全文获取类型
收费全文 | 1994篇 |
免费 | 144篇 |
专业分类
2138篇 |
出版年
2022年 | 16篇 |
2021年 | 14篇 |
2020年 | 22篇 |
2019年 | 20篇 |
2018年 | 28篇 |
2017年 | 17篇 |
2016年 | 36篇 |
2015年 | 62篇 |
2014年 | 66篇 |
2013年 | 105篇 |
2012年 | 97篇 |
2011年 | 92篇 |
2010年 | 57篇 |
2009年 | 52篇 |
2008年 | 82篇 |
2007年 | 109篇 |
2006年 | 116篇 |
2005年 | 83篇 |
2004年 | 95篇 |
2003年 | 79篇 |
2002年 | 81篇 |
2001年 | 74篇 |
2000年 | 66篇 |
1999年 | 67篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 41篇 |
1991年 | 31篇 |
1990年 | 31篇 |
1989年 | 36篇 |
1988年 | 24篇 |
1987年 | 24篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1979年 | 18篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1975年 | 15篇 |
1974年 | 21篇 |
1973年 | 15篇 |
1972年 | 22篇 |
1971年 | 13篇 |
1970年 | 15篇 |
1966年 | 15篇 |
排序方式: 共有2138条查询结果,搜索用时 0 毫秒
1.
To explore the biological role of carbohydrate chains in the process of nerve cell differentiation, we carried out a characterization of the carbohydrate structure of glycoproteins by comparing conventional PC12 cells with variant cells (PC12D). In vitro metabolic labeling of cells with either [(3)H] glucosamine or [(3)H] threonine, together with tomato lectin staining, revealed that nerve growth factor (NGF) stimulation caused a decrease in the poly-N-acetyllactosamine synthesis of high-molecular-weight glycopeptides from PC12 cells. By comparison, the amount of glycopeptides with poly-N-acetyllactosamine from PC12D cells was already significantly low and it was not changed by NGF stimulation. By assaying the glycosyltransferases that participate in poly-N-acetyllactosamine synthesis, the decrease in the amount of the poly-N-acetyllactosamine in PC12D cells as well as NGF-stimulated PC12 cells could be accounted for by a reduction in the activity of poly-N-acetyllactosamine extension enzyme (GnT-i), because the amount of poly-N-acetyllactosamine in both cells precisely correlated with changes in GnT-i activity, whereas the activities of N-acetylglucosaminyltransferase V (GnT-V) and beta 1-4 galactosyltransferase remained unchanged. These results demonstrate that the decrease in poly-N-acetyllactosamine synthesis in PC12 cells occurred prior to neurite formation, whereas PC12D cells were insensitive to this effect. Next, we showed that GnT-i but not GnT-V catalyzed a rate-limiting reaction in the expression of poly-N-acetyllactosamine chains, especially in pheochromocytoma. 相似文献
2.
3.
4.
The role of tropomyosin in the interactions of F-actin with caldesmon and actin-binding protein (or filamin) 总被引:6,自引:0,他引:6
M Nomura K Yoshikawa T Tanaka K Sobue K Maruyama 《European journal of biochemistry》1987,163(3):467-471
The interactions of actin filaments with actin-binding protein (filamin) and caldesmon under the influence of tropomyosin were studied in detail using falling-ball viscometry, binding assay and electron microscopy. Caldesmon decreased the binding constant of filamin with F-actin. In contrast, the maximum binding ability of filamin to F-actin was decreased by tropomyosin. The filamin-induced gelation of actin filaments was inhibited by caldesmon. Tropomyosin also inhibited this gelation. The effect of caldesmon became stronger under the influence of tropomyosin. Furthermore, both caldesmon and tropomyosin additionally decreased the filamin binding to F-actin. From these results, caldesmon and tropomyosin appeared to influence filamin binding to F-actin with different modes of actin. In addition, there was no sign of direct interactions between filamin, caldesmon and tropomyosin as judged from gel filtration. Under the influence of caldesmon and tropomyosin, calmodulin conferred Ca2+ sensitivity on the filamin-induced gelation of actin filaments. 相似文献
5.
T Maruyama T Nomiyama M Asahi N Mori E Ono A Kawahara S Fujimoto 《Histology and histopathology》1989,4(1):85-94
Based on ultrastructural features of cellular components of a hemangiopericytoma, hyperplastic cells are classifiable into fibroblast-like (group I), endotheloid (group II) and pericyte-like (group III) cells. The transformation of the group I cells to the group II, or to the group III cells, is pronounced in our electron micrographs and this may imply that the group I cell is the principal cell of origin in this neoplasm. The smooth muscle-like (group IV) cells comprising the media of the arteries and veins in this neoplasm may represent modified, possibly de-differentiated smooth muscle cells reacted to the neoplastic proliferation of the surrounding adventitial (group I) cells. 相似文献
6.
7.
Regulation of Drosophila myosin ATPase activity by phosphorylation of myosin light chains--II. Flightless mfd- fly 总被引:1,自引:0,他引:1
S Takahashi H Takano-Ohmuro K Maruyama Y Hotta 《Comparative biochemistry and physiology. B, Comparative biochemistry》1990,95(1):183-185
1. The Ca2(+)-activated and Mg2+ actin-activated myosin ATPase activities of flightless mfd- mutant Drosophila flight muscle myosin were one-half and one-third of those of the wild-type fly muscle myosin, respectively. 2. In the two-dimensional gel electrophoresis, the spots corresponding to phosphorylated myosin light chains, Lfl and Ltl, were hardly detected in mfd- mutant myosin. 3. These results support not only the conclusion that phosphorylation of myosin light chains regulates Drosophila myosin ATPase activity but also the assumption that the phosphorylation of myosin light chains is directly involved in flight function of the Drosophila fly. 相似文献
8.
K Okazaki T Abe K Saruwatari F Kato K Maruyama K Tagawa 《Bioscience, biotechnology, and biochemistry》1992,56(9):1401-1405
An enzyme hydrolyzing nigeran (alternating alpha-1,3- and alpha-1,4-linked glucan) was purified from the culture filtrate of Streptomyces sp. J-13-3, which lysed the cell wall of Aspergillus niger, by percipitation with ammonium sulfate and column chromatographies on DEAE-Sephadex A-50, CM-Sephadex C-50, chromatofocusing, and Sephadex G-100. The final preparation was homogenous in polyacrylamide gel electrophoresis (PAGE). The molecular weight of the enzyme was 68,000 by SDS-PAGE and gel filtration. The optimum pH and temperature for the enzyme activity were 6.0 and 50 degrees C, respectively. The enzyme was stable in the pH range from 6.0 to 8.0 and up to 50 degrees C. The enzyme activity was inhibited significantly by Hg+, Hg2+, and p-chloromercuribenzoic acid. The Km (mg/ml) for nigeran was 3.33. The enzyme specifically hydrolyzed nigeran into nigerose and nigeran tetrasaccharide by an endo-type of action, indicating it to be a mycodextranase (EC 3.2.1.61) that splits only the alpha-1,4-glucosidic linkages in nigeran. 相似文献
9.
Actin-modulating activity was analysed with the 16,131-dalton calcium-binding light chain (CaLc, Kobayashi et al. (1988) J. Biol. Chem. 263, 305-313) of Physarum myosin, which is under an inhibitory Ca-control (Kohama and Kendrick-Jones (1986) J. Biochem. 99, 1433-1446). When skeletal muscle actin was polymerized in the presence of CaLc and Ca2+, increases in both viscosity and birefringence were reduced under high shear conditions. However, CaLc did not inhibit actin polymerization under no or low shearing forces, which was demonstrated by a variety of methods including fluorescence intensity measurements using pyrenyl actin. We propose that actin polymerized in the presence of CaLc and Ca2+ is easily fragmented under high shearing forces to produce the changes in viscosity and birefringence. 相似文献
10.
Gene structure of human thrombomodulin, a cofactor for thrombin-catalyzed activation of protein C 总被引:2,自引:0,他引:2
T Shirai S Shiojiri H Ito S Yamamoto H Kusumoto Y Deyashiki I Maruyama K Suzuki 《Journal of biochemistry》1988,103(2):281-285
The gene coding for human thrombomodulin, a thrombin receptor on endothelial cells and a cofactor for the activation of anticoagulant protein C zymogen, was isolated from a human genomic library by employing human thrombomodulin cDNA as a probe. The nucleotide sequences of the gene and the adjacent 5' and 3' flanking regions were then determined. The nucleotide sequence of this gene with approximately 3.7 kilobase pairs was identical to that of the cDNA, indicating that the gene for human thrombomodulin is free of introns. Hybridization data showed that there is only a single thrombomodulin gene in the human genome. 相似文献