全文获取类型
收费全文 | 3756篇 |
免费 | 397篇 |
国内免费 | 261篇 |
出版年
2023年 | 29篇 |
2022年 | 29篇 |
2021年 | 134篇 |
2020年 | 100篇 |
2019年 | 148篇 |
2018年 | 145篇 |
2017年 | 121篇 |
2016年 | 164篇 |
2015年 | 265篇 |
2014年 | 275篇 |
2013年 | 293篇 |
2012年 | 367篇 |
2011年 | 320篇 |
2010年 | 211篇 |
2009年 | 189篇 |
2008年 | 230篇 |
2007年 | 203篇 |
2006年 | 162篇 |
2005年 | 140篇 |
2004年 | 140篇 |
2003年 | 127篇 |
2002年 | 116篇 |
2001年 | 66篇 |
2000年 | 52篇 |
1999年 | 52篇 |
1998年 | 25篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 16篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 22篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 16篇 |
1985年 | 6篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1970年 | 3篇 |
排序方式: 共有4414条查询结果,搜索用时 15 毫秒
1.
2.
Dong-Hui Xu Guo-Nan Chi Cong-Hai Zhao Dong-Yuan Li 《Journal of cellular biochemistry》2019,120(5):7516-7526
Glioma is a common primary brain tumor with high mortality rate and poor prognosis. Long noncoding RNA maternally expressed gene 3 (MEG3) is a tumor suppressor in diverse cancer types. However, the role of MEG3 in glioma remains unclear. We aimed to explore the effects of MEG3 on U251 cells as well as the underlying mechanisms. U251 cells were stably transfected with different recombined plasmids to overexpress or silence MEG3. Effects of aberrantly expressed MEG3 on cell viability, migration, apoptosis, expressions of apoptosis-associated and autophagy-associated proteins, and phosphorylated levels of key kinases in the PI3K/AKT/mTOR pathway were all evaluated. Then, messenger RNA (mRNA) and protein expression of Sirt7 in cells abnormally expressing MEG3 were estimated. In addition, effects of abnormally expressed MEG3 and Sirt7 on U251 cells were determined to reveal the underlying mechanism of MEG3-associated modulation. Cell viability and migration were significantly reduced by MEG3 overexpression whereas cell apoptosis as well as Bax and cleaved caspase-3/-9 proteins were obviously induced. Beclin-1 and LC3-II/LC3-I were upregulated and p62 was downregulated in MEG3 overexpressed cells. In addition, the autophagy pharmacological inhibitor (3-methyladenine, 3-MA) affected the effect of MEG3 overexpression on cell proliferation. Furthermore, the phosphorylated levels of key kinases in the PI3K/AKT/mTOR pathway were all reduced by MEG3 overexpression. Sirt7 was positively regulated by MEG3 expression, and effects of MEG3 overexpression on U251 cells were ameliorated by Sirt7 silence. MEG3 suppressed cell proliferation and migration but promoted autophagy in U251 cells through positively regulating Sirt7, involving in the inhibition of the PI3K/AKT/mTOR pathway. 相似文献
3.
Irene Jao Vicki Marsh Primus Che Chi Melissa Kapulu Mainga Hamaluba Sassy Molyneux Philip Bejon Dorcas Kamuya 《Bioethics》2020,34(8):819-832
Controlled human malaria infection (CHMI) studies involve the deliberate infection of healthy volunteers with malaria parasites under controlled conditions to study immune responses and/or test drug or vaccine efficacy. An empirical ethics study was embedded in a CHMI study at a Kenyan research programme to explore stakeholders’ perceptions and experiences of deliberate infection and moral implications of these. Data for this qualitative study were collected through focus group discussions, in-depth interviews and non-participant observation. Sixty-nine participants were involved, including CHMI study volunteers, community representatives and research staff. Data were managed using QSR Nvivo 10 and analysed using an inductive-deductive approach, guided by ethics literature. CHMI volunteers had reasonable understanding of the study procedures. Decisions to join were influenced by study incentives, trust in the research institution, their assessment of associated burdens and motivation to support malaria vaccine development. However, deliberate malaria infection was a highly unusual research strategy for volunteers, community representatives and some study staff. Volunteers’ experiences of physical, emotional and social burdens or harms were often greater than anticipated initially, and fluctuated over time, related to specific procedures and events. Although unlikely to deter volunteers' participation in similar studies in furture, we argue that the dissonance between level of understanding of the burdens involved and actual experiences are morally relevant in relation to community engagement, informed consent processes, and ongoing support for volunteers and research staff. We further argue that ethics oversight of CHMI studies should take account of these issues in deciding whether consent, engagement and the balance of benefits and harms are reasonable in a given context. 相似文献
4.
Two Saccharomyces cerevisiae strains with different degrees of ethanol tolerance adapted differently to produced ethanol. Adaptation in the less ethanol-tolerant
strain was high and resulted in a reduced formation of ethanol-induced respiratory deficient mutants and an increased ergosterol
content of the cells. Adaptation in the more ethanol-tolerant strain was less pronounced. Journal of Industrial Microbiology & Biotechnology (2000) 24, 75–78.
Received 22 June 1999/ Accepted in revised form 06 October 1999 相似文献
5.
6.
7.
8.
9.
10.