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21.
Chaomurilege Zu Yanhui Miyagi Atsuko Hashida Shin-Nosuke Ishikawa Toshiki Yamaguchi Masatoshi Kawai-Yamada Maki 《Journal of plant research》2023,136(1):97-106
Journal of Plant Research - Chloroplast-localized NAD kinase (NADK2) is responsible for the production of NADP+, which is an electron acceptor in the linear electron flow of photosynthesis. The... 相似文献
22.
Phosphorescence and optically detected zero field magnetic resonance ( ODMR ) spectra are reported for a bromine atom-containing polynucleotide, poly(dA- br5dU ). The triplet state luminescence of poly(dA- br5dU ) is dominated by the phosphorescence of the bromouracil base which possesses sub-millisecond triplet lifetimes. Characteristic multiple slow passage ODMR transitions, which are observed in both br5dUrd and poly(dA- br5dU ), are assigned to the triplet state of bromouracil. In addition, an abnormally-perturbed adenine triplet state, which is not apparent in the phosphorescence spectrum of poly(dA- br5dU ), is detected and identified by its slow passage ODMR and amplitude-modulated phosphorescence microwave double resonance spectra. It is proposed that the perturbed adenine is a minor component of the polynucleotide structure which is present in regions of altered stacking induced by the high polarizability of the Br atom. 相似文献
23.
CH3Hg(II)OH forms complexes at pH 8 with tyrosine and with tyrosine ethyl ester (TEE) that are detected by ultraviolet difference absorption spectra. With Kf defined by CH3HgOH + HB CH3HgB + H2O, we find log Kf = 3.61 (tyrosine) and 3.36 (TEE). A heavy-atom effect is observed in frozen glasses of the complexes; this indicates a close interaction between Hg and the chromophore. No UV difference spectrum or heavy-atom effect is observed with N-acetyl tyrosine ethyl ester, indicating that complexing at the phenol O does not occur, and suggesting that binding occurs at the amine N. Zero field optically detected magnetic resonance (ODMR) measurements of the CH3Hg(II)-tyrosine triplet state give (D, E) = (0.129, 0.047) or (0.134, 0.041) cm?1 depending upon assignment of transitions. D of tyrosine is relatively unaffected, but E is reduced by CH3Hg(II) complexing. Low-temperature kinetic measurements show that the shortest lived sublevel of the complex is Tz, where z lies along the phenol long axis in tyrosine. A dominant 11.6-msec component in the 77 K decay of the phosphorescence is consistent with the individual sublevel lifetimes obtained by ODMR. 相似文献
24.
Mutational specificity of the dnaE173 mutator associated with a defect in the catalytic subunit of DNA polymerase III of Escherichia coli. 总被引:4,自引:0,他引:4
We developed a system to examine forward mutations that occurred in the rpsL gene of Escherichia coli placed on a multicopy plasmid. Using this system we determined the mutational specificity for a dnaE173 mutator strain in which the editing function of DNA polymerase III is impeded. The frequency of rpsL- mutations increased 32,000-fold, due to the dnaE173 mutator, and 87 independent rpsL- mutations in the mutator strain were analyzed by DNA sequencing, together with 100 mutants recovered from dnaE+ strain, as the control. While half the number of mutations that occurred in the wild-type strain were caused by insertion elements, no such mutations were recovered from the mutator strain. A novel class of mutation, named "sequence substitution" was present in mutants raised in the dnaE173 strain; seven sequence substitutions induced in the mutator strain occurred at six sites, and all were located in quasipalindromic sequences, carrying the GTG or CAC sequence at one or both endpoints. While other types of mutation were found in both strains, single-base frameshifts were the most frequent events in the mutator strain. Thus, the mutator effect on this class of mutation was 175,000-fold. A total of 95% of the single-base frameshifts in the mutator strain were additions, most of which occurred at runs of A or C bases so as to increase the number of identical residues. Base substitutions, the frequency of which was enhanced 25,000-fold by the mutator effect, occurred primarily at several hotspots in the mutator strain, whereas those induced in the wild-type strain were more randomly distributed throughout the rpsL sequence. The dnaE173 mutator also increased the frequency of duplications 28,000-fold. Of the three duplications recovered from the mutator strain, one was a simple duplication, the region of which was flanked by direct repeats. The other duplications were complex, one half part of which was in the inverted orientation of a region containing two sets of inverted repeats. The same duplications were also recovered from the wild-type strain. The present data suggest that dnaE173 is a novel class of mutator that sharply induces sequence-directed mutagenesis, yielding high frequencies of single base frameshifts, duplications with inversions, sequence substitutions and base substitutions at hotspots. 相似文献
25.
Phosphorescence and optically detected magnetic resonance (ODMR) have been used to characterize two synthetic peptides, alpha 181-198 and alpha 185-196, of the major binding determinant of the alpha-acetylcholine receptor (AChR) of Torpedo californica and its interaction with alpha-bungarotoxin (BgTX) using Trp as an intrinsic probe. BgTX conformational changes are suggested upon complexation with the peptides. Methylmercury-modified peptides show conformational heterogeneity which brings some of the modified Cys residues into proximity of peptide Trp(s). These modified peptides, when bound to BgTX, undergo structural changes which remove the tagged Cys from its close contact with the Trp residue(s) of the peptide. 相似文献
26.
Calphobindins (CPBs, placental annexins) are intracellular Ca(2+)- and phospholipid-dependent proteins like protein kinase C [EC 2.7.1.37]. We investigated the inhibitory effects of calphobindins on the protein kinase C activity in vitro. CPB I inhibited the protein kinase C activity for both histone phosphorylation and lipocortin phosphorylation, but CPB II and CPB III inhibited only the protein kinase C activity for histone phosphorylation. In the case of histone phosphorylation, all CPBs inhibited the protein kinase C activity in a concentration-dependent manner, and the IC50 (concentration required for 50% inhibition) value of CPB I was 70 nM. The inhibition of protein kinase C by CPB I was Ca(2+)-dependent, and did not disappear upon increasing the concentration of phosphatidyl-serine. Kinetic analysis by double-reciprocal plots indicated that CPB I interacted not only with phosphatidylserine but also with protein kinase C. Although CPB I partially interacts with phospholipid, it is conceivable that the inhibitory action of CPB I on protein kinase C results from direct interaction of CPB I with protein kinase C. Since CPBs are mainly present under the plasma membrane, it is presumed that CPB I is an endogenous inhibitor of protein kinase C, and according to intracellular circumstances, CPB II and CPB III may also be endogenous inhibitors. 相似文献
27.
The complexes of point-mutated Escherichia coli single-stranded DNA-binding protein (Eco SSB) with poly-(2-thiouridylic acid) (poly S2U) have been studied by optical detection of magnetic resonance spectroscopy (ODMR). Previous work has determined that two of four tryptophan (Trp) residues in Eco SSB undergo stacking interactions with nucleic acid bases. Selective photoexcitation of S2U bases was performed and subsequent triplet----triplet energy transfer from S2U to nearby Trp residues in the protein took place. The zero-field splitting (ZFS) parameters and sublevel kinetics were determined for each Trp residue sensitized by S2U. The sublevel lifetimes of the two sensitized residues are similar to those of normal Trp. The ZFS parameters, on the other hand, show a dramatic reduction relative to those of the uncomplexed protein, implying a more polarizable environment for the sensitized Trp residues and/or charge transfer interactions with the S2U bases. 相似文献
28.
H Yoshizaki T Mizoguchi K Arai M Shiratsuchi Y Shidara M Maki 《Journal of biochemistry》1990,107(1):43-50
The structure of human placental calphobindin-II (CPB-II) was investigated by amino acid composition and amino acid sequence analyses of peptides generated by protease digestion of the protein. The 45 peptides obtained from the lysyl endopeptidase digest of CPB-II, and the amino-terminal peptide prepared from its tryptic digest, were analyzed, and they accounted for over 98% of total amino acids of CPB-II. The structure of CPB-II determined by protein sequencing was identical to that previously predicted from its cDNA sequence (Iwasaki, A. et al. (1989) J. Biochem. 106, 43-49), except for the amino terminus. Since the amino terminus of CPB-II was blocked to Edman degradation, fast-atom-bombardment mass spectrometric analysis was used to demonstrate that the amino-terminal residue was acetyl-alanine. The carboxyl-terminal residue of CPB-II was identified as aspartic acid by the hydrazinolytic procedure. Calcium-binding studies indicated that 1 mol of CPB II binds 1 mol of calcium in the absence of phospholipid and 8 mol of calcium in the presence of phospholipid. 相似文献
29.
M. Akaboshi K. Kawai H. Maki K. Kawamoto Y. Honda 《Origins of life and evolution of the biosphere》1982,12(4):339-345
Ammonium acetate in various conditions was irradiated in a reactor to examine the contributions of both the reactor radiations and recoiled14C nucleis to form the biologically interesting molecules. Present investigations demonstrated that several amino acids, glycine, alanine, -alanine and GABA, and may-be aspartic acid, serine and valine by prolonged irradiation, were formed in the aqueous solutions of ammonium acetate.14C-radioactivities were also found distributed in these amino acids. However, no special relationship between14C-radioactivity and these amino acids formed was observed. 相似文献
30.