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131.
Although the importance of the extracellular signal-regulated kinase (ERK) pathway in regulating the transition from G1 to S has been extensively studied, its role during the G2/M transition is less well understood. Previous reports have shown that inhibition of the ERK pathway in mammalian cells delays entry as well as progression through mitosis, suggesting the existence of molecular targets of this pathway in M phase. In this report we employed 2-DE and MS to survey proteins and PTMs in the presence versus absence of MKK1/2 inhibitor. Targets of the ERK pathway in G2/M were identified as elongation factor 2 (EF2) and nuclear matrix protein, 55 kDa (Nmt55). Phosphorylation of each protein increased under conditions of ERK pathway inhibition, suggesting indirect control of these targets; regulation of EF2 was ascribed to phosphorylation and inactivation of upstream EF2 kinase, whereas regulation of Nmt55 was ascribed to a delay in normal mitotic phosphorylation and dephosphorylation. 2-DE Western blots probed using anti-phospho-Thr-Pro antibody demonstrated that the effect of ERK inhibition is not to delay the onset of phosphorylation controlled by cdc2 and other mitotic kinases, but rather to regulate a small subset of targets in M phase in a nonoverlapping manner with cdc2. 相似文献
132.
Charge distribution in 7-methylguanine regarding cation-pi interaction with protein factor eIF4E
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Ruszczynska K Kamienska-Trela K Wojcik J Stepinski J Darzynkiewicz E Stolarski R 《Biophysical journal》2003,85(3):1450-1456
Electric charge distribution in mRNA 5' cap terminus has been exhaustively characterized in respect to the affinity for cap-binding proteins. Formation of the stacked configuration of positively charged 7-methylguanine in between two aromatic amino acid rings, known as sandwich cation-pi stacking, is thought to be prerequisite for the specific recognition of the cap by eukaryotic initiation factor eIF4E; i.e., discrimination between the cap and nucleotides without the methyl group at N(7). Nuclear magnetic resonance spectroscopy of (15)N/(13)C-double-labeled 7-methylguanosine 5'-triphosphate and 7-methylguanosine, as well as their unsubstituted counterparts, GTP and guanosine, yielded characteristic changes of the electron-mediated spin-spin couplings and chemical shifts due to the methylation at N(7). The experimentally measured changes of the nuclear magnetic resonance parameters have been analyzed in respect to the electric charge distribution calculated by means of quantum chemical methods, and interpreted in terms of new proposed positive charge localization in the 7-methylguanine five-member ring. 相似文献
133.
134.
Foreign gene products can be enhanced by introduction into low storage protein mutants 总被引:3,自引:0,他引:3
Transgenic rice expressing soybean glycinin in its endosperm was crossed with two types of low-glutelin mutants to determine how much storage the protein mutants can contribute to increases in glycinin accumulation. The glycinin level (102 microg/100 mg seed) in the parental transgenic line was enhanced to approximately 224-237 microg/100 mg seed within a genetic background deficient in glutelin (i.e. of low glutelins). The enrichment of this foreign gene product was compensated by a decrease in the expression of other endogenous prolamine and globulin storage proteins, resulting in an almost equivalent total amount of seed storage proteins. These results show that low storage protein mutants can provide potentially useful hosts for the expression of foreign genes, allowing a higher-level accumulation, because they can provide wider space for the accumulation of foreign gene products than in the normal host plant. 相似文献
135.
The structure and function of the 33 kDa extrinsic protein of Photosystem II: A critical assessment 总被引:2,自引:0,他引:2
In this review the structure and function of the 33 kDa protein of Photosystem II is examined. Significant controversies exist concerning the solution secondary structure of the protein, the location of its binding site(s) within Photosystem II, the amino acid residues of the 33 kDa protein required for binding and its stoichiometry within the photosystem. The studies which examine these topics are considered from a critical perspective. A hypothetical model of the folding of the 33 kDa extrinsic protein which is supported by site-specific labeling studies and site-directed mutagenesis experiments is presented. Additionally, the function of the protein within the photosystem is unclear. We present a hypothesis that the 33 kDa protein is involved in maintaining the chloride associated with photosynthetic oxygen evolution in close proximity to the oxygen-evolving site. 相似文献
136.
Maria T. Giardi 《Planta》1993,190(1):107-113
The presence of heterogeneity in phosphorylated PSII core populations in grana membranes of spinach (Spinacia oleracea L.) was previously demonstrated (Giardi et al., 1991, Biochem. Biophys. Res. Commun. 176, 1298–1304). The effect of photoinhibitory conditions on the distribution of these phosphorylated PSII core populations in thylakoids and PSII particles has been investigated. The sensitivity of the PSII core to strong illumination depended on the phosphorylation state of D1 and D2 proteins as well as on the content of the 9-kDa PsbH phosphoprotein. When D1 and D2 proteins are under-phosphorylated, the 9-kDa phosphoprotein is tightly bound to the PSII core; thus, a partial protection from photoinhibition is observed. Of the different PSII core populations isolated from membranes photoinhibited for 10 min, the highly phosphorylated populations lack internal antennae CP43 and CP47; perhaps these migrate out to the non-appressed regions of thylakoids. The degradation of the D1 protein seems to follow the disassembly of the PSII core. 相似文献
137.
In this study we have analysed the multigene family coding for the cytoplasmic heat shock 70 kDa proteins (hsp70) inZea mays. Fully degenerate primers were used in a polymerase chain reaction (PCR) to amplify selected regions of the hsp70 genes. Sequence and Southern blot analysis reveals that at least three highly conserved genes exist in maize. In addition, amplification reveals the presence of a conserved intron in all genes examined. Expression analysis shows that the hsp70 genes studied represent members of the inducible and constitutive families. The results obtained may indicate that there are subfamilies of cytoplasmic hsp70 genes expressed in higher plants. 相似文献
138.
139.
In vivo protein synthesis in duck erythroblasts was compared to in vitro translation of polyribosomal and free cytoplasmic mRNA. The in vivo study showed the absence of de novo synthesis of the Mr 73 000 poly(A)-binding protein found associated with all polyribosomal mRNA. In vitro translation demonstrated that the mRNA for this protein is absent from the polyribosomal mRNA fraction but constitutes a medium frequency messenger among the repressed free mRNA. This result confirms the existence of a qualitative translational control in terminal differentiating duck erythroblasts leading eventually to the arrest of the protein synthesizing machinery. 相似文献
140.
Linda A. Franklin Guy Levavasseur C.Barry Osmond William J. Henley Joseph Ramus 《Planta》1992,186(3):399-408
Short-term (up to 5 h) transfers of shade-adapted (100 mol · m–2 · s–1) clonal tissue of the marine macroalga Ulva rotundata Blid. (Chlorophyta) to higher irradiances (1700, 850, and 350 mol · m–2 · s–1) led to photoinhibition of room-temperature chlorophyll fluorescence and O2 evolution. The ratio of variable to maximum (Fv/Fm) and variable (Fv) fluorescence, and quantum yield () declined with increasing irradiance and duration of exposure. This decline could be resolved into two components, consistent with the separation of photoinhibition into energy-dissipative processes (photoprotection) and damage to photosystem II (PSII) by excess excitation. The first component, a rapid decrease in Fv/Fm and in Fv, corresponds to an increase in initial (Fo) fluorescence and is highly sensitive to 1 mM chloramphenicol. This component is rapidly reversible under dim (40 mol · m–2 · s–1) light, but is less reversible with increasing duration of exposure, and may reflect damage to PSII. The second (after 1 h exposure) component, a slower decline in Fv/Fm and Fv with declining Fo, appears to be associated with the photoprotective interconversion of violaxanthin to zeaxanthin and is sensitive to dithiothreitol. The accumulation of zeaxanthin in U. rotundata is very slow, and may account for the predominance of increases in Fo at high irradiances.Abbreviations and Symbols CAP
chloramphenicol
- DTT
dithiothreitol
- Fo, Fm, Fv
initial, maximum, and variable fluorescence
-
quantum yield
- PFD
photon flux density
- PSII
photosystem II
To whom correspondence should be addressedWe are grateful to O. Björkman and S. Thayer, Carnegie Institution of Washington, Stanford, Cal., USA, for analysis of xanthophyll pigments reported here. This research was supported by National Science Foundation grant OCE-8812157 to C.B.O. and J.R. Support for G.L. was provided by a NSF-CNRS (Centre National de la Recherche Scientifique) exchange fellowship. 相似文献