全文获取类型
收费全文 | 553篇 |
免费 | 4篇 |
国内免费 | 4篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 12篇 |
2014年 | 17篇 |
2013年 | 20篇 |
2012年 | 20篇 |
2011年 | 13篇 |
2010年 | 13篇 |
2009年 | 17篇 |
2008年 | 22篇 |
2007年 | 20篇 |
2006年 | 19篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 15篇 |
1993年 | 10篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 22篇 |
1982年 | 25篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 1篇 |
排序方式: 共有561条查询结果,搜索用时 31 毫秒
11.
Francisco Romero Francisco Javier Caballero Francisco Castillo José Manuel Roldán 《Archives of microbiology》1985,143(2):111-116
Anti-glutamine synthetase serum was raised in rabbits by injecting purified glutamine synthetase (GS) of the phototrophic bacterium Rhodopseudomonas capsulata E1F1. The antibodies were purified to monospecificity by immunoaffinity chromatography in GS-sepharose gel. These anti-GS antibodies were used to measure the antigen levels in crude extracts from bacteria, grown phototrophically with dinitrogen, nitrate, nitrite, ammonia, glutamate, glutamine or alanine as nitrogen sources. The amount of GS detected by rocket immunoelectrophoresis was proportional to Mn2+-dependent transferase activity measured in the crude extracts. Addition of GS inhibitor l-methionine-d,l-sulfoximine (MSX) to the actively growing cells promoted increased antigen levels, that were not found in the presence of glutamine or chloramphenicol. The ammonia-induced decrease in GS relative levels was reverted by MSX. GS levels remained constant when phototrophically growing cells were kept in the dark.Abbreviations GS
glutamine synthetase
- MOPS
2-(N-morpholine) propane sulfonate
- MSX
l-methionine-d,l-sulfoximine 相似文献
12.
The effect of the glutamine synthetase (GS) inhibitor, methionine sulfoximine (MSO), on glutamate levels in, and glutamate release from, rat striatal tissue was examined. Tissue levels of glutamate were unchanged 24 h after an intraventricular injection of MSO, but tissue glutamine levels were decreased 50%. Calcium-dependent, potassium-stimulated glutamate release was diminished in tissue prisms from animals pretreated with MSO compared to controls. The decreased release of glutamate correlated over time with the inhibition of GS following an intraventricular injection of MSO. The maximum diminution of calcium-dependent, potassium-stimulated glutamate release (50%) and the maximum inhibition of GS activity (51%) were observed 24 h after MSO. The addition of 0.5 mM glutamine to the perfusion medium completely reversed the effects of MSO pretreatment on calcium-dependent, potassium-stimulated glutamate release. Since GS is localized in glial cells and the measured glutamate release is presumed to occur from neurons, the data support the contention that astroglial glutamine synthesis is an important contributor to normal neuronal neurotransmitter release. 相似文献
13.
The neuropeptides methionine enkephalin and FMRFamide, when injected into intact fiddler crabs, Uca pugilator, produce dark adaptation of the distal retinal pigment. Furthermore, both neuropeptides stimulate release of distal retinal pigment dark-adapting hormone activity from the isolated eyestalk neuroendocrine complex. It is hypothesized that both neuropeptides, when injected into intact fiddler crabs, act only indirectly on the distal retinal pigment, by stimulating release of this dark-adapting hormone. 相似文献
14.
Summary The distribution and characterization of the opioid octapeptide met5-enkephalin-arg6-gly7-leu8 (met5-enk-arg6-gly7-leu8) within the gastrointestinal tract of the rat has been determined by immunohistochemistry and radioimmunoassay by use of a newly developed antibody to met5-enk-arg6-gly7-leu8. With both techniques, met5-enk-arg6-gly7-leu8-immunoreactivity (met5-enk-arg6-gly7-leu8IR) was detected in all regions of the gastrointestinal (GI) tract except the esophagus. The highest concentration of immunoreactive met5-enk-arg6-gly7-leu8 was observed in the colon, while intermediate concentrations were found in the stomach, duodenum, jejunum, and ileum. Immunostained somata were observed chiefly in the myenteric plexus; immunostained processes were present primarily in the myenteric plexus and the circular muscle layer. This distribution pattern is similar to that previously observed with antiserum to met5-enkephalin-arg6-phe7 (met5-enk-arg6phe7). Chromatographic analysis of met5-enk-arg6-gly7leu8-immunoreactive peptides extracted from the GI tract revealed the presence of an immunoreactive peptide of high molecular weight which accounted for approximately three-quarters of met5-enk-arg6-gly7-leu8-IR in both stomach and colon. These findings suggest a role for peptides related to the octapeptide met5-enk-arg6-gly7-leu8 in the regulation of GI function. 相似文献
15.
Neuropeptide Y,enkephalin and noradrenaline coexist in sympathetic neurons innervating the bovine spleen 总被引:4,自引:0,他引:4
Dr. G. Fried L. Terenius E. Brodin S. Efendic G. Dockray J. Fahrenkrug M. Goldstein T. Hökfelt 《Cell and tissue research》1986,243(3):495-508
Summary The subcellular distribution of noradrenaline (NA), neuropeptide Y (NPY), Met and Leu-enkephalin (ENK), substance P (SP), somatostatin (SOM), and vasoactive intestinal polypeptide (VIP) was investigated in homogenates of bovine splenic nerve. The distribution of noradrenergic peptide-containing nerves in the bovine celiac ganglion, splenic nerve and terminal areas in spleen was studied by indirect immunofluorescence histochemistry using antisera to tyrosine hydroxylase (TH), dopamine--hydroxylase (DBH), NPY, enkephalin peptides, SP, SOM, VIP and peptide HI (PHI).After density gradient centrifugation, high levels of NPY and ENK-like immunoreactivity (LI) were found in high-density gradient fractions, coinciding with the main NA peak. SP, SOM and VIP were found in fractions with a lower density, VIP being also enriched in a heavy fraction; the latter three peptides were present in low concentrations.Immunohistochemistry revealed that staining for NPYLI and ENK-LI partly overlapped that for TH and DBH in celiac ganglia, splenic nerve axons and terminal areas of spleen. Almost all principal ganglion cells were TH- and DBH-immunoreactive. Many were also NPY-immunoreactive, whereas a smaller number were ENK-positive. In the celiac ganglion patches of dense SP-positive networks and some VIP/PHI- and ENK-immunoreactive fibers were seen around cell bodies.The results indicate that NPY and ENK are stored with NA in large dense-cored vesicles in unmyelinated axons of bovine splenic nerve. SP, SOM and VIP appear in different organelles in axon populations separate from sympathetic noradrenergic nerves. 相似文献
16.
The cyanobacteria Anabaena variabilis and Nostoc CAN showed a biphasic pattern of 14CH3NH
3
+
uptake at external pH values of 7.0 and 9.0. The initial phase of uptake, which was independent of metabolism of 14CH3NH
3
+
, was attributed to uptake via a CH3NH
3
+
(NH
4
+
) transport system at pH 7.0 and probably to passive diffusion of uncharged CH3NH2 and trapping by protonation at pH 9.0. The second slower phase of uptake was attributed to metabolism of CH3NH
3
+
via glutamine synthetase to form -methylglutamine which accumulates. Anabaena cylindrica showed an initial rapid uptake at pH 7.0 and pH 9.0 but metabolism of 14CH3NH
3
+
was undetectable at pH 7.0 and was barely detectable at pH 9.0. Pretreatment of A. variabilis with l-methionine-d,l-sulphoximine to inactivate glutamine synthetase, inhibited the second phase of 14CH3NH
3
+
uptake at both pH 7.0 and pH 9.0 and the accumulation of -methylglutamine but had no effect on the first phase of uptake. Following transfer of A. variabilis to darkness the initial phase of 14CH3NH
3
+
uptake at pH 7.0 and 9.0 was unaffected but the subsequent metabolism via glutamine synthetase was inhibited.Abbreviations MSX
l-methionine-d,l-sulphoximine
- GS
glutamine synthetase 相似文献
17.
Liposome-mediated labeling of adrenocorticotropin fragments parallels their biological activity 总被引:2,自引:0,他引:2
To test our hypothesis that specific interactions of ACTH peptides with model lipid membranes reflect the biological importance of similar interactions on target cells, we investigated the liposome-mediated labeling of ACTH fragments with the extremely hydrophobic photolabel, 3-trifluoromethyl-3-(m-[125I]iodophenyl)diazirine. Correlations were found between the labeling rates and the agonistic and antagonistic potencies of the peptides for in vitro steroidogenesis and inhibition of a synaptosomal protein kinase. A model for the cross-reactivity between ACTH and opioid peptides is discussed. 相似文献
18.
Abstract: Stores of methionine-enkephalin were labelled on the N -terminal by incubation of whole brain slices with [3 H]tyrosine (10 °Ci/ml). The 3 H radioactivity corresponding to the position of authentic Met-enkephalin after extraction on Amberlite XAD2 and separation by thin-layer chromatography was taken as an index of synthesis. Maximal incorporation of the labelled tyrosine into Met-enkephalin was attained after 4 h of incubation at 37°C and was inhibited in the presence of 10 μ M cycloheximide. Isolated nerve terminals failed to incorporate any [3 H]tyrosine. The labelled compound had opiatelike activity and consisted of the same five amino acids as an authentic standard. Incubations with leucine aminopeptidase indicated that the labelled tyrosine was on the N -terminus and removal of this tyrosine resulted in loss of opiate-like activity. The incorporation of [14 C]glycine, selected as an alternative precursor, was consistent with de novo synthesis and not N -terminal exchange. A radioimmunoassay was also used to quantify the amount of labelled Met-enkephalin. KCl (50 m M ) elicited a Ca2+ -dependent release of the synthesised [3 H]Met-enkephalin from whole brain slices and also from isolated nerve terminals. The release of Met-enkephalin radioimmunoactivity paralleled that of [3 H]met-enkephalin. Preliminary investigations have suggested that carbamyl choline inhibited this release and its effect was partially reversed by atropine. 相似文献
19.
The levels of amino acids in globus pallidus, a structure heavily innervated with gamma-aminobutyric acid (GABA)-ergic terminals but few glutamergic terminals, were compared with the levels in neostriatum, a structure richly innervated with glutamergic terminals but intermediate in GABAergic terminals. The level of glutamate in neostriatum was twice as high as in globus pallidus whereas the level of GABA in globus pallidus was three times higher than in neostriatum. The level of aspartate was similar in both regions whereas the level of glutamine was correlated with the level of glutamate. Methionine sulfoximine, a glutamine synthetase inhibitor, reduced the level of glutamine to 10-20% of control in both structures. This reduction was accompanied by the largest decrease in the level of glutamate in neostriatum, indicating that transmitter glutamate turns over more rapidly than other glutamate pools. Likewise, insulin decreased the levels of glutamate and glutamine more in neostriatum than in globus pallidus. gamma-Vinyl GABA increased the level of GABA in globus pallidus more than in neostriatum although the percent increase was largest in neostriatum. Treatment with gamma-vinyl GABA was accompanied by a large reduction in the level of GABA, indicating that a substantial proportion of the glutamine pool is linked to GABA metabolism. 相似文献
20.
M. Torras-Llort R. Ferrer J.F. Soriano-García M. Moretó 《The Journal of membrane biology》1996,152(3):183-193
The properties of l-lysine transport in chicken jejunum have been studied in brush border membrane vesicles isolated from 6-wk-old birds. l-lysine uptake was found to occur within an osmotically active space with significant binding to the membrane. The vesicles
can accumulate l-lysine against a concentration gradient, by a membrane potential-sensitive mechanism. The kinetics of l-lysine transport were described by two saturable processes: first, a high affinity-transport system (K
mA= 2.4 ± 0.7 μmol/L) which recognizes cationic and also neutral amino acids with similar affinity in the presence or absence
of Na+ (l-methionine inhibition constant KiA, NaSCN = 21.0 ± 8.7 μmol/L and KSCN = 55.0 ± 8.4 μmol/L); second, a low-affinity transport mechanism (KmB= 164.0 ± 13.0 μmol/L) which also recognizes neutral amino acids. This latter system shows a higher affinity in the presence
of Na+ (KiB for l-methionine, NaSCN = 1.7 ± 0.3 and KSCN = 3.4 ± 0.9 mmol/L). l-lysine influx was significantly reduced with N-ethylmaleimide (0.5 mmol/L) treatment. Accelerative exchange of extravesicular labeled l-lysine was demonstrated in vesicles preloaded with 1 mmol/L l-lysine, l-arginine or l-methionine. Results support the view that l-lysine is transported in the chicken jejunum by two transport systems, A and B, with properties similar to those described
for systems b
0,+ and y+, respectively.
Received: 14 August 1995/Revised: 2 April 1996 相似文献