全文获取类型
收费全文 | 22371篇 |
免费 | 2690篇 |
国内免费 | 7871篇 |
出版年
2024年 | 65篇 |
2023年 | 549篇 |
2022年 | 789篇 |
2021年 | 1210篇 |
2020年 | 1035篇 |
2019年 | 1294篇 |
2018年 | 986篇 |
2017年 | 896篇 |
2016年 | 1027篇 |
2015年 | 1464篇 |
2014年 | 1899篇 |
2013年 | 1829篇 |
2012年 | 2267篇 |
2011年 | 2226篇 |
2010年 | 1596篇 |
2009年 | 1554篇 |
2008年 | 1767篇 |
2007年 | 1618篇 |
2006年 | 1547篇 |
2005年 | 1316篇 |
2004年 | 1090篇 |
2003年 | 902篇 |
2002年 | 842篇 |
2001年 | 650篇 |
2000年 | 608篇 |
1999年 | 408篇 |
1998年 | 252篇 |
1997年 | 172篇 |
1996年 | 150篇 |
1995年 | 105篇 |
1994年 | 89篇 |
1993年 | 75篇 |
1992年 | 82篇 |
1991年 | 78篇 |
1990年 | 65篇 |
1989年 | 54篇 |
1988年 | 41篇 |
1987年 | 42篇 |
1986年 | 49篇 |
1985年 | 44篇 |
1984年 | 34篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 24篇 |
1980年 | 9篇 |
1979年 | 17篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1950年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
1.
2.
3.
4.
5.
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
6.
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.
XIAO-YUAN HE SHI-JUN WANG JASON HILTON fls YI-LONG ZHOU 《Botanical journal of the Linnean Society. Linnean Society of London》2006,151(2):279-288
Several isolated marattialean synangia and sporangia are reported from coal balls collected from Coal Seam No.1 (C605) in the uppermost Permian Wangjiazhai Formation in Guizhou Province, south-western China. The synangia are radially symmetrical with diameters between 0.8 and 1.2 mm and are 1.7 mm long, consisting of 3–4 elongate sporangia that are fused basally, free distally and possess a pointed apex. The outer-facing sporangial wall is 4–5 cells thick and conspicuously differentiated. Spores are trilete, have a granular ornamentation and are nearly round equatorially with a diameter of 55–60 µm. Comparisons with other anatomically preserved Palaeozoic marattialean synangia from the Euramerican and Cathaysian floras permit their assignment to the genus of Scolecopteris (Zenker) Millay. In this species the thick, outer-facing sporangial walls and large trilete spores are features consistent with those of the Oliveri Group within Scolecopteris , a group that has previously been considered primitive within this genus. Distinctions from all other previously recognized species within the Oliveri Group lead to the creation of a new species, S. guizhouensis sp. nov. This species is the youngest of the reported species of Scolecopteris recognized from the Euramerican and Cathaysian floras, and provides important evidence on the organization of marattialean ferns from the Upper Permian strata of south China. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 279–288. 相似文献
10.
<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