全文获取类型
收费全文 | 585篇 |
免费 | 55篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 28篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 22篇 |
2017年 | 23篇 |
2016年 | 33篇 |
2015年 | 41篇 |
2014年 | 49篇 |
2013年 | 45篇 |
2012年 | 62篇 |
2011年 | 53篇 |
2010年 | 29篇 |
2009年 | 29篇 |
2008年 | 40篇 |
2007年 | 27篇 |
2006年 | 26篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 19篇 |
2002年 | 14篇 |
2001年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 6篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1932年 | 1篇 |
1910年 | 1篇 |
排序方式: 共有641条查询结果,搜索用时 15 毫秒
31.
32.
Canalization and developmental instability of the fetal skull in a mouse model of maternal nutritional stress 下载免费PDF全文
Paula N. Gonzalez Federico P. Lotto Benedikt Hallgrímsson 《American journal of physical anthropology》2014,154(4):544-553
Nutritional imbalance is one of the main sources of stress in both extant and extinct human populations. Restricted availability of nutrients is thought to disrupt the buffering mechanisms that contribute to developmental stability and canalization, resulting in increased levels of fluctuating asymmetry (FA) and phenotypic variance among individuals. However, the literature is contradictory in this regard. This study assesses the effect of prenatal nutritional stress on FA and among‐individual variance in cranial shape and size using a mouse model of maternal protein restriction. Two sets of landmark coordinates were digitized in three dimensions from skulls of control and protein restricted specimens at E17.5 and E18.5. We found that, by the end of gestation, maternal protein restriction resulted in a significant reduction of skull size. Fluctuating asymmetry in size and shape exceeded the amount of measurement error in all groups, but no significant differences in the magnitude of FA were found between treatments. Conversely, the pattern of shape asymmetry was affected by the environmental perturbation since the angles between the first eigenvectors extracted from the covariance matrix of shape asymmetric component of protein restricted and control groups were not significantly different from the expected for random vectors. In addition, among‐individual variance in cranial shape was significantly higher in the protein restricted than the control group at E18.5. Overall, the results obtained from a controlled experiment do not support the view of fluctuating asymmetry of cranial structures as a reliable index for inferring nutritional stress in human populations. Am J Phys Anthropol 154:544–553, 2014. © 2014 Wiley Periodicals, Inc. 相似文献
33.
34.
35.
The final step of FeMo cofactor (FeMoco) assembly involves the insertion of FeMoco into its binding site in the molybdenum-iron (MoFe) protein of nitrogenase. Here we examine the role of His alpha274 and His alpha451 of Azotobacter vinelandii MoFe protein in this process. Our results from combined metal, activity, EPR, stability and insertion analyses show that mutations of His alpha274 and/or His alpha451, two of the histidines that belong to a so-called His triad, to small uncharged Ala specifically reduce the accumulation of FeMoco in MoFe protein. This observation indicates that the enrichment of histidines at the His triad is important for FeMoco insertion and that the His triad potentially serves as an intermediate docking point for FeMoco through transitory ligand coordination and/or electrostatic interaction. 相似文献
36.
Parvovirus (PV) B19 is the causative agent of the childhood disease erythema infectiosum. An association of PV B19 with chronic
arthropathies, sometimes resembling rheumatoid arthritis or juvenile idiopathic arthritis (JIA), has repeatedly been described.
Other studies, however, have failed to identify any such relationship. In order to study further whether there is a link between
PV B19 and JIA, we determined the prevalence of PV B19 specific IgG antibodies in serum samples from children with rheumatoid
diseases and compared it with the prevalence in unaffected children We reasoned that if there is an association between PV
B19 and JIA, then the prevalence of PV B19 IgG in the children with JIA should be higher than in the control group. PV B19
IgG status was tested in 406 children with JIA and related diseases, and in 146 children constituting a control group. The
percentage of PV B19 IgG positive children was not significantly elevated in the disease subgroups compared with age-matched
control groups. In conclusion, our findings do not support the hypothesis that human parvovirus B19 is involved in the pathogenesis
of JIA. 相似文献
37.
Enni Markkanen Roman Fischer Marina Ledentcova Benedikt M. Kessler Grigory L. Dianov 《Nucleic acids research》2015,43(7):3667-3679
Genetic instability, provoked by exogenous mutagens, is well linked to initiation of cancer. However, even in unstressed cells, DNA undergoes a plethora of spontaneous alterations provoked by its inherent chemical instability and the intracellular milieu. Base excision repair (BER) is the major cellular pathway responsible for repair of these lesions, and as deficiency in BER activity results in DNA damage it has been proposed that it may trigger the development of sporadic cancers. Nevertheless, experimental evidence for this model remains inconsistent and elusive. Here, we performed a proteomic analysis of BER deficient human cells using stable isotope labelling with amino acids in cell culture (SILAC), and demonstrate that BER deficiency, which induces genetic instability, results in dramatic changes in gene expression, resembling changes found in many cancers. We observed profound alterations in tissue homeostasis, serine biosynthesis, and one-carbon- and amino acid metabolism, all of which have been identified as cancer cell ‘hallmarks’. For the first time, this study describes gene expression changes characteristic for cells deficient in repair of endogenous DNA lesions by BER. These expression changes resemble those observed in cancer cells, suggesting that genetically unstable BER deficient cells may be a source of pre-cancerous cells. 相似文献
38.
39.
40.
Dorothee Aydin Mikhail A Filippov Jakob-Andreas Tschäpe Norbert Gretz Marco Prinz Roland Eils Benedikt Brors Ulrike C Müller 《BMC genomics》2011,12(1):1-17