全文获取类型
收费全文 | 15083篇 |
免费 | 1607篇 |
国内免费 | 3315篇 |
出版年
2024年 | 50篇 |
2023年 | 278篇 |
2022年 | 531篇 |
2021年 | 774篇 |
2020年 | 583篇 |
2019年 | 815篇 |
2018年 | 684篇 |
2017年 | 579篇 |
2016年 | 718篇 |
2015年 | 998篇 |
2014年 | 1205篇 |
2013年 | 1247篇 |
2012年 | 1510篇 |
2011年 | 1384篇 |
2010年 | 927篇 |
2009年 | 847篇 |
2008年 | 992篇 |
2007年 | 856篇 |
2006年 | 775篇 |
2005年 | 651篇 |
2004年 | 598篇 |
2003年 | 545篇 |
2002年 | 493篇 |
2001年 | 317篇 |
2000年 | 244篇 |
1999年 | 197篇 |
1998年 | 136篇 |
1997年 | 113篇 |
1996年 | 97篇 |
1995年 | 57篇 |
1994年 | 64篇 |
1993年 | 42篇 |
1992年 | 53篇 |
1991年 | 47篇 |
1990年 | 59篇 |
1989年 | 41篇 |
1988年 | 28篇 |
1987年 | 26篇 |
1986年 | 33篇 |
1985年 | 28篇 |
1984年 | 23篇 |
1983年 | 24篇 |
1982年 | 17篇 |
1979年 | 24篇 |
1958年 | 16篇 |
1957年 | 19篇 |
1956年 | 17篇 |
1955年 | 21篇 |
1954年 | 17篇 |
1953年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Correlation between bilayer destabilization and activity enhancement by diacylglycerols in reconstituted Ca-ATPase vesicles 总被引:1,自引:0,他引:1
Using the reconstituted Ca-ATPase vesicles as a model system, we demonstrated that the presence of 1,2-dioleoyl-sn-glycerol (diolein) in the membrane introduces a pronounced enhancement in the Ca-transport function of Ca-ATPase, while the 1,2-dipalmitoyl-sn-glycerol (dipalmitin) does not. We also found by both 31P NMR and freeze-fraction electron microscopy that diolein destabilized lipid bilayers to a greater extent than did dipalmitin. We conclude that the tendency of diacylglycerols to destabilize the phospholipid bilayer is related to their capacity to enhance the activity of the membrane calcium pump. 相似文献
5.
6.
Studies on larval population densities and adult emergence rates of the Brugian filariasis vectors Mansonia bonneae Edwards and Ma. dives Schiner were conducted in freshwater swamp forest bordering the Sadong River, Serian District, Sarawak, East Malaysia, during 1984-85. Three species of aquatic host-plants in the Family Araceae were identified as supporting immature stages of the Ma. bonneae/dives complex. Proportions of positive plants were 4.7%, 6.5% and 3.4% with 6.4 +/- 2.6, 7.3 +/- 2.8 and 10.1 +/- 1.1 larvae per positive plant, respectively, for the plant species Homalomena cordata Schott, H. rostrata Griffiths and Hydrostemma motleyi (Hook. f.) Mabberley. These data indicate no significant preferences between the three types of host-plant. Detailed monitoring of the host-plant H. cordata revealed no significant monthly fluctuations in larval density per plant nor the proportion of positive plants. 11.6% of larvae were Ma. dives and 88.4% were Ma. bonneae. Mean daily yields of Ma. bonneae/dives adults per square metre of H. cordata vegetated water surface were 0.45 males plus 0.57 females during the wet season (December-February) compared with 0.2 males plus 0.31 females during the dry season (June-August). Thus output of adults per plant was approximately halved, and suitable breeding areas were further reduced, during the dry season. By extrapolation from these rates, a crude mean estimate for productivity of Ma. bonneae/dives females is 1.6 million per hectare per annum in swamp forest habitats vegetated with any of the host-plants studied. 相似文献
7.
8.
Yang Su-Rong Sun Huan-Xin Hu Zhen-Zhen Wang Si-Heng Sun Hui Xue Yin-Jia Ye Chen-Bo 《Sleep and biological rhythms》2017,15(1):57-65
Sleep and Biological Rhythms - Chronic sleep deprivation (SD) is an overwhelming problem in young students. Firstly, we investigated whether different levels of pre-training SD had effects on... 相似文献
9.
<正>Nanozymes, nanomaterials with enzyme-like characteristics,are emerging as novel artificial enzymes (Gao et al., 2007;Manea et al., 2004; Yan, 2018). They are superior to natural enzymes in many ways, such as higher stability, lower cost in preparation, and better robustness toward harsh environments (Wei and Wang, 2013). Various nanomaterials (e.g., 相似文献
10.
A neutral cholesterol esterase has been purified to homogeneity from the cytosolic fraction of rat liver. The 105,000 x g supernatant fraction of rat liver was applied to a DEAE-cellulose column to isolate a partially purified fraction of hepatic cholesterol esterase. Immunoblot analysis of the partially purified liver fraction with the anti-porcine pancreatic cholesterol esterase IgG demonstrated a single band with a molecular weight of 67,000. The hepatic protein was then isolated by immunoaffinity chromatography technique using a column constructed with antibodies prepared against the pancreatic cholesterol esterase. Characterization of the hepatic cholesterol esterase revealed that the hepatic enzyme shared antigenic epitopes with the pancreatic cholesterol esterase and was similarly activated by addition of bile salt such as taurocholate. Moreover, amino-terminal sequencing analysis of the hepatic cholesterol esterase showed an identical sequence with the pancreatic enzyme. Taken together, these results showed that the cholesterol esterases in the liver and the pancreas are very similar and possibly identical proteins. 相似文献