全文获取类型
收费全文 | 126323篇 |
免费 | 3119篇 |
国内免费 | 2616篇 |
专业分类
132058篇 |
出版年
2024年 | 69篇 |
2023年 | 395篇 |
2022年 | 937篇 |
2021年 | 1638篇 |
2020年 | 1040篇 |
2019年 | 1255篇 |
2018年 | 12739篇 |
2017年 | 11277篇 |
2016年 | 8587篇 |
2015年 | 2593篇 |
2014年 | 2633篇 |
2013年 | 2826篇 |
2012年 | 7179篇 |
2011年 | 15318篇 |
2010年 | 13494篇 |
2009年 | 9517篇 |
2008年 | 11305篇 |
2007年 | 12708篇 |
2006年 | 1599篇 |
2005年 | 1634篇 |
2004年 | 1958篇 |
2003年 | 1859篇 |
2002年 | 1505篇 |
2001年 | 931篇 |
2000年 | 838篇 |
1999年 | 678篇 |
1998年 | 394篇 |
1997年 | 359篇 |
1996年 | 368篇 |
1995年 | 333篇 |
1994年 | 332篇 |
1993年 | 245篇 |
1992年 | 371篇 |
1991年 | 307篇 |
1990年 | 313篇 |
1989年 | 264篇 |
1988年 | 206篇 |
1987年 | 184篇 |
1986年 | 152篇 |
1985年 | 134篇 |
1984年 | 128篇 |
1983年 | 112篇 |
1982年 | 79篇 |
1981年 | 61篇 |
1979年 | 75篇 |
1978年 | 55篇 |
1977年 | 53篇 |
1975年 | 64篇 |
1972年 | 287篇 |
1971年 | 310篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
331.
M. Islam Khan M. K. Mathew T. Mazumdar D. Pain N. Surolia M. K. Das P. Balaram A. Surolia 《Journal of biosciences》1983,5(1):31-39
The binding ofRicinus communis agglutinin andAbrus agglutinin to 4-methylumbelliferyl β-D-galactopyranoside was studied by equilibrium dialysis, fluo-rescence quenching and fluorescence polarization. The number of binding sites and the association constant value obtained by fluorescence polarization for bothRicinus communis agglutinin andAbrus agglutinin are in close agreement with those obtained by the other methods. This indicates the potential of ligand-fluorescence polarization measurements in the investigation of lectin-sugar interactions. 相似文献
332.
Irwin J. Goldstein 《Journal of biosciences》1983,5(1):65-71
The physical-chemical and carbohydrate binding specificity ofGriffonia simplicifolia I (GS I) isolectins, one of the 4 lectins isolated fromGriffonia simplicifolia seeds, are described.Association constants for the binding of methyl α- and β-D-galactopyranoside and methyl 2-acetamido-2-deoxy-α-D-galactopyranoside to the A4, A2 B2 and B4 isolectins are reported.Precipitation reactions of theGriffonia simplicifolia isolectins with guaran and type B blood group substance are described.The hypothesis that subunit B is a precursor of subunit A, a process involving proteolytic cleavage of the B subunit, was tested by conducting structural studies on the 2 subunits. The results indicated that the A and B subunits are probably products of 2 separate but closely related, possibly contiguous genes. 相似文献
333.
The kinetics of haemolysis of rabbit erythrocytes byCroton tiglium lectin was studied as a function of concentration of the lectin and erythrocytes. The length of the prelytic period decreased with increasing lectin concentrations, indicating that the secondary events at the membrane which follow the binding of the lectin to cell surface carbohydrate receptors are accelerated at higher surface concentrations of the lectin. The rate or extent of haemolysis was not affected by the inclusion of ions like K+, Ca2+ and Mg2+ in the medium or by the substitution of ionic medium by a non-ionic medium. The inhibition of haemagglutination and haemolysis of rabbit red cells byCroton tiglium lectin by antilectin rabbit serum was observed. A possible mechanism of haemolysis by the lectin is discussed. 相似文献
334.
N-Acetyl-D-galactosamine in β-linkage being ubiquitous in cell surface glycoproteins, their interaction with lectins specific for this sugar moiety may be a significant event in cell adhesion phenomena. This article discusses the common β-N-acetyl galactosamine-specific lectins, with particular stress on the lectin from winged beans (Psophocarpus tetragonolobus). 相似文献
335.
Kunio Yamato I-Yih Huang Helmut Muensch Akira Yoshida Heinz-Werner Goedde Dharam P. Agarwal 《Biochemical genetics》1983,21(1-2):135-145
The usualE 1 u and atypicalE 1 a human pseudocholinesterases (acylocholine acylhydrolase, EC 3.1.1.8) were purified to homogeneity. The active-site serine residue was conjugated with diisopropyl fluorophosphate and digested with trypsin. The tryptic peptide containing the active site was isolated by gel filtration followed by two-dimensional paper chromatography and electrophoresis. The amino acid sequence of the active site peptide obtained from the usualE 1 u enzyme was found to be Gly-Glu-Ser-Ala-Gly-Ala-Ser-Ala-Val-Ser-Leu. A remarkable structural homology exists between the human and the horse enzymes in their active sites. From the difference in electrophoretic mobility of the active-site peptides obtained from the usual and atypical enzymes, the probable structure of the atypical human enzyme was deduced as Gly-His-Ser-Ala-Gly-Ala-Ser-Ala-Val-Ser-Leu. 相似文献
336.
Inhibition of amino acid and sugar transport by showdomycin 总被引:1,自引:0,他引:1
S Roy-Burman Y H Huang D W Visser 《Biochemical and biophysical research communications》1971,42(3):445-453
337.
Specialized microbodies have previously been isolated and characterized from fatty seedling tissues (glyoxysomes) and leaves (leaf peroxisomes). We have now examined 11 other plant tissues, including tubers, fruits, roots, shoots, and petals, and find that all contain particulate catalase, a distinctive common enzyme component of microbodies. On linear sucrose gradients the catalase activity peaks sharply at a higher equilibrium density (1.20 to 1.25 gram per cm3 in the various tissues) than the mitochondria (1.17 to 1.20). Only small amounts of protein are recovered in the fractions containing catalase, although a definite band is visible in preparations from some tissues, e.g., potato. As in the preparations from castor bean endosperm and spinach leaves for which comparable data are provided, the distribution of glycolate oxidase and uricase follows closely that of catalase on the gradients. The preparations from potato lack glyoxylate reductase and the transaminases, typical enzymes of leaf peroxisomes, and the distinctive enzymes of glyoxysomes are missing. Nonspecialized microbodies with limited enzyme composition can thus be isolated from a variety of plant tissues. 相似文献
338.
Role of Peroxidase when Hydroxyproline-rich Protein in Plant Cell Walls is increased by Ethylene 总被引:9,自引:0,他引:9
Ethylene may control the growth of plant cells by regulating hydroxylation of specific wall proteins. 相似文献
339.
IMMUNOGLOBULIN polypeptide chains consist of two well defined regions designated the “variable region” and the “constant region”. Whereas great diversity exists in amino-acid sequences of variable regions, the constant regions of a given subclass of heavy chains (CH)* are essentially invariant in sequence1, 2. Exceptions are the allelic forms, such as the rabbit allotypes A14 and A153, 4, where a threonine-alanine interchange occurs in the constant region of γ chains (Appella, Chersi, R. G. M. and Dubiski, in preparation). The markers unique to a chains (for example, A14-A15) are closely linked to allotypic markers at the a locus (a1, a2, a3)3, 4 which seem to be present on four different Ig heavy chain classes (α, γ, ε, µ)5–7. These puzzling observations can be explained if the a locus determinants are variable region markers which reflect genetically controlled differences in some relatively constant residues within the VH region sequences7. 相似文献
340.
Mitochondrial Ribosomes in HeLa Cells 总被引:5,自引:0,他引:5
HeLa cell mitochondria contain 60S ribosomes which seem to consist of subunits of 45S and 35S particles. The 16S and 12S RNA components are coded by mitochondrial DNA. 相似文献