全文获取类型
收费全文 | 6092篇 |
免费 | 647篇 |
国内免费 | 1篇 |
专业分类
6740篇 |
出版年
2021年 | 60篇 |
2019年 | 49篇 |
2018年 | 62篇 |
2017年 | 51篇 |
2016年 | 106篇 |
2015年 | 150篇 |
2014年 | 201篇 |
2013年 | 271篇 |
2012年 | 334篇 |
2011年 | 358篇 |
2010年 | 218篇 |
2009年 | 196篇 |
2008年 | 318篇 |
2007年 | 379篇 |
2006年 | 321篇 |
2005年 | 358篇 |
2004年 | 319篇 |
2003年 | 325篇 |
2002年 | 303篇 |
2001年 | 74篇 |
2000年 | 51篇 |
1999年 | 88篇 |
1998年 | 93篇 |
1997年 | 63篇 |
1996年 | 65篇 |
1995年 | 67篇 |
1994年 | 63篇 |
1993年 | 56篇 |
1992年 | 72篇 |
1991年 | 48篇 |
1990年 | 52篇 |
1989年 | 50篇 |
1988年 | 52篇 |
1987年 | 54篇 |
1985年 | 58篇 |
1984年 | 81篇 |
1983年 | 60篇 |
1982年 | 72篇 |
1981年 | 97篇 |
1980年 | 80篇 |
1979年 | 47篇 |
1978年 | 65篇 |
1977年 | 70篇 |
1976年 | 60篇 |
1975年 | 49篇 |
1974年 | 59篇 |
1973年 | 41篇 |
1970年 | 44篇 |
1969年 | 43篇 |
1967年 | 45篇 |
排序方式: 共有6740条查询结果,搜索用时 15 毫秒
991.
992.
In response to fluctuations in environmental osmolarity, yeast cells adjust their intracellular solute concentrations in order to maintain a constant turgor pressure and ensure continuation of cellular activity. In this study, the effect of hypo-osmotic stress on osmolyte content of osmotolerant yeasts Zygosaccharomyces rouxii and Pichia sorbitophila and the less tolerant Saccharomyes cerevisiae was investigated. All these yeasts released glycerol upon hypo-osmotic shock. However, Z. rouxii also released arabitol, whereas P. sorbitophila released erythritol in addition to arabitol and glycerol. Osmolyte release was very rapid and specific and was neither affected by reduced temperatures nor inhibited by the channel blocker gadolinium or the protonophore carbonyl cyanide m-chlorophenyl hydrazone. Extracellular osmolyte levels increased drastically suggesting that osmolytes were not metabolised but mainly released upon exposure to hypotonic conditions. The export process is well controlled, and the amount of osmolyte released was proportional to the shock intensity. Osmolyte release occurred with little cell lysis and thus the survival as well as the subsequent growth of yeast cells was largely unaffected after hypo-osmotic shock. The kinetics and patterns of osmolyte export suggest the involvement of channel proteins, but the molecular nature of this export pathway in yeasts, with exception of S. cerevisiae, remains to be established. 相似文献
993.
Ron J.G. Kaandorp Hubert B. VonhofCahuide Del Busto Frank P. Wesselingh Gerald M. GanssenAndrés E. Marmól Lidia Romero PittmanJan E. van Hinte 《Palaeogeography, Palaeoclimatology, Palaeoecology》2003,194(4):339-354
In a floodplain lake of the Amazon River near the city of Iquitos, northeastern Peru, a one-year monitoring experiment was conducted during which water samples and living bivalves (Anodontites trapesialis) were collected with the aim to investigate seasonal δ18O variation in and fractionation between bivalve aragonite and host water. Both host water and molluscan growth increments show more than 8‰ seasonal variation in δ18O. In the floodplain lake under study the δ18O variation of the water is controlled by contrasting dry and wet season evaporation-precipitation regimes. Molluscan δ18O appears to be in equilibrium with the host water. Although an approximately 4.0‰ offset occurs, δ13C records of water and bivalves are in good agreement, suggesting that both δ18O and δ13C of the shells of freshwater bivalve A. trapesialis are good recorders of (palaeo-)environmental conditions. The δ13C of Dissolved Inorganic Carbon (DIC) is governed by plant growth and/or by changes in aquatic chemistry, affecting the DIC pool. 相似文献
994.
995.
Different effects of rat interferon alpha, beta and gamma on rat hepatic stellate cell proliferation and activation 总被引:1,自引:0,他引:1
Background
Liver fibrosis is the common sequel of chronic liver diseases. Recent studies have identified hepatic stellate cells as the primary cell type mediating hepatic fibrogenesis. It has been demonstrated that hepatic stellate cells undergo a process of activation during the development of liver fibrosis. During the activation process, hepatic stellate cells acquire myofibroblast-like phenotype featuring the expression of smooth muscle alpha actin. Interferons have been employed for the treatment of viral hepatitis. However, it is unclear what is the effect of interferons on the prevention and treatment of liver fibrosis. Moreover, it is not clear whether there are any differences among interferon alpha, interferon beta, and interferon gamma in the treatment of liver fibrosis. Therefore, our objective in current study is to investigate the effects of rat interferon-α, interferon-β, and interferon-γ on the proliferation and activation of rat hepatic stellate cells. 相似文献996.
997.
998.
Gerald E. Gaull M.D. 《Neurochemical research》1996,21(10):1267-1268
999.
1000.