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排序方式: 共有237条查询结果,搜索用时 125 毫秒
1.
Lowering pH in blood platelets dissociates myosin phosphorylation from shape change and myosin association with the cytoskeleton 总被引:1,自引:0,他引:1 下载免费PDF全文
Platelet shape change induced by ADP is relatively independent of external pH over the range 6-7. If the chloride ion in the buffer is replaced by weak acids, however, shape change is rapidly and reversibly inhibited as a function of lowered pH (92% at pH 6.0). This inhibition is correlated with lowered internal pH caused by the weak acids, as measured by the 5,5-dimethyloxazolidine 2,4-dione technique. Shape change was 50% inhibited at internal pH 6.4 when 50 mM NaCl was replaced by propionate (PR). When platelets were stimulated with ADP 10-20 s after addition of PR to a final pH of 6 (PR6), both myosin light chain (MLC) phosphorylation and myosin and actin association with the cytoskeleton were reduced in correlation with the inhibition of shape change. But when ADP was added 30 s after PR6, the MLC phosphorylation was essentially the same in PR or in chloride, although shape change and myosin and actin association with the cytoskeleton remained inhibited. This was shown to be due mainly to endogenous phosphorylation of MLC. On return to neutral pH, platelets in PR immediately changed shape and myosin and actin became associated with the cytoskeleton. Two-dimensional tryptic peptides of MLC showed two major spots after PR6 treatment, indicating that both the MLC kinase site and the protein kinase C sites were phosphorylated. The results show that increased internal pH is not required for shape change, although it may affect the rate. In PR6, as after phorbol esters, MLC phosphorylation can be uncoupled from shape change. The association of myosin and actin with the cytoskeleton is closely correlated with shape change, suggesting that shape change requires the active interaction of these contractile proteins. 相似文献
2.
We have isolated the delta-globin gene of the New-World spider monkey,
Ateles geoffroyi, and compared its nucleotide sequence with those of other
primate delta- and beta-globin genes. Among primate delta-globin genes, the
rate of nonsynonymous substitutions is much less than the rate of
synonymous substitutions. This suggests that primate delta- globin genes
may remain under evolutionary conservation, perhaps because hemoglobin A2
has an as yet unknown physiological importance.
相似文献
3.
Biochemical pathways in prokaryotes can be traced backward through evolutionary time 总被引:10,自引:0,他引:10
For the first time, a credible prokaryotic phylogenetic tree is being
assembled by Woese and others using quantitative sequence analysis of
oligonucleotides in the highly conservative rRNA. This provides an
evolutionary scale against which the evolutionary steps that led to the
arrangement and regulation of contemporary biochemical pathways can be
measured. This paper presents an emerging evolutionary picture of aromatic
amino acid biosynthesis within a large superfamily assemblage of
prokaryotes that is sufficiently developed to illustrate a new perspective
that will be applicable to many other biochemical pathways.
相似文献
4.
Discriminative stimulus properties of the serotonin agonist 1-(3-trifluoromethylphenyl)piperazine (TFMPP) 总被引:1,自引:0,他引:1
Using a standard two-lever drug discrimination procedure, twelve rats were trained to discriminate 1.0 mg/kg of the serotonin (5-HT) agonist TFMPP from saline. Once trained, the animals displayed a dose-related decrease in discriminative performance upon administration of lower doses of TFMPP. Tests of stimulus generalization were performed using the purported 5-HT agonist RU-24, 969 and 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM). While TFMPP produced stimulus effects similar to those of RU-24,969, these effects seem to be dissimilar to those of DOM. The results of the present study suggest that the discriminative stimulus effects of TFMPP may involve a 5-HT1-related mechanism. 相似文献
5.
In Drosophila pseudoobscura, the amylase (Amy) multigene family is
contained within a series of inversions, or gene arrangements, on the third
chromosome. The Standard (ST), Santa Cruz (SC), and Tree Line (TL)
inversions are central to the phylogeny of arrangements, and have clusters
of other arrangements derived from them. The gene arrangements belonging to
each of these three clusters have a characteristic number of Amy genes,
ranging from three in ST to two in SC to one in TL. This distribution
pattern can reflect a history of either duplications or deletions, although
the data available in the past did not permit a decision between these
alternatives. We provide unambiguous evidence that three Amy genes were
present before the divergence of the ST, SC, and TL arrangements. Thus, the
current status of the Amy multigene family is the result of deletions in
the TL and SC arrangements, which created three new pseudogenes: TL
Amy2-psi, TL Amy3-psi, and SC Amy3- psi. Analysis of pseudogene sequences
revealed that, in the SC and ST arrangements, pseudogene evolution has been
retarded, most likely due to the homogenization effect of gene conversion.
Finally, by determining the original copy number, we have reconstructed the
evolutionary history of the Amy multigene family and linked it with the
evolution of the central gene arrangements.
相似文献
6.
The application of sensory methodology for measuring deodorizing effect of an air conditioner equipped with electric plasma was introduced. Deodorizing effect was measured using chemical and sensory methods at different time (0, 30 and 60 min) and mode (control, blowing and cooling) of an air conditioner. Smoke from a roll of cigarette in a closed room was used as a source of odor and the concentrations of acetic acid and ammonia were measured as odorous chemical components. As one of the sensory methods triangle test was used and as a first step to obtain deodorizing effects by triangle test, the threshold of each panelist was obtained as the log dilution ratio of odor concentration at which the difference from odorless air was detected. The odor concentration at each time and mode was calculated using the threshold of the panel and the deodorizing effect was obtained on the basis of the odor concentration. In addition to a triangle test, scaling methods such as category scaling or magnitude estimation were used to measure deodorizing effect of an air conditioner. Deodorizing effects by scaling methods were calculated based on odor intensity with time at each mode. The regression analysis was done between the efficacy of deodorizing effect by sensory test and those by acetic acid and ammonia, the R2 values of the regression equations for triangle test, category scale, and magnitude estimation were 0.84, 0.72 and 0.69, respectively. Deodorizing effect by triangle test explained the decrease of acetic acid and ammonia better than those by category scaling or magnitude estimation while high cost and time consuming labor involved in triangle tests reduced the merit. The results of this study demonstrated that various sensory methods could be used to measure deodorizing effect of air conditioners and further researches on fast and reliable methods are needed to establish the official procedures. 相似文献
7.
8.
Hallucinogens (psychotomimetic agents) are capable of producing various discriminative stimuli for animals. Serotonergic involvement has been implicated as playing a role in the behavioral effects elicited by, for example, mescaline and DOM. Because certain tryptamine analogs possess high serotonin (5-HT) receptor binding affinities, it was of interest to examine one of the more potent agents. Employing a standard operant test chamber, six rats were trained to respond under a variable-interval 15-second schedule of sweetened-milk reinforcement. 5-Methoxy-N, N-dimethyltryptamine (5-OMe DMT), which possesses a 5-HT receptor affinity much higher than that of mescaline, but nearly equivalent to that of DOM, was found to serve as a discriminative stimulus. Furthermore, the 5-OMe DMT stimulus could be attenuated by the 5-HT antagonist BC-105. The 5-OMe DMT stimulus generalized with DOM suggesting that these two hallucinogens produce qualitatively similar interoceptive cues in rats. 相似文献
9.
T J Kulik R A Bialecki W S Colucci A Rothman E T Glennon R H Underwood 《Biochemical and biophysical research communications》1991,180(2):982-987
There are no reports of the effect of stretch on inositol phosphates in smooth muscle. Phosphoinositide and inositol phosphate metabolism was studied in cultured rat vascular smooth muscle cells subjected to stretching. The masses of inositol trisphosphate and tetrakisphosphate increased (+34 +/- 7% and +58 +/- 12%, respectively; p less than 0.001) after 25 s of a single 20% stretch and had returned to control levels by 45 s; phosphatidylinositol, phosphatidylinositol phosphate and bisphosphate did not change. Repetitive stretch did not alter the masses of any of the compounds. A single stretch also increased 45Ca2+ efflux (+52 +/- 5%, p less than 0.01). These data suggest that stretch of cultured vascular smooth muscle can elicit a rapid, short-lived increase in inositol phosphates, which may subsequently affect Ca2+. 相似文献
10.
Aron Kos Nikkie F. Olde Loohuis Jeffrey C. Glennon Tansu Celikel Gerard J. M. Martens Paul H. Tiesinga Armaz Aschrafi 《Molecular neurobiology》2013,47(1):172-185
The emergence of optogenetics technology facilitated widespread applications for interrogation of complex neural networks, such as activation of specific axonal pathways, previously found impossible with electrical stimulation. Consequently, within the short period of its application in neuroscience research, optogenetics has led to findings of significant importance both during normal brain function as well as in disease. Moreover, the optimization of optogenetics for in vivo studies has allowed the control of certain behavioral responses such as motility, reflex, and sensory responses, as well as more complex emotional and cognitive behaviors such as decision-making, reward seeking, and social behavior in freely moving animals. These studies have produced a wide variety of animal models that have resulted in fundamental findings and enhanced our understanding of the neural networks associated with behavior. The increasing number of opsins available for this technique enabled even broader regulation of neuronal activity. These advancements highlight the potential of this technique for future treatment of human diseases. Here, we provide an overview of the recent developments in the field of optogenetics technology that are relevant for a better understanding of several neuropsychiatric and neurodegenerative disorders and may pave the way for future therapeutic interventions. 相似文献