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排序方式: 共有181条查询结果,搜索用时 343 毫秒
51.
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
52.
在光周期不变的情况下,使光周期中的暗时相与温度周期中的冷时相相同步时,亚洲玉米螟Ostriniafurnacalis(Guenee')(Lepidoptera:Pyralidae)的滞育率就高;而当光周期中的暗时相与温度周期中的温时相相同步时,不足育的发生率就低。 相似文献
53.
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
54.
鉴于传统制造业企业仓储分类方法分类边界不明确、难以适应现代企业信息化发展趋势的问题,提出了基于聚类算法的ABC库存分类算法,提升了传统库存分类模型的分类精度和效率。以某电力制造业企业的库存产品数据为研究对象,结合聚类算法与ABC分类法提出了适用于实际研究场景的评价函数,并给出了新的基于k-means 算法的ABC分类法。采用该分类模型对库存环网柜产品进行分类,并基于ERP系统中存储的产品数据将库存环网柜产品分为A、B、C三类,根据分类结果对不同类别的环网柜产品采取不同的库存控制策略。研究结果表明,将数据挖掘算法应用于库存管理实现了企业库存管理决策的科学化和智能化。 相似文献
55.
S. Wilde E. Schlatter H. Koepsell B. Edemir S. Reuter H. Pavenstädt U. Neugebauer R. Schröter S. Brast G. Ciarimboli 《Cellular and molecular life sciences : CMLS》2009,66(10):1729-1740
In this work, regulation of organic cation transporter type 2 from rat (rOCT2) stably transfected in HEK293 cells was investigated
by microfluorimetry with 4-(4-(dimethylamino)styryl)-N-methylpyridinium as substrate. The transport mediated by rOCT2 was
specifically stimulated by PKA, phosphatidylinositol-3-kinase, p56lck tyrosine kinase, mitogen-extracellular-signal-regulated-kinase-1/2, calmodulin (CaM), and CaM-kinase-II. The regulatory pattern
of rOCT2 differs markedly quantitatively and qualitatively from that of other OCT isoforms. Only CaM-dependent upregulation
is conserved throughout the OCT family. For this reason, CaM regulation of rOCT2 was also investigated in isolated S3-segments
(known to express only rOCT2) of male and female rat proximal tubules. Inhibition of CaM by calmidazolium significantly decreased
rOCT2 activity (−49.0 ± 13.6%, n = 4) in male but not female (9.0 ± 13.0%, n = 4) rats. Real-time PCR and Western blot investigations
of CaM expression in rat kidneys showed that male animals have significantly higher CaM expression. This is the first study
describing post-translational gender-dependent rOCT2 regulation.
Received 26 February 2009; accepted 16 March 2009 相似文献
56.
G. Zhao X.-W. Zheng G.-W. Qin Y. Gai Z.-H. Jiang L.-H. Guo 《Cellular and molecular life sciences : CMLS》2009,66(9):1617-1629
Cocktail recipes containing Psoralea corylifolia seeds (PCS) are used to empirically treat Parkinson disease. A PCS isolate Δ3,2-hydroxybakuchiol (BU) can inhibit dopamine uptake in dopamine transporter (DAT) transfected Chinese hamster ovary (CHO)
cells, and dopamine reuptake blockade may provide an alternative approach for ameliorating parkinsonism. Here, we assessed
the potential dopaminergic neuroprotective, and antiparkinsonian-like activity of BU. BU sample size was increased by using
a scale-up extraction paradigm. Pharmacologically, BU significantly protected SK-N-SH cells from 1-methyl-4-phenylpyridinium
(MPP+) insult, produced striking inhibitory actions on dopamine/norepinephrine uptake and WIN35,428 binding in synaptosomes on
in vivo administration, and significantly preventing poor performance on rotarod and dopaminergic loss in substantia nigra in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine
(MPTP) mice. BU acts by protecting dopaminergic neurons from MPP+ injury and preventing against MPTP-induced behavioral and histological lesions in the Parkinson’s disease (PD) model, possibly
by inhibiting monoamine transporters. These findings suggest that BU could be meaningful in PD treatment.
Received 14 January 2009; received after revision 22 February 2009; accepted 10 March 2009 相似文献
57.
Atomic model of human cystic fibrosis transmembrane conductance regulator: Membrane-spanning domains and coupling interfaces 总被引:2,自引:0,他引:2
We describe herein an atomic model of the outward-facing three-dimensional structure of the membrane-spanning domains (MSDs) and nucleotide-binding domains (NBDs) of human cystic fibrosis transmembrane conductance regulator (CFTR), based on the experimental structure of the bacterial transporter Sav1866. This model, which is in agreement with previous experimental data, highlights the role of some residues located in the transmembrane passages and directly involved in substrate translocation and of some residues within the intracellular loops (ICL1-ICL4) making MSD/NBD contacts. In particular, our model reveals that D173 ICL1 and N965 ICL3 likely interact with the bound nucleotide and that an intricate H-bond network (involving especially the ICL4 R1070 and the main chain of NBD1 F508) may stabilize the interface between MSD2 and the NBD1F508 region. These observations allow new insights into the ATP-binding sites asymmetry and into the molecular consequences of the F508 deletion, which is the most common cystic fibrosis mutation. 相似文献
58.
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
59.
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
60.
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