全文获取类型
收费全文 | 607篇 |
免费 | 72篇 |
国内免费 | 1篇 |
出版年
2022年 | 4篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 27篇 |
2014年 | 27篇 |
2013年 | 23篇 |
2012年 | 44篇 |
2011年 | 31篇 |
2010年 | 13篇 |
2009年 | 20篇 |
2008年 | 32篇 |
2007年 | 20篇 |
2006年 | 13篇 |
2005年 | 26篇 |
2004年 | 16篇 |
2003年 | 22篇 |
2002年 | 26篇 |
2001年 | 28篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1974年 | 11篇 |
1973年 | 7篇 |
1972年 | 7篇 |
1971年 | 3篇 |
排序方式: 共有680条查询结果,搜索用时 15 毫秒
131.
Bengt C. Magnusson 《Histochemistry and cell biology》1974,42(3):211-219
Summary The hydrolysis of ATP, AMP and glycerophosphate (GP) at alkaline pH in mineralizing bone and teeth of young mice has been studied histochemically. The substrates were visibly hydrolyzed to the same degree in osteoblasts, cells of stratum intermedium, odontoblasts and subodontoblasts at Ca2+ concentrations ranging from 10 mM to 600 mM. In the ameloblasts, however, only ATP was hydrolyzed. The ATPase activities gradually decreased at increasing Mg2+/Ca2+ ratios. The AMPase and GPase activities, on the other hand, were visibly unaffected. Marked cellular staining, including the nuclei was seen with AMP and GP as substrates when only Mg2+ ions were added. No ATPase activity at all could be recorded in media containing Mg2+ but no Ca2+ ions. The different phosphatase activities in cells involved in hard tissue formation were identically affected by preincubations with solutions containing various concentrations of Ca2+ or Mg2+ ions. The ATPase activity in striated muscle fibres and blood vessel walls, however, was affected differently by the same procedure.The results indicate that the phosphatase activities recorded in osteoblasts, cells of stratum intermedium, odontoblasts and subodontoblasts at alkaline pH belong to one single enzyme. The results also imply that CaATP is the preferred substrate in the enzymatic hydrolysis of ATP in hard-tissue-forming cells. 相似文献
132.
Synthesis of polyoma DNA by isolated nuclei 总被引:7,自引:0,他引:7
133.
S Mårtensson T Brodin A-S Carlström J Dahmen T Frejd A Gunnarsson U Jansson G Magnusson A Lundblad 《Glycoconjugate journal》1986,3(2):163-174
A mouse monoclonal antibody (87.5) against Gal1-4Gal has been obtained after immunization with the disaccharide glycosidically coupled to a protein. The specificity was determined by studying its binding to a number of glycoconjugates and oligosaccharides.The antibody which was found to be highly specific for terminal Gal1-4Gal residues is a powerful tool for the detection of this structure in glycoproteins and glycolipids by immunochemicalin vitro methods. It is also useful forin vitro quantification of the free disaccharide.A thin layer chromatographic overlay assay using glycolipids and an immunoperoxidase technique is also described. The antibody 87.5 is used in this assay to identify human uroepithelium glycolipids with terminal Gal1-4Gal residues.Abbreviations Lactosylceramide
Gal1-4GlcCer
- globotriaosylceramide
GbOse3-ceramide, Gal1-4Gal1-4GlcCer
- globotetraosylceramide
globoside, GbOse4-ceramide, GalNAc1-3Gal1-4Gal1-4GlcCer 相似文献
134.
Purification and complete primary structures of the heparin-, cell-, and DNA-binding domains of bovine plasma fibronectin 总被引:6,自引:0,他引:6
K Skorstengaard M S Jensen T E Petersen S Magnusson 《European journal of biochemistry》1986,154(1):15-29
The complete amino acid sequences of the heparin-, cell- and DNA-binding domains of bovine plasma fibronectin have been determined. The fragments were generated from the 170-kDa central plasmic fragment by extensive digestion with chymotrypsin, and they contain 268, 300 and 269 amino acid residues, respectively. No half-cystines or cysteines were found in these sequences. A glucosamine-based oligosaccharide group is attached to Asn-108 in the sequence of the DNA-binding domain. Only one of the three types of internal homology found in fibronectin [Petersen et al. (1983) Proc. Natl Acad. Sci. USA 80, 137-141], namely the type III homology, occurs in these three fragments, and each of them consists of approximately three stretches of this type III homology. Part of the arrangement of peptides was derived by comparison with the partial cDNA sequence for human fibronectin recently reported [Kornblihtt et al. (1984) Nucleic Acids Res. 12, 5853-5868]. 相似文献
135.
Abstract The effect of bacterial enterotoxins on rat intestinal permeability properties was studied by comparing the effect of toxin-positive and toxin-negative Escherichia coli and Salmonella typhimurium inoculated into a segment of rat small intestine. Fluoresceinated dextran 3000 (FITC-D3; M r 3000) was applied as permeability marker. The E. coli strain C922a-1 producing heat-labile (LT) and heat-stable (ST) enterotoxins and colonising factor CFA/II increased the transmural passage of the dextran probe into portal blood. In contrast, its plasmid-negative variant, a non-toxin producer lacking CFA, caused permeability changes indistinguishable from the bacteria-free nutrient broth control. Another pair of enterotoxigenic E. coli strains, 1628–14 (LT+ , ST+ , CFA/I+ ) and 1628–15 (LT+ , ST− and CFA/I− ) both increased the intestinal permeability. The observations indicate that the LT+ -only E. coli strain 1628–15 has the ability to promote permeability of rat intestine. The toxin-negative, rough S. typhimurium 395MR10 bacteria had a very small effect on the permeability, which was also achieved with culture filtrate only.
It is concluded that enterotoxigenic E. coli (ETEC) can alter the properties of the mucosal barrier towards intermediate-sized molecules that could be of antigenic significance, or which could play a crucial role in the nutritional status of the host organism. 相似文献
It is concluded that enterotoxigenic E. coli (ETEC) can alter the properties of the mucosal barrier towards intermediate-sized molecules that could be of antigenic significance, or which could play a crucial role in the nutritional status of the host organism. 相似文献
136.
Characterization of a pleiotropic succinate dehydrogenase-negative mutant of Bacillus subtilis 总被引:4,自引:0,他引:4
A succinate dehydrogenase-negative mutant of Bacillus subtilis is described which lacks all three subunits of the membrane-bound succinate dehydrogenase complex: flavoprotein, iron protein, and cytochrome b558. The corresponding mutation is revertible and it maps at one extreme of the sdh region. The results presented suggest that the structural genes for the subunits of the succinate dehydrogenase complex are part of one operon. 相似文献
137.
Overproduction of outer membrane protein suppresses envA-induced hyperpermeability. 总被引:5,自引:3,他引:2 下载免费PDF全文
A quantitative study on outer membrane components was performed in a number of envelope mutants of Escherichia coli K-12 exhibition different permeability properties for antimicrobial agents. The envA1 allele causing an increased influx for both hydrophobic and hydrophilic drugs was found to be associated with a deficiency in the amount of lipopolysaccharides. The sefA1 envA1 double mutant was found to have a higher outer membrane buoyant density, apparently due to an increase in protein content. This double mutant was still low in lipopolysaccharide content. 相似文献
138.
The activity of MAO-A and MAO-B in four different brain regions (striatum, limbic system, occipito-temporal cortex and hemispheres) was determined after hemitransection of the left side. There was no difference in the MAO-A activities of either the left or right sides of the brain in either control or hemitransected rats. The activity of MAO-B was the same for both sides in control rats, but there was an increased MAO-B activity in the left side of the hemitransected rats with respect to the right side in all brain regions investigated, with the possible exception of the limbic system. The increase was due to a change in the Vmax rather than to a changed Km of the MAO-B. The interaction of the MAO-B with oxygen was unchanged after hemitransection. 相似文献
139.
C. Dahlgren I. Rundqvist O. Stendahl K. -E. Magnusson 《Cell biochemistry and biophysics》1980,2(3):253-267
The capacity of synthetic amphiphiles, poly(ethyleneglycol) 6000 (PEG) esterified with saturated fatty acids (C2–C18), to modify polymorphonuclear leukocyte (PMNL) locomotion has been investigated. It was noticed that PEG-myristate (M-PEG;
C14) stimulated the random locomotion of PMNL populations in concentrations up to about 1 g/L. The esters with shorter aliphatic
chains had negligible effects, whereas those with longer chains, PEG-palmitate (P-PEG; C16) and PEG-stearate (S-PEG; C18) reduced the locomotion, irrespectively of concentration. The ability of the PMNL to be stimulated by an attractant liberated
from normal human serum was slightly impaired by M-PEG, but not by P-PEG. The response to M-PEG of individual PMNL was heterogeneous
in that some cells were stimulated and others were inhibited. However, the average result was a reduction of the motility.
This indicates that methods used for the study of the locomotion of cell populations may not always reflect the average behavior
of the whole population. It was also concluded that the different effects of M-PEG and P-PEG owed to dissimilar effects on
the membrane structure of the PMNL since (1) M-PEG perturbated the PMNL membrane more than P-PEG, as assayed by the release
of superoxide anion (0
2
−
, although the binding was smaller, and (2) M-PEG and P-PEG increased and decreased the membrane fluidity, respectively, as
measured with fluorescent bleaching and recovery after bleaching of labeled PMNL. The results indicate a subtle coupling between
membrane structure and PMNL locomotion. 相似文献
140.
Different LPS mutants of Salmonella typhimurium and Salmonella minnesota have been investigated with respect to (1) their tendency to associate with HeLa cell monolayers, and (2) their physicochemical surface properties. Aqueous biphasic partitioning, hydrophobic interaction chromatography, and ion exchange chromatography have been used to characterize the bacterial cell surface properties with respect to charge and hydrophobicity. Liability to hydrophobic interaction was defined either by the change of partition in a dextran-polyethylene-glycol (PEG) system by the addition of PEG-palmitate (P-PEG), or by the elution pattern from Octyl-Sepharose. Accordingly, charge was asssessed by the effect of positively charged trimethylamino-PEG (TMA-PEG) on the partition, and by the elution from DEAE-Sephacel. Bacterial being negatively charged and liable to hydrophobic interaction had the highest tendency to associate with HeLa cells. In some cases the methods for surface analysis gave conflicting results on charge and/or liability to hydrophobic interaction of the same LPS mutant. Possible reasons for these differences and the role of bacterial cell surface structures contributing to physicochemical character are discussed. 相似文献