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131.
Patrick Doherty Josie Furness Emma J. Williams Frank S. Walsh 《Journal of neurochemistry》1994,62(6):2124-2131
Abstract: Activation of tyrosine kinases is established as an important mechanism for controlling growth cone motility and neurite outgrowth. We have tested the effects of a range of tyrosine kinase inhibitors on neurite outgrowth from postnatal day 4 cerebellar granule cells cultured over confluent monolayers of 3T3 fibroblasts. The only agent that had any effect was herbimycin A, which stimulated neurite outgrowth. The response is shown to be attributable to a direct effect of this tyrosine kinase inhibitor on neurones. The neurite outgrowth response to herbimycin A was inhibited by two other tyrosine kinase inhibitors, which on their own did not affect neurite outgrowth. The data suggest that the response to herbimycin A reflects either a direct or indirect activation of one or more protein tyrosine kinases. Independent signalling events downstream from tyrosine kinase activation underlying the neurite outgrowth response to herbimycin A include increased activity of protein kinase C and calcium influx into neurones through both N-and L-type calcium channels. 相似文献
132.
Depolarization and Neurotransmitters Increase Neuronal Protein Tyrosine Phosphorylation 总被引:5,自引:2,他引:3
Julio C. Siciliano Michèle Gelman Jean-Antoine Girault 《Journal of neurochemistry》1994,62(3):950-959
Abstract: In rat hippocampal slices and in neurons in primary culture, K+ -induced depolarization increased markedly and rapidly tyrosine phosphorylation of a 110-kDa protein (pp110) and, to a lesser degree, of a 120-kDa protein (pp120), in a calcium-dependent fashion. Qlutamate, 1-aminocyclopentane- trans -1,3-dicarboxylic acid (an agonist of metabotropic glutamate receptors), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (an agonist of ionotropic glutamate receptors) stimulated also tyrosine phosphorylation of pp110 and pp120. These effects were not observed in astrocytes in primary culture. In hippocampal slices tyrosine phosphorylation of pp110 and pp120 was stimulated by Ca2+ -ionophores and by phorbol esters and antagonized by a chelator of intracellular Ca2+ and by drugs that inhibit protein kinase C. Stimulation of muscarinic and α1 ,-adrenergic receptors increased also tyrosine phosphorylation of pp110 and pp120. These results demonstrate that membrane depolarization and stimulation of neurotransmitter receptors activate a tyrosine phosphorylation pathway in neurons. This pathway involves an increase in intracellular Ca2+ concentrations and the activation of protein kinase C. It may provide a biochemical basis for some neurotrophic effects of electrical activity and neurotransmitters and may contribute to the role of tyrosine phosphorylation in long-term potentiation. 相似文献
133.
Summary The kinetics of putrescine and spermidine uptake and the influence of calcium on the kinetic parameters of the transport process were investigated in protoplasts isolated from carrot phloem parenchyma. Spermidine uptake dependence on external concentration was biphasic, both in the absence and in the presence of 1 mM CaCl2. In the first case, saturation was reached at 0.1 to 0.25 mM and the Km value was 43µM. When calcium was added, the Km and Vmax increased. A similar pattern was found with regard to putrescine uptake. Moreover, in order to clarify the mode of action of calcium on polyamine uptake, lanthanides (lanthanum and gadolinium) were utilised as Ca+2-channel antagonists. When protoplasts were preincubated with these lanthanides, the stimulatory effect exerted by Ca+2 on polyamine uptake was almost totally abolished. On the other hand, if lanthanum was supplied instead of calcium, it gave rise to a small enhancement of polyamine transport. These results induce us to suggest that calcium acts on polyamine uptake both by binding to external sites on the plasmalemma and by penetrating into the cell. 相似文献
134.
Summary The structure-activity data of 6 years on 395 analogs of the luteinizing hormone releasing hormone (LHRH) have been studied to determine effective substituents for the ten positions for maximal antiovulatory activity and minimal histamine release. The numbers of substituents studied in the ten positions are as follows: (41)1-(12)2-(12)3-(5)4-(47)5-(52)6-(16)7-(18)8-(4)9-(8)10. In position 1, DNal and DQal were effective with the former being more frequently the better substituent. DpClPhe was uniquely effective in position 2. Positions 3 and 4 are very sensitive to change. D3Pal in position 3 and Ser in position 4 of LHRH were in the best antagonists. PicLys and cPzACAla were the most successful residues in position 5 with cPzACAla being the better substituent. Position 6 was the most flexible and many substituents were effective; particularly DPicLys. Leu7 was most often present in the best antagonists. In position 8, Arg was effective for both antiovulatory activity and histamine release; ILys was effective for potency and lesser histamine release. Pro9 of LHRH was retained. DAlaNH2
10 was in the best antagonists.Abbreviations AABLys
N
-(4-acetylaminobenzoyl)lysine
- AALys
N
-anisinoyl-lysine
- AAPhe
3-(4-acetylaminophenyl)lysine
- Abu
2-aminobutyric acid
- ACLys
N
-(6-aminocaproyl)lysine
- ACyh
1-aminocyclohexanecarboxylic acid
- ACyp
1-aminocyclopentanecarboxylic acid
- Aile
alloisoleucine
- AnGlu
4-(4-methoxy-phenylcarbamoyl)-2-aminobutyric acid
- 2ANic
2-aminonicotinic acid
- 6ANic
6-aminonicotinic acid
- APic
6-aminopicolinic acid
- APh
4-aminobenzoic acid
- APhe
4-aminophynylalanine
- APz
3-amino-2-pyrazinecarboxylic acid
- Aze
azetidine-2-carboxylic acid
- Bim
5-benzimidazolecarboxylic acid
- BzLys
N
-benzoyllysine
- Cit
citrulline
- Cl2Phe
3-(3,4-dichlorphenyl)alanine
- cPzACAla
cis-3-(4-pyrazinylcarbonylaminocyclohexyl)alnine
- cPmACAla
cis-3-[4-(4-pyrimidylcarbonyl)aminocyclohexyl]alanine
- Dbf
3-(2-dibenzofuranyl)alanine
- DMGLys
N
-(N,N-dimethylglycyl)lysine
- Dpo
N
-(4,6-dimethyl-2-pyrimidyl)-ornithine
- F2Ala
3,3-difluoroalanine
- hNal
4-(2-naphthyl)-2-aminobutyric acid
- HOBLys
N
-(4-hydroxybenzoyl)lysine
- hpClPhe
4-(4-chlorophenyl)-2-amino-butyric acid
- Hse
homoserine, 2-amino-4-hydroxybutanoic acid
- ICapLys
N
-(6-isopropylaminocaproyl)lysine
- ILys
N
-isopropyllysine
- Ind
indoline-2-carboxylic acid
- INicLys
N
-isonicotinoyllysine
- IOrn
N
-isopropylornithine
- Me3Arg
NG,NG,NG-trimethylarginine
- Me2Lys
N
,N
-dimethyllysine
- MNal
3-[(6-methyl)-2-naphtyl]alanine
- MNicLys
N
-(6-methylpicolinoyl)lysine
- MPicLys
N
-(6-methylpicolinoyl)lysine
- MOB
4-methoxybenzoyl
- MpClPhe
N-methyl-3-(4-chlorphenyl)lysine
- MPZGlu
glutamic acid,-4-methylpiperazine
- Nal
3-(2-naphthyl)alanine
- Nap
2-naphthoic acid
- NicLys
N
-nicotinoyllysine
- NO2B
4-nitrobenzoyl
- NO2Phe
3-(4-nitrophenyl)alanine
- oClPhe
3-(2-chlorphenyl)alanine
- Opt
O-phenyl-tyrosine
- Pal
3-(3-pyridyl)alanine
- 2Pal
3-(2-pyridyl)alanine
- 2PALys
N
-(3-pyridylacetyl)lysine
- pCapLys
N
-(6-picolinoylaminocaproyl)lysine
- pClPhe
3-(4-chlorophenyl)alanine
- pFPhe
3-(4-fluorophenyl)-alanine
- Pic
picolinic acid
- PicLys
N
-picolinoyllysine
- Pip
piperidine-2-car-boxylic acid
- PmcLys
N
-(4-pyrimidylcarbonyl)lysine
- Ptf
3-(4-trifluromethyl phenyl)alanine
- Pz
pyrazinecarboxylic acid
- PzAla
3-pyrazinylalanine
- PzAPhe
3-(4-pyrazinylcarbonylaminophenyl)alanine
- Qal
3-(3-quinolyl)alanine
- Qnd-Lys
N
-quinaldoyllysine
- Qui
3-quinolinecarboxylic acid
- Qux
2-quinoxalinecarboxylic acid
- Tic
1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid
- TinGly
2-thienylglycine
- tNACAla
trans-3-(4-nicotinoylaminocyclohexyl)-alanine
- tPACAla
trans-3-(4-picolinoylaminocyclohexyl)alanine 相似文献
135.
Influence of copper on proton efflux from Saccharomyces cerevisiae and the protective effect of calcium and magnesium 总被引:1,自引:0,他引:1
Abstract The inhibitory effect of Cu on glucose-dependent H+ efflux from Saccharomyces cerevisiae was manifest at low (micromolar) concentrations, with the time period between the addition of glucose and commencement of H+ efflux, H+ efflux rate and duration all being affected with increasing Cu concentration (5–100 μM). Ca, at a concentration of 0.5 mM, completely removed the inhibitory effect of Cu at concentrations up to 50 μM and considerably reduced it at higher concentrations (up to 150 μM). Mg exhibited a similar but weaker protective effect against the influence of Cu. The protective effect of Ca against 50 μM Cu was evident at low Ca concentrations (2.5–5 μM), whereas Mg was effective at ≥50 μ M. In order to prevent the inhibitory effect of Cu, it was necessary to add Ca or Mg to the cell suspension before Cu addition. It is concluded that the protective effect of Ca and Mg is mediated by competitive and stabilizing interactions at the cell surface as well as physiological functions of Ca and Mg. 相似文献
136.
The trimeric derivative of 16,16-dimethyl-15-dehydroprostaglandin B1 (termed tri-Calciphor), which protects tissues against ischemic damage, induced Ca2+ efflux and swelling in mitochondria in the absence of phosphate, Mg2+ and ATP. When glutamate/malate rather than succinate was the substrate, higher tri-Calciphor concentrations were required for the ionophoretic activity. Ca2+ efflux and mitochondrial swelling induced by tri-Calciphor were completely inhibited by ATP, phopsphate and Mg2+ added together, and partially inhibited with phosphate plus either ATP or Mg2+. Between 0 and 7 μM added Ca2+ and in the presence of phosphate, ATP and Mg2+, tri-Calciphor stimulated the uptake of Ca2+ by mitochondria and increased the efficiency of buffering of extramitochondrial Ca2+. Thus depending on the assay conditions, two different effects involving Ca2+ movements and mitochondria are observed with tri-Calciphor. 相似文献
137.
M. V. Wright N. Elwess J. van Houten 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(4):288-296
Intracellular Ca2+ levels in Paramecium must be tightly controlled, yet little is understood about the mechanisms of control. We describe here indirect evidence that a phosphoenzyme intermediate is the calmodulin-regulated plasma membrane Ca2+ pump and that a Ca2+-ATPase activity in pellicles (the complex of cell body surface membranes) is the enzyme correlate of the plasma membrane pump protein. A change in Ca2+ pump activity has been implicated in the chemoresponse of paramecia to some attractant stimuli. Indirect support for this is demonstrated using mutants with different modifications of calmodulin to correlate defects in chemoresponse with altered Ca2+ homeostasis and pump activity.Abbreviations EGTA
ethyleneglycol tetra-acetate
- ER
endoplasmic reticulum
- IBMX
isobutyl methylxanthine
-
I
che
index of chemokinesis
- Mops
3-[N-morpholino] propanesulfonic acid
- PEI
phosphoenzyme intermediate
- STEN
sucrose, TRIS, EDTA, sodium chloride
- TCA
trichloroacetic acid
- TRIS
tris[hydroxymethyl] aminomethane 相似文献
138.
A. M. Coimbra K. G. Ferreira P. Fernandes H. G. Ferreira 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(3):196-202
Electrical potential differences between the haemolymph and the extrapallial fluid, and between the haemolymph and the mantle cavity fluid, and ionic concentrations of calcium in the haemolymph and in extrapallial fluid were measured in vivo in Anodonta cygnea. The electrochemical potential of ionic calcium in the haemolymph is clearly above the electrochemical potential of ionic calcium in the environment and is very nearly in equilibrium with that of the extrapallial fluid. Simultaneous measurements of carbon dioxide partial pressure and pH in the extrapallial fluid showed that in this compartment ionic calcium is clearly above saturation. It is proposed that calcium deposition is regulated through the secretion of the organic matrix and by controlling the pH and the carbon dioxide partial pressure of the extrapallial fluid. An estimation of the minimum positive balance of calcium required to sustain shell growth together with the electrophysiological characterization of the mantle cavity epithelium showed that this tissue is not the route of entry of calcium into the animal.Abbreviations BW
body weight
- DW
dry weight
- EEPF-S
chemical potential difference
- EPF
extrapallial fluid
- Gtot
total conductance
- Isc
short-circuit current
- Ksp
solubility product
- MCE
mantle cavity epithelium
- MCF
mantle cavity fluid
- OME
outer mantle epithelium
- PCO2
partial pressure of carbon dioxide
- PVC
Poly(vinyl chloride)
- S
shell
- SEM
standard error of mean
-
V
ic
intracellular electrical potential
-
V
oc
open-circuit voltage 相似文献
139.
C. JIMNEZ-CERVANTES F SOLANO J.A. LOZANO J.C. GARCIA-BORR
N 《Pigment cell & melanoma research》1994,7(5):291-297
Two forms of tyrosinase from B16 mouse melanoma were identified by nonreducing SDS-PAGE after solubilization of crude melanosomal preparations with the nonionic detergent Brij 35. These forms, named LEMT and HEMT (low and high electrophoretic mobility tyrosinase, respectively), were purified by a combination of differential detergent extraction and chromatographic techniques. They displayed tyrosine hydroxylase and dopa oxidase activity and were stereospecific and sensitive to phenylthiourea, proving that they are true tyrosinases. However, based on its kinetic parameters, HEMT is a much more efficient enzyme, Immunoprecipitation and Western blots performed with the specific antibody αPEP1, directed against the b protein carboxyl terminus, suggested that LEMT is identical to the b protein. Both forms of tyrosinase were noncompetitively inhibited by Ca2+ at physiologically relevant concentrations. However, the b protein was apparently more susceptible, since maximal inhibition was reached at lower Ca2+ concentrations for LEMT. Moreover, binding of Ca2+ to the tyrosinases resulted in a noticeable thermal destabilization of the enzymes, which was also more pronounced for LEMT. 相似文献
140.
I. I. Pottosin P. R. Andjus D. Vučelić G. N. Berestovsky 《The Journal of membrane biology》1993,136(2):113-124
We studied the effects of H2O/D2O substitution on the permeation and gating of the large conductance Ca2+-activated K+ channels inChara gymnophylla droplet membrane using the patchclamp technique. The selectivity sequence of the channel was: K+>Rb+≫Li+, Na+, Cs+ and Cl−. The conductance of this channel in symmetric 100mm KCl was found to be 130 pS. The single channel conductance was decreased by 15% in D2O as compared to H2O. The blockade of channel conductance by cytosolic Ca2+ weakened in D2O as a result of a decrease in zero voltage Ca2+ binding affinity by a factor of 1.4. Voltage-dependent channel gating was affected by D2O primarily due to the change in Ca2+ binding to the channel during the activation step. The Hill coefficient for Ca2+ binding was 3 in D2O and around 1 in H2O. The values of the Ca2+ binding constant in the open channel conformation were 0.6 and 6 μm in H2O and D2O, respectively, while the binding in the closed conformation was much less affected by D2O. The H2O/D2O substitution did not produce a significant change in the slope of channel voltage dependence but caused a shift as large
as 60 mV with 1mm internal Ca2+. 相似文献