全文获取类型
收费全文 | 446701篇 |
免费 | 37622篇 |
国内免费 | 1002篇 |
出版年
2018年 | 16317篇 |
2017年 | 15262篇 |
2016年 | 12455篇 |
2015年 | 6030篇 |
2014年 | 6572篇 |
2013年 | 9143篇 |
2012年 | 15117篇 |
2011年 | 25098篇 |
2010年 | 20903篇 |
2009年 | 16540篇 |
2008年 | 20651篇 |
2007年 | 23222篇 |
2006年 | 8924篇 |
2005年 | 9804篇 |
2004年 | 9306篇 |
2003年 | 9267篇 |
2002年 | 9004篇 |
2001年 | 18459篇 |
2000年 | 18647篇 |
1999年 | 14136篇 |
1998年 | 4242篇 |
1997年 | 4525篇 |
1996年 | 4327篇 |
1995年 | 4010篇 |
1994年 | 3953篇 |
1993年 | 3827篇 |
1992年 | 11530篇 |
1991年 | 11189篇 |
1990年 | 10704篇 |
1989年 | 10278篇 |
1988年 | 9506篇 |
1987年 | 8879篇 |
1986年 | 8106篇 |
1985年 | 7980篇 |
1984年 | 6422篇 |
1983年 | 5597篇 |
1982年 | 4127篇 |
1981年 | 3602篇 |
1980年 | 3361篇 |
1979年 | 6129篇 |
1978年 | 4580篇 |
1977年 | 4138篇 |
1976年 | 3774篇 |
1975年 | 4360篇 |
1974年 | 4518篇 |
1973年 | 4398篇 |
1972年 | 4762篇 |
1971年 | 4124篇 |
1970年 | 3177篇 |
1969年 | 2971篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
791.
Thomas Cavalier-Smith 《Biology direct》2010,5(1):7
Background
The transition from prokaryotes to eukaryotes was the most radical change in cell organisation since life began, with the largest ever burst of gene duplication and novelty. According to the coevolutionary theory of eukaryote origins, the fundamental innovations were the concerted origins of the endomembrane system and cytoskeleton, subsequently recruited to form the cell nucleus and coevolving mitotic apparatus, with numerous genetic eukaryotic novelties inevitable consequences of this compartmentation and novel DNA segregation mechanism. Physical and mutational mechanisms of origin of the nucleus are seldom considered beyond the long-standing assumption that it involved wrapping pre-existing endomembranes around chromatin. Discussions on the origin of sex typically overlook its association with protozoan entry into dormant walled cysts and the likely simultaneous coevolutionary, not sequential, origin of mitosis and meiosis. 相似文献792.
A A Krichevskaia A I Lukash N V Pushkina I V Shepotinovskaia K B Sherstnev 《Nauchnye doklady vysshe? shkoly. Biologicheskie nauki》1984,(7):23-28
The amide content of total proteins and protein fractions (alpha-, beta-, gamma-cristallins and albuminoid) from cortex and nuclear lens zones of cattle has been investigated. The amide content in proteins of cortex and nuclear lens of young animals (1,5-2 years old) is the same. The decrease of the amide content in the proteins of nuclear lenz zone of old animals (6-12 years old) is due to fraction of readily hydrolysed amides. The data obtained prove the posttranslational desamidation of lens proteins at ageing. beta-Cristallines--the proteins with the highest amides content is exposed to posttranslational desamidation most of all. 相似文献
793.
794.
795.
796.
Inhibitory effect of ammonium chloride and chloroquine on the entry of the toxic lectin modeccin into HeLa cells 总被引:12,自引:0,他引:12
Ammonium chloride and chloroquine protected a variety of cell lines against diphtheria toxin and the toxic lectin modeccin. Experiments where the ability of antibody to neutralize the toxin was measured indicate that in the presence of ammonium chloride and chloroquine, modeccin remains at the cell surface and that the two compounds inhibit the uptake of modeccin into the cytoplasm. A cell line tolerating increased concentrations of modeccin was not protected against modeccin by ammonium chloride or chloroquine, whereas the compounds did protect these cells against diphtheria toxin. 相似文献
797.
G. Ricci L. Volpi L. Pasquali L. Petrozzi G. Siciliano 《Journal of biological physics》2009,35(4):317-336
Astrocytes have long been considered as just providing trophic support for neurons in the central nervous system, but recently
several studies have highlighted their importance in many functions such as neurotransmission, metabolite and electrolyte
homeostasis, cell signaling, inflammation, and synapse modulation. Astrocytes are, in fact, part of a bidirectional crosstalk
with neurons. Moreover, increasing evidence is stressing the emerging role of astrocyte dysfunction in the pathophysiology
of neurological disorders, including neurodegenerative disease, stroke, epilepsy, migraine, and neuroinflammatory diseases. 相似文献
798.
Using a solid-phase radioimmunoassay, serum IgE level was determined in 46 normal subjects, 53 patients with bronchial asthma, 44 patients with chronic bronchitis and / or emphysema, and 19 patients with restrictive lung disease. Sputum IgE was measured simultaneously in 51 of the subjects. The range of serum IgE concentration in the normal subjects was wide. It varied between 15 and 750 ng/ml with a mean of 135 ng. Asthmatic patients had significantly higher levels of serum IgE with a mean of 579 ng/ml, but only 30% fell outside the normal 95% confidence limits. Patients with chronic bronchitis, emphysema and restrictive lung diseases had normal IgE levels. There was a significant correlation between serum and sputum IgE levels. 相似文献
799.
800.