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排序方式: 共有137条查询结果,搜索用时 15 毫秒
31.
Hee Chun Jeong Nam Sook Kang No-Joong Park Eul Kyun Yum Young-Sik Jung 《Bioorganic & medicinal chemistry letters》2009,19(4):1214-1217
For the purpose of developing new oxime reactivators of acetylcholinesterases (AChE) that have been inhibited by organophosphorus agents, emphasis was given to the finding that the lipophilic nature of fluorinated compounds is responsible for their enhanced transport across the blood brain barrier (BBB). As a result, we have designed and synthesized the fluorinated oxime derivatives, which quantum mechanical calculations suggest should have a greater lipophilicity and BBB permeability than their non-fluorinated analogs. Among the compounds explored in this study, 4 was found to have the highest potency for reactivation of paraoxon-inhibited housefly (HF) AChE. 相似文献
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34.
In four experiments, we examined the effects on the affiliative preferences of 'focal' female Japanese quail given the opportunity to watch a conspecific male interact with a 'model' female. Experiments were conducted in three, 10-min phases: (1) a pretest, during which a 'focal' female chose between two males; (2) an observation phase, when each focal female watched the male she had spent less time near during the pretest (her 'nonpreferred' male) interact with a 'model' quail; and (3) a post-test, during which each focal female again chose between her nonpreferred and preferred males. Focal females increased their preferences for nonpreferred males after seeing them together with a model female (but not a model male), even if the nonpreferred male and model female were separated by an opaque barrier that prevented them from interacting. A focal female's preference for the end of the enclosure containing her nonpreferred male was not increased when she either watched him court a concealed model female or watched a model female that was being courted by him. Taken together, the present results suggest that a simple tendency for females to approach areas where they have previously seen a male and female quail, in preference to locations where they have seen only a male quail, can explain some of the effect of watching a nonpreferred male mate on a female's tendency to affiliate with him. However, focal females also showed enhanced preferences for nonpreferred males they had seen mating after we both moved those males and controlled for effects of transposition. Thus, processes akin to both 'mate choice copying' and 'conspecific cueing' remain viable explanations for the increase in a focal female quail's tendency to affiliate with a male she watched mate with another female. Copyright 1999 The Association for the Study of Animal Behaviour. 相似文献
35.
In growing Escherichia coli K12 cells, the cryptic bgl operon is activated
98% of the time by insertions of IS1 or IS5 into the control region,
designated bglR. The activated bgl operon permits utilization of the
beta-glucoside sugar arbutin as a sole carbon and energy source. The bgl
operon is also activated by late-occurring mutations during prolonged
selection on arbutin. The late-occurring mutations that occurred during
prolonged carbon starvation in the presence of arbutin were "adaptive
mutations" because they were specific to the presence of arbutin, and they
did not occur during prolonged starvation in the absence of arbutin. The
spectrum of late-arising mutations differed from that of early-arising,
growth-dependent mutations in that 20% of the late-arising mutants resulted
from mutations at the hns locus. This provides the first direct evidence
for adaptive mutagenesis mediated by the insertion of IS elements. Because
no special genetic background is required to select Bgl+ mutants, this
affords the opportunity to study IS-element-mediated adaptive mutagenesis
in a variety of genetic backgrounds, including the backgrounds of natural
isolates of E. coli.
相似文献
36.
Jain RK; Piskorz CF; Huang BG; Locke RD; Han HL; Koenig A; Varki A; Matta KL 《Glycobiology》1998,8(7):707-717
The selectins interact in important normal and pathological situations with
certain sialylated, fucosylated glycoconjugate ligands containing sialyl
Lewisx(Neu5Acalpha2-3Galbeta1-4(Fucalpha1-3)GlcN Ac). Much effort has gone
into the synthesis of sialylated and sulfated Lewisxanalogs as competitive
ligands for the selectins. Since the natural selectin ligands GlyCAM-1 and
PSGL-1 carry sialyl Lewisxas part of a branched Core 2 O-linked structure,
we recently synthesized Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-6(SE-3Galbeta1++
+-3)GalNAc1alphaOMe and found it to be a moderately superior ligand for L
and P-selectin (Koenig et al. , Glycobiology 7, 79-93, 1997). Other studies
have shown that sulfate esters can replace sialic acid in some selectin
ligands (Yeun et al. , Biochemistry, 31, 9126-9131, 1992; Imai et al. ,
Nature, 361, 555, 1993). Based upon these observations, we hypothesized
that Neu5Acalpha2-3Galbeta1-3GalNAc might have the capability of
interacting with L- and P-selectin. To examine this hypothesis, we
synthesized Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-6(Neu5Acalpha2++
+-3Galbeta1-3)- GalNAc alpha1-OB, which was found to be 2- to 3-fold better
than sialyl Lexfor P and L selectin, respectively. We also report the
synthesis of an unusual structure GalNAcbeta1-4(Fucalpha1-
3)GlcNAcbeta1-OMe (GalNAc- Lewisx-O-methyl glycoside), which also proved to
be a better inhibitor of L- and P-selectin than sialyl Lewisx-OMe.
Combining this with our knowledge of Core 2 branched structures, we have
synthesized a molecule that is 5- to 6-fold better at inhibiting L- and
P-selectin than sialyl Lewisx-OMe, By contrast to unbranched structures,
substitution of a sulfate ester group for a sialic acid residue in such a
molecule resulted in a considerable loss of inhibition ability. Thus, the
combination of a sialic acid residue on the primary (beta1-3) arm, and a
modified Lexunit on the branched (beta1-6) arm on an O-linked Core 2
structure generated a monovalent synthetic oliogosaccharide inhibitor
superior to SLexfor both L- and P-selectin.
相似文献
37.
The role of a single N-linked glycosylation site for a functional epitope of herpes simplex virus type 1 envelope glycoprotein gC 总被引:4,自引:2,他引:2
Olofsson S; Bolmstedt A; Biller M; Mardberg K; Leckner J; Malmstrom BG; Trybala E; Bergstrom T 《Glycobiology》1999,9(1):73-81
A monoclonal antibody, B1C1, binding to an epitope of antigenic site II of
the herpes simplex virus type 1 (HSV-1) glycoprotein gC-1, is a potent
inhibitor of two important biological functions of gC-1: its binding to
cell surface heparan sulfate and its binding to the receptor for complement
factor C3b. Here, we have analyzed a B1C1-resistant HSV- 1 variant
(HSV-12762/B1C1B4.2), obtained after passage of wild type HSV- 1
(HSV-12762) in the presence of high concentrations of B1C1. The transport
of newly synthesized mutant gC-1 to the cell surface was comparable to that
of wild type glycoprotein, but no binding of surface- associated mutant
gC-1 to B1C1 was detected. However, mutant and wild type gC-1 bound equally
well to other site II Mabs. Attachment of wild type but not mutant virus
was inhibited by B1C1. Sequencing of the mutant gC-1 gene revealed only one
nucleotide change, resulting in replacement of Thr150 by an Ile, in turn
destroying an N-glycosylation site at Asn148. Loss of one complex type
N-linked glycan was confirmed by endoglycosidase digestion and subsequent
SDS-polyacrylamide gel electrophoresis. Circular dichroism analysis of
purified gC-1 from cells infected with mutant or wild type virus did not
reveal any difference in secondary structure between mutant and wild type
gC-1. It was not possible to obtain a B1C1-resistant phenotype by
nucleotide- directed mutagenesis of gC-1 where Asn148 was changed to a
glutamine. These data demonstrated that the threonine of the glycosylation
site and not the N-linked glycan in itself was essential for B1C1 binding
相似文献
38.
Park ES Hwang WS Kang SK Lee BC Han JY Lim JM 《Molecular reproduction and development》2004,67(2):200-206
In preliminary experiments, the treatment of donor somatic cells with beta-mercaptoethanol (ME) or hemoglobin (Hb) improved in vitro-development of bovine cloned embryos. This study was subsequently evaluated whether the exposure to Hb and/or ME during in vitro-maturation or embryo culture could further promote the development of embryos cloned with ME-treated donor cells. A prospective, randomized study was conducted and, embryo development, cell number, and apoptosis in blastocysts were monitored. A significant (P < 0.05) effect was found after the combined treatment of cloned embryos with Hb (1 microg/ml) and ME (10 microM); the development of morulae (53 vs. 35%) was greatly improved, which resulted in enhanced blastocyst formation (38%). However, cell number and apoptosis in blastocysts were predominantly affected by ME rather than Hb; a significant increase in total cell number of blastomeres (142-154 vs. 123 cells/embryo), inner cell mass (ICM) (39-41 vs. 27), and trophectoderm (TE) (103-114 vs. 98), and the ratio of ICM to TE cell number (0.26-0.27 vs. 0.22) was found. Also, the apoptosis index indicating the ratio of apoptotic cell to normal blastomere number was greatly reduced after ME treatments (0.85 vs. 0.056-0.069). When embryos cloned with ME-treated cells were cultured in Hb + ME-containing medium, any of the treatments to recipient oocytes before enucleation did not further promote the development. In conclusion, combined treatment of cloned embryos with Hb + ME not only improved in vitro-development but also decreased blastomere apoptosis. The use of ME-treated donor cells and the culture of cloned embryos in Hb + ME-containing medium yielded the optimal results for promoting the production of blastocysts with improved quality. 相似文献
39.
Impact on fatty acid metabolism and differential localization of FATP1 and FAT/CD36 proteins delivered in cultured human muscle cells 总被引:1,自引:0,他引:1
García-Martínez C Marotta M Moore-Carrasco R Guitart M Camps M Busquets S Montell E Gómez-Foix AM 《American journal of physiology. Cell physiology》2005,288(6):C1264-C1272
We compared the intracellular distribution and regulatory role of fatty acid transporter protein (FATP1) and fatty acid translocase (FAT/CD36) on muscle cell fatty acid metabolism. With the use of adenoviruses, FATP1 and FAT genes were delivered to primary cultured human muscle cells. FATP1 and FAT moderately enhanced palmitate and oleate transport evenly at concentrations of 0.05, 0.5, and 1 mM. Long-term (16 h) consumption of palmitate and oleate from the media, and particularly incorporation into triacylglyceride (TAG), was stimulated equivalently by FATP1 and FAT at all fatty acid concentrations tested. In contrast, long-term CO2 production was reduced by FATP1 and FAT at all doses of palmitate and at the lower concentrations of oleate. Neither FATP1 nor FAT markedly altered the production of acid-soluble metabolic intermediates from palmitate or oleate. The intracellular localization of fusion constructs of FATP1 and FAT with enhanced green fluorescent protein (EGFP) was examined. Independently of fatty acid treatment, FATPGFP was observed throughout the cytosol in a reticular pattern and concentrated in the perinuclear region, partly overlapping with the Golgi marker GM-130. FATGFP was found in the extracellular membrane and in cytosolic vesicles not coincident with GM-130. Neither FATP1 nor FAT proteins colocalized with lipid droplets in oleate-treated cells. We conclude that whereas FAT is localized on the extracellular membrane, FATP1 is active in the cytosol and imports fatty acids into myotubes. Overall, both FATP1 and FAT stimulated transport and consumption of palmitate and oleate, which they channeled away from complete oxidation and toward TAG synthesis. palmitate; oleate; fatty acid binding proteins; skeletal muscle 相似文献
40.
Thiol-linked DNA-gold nanoparticles were used in a novel colorimetric method to detect the presence of specific mRNA from a total RNA extract of yeast cells. The method allowed detection of expression of the FSY1 gene that encodes a specific fructose/H+ symporter in Saccharomyces bayanus PYCC 4565. FSY1 is strongly expressed when the yeast is grown in fructose as the sole carbon source, while cells cultivated in glucose as the sole carbon source repress gene expression. The presence of FSY1 mRNA is detected based on color change of a sample containing total RNA extracted from the organism and gold nanoparticles derivatized with a 15-mer of complementary single stranded DNA upon addition of NaCl. If FSY1 mRNA is present, the solution remains pink, changing to blue-purple in the absence of FSY1 mRNA. Direct detection of specific expression was possible from only 0.3 microg of unamplified total RNA without any further enhancement. This novel method is inexpensive, very easy to perform as no amplification or signal enhancement steps are necessary and takes less than 15 min to develop after total RNA extraction. No temperature control is necessary and color change can be easily detected visually. 相似文献