全文获取类型
收费全文 | 2783篇 |
免费 | 241篇 |
出版年
2023年 | 9篇 |
2022年 | 9篇 |
2021年 | 40篇 |
2020年 | 22篇 |
2019年 | 32篇 |
2018年 | 43篇 |
2017年 | 36篇 |
2016年 | 65篇 |
2015年 | 97篇 |
2014年 | 143篇 |
2013年 | 133篇 |
2012年 | 163篇 |
2011年 | 195篇 |
2010年 | 140篇 |
2009年 | 118篇 |
2008年 | 139篇 |
2007年 | 141篇 |
2006年 | 149篇 |
2005年 | 104篇 |
2004年 | 141篇 |
2003年 | 129篇 |
2002年 | 125篇 |
2001年 | 59篇 |
2000年 | 56篇 |
1999年 | 57篇 |
1998年 | 43篇 |
1997年 | 32篇 |
1996年 | 37篇 |
1995年 | 18篇 |
1994年 | 25篇 |
1993年 | 26篇 |
1992年 | 40篇 |
1991年 | 28篇 |
1990年 | 32篇 |
1989年 | 32篇 |
1988年 | 26篇 |
1987年 | 19篇 |
1986年 | 31篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 20篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 9篇 |
1979年 | 34篇 |
1978年 | 31篇 |
1977年 | 14篇 |
1976年 | 11篇 |
1974年 | 11篇 |
1972年 | 11篇 |
排序方式: 共有3024条查询结果,搜索用时 15 毫秒
81.
Claire Zehnacker Thomas W. Becker Akira Suzuki Elisa Carrayol Michel Caboche Bertrand Hirel 《Planta》1992,187(2):266-274
Ferredoxin-dependent glutamate synthase (Fd-GOGAT, EC 1.4.7.1) was purified to electrophoretic homogeneity from leaves of tobacco (Nicotiana tabacum L.). The holoenzyme is a monomeric flavoprotein with a molecular weight of 164 kDa. Polyclonal rabbit antibodies against the purified enzyme were used to isolate a 450-bp Fd-GOGAT cDNA clone (C16) from a tobacco gt11 expression library. A longer Fd-GOGAT cDNA clone (C35) encoding about 70% of the amino acids of tobacco Fd-GOGAT was isolated from a tobacco gt10 cDNA library using C16 as the probe. The amino-acid sequence of the protein encoded by the Fd-GOGAT cDNA clone C35 was delineated. It is very likely that Fd-GOGAT is encoded by two genes in the amphidiploid genome of tobacco while only a single Fd-GOGAT gene appears to be present in the diploid genome of Nicotiana sylvestris. Two Fd-GOGAT isoenzymes could be distinguished in extracts of tobacco leaf protein. In contrast, a single Fd-GOGAT protein species was detected in leaves of Nicotiana sylvestris speg. et Comes. In tobacco leaves, the 6-kb Fd-GOGAT mRNA is about 50-fold less abundant than chloroplastic glutamine synthetase (EC 6.3.1.2) mRNA. Both Fd-GOGAT mRNA and Fd-GOGAT protein accumulated during greening of etiolated tobacco leaves, and a concomitant increase in Fd-GOGAT activity was observed. These results indicate that tobacco Fd-GOGAT gene expression is light-inducible. Levels of Fd-GOGAT mRNA in tobacco organs other than leaves were below the detection limit of our Northern-blot analysis. Polypeptides of Fd-GOGAT were present in tobacco leaves and, to a lesser extent, in pistils and anthers, but not in corollas, stems and roots. These results support organ specificity in tobacco Fd-GOGAT gene expression.Abbreviations bp
base pairs
- Fd-GOGAT
ferredoxin-dependent glutamate synthase
- GS
glutamine synthetase
- PAGE
polyacrylamide gel electrophoresis
- SDS
sodium dodecyl sulfate
The authors wish to thank Juan Luis Gómez Pinchetti (Marine Plant Biotechnology Laboratory) for his assistance during the experiments. This study was supported by grants received from SAREC (Swedish Agency for Research Cooperation with Developing Countries), Carl Tryggers Fund for Scientific Research (K. Haglund), SJFR (Swedish Council for Forestry and Agricultural Research) (M. Björk, M. Pedersén), CITYT Spain (SAB 89-0091 and MAR 91-1237, M. Pedersén) and CICYT Spain (Z. Ramazanov, invited professor of Ministerio de Educatión y Ciencia, Spain). The planning of this cooperation was facilitated by COST-48. 相似文献
82.
Thomas W. Becker Michel Caboche Elisa Carrayol Bertrand Hirel 《Plant molecular biology》1992,19(3):367-379
83.
S el Ouggouti O Bournier P Boivin O Bertrand D Dhermy 《Protein expression and purification》1992,3(6):488-496
Protein 4.1 is a multifunctional structural protein occupying a strategic position in the erythrocyte membrane. It is present in the erythrocyte membrane skeleton and in many nonerythroid cells. This report describes a novel method for purifying this protein based on its selective interaction with inositol hexaphosphate dimagnesium tetrapotassium salt. This interaction was discovered in the course of chromatography of high-salt extract of inside-out membrane vesicles on Procion orange MX-2R-Sepharose. The new procedure is simple and selective and produces protein 4.1 with better yield than that obtained with a previously published procedure. The purified protein 4.1 has the same immunoreactivity and the same alpha-chymotryptic digest profile as protein 4.1 purified by published methods and is fully functional in enhancing the interaction between F-actin and spectrin dimers. 相似文献
84.
Cytochrome b5 from Candida tropicalis grown on alkane has been solubilized in three different ways (sodium cholate, trypsin, osmotic wash). After solubilization of the microsomal membrane with sodium cholate, the purification of cytochrome b5 was achieved by DEAE-cellulose chromatography, hydroxylapatite chromatography, a second DEAE-cellulose chromatography and a Sephadex G-75 gel filtration. The purified protein had an apparent molecular weight of 16 000 ± 1 000. After solubilization by trypsin treatment or osmotic wash, the purification procedure yielded a protein with an apparent molecular weight of 12 000 ± 1 000. Though the purified proteins presented molecular weights depending on the technique of solubilization, they exhibited identical optical properties, a great stability with respect to temperature and pH, and were all autooxidable. Redox titrations revealed differences in their midpoint potential values, which were 35 ± 5 mV for the b5 purified after cholate solubilization, —59 ± 5 mV for the b5 purified after trypsin treatment and —65 ± 5 mV for the b5 purified after osmotic wash. 相似文献
85.
86.
Rat immunoglobulin δ heavy-chain mRNA has been isolated. RNA blot analysis revealed that this mRNA with a length of 1.8 kb encodes for the secreted form of IgD. The corresponding cDNA was cloned in plasmid pBR322 and its sequence was determined. The hybrid plasmid contains a 775-bp insert comprising a partial Cδ1 sequence and complete CδH, Cδ3, CδDC and 3' untranslated sequences. Rat and mouse IgD amino acid sequences show striking homology in Cδ3 and CδDC regions. 相似文献
87.
Characterization and Purification from Human Brain of a Hyaluronic Acid-Binding Glycoprotein, Hyaluronectin 总被引:11,自引:4,他引:7
Using affinity chromatography and enzyme-labelled immunological assays combined with affinity adsorption, we have obtained evidence for the binding of a brain glycoprotein to hyaluronic acid, and on this basis named it hyaluronectin. This binding was inhibited by hyaluronic acid and by the products of its hydrolysis by hyaluronidase from bovine testis, but was not inhibited by other glycosaminoglycans or by monosaccharides. Preparative affinity chromatography of brain acid-soluble proteins produced hyaluronectin in a good degree of purity. Contamination by albumin was less than 1% and the yield was as high as 80%. 相似文献
88.
Richard A. Collins Helmut Bertrand Robert J. LaPolla Alan M. Lambowitz 《Molecular & general genetics : MGG》1981,181(1):13-19
Summary [C93] is a novel, extranuclear mutant of Neurospora crassa which has a normal mitochondrial phenotype when grown at 25°, but which is deficient in cytochromes b and aa
3 when grown at 37° (Pittenger and West 1979). In the present work, the phenotype of [C93] was characterized in greater detail. When [C93] is grown at 37°, the rate of mitochondrial protein synthesis is decreased to approximately 25% that of wild type; the ratio of mitochondrial small to large ribosomal subunits is decreased to 1:4 and mitochondrial small subunits are deficient in the mitochondrially-synthesized protein, S-5. The mitochondrial ribosome assembly defects in 37°-grown [C93] resemble those in chloramphenicol-treated wild-type cells and could merely be a consequence of the decreased rates of mitochondrial protein synthesis. Analysis of mitochondrial translation products by SDS gel electrophoresis suggests that 37°-grown [C93] is grossly deficient in the 19,000 Mr subunit of the oligomycin-sensitive ATPase relative to other mitochondrially-synthesized proteins. The ATPase defect was not found in other extranuclear or nuclear mutants deficient in mitochondrial protein synthesis. These data and additional evidence suggest that the primary defect in [C93] may be in the assembly of the ATPase complex. The possible connection between the ATPase defect and the deficiency of mitochondrial protein synthesis is discussed. 相似文献
89.
J P Gayda P Bertrand C More J Le Gall R C Cammack 《Biochemical and biophysical research communications》1981,99(4):1265-1270
Two different forms of cell-associated [35S]-heparan sulfate proteoglycans were identified in prelabeled cultured cells, including glial cells, endothelial cells and fibroblasts. One of them migrated characteristically in the excluded volume fraction in Sepharose CL-2B chromatography and flotated in CsCl density gradient centrifugation. Further, it showed affinity for a hydrophobic gel, Octyl-Sepharose. The molecular size was markedly reduced and the density elevated by treatment with detergent or lipid solvents. These findings indicate an admixture of lipid in this proteoglycan and suggest a location for the molecule in the plasma membrane. This proteoglycan was found in all cell species examined. - The other type of heparan sulfate proteoglycan had a larger molecular size than most previously described heparan sulfate proteoglycans and had a buoyant density around 1.32 g/ml, probably due to an unusually high ratio of protein to carbohydrate. This heparan sulfate proteoglycan was found only in extracts of cells capable of forming a fibrillar extracellular matrix, but not in extracts of cells devoid of matrix. It was retained in cell-free preparations of extracellular matrix, indicating that it may be a specific product of this compartment. 相似文献
90.