全文获取类型
收费全文 | 663962篇 |
免费 | 76370篇 |
国内免费 | 356篇 |
专业分类
740688篇 |
出版年
2016年 | 7586篇 |
2015年 | 10329篇 |
2014年 | 12153篇 |
2013年 | 17070篇 |
2012年 | 19245篇 |
2011年 | 19664篇 |
2010年 | 13499篇 |
2009年 | 12622篇 |
2008年 | 17950篇 |
2007年 | 18617篇 |
2006年 | 17521篇 |
2005年 | 17024篇 |
2004年 | 16846篇 |
2003年 | 16241篇 |
2002年 | 15823篇 |
2001年 | 25981篇 |
2000年 | 26101篇 |
1999年 | 21092篇 |
1998年 | 7961篇 |
1997年 | 8327篇 |
1996年 | 7925篇 |
1995年 | 7431篇 |
1994年 | 7339篇 |
1993年 | 7329篇 |
1992年 | 18121篇 |
1991年 | 17865篇 |
1990年 | 17462篇 |
1989年 | 17091篇 |
1988年 | 16255篇 |
1987年 | 15738篇 |
1986年 | 14712篇 |
1985年 | 14703篇 |
1984年 | 12373篇 |
1983年 | 10925篇 |
1982年 | 8544篇 |
1981年 | 7933篇 |
1980年 | 7461篇 |
1979年 | 12261篇 |
1978年 | 9717篇 |
1977年 | 9085篇 |
1976年 | 8708篇 |
1975年 | 9471篇 |
1974年 | 10493篇 |
1973年 | 10270篇 |
1972年 | 9603篇 |
1971年 | 8694篇 |
1970年 | 7661篇 |
1969年 | 7660篇 |
1968年 | 7139篇 |
1967年 | 6125篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
341.
ESR spectra of gamma-irradiated and frozen at 77 K human oxyhemoglobin and partially denaturated methemoglobin solutions were analysed. The quartet signal ascribed to the anion-radical of proximal histidine was shown to dominate in the spectra of both solutions. The spectra of methemoglobin solution irradiated with relatively small doses have an intensive singlet ascribed to the stabilized electron. The formation mechanism of free radicals is discussed. 相似文献
342.
343.
The dynamical structure of the RNA in alfalfa mosaic virus studied by 31P-nuclear magnetic resonance
The structure of the viral RNA in alfalfa mosaic virus (AlMV) was investigated by means of 31P-nuclear magnetic resonance (NMR). It was found that the 31P-NMR line width of AlMV Top a particles is significantly smaller than that of the larger Bottom particles. At low temperatures, the totational correlation time of the 31P nuclei essentially equals the tumbling rate of the virus particle, indicating that the RNA is contained rigidly inside the virion. At more elevated temperatures, the NMR line width sharpens more than expected on the basis of viscosity changes and the RNA exhibits internal mobility. The occurrence of internal mobility is paralleled by an increased internal mobility of the N-terminal part of the coat protein, as could be observed by 1H-NMR spectroscopy. The influence of EDTA on the 31P-NMR line width appeared to be negligible, which is in agreement with the idea that AlMV does not 'swell' like several other RNA-containing plant viruses. 相似文献
344.
345.
Biosynthesis of immunoglobulin A (IgA). Secretion and addition of carbohydrate to monomer and polymer forms of a mouse myeloma protein 总被引:9,自引:3,他引:6
Cell suspensions of mouse plasma-cell tumour MOPC 315 secreting predominantly IgA (immunoglobulin A) monomer and dimer were incubated with radioactive leucine, mannose, galactose and fucose for various periods of time. The amounts of secreted and intracellular immunoglobulins were measured by co-precipitation with specific antibody, and the molecular species present were assessed by electrophoresis in polyacrylamide gels. Analysis of the secreted myeloma protein demonstrated that monomer and dimer IgA molecules are identical with respect to carbohydrate composition and rate of secretion. Within the cell, the myeloma protein is almost entirely accounted for by monomer units which either leave the cell as such or are polymerized with the addition of J chain close to the time of secretion. The results support the concept of a stepwise addition of carbohydrate residues to IgA immunoglobulin during the process of secretion. Similar patterns of carbohydrate assembly were found for the monomer or dimer molecules. Mannose residues are added at an early stage, whereas fucose is added close to the time of secretion. Galactose is also added early, but some may also be incorporated at a later stage. Control of IgA polymerization is considered unlikely to reflect regulation at the level of carbohydrate addition, and it is suggested that the critical controlling factor is the J chain. 相似文献
346.
347.
348.
349.
350.