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排序方式: 共有174条查询结果,搜索用时 15 毫秒
101.
Kato A Ogasawara T Homma T Batchelor J Imai S Wakiguchi H Saito H Matsumoto K 《Biochemical and biophysical research communications》2004,320(4):1139-1147
CpG oligodeoxynucleotides (CpG ODN) are known to elicit Th1 immune responses via TLR9. However, the precise mechanisms through which B cells are involved in this phenomenon are not fully understood. We investigated the effect of CpG ODN on the induction of Th1-chemoattractant CXCR3 chemokines, IP-10, Mig, and I-TAC, in B cells. Cells from the RPMI 8226 human B cell line and human peripheral B cells were stimulated with three distinct classes of CpG ODN. As a result, CXCR3 chemokines were strongly up-regulated by CpG-B and CpG-C, but only weakly by CpG-A. Though CXCR3 chemokines are known to be induced by IFNs, blocking mAbs against IFN receptors did not inhibit their induction by CpG-B. Induction of CXCR3 chemokines was blocked by two NF-kappaB inhibitors and a p38 inhibitor. These results strongly suggest that CXCR3 chemokines are directly induced by CpG ODN via NF-kappaB- and p38-dependent pathways in human B cells. 相似文献
102.
Based on structural, biochemical, and genetic data, the soluble diiron monooxygenases can be divided into four groups: the soluble methane monooxygenases, the Amo alkene monooxygenase of Rhodococcus corallinus B-276, the phenol hydroxylases, and the four-component alkene/aromatic monooxygenases. The limited phylogenetic distribution of these enzymes among bacteria, together with available genetic evidence, indicates that they have been spread largely through horizontal gene transfer. Phylogenetic analyses reveal that the alpha- and beta-oxygenase subunits are paralogous proteins and were derived from an ancient gene duplication of a carboxylate-bridged diiron protein, with subsequent divergence yielding a catalytic alpha-oxygenase subunit and a structural beta-oxygenase subunit. The oxidoreductase and ferredoxin components of these enzymes are likely to have been acquired by horizontal transfer from ancestors common to unrelated diiron and Rieske center oxygenases and other enzymes. The cumulative results of phylogenetic reconstructions suggest that the alkene/aromatic monooxygenases diverged first from the last common ancestor for these enzymes, followed by the phenol hydroxylases, Amo alkene monooxygenase, and methane monooxygenases. 相似文献
103.
Cell density-regulated recovery of starved biofilm populations of ammonia-oxidizing bacteria. 总被引:8,自引:2,他引:6
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S E Batchelor M Cooper S R Chhabra L A Glover G S Stewart P Williams J I Prosser 《Applied microbiology》1997,63(6):2281-2286
The speed of recovery of cell suspensions and biofilm populations of the ammonia oxidizer Nitrosomonas europaea, following starvation was determined. Stationary-phase cells, washed and resuspended in ammoniumfree inorganic medium, were starved for periods of up to 42 days, after which the medium was supplemented with ammonium and subsequent growth was monitored by measuring nitrite concentration changes. Cultures exhibited a lag phase prior to exponential nitrite production, which increased from 8.72 h (no starvation) to 153 h after starvation for 42 days. Biofilm populations of N. europaea colonizing sand or soil particles in continuous-flow, fixed column reactors were starved by continuous supply of ammonium-free medium. Following resupply of ammonium, starved biofilms exhibited no lag phase prior to nitrite production, even after starvation for 43.2 days, although there was evidence of cell loss during starvation. Biofilm formation will therefore provide a significant ecological advantage for ammonia oxidizers in natural environments in which the substrate supply is intermittent. Cell density-dependent phenomena in a number of gram-negative bacteria are mediated by N-acyl homoserine lactones (AHL), including N-(3-oxohexanoyl)-L-homoserine lactone (OHHL). Addition of both ammonium and OHHL to cell suspensions starved for 28 days decreased the lag phase in a concentration-dependent manner from 53.4 h to a minimum of 10.8 h. AHL production by N. europaea was detected by using a luxR-luxAB AHL reporter system. The results suggest that rapid recovery of high-density biofilm populations may be due to production and accumulation of OHHL to levels not possible in relatively low-density cell suspensions. 相似文献
104.
The timing of alpha-gustducin expression during cell renewal in rat vallate taste buds 总被引:2,自引:2,他引:0
The G protein subunit alpha-gustducin is expressed in a subset of light
(Type II) but not in dark (Type I) cells in rat vallate taste buds. The
thymidine analogue 5-bromo-2'-deoxyuridine (BrdU) is incorporated into DNA
during the S-phase of the cell cycle and can be used to determine the time
of origin of a cell. In this study, 31 rats were injected with BrdU (50
mg/kg i.p.) and perfused at various times, from 2.5 to 10.5 days, following
BrdU administration. Vallate papillae were embedded in polyester wax, cut
into 4 microm transverse sections, and characterized with antibodies to
BrdU and alpha-gustducin. Sections were processed for indirect
immunofluorescence or with an immunoperoxidase procedure. From
immunoperoxidase material on 21 rats, counts of alpha-gustducin- and
BrdU-labeled cells were obtained from 300-800 taste bud profiles at each
survival time; a total of 4122 taste bud profiles were examined. Cells with
nuclei immunoreactive for BrdU occurred within the taste buds at 2.5 days
and double-labeled cells were clearly evident at 3.5 days; a small number
of double-labeled cells were seen as early as 2.5 days. Double-labeled
cells reached a peak at 6.5 days and did not decline significantly by 10.5
days. Cells labeled for BrdU but not alpha-gustducin peaked at 5.5 days and
showed a significant decline by 8.5 days. These latter cells included light
cells not expressing alpha- gustducin and dark cells, which have previously
been shown to have a shorter life span than light cells. These data suggest
that expression of alpha-gustducin appears very early in a cell's life span
and that these cells are longer lived than many of the cells that do not
express this G protein.
相似文献
105.
Tonic GABAergic inhibition of taste-responsive neurons in the nucleus of the solitary tract 总被引:4,自引:1,他引:3
The effects of gamma-aminobutyric acid (GABA) and the GABAA receptor
antagonist bicuculline methiodide (BICM) on the activity of taste-
responsive neurons in the nucleus of the solitary tract (NST) were examined
electrophysiologically in urethane-anesthetized hamsters. Single neurons in
the NST were recorded extracellularly and drugs (21 nl) were microinjected
into the vicinity of the cell via a multibarrel pipette. The response of
each cell was recorded to lingual stimulation with 0.032 M NaCl, 0.032 M
sucrose, 0.0032 M citric acid and 0.032 M quinine hydrochloride (QHCl).
Forty-six neurons were tested for the effects of GABA; the activity of 29
cells (63%) was inhibited by 5 mM GABA. Whether activity was elicited in
these cells by repetitive anodal current stimulation (25 microA, 0.5 s, 0.1
Hz) of the tongue (n = 13 cells) or the cells were spontaneously active (n
= 13 cells), GABA produced a dose-dependent (1, 2 and 5 mM) decrement in
activity. Forty- seven NST neurons were tested for the effects of BICM on
their responses to chemical stimulation of the tongue; the responses of 28
cells (60%) were enhanced by 10 mM BICM. The gustatory responses of 26 of
these cells were tested with three concentrations (0.2, 2 and 10 mM) of
BICM, which produced a dose-dependent increase in both spontaneous activity
and taste-evoked responses. Nine of these neurons were sucrose- best, seven
were NaCl-best, eight were acid-best and two responded best to QHCl. The
responses to all four tastants were enhanced, with no difference among
neuron types. For 18 cells that were tested with two or more gustatory
stimuli, BICM increased their breadth of responsiveness to their two most
effective stimuli. These data show that approximately 60% of the
taste-responsive neurons in the rostral NST are inhibited by GABA and/or
subject to a tonic inhibitory influence, which is mediated by GABAA
receptors. The modulation of these cells by GABA provides a mechanism by
which the breadth of tuning of the cell can be sharpened. Modulation of
gustatory activity following a number of physiological changes could be
mediated by such a GABAergic circuit.
相似文献
106.
An efficient biosynthetic method to prepare fatty acyl chains highly enriched with 13C 总被引:2,自引:0,他引:2
A method has been developed for the biosynthetic incorporation of 13C acetate into fatty acyl chains. It combines both high specific enrichment and high utilization of the acetate. 相似文献
107.
108.
Giovanna Lombardi Masanori Matsui Robert Moots Gerald Aichinger Sid Sidhu Richard Batchelor Jeff Frelinger Robert Lechler 《Immunogenetics》1991,34(3):149-156
The regions of the HLA-A2 molecule controlling anti-A2 alloreactivity were explored using naturally occurring allelic variants of HLA-A, and a panel of transfectants expressing the products of A2.1 genes that had been mutated at multiple positions encoding residues in the 2 domain -helix. As a means of detecting distant conformational effects, these altered A2.1 molecules were also examined serologically. Amino acid substitutions at the carboxy-terminal end of the 2 domain -helix led to diminished staining with the monoclonal antibody (mAb) MA2.1. The epitope for this antibody has previously been mapped to the 1 domain -helix (residues 62–65). This suggests that interdomain contacts may cause conformational alteration, and that mutants can have distant, as well as local effects. Of the 24 positions where substitutions were made, only six led to loss of the anti-A2 alloresponse by the three clones and three lines that were tested. In addition, the mutations that altered the MA2.1 epitope, located on the 1 domain -helix, did not inhibit allorecognition. This suggests that a limited number of regions on the A2.1 molecule are responsible for allodeterminant expression. The most influential substitutions were those at positions 152, 154, 162, and 166. It is notable that three of these are predicted to be T-cell receptor (Tcr)-contacting residues, and one (152) to contribute to peptide binding. These results suggest that the specificity of alloreactive T cells is determined by exposed polymorphisms, directly contacted by the Tcr, and by concealed polymorphisms which influence peptide binding. 相似文献
109.
110.