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991.
Effect of norepinephrine and dibutyryl cyclic AMP on S-100 protein level in C6 glioma cells 总被引:6,自引:0,他引:6
S-100 Protein level was determined in C6 glioma cells after treatments by norepinephrine. In growing cells norepinephrine induces an important increase of S-100 protein level continuing during the stationary phase to reach a level higher than in untreated quiescent cells. In quiescent, low density, thymidine blocked cells, S-100 protein level is also enhanced by norepinephrine. In high density, contact inhibited cells, S-100 protein level is not modified although cAMP level is much more stimulated by norepinephrine than is low density cells. Exogenous addition of dibutyryl cyclic AMP mimics the effects of norepinephrine.Our results suggest that cyclic AMP level can mudulate S-100 protein level in C6 cells but that in density inhibited cells, a subsequent step involved in the regulation is no more operative. 相似文献
992.
H E Claesson 《FEBS letters》1982,139(2):305-308
993.
Sobhy R. Ayad Richard J. Hughes 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,630(2):193-201
One of the characteristics of malignant cells is a poor response to hormones and a low level of cyclic AMP. Whilst this is true of intact P388 mouse lymphoma cells, high levels of adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) activity can be measured in particulate preparations of these cells. When ATP is added to the incubation medium of intact lymphoma cells, the cyclic AMP level is enhanced. This effect of ATP is not mediated by adenosine, nor is it enhanced by NaF. The ATP content of the lymphoma cells is much lower than that of CH23 Chinese hamster fibroblast and PCM3 hybrid cells, whose cyclic AMP levels are not affected by the presence of ATP. This suggests that adenylate cyclase, in the lymphoma cells, is bathed in a pool which is deficient in substrate. The substrate concentration of this pool is thought to be elevated by addition of ATP to the incubation medium with ATP, itself, crossing the plasma membrane. 相似文献
994.
G. Burke 《Prostaglandins & other lipid mediators》1973,3(3):291-297
We have shown that TSH increases PG levels in isolated bovine thyroid cells. We now report that TSH also increases PG levels in rat and mouse thyroid, and that these effects may be mediated via cyclic AMP. PG and cyclic AMP levels in intact rat and mouse thyroid lobes were measured by radioimmunoassay. During 60-min incubations at 37°C, 25 mU/ml TSH effected a 75–83% increase in PGE1 and PGF2α ”equivalents“ in rat thyroid; parallel measurements of endogenous cyclic AMP in these intact thyroid lobes revealed that maximal TSH-induced increase in cyclic AMP also required 60-min incubations. In mouse thyroid, 5 mU/ml TSH increased PGE1 and PGF2α levels 38–82% above basal; this TSH effect was evident within 15 min of incubation, thus mimicking the time-course of TSH-induced increase in mouse thyroid cyclic AMP. Exogenous DBcAMP, 0.5 to 3 mM, effected a dose-related increase in mouse thyroid PG levels. The stimulatory effects of both TSH and DBcAMP on mouse thyroid PG levels were abolished by aspirin and indomethacin. These studies suggest that TSH-induced increase in endogenous PG levels in thyroid may be mediated by cyclic AMP. 相似文献
995.
Pituitary adenylate cyclase activating peptide (PACAP) is a peptide that is present in the hypothalamus and other areas of the rat brain. This study demonstrates that PACAP reduces food intake after intracerebroventricular injection in food-deprived mice. Behavioral analysis suggests that this decrease in food intake is, in part, compensated for by an increase in other behaviors. Pituitary adenylate cyclase activating peptide also was demonstrated to antagonize increased food intake resulting from administration of neuropeptide Y. Thus, PACAP joins a growing list of neuropeptides involved in the central regulation of food intake. 相似文献
996.
Cyclic peptides form an interesting class of compounds for study by conformational analysis, by virtue of their unique conformational
features and biological properties. The small cyclic peptides having 3-6 peptide units in their ring, show a variety of conformational
characteristics such as occurrence ofcis peptide units, flexibility of peptide dimension and variety in hydrogen bonding. The different possible conformations of
cyclic tri- and hexa-peptides are given and certain specific conformational features are discussed for cyclic tetra and pentapeptides.
For higher cyclic peptides, the hydrogen bonding requirement for stability of the backbone of the ring, is seen to be kept
to a minimum. These various features and their significance are examined and discussed in the light of energy minimization
studies and analysis of available experimental data. 相似文献
997.
This study was carried out to investigate possible interactions between some glutamatergic agonists and the peptide α-MSH upon the cyclic AMP levels. We used an in vitro tissue slice preparation incubated in the presence of different glutamatergic agonists such as N-methyl-
-aspartic acid (NMDA), quisqualic acid (QUIS), kainic acid (KA), and the peptide α-MSH together with each agonist. Slices containing caudate putamen and accumbens were chosen according to neurochemical data indicating that the striatum contains a moderate amount of MSH binding sites and also receives glutamatergic innervation. Exposure of these slices to either MSH or to the agonists NMDA or QUIS resulted in an increase in the cAMP levels in relation to controls. Nevertheless, incubation with KA resulted in no changes in the nucleotide levels. The combination of MSH/NMDA induced a reduction of cAMP levels in relation to those obtained with NMDA alone. The combinations of QUIS/MSH or KA/MSH also induced variations in the values of nucleotide in relation to the those obtained with the peptide alone or with the corresponding agonist; these changes were related to the dose of agonist used in each case. The results obtained in these experiments suggest the existence of some interaction between the peptide and the agonist used. 相似文献
998.
George Britton Raj Kumari Singh Trevor W. Goodwin Avraham Ben-Aziz 《Phytochemistry》1975,14(11):2427-2433
The presence of β-carotene, lycopene, rhodopin, rhodovibrin, anhydrorhodovibrin, spirillox-anthin, ‘monodemethylated spirilloxanthin’ and ‘dihy 相似文献
999.
HELEN L. GREENWOOD 《The Journal of eukaryotic microbiology》1973,20(2):305-307
SYNOPSIS. Gibberellin A7 and cyclic AMP increased mating efficiency of Chlamydomonas reinhardtii when the cells were treated during gametogenesis. No change in mating activity was observed when cells were treated with 5′-AMP. Actinomycin D inhibited both normal mating and gibberellin-stimulated mating. 相似文献
1000.
Annie F. Prigent G. Némoz H. Pacheco 《Biochemical and biophysical research communications》1980,95(3):1080-1089
Cyclic nucleotide phosphodiesterase was purified over 200-fold in a single step from the rat heart cytosolic fraction, using affinity chromatography on phenylbutenolide inhibitor immobilized to AH Sepharose. After elimination of the contaminating proteins by washing with the loading buffer and then with 0.4 M KCl buffer, without any loss in enzymatic activity, the cyclic nucleotide phosphodiesterase was eluted in good zields with a linear KCl gradient from 0.4 M to 1.8 M. Enzymatic activity determination performed with both cyclic AMP and cyclic GMP as substrate, either at low (0.25 μM) or at high (25 μM) concentration, pointed out the presence of several phosphodiesterase forms with different substrate specificities, in the elution profiles. 相似文献