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171.
Substrate preferences of human placental DNA methyltransferase investigated with synthetic polydeoxynucleotides 总被引:1,自引:0,他引:1
D Carotti F Palitti S Mastrantonio M Rispoli R Strom A Amato F Campagnari E P Whitehead 《Biochimica et biophysica acta》1986,866(2-3):135-143
A DNA methyltransferase partly purified from human placenta has been tested on a variety of synthetic polydeoxynucleotides. The results showed that: the enzyme is most active as a 'maintenance' or 'hemi-' methylase but also has some de novo methylating activity; the presence or absence of A or T in the substrate strand has little influence on maintenance or de novo activity, while polymers containing C but not G in the same strand are poor de novo substrates and bind poorly to the enzyme; single-stranded polymers are about as good substrates as double-stranded ones, and the effects of nucleotide composition (particularly G and mC content) on enzyme activity with single strands are similar to those with double-stranded polymers; strands in which all the cytosines are methylated bind the enzyme well. A mechanism is suggested involving two different sites on the enzyme that recognize CG and mCG, and which rationalizes the activity of eukaryotic DNA methyltransferases towards single-stranded DNA. 相似文献
172.
Summary The functionality of isolated brain microvessels — used as anin vitro model of the blood-brain barrier — can be influenced by interaction with cationic proteins. The various polylysines (Mr ranging from 0.9 to 180 kDa) tested affected the activity of both the Na+-dependent (A) and the Na+-independent (L) systems for neutral amino acid transport. Exposure to the 180 kDa polylysine caused a conspicuous inhibition of both transport systems, associated to an increased passive permeability. There was a constant, Mr-dependent, inhibition of the the L-system-mediated uptake of hydrophobic neutral amino acids. The activity of the A-system was enhanced, upon exposure to polymers larger than 22 kDa reaching its peak at 68 kDa and and declining at higher Mr values. The effect which was Na+-ions dependent and abolished by phloretine, could be essentially ascribed to an increased affinity of the MeAIB for its carrier (Km value decreasing from 265 to 169µM in presence of 68 kDa polylysine). 相似文献
173.
174.
Nicole Weisschuh Anja K. Mayer Tim M. Strom Susanne Kohl Nicola Gl?ckle Max Schubach Sten Andreasson Antje Bernd David G. Birch Christian P. Hamel John R. Heckenlively Samuel G. Jacobson Christina Kamme Ulrich Kellner Erdmute Kunstmann Pietro Maffei Charlotte M. Reiff Klaus Rohrschneider Thomas Rosenberg Günther Rudolph Rita Vámos Balázs Varsányi Richard G. Weleber Bernd Wissinger 《PloS one》2016,11(1)
Retinal dystrophies (RD) constitute a group of blinding diseases that are characterized by clinical variability and pronounced genetic heterogeneity. The different nonsyndromic and syndromic forms of RD can be attributed to mutations in more than 200 genes. Consequently, next generation sequencing (NGS) technologies are among the most promising approaches to identify mutations in RD. We screened a large cohort of patients comprising 89 independent cases and families with various subforms of RD applying different NGS platforms. While mutation screening in 50 cases was performed using a RD gene capture panel, 47 cases were analyzed using whole exome sequencing. One family was analyzed using whole genome sequencing. A detection rate of 61% was achieved including mutations in 34 known and two novel RD genes. A total of 69 distinct mutations were identified, including 39 novel mutations. Notably, genetic findings in several families were not consistent with the initial clinical diagnosis. Clinical reassessment resulted in refinement of the clinical diagnosis in some of these families and confirmed the broad clinical spectrum associated with mutations in RD genes. 相似文献
175.
Alma Kuechler Marjolein H. Willemsen Beate Albrecht Carlos A. Bacino Dennis W. Bartholomew Hans van Bokhoven Marie Jose H. van den Boogaard Nuria Bramswig Christian Büttner Kirsten Cremer Johanna Christina Czeschik Hartmut Engels Koen van Gassen Elisabeth Graf Mieke van Haelst Weimin He Jacob S. Hogue Marlies Kempers David Koolen Glen Monroe Sonja de Munnik Matthew Pastore André Reis Miriam S. Reuter David H. Tegay Joris Veltman Gepke Visser Peter van Hasselt Eric E. J. Smeets Lisenka Vissers Thomas Wieland Willemijn Wissink Helger Yntema Alexander Michael Zink Tim M. Strom Hermann-Josef Lüdecke Tjitske Kleefstra Dagmar Wieczorek 《Human genetics》2015,134(1):97-109
176.
177.
P Caiafa S Mastrantonio F Cacace M Attinà M Rispoli R Strom 《Biochimica et biophysica acta》1988,951(1):191-200
In human placenta, the DNA of all subfractions of the third level of chromatin organization exhibits similar values of the methylcytosine-to-cytosine ratio. The tightly bound form of DNA methyltransferase is mostly recovered in the 'stripped loop' fraction, although, on the basis of the DNA content, the 'stripped loops' and the 'stripped matrix' appear to possess a similar amount of the enzyme. DNA methyltransferase activity is instead totally absent from the 'digested matrix', i.e., from the fraction remaining after digestion of the 'stripped matrix' with DNAase I. Upon addition of exogenous DNA methyltransferase, however, the DNA of this fraction, which is only 1% (in weight) of the total chromatin DNA and which has a length of approx. 9 kbp, can readily undergo methylation. 相似文献
178.
179.
Induction of calbindin-D 9k mRNA but not calcium transport in rat intestine by 1,25-dihydroxyvitamin D3 24-homologs 总被引:2,自引:0,他引:2
J Krisinger M Strom H D Darwish K Perlman C Smith H F DeLuca 《The Journal of biological chemistry》1991,266(3):1910-1913
The function and precise mechanism of regulation of calbindin-D 9k in intestine is largely unknown. It is suggested that this calcium binding protein is involved in active intestinal calcium transport and that its expression is mainly mediated by 1,25-dihydroxyvitamin D3. We examined the effect of two side chain modified analogs of 1,25-dihydroxyvitamin D3 as compared to 1,25-dihydroxyvitamin D3 itself on the regulation of the calbindin-D 9k at the mRNA level and on intestinal calcium transport in the rat. delta 22-24,24-dihomo-1,25-dihydroxyvitamin D3 at a single dose of 500, 1,000, and 2,000 pmol caused greater than 7.0-fold increase in calbindin-D 9k mRNA without stimulating intestinal calcium transport. A 10,000-pmol dose of delta 22-24,24,24-trihomo-1,25-dihydroxyvitamin D3 caused a 7.6-fold increase in calbindin-D 9k mRNA without significantly increasing intestinal absorption of calcium. In contrast, 1,25-dihydroxyvitamin D3 caused a parallel increase in calbindin-D 9k mRNA and intestinal absorption of calcium. Thus, calbindin 9k is not by itself responsible for 1,25-dihydroxyvitamin D3-mediated increase in intestinal absorption of calcium. 相似文献
180.