全文获取类型
收费全文 | 182篇 |
免费 | 24篇 |
出版年
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 29篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 6篇 |
2005年 | 13篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1992年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1971年 | 2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206条查询结果,搜索用时 31 毫秒
121.
122.
Frédéric D Chevalier Claudia LL Valentim Philip T LoVerde Timothy JC Anderson 《BMC genomics》2014,15(1)
Background
Identification of parasite genes that underlie traits such as drug resistance and host specificity is challenging using classical linkage mapping approaches. Extreme QTL (X-QTL) methods, originally developed by rodent malaria and yeast researchers, promise to increase the power and simplify logistics of linkage mapping in experimental crosses of schistosomes (or other helminth parasites), because many 1000s of progeny can be analysed, phenotyping is not required, and progeny pools rather than individuals are genotyped. We explored the utility of this method for mapping a drug resistance gene in the human parasitic fluke Schistosoma mansoni.Results
We staged a genetic cross between oxamniquine sensitive and resistant parasites, then between two F1 progeny, to generate multiple F2 progeny. One group of F2s infecting hamsters was treated with oxamniquine, while a second group was left untreated. We used exome capture to reduce the size of the genome (from 363 Mb to 15 Mb) and exomes from pooled F2 progeny (treated males, untreated males, treated females, untreated females) and the two parent parasites were sequenced to high read depth (mean = 95-366×) and allele frequencies at 14,489 variants compared. We observed dramatic enrichment of alleles from the resistant parent in a small region of chromosome 6 in drug-treated male and female pools (combined analysis: = 11.07, p = 8.74 × 10-29). This region contains Smp_089320 a gene encoding a sulfotransferase recently implicated in oxamniquine resistance using classical linkage mapping methods.Conclusions
These results (a) demonstrate the utility of exome capture for generating reduced representation libraries in Schistosoma mansoni, and (b) provide proof-of-principle that X-QTL methods can be successfully applied to an important human helminth. The combination of these methods will simplify linkage analysis of biomedically or biologically important traits in this parasite.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-617) contains supplementary material, which is available to authorized users. 相似文献123.
124.
125.
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
126.
Whitney J. Cowell David C. Bellinger Brent A. Coull Chris Gennings Robert O. Wright Rosalind J. Wright 《PloS one》2015,10(11)
Background
Whether fetal neurodevelopment is disrupted by traffic-related air pollution is uncertain. Animal studies suggest that chemical and non-chemical stressors interact to impact neurodevelopment, and that this association is further modified by sex.Objectives
To examine associations between prenatal traffic-related black carbon exposure, prenatal stress, and sex with children’s memory and learning.Methods
Analyses included N = 258 mother-child dyads enrolled in a Boston, Massachusetts pregnancy cohort. Black carbon exposure was estimated using a validated spatiotemporal land-use regression model. Prenatal stress was measured using the Crisis in Family Systems-Revised survey of negative life events. The Wide Range Assessment of Memory and Learning (WRAML2) was administered at age 6 years; outcomes included the General Memory Index and its component indices [Verbal, Visual, and Attention Concentration]. Relationships between black carbon and WRAML2 index scores were examined using multivariable-adjusted linear regression including effect modification by stress and sex.Results
Mothers were primarily minorities (60% Hispanic, 26% Black); 67% had ≤12 years of education. The main effect for black carbon was not significant for any WRAML2 index; however, in stratified analyses, among boys with high exposure to prenatal stress, Attention Concentration Index scores were on average 9.5 points lower for those with high compared to low prenatal black carbon exposure (P 3-way interaction = 0.04).Conclusion
The associations between prenatal exposure to black carbon and stress with children’s memory scores were stronger in boys than in girls. Studies assessing complex interactions may more fully characterize health risks and, in particular, identify vulnerable subgroups. 相似文献127.
The population of Stephanodiscus rotula in a temperate eutrophic lake was studied over a 2 month period (January to early March). Although during the study period nutrient concentrations in the lake water remained far in excess of phytoplankton requirements, no notable increase in chlorophyll levels was recorded. This suggests that algae were limited by shortage of light and low temperatures. Frequency distribution analysis of cell diameters showed a dramatic size reduction at the end of winter, followed by restoration of higher values by early spring. Electron probe X-ray microanalysis spectra from Stephanodiscus cells routinely showed peaks of Ca, K, Si, P, S, Fe, Al, Mn, Mg, Na and Cl, with substantial variation in elemental concentrations both between and within samples. End-of-winter reduction in the cell size coincided with a considerable depletion of intracellular chemical levels of Si, P, Cl and K and could be related to the concurrent decrease in dissolved organic C and increase in intracellular Al. Correlation and factor analysis of intracellular elemental concentrations showed that statistical elemental associations within Stephanodiscus cells were mainly determined by three factors, with P, Cl, Si and K showing higher loadings on the first, Ca, Mn and S on the second, and Fe, Ca and Al on the third factor. Significant correlations among the elements of the first association may indicate the importance of P (ATP), K (through involvement in P metabolism) and Cl (possibly charge balance) in the active Si uptake during the study period. 相似文献
128.
Diatoms are frequently used as indicators of eutrophication in temperate systems, but little is known about their application
to impacted African tropical systems. Five streams located within Gombe Stream National Park and five streams supporting human
settlements draining into Lake Tanganyika, East Africa, were investigated for species composition, richness and diversity
of epilithic algae. In addition, a trophic diatom index (TDI) developed for monitoring European rivers was applied to these
tropical systems. 54 specific and infraspecific diatom taxa representing 20 genera were identified for all sites with Achnanthes s.l., Gomphonema and Navicula s.l. being the most common genera. Species richness varied between 10 and 21 in disturbed streams and 13 and 19 in undisturbed
streams. Nutrients were significantly enriched in streams draining the deforested watersheds but indices of diversity and
evenness (Shannon H, J and Simpson–Yule D, E) did not show any significant differences between streams in forested and deforested
watersheds. Significant differences were observed between pooled data for the TDI between forested and deforested watersheds.
Analysis of percent pollution tolerant diatom taxa indicates that organic pollution of streams in deforested watersheds may
be contributing to eutrophication. This study shows that African diatoms, cosmopolitan or resembling well-known North American
and European taxa, allows for trophic indices tailored to the autecological preferences of species to be applied to new regions,
although intensive studies on these African taxa will lead to more accurate results. Measures of species-richness and diversity,
historically used to describe the state of an ecosystem, may not be suitable to evaluate streams which are not grossly polluted.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
129.
Raman AV Pitts MW Seyedali A Hashimoto AC Seale LA Bellinger FP Berry MJ 《Genes, Brain & Behavior》2012,11(5):601-613
Dietary selenium restriction in mammals causes bodily selenium to be preferentially retained in the brain relative to other organs. Almost all the known selenoproteins are found in brain, where expression is facilitated by selenocysteine (Sec)-laden selenoprotein P. The brain also expresses selenocysteine lyase (Scly), an enzyme that putatively salvages Sec and recycles the selenium for selenoprotein translation. We compared mice with a genetic deletion of Scly to selenoprotein P (Sepp1) knockout mice for similarity of neurological impairments and whether dietary selenium modulates these parameters. We report that Scly knockout mice do not display neurological dysfunction comparable to Sepp1 knockout mice. Feeding a low-selenium diet to Scly knockout mice revealed a mild spatial learning deficit without disrupting motor coordination. Additionally, we report that the neurological phenotype caused by the absence of Sepp1 is exacerbated in male vs. female mice. These findings indicate that Sec recycling via Scly becomes limiting under selenium deficiency and suggest the presence of a complementary mechanism for processing Sec. Our studies illuminate the interaction between Sepp1 and Scly in the distribution and turnover of body and brain selenium and emphasize the consideration of sex differences when studying selenium and selenoproteins in vertebrate biology. 相似文献
130.
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