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991.
The C-terminal extension of the beta7 subunit and activator complexes stabilize nascent 20 S proteasomes and promote their maturation 总被引:2,自引:0,他引:2
Marques AJ Glanemann C Ramos PC Dohmen RJ 《The Journal of biological chemistry》2007,282(48):34869-34876
The eukaryotic 20 S proteasome is formed by dimerization of two precursor complexes containing the maturation factor Ump1. Beta7/Pre4 is the only one of the 14 subunits forming the 20 S proteasome that is absent from these precursor complexes in Saccharomyces cerevisiae. Increased expression of Pre4 leads to a reduction in the level of precursor complex, indicating that Pre4 incorporation into these complexes is rate-limiting for their dimerization. When we purified these precursor complexes, we observed co-purification of Blm10, a large protein known to attach to the alpha ring surface of proteasomes. In contrast to single mutants lacking either Blm10 or the C-terminal extension of Pre4, a mutant lacking both grew extremely poorly, accumulated very high levels of precursor complexes, and was impaired in beta subunit maturation. The effect of blm10Delta on proteasome biogenesis is modest, apparently because the 19 S regulatory particle is capable of substituting for Blm10, as long as precursor complex dimers are stabilized by the Pre4 C terminus. We found that a mutation (sen3/rpn2) affecting the Rpn2 subunit inhibits attachment of the 19 S activator to the 20 S particle or its precursors. Although the sen3 mutation alone had no apparent effect on precursor complex dimerization and active site maturation, the sen3 blm10 double mutant was impaired in these processes. Together these data demonstrate that Blm10 and the 19 S activator have a partially redundant function in stabilizing nascent 20 S proteasomes and in promoting their activation. 相似文献
992.
993.
Oliveira MG Brito JR Carvalho RR Guth BE Gomes TA Vieira MA Kato MA Ramos II Vaz TM Irino K 《Applied and environmental microbiology》2007,73(18):5945-5948
The presence of Shiga toxin-producing Escherichia coli (STEC) in water buffaloes is reported for the first time in South America. The prevalence of STEC ranged from 0 to 64% depending on the farm. STEC isolates exhibiting the genetic profiles stx(1)stx(2)ehxA iha saa and stx(2)ehxA iha saa predominated. Of the 20 distinct serotypes identified, more than 50% corresponded to serotypes associated with human diseases. 相似文献
994.
Schwab S Ramos HJ Souza EM Pedrosa FO Yates MG Chubatsu LS Rigo LU 《Archives of microbiology》2007,187(5):379-386
995.
C. San Vicente J. Castelló J. Corbera A. Jimeno T. Munilla M. C. Sanz J. C. Sorbe A. Ramos 《Polar Biology》2007,30(4):477-486
During the austral summer 1995, suprabenthic samplings were carried out at 24 stations (depth range 45–649 m) located around
Livingston Island, within the caldera of Deception Island and in the Bransfield Strait. At each station, the near-bottom motile
fauna was simultaneously collected with a multinet Macer-GIROQ sled in three water layers above the bottom. This study presents
original data on the occurrence, diversity, vertical distribution and abundance of suprabenthic taxa in this near-bottom environment.
The most speciose taxa were amphipods (at least 140 spp.), followed by isopods (66 spp.), pycnogonids (31 spp.) and mysids
(19 spp.). Total abundances ranged between 31 ind./100 m2 (Bransfield Strait, 361 m depth) and 6817 ind./100 m2 (South Livingston Island, 163 m depth). According to stations, the groups numerically dominant and more frequent were amphipods
(17 stations) or mysids (seven stations). Four suprabenthic assemblages were discriminated in the study area, apparently more
structured by the degree of shelter-exposure and development of sessile epifauna than by water depth or sediment features. 相似文献
996.
Benach J Swaminathan SS Tamayo R Handelman SK Folta-Stogniew E Ramos JE Forouhar F Neely H Seetharaman J Camilli A Hunt JF 《The EMBO journal》2007,26(24):5153-5166
The second messenger cyclic diguanylate (c-di-GMP) controls the transition between motile and sessile growth in eubacteria, but little is known about the proteins that sense its concentration. Bioinformatics analyses suggested that PilZ domains bind c-di-GMP and allosterically modulate effector pathways. We have determined a 1.9 A crystal structure of c-di-GMP bound to VCA0042/PlzD, a PilZ domain-containing protein from Vibrio cholerae. Either this protein or another specific PilZ domain-containing protein is required for V. cholerae to efficiently infect mice. VCA0042/PlzD comprises a C-terminal PilZ domain plus an N-terminal domain with a similar beta-barrel fold. C-di-GMP contacts seven of the nine strongly conserved residues in the PilZ domain, including three in a seven-residue long N-terminal loop that undergoes a conformational switch as it wraps around c-di-GMP. This switch brings the PilZ domain into close apposition with the N-terminal domain, forming a new allosteric interaction surface that spans these domains and the c-di-GMP at their interface. The very small size of the N-terminal conformational switch is likely to explain the facile evolutionary diversification of the PilZ domain. 相似文献
997.
Computational and biological inference of gene regulatory networks of the LINE-1 retrotransposon 总被引:1,自引:0,他引:1
Ramos KS He Q Kalbfleisch T Montoya-Durango DE Teneng I Stribinskis V Brun M 《Genomics》2007,90(2):176-185
Computational approaches were used to define structural and functional determinants of a putative genetic regulatory network of murine LINE-1 (long interspersed nuclear element-1), an active mammalian retrotransposon that uses RNA intermediates to populate new sites throughout the genome. Polymerase (RNA) II polypeptide E AI845735 and mouse DNA homologous to Drosophila per fragment M12039 were identified as primary attractors. siRNA knockdown of the aryl hydrocarbon receptor NM_013464 modulated gene expression within the network, including LINE-1, Sgpl1, Sdcbp, and Mgst1. Genes within the network did not exhibit physical proximity and instead were dispersed throughout the genome. The potential impact of individual members of the network on the global dynamical behavior of LINE-1 was examined from a theoretical and empirical framework. 相似文献
998.
In spite of the enormous interest that has been devoted to its study, the mechanism of the enzyme farnesyltransferase (FTase) remains the subject of several crucial doubts. In this article, we shed a new light in one of the most fundamental dilemmas that characterize the mechanism of this puzzling enzyme commonly referred to as the "distances paradox", which arises from the existence of a large 8-A distance between the two reactive atoms in the reaction catalyzed by this enzyme: a Zn-bound cysteine sulphur atom from a peptidic substrate and the farnesyldiphosphate (FPP) carbon 1. This distance must be overcome for the reaction to occur. In this study, the two possible alternatives were evaluated by combining molecular mechanics (AMBER) and quantum chemical calculations (B3LYP). Basically, our results have shown that an activation of the Zn-bound cysteine thiolate with subsequent displacement from the zinc coordination sphere towards the FPP carbon 1 is not a realistic hypothesis of overcoming the large distance reported in the crystallographic structures of the ternary complexes between the two reactive atoms, but that a rotation involving the FPP molecule can bring the two atoms closer with moderate energetic cost, coherent with previous experimental data. This conclusion opens the door to an understanding of the chemical step in the farnesylation reaction. 相似文献
999.
Effects of dietary flavonoids on apoptotic pathways related to cancer chemoprevention 总被引:1,自引:0,他引:1
Ramos S 《The Journal of nutritional biochemistry》2007,18(7):427-442
Epidemiological studies have described the beneficial effects of dietary polyphenols (flavonoids) on the reduction of the risk of chronic diseases, including cancer. Moreover, it has been shown that flavonoids, such as quercetin in apples, epigallocatechin-3-gallate in green tea and genistein in soya, induce apoptosis. This programmed cell death plays a critical role in physiological functions, but there is underlying dysregulation of apoptosis in numerous pathological situations such as Parkinson's disease, Alzheimer's disease and cancer. At the molecular level, flavonoids have been reported to modulate a number of key elements in cellular signal transduction pathways linked to the apoptotic process (caspases and bcl-2 genes), but that regulation and induction of apoptosis are unclear. The aim of this review is to provide insights into the molecular basis of the potential chemopreventive activities of representative flavonoids, with emphasis on their ability to control intracellular signaling cascades responsible for regulating apoptosis, a relevant target in cancer-preventive approach. 相似文献
1000.
Humberto J. O. Ramos Emanuel M. Souza Juliana R. L. Soares-Ramos Fábio O. Pedrosa 《World journal of microbiology & biotechnology》2007,23(5):713-717
A new broad-host-range vector expressing constitutively the reporter genes gfp and gusA was used to evaluate nodule occupancy of Phaseolus vulgaris nodules by Rhizobium tropici. The results showed that the pHRGFPGUS plasmid was stably maintained in R. tropici over 45 generations and can therefore be used in nodule competitiveness assays. A new method for determining the nodule occupancy
using the green fluorescent protein as a marker is described and is shown to be quick, inexpensive and reliable. 相似文献