全文获取类型
收费全文 | 4254篇 |
免费 | 351篇 |
专业分类
4605篇 |
出版年
2023年 | 17篇 |
2022年 | 35篇 |
2021年 | 62篇 |
2020年 | 33篇 |
2019年 | 55篇 |
2018年 | 67篇 |
2017年 | 63篇 |
2016年 | 84篇 |
2015年 | 179篇 |
2014年 | 158篇 |
2013年 | 241篇 |
2012年 | 308篇 |
2011年 | 297篇 |
2010年 | 212篇 |
2009年 | 175篇 |
2008年 | 286篇 |
2007年 | 289篇 |
2006年 | 250篇 |
2005年 | 227篇 |
2004年 | 252篇 |
2003年 | 272篇 |
2002年 | 245篇 |
2001年 | 47篇 |
2000年 | 35篇 |
1999年 | 49篇 |
1998年 | 76篇 |
1997年 | 43篇 |
1996年 | 50篇 |
1995年 | 43篇 |
1994年 | 50篇 |
1993年 | 40篇 |
1992年 | 29篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 21篇 |
1984年 | 24篇 |
1983年 | 14篇 |
1982年 | 30篇 |
1981年 | 23篇 |
1980年 | 21篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1974年 | 9篇 |
1973年 | 7篇 |
排序方式: 共有4605条查询结果,搜索用时 0 毫秒
21.
Proteolytic activity of proteasome on myofibrillar structures 总被引:5,自引:0,他引:5
Richard G. Taylor Caroline Tassy Mariele Briand Nathalie Robert Yves Briand Ahmed Ouali 《Molecular biology reports》1995,21(1):71-73
The physiologic function of proteasome remains unclear. Evidence suggests a role in degradation of ubiquitin-protein conjugates, MHC antigen presentation, and some specificity of substrate within certain cell types. To explore further the properties of proteasome we have examined its effect on a well defined structure, the myofibril. We find that despite its large size (20S) proteasome is able to degrade myofibrils and intact, permeabilized muscle fibrils. The proteins degraded showed some specificity because actin, myosin and desmin were degraded faster than -actinin, troponin T and tropomyosin. Changes in ultrastructure were slow and included a general loss of structure with Z and I bands effected before the M band and costameres. 相似文献
22.
Christophe Tournamille Caroline Le Van Kim Pierre Gane Jean-Pierre Cartron Yves Colin 《Human genetics》1995,95(4):407-410
Spondyloepiphyseal dysplasia tarda (SEDL) is an X-linked recessive disorder characterized in affected males by short stature resulting from a growth defect of the vertebral bodies. We have extended our earlier studies by analyzing 15 families with newly identified microsatellite DNA markers; analysis of recombination events with these markers indicates that the gene responsible for SEDL is located in Xp22 between DXS 16 and DXS 987 on an interval spanning approximately 2 Mb. 相似文献
23.
Yves Hurtubise Franois Shareck Dieter Kluepfel Rolf Morosoli 《Molecular microbiology》1995,17(2):367-377
Centre de Recherche en Microbiologie Appliquée, Institut Armand-Frappier, Université du Québec, Ville de Laval, Québec H7N 4Z3, Canada. 相似文献
24.
25.
Dinoflagellate chromosomes observed in thin section show regular patterns which have been shown to correspond to a liquid crystalline helicoidal arrangement of DNA. Peripheral DNA filaments form a system of loops in the surrounding nucleoplasm. When such chromosomes (studied in Prorocentrum micans) are in presence of water, they extend considerably and form a double helical bundle. At the periphery of these bundles, one observes numerous filaments, which are smooth and devoid of nucleosomes; their diameter is constant.This study, in phase contrast and in electron microscopy, allows statistical measurements. A geometrical model is proposed and shows the simplest way to pass from the intact to the extended form. The liquid crystalline character of the chromosome is probably involved in the extension mechanisms. 相似文献
26.
Crystalline polysaccharides with 1 → 3−β and 1 → 4−β glycosidic linkages are the most prevalent ones in nature. An interpretation of recent X-ray data on 1 → 3−α glucan shows that it has a ribbon-like crystalline conformation similar to cellulose. Comparison of the crystalline conformation of the four principal homoglucans shows that they fall either in the ‘ribbon-like’ or ‘large amplitude’ helix class. Heteroglucans with a regular sequence of glucosidic linkages show characteristics of the ‘extended conformation’ rather than the ‘coiled conformation’ even when there is 50% of a linkage which in a homoglucan leads to a large amplitude helix. It is concluded that X-ray diffraction analysis fully establishes the hypothesis that the glycosidic linkage type is the determinant of polysaccharide conformation. In this respect, polysaccharides are more like synthetic polymers than proteins or nucleotides; in the latter, it is variation in the substituents which are responsible for the conformational diversity. 相似文献
27.
The effect of cytochalasin B, colchicine, coumarin and 2,6-dichlorobenzonitrile on cell wall formation and cellular division was studied by light and electron microscopy with tobacco mesophyll protoplasts cultivated in vitro. 2,6-dichlorobenzonitrile was found to be the most effective and reversible inhibitor of cell wall formation. The other inhibitors caused irreversible damage and/or inhibited mitosis. In protoplasts cultivated in the presence of 2,6-dichlorobenzonitrile the total inhibition of cell wall formation had no effect on nuclear division, but cytokinesis was totally inhibited so that multinucleate protoplasts were obtained.Abbreviations DB
2,6-dichlorobenzonitrile=dichlobenil
- CB
cytochalasin B 相似文献
28.
Martin Diatewa Yves Boulanger AndréJ.C. Stahl 《Biochemical and biophysical research communications》1982,106(2):520-525
The α and β subunits of yeast mitochondrial Phe-tRNA synthetase are separated and isolated by means of chromatography on DEAE-cellulose, after enzyme alkylation with iodoacetate. The comparison of amino acid compositions of yeast mitochondrial and cytoplasmic native Phe-tRNA synthetases and their components shows significant differences. Results indicate that the two enzymes are coded for by different nuclear genes. 相似文献
29.
Mhamed Sa?d El Kebbaj Norbert Latruffe Yves Gaudemer 《Biochemical and biophysical research communications》1982,108(1):42-50
In order to titrate and understand the role of arginyl residues of D-β-hydroxybutyrate dehydrogenase, arginyl specific reagents: butanedione, 1,2-cyclohexanedione and phenylglyoxal were incubated with three different forms of the enzyme; native enzyme (inner mitochondrial membrane bound), purified apoenzyme (phospholipid -free) and phospholipid-enzyme complex (reconstituted active form).After complete inactivation of the enzyme by [14C]-phenylglyoxal, the number of modified arginyl residues was different: one with the lipid-free apoenzyme and three with the phospholipid-enzyme complex, suggesting a conformational change of the enzyme triggered by the presence of phospholipids.After exhaustive chemical modification either of the apoenzyme or of the phospholipid-enzyme complex with [14C]-phenylglyoxal, four arginyl residues were titrated indicating that these residues are located in the hydrophilic part of the enzyme, not interacting with phospholipids.Reconstituted enzyme inactivated by butanedione could no longer bind a pseudosubstrate (succinate) which indicates that an arginyl residue is involved in the enzyme-substrate complex formation.The values of second order rate constants of D-β-hydroxybutyrate dehydrogenase inactivation by butanedione and 1,2-cyclohexanedione were unchanged with the three enzyme forms, suggesting that phospholipids are not involved in the substrate binding mechanism. 相似文献
30.
The genomic organization of two parasitic wasps was analyzed by DNA reassociation. Cot curves revealed a pattern with three types of components. A highly repetitive DNA, accounting for 15 to 25% of the genome, was identified as satellite DNA. The moderately repetitive DNA corresponds to 26 to 42% of the genome in both species, and shows large variations in complexity, repetitive frequency and a number of sub-components between males and females. These variations are seen as resulting from DNA amplification during somatic and sexual differentiation. Dot blot analyses show that such DNA amplifications concern several types of structural and regulatory genes. The presence of repeated mobile elements was studied by the Roninson method to compare the repeated sequence patterns of Diadromus pulchellus and Eupelmus vuilleti with those of Drosophila melanogaster. The occurrence and organization of mobile elements in these Hymenoptera differ from those of the neighboring order of Diptera. The repetitive and unique components define very large genomes (1 to 3 × 109 base pairs). The genomic organization in Parasitica appears to be an extreme drosophilan type. We propose that the germinal genome of these parasitic wasps is primarily composed of satellite DNA blocks and very long stretches of unique sequences, separated by a few repeated and/or variously deleted, interspersed elements of each mobile element family. 相似文献