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排序方式: 共有190条查询结果,搜索用时 15 毫秒
41.
42.
W J Peumans A Barre V Derycke P Rougé W Zhang G D May J A Delcour F Van Leuven E J Van Damme 《European journal of biochemistry》2000,267(4):1188-1195
An abundant, catalytically active beta-1,3-endoglucanase (EC 3.2.1. 39) has been isolated from the pulp of ripe bananas. Biochemical analysis of the purified protein, molecular modelling, and molecular cloning of the corresponding gene indicate that this banana enzyme closely resembles previously characterized plant beta-glucanases with respect to its amino-acid sequence, structure and biological activity. The results described in this paper demonstrate both the occurrence of an abundant active beta-1,3-endoglucanases in fruits and also readdress the question of the possible involvement of these enzymes in the ripening and/or softening process. 相似文献
43.
Serum lathosterol concentration is an indicator of whole-body cholesterol synthesis in humans 总被引:6,自引:0,他引:6
H J Kempen J F Glatz J A Gevers Leuven H A van der Voort M B Katan 《Journal of lipid research》1988,29(9):1149-1155
The power of serum lathosterol concentration as an indicator of whole-body cholesterol synthesis was investigated in 47 human volunteers consuming two diets differing in fatty acid composition. The cholesterol balance (fecal excretion of neutral and acid steroids minus cholesterol intake) was strongly correlated with the serum level of total (free plus esterified) lathosterol and also with the ratio of serum lathosterol over serum cholesterol, both on a diet rich in polyunsaturated fatty acids (r = 0.74 for the ratio) and one containing mainly saturated fatty acids (r = 0.70 for the ratio). In a subgroup for which the serum levels of free lanosterol and other free methylsterols were also quantitated, the correlations of these levels (expressed relative to serum free cholesterol) with the cholesterol balance were lower than that found for total lathosterol (expressed relative to serum total cholesterol). A further corroboration was obtained by measuring the lathosterol/cholesterol ratio in 20 patients with familial hypercholesterolemia before and during treatment with the hydroxymethylglutaryl coenzyme A reductase inhibitor Mk-733. The ratio was lowered by 47% during drug treatment, suggesting a significant decrease of the cholesterol balance in these patients. We conclude, from the various indicators proposed to monitor whole-body cholesterol synthesis, that the lathosterol/cholesterol ratio in serum appears preferable with respect to indicative power and ease of quantitation. 相似文献
44.
The seed lectins of black locust (robinia pseudoacacia) are encoded by two genes which differ from the bark lectin genes 总被引:2,自引:0,他引:2
Els J. M. Van Damme Annick Barre Pierre Rougé Fred Van Leuven Willy J. Peumans 《Plant molecular biology》1995,29(6):1197-1210
Two lectins were isolated from Robinia pseudoacacia (black locust) seeds using affinity chromatography on fetuin-agarose, and ion exchange chromatography on a Neobar CS column. The first lectin, R. pseudoacacia seed agglutinin I, referred to as RPsAI, is a homotetramer of four 34 kDa subunits whereas the second lectin, referred to as RPsAII, is composed of four 29 kDa polypeptides. cDNA clones encoding the polypeptides of RPsAI and RPsAII were isolated and their sequences were determined. Both polypeptides are translated from mRNAs of ca. 1.2 kb encoding a precursor carrying a signal peptide. Alignment of the deduced amino acid sequences of the different clones indicates that the 34 and 29 kDa seed lectin polypeptides show 95% sequence identity. In spite of this striking homology, the 29 kDa polypeptide has only one putative glycosylation site whereas the 34 kDa subunit has four of these sites. Carbohydrate analysis revealed that the 34 kDa possesses three carbohydrate chains whereas the 29 kDa polypeptide is only partially glycosylated at one site. A comparison of the deduced amino acid sequences of the two seed and three bark lectin polypeptides demonstrated unambiguously that they are encoded by different genes. This implies that five different genes are involved in the control of the expression of the lectins in black locust.Abbreviations LECRPAs
cDNA clone encoding Robinia pseudoacacia seed lectin
- LoLI
Lathyrus ochrus isolectin I
- PsA
Pisum sativum agglutinin
- RPbAI
Robinia pseudoacacia bark agglutinin I
- RPbAII
Robinia pseudoacacia bark agglutinin II
- RPsAI
Robinia pseudoacacia seed agglutinin I
- RPsAII
Robinia pseudoacacia seed agglutinin II 相似文献
45.
Willy J. Peumans Koen Smeets Karel Van Nerum Fred Van Leuven Els J. M. Van Damme 《Planta》1997,201(3):298-302
Analysis of nectar from leek (Allium porrum) flowers by SDS-PAGE revealed the presence of two major polypeptide bands of 50 kDa and 13 kDa, respectively. Using a combination
of agglutination tests, enzyme assays and N-terminal sequencing, the polypeptides have been identified as subunits of alliin
lyase (alliinase, EC 4.4.1.4) and mannose-binding lectin, respectively. The latter protein is particularly abundant since
it represents about 75% of the total nectar protein. Honey produced by bees foraging on flowering leek plants still contains
biologically active lectin and alliinase. However, the levels of both proteins are strongly reduced as compared to those in
the original nectar. It is evident, therefore, that the lectin as well as the alliinase are inactivated/degraded during the
conversion of nectar into honey.
Received: 24 May 1996 / Accepted: 19 August 1996 相似文献
46.
A detailed study was made of the bark lectins of the legume tree Maackia amurensis using a combination of protein purification
and cDNA cloning. The lectins, which are the most abundant bark proteins, are a complex mixture of isoforms composed of two
types of subunits of 32 and 37 kDa, respectively. Isolation and characterization of the homotetrameric isoforms indicated
that the 32 kDa subunit exhibits a 100-fold stronger haemagglutinating activity than the 37 kDa subunit. Molecular cloning
confirmed that the two lectin subunits are encoded by different genes. The 32 kDa subunit is apparently encoded by a single
gene, whereas two highly homologous genes encode the 37 kDa subunit. A comparison of the deduced amino acid sequences of the
bark lectin cDNAs and the previously described cDNA encoding the seed haemagglutinin demonstrated that they are encoded by
different genes. Abbreviations: LECMAHb, cDNA clone encoding Maackia amurensis bark haemagglutinin; LECMALb, cDNA clone encoding
Maackia amurensis bark leucoagglutinin; MALb, Maackia amurensis bark leucoagglutinin; MAHb, Maackia amurensis bark haemagglutinin
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
47.
L. H. T. Dederen † R. S. E. W. Leuven S. E. Wendelaar † F. G. F. Oyen 《Journal of fish biology》1986,28(3):307-326
In The Netherlands, the mudminnow Umbra pygmaea mainly occurs in water bodies with a pH ranging from 3–5 to 4–0, an alkalinity less than 0.1 meq 1−1 and a calcium content below 100 μmol 1−1 . The abundance of mudminnows is inversely related to the pH and the presence of predatory fish species. Experimental studies show that If. pygmaea is extremely acid-tolerant. Exposure to media with pH values ranging from 4.0 to 7.0 did not cause mortality or significant changes in blood plasma osmolarity and haematocrit. At pH 3.0 no mortality was recorded although a strong decrease in the plasma osmolarity was observed. Exposure to pH 2.8 and calcium concentrations of 100 or 500 μ mol 1−1 for 10 days caused 70% and 40% mortality respectively. The growth, reproduction and feeding of mudminnows are described. Age-growth and length-age relationships were calculated. Gonadal development started between September and January. The highest Gonado Somatic Index was recorded in spring. Spawning occurred from April to May. Fecundity of a sample of females was assessed. Nematocera provided the main item of diet of U. pygmaea; the microfauna ingested was dominated by Cladocera. The adaptations of mudminnows to acid environments are discussed. 相似文献
48.
Apolipoprotein E3-Leiden. A new variant of human apolipoprotein E associated with familial type III hyperlipoproteinemia 总被引:8,自引:2,他引:6
L. Havekes Elly de Wit J. Gevers Leuven E. Klasen W. Utermann W. Weber Ulrike Beisiegel 《Human genetics》1986,73(2):157-163
Summary A variant of apolipoprotein E, denoted apo E3-Leiden, has been identified in a 41-year-old male suffering from type III hyperlipoproteinemia with xanthomatosis. Apo E3-Leiden focus in the E3 position. In contrast with normal apo E3, apo E3-Leiden is defective in binding to the low density lipoprotein (LDL) receptor and does not contain cysteine as evaluated by cysteamine treatment of very low density lipoprotein followed by isoelectric focusing and conventional protein staining and by amino acid analysis. On sodium dodecyl sulfate polyacrylamide gel electrophoresis, apo E3-Leiden displays an electrophoretic mobility intermediate to that of normal apo E3 and apo E2 (Arg158Cys). The mother and four siblings of the proband also have apo E3-Leiden and hyperlipoproteinemia type III; three of them with xanthomatosis. Two siblings do not show apo E3-Leiden in their VLDL fraction and do not have hyperlipoproteinemia type III. In the VLDL fractions of all affected family members only the presence of apo E3-Leiden could be detected after cysteamine treatment and isoelectric focusing followed by conventional protein staining. However, isoelectric focusing of cysteaminetreated sera followed by immunoblotting, using anti-apo E antiserum as first antiserum, demonstrates the presence of low amounts of normal apo E3 in addition to apo E3-Leiden in serum of the affected family members. These results indicate that all affected family members are heterozygotes E3/E3-Leiden and suggest that in this family type III hyperlipoproteinemia is transmitted as a dominant trait. 相似文献
49.
Identification of cell surface dipeptidylpeptidase IV in human fibroblasts. 总被引:1,自引:0,他引:1 下载免费PDF全文
M Saison J Verlinden F Van Leuven J J Cassiman H Van den Berghe 《The Biochemical journal》1983,216(1):177-183
An antigen with dipeptidylpeptidase IV activity was identified at the surface of normal human fibroblasts. Hydrophobic interaction electrophoresis in phenyl-Sepharose revealed that the enzyme contained a hydrophobic domain, while lactoperoxidase-catalysed iodination with 125I of living cells indicated that the protein was located at the cell surface. Crossed immunoelectrophoresis with specific antibodies of acid-extracted or papain-treated cells showed a shift of the dipeptidylpeptidase IV peak to a faster mobility. The molecular properties of the fibroblast enzyme were clearly different from those described for dipeptidylpeptidase IV from other tissues and species. Fibroblast dipeptidylpeptidase IV contained two different disulphide-linked subunits, of apparent Mr values 125000 and 135000 (denatured and reduced). In gel filtration, an Mr of about 400000 was observed for the unreduced molecule. The enzymic properties of fibroblast dipeptidylpeptidase IV were very similar to those of the well-characterized pig kidney enzyme. Activity towards glycyl-L-prolyl-beta-naphthylamide was inhibited 50% by 0.023 mM-di-isopropylphosphorofluoridate. L-Alanyl-L-alanyl-beta-naphthylamide was hydrolysed ten times more slowly than glycyl-L-prolyl-beta-naphthylamide. 相似文献
50.