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排序方式: 共有111条查询结果,搜索用时 343 毫秒
31.
ZHANGLingyun PENGChangcao ZOUKeqin WANGXiuling FANRenchun YUXiangchun ZHANGXiaoyan SHENYuanyue ZHANGDapeng 《科学通报(英文版)》2005,50(5):429-434
Two major classes of plant sugar transporters, sucrose and monosaccharide transporters, may be localized to tonoplast or plasma membrane. The monosaccharide transporters may also be localized in plastid. However, whether these transporters reside in other subcellular compartments remains unclear. We recently detected in apple fruit a 52 kD plasma membrane-localized monosaccharide transporter, and showed that this transporter may be functional in phloem unloading in the fruit. In this paper, we report that this monosaccharide transporter is also localized to sieve plate and plasmodesmal channel in apple fruit. The amount of this sieve plate- and plasmodesma-associated transporter changes during fruit development. This amount of the transporter expression may be altered in the phloem sieve elements but not in the parenchyma cells by a photoassimilate deficiency applied by the shoot girdling treatment, suggesting that the monosaccharide transporter of the special sub-cellular localization may be of biological significance. 相似文献
32.
姬迎春 《科技情报开发与经济》2006,16(2):272-273
分析了成庄矿主井胶带机驱动控制系统设备出现故障的原因,论述了驱动控制系统改进方案的确定原则,并详细介绍了改进方案。 相似文献
33.
Trompier D Baubichon-Cortay H Chang XB Maitrejean M Barron D Riordon JR Di Pietro A 《Cellular and molecular life sciences : CMLS》2003,60(10):2164-2177
Recombinant nucleotide-binding domains (NBDs) from human multidrug resistance protein MRP1 were overexpressed in bacteria and purified to measure their direct interaction with high-affinity flavonoids, and to evaluate a potential correlation with inhibition of MRP1-mediated transport activity and reversion of cellular multidrug resistance. Among different classes of flavonoids, dehydrosilybin exhibited the highest affinity for both NBDs, the binding to N-terminal NBD1 being prevented by ATP. Dehydrosilybin increased vanadate-induced 8-N3-[-32P]ADP trapping, indicating stimulation of ATPase activity. In contrast, dehydrosilybin strongly inhibited leukotriene C4 (LTC4) transport by membrane vesicles from MRP1-transfected cells, independently of reduced glutathione, and chemosensitized cell growth to vincristine. Hydrophobic C-isoprenylation of dehydrosilybin increased the binding affinity for NBD1, but outsite the ATP site, lowered the increase in vanadate-induced 8-N3-[-32P]ADP trapping, weakened inhibition of LTC4 transport which became glutathione dependent, and induced some cross-resistance. The overall results indicate multiple binding sites for dehydrosilybin and its derivatives, on both cytosolic and transmembrane domains of MRP1.Received 1 May 2003; received after revision 18 June 2003; accepted 24 June 2003 相似文献
34.
D. Evéquoz E. Grouzmann A. G. Beck-Sickinger H. -R. Brunner B. Waeber 《Cellular and molecular life sciences : CMLS》1994,50(10):936-938
Neuropeptide Y (NPY) increases blood pressure either directly or indirectly by potentiating the effect of various vasoconstrictors. Only one (the Y1-receptor) of two subtypes of receptors (Y1 and Y2) is thought to mediate the vascular smooth muscle contraction. To test this hypothesis we challenged isolated rat mesenteric arteries that had a functional endothelium with (1–36) NPY and with specific Y1-receptor ([Leu31, Pro34] NPY) and Y2-receptor ([Ahx5–24, -Glu2--Lys30] NPY) agonists. The Y1-receptor agonist elicited a contractile response similar to that of NPY, whereas the Y2-receptor agonist had no effect on wall tension. We also found that the presence of a functional endothelium has no influence on the contractile response to NPY. From these data we conclude that the direct contractile effect of NPY in the mesenteric artery is mediated by stimulation of Y1-receptors and is not endothelium-dependent. 相似文献
35.
纳米中药——中药现代化的新途径 总被引:2,自引:0,他引:2
纳米中药是近年来迅速发展起来的前沿科技领域,与传统中药比较有其优势及特色.纳米中药的开发需要多学科的合作与研究,是传统中药走向国际化的方向,具有着广阔的前景. 相似文献
36.
Pozza A Perez-Victoria JM Sardo A Ahmed-Belkacem A Di Pietro A 《Cellular and molecular life sciences : CMLS》2006,63(16):1912-1922
Human ABCG2 was efficiently overexpressed in insect cell membranes, solubilized with 3-[(3-cholamidopropyl)dimethyl ammonio]-1-propanesulfonate,
and purified through N-terminal hexahistidine tag. Its functionality was assessed by high vanadate-sensitive ATPase activity, and nucleotide-binding
capacity. Interestingly, the R482T point mutation increased both maximal hydrolysis rate and affinity for MgATP, and lowered
sensitivity to vanadate inhibition. Direct nucleotide binding, as monitored by quenching of intrinsic fluorescence, indicated
a mutation-related preference for ATP over ADP. The R482T mutation only produced a limited change, if any, on the binding
of drug substrates, indicating that methotrexate, on the one hand, and rhodamine 123 or doxorubicin, on the other hand, bound
similarly to wild-type and mutant transporters whether or not they were subject to cellular transport. In addition, the characteristic
inhibitors GF120918 and 6-prenylchrysin, which alter mitoxantrone efflux much better for wild-type than mutant ABCG2, bound
similarly to purified ABCG2, while the highly-potent Ko143 bound in the nanomolar range also effective in inhibition of drug
transport. All results indicate that the role of the arginine-482 mutation on substrate drug transport and inhibitor efficiency
is not mediated by changes in drug binding.
Received 10 April 2006; received after revision 22 May 2006; accepted 12 June 2006
A. Pozza and J. M. Perez-Victoria contributed equally to this work 相似文献
37.
Gbaguidi B Hakizimana P Vandenbussche G Ruysschaert JM 《Cellular and molecular life sciences : CMLS》2007,64(12):1571-1582
LmrP is an electrogenic H+/drug antiporter that extrudes a broad spectrum of antibiotics. Five carboxylic residues are implicated in drug binding (Asp142
and Glu327) and proton motive force-mediated restructuring (Asp68, Asp128 and Asp235). ATR-FTIR (Attenuated Total Reflection
– Fourier Transform Infrared) and tryptophan quenching experiments revealed that phosphatidylethanolamine (PE) is required
to generate the structural intermediates induced by ionization of carboxylic residues. Surprisingly, no ionization-induced
conformational changes were detectable in the absence of PE, suggesting either that carboxylic acid residues do not ionize
or that ionization does not lead to any conformational change. The mean pKa of carboxylic residues evaluated by ATR-FTIR spectroscopy
was 6.5 for LmrP reconstituted in PE liposomes, whereas the pKa calculated in the absence of PE was 4.6. Considering that
16 of the 19 carboxylic residues are located in the extramembrane loops, the pKa values obtained in the absence and in the
presence of PE suggest that the interaction of the loop acid residues with the membrane interface depends on the lipid composition.
Received 23 January 2007; received after revision 2 April 2007; accepted 20 April 2007 相似文献
38.
Despite being relatively insensitive to environmental insult, the spore is responsive to low concentrations of chemical germinants,
which induce germination. The process of bacterial spore germination involves membrane permeability changes, ion fluxes and
the activation of enzymes that degrade the outer layers of the spore. A number of components in the spore that are required
for the germination response have been identified, including a spore-specific family of receptor proteins (the GerA family),
an ion transporter and cortex lytic enzymes. The germinant traverses the outer layers of the spore and interacts with its
receptor in the inner membrane to initiate the cascade of germination events, but the molecular details of this signal transduction
process remain to be identified. 相似文献
39.
目的探讨锌缺乏对小鼠大脑海马锌离子和锌转运蛋白4(Zinc Transporter 4,ZnT4)表达的影响.方法建立锌缺乏动物模型,给断乳后的CD-1小鼠分别喂养缺锌饲料和正常饲料,5周后取大脑海马组织,应用锌金属自显影技术、免疫组织化学技术和Western blotting技术分别进行两组海马锌离子含量和ZnT4表... 相似文献
40.
L. E. Lindblad R. R. Lorenz J. T. Shepherd P. M. Vanhoutte 《Cellular and molecular life sciences : CMLS》1984,40(12):1372-1373
Summary 1–3 h after prolonged (3–16 h) vibration (120 Hz, 0.2–0.3 mm amplitude) of rings of canine saphenous arteries there was no significant change in the contractile response to electrical stimulation, exogenous norepinephrine or of neuronal uptake of tritium labeled norepinephrine. These results did not provide evidence for persistent aftereffects of prolonged vibration.Acknowledgments. Supported in part by NIH grant HL 05883 and the Swedish Work Environmental Fund. 相似文献