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51.
María Florencia Pignataro María Georgina Herrera Natalia Brenda Fernández Martín Aran Hernán Gustavo Gentili Fernando Battaglini Javier Santos 《Biotechnology and bioengineering》2023,120(2):409-425
Frataxin is a kinetic activator of the mitochondrial supercomplex for iron-sulfur cluster assembly. Low frataxin expression or a decrease in its functionality results in Friedreich's Ataxia (FRDA). With the aim of creating new molecular tools to study this metabolic pathway, and ultimately, to explore new therapeutic strategies, we have investigated the possibility of obtaining small proteins exhibiting a high affinity for frataxin. In this study, we applied the ribosome display approach, using human frataxin as the target. We focused on Affi_224, one of the proteins that we were able to select after five rounds of selection. We have studied the interaction between both proteins and discussed some applications of this specific molecular tutor, concerning the modulation of the supercomplex activity. Affi_224 and frataxin showed a KD value in the nanomolar range, as judged by surface plasmon resonance analysis. Most likely, it binds to the frataxin acidic ridge, as suggested by the analysis of chemical shift perturbations (nuclear magnetic resonance) and computational simulations. Affi_224 was able to increase Cys NFS1 desulfurase activation exerted by the FRDA frataxin variant G130V. Importantly, Affi_224 interacts with frataxin in a human cellular model. Our results suggest quaternary addition may be a new tool to modulate frataxin function in vivo. Nevertheless, more functional experiments under physiological conditions should be carried out to evaluate Affi_224 effectiveness in FRDA cell models. 相似文献
52.
Summary Immobilized -chymotrypsin was used as catalyst to synthesize a kyotorphin derivative (Bz-Tyr-Arg-OEt) in the presence of five water-miscible aprotic solvents (dimethylsulphoxide, dimethylformamide, acetonitrile, acetone and tetrahydrofurane) at 30 °C. By using a kinetically-controlled approach, the maximum synthetic activity was obtained when Arg-OEt was used as nucleophile donor at a concentration 1.5-times higher than the acyl-acceptor substrate (Bz-Tyr-OEt). The water-miscible aprotic solvents enhanced greatly the synthetic activity proportionally to their hidrophilicity properties adequately measured by the log P parameter. At the optimum solvent concentration for the enzymatic peptide synthesis, both the water activity (Aw) of the media and the water content of the immobilized derivative showed a saturation profile against the log P parameter. As a function of the solvent hydrophilicity, these water parameters were shown as key parameters for the increase in the synthetic activity of the enzyme by the presence of these solvents. 相似文献
53.
54.
Lumen to bath J
12/C
1
and bath to lumen J
21/ C
2
fluxes per unit concentration of 19 probes with diameters (d
m) ranging from 3.0–30.0 Å (water, urea, erythritol, mannitol, sucrose, raffinose and 13 dextrans with d
m
9.1–30.0 Å) were measured during volume secretion (J
v
) in the upper segment of the Malpighian Tubule of Rhodnius by perfusing lumen and bath with 14C or 3H-labeled probes. J
net=(J
12/C
1 – J
21/C
2) was studied as a function of J
v
· J
v
was varied by using different concentrations of 5-hydroxy tryptamine. J
net for 3H-water was not different from J
v
We found: (i) A strong correlation between J
net
and J
v
for 8 probes d
m
=3.0–11.8 Å (group a probes), indicating that the convective component of J
net is more important than its diffusive component and than unstirred layers effects which are negligible. Therefore group a probes are solvent dragged as they cross the epithelium, (ii) There is no correlation between J
net and J
v
for 11 probes with d
m=11.8–30 Å (group b). Therefore these probes must cross the epithelium by diffusion and not by solvent drag, (iii) In a plot of J
net/J
v
vs. d
m
group a probes show a steep linear relation with a slope = –0.111, while for group b probes the slope is –0.002. Thus there is a break between groups a and b in this plot. We tried to fit the data with models for restricted diffusion and convention through cylindrical or parallel slit pathways. We conclude that (i) group a probes are dragged by water through an 11.0 Å-wide slit, (ii) Most of J
v
must follow an extracellular noncytosolic pathway, (iii) Group b probes must diffuse through a 42 Å-wide slit, (iv) A cylindrical pathway does not fit the data.E.G. is a Visiting Scientist at IVIC. It is a pleasure to thank Drs. A.E. Hill and Bruria Shachar-Hill for their suggestion of the use of dextrans, their instruction and help with the dextran separation technique, and their extensive discussions. Dr. R. Apitz, Mr H. Rojas and Mrs. Fulvia Bartoli were most helpful with suggestions during the course of the experimental work. Mr. Jose Mora was fundamental help with the equipment. Mrs. Lelis Ochoa and Mr. Luis F. Alvarez helped with some of the drawings. This work was partially supported by CONICIT, Fundación Polar and CDCH of UCV. It is a pleasure to thank Dr. H. Passow and Dr. K.J. Ullrich at the Max Planck Institut für Biophysik (Frankfurt/Main) where this work was initiated. 相似文献
55.
Flux and retention of 0.1%w/w aqueous solutions of several proteins [lysozyme, pepsin, bovine serum albumin (BSA), lipase, and gamma-globulin] with molecular weights of 14.6, 36, 67, 801 and 150 kDa are studied when they are tangentially filtered, with transmembrane pressure differences until 1 MPa and circulation velocities in the re-tentate loop from 0.04 to 1.98 m/s (laminar regime), through two asymmetric polysulfone commercial membranes (E-100 with a nominal pore size of 0.01 mum and E-500 with a nominal pore size of 0.04 mum). Results are analyzed with the film theory for the concentration-polarization phenomenon, obtaining the mass transfer coefficient along with the apparent and true retention coefficients for the cell used, as a function of the feed circulation velocity and the molecular weight of the solute. The standard retention curves lead to pore size distributions differing from the nominal ones. These differences can be attributed to the modifications of the membranes when they are in operational conditions, probably due to protein adsorption. (c) 1995 John Wiley & Sons, Inc. 相似文献
56.
A. Falconi M. Borde A. Hernández-Cruz F. R. Morales 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,176(5):679-689
Stimulation of the spinal cord of the electric fish Gymnotus carapo, evoked an abrupt increase in the discharge rate of the electric organ. At the maximum of this response, the rate increased an average of 26 ± 11.8%. The duration of the response was 4.9 ± 2.12 s; its latency was 10.4 ± 1.1 ms. Activation of the Mauthner axon played a decisive role in this phenomenon as indicated by the following: (1) recordings from the axon cap of the Mauthner cell demonstrated that the response was evoked if the Mauthner axon was antidromically activated and (2) a response that was similar to that produced by spinal cord stimulation, was elicited by intracellular stimulation of either Mauthner cell. Stimulation of the eighth nerve could also increase the discharge rate of the electric organ. The effect was greater if a Mauthner cell action potential was elicited. The findings described in the present report, indicate the existence of a functional connection between the Mauthner cell and the electromotor system in Gymnotus carapo. This connection may function to enhance the electrolocative sampling of the environment during Mauthner-cell mediated behaviors. This is a novel function for the Mauthner cell.Abbreviations
EHP
extrinsic hyperpolarizing potential
-
EOD
electric organ discharge
-
M-AIR
Mauthner initiated abrupt increase in rate
-
M-cell
Mauthner cell
-
M-axon
Mauthner axon
-
PM
pacemaker nucleus
-
PM-cell
pacemaker cell
-
PPn
prepacemaker nucleus
-
SPPn
sublemniscal prepacemaker nucleus 相似文献
57.
Carlos F. de Mello Diego D. De La Vega Leandro T. Pizutti Fabiane P. Lopes Maribel A. Rubin Jaime G. Homerich Dr. Carlos R. Melo Joana E. Somer Diogo O. Souza Moacir Wajner 《Neurochemical research》1995,20(12):1437-1441
The effect ofl-pyroglutamic acid, a metabolite that accumulates in pyroglutamic aciduria, on different neurochemical parameters was investigated in adult male Wistar rats. Glutamate binding, adenylate cyclase activity and G protein coupling to adenylate cyclase were assayed in the presence of the acid.l-pyroglutamic acid decreased Na+-dependent and Na+-independent glutamate binding Basal and GMP-PNP stimulated adenylate cyclase activity were not affected by the acid. Furthermore, rats received unilateral intrastriatal injections of 10–300 nmol of bufferedl-pyroglutamic acid. Vehicle (0.25 M Tris-Cl, pH 7.35–7.4) was injected into the contralateral striatum. Neurotoxic damage was assessed seven days after the injection by histological examination and by weighing both cerebral hemispheres. No difference in histology or weight could be identified between hemispheres. These results suggest that, although capable of interfering with glutamate binding, pyroglutamate did not cause a major lesion in the present model of neurotoxicity. 相似文献
58.
59.
L Moreno-Fierros E O Hernández Z O Salgado A Mújica 《Molecular reproduction and development》1992,33(2):172-181
The presence of actin has been determined in mammalian spermatozoa. However, its function in these cells is still almost unknown. Only in boar spermatozoa has evidence for F-actin and a possible function for it been presented. In this work, actin distribution and F-actin were determined in uncapacitated, capacitated, and acrosomal-reacted guinea pig spermatozoa, by means of monoclonal and polyclonal antibodies, using an indirect immunoperoxidase technique, and by the use of rhodamine-phalloidin. With the last probe we found filamentous actin in these cells. By both techniques, actin was detected in the acrosome and in the entire tail. In some cells with acrosomal reaction, actin was also detected in the equatorial and in the postacrosomal regions. SDS-PAGE and Western blots immunostained with monoclonal and polyclonal anti-actin antibodies confirmed the presence of actin in extracts of guinea pig spermatozoa. Actin was also detected in preparations of Percoll-purified spermatozoa. We have communicated that guinea pig spermatozoa show a change on calmodulin location during the acrosome reaction. They present it first in the equatorial region and later in the postacrosomal region. To determine if F-actin participates in this calmodulin translocation, we studied the effect of cytochalasin D. It was found that the number of cells with calmodulin in the equatorial region increased in the presence of cytochalasin D while the number of cells with calmodulin in the postacrosomal region decreased. We also found that after cytochalasin D treatment acrosome loss was increased and sperm motility was slightly inhibited. Our results suggest that actin participate in calmodulin translocation to the postacrosomal region during acrosome reaction, in maintaining the acrosome structure, and perhaps also in sperm motility. 相似文献
60.
M Zentella de Pi?a A Hernández-Tobías Y Salda?a-Balmori A Díaz-Belmont E Pi?a 《FEBS letters》1992,298(2-3):123-125
The non-steroidal anti-inflammatory drug, piroxicam, prevents the hepatic increase of triacylglycerols and malondialdehyde resulting from the acute intoxication of rats with ethanol. In addition, in the intoxicated rats, piroxicam consistently produces a decrease in the levels of blood ethanol in comparison with control animals. It is suggested that the anti-inflammatory compound stimulates ethanol oxidation. 相似文献