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The fouling tendencies of seven commercial antifoam agents used with microfiltration membranes were investigated in a stirred cell. Parameters such as viscosity, oil droplet size distribution, contact angle, work of adhesion (W(a)), membrane type, operating pressure, and feed concentration were examined. The results show that a silicone-based antifoam, G832, gave a significantly lower flux (=100 L h(-1) m(-2)) than the polypropylene glycol antifoam PPG2000 (1500-2500 L h(-1) m(-2)) over the concentrations from 0.5 to 4.0 mL L(-1) at 50 kPa, 700 rpm, and 25 degrees C. The significantly lower flux attained by the antifoam G832 was attributed to a number of factors, such as its greater viscosity (1.25 x 10(-3) kg m(-1) s(-1) compared with 1.05 x 10(-3) kg m(-1) s(-1) for PPG2000), a smaller average oil droplet size (0.28 vs. 0.65 mum) comparable to the membrane pore size distribution (0.26-0.62 mum), a higher contact angle (98 vs. 51 degrees ); and a significantly larger value of work of adhesion (26.0 vs. 0.81 mN m(-1)). The different magnitudes of membrane adsorption by these antifoam agents, as reflected by their values of work of adhesion, were also observed in the field emission scanning electronic microscopy photographs. In terms of membrane type, the inorganic Anopore alumina membrane was found to offer a higher PPG flux than the organic Millipore polyvinyl difluoride (PVDF) membranes (both hydrophilic and hydrophobic). Furthermore, the mixed-type antifoams (B5600, B426, and G832) were found to give an increased hydraulic resistance and fouling percentage with an increase in pressure or feed concentration. Conversely for PPG2000, a reduction of the hydraulic resistance and fouling percentage was observed with increases of these two parameters. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 89-98, 1997. 相似文献
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The ability of different classes of passively administered guinea pig antibody (γ1, γ2, and IgM) to regulate humoral and cell-mediated immunity to flagellin, polymerized flagellin (POL), and sheep red blood cells (SRBC) was investigated in rats. It was found that at high concentrations, all classes of antibody suppressed the primary antibody responses and usually enhanced the delayed-type hypersensitivity induced by the three antigens. With flagellin and SRBC, the different classes of passive antibody varied in their suppressing and enhancing properties, being in the order: γ2 > γ1 = IgM. At low concentrations, γ1 and IgM enhanced the primary antibody response and suppressed the delayed hypersensitivity induced by flagellin. Such an effect was not observed with either POL or SRBC. Priming for a secondary antibody response was less readily suppressed by all classes of passive antibody. The removal of macrophage cytophilic antibody from γ2 converted this antibody to a preparation (γ2 absorbed) which had effects on humoral and cell-mediated immunity approaching that of γ1 antibody. 相似文献
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Heng Tai Liew Janet To Xiaohong Zhang Xinya Hemu Ning-Yu Chan Aida Serra Siu Kwan Sze Chuan-fa Liu James P. Tam 《The Journal of biological chemistry》2021,297(6)
Legumains, also known as asparaginyl endopeptidases (AEPs), cleave peptide bonds after Asn/Asp (Asx) residues. In plants, certain legumains also have ligase activity that catalyzes biosynthesis of Asx-containing cyclic peptides. An example is the biosynthesis of MCoTI-I/II, a squash family-derived cyclic trypsin inhibitor, which involves splicing to remove the N-terminal prodomain and then N-to-C-terminal cyclization of the mature domain. To identify plant legumains responsible for the maturation of these cyclic peptides, we have isolated and characterized a legumain involved in splicing, McPAL1, from Momordica cochinchinensis (Cucurbitaceae) seeds. Functional studies show that recombinantly expressed McPAL1 displays a pH-dependent, trimodal enzymatic profile. At pH 4 to 6, McPAL1 selectively catalyzed Asp-ligation and Asn-cleavage, but at pH 6.5 to 8, Asn-ligation predominated. With peptide substrates containing N-terminal Asn and C-terminal Asp, such as is found in precursors of MCoTI-I/II, McPAL1 mediates proteolysis at the Asn site and then ligation at the Asp site at pH 5 to 6. Also, McPAL1 is an unusually stable legumain that is tolerant of heat and high pH. Together, our results support that McPAL1 is a splicing legumain at acidic pH that can mediate biosynthesis of MCoTI-I/II. We purport that the high thermal and pH stability of McPAL1 could have applications for protein engineering. 相似文献
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Chiara Merigliano Romina Burla Mattia La Torre Simona Del Giudice Hsiangling Teo Chong Wai Liew Alexandre Chojnowski Wah Ing Goh Yolanda Olmos Klizia Maccaroni Maria Giubettini Irene Chiolo Jeremy G. Carlton Domenico Raimondo Fiammetta Vernì Colin L. Stewart Daniela Rhodes Graham D. Wright Brian E. Burke Isabella Saggio 《PLoS genetics》2021,17(8)
To complete mitosis, the bridge that links the two daughter cells needs to be cleaved. This step is carried out by the endosomal sorting complex required for transport (ESCRT) machinery. AKTIP, a protein discovered to be associated with telomeres and the nuclear membrane in interphase cells, shares sequence similarities with the ESCRT I component TSG101. Here we present evidence that during mitosis AKTIP is part of the ESCRT machinery at the midbody. AKTIP interacts with the ESCRT I subunit VPS28 and forms a circular supra-structure at the midbody, in close proximity with TSG101 and VPS28 and adjacent to the members of the ESCRT III module CHMP2A, CHMP4B and IST1. Mechanistically, the recruitment of AKTIP is dependent on MKLP1 and independent of CEP55. AKTIP and TSG101 are needed together for the recruitment of the ESCRT III subunit CHMP4B and in parallel for the recruitment of IST1. Alone, the reduction of AKTIP impinges on IST1 and causes multinucleation. Our data altogether reveal that AKTIP is a component of the ESCRT I module and functions in the recruitment of ESCRT III components required for abscission. 相似文献
80.
Andrew T Maniatis N Carbonaro F Liew SH Lau W Spector TD Hammond CJ 《PLoS genetics》2008,4(10):e1000220
Refractive error is a highly heritable quantitative trait responsible for considerable morbidity. Following an initial genome-wide linkage study using microsatellite markers, we confirmed evidence for linkage to chromosome 3q26 and then conducted fine-scale association mapping using high-resolution linkage disequilibrium unit (LDU) maps. We used a preliminary discovery marker set across the 30-Mb region with an average SNP density of 1 SNP/15 kb (Map 1). Map 1 was divided into 51 LDU windows and additional SNPs were genotyped for six regions (Map 2) that showed preliminary evidence of multi-marker association using composite likelihood. A total of 575 cases and controls selected from the tails of the trait distribution were genotyped for the discovery sample. Malecot model estimates indicate three loci with putative common functional variants centred on MFN1 (180,566 kb; 95% confidence interval 180,505–180, 655 kb), approximately 156 kb upstream from alternate-splicing SOX2OT (182,595 kb; 95% CI 182,533–182,688 kb) and PSARL (184,386 kb; 95% CI 184,356–184,411 kb), with the loci showing modest to strong evidence of association for the Map 2 discovery samples (p<10−7, p<10−10, and p=0.01, respectively). Using an unselected independent sample of 1,430 individuals, results replicated for the MFN1 (p=0.006), SOX2OT (p=0.0002), and PSARL (p=0.0005) gene regions. MFN1 and PSARL both interact with OPA1 to regulate mitochondrial fusion and the inhibition of mitochondrial-led apoptosis, respectively. That two mitochondrial regulatory processes in the retina are implicated in the aetiology of myopia is surprising and is likely to provide novel insight into the molecular genetic basis of common myopia. 相似文献