Long-standing models propose that plant growth responses to light or gravity are mediated by asymmetric distribution of the phytohormone auxin. Physiological studies implicated a specific transport system that relocates auxin laterally, thereby effecting differential growth; however, neither the molecular components of this system nor the cellular mechanism of auxin redistribution on light or gravity perception have been identified. Here, we show that auxin accumulates asymmetrically during differential growth in an efflux-dependent manner. Mutations in the Arabidopsis gene PIN3, a regulator of auxin efflux, alter differential growth. PIN3 is expressed in gravity-sensing tissues, with PIN3 protein accumulating predominantly at the lateral cell surface. PIN3 localizes to the plasma membrane and to vesicles that cycle in an actin-dependent manner. In the root columella, PIN3 is positioned symmetrically at the plasma membrane but rapidly relocalizes laterally on gravity stimulation. Our data indicate that PIN3 is a component of the lateral auxin transport system regulating tropic growth. In addition, actin-dependent relocalization of PIN3 in response to gravity provides a mechanism for redirecting auxin flux to trigger asymmetric growth.  相似文献   
35.
The α-amylase enzyme family is the largest family of glycoside hydrolases. It contains almost 30 different enzyme specificities covering hydrolases, transferases and isomerases. Some of the enzyme specificities from the family are closely related, others less so. This study, based on the analysis of 79 amino acid sequences, postulates two subfamilies in the framework of the α-amylase family: the oligo-1,6-glucosidase subfamily and the neopullulanase subfamily. The specific sequence in the fifth conserved sequence region of the family served as the basis for defining the subfamilies: QpDln for the oligo-1,6-glucosidase subfamily and MPKln for the neopullulanase subfamily. This conserved sequence region is proposed to be the selection marker that enables one to distinguish between the two subfamilies. The 'intermediary' sequence MPDLN can be characteristic of the so-called intermediary group with a mixed enzyme specificity of α-amylase, cyclomaltodextrinase and neopullulanase. The evolutionary trees clearly supported the proposed definition of the two subfamilies. Received 12 July 2002; received after revision 28 August 2002; accepted 24 September 2002 RID="*" ID="*"Corresponding author.  相似文献   
36.
Auxin inhibits endocytosis and promotes its own efflux from cells   总被引:2,自引:0,他引:2  
One of the mechanisms by which signalling molecules regulate cellular behaviour is modulating subcellular protein translocation. This mode of regulation is often based on specialized vesicle trafficking, termed constitutive cycling, which consists of repeated internalization and recycling of proteins to and from the plasma membrane. No such mechanism of hormone action has been shown in plants although several proteins, including the PIN auxin efflux facilitators, exhibit constitutive cycling. Here we show that a major regulator of plant development, auxin, inhibits endocytosis. This effect is specific to biologically active auxins and requires activity of the Calossin-like protein BIG. By inhibiting the internalization step of PIN constitutive cycling, auxin increases levels of PINs at the plasma membrane. Concomitantly, auxin promotes its own efflux from cells by a vesicle-trafficking-dependent mechanism. Furthermore, asymmetric auxin translocation during gravitropism is correlated with decreased PIN internalization. Our data imply a previously undescribed mode of plant hormone action: by modulating PIN protein trafficking, auxin regulates PIN abundance and activity at the cell surface, providing a mechanism for the feedback regulation of auxin transport.  相似文献   
37.
Phosphorus (P) is generally considered the most common limiting nutrient for productivity of mature tropical lowland forests growing on highly weathered soils. It is often assumed that P limitation also applies to young tropical forests, but nitrogen (N) losses during land-use change may alter the stoichiometric balance of nutrient cycling processes. In the Amazon basin, about 16% of the original forest area has been cleared, and about 30-50% of cleared land is estimated now to be in some stage of secondary forest succession following agricultural abandonment. Here we use forest age chronosequences to demonstrate that young successional forests growing after agricultural abandonment on highly weathered lowland tropical soils exhibit conservative N-cycling properties much like those of N-limited forests on younger soils in temperate latitudes. As secondary succession progresses, N-cycling properties recover and the dominance of a conservative P cycle typical of mature lowland tropical forests re-emerges. These successional shifts in N:P cycling ratios with forest age provide a mechanistic explanation for initially lower and then gradually increasing soil emissions of the greenhouse gas nitrous oxide (N(2)O). The patterns of N and P cycling during secondary forest succession, demonstrated here over decadal timescales, are similar to N- and P-cycling patterns during primary succession as soils age over thousands and millions of years, thus revealing that N availability in terrestrial ecosystems is ephemeral and can be disrupted by either natural or anthropogenic disturbances at several timescales.  相似文献   
38.
39.
Mulibrey nanism (for muscle-liver-brain-eye nanism, MUL; MIM 253250) is an autosomal recessive disorder that involves several tissues of mesodermal origin, implying a defect in a highly pleiotropic gene. Characteristic features include severe growth failure of prenatal onset and constrictive pericardium with consequent hepatomegaly. In addition, muscle hypotonia, J-shaped sella turcica, yellowish dots in the ocular fundi, typical dysmorphic features and hypoplasia of various endocrine glands causing hormonal deficiency are common. About 4% of MUL patients develop Wilms' tumour. MUL is enriched in the Finnish population, but is rare elsewhere. We previously assigned MUL to chromosome 17q22-q23 and constructed a physical contig over the critical MUL region. The region has now been further refined by haplotype analysis and new positional candidate genes have been localized. We identified a gene with four independent MUL-associated mutations that all cause a frameshift and predict a truncated protein. MUL is ubiquitously expressed and encodes a new member of the RING-B-box-Coiled-coil (RBCC) family of zinc-finger proteins, whose members are involved in diverse cellular functions such as developmental patterning and oncogenesis.  相似文献   
40.
Abstract Scoring in a basketball game is a highly dynamic, non-linear process. NBA teams try to be more and more competitive each season. For instance, they incorporate into their rosters the best players in the world. This and other mechanisms concur to make the scoring process in NBA games exciting and rarely predictable. This paper is to study the behavior of timing and scoring in basketball games. The authors analyze all the games in five NBA regular seasons (2005–06, 2006–07, 2007–08, 2008–09, 2009–10), for a total of 6150 games. Scoring does not behave uniformly; therefore, the authors also analyze the distributions of the differences in points in the basketball games. To further analyze the behavior of the tail of the distribution, the authors also carry out a semilog-plot and a log-log plot to verify whether this trend approaches a Poisson distribution or a PL. This paper reveals different areas of behavior related to the score, with specific instances of time that could be considered tipping points of the game. The presence of these critical points suggests that there are phase transitions where the dynamic scoring of the games varies significantly.  相似文献   
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