全文获取类型
收费全文 | 370篇 |
免费 | 46篇 |
专业分类
416篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 10篇 |
2019年 | 20篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 18篇 |
2014年 | 26篇 |
2013年 | 23篇 |
2012年 | 34篇 |
2011年 | 41篇 |
2010年 | 32篇 |
2009年 | 23篇 |
2008年 | 28篇 |
2007年 | 25篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1956年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有416条查询结果,搜索用时 15 毫秒
1.
An unselected series of spontaneous abortions and their mothers were karyotyped with Q-bands to obtain a frequency of twin conceptions lost during the first trimester. Among 661 spontaneous abortions, 15 twin pairs were identified including two sets of conjoined twins. Analysis of Q-band variants permitted the exclusion of cases with two cell lines that could be attributed to maternal contamination or mosaicism. The twinning rate among spontaneous abortions was 1/44 compared with 1/103 live births and stillbirths in the Ontario population. If Weinberg's differential method is applied to these data, the frequency would be as high as 1/30 under the assumption that the incidence of monozygotic twins among abortions is the same as that for live births. 相似文献
2.
The purpose of this study has been to obtain information on the development of the envelop of horny cells that resists the action of keratinolytic agents. Toward this end the epidermis, oral mucosa, and tongue epithelium of various vertebrates, as well as the isolated envelopes of horny cells, were examined by electron microscopy. It was found that small cytoplasmic granules (1,000 to 5,000 A) that develop within differentiating epithelial cells move toward the cell periphery, and after fusion with the plasma membrane, empty their contents into the intercellular spaces. The content of the granules spreads over the cell surfaces, and subsequently a thickened and coated cell envelope is formed that resists the action of keratinolytic agent. The membrane-coating granule is regarded as a specific differentiation product of the keratinizing epithelium. It contains numerous inner membranes and is assumed to engage in synthetic activities such as, perhaps, the formation of polysaccharides. 相似文献
3.
S. Yu J. Mulley D. Loesch G. Turner A. Donnelly A. Gedeon D. Hillen E. Kremer M. Lynch M. Pritchard G. R. Sutherland R. I. Richards 《American journal of human genetics》1992,50(5):968-980
The fragile site at Xq27.3 is an unstable microsatellite repeat, p(CCG)n. In fragile-X syndrome pedigrees, this sequence exhibits variable amplification, the length of which correlates with fragile-site expression. There is a direct relationship between increased p(CCG)n copy number and propensity for instability: individuals having large amplifications exhibit somatic variation due to increased instability. The instability of the p(CCG)n repeat, when transmitted through affected pedigrees, explains the unusual segregation patterns of fragile-X phenotype, referred to as the Sherman paradox. All individuals of fragile-X genotype were found (where testing was possible) to have a parent with amplified p(CCG)n repeat, indicating that few, if any, cases of fragile-X syndrome are not familial. 相似文献
4.
Refined genetic localization for central core disease 总被引:4,自引:3,他引:1
J. C. Mulley H. M. Kozman H. A. Phillips A. K. Gedeon J. A. McCure D. E. Iles R. G. Gregg K. Hogan F. J. Couch D. H. MacLennan E. A. Haan 《American journal of human genetics》1993,52(2):398-405
Central core disease (CCO) is an autosomal dominant myopathy clinically distinct from malignant hyperthermia (MHS). In a large kindred in which the gene for CCO is segregating, two-point linkage analysis gave a maximum lod score, between the central core disease locus (CCO) and the ryanodine receptor locus (RYR1), of 11.8, with no recombination. Mutation within RYR1 is responsible for MHS, and RYR1 is also a candidate locus for CCO. A combination of physical mapping using a radiation-induced human-hamster hybrid panel and of multipoint linkage analysis using the Centre d'Etude du Polymorphisme Humain families established the marker order and sex-average map distances (in centimorgans) on the background map as D19S75–(5.2)–D19S9–(3.4)–D19S191–(2.2)–RYR1–(1.7)–D19S190–(1.6)-D19S47–(2.0)–CYP2B. Recombination was observed between CCO and the markers flanking RYR1. These linkage data are consistent with the hypothesis that CCO and RYR1 are allelic. The most likely position for CCO is near RYR1, with a multipoint lod score of 11.4, in 19q13.1 between D19S191 and D19S190, within the same interval as MHS (RYR1). 相似文献
5.
Summary In a study of 514 spontaneous abortions, 194 were found to have a chromosome anomaly. Of these, 4 (2.1%) were unbalanced translocations. Three of the translocations were Robertsonian (13q14q) and one was reciprocal. Each translocation was ascertained independently and each was associated with a balanced rearrangement in a carrier parent. 相似文献
6.
C. C. Lin M. M. Gedeon P. Griffith W. K. Smink D. R. Newton L. Wilkie L. M. Sewell 《Human genetics》1976,31(3):315-328
Summary Chromosome analysing using quinacrine fluorescence was performed on 930 consecutive newborn infants. The total incidence of major chromosome aberrations including numerical changes of the sex chromosomes, and structural changes of autosomes, was 0.54%. Incidences of XYY (0.4%) and XXY (0.2%) were relatively higher as compared to other studies. About 0.75% of the newborn infants were found to have a variable bright fluorescent band located on the proximal area of the short arm (p11) rather than on the proximal long arm (q11) of chromosome No. 3. Attempts were also made to record the variable fluorescent regions on 7 autosomes and the Y chromosome. 相似文献
7.
Zhang SL Kozak JA Jiang W Yeromin AV Chen J Yu Y Penna A Shen W Chi V Cahalan MD 《The Journal of biological chemistry》2008,283(25):17662-17671
We evaluated currents induced by expression of human homologs of Orai together with STIM1 in human embryonic kidney cells. When co-expressed with STIM1, Orai1 induced a large inwardly rectifying Ca(2+)-selective current with Ca(2+)-induced slow inactivation. A point mutation of Orai1 (E106D) altered the ion selectivity of the induced Ca(2+) release-activated Ca(2+) (CRAC)-like current while retaining an inwardly rectifying I-V characteristic. Expression of the C-terminal portion of STIM1 with Orai1 was sufficient to generate CRAC current without store depletion. 2-APB activated a large relatively nonselective current in STIM1 and Orai3 co-expressing cells. 2-APB also induced Ca(2+) influx in Orai3-expressing cells without store depletion or co-expression of STIM1. The Orai3 current induced by 2-APB exhibited outward rectification and an inward component representing a mixed calcium and monovalent current. A pore mutant of Orai3 inhibited store-operated Ca(2+) entry and did not carry significant current in response to either store depletion or addition of 2-APB. Analysis of a series of Orai1-3 chimeras revealed the structural determinant responsible for 2-APB-induced current within the sequence from the second to third transmembrane segment of Orai3. The Orai3 current induced by 2-APB may reflect a store-independent mode of CRAC channel activation that opens a relatively nonselective cation pore. 相似文献
8.
Andriy I. Vovk Lyudmyla A. Kononets Vsevolod Yu. Tanchuk Sergiy O. Cherenok Andriy B. Drapailo Vitaly I. Kalchenko Valery P. Kukhar 《Bioorganic & medicinal chemistry letters》2010,20(2):483-487
Inhibition of Yersinia protein tyrosine phosphatase by calix[4]arene mono-, bis-, and tetrakis(methylenebisphosphonic) acids as well as calix[4]arene and thiacalix[4]arene tetrakis(methylphosphonic) acids have been investigated. The kinetic studies revealed that some compounds in this class are potent competitive inhibitors of Yersinia PTP with inhibition constants in the low micromolar range. The binding modes of macrocyclic phosphonate derivatives in the enzyme active center have been explained using computational docking approach. The results obtained indicate that calix[4]arenes are promising scaffolds for the development of inhibitors of Yersinia PTP. 相似文献
9.
Ljubov Dzanaeva Barbara Kruk Justyna Ruchala Jens Nielsen Andriy Sibirny Kostyantyn Dmytruk 《Cell biology international》2020,44(8):1606-1615
Xylose is a second‐most abounded sugar after glucose in lignocellulosic hydrolysates and should be efficiently fermented for economically viable second‐generation ethanol production. Despite significant progress in metabolic and evolutionary engineering, xylose fermentation rate of recombinant Saccharomyces cerevisiae remains lower than that for glucose. Our recent study demonstrated that peroxisome‐deficient cells of yeast Ogataea polymorpha showed a decrease in ethanol production from xylose. In this work, we have studied the role of peroxisomes in xylose alcoholic fermentation in the engineered xylose‐utilizing strain of S. cerevisiae. It was shown that peroxisome‐less pex3Δ mutant possessed 1.5‐fold decrease of ethanol production from xylose. We hypothesized that peroxisomal catalase Cta1 may have importance for hydrogen peroxide, the important component of reactive oxygen species, detoxification during xylose alcoholic fermentation. It was clearly shown that CTA1 deletion impaired ethanol production from xylose. It was found that enhancing the peroxisome population by modulation the peroxisomal biogenesis by overexpression of PEX34 activates xylose alcoholic fermentation. 相似文献
10.
Kostyantyn V. Dmytruk Justyna Ruchala Daria V. Fedorovych Roman D. Ostapiv Andriy A. Sibirny 《Biotechnology journal》2020,15(7)
Riboflavin (vitamin B2) is an indispensable nutrient for humans and animals, since it is the precursor of the essential coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), involved in variety of metabolic reactions. Riboflavin is produced on commercial scale and is used for feed and food fortification purposes, and in medicine. Until recently, the mutant strains of the flavinogenic yeast Candida famata were used in industry for riboflavin production. Guanosine triphosphate is the immediate precursor of riboflavin synthesis. Therefore, the activation of metabolic flux toward purine nucleotide biosynthesis is a promising approach to improve riboflavin production. The phosphoribosyl pyrophosphate synthetase and phosphoribosyl pyrophosphate amidotransferase are the rate limiting enzymes in purine biosynthesis. Corresponding genes PRS3 and ADE4 from yeast Debaryomyces hansenii are modified to avoid feedback inhibition and cooverexpressed on the background of a previously constructed riboflavin overproducing strain of C. famata. Constructed strain accumulates twofold more riboflavin when compared to the parental strain. 相似文献