全文获取类型
收费全文 | 149篇 |
免费 | 19篇 |
出版年
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 26篇 |
2011年 | 7篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 3篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1992年 | 2篇 |
1989年 | 2篇 |
1975年 | 2篇 |
1943年 | 1篇 |
1929年 | 1篇 |
1926年 | 1篇 |
1925年 | 1篇 |
1924年 | 1篇 |
1921年 | 1篇 |
1920年 | 1篇 |
1915年 | 2篇 |
1914年 | 1篇 |
1909年 | 1篇 |
1902年 | 1篇 |
1901年 | 1篇 |
1897年 | 2篇 |
1892年 | 1篇 |
1891年 | 1篇 |
1889年 | 1篇 |
1888年 | 1篇 |
1887年 | 1篇 |
1883年 | 3篇 |
1882年 | 5篇 |
1881年 | 2篇 |
1880年 | 1篇 |
1879年 | 6篇 |
1878年 | 2篇 |
1877年 | 2篇 |
1876年 | 1篇 |
排序方式: 共有168条查询结果,搜索用时 484 毫秒
101.
In 1950, Raphael Patai published his research on Venta Prieta, a Mexican town in which some residents lived as Jews despite having little knowledge of Judaism. Like other visitors, Patai was perplexed. Why did they wish to live as Jews? While Patai never answered this question to his satisfaction, he believed the answer would be found by developing a psychological profile of the residents, an approach in keeping with culture and personality theorists of the day. The present article provides a different solution. Drawing on additional sources, and short visits, we argue that Venta Prieta was not only a stop on the Jewish tourist circuit by 1950 but also developed out of a unique exchange. While U.S. Jews, as evangelical Protestants before them, provided a model for upwardly mobile Mexicans, Venta Prieta enabled middle-class tourists to experience Judaism in a pastoral setting and to "repair the world" (tikkun). [Keywords: Judaism, tourism, dialogical anthropology, social change, social mobility] 相似文献
102.
LAURIE A. HALL PER J. PALSBØLL STEVEN R. BEISSINGER JAMES T. HARVEY MARTINE BÉRUBÉ MARTIN G. RAPHAEL S. KIM NELSON RICHARD T. GOLIGHTLY LAURA MCFARLANE‐TRANQUILLA SCOTT H. NEWMAN M. ZACHARIAH PEERY 《Molecular ecology》2009,18(24):5074-5085
Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (FST~ 0.03) from larger populations to the north. We used coalescent simulations to select a significance level that resulted in a low and approximately equal expected number of type I and II errors and then used this significance level to identify a population of origin for 589 individuals genotyped at 13 microsatellite loci. The proportion of migrants in central California was greatest during winter when 83% of individuals were classified as migrants compared to lower proportions during the breeding (6%) and post‐breeding (8%) seasons. Dispersal was also biased toward young and female individuals, as is typical in birds. Migrants were rarely members of parent‐offspring pairs, suggesting that they contributed few young to the central California population. A greater number of migrants than expected under equilibrium conditions, a lack of individuals with mixed ancestry, and a small number of potential source populations (two), likely allowed us to use assignment methods to rigorously characterize dispersal patterns for a population that was larger and less differentiated than typically thought required for the identification of migrants. 相似文献
103.
Charles D Criscione Claudia LL Valentim Hirohisa Hirai Philip T LoVerde Timothy JC Anderson 《Genome biology》2009,10(6):R71-13
Background
Schistosoma mansoni is a blood fluke that infects approximately 90 million people. The complete life cycle of this parasite can be maintained in the laboratory, making this one of the few experimentally tractable human helminth infections, and a rich literature reveals heritable variation in important biomedical traits such as virulence, host-specificity, transmission and drug resistance. However, there is a current lack of tools needed to study S. mansoni's molecular, quantitative, and population genetics. Our goal was to construct a genetic linkage map for S. mansoni, and thus provide a new resource that will help stimulate research on this neglected pathogen. 相似文献104.
LOVE DALÉN EVA FUGLEI PÁLL HERSTEINSSON CHRISTIAN M. O. KAPEL JAMES D. ROTH GUSTAF SAMELIUS MAGNUS TANNERFELDT ANDERS ANGERBJÖRN 《Biological journal of the Linnean Society. Linnean Society of London》2005,84(1):79-89
The circumpolar arctic fox Alopex lagopus thrives in cold climates and has a high migration rate involving long-distance movements. Thus, it differs from many temperate taxa that were subjected to cyclical restriction in glacial refugia during the Ice Ages. We investigated population history and genetic structure through mitochondrial control region variation in 191 arctic foxes from throughout the arctic. Several haplotypes had a Holarctic distribution and no phylogeographical structure was found. Furthermore, there was no difference in haplotype diversity between populations inhabiting previously glaciated and unglaciated regions. This suggests current gene flow among the studied populations, with the exception of those in Iceland, which is surrounded by year-round open water. Arctic foxes have often been separated into two ecotypes: 'lemming' and 'coastal'. An analysis of molecular variance suggested particularly high gene flow among populations of the 'lemming' ecotype. This could be explained by their higher migration rate and reduced fitness in migrants between ecotypes. A mismatch analysis indicated a sudden expansion in population size around 118 000 BP, which coincides with the last interglacial. We propose that glacial cycles affected the arctic fox in a way opposite to their effect on temperate species, with interglacials leading to short-term isolation in northern refugia. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 79–89. 相似文献
105.
Gustavo?Camps-VallsEmail author Alistair?M?Chalk Antonio?J?Serrano-López José?D?Martín-Guerrero Erik?LL?Sonnhammer 《BMC bioinformatics》2004,5(1):135
Background
This paper presents the use of Support Vector Machines (SVMs) for prediction and analysis of antisense oligonucleotide (AO) efficacy. The collected database comprises 315 AO molecules including 68 features each, inducing a problem well-suited to SVMs. The task of feature selection is crucial given the presence of noisy or redundant features, and the well-known problem of the curse of dimensionality. We propose a two-stage strategy to develop an optimal model: (1) feature selection using correlation analysis, mutual information, and SVM-based recursive feature elimination (SVM-RFE), and (2) AO prediction using standard and profiled SVM formulations. A profiled SVM gives different weights to different parts of the training data to focus the training on the most important regions. 相似文献106.
Actin-based motility as a self-organized system: mechanism and reconstitution in vitro 总被引:5,自引:0,他引:5
Site-directed actin polymerisation in response to signalling is responsible for the formation of cell protrusions. These elementary 'actin-based motility processes' are involved in cell locomotion, cell metastasis, organ morphogenesis and microbial pathogenesis. We have reconstituted actin-based propulsive movement of particles of various sizes and geometries (rods, microspheres) in a minimum motility medium containing five pure proteins. The ATP-supported treadmilling of actin filaments, regulated by Actin Depolymerizing Factor (ADF/cofilin), profilin and capping proteins provides the thermodynamic basis for sustained actin-based movement. Local activation of Arp2/3 complex at the surface of the particle promotes autocatalytic barbed end branching of filaments, generating a polarized arborescent array. Barbed end growth of branched filaments against the surface generates a propulsive force and is eventually arrested by capping proteins. Understanding the mechanism of actin-based movement requires elucidation of the biochemical properties and mode of action of Arp2/3 complex in filament branching, in particular the role of ATP binding and hydrolysis in Arp2/3, and a physical analysis of the movement of functionalised particles. Because the functionalisation of the particle by an activator of Arp2/3 complex (N-WASP or the Listeria protein ActA) and the concentrations of effectors in the medium are controlled, the reconstituted motility assay allows an analysis of the mechanism of force production at the mesoscopic and molecular levels. 相似文献
107.
108.
Recombinant adenovirus is one of the primary vectors for human gene therapy. However, the aggregation of unstable virus has
been a recurring problem during the production of purified virus for human therapeutics. To facilitate the development of
a robust manufacturing process for recombinant adenovirus vectors, a convenient and reliable size distribution analytical
assay is necessary and we demonstrate here that disc centrifuge sedimentation is applicable to this purpose. Using the disc
centrifuge system and the line start method, the assay can provide particle size distribution of adenovirus samples within
30 min. The assay can detect virus concentrations down to 0.01% (w/v) or 3 × 1011 particles per ml. The apparent hydrodynamic diameter of recombinant adenovirus was determined to be about 0.063 μm. Furthermore,
the disc centrifuge analysis was able to detect adenovirus dimers, trimers, and tetramers, consistent with a rigid sphere
approximation for adenovirus, as well as a large aggregate of 0.35 μm. The appearance of viral aggregates is confirmed by
increased light scattering based on A320/A260 ratios. The technique could be useful for monitoring the kinetics of aggregation for adenovirus and other DNA and RNA viruses
in the submicron region. Therefore, this novel assay provides a critical tool for purification development of viral vectors
for meeting therapeutic and research needs.
Received 18 September 1997/ Accepted in revised form 15 May 1998 相似文献
109.
110.
Astorga and Williams1 have demonstrated that leucocytes from some patients with rheumatoid arthritis (RA) have an impaired one-way mixed leucocyte reaction2 (MLR) when stimulated with leucocytes from other such patients. No definite explanation of this phenomenon is given. We have investigated other diseases in which auto-immune aetiology is suspected to see whether similar phenomena are associated with them. Here we report our investigations of multiple sclerosis (MS). 相似文献