全文获取类型
收费全文 | 19824篇 |
免费 | 2465篇 |
国内免费 | 3篇 |
出版年
2022年 | 161篇 |
2021年 | 339篇 |
2020年 | 157篇 |
2019年 | 222篇 |
2018年 | 275篇 |
2017年 | 259篇 |
2016年 | 448篇 |
2015年 | 685篇 |
2014年 | 772篇 |
2013年 | 912篇 |
2012年 | 1306篇 |
2011年 | 1260篇 |
2010年 | 796篇 |
2009年 | 738篇 |
2008年 | 1048篇 |
2007年 | 1084篇 |
2006年 | 924篇 |
2005年 | 954篇 |
2004年 | 934篇 |
2003年 | 860篇 |
2002年 | 841篇 |
2001年 | 415篇 |
2000年 | 392篇 |
1999年 | 345篇 |
1998年 | 271篇 |
1997年 | 212篇 |
1996年 | 195篇 |
1995年 | 211篇 |
1994年 | 208篇 |
1993年 | 203篇 |
1992年 | 273篇 |
1991年 | 249篇 |
1990年 | 269篇 |
1989年 | 302篇 |
1988年 | 394篇 |
1987年 | 242篇 |
1986年 | 190篇 |
1985年 | 199篇 |
1984年 | 178篇 |
1983年 | 179篇 |
1982年 | 151篇 |
1981年 | 134篇 |
1980年 | 148篇 |
1979年 | 138篇 |
1978年 | 142篇 |
1977年 | 149篇 |
1976年 | 104篇 |
1975年 | 105篇 |
1974年 | 118篇 |
1973年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
Tristan J. Iseli Nigel Turner Xiao-Yi Zeng Gregory J. Cooney Edward W. Kraegen Sheng Yao Yang Ye David E. James Ji-Ming Ye 《PloS one》2013,8(4)
We recently showed that bitter melon-derived triterpenoids (BMTs) activate AMPK and increase GLUT4 translocation to the plasma membrane in vitro, and improve glucose disposal in insulin resistant models in vivo. Here we interrogated the mechanism by which these novel compounds activate AMPK, a leading anti-diabetic drug target. BMTs did not activate AMPK directly in an allosteric manner as AMP or the Abbott compound (A-769662) does, nor did they activate AMPK by inhibiting cellular respiration like many commonly used anti-diabetic medications. BMTs increased AMPK activity in both L6 myotubes and LKB1-deficient HeLa cells by 20–35%. Incubation with the CaMKKβ inhibitor, STO-609, completely attenuated this effect suggesting a key role for CaMKKβ in this activation. Incubation of L6 myotubes with the calcium chelator EGTA-AM did not alter this activation suggesting that the BMT-dependent activation was Ca2+-independent. We therefore propose that CaMKKβ is a key upstream kinase for BMT-induced activation of AMPK. 相似文献
62.
Jason C. White 《Arts Education Policy Review》2016,117(1):55-64
While there are many educational and experiential benefits to attending professional higher arts education programs, students who incur excessive student loan debt during their studies may experience unanticipated or poor professional outcomes either over the course of their artistic careers, shortly after the expiration of a loan grace period, or after they can no longer defer payments. To date, little to no research exists on the effects of an excessive student loan debt burden on professional arts careers. To address this gap in the higher arts education literature, and in an effort to facilitate scholarly discussion on the topic, this article identifies concerns, consequences, and potential interventions. 相似文献
63.
64.
65.
66.
67.
Carbonmonoxyhemoglobin prepared from protein isolated from rabbits maintained on a diet supplemented with 4-fluorophenylalanine (Phe (4F)) has been studied by fluorine NMR spectroscopy. Substitution of Phe(4F) appears to take place randomly at the sixteen nonequivalent phenylalanine positions of the globins; examination of hybrid hemoglobins in which only one type of globin chain contained the fluorinated amino acid, as well as changes in the spectrum upon exposure to oxygen, aided in the assignment of fluorine resonances from the alpha- or beta-globin chains. The effects of modification of Cys-beta-93 with a spin label and variation of pH and sample temperature on the spectrum were also examined. These data in association with theoretical estimates of aromatic ring current and van der Waals effects on chemical shifts were used to support tentative assignments of several signals observed to specific amino acid residues. Evidence suggesting the presence of two conformational forms of the protein, possibly due to disorder of the heme groups, is described. 相似文献
68.
69.
70.
P. White 《BMJ (Clinical research ed.)》1989,298(6682):1199-1200