全文获取类型
收费全文 | 289篇 |
免费 | 45篇 |
出版年
2022年 | 4篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 10篇 |
2012年 | 11篇 |
2011年 | 10篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 22篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 3篇 |
1962年 | 2篇 |
1961年 | 1篇 |
1960年 | 2篇 |
排序方式: 共有334条查询结果,搜索用时 390 毫秒
31.
Liliane?VenturaEmail author Gabriel?Torres?de Jesus Gunter?Camilo Dablas?de Oliveira Sidney?JF?Sousa 《Biomedical engineering online》2005,4(1):70
Background
The authors have developed a small portable device for the objective measurement of the transparency of corneas stored in preservative medium, for use by eye banks in evaluation prior to transplantation. 相似文献32.
RP Tucker K Drabikowski JF Hess J Ferralli R Chiquet-Ehrismann JC Adams 《BMC evolutionary biology》2006,6(1):60-17
Background
Tenascins are a family of glycoproteins found primarily in the extracellular matrix of embryos where they help to regulate cell proliferation, adhesion and migration. In order to learn more about their origins and relationships to each other, as well as to clarify the nomenclature used to describe them, the tenascin genes of the urochordate Ciona intestinalis, the pufferfish Tetraodon nigroviridis and Takifugu rubripes and the frog Xenopus tropicalis were identified and their gene organization and predicted protein products compared with the previously characterized tenascins of amniotes. 相似文献33.
Background
Trichomonosis caused by Trichomonas vaginalis is the number one, non-viral sexually transmitted disease (STD) that affects more than 250 million people worldwide. Immunoglobulin A (IgA) has been implicated in resistance to mucosal infections by pathogens. No reports are available of IgA-reactive proteins and the role, if any, of this class of antibody in the control of this STD. The availability of an IgA monoclonal antibody (mAb) immunoreactive to trichomonads by whole cell (WC)-ELISA prompted us to characterize the IgA-reactive protein of T. vaginalis. 相似文献34.
35.
Hershkovitz I Donoghue HD Minnikin DE Besra GS Lee OY Gernaey AM Galili E Eshed V Greenblatt CL Lemma E Bar-Gal GK Spigelman M 《PloS one》2008,3(10):e3426
Background
Mycobacterium tuberculosis is the principal etiologic agent of human tuberculosis. It has no environmental reservoir and is believed to have co-evolved with its host over millennia. This is supported by skeletal evidence of the disease in early humans, and inferred from M. tuberculosis genomic analysis. Direct examination of ancient human remains for M. tuberculosis biomarkers should aid our understanding of the nature of prehistoric tuberculosis and the host/pathogen relationship.Methodology/Principal Findings
We used conventional PCR to examine bone samples with typical tuberculosis lesions from a woman and infant, who were buried together in the now submerged site of Atlit-Yam in the Eastern Mediterranean, dating from 9250-8160 years ago. Rigorous precautions were taken to prevent contamination, and independent centers were used to confirm authenticity of findings. DNA from five M tuberculosis genetic loci was detected and had characteristics consistent with extant genetic lineages. High performance liquid chromatography was used as an independent method of verification and it directly detected mycolic acid lipid biomarkers, specific for the M. tuberculosis complex.Conclusions/Significance
Human tuberculosis was confirmed by morphological and molecular methods in a population living in one of the first villages with evidence of agriculture and animal domestication. The widespread use of animals was not a source of infection but may have supported a denser human population that facilitated transmission of the tubercle bacillus. The similarity of the M. tuberculosis genetic signature with those of today gives support to the theory of a long-term co-existence of host and pathogen. 相似文献36.
Citrate synthase (E.C. 4.1.3.7) has been isolated from bean mitochondria by an improved procedure. The purified enzyme had a specific activity of 50. In most respects (e.g. sedimentation constant, Kms, pH sensitivity and ionic strength inhibition) the enzyme is similar to that prepared from mammalian sources. The feature distinguishing the plant enzyme from the others was its inhibition by several sulfhydryl reagents. The substrates conferred either complete protection (acetyl coenzyme A) or partial protection (oxalacetic acid) against the inhibition. Dithiothreitol (DTT) was capable of partially reversing the inhibition. The efficacy of DTT varied with the sulfhydryl reagent and was inversely related to the period of incubation of the enzyme with the reagent. 相似文献
37.
Carney D. Matheson Kim K. Vernon Arlene Lahti Renee Fratpietro Mark Spigelman Shimon Gibson Charles L. Greenblatt Helen D. Donoghue 《PloS one》2009,4(12)
The Tomb of the Shroud is a first-century C.E. tomb discovered in Akeldama, Jerusalem, Israel that had been illegally entered and looted. The investigation of this tomb by an interdisciplinary team of researchers began in 2000. More than twenty stone ossuaries for collecting human bones were found, along with textiles from a burial shroud, hair and skeletal remains. The research presented here focuses on genetic analysis of the bioarchaeological remains from the tomb using mitochondrial DNA to examine familial relationships of the individuals within the tomb and molecular screening for the presence of disease. There are three mitochondrial haplotypes shared between a number of the remains analyzed suggesting a possible family tomb. There were two pathogens genetically detected within the collection of osteological samples, these were Mycobacterium tuberculosis and Mycobacterium leprae. The Tomb of the Shroud is one of very few examples of a preserved shrouded human burial and the only example of a plaster sealed loculus with remains genetically confirmed to have belonged to a shrouded male individual that suffered from tuberculosis and leprosy dating to the first-century C.E. This is the earliest case of leprosy with a confirmed date in which M. leprae DNA was detected. 相似文献
38.
39.
40.
Extreme differences in rates of molecular evolution of foraminifera revealed by comparison of ribosomal DNA sequences and the fossil record 总被引:8,自引:3,他引:5
Pawlowski J; Bolivar I; Fahrni JF; de Vargas C; Gouy M; Zaninetti L 《Molecular biology and evolution》1997,14(5):498-505
Foraminifera have one of the best known fossil records among the
unicellular eukaryotes. However, the origin and phylogenetic relationships
of the extant foraminiferal lineages are poorly understood. To test the
current paleontological hypotheses on evolution of foraminifera, we
sequenced about 1,000 base pairs from the 3' end of the small subunit rRNA
gene (SSU rDNA) in 22 species representing all major taxonomic groups.
Phylogenies were derived using neighbor- joining, maximum-parsimony, and
maximum-likelihood methods. All analyses confirm the monophyletic origin of
foraminifera. Evolutionary relationships within foraminifera inferred from
rDNA sequences, however, depend on the method of tree building and on the
choice of analyzed sites. In particular, the position of planktonic
foraminifera shows important variations. We have shown that these changes
result from the extremely high rate of rDNA evolution in this group. By
comparing the number of substitutions with the divergence times inferred
from the fossil record, we have estimated that the rate of rDNA evolution
in planktonic foraminifera is 50 to 100 times faster than in some benthic
foraminifera. The use of the maximum-likelihood method and limitation of
analyzed sites to the most conserved parts of the SSU rRNA molecule render
molecular and paleontological data generally congruent.
相似文献