全文获取类型
收费全文 | 3202篇 |
免费 | 182篇 |
国内免费 | 4篇 |
出版年
2023年 | 8篇 |
2022年 | 27篇 |
2021年 | 64篇 |
2020年 | 22篇 |
2019年 | 43篇 |
2018年 | 62篇 |
2017年 | 58篇 |
2016年 | 71篇 |
2015年 | 136篇 |
2014年 | 140篇 |
2013年 | 201篇 |
2012年 | 244篇 |
2011年 | 209篇 |
2010年 | 132篇 |
2009年 | 132篇 |
2008年 | 193篇 |
2007年 | 198篇 |
2006年 | 172篇 |
2005年 | 189篇 |
2004年 | 152篇 |
2003年 | 138篇 |
2002年 | 127篇 |
2001年 | 59篇 |
2000年 | 71篇 |
1999年 | 56篇 |
1998年 | 30篇 |
1997年 | 21篇 |
1996年 | 28篇 |
1995年 | 22篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 22篇 |
1989年 | 28篇 |
1988年 | 33篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 16篇 |
1984年 | 18篇 |
1983年 | 7篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 17篇 |
1977年 | 7篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 6篇 |
1966年 | 5篇 |
排序方式: 共有3388条查询结果,搜索用时 15 毫秒
991.
992.
Computational modeling has been applied for data analysis in psychology, neuroscience, and psychiatry. One of its important uses is to infer the latent variables underlying behavior by which researchers can evaluate corresponding neural, physiological, or behavioral measures. This feature is especially crucial for computational psychiatry, in which altered computational processes underlying mental disorders are of interest. For instance, several studies employing model-based fMRI—a method for identifying brain regions correlated with latent variables—have shown that patients with mental disorders (e.g., depression) exhibit diminished neural responses to reward prediction errors (RPEs), which are the differences between experienced and predicted rewards. Such model-based analysis has the drawback that the parameter estimates and inference of latent variables are not necessarily correct—rather, they usually contain some errors. A previous study theoretically and empirically showed that the error in model-fitting does not necessarily cause a serious error in model-based fMRI. However, the study did not deal with certain situations relevant to psychiatry, such as group comparisons between patients and healthy controls. We developed a theoretical framework to explore such situations. We demonstrate that the parameter-misspecification can critically affect the results of group comparison. We demonstrate that even if the RPE response in patients is completely intact, a spurious difference to healthy controls is observable. Such a situation occurs when the ground-truth learning rate differs between groups but a common learning rate is used, as per previous studies. Furthermore, even if the parameters are appropriately fitted to individual participants, spurious group differences in RPE responses are observable when the model lacks a component that differs between groups. These results highlight the importance of appropriate model-fitting and the need for caution when interpreting the results of model-based fMRI. 相似文献
993.
Marina Pais Joe Win Kentaro Yoshida Graham J Etherington Liliana M Cano Sylvain Raffaele Mark J Banfield Alex Jones Sophien Kamoun Diane GO Saunders 《Genome biology》2013,14(6):211
Recent pathogenomic research on plant parasitic oomycete effector function and plant host responses has resulted in major conceptual advances in plant pathology, which has been possible thanks to the availability of genome sequences. 相似文献
994.
Colony-stimulating factor 1 expression is down-regulated during the adipocyte differentiation of H-1/A marrow stromal cells and induced by cachectin/tumor necrosis factor. 总被引:3,自引:0,他引:3
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A Umezawa K Tachibana K Harigaya S Kusakari S Kato Y Watanabe T Takano 《Molecular and cellular biology》1991,11(2):920-927
995.
The amino acid sequence of triculamin is established from the amino acid composition of the peptides, which have been obtained by partial acid hydrolysis. It is a branched peptides, and a possible structure of the branched parts is proposed. 相似文献
996.
997.
Although dedifferentiation, transformation of differentiated cells into progenitor cells, is a critical step in the regeneration of amphibians and fish, the molecular mechanisms underlying this process, including epigenetic changes, remain unclear. Dot blot assays and immunohistochemical analyses revealed that, during regeneration of zebrafish fin, the levels of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) are transiently reduced in blastema cells and cells adjacent to the amputation plane at 30 h post-amputation (hpa), and the level of 5mC, but not 5hmC, is almost restored by 72 hpa. We observed that the dedifferentiated cells showed reduced levels of 5mC and 5hmC independent of cell proliferation by 24 hpa. Furthermore, expressions of the proposed demethylation- and DNA repair-related genes were detected during fin regeneration. Taken together, our findings illustrate that the transient reduction of 5mC and 5hmC in dedifferentiated cells is associated with active demethylation during regeneration of zebrafish fin. 相似文献
998.
Louis Grandjean Tomotada Iwamoto Anna Lithgow Robert H Gilman Kentaro Arikawa Noriko Nakanishi Laura Martin Edith Castillo Valentina Alarcon Jorge Coronel Walter Solano Minoo Aminian Claudia Guezala Nalin Rastogi David Couvin Patricia Sheen Mirko Zimic David AJ Moore 《PloS one》2015,10(5)
BackgroundThe comparison of Mycobacterium tuberculosis bacterial genotypes with phenotypic, demographic, geospatial and clinical data improves our understanding of how strain lineage influences the development of drug-resistance and the spread of tuberculosis.MethodsTo investigate the association of Mycobacterium tuberculosis bacterial genotype with drug-resistance. Drug susceptibility testing together with genotyping using both 15-loci MIRU-typing and spoligotyping, was performed on 2,139 culture positive isolates, each from a different patient in Lima, Peru. Demographic, geospatial and socio-economic data were collected using questionnaires, global positioning equipment and the latest national census.ResultsThe Latin American Mediterranean (LAM) clade (OR 2.4, p<0.001) was significantly associated with drug-resistance and alone accounted for more than half of all drug resistance in the region. Previously treated patients, prisoners and genetically clustered cases were also significantly associated with drug-resistance (OR''s 2.5, 2.4 and 1.8, p<0.001, p<0.05, p<0.001 respectively).ConclusionsTuberculosis disease caused by the LAM clade was more likely to be drug resistant independent of important clinical, genetic and socio-economic confounding factors. Explanations for this include; the preferential co-evolution of LAM strains in a Latin American population, a LAM strain bacterial genetic background that favors drug-resistance or the "founder effect" from pre-existing LAM strains disproportionately exposed to drugs. 相似文献
999.
Jia-Min B. Pang David J. Byrne Elena A. Takano Nicholas Jene Lara Petelin Joanne McKinley Catherine Poliness Christobel Saunders Donna Taylor Gillian Mitchell Stephen B. Fox 《PloS one》2015,10(6)
Aim
To investigate the cellular and immunophenotypic basis of mammographic density in women at high risk of breast cancer.Methods
Mammograms and targeted breast biopsies were accrued from 24 women at high risk of breast cancer. Mammographic density was classified into Wolfe categories and ranked by increasing density. The histological composition and immunophenotypic profile were quantified from digitized haematoxylin and eosin-stained and immunohistochemically-stained (ERα, ERβ, PgR, HER2, Ki-67, and CD31) slides and correlated to mammographic density.Results
Increasing mammographic density was significantly correlated with increased fibrous stroma proportion (rs (22) = 0.5226, p = 0.0088) and significantly inversely associated with adipose tissue proportion (rs (22) = -0.5409, p = 0.0064). Contrary to previous reports, stromal expression of ERα was common (19/20 cases, 95%). There was significantly higher stromal PgR expression in mammographically-dense breasts (p=0.026).Conclusions
The proportion of stroma and fat underlies mammographic density in women at high risk of breast cancer. Increased expression of PgR in the stroma of mammographically dense breasts and frequent and unexpected presence of stromal ERα expression raises the possibility that hormone receptor expression in breast stroma may have a role in mediating the effects of exogenous hormonal therapy on mammographic density. 相似文献1000.
Takeshi Nishijima Misao Takano Shoko Matsumoto Miki Koyama Yuko Sugino Miwa Ogane Kazuko Ikeda Yoshimi Kikuchi Shinichi Oka Hiroyuki Gatanaga 《PloS one》2015,10(11)