全文获取类型
收费全文 | 868篇 |
免费 | 68篇 |
国内免费 | 2篇 |
出版年
2023年 | 1篇 |
2022年 | 13篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 13篇 |
2017年 | 8篇 |
2016年 | 20篇 |
2015年 | 29篇 |
2014年 | 38篇 |
2013年 | 33篇 |
2012年 | 47篇 |
2011年 | 88篇 |
2010年 | 46篇 |
2009年 | 39篇 |
2008年 | 55篇 |
2007年 | 58篇 |
2006年 | 47篇 |
2005年 | 44篇 |
2004年 | 53篇 |
2003年 | 56篇 |
2002年 | 34篇 |
2001年 | 16篇 |
2000年 | 22篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有938条查询结果,搜索用时 31 毫秒
31.
Interaction of Insulin-Like Growth Factor-Binding Protein 2 with α2-Macroglobulin in the Circulation
Insulin-like growth factors (IGFs) play active role in mitogenic and metabolic processes. In the peripheral circulation, they are mostly bound to specific IGF-binding proteins (IGFBPs). Proteolysis of IGFBPs releases free, active IGFs. IGFBP-2 is the second most abundant of the six binding proteins and its concentration increases in catabolic states. The possible interaction between IGFBP-2 and other proteins in the circulation was investigated in this study. Our results showed that IGFBP-2 associates with α2-macroglobulin (α2M), a protease inhibitor. Formation of IGFBP-2/α2M complexes most likely contributes to the regulation of IGFBP-2 proteolysis and, thus, the activity of IGFs. 相似文献
32.
Olympe Chazara Chi-Sheng Chang Nicolas Bruneau Khalid Benabdeljelil Jean-Claude Fotsa Boniface B. Kayang N’Goran E. Loukou Richard Osei-Amponsah Valentine Yapi-Gnaore Issaka A. K. Youssao Chih-Feng Chen Marie-Hélène Pinard-van der Laan Michèle Tixier-Boichard Bertrand Bed’Hom 《Immunogenetics》2013,65(6):447-459
The chicken major histocompatibility complex (MHC) is located on the microchromosome 16 and is described as the most variable region in the genome. The genes of the MHC play a central role in the immune system. Particularly, genes encoding proteins involved in the antigen presentation to T cells. Therefore, describing the genetic polymorphism of this region is crucial in understanding host–pathogen interactions. The tandem repeat LEI0258 is located within the core area of the B region of the chicken MHC (MHC-B region) and its genotypes correlate with serology. This marker was used to provide a picture of the worldwide diversity of the chicken MHC-B region and to categorize chicken MHC haplotypes. More than 1,600 animals from 80 different populations or lines of chickens from Africa, Asia, and Europe, including wild fowl species, were genotyped at the LEI0258 locus. Fifty novel alleles were described after sequencing. The resulting 79 alleles were classified into 12 clusters, based on the SNPs and indels found within the sequences flanking the repeats. Furthermore, hypotheses were formulated on the evolutionary dynamics of the region. This study constitutes the largest variability report for the chicken MHC and establishes a framework for future diversity or association studies. 相似文献
33.
34.
35.
The YUMM lines: a series of congenic mouse melanoma cell lines with defined genetic alterations 下载免费PDF全文
Katrina Meeth Jake Xiao Wang Goran Micevic William Damsky Marcus W. Bosenberg 《Pigment cell & melanoma research》2016,29(5):590-597
The remarkable success of immune therapies emphasizes the need for immune‐competent cancer models. Elegant genetically engineered mouse models of a variety of cancers have been established, but their effective use is limited by cost and difficulties in rapidly generating experimental data. Some mouse cancer cell lines are transplantable to immunocompetent host mice and have been utilized extensively to study cancer immunology. Here, we describe the Yale University Mouse Melanoma (YUMM) lines, a comprehensive system of mouse melanoma cell lines that are syngeneic to C57BL/6, have well‐defined human‐relevant driver mutations, and are genomically stable. This will be a useful tool for the study of tumor immunology and genotype‐specific cancer biology. 相似文献
36.
Natasa M. Milic Goran Z. Trajkovic Zoran M. Bukumiric Andja Cirkovic Ivan M. Nikolic Jelena S. Milin Nikola V. Milic Marko D. Savic Aleksandar M. Corac Jelena M. Marinkovic Dejana M. Stanisavljevic 《PloS one》2016,11(2)
Background
Although recent studies report on the benefits of blended learning in improving medical student education, there is still no empirical evidence on the relative effectiveness of blended over traditional learning approaches in medical statistics. We implemented blended along with on-site (i.e. face-to-face) learning to further assess the potential value of web-based learning in medical statistics.Methods
This was a prospective study conducted with third year medical undergraduate students attending the Faculty of Medicine, University of Belgrade, who passed (440 of 545) the final exam of the obligatory introductory statistics course during 2013–14. Student statistics achievements were stratified based on the two methods of education delivery: blended learning and on-site learning. Blended learning included a combination of face-to-face and distance learning methodologies integrated into a single course.Results
Mean exam scores for the blended learning student group were higher than for the on-site student group for both final statistics score (89.36±6.60 vs. 86.06±8.48; p = 0.001) and knowledge test score (7.88±1.30 vs. 7.51±1.36; p = 0.023) with a medium effect size. There were no differences in sex or study duration between the groups. Current grade point average (GPA) was higher in the blended group. In a multivariable regression model, current GPA and knowledge test scores were associated with the final statistics score after adjusting for study duration and learning modality (p<0.001).Conclusion
This study provides empirical evidence to support educator decisions to implement different learning environments for teaching medical statistics to undergraduate medical students. Blended and on-site training formats led to similar knowledge acquisition; however, students with higher GPA preferred the technology assisted learning format. Implementation of blended learning approaches can be considered an attractive, cost-effective, and efficient alternative to traditional classroom training in medical statistics. 相似文献37.
Troy E. Sandberg Christopher P. Long Jacqueline E. Gonzalez Adam M. Feist Maciek R. Antoniewicz Bernhard O. Palsson 《PloS one》2016,11(3)
13C-Metabolic flux analysis (13C-MFA) traditionally assumes that kinetic isotope effects from isotopically labeled compounds do not appreciably alter cellular growth or metabolism, despite indications that some biochemical reactions can be non-negligibly impacted. Here, populations of Escherichia coli were adaptively evolved for ~1000 generations on uniformly labeled 13C-glucose, a commonly used isotope for 13C-MFA. Phenotypic characterization of these evolved strains revealed ~40% increases in growth rate, with no significant difference in fitness when grown on either labeled (13C) or unlabeled (12C) glucose. The evolved strains displayed decreased biomass yields, increased glucose and oxygen uptake, and increased acetate production, mimicking what is observed after adaptive evolution on unlabeled glucose. Furthermore, full genome re-sequencing revealed that the key genetic changes underlying these phenotypic alterations were essentially the same as those acquired during adaptive evolution on unlabeled glucose. Additionally, glucose competition experiments demonstrated that the wild-type exhibits no isotopic preference for unlabeled glucose, and the evolved strains have no preference for labeled glucose. Overall, the results of this study indicate that there are no significant differences between 12C and 13C-glucose as a carbon source for E. coli growth. 相似文献
38.
Historically, the lacZ gene is one of the most universally used reporters of gene expression in molecular biology. Its activity can be quantified using an artificial substrate, o-nitrophenyl-ß-d-galactopyranoside (ONPG). However, the traditional method for measuring LacZ activity (first described by J. H. Miller in 1972) can be challenging for a large number of samples, is prone to variability, and involves hazardous compounds for lysis (e.g., chloroform, toluene). 相似文献
39.
40.
Stphanie Sherpa Maya Guguen Julien Renaud Michael G. B. Blum Thierry Gaude Frdric Laporte Mustafa Akiner Bulent Alten Carles Aranda Hlne Barre‐Cardi Romeo Bellini Mikel Bengoa Paulis Xiao‐Guang Chen Roger Eritja Eleonora Flacio Cipriano Foxi Intan H. Ishak Katja Kalan Shinji Kasai Fabrizio Montarsi Igor Pajovi Duan Petri Rosa Termine Nataa Turi Gonzalo M. Vazquez‐Prokopec Enkelejda Velo Goran Vignjevi Xiaohong Zhou Laurence Desprs 《Ecology and evolution》2019,9(22):12658-12675
Invasive species can encounter environments different from their source populations, which may trigger rapid adaptive changes after introduction (niche shift hypothesis). To test this hypothesis, we investigated whether postintroduction evolution is correlated with contrasting environmental conditions between the European invasive and source ranges in the Asian tiger mosquito Aedes albopictus. The comparison of environmental niches occupied in European and source population ranges revealed more than 96% overlap between invasive and source niches, supporting niche conservatism. However, we found evidence for postintroduction genetic evolution by reanalyzing a published ddRADseq genomic dataset from 90 European invasive populations using genotype–environment association (GEA) methods and generalized dissimilarity modeling (GDM). Three loci, among which a putative heat‐shock protein, exhibited significant allelic turnover along the gradient of winter precipitation that could be associated with ongoing range expansion. Wing morphometric traits weakly correlated with environmental gradients within Europe, but wing size differed between invasive and source populations located in different climatic areas. Niche similarities between source and invasive ranges might have facilitated the establishment of populations. Nonetheless, we found evidence for environmental‐induced adaptive changes after introduction. The ability to rapidly evolve observed in invasive populations (genetic shift) together with a large proportion of unfilled potential suitable areas (80%) pave the way to further spread of Ae. albopictus in Europe. 相似文献