全文获取类型
收费全文 | 264篇 |
免费 | 21篇 |
出版年
2019年 | 3篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 7篇 |
2009年 | 3篇 |
2008年 | 10篇 |
2007年 | 11篇 |
2006年 | 7篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1991年 | 6篇 |
1987年 | 2篇 |
1980年 | 2篇 |
1971年 | 3篇 |
1928年 | 1篇 |
1927年 | 2篇 |
1926年 | 2篇 |
1925年 | 4篇 |
1924年 | 6篇 |
1923年 | 3篇 |
1922年 | 6篇 |
1921年 | 7篇 |
1920年 | 9篇 |
1919年 | 11篇 |
1918年 | 2篇 |
1917年 | 5篇 |
1916年 | 9篇 |
1915年 | 2篇 |
1914年 | 15篇 |
1913年 | 3篇 |
1912年 | 4篇 |
1911年 | 2篇 |
1910年 | 3篇 |
1908年 | 2篇 |
1907年 | 2篇 |
1905年 | 1篇 |
排序方式: 共有285条查询结果,搜索用时 78 毫秒
71.
Venema R Tjalsma H van Dijl JM de Jong A Leenhouts K Buist G Venema G 《The Journal of biological chemistry》2003,278(17):14739-14746
Lipid-modified proteins play important roles at the interface between eubacterial cells and their environment. The importance of lipoprotein processing by signal peptidase II (SPase II) is underscored by the fact that this enzyme is essential for viability of the Gram-negative eubacterium Escherichia coli. In contrast, SPase II is not essential for growth and viability of the Gram-positive eubacterium Bacillus subtilis. This could be due to alternative amino-terminal lipoprotein processing, which was shown previously to occur in SPase II mutants of B. subtilis. Alternatively, uncleaved lipoprotein precursors might be functional. To explore further the importance of lipoprotein processing in Gram-positive eubacteria, an SPase II mutant strain of Lactococcus lactis was constructed. Although some of the 39 (predicted) lactococcal lipoproteins, such as PrtM and OppA, are essential for growth in milk, the growth of SPase II mutant L. lactis cells in this medium was not affected. Furthermore, the activity of the strictly PrtM-dependent extracellular protease PrtP, which is required for casein degradation, was not impaired in the absence of SPase II. Importantly, no alternative processing of pre-PrtM and pre-OppA was observed in cells lacking SPase II. Taken together, these findings show for the first time that authentic lipoprotein precursors retain biological activity. 相似文献
72.
The brushtail possum (Trichosurus vulpecula) zona pellucida (ZP) is composed of three major glycoproteins, designated ZP1, ZP2, and ZP3 based on their size and homology with eutherian ZP proteins. These proteins are candidate antigens for the development of an immunocontraceptive vaccine to control the fertility of the brushtail possum in New Zealand, where it is an introduced pest. In order to further their immunological and functional characterization, recombinant possum ZP proteins were produced in Escherichia coli (E. coli) strain JM109, M15, SG13009, or BL21 codon plus. Each of the proteins produced possessed a N-terminal six histidine tag (His)(6) to facilitate purification and consisted of amino acid (aa) residues 18-471 of possum ZP1, aa residues 40-311 of ZP2 (ZP2-N), aa residues 305-634 of ZP2 (ZP2-C), and aa residues 23-342 of ZP3. Immunoblot using anti-RGS(His)(4) antibodies and polyclonal rabbit anti-porcine ZP antibodies detected major bands at 54 kDa for ZP1, 32 kDa for ZP2-N, 39 kDa for ZP2-C, and 40 kDa for ZP3. Immunization of male and female rabbits with ZP2-N, ZP2-C, and ZP3 purified on Ni-NTA resin under denaturing conditions generated antibodies reactive with recombinant ZP proteins on Western blot and with native ZP proteins in possum ovarian sections using immunofluorescence. Antibodies generated against ZP1 in the same way were reactive with recombinant ZP proteins on Western blot only. The recombinant possum ZP proteins and specific antibodies produced in this study give an indication of the antigenic relationship of the possum ZP proteins and are vital tools for future studies of sperm-ZP binding in marsupials and for the evaluation of ZP-based contraceptive vaccines in possums and other marsupials. 相似文献
73.
Kuipers OP de Jong A Baerends RJ van Hijum SA Zomer AL Karsens HA den Hengst CD Kramer NE Buist G Kok J 《Antonie van Leeuwenhoek》2002,82(1-4):113-122
74.
Darwin W Reed Christopher K Savile Xiao Qiu Peter H Buist Patrick S Covello 《European journal of biochemistry》2002,269(20):5024-5029
The mechanism by which the fatty acid (1,4)-desaturase of Calendula officinalis produces calendic acid from linoleic acid has been probed through the use of kinetic isotope effect (KIE) measurements. This was accomplished by incubating appropriate mixtures of linoleate and regiospecifically dideuterated isotopomers with a strain of Saccharomyces cerevisiae expressing a functional (1,4)-desaturase. GC-MS analysis of methyl calendate obtained in these experiments showed that the oxidation of linoleate occurs in two discrete steps since the cleavage of the C11-H bond is very sensitive to isotopic substitution (kH/kD = 5.7 +/- 1.0) while no isotope effect (kH/kD = 1.0 +/- 0.1) was observed for the C8-H bond breaking step. These data indicate that calendic acid is produced via initial H-atom abstraction at C11 of a linoleoyl substrate and supports the hypothesis that this transformation represents a regiochemical variation of the more common C12-initiated Delta12 desaturation process. 相似文献
75.
Acceptor specificity of the human leukocyte alpha3 fucosyltransferase: role of FucT-VII in the generation of selectin ligands 总被引:2,自引:2,他引:0
Britten CJ; van den Eijnden DH; McDowell W; Kelly VA; Witham SJ; Edbrooke MR; Bird MI; de Vries T; Smithers N 《Glycobiology》1998,8(4):321-327
The alpha3 fucosyltransferase, FucT-VII, is one of the key
glycosyltransferases involved in the biosynthesis of the sialyl Lewis X
(sLex) antigen on human leukocytes. The sialyl Lewis X antigen
(NeuAcalpha(2-3)Galbeta(1-4)[Fucalpha(1-3)]GlcNAc-R) is an essential
component of the recruitment of leukocytes to sites of inflammation,
mediating the primary interaction between circulating leukocytes and
activated endothelium. In order to characterize the enzymatic properties of
the leukocyte alpha3 fucosyltransferase FucT-VII, the enzyme has been
expressed in Trichoplusia ni insect cells. The enzyme is capable of
synthesizing both sLexand sialyl-dimeric-Lexstructures in vitro , from
3'-sialyl-lacNAc and VIM-2 structures, respectively, with only low levels
of fucose transfer observed to neutral or 3'-sulfated acceptors. Studies
using fucosylated NeuAcalpha(2-3)-(Galbeta(1- 4)GlcNAc)3-Me acceptors
demonstrate that FucT-VII is able to synthesize both di-fucosylated and
tri-fucosylated structures from mono- fucosylated precursors, but
preferentially fucosylates the distal GlcNAc within a polylactosamine
chain. Furthermore, the rate of fucosylation of the internal GlcNAc
residues is reduced once fucose has been added to the distal GlcNAc. These
results indicate that FucT-VII is capable of generating complex selectin
ligands, in vitro , however the order of fucose addition to the lactosamine
chain affects the rate of selectin ligand synthesis.
相似文献
76.
David A Baldwin Deolinda MR de Sousa 《Biochemical and biophysical research communications》1981,99(4):1101-1107
The kinetics of iron release from N-terminal and C-terminal monoferric human transferrins has been studied using EDTA as the accepting chelate. In the absence of added salts iron release from the N-terminal site is more facile but the relative lability can be reversed by the addition of NaClO4, NaCl and LiCl. The results indicate that both anions and cations can affect the lability of the two sites. Since the relative lability of the two monoferrictransferrins is affected by fairly moderate concentrations of NaCl and NaClO4 we suggest that the ionic composition serum may play an important role in determining the observed distribution of iron among the sites. A new method for the preparation of N-terminal monoferrictransferrin is described. 相似文献
77.
Bas Engel Kees van Reenen Willem Buist 《Biometrical journal. Biometrische Zeitschrift》2003,45(7):866-886
Data from an ACTH challenge experiment with veal calves, two short time series of cortisol measurements per animal at 6 and 27 weeks of age, are analysed. Interest is focussed on variation in cortisol profiles both within and between animals. Potential effects of an animals diet and housing system on the profiles are addressed as well. Fully parametric and semi‐parametric models, combining individual random effects with effects of diet and housing, were fitted using (approximate) restricted maximum likelihood (employing Laplacian integration). Eigenfunctions were utilized to describe the variation between profiles and the connection between profiles of the same individual. All calculations were performed with standard software. Results of the analysis provides empirical support for the existence of stable individual characteristics mediating reactivity of the adrenal cortex. 相似文献
78.
Buist A Blanchetot C Tertoolen LG den Hertog J 《The Journal of biological chemistry》2000,275(27):20754-20761
We have employed a substrate trapping strategy to identify physiological substrates of the receptor protein-tyrosine phosphatase alpha (RPTPalpha). Here we report that a substrate-trapping mutant of the RPTPalpha membrane proximal catalytic domain (D1), RPTPalpha-D1-C433S, specifically bound to tyrosine-phosphorylated proteins from pervanadate-treated cells. The membrane distal catalytic domain of RPTPalpha (D2) and mutants thereof did not bind to tyrosine-phosphorylated proteins. The pattern of tyrosine-phosphorylated proteins that bound to RPTPalpha-D1-C433S varied between cell lines, but a protein of approximately 130 kDa was pulled down from every cell line. This protein was identified as p130(cas). Tyrosine-phosphorylated p130(cas) from fibronectin-stimulated NIH3T3 cells bound to RPTPalpha-D1-C433S as well, suggesting that p130(cas) is a physiological substrate of RPTPalpha. RPTPalpha dephosphorylated p130(cas) in vitro, and RPTPalpha co-localized with a subpopulation of p130(cas) to the plasma membrane. Co-transfection experiments with activated SrcY529F, p130(cas), and RPTPalpha or inactive, mutant RPTPalpha indicated that RPTPalpha dephosphorylated p130(cas) in vivo. Tyrosine-phosphorylated epidermal growth factor receptor was not dephosphorylated by RPTPalpha under these conditions, suggesting that p130(cas) is a specific substrate of RPTPalpha in living cells. In conclusion, our results provide evidence that p130(cas) is a physiological substrate of RPTPalpha in vivo. 相似文献
79.
Sianos G Kay IP Carlier SG Lighart JM Wardeh AJ Coen VL Levendag PC Serruys PW 《International journal of cardiovascular interventions》2000,3(2):121-125
The application of beta-radiation in coronary arteries is a promising new technique for the treatment of in-stent restenosis. This is the first case in which the 5 F. delivery catheter of the Beta-Cath trade mark system was advanced through the struts of a stent, previously deployed in an adjacent branch, so as to deliver radiation to the target vessel. 相似文献
80.
The stereochemistry of fatty acid desaturase-mediated sulfoxidation can be evaluated at micromolar concentrations of analyte using (19)F NMR in combination with a chiral shift reagent: (S)-(+)-MPAA. 相似文献