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排序方式: 共有429条查询结果,搜索用时 31 毫秒
1.
Characterization of the muscarinic receptor subtype involved in phosphoinositide metabolism in bovine tracheal smooth muscle 总被引:9,自引:6,他引:3
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1. The muscarinic receptor subtype involved in the methacholine-induced enhancement of phosphoinositide metabolism in bovine tracheal smooth muscle was identified by using the M2-selective antagonist AF-DX 116 and the M3-selective antagonist 4-diphenylacetoxy-N-methylpiperidine (4-DAMP) methobromide, in addition to the M1-selective antagonist pirenzepine, in a classical Schild analysis. 2. All the antagonists shifted the methacholine dose-response curve to the right in a parallel and concentration-dependent fashion, yielding Schild plots with slopes not significantly different from unity. The pA2 values (6.94, 6.32 and 8.54 for pirenzepine, AF-DX 116 and 4-DAMP methobromide respectively) indicate that it is the M3 (smooth muscle/glandular), but not the M2 (cardiac) muscarinic receptor subtype, present in this tissue, that mediates phosphoinositide turnover, in accordance with our previous contractile studies. 3. The results provide additional evidence for the involvement of phosphoinositide turnover in the pharmacomechanical coupling between muscarinic receptor stimulation and contraction in (bovine tracheal) smooth muscle. 相似文献
2.
Nicole Y. L. Oei Bernet M. Elzinga Oliver T. Wolf Michiel B. de Ruiter Jessica S. Damoiseaux Joost P. A. Kuijer Dick J. Veltman Philip Scheltens Serge A. R. B. Rombouts 《Brain imaging and behavior》2007,1(1-2):31-41
Glucocorticoids (GCs, cortisol in human) are associated with impairments in declarative memory retrieval. Brain regions hypothesized
to mediate these effects are the hippocampus and prefrontal cortex (PFC). Our aim was to use fMRI in localizing the effects
of GCs during declarative memory retrieval. Therefore, we tested memory retrieval in 21 young healthy males in a randomized
placebo-controlled crossover design. Participants encoded word lists containing neutral and emotional words 1 h prior to ingestion
of 20 mg hydrocortisone. Memory retrieval was tested using an old/new recognition paradigm in a rapid event-related design.
It was found that hydrocortisone decreased brain activity in both the hippocampus and PFC during successful retrieval of neutral
words. These observations are consistent with previous animal and human studies suggesting that glucocorticoids modulate both
hippocampal and prefrontal brain regions that are crucially involved in memory processing.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
4.
Using the open-field test, differences in emotional reactivity were shown in male rats of several albino strains. These behavioural differences were then investigated in relation to physiological differences. It was found that, under resting conditions, sympatho-adrenomedullary activity as estimated by urinary catecholamine excretion and adrenal catecholamine content is lower in the more emotionally reactive rats. The resting heart rate is correspondingly slower in these animals though they show the same noradrenaline cardiac concentration as the nonreactive rats. These data suggest that high defecating rats in the open-field exhibit a lower sympathetic tonus, possibly linked, however, with a higher parasympathetic tonus. 相似文献
5.
H. P. J. Buschman M. Linari G. Elzinga R. C. Woledge 《Pflügers Archiv : European journal of physiology》1997,435(1):145-150
The mechanical and energy characteristics of isolated fast-twitch muscle fibres (type 1) of Xenopus laevis in isometric- and isovelocity contractions were measured at 20°C. The fibres were stimulated at either 60 Hz or 20 Hz to
produce contractions at different levels of activation. The high stimulation frequency gave fused contractions, while at the
low stimulation frequency tension fluctuated. When maximum isometric force had been reached, the fibres were shortened by
10% of the fibre length at different velocities. At 60 Hz stimulation during shortening the rate of heat production increased
above the isometric rate of heat production. At 20 Hz stimulation during shortening, however, the rate of heat production
was not different from the isometric rate of heat production. Mechanical efficiency was the same at the high and low level
of activation. The actomyosin efficiency (i.e. the mechanical efficiency corrected for ”activation heat”) was highest at the
low level of activation. We conclude that in fast-twitch muscle fibres from X. laevis, actomyosin efficiency is highest for partially activated muscle. From a comparison of the present results with those obtained
from a study of slow-twitch muscle fibres presented earlier, it is concluded that fast-twitch muscle fibres are less efficient
than slow-twitch muscle fibres.
Received after revision: 13 May 1997 / Accepted: 1 July 1997 相似文献
6.
Isolation and RNA-binding analysis of NAD+-isocitrate dehydrogenases from Kluyveromyces lactis and Schizosaccharomyces pombe 总被引:1,自引:0,他引:1
Krebs cycle NAD+-isocitrate dehydrogenase (Idh) binds to the 5-UTRs of all mitochondrial mRNAs in Saccharomyces cerevisiae. We hypothesize that this leader-binding activity plays a role in translational regulation, thereby linking mitochondrial
biogenesis to the need for respiratory function. Analysis of effects of leader binding on mitochondrial translation is complicated
by the involvement of the enzyme in mitochondrial metabolism. We have therefore searched for an Idh altered in RNA binding,
but retaining full enzyme activity. Idh from Kluyveromyces lactis and Schizosaccharomyces pombe was partially purified and examined for the ability to bind Cox2 mRNA. Sch. pombe Idh, like the S. cerevisiae enzyme, has high affinity for both its own, K. lactis and S. cerevisiaeCOX2 leaders. In contrast, Idh purified from K. lactis shows only low affinity for all mRNAs tested. To determine what distinguishes K. lactis Idh from S. cerevisiae Idh, genes encoding the two subunits of Idh in K. lactis were cloned and sequenced. Sequence comparison revealed high levels of similarity throughout the proteins, in particular
in regions involved in enzyme activity, co-factor and regulator binding. Non-conserved residues between the subunits from
the two yeasts are candidates for involvement in the interaction with RNA.
Received: 19 January 2000 / 24 March 2000 相似文献
7.
de Ruiter CJ Elzinga MJ Verdijk PW van Mechelen W de Haan A 《Pflügers Archiv : European journal of physiology》2004,447(4):436-444
The purpose of the present study was to relate the expected inter-subject variability in voluntary drive of the knee extensor muscles during a sustained isometric contraction to the changes in firing rates of single motor units. Voluntary activation, as established with superimposed electrical stimulation was high (range: 91–99%, n=8) during a short maximal contraction, but was lower (range: 69–100%) in most subjects at the point of force failure during a sustained (49.1±10.1 s) fatiguing contraction at 50% of maximum force. On a different experimental day the firing behaviour of 27 single motor units was recorded with wire electrodes in the vastus lateralis muscle, 24 of which could be monitored from the time of recruitment to the point of force failure (53.6±9.8 s). Motor unit firing behaviour differed considerably among subjects. During the second half of the sustained, fatiguing contraction the changes in firing rate firing rate variability of early recruited units ranged from –10% to +100% and from –50% to +160% respectively among subjects. There were significant positive linear relations between voluntary activation, on the one hand, and rectified surface electromyogram (rsEMG, r=0.82), the changes in motor unit firing rate (r=0.49) and firing rate variability (r=0.50) towards the point of force failure on the other. The present data suggest that differences in voluntary drive that appear among subjects during fatigue may be an important determinant of motor unit firing behaviour.Abbreviations
EMG
electromyogram
-
ER unit
early recruited unit
-
MFGC
maximal force-generating capacity
-
MPF
mean power frequency
-
MVC
maximum voluntary contraction
-
NR unit
newly recruited unit
-
rsEMG
rectified surface electromyogram
-
SMUAP
single motor unit action potential 相似文献
8.
Ad F Roffel Joost H Davids Carolina R S Elzinga Doris Wolf Johan Zaagsma Heinz Kilbinger 《British journal of pharmacology》1997,122(1):133-141
- The muscarinic receptor subtypes mediating contraction of the guinea-pig lung strip and inhibition of the release of acetylcholine from cholinergic vagus nerve endings in the guinea-pig trachea in vitro have previously been characterized as M2-like, i.e. having antagonist affinity profiles that are qualitatively similar but quantitatively dissimilar compared to cardiac M2 receptors. The present study sought to establish definitely the identity of these receptor subtypes by using the selective muscarinic receptor antagonist, tripitramine. Guinea-pig atria and guinea-pig trachea (postjunctional contractile response) were included for reference.
- It was found that tripitramine antagonized methacholine-induced contractions of the guinea-pig lung strip with a pKB value of 8.76±0.05. Both the parallel shifts of the concentration-response curves and the slope of the Schild plot being not significantly different from unity (when antagonist preincubation was for 2 h) indicated the involvement of a single population of receptors in the contractile response. From the pKB values obtained with tripitramine and a range of other selective muscarinic receptor antagonists (cf. Roffel et al., 1993), this single population of receptors can only be classified as M2-like.
- Tripitramine antagonized methacholine-induced negative chronotropic and inotropic responses in guinea-pig right and left atria with apparent pKB values of 9.4–9.6. However, such values were only obtained when antagonist preincubation was relatively long and/or antagonist concentration relatively high (e.g. with 1 h at 100 or 300 nM but 3 h at 30 nM). It thus appears that low concentrations of tripitramine do not readily equilibrate with M2 receptors in guinea-pig atria nor with M2-like receptors in the guinea-pig lung strip.
- Tripitramine increased electrical field stimulation-induced cholinergic twitch contractions in guinea-pig trachea in concentrations of 0.3–100 nM, by blocking prejunctional muscarinic inhibitory autoreceptors; with higher concentrations, twitch contractions were progressively diminished, as a result of blocking postjunctional M3 receptors (apparent pKB value 6.07±0.15). The pEC20 value (−log concentration that increases twitch by 20% of maximum) was 8.29±0.08, which would suggest that M4 receptors are involved in this response.
- Oxotremorine-induced inhibition of the release of prelabelled [3H]-acetylcholine from guinea-pig trachea, under conditions where there is no auto-feedback, was blocked by tripitramine (2 h preincubation) with a pKB value of 8.56±0.06. The slope of the corresponding Schild plot was not significantly different from unity, which together with the parallel shifts of the concentration-response curves indicated the involvement of a single muscarinic receptor subtype.
- Since the pKB value for tripitramine at prejunctional receptors in guinea-pig trachea is in between the affinities towards M2 and M4 receptors, correlation plots were constructed to compare the pKB values obtained with tripitramine and a range of other selective muscarinic receptor antagonists (cf. Kilbinger et al., 1995) to reported affinities at M1–M4 receptors. This showed rather similar distribution patterns of the data points around the line of equality in the case of M2 and M4 receptor subtypes. However, the correlation coefficient was markedly better for M2 (0.9667) than for M4 (0.5976). Since recent evidence suggests that M4 receptors are not expressed in cholinergic nerves from guinea-pig trachea, it is concluded that prejunctional muscarinic autoinhibitory receptors in this tissue exhibit an atypical M2 type character, with a pharmacological profile distinct from cardiac M2 receptors.
9.
Age does not influence early and late tumor-related outcome for bronchogenic carcinoma 总被引:5,自引:0,他引:5
Bernet F Brodbeck R Guenin MO Schüpfer G Habicht JM Stulz PM Carrel TP 《The Annals of thoracic surgery》2000,69(3):913-918
BACKGROUND: The influence of age on early and late outcome after surgical resection of bronchogenic carcinoma is unknown. In an attempt to clarify this issue, we reviewed the outcome of 212 consecutive patients with primary lung cancer who had surgical treatment for bronchogenic carcinoma. METHODS: Ninety-two patients were younger than 50 years (group 1), and 120 patients were older than 70 years of age (group 2). Squamous cell carcinoma and adenocarcinoma were the most common histologic types in both groups. According to the new international staging classification, a similar proportion of stage I, II, and III were observed in both groups. RESULTS: Only the rate of pneumonectomy was significantly higher in younger patients (41% versus 22%, p = 0.002). The overall operative mortality rate in group 1 was 2.2% and 2.6% after pneumonectomy. In group 2 the overall mortality rate was 2.5% and 3.8% after pneumonectomy. Advanced age did not affect operative mortality. The adjusted (tumor-related) survival rate at 5 years was 56% in group 1 and 53% in group 2 (p = 0.93). The adjusted survival rate for patients with stage I was 61% in group 1 and 65% in group 2 (p = 0.21), and for stage IIIa 39% in group 1 and 48% in group 2 (p = 0.43). The adjusted 5-year survival rate was 56% in group 1 and 59% in group 2 for squamous cell carcinoma (p = 0.53) and 49% in group 1 and 42% in group 2 for adenocarcinoma (p = 0.76). CONCLUSIONS: Perioperative risk and midterm survival were similar in younger and older patients after surgical resection of bronchogenic carcinoma. We believe that this result is because surgical candidates constitute already a highly selected group of patients. From these data it is not possible to conclude that biologic behavior of lung cancer is more aggressive in younger patients. 相似文献
10.