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排序方式: 共有213条查询结果,搜索用时 15 毫秒
1.
M Camacho Ochoa T A Jackson C S Aaron R A Lahti G M Strain P F Von Voigtlander 《Life sciences》1992,51(14):1135-1143
A morphometric study of kainic acid- (KA) induced lesions was designed for the study of the interaction of the diamines U-5449A and U-50488H with excitatory amino acids, and the dose-response relationship thereof. IC50S determined for binding at the kappa receptor and other opioid receptors demonstrated the lack of kappa activity of U-54494A, a structurally related analog of U-50488H. Both opiate kappa receptor related anticonvulsant diamines were tested for their ability to protect the mouse hippocampus from the cytopathological changes induced by KA in neurons and glia. The damage observed with i.c.v. KA in mouse was restricted to neurons of the CA3 pyramidal region and glia of the hippocampus. It involved massive cell loss and shrunken neurons with dark cytoplasm and nuclei. Groups treated with combinations of KA and U-54494A or U-50488H showed scarce damage, but patches of necrotic changes were still observed. Control animals treated with saline (i.c.v.) and U-54494A (s.c.) or U-50488H (s.c.) did not suffer any noticeable alterations of the polymorphic layers of the hippocampal formation. Image analysis of the CA3 area of the hippocampus was used to quantitate the vacuolization induced by KA lesions in the control and treated groups. By this method, both U-54494A and U-50488H were shown to protect this area in a dose-related fashion as evidenced by reduced vacuolization. The anticonvulsant properties of these compounds may result in the antagonism of the excitotoxic lesions. More specifically, the ability of these diamines to block depolarization-induced influxes of Ca++ may protect the CA3 cells from the cytotoxic effects of persistent depolarization. 相似文献
2.
Several investigators have observed that sodium ion enhances the binding of naloxone to opioid receptors. This effect has generally been attributed to allosteric modulation of the state of the mu receptor. However, a recent claim has been made that the enhancement does not involve a change in the mu receptor, but instead occurs because naloxone becomes a more kappa-specific drug when sodium ion is present in high concentration. Since the claim was not based on experimental evidence from binding studies involving known high-affinity kappa ligands, we have investigated the competition of naloxone for the kappa site using [3H]U-69593 as the marker for receptor binding. Assays were carried out in the presence and absence of 100 mM NaCl. The results of the study indicate that sodium ion does not increase the affinity of naloxone or U-69593 for the kappa receptor. 相似文献
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5.
H U M?sch B Scheier R Lahti P M?nts?la G H Braus 《The Journal of biological chemistry》1991,266(30):20453-20456
6.
R Lahti K Pohjanoksa T Pitk?ranta P Heikinheimo T Salminen P Meyer J Heinonen 《Biochemistry》1990,29(24):5761-5766
Analysis of the conservation of functional residues between yeast and Escherichia coli inorganic pyrophosphatases (PPases) suggested that Asp-97, Glu-98, Asp-102, and Lys-104 are important for the action of E. coli PPase [Lahti, R., Kolakowski, L. F., Heinonen, J., Vihinen, M., Pohjanoksa, K., & Cooperman, B. S. (1990) Biochim. Biophys. Acta 1038, 338-345]. We replaced these four residues by oligonucleotide-directed mutagenesis, giving variant PPases DV97, DE97, EV98, DV102, DE102, KI104, and KR104. PPase variants DV97, DV102, and KI104 had no enzyme activity, whereas PPase variants DE97, EV98, DE102, and KR104 had 22%, 33%, 3%, and 3% of the wild-type PPase activity, respectively. This suggests that Asp-97, Asp-102, and Lys-104 are essential for the catalytic activity of E. coli PPase. PPase variants DV98 and KR104 also had an increased sensitivity to heat denaturation; incubation of these mutant PPases at 75 degrees C for 15 min in the presence of 5 mM magnesium ion decreased the activity to 20% and 1%, respectively, of the initial value while 74% of the activity was observed with wild-type PPase. Furthermore, these thermolabile mutant PPases displayed the most profound conformational changes of the PPase variants examined, as demonstrated by the binding of the fluorescent dye Nile red that monitors the hydrophobicity of protein surfaces. Accordingly, Glu-98 and Lys-104 seem to be important for the structural integrity of E. coli PPase. 相似文献
7.
Gold salts and phenylbutazone selectively inhibit the synthesis of PGF2α and PGE2 respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE2 and PGF2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action
and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function. 相似文献
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9.
Activity changes of inorganic pyrophosphatase of Streptococcus faecalis during batch culture 总被引:2,自引:0,他引:2
The state of inorganic pyrophosphatase (EC 3.6.1.1) from Streptococcus faecalis ATCC 8043 was studied in different phases of batch culture. The degree of inactivation (i.e. the ratio of activities observed before and after incubation at 37 degrees C without cysteine) was highest, and the degree of activation (i.e. the ratio of activities after and before incubation in the presence of cysteine) was lowest, in samples taken during the early-exponential growth phase. During the various phases of batch culture, the specific activity before incubation and the degree of inactivation changed in parallel, whereas the specific activity observed after incubation remained nearly constant. During the early-exponential phase of growth almost all the enzyme was in the high-activity form, whereas during the stationary phase the highly active and the less active forms existed in equal amounts. These findings suggest that inorganic pyrophosphatase in S. faecalis is synthesized constitutively and is primarily regulated at the level of activity. 相似文献
10.
Alexander A. Baykov Anssi M. Malinen Heidi H. Luoto Reijo Lahti 《Microbiology and molecular biology reviews》2013,77(2):267-276