全文获取类型
收费全文 | 19371篇 |
免费 | 1487篇 |
国内免费 | 1090篇 |
专业分类
21948篇 |
出版年
2024年 | 53篇 |
2023年 | 226篇 |
2022年 | 578篇 |
2021年 | 905篇 |
2020年 | 601篇 |
2019年 | 738篇 |
2018年 | 826篇 |
2017年 | 548篇 |
2016年 | 845篇 |
2015年 | 1153篇 |
2014年 | 1308篇 |
2013年 | 1464篇 |
2012年 | 1766篇 |
2011年 | 1555篇 |
2010年 | 964篇 |
2009年 | 847篇 |
2008年 | 1067篇 |
2007年 | 933篇 |
2006年 | 821篇 |
2005年 | 731篇 |
2004年 | 584篇 |
2003年 | 548篇 |
2002年 | 472篇 |
2001年 | 357篇 |
2000年 | 295篇 |
1999年 | 288篇 |
1998年 | 180篇 |
1997年 | 137篇 |
1996年 | 105篇 |
1995年 | 111篇 |
1994年 | 78篇 |
1993年 | 70篇 |
1992年 | 96篇 |
1991年 | 96篇 |
1990年 | 87篇 |
1989年 | 68篇 |
1988年 | 56篇 |
1987年 | 53篇 |
1986年 | 39篇 |
1985年 | 44篇 |
1984年 | 23篇 |
1983年 | 23篇 |
1982年 | 21篇 |
1981年 | 13篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 19篇 |
1976年 | 15篇 |
1975年 | 14篇 |
1972年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Fibronectin (FN) is the foremost proliferation‐associated extracellular matrix component promoting cell adhesion, migration, and survival. We examined the effect of FN on cell proliferation and the related signaling pathways in mouse embryonic stem (ES) cells. FN increased integrin β1, Src, focal adhesion kinase (FAK), and caveolin‐1 phosphorylation levels in a time‐dependent manner. Phosphorylation of Src, FAK, and caveolin‐1 was attenuated by integrin β1 neutralizing antibody. Integrin β1, Src, and FAK coimmunoprecipitated with caveolin‐1 in the presence of FN. In addition, FN increased RhoA and Rho kinase activation, which were completely blocked by PP2, FAK small interfering RNA (siRNA), caveolin‐1 siRNA, or the caveolar disruptor methyl‐β‐cyclodextrin (MβCD). FN also increased phosphorylation of Akt and ERK 1/2, which were significantly blocked by either FAK siRNA, caveolin‐1 siRNA, MβCD, GGTI‐286 (RhoA inhibitor), or Y‐27632 (Rho kinase inhibitor). FN‐induced increase of protooncogenes (c‐fos, c‐myc, and c‐Jun) and cell‐cycle regulatory proteins (cyclin D1/CDK4 and cyclin E/CDK2) expression levels were attenuated by FAK siRNA or caveolin‐1 siRNA. Furthermore, inhibition of each pathway such as integrin β1, Src, FAK, caveolin‐1, RhoA, Akt, and ERK 1/2 blocked FN‐induced [3H]‐thymidine incorporation. We conclude that FN stimulates mouse ES cell proliferation via RhoA‐PI3K/Akt‐ERK 1/2 pathway through caveolin‐1 phosphorylation. J. Cell. Physiol. 226: 267–275, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
92.
93.
94.
95.
96.
Han Hu Kshitij Khatri Joshua Klein Nancy Leymarie Joseph Zaia 《Glycoconjugate journal》2016,33(3):285-296
Despite the publication of several software tools for analysis of glycopeptide tandem mass spectra, there remains a lack of consensus regarding the most effective and appropriate methods. In part, this reflects problems with applying standard methods for proteomics database searching and false discovery rate calculation. While the analysis of small post-translational modifications (PTMs) may be regarded as an extension of proteomics database searching, glycosylation requires specialized approaches. This is because glycans are large and heterogeneous by nature, causing glycopeptides to exist as multiple glycosylated variants. Thus, the mass of the peptide cannot be calculated directly from that of the intact glycopeptide. In addition, the chemical nature of the glycan strongly influences product ion patterns observed for glycopeptides. As a result, glycopeptidomics requires specialized bioinformatics methods. We summarize the recent progress towards a consensus for effective glycopeptide tandem mass spectrometric analysis. 相似文献
97.
98.
Hawon Lee Dae Haeng Cho Yong Hwan Kim Soo-Jeong Shin Sung Bong Kim Sung Ok Han Jinwon Lee Seung Wook Kim Chulhwan Park 《Biotechnology and Bioprocess Engineering》2011,16(4):755-760
The hydrolysis which converts polysaccharides to the fermentable sugars for yeast’s lingocellulosic ethanol production also
generates byproducts which inhibit the ethanol production. To investigate the extent to which inhibitory compounds affect
yeast’s growth and ethanol production, fermentations by Saccharomyces cerevisiae K35 were investigated in various concentrations of acetic acid, furfural, 5-hydroxymethylfurfural (5-HMF), syringaldehyde,
and coumaric acid. Fermentation in hydrolysates from yellow poplar and waste wood was also studied. After 24 h, S. cerevisiae K35 produced close to theoretically predicted ethanol yields in all the concentrations of acetic acid tested (1 ∼ 10 g/L).
Both furans and phenolics inhibited cell growth and ethanol production. Ethanol yield, however, was unaffected, even at high
concentrations, except in the cases of 5 g/L of syringaldehyde and coumaric acid. Although hydrolysates contain various toxic
compounds, in their presence, S. Cerevisiae K35 consumed close to all the available glucose and yielded more ethanol than theoretically predicted. S. Cerevisiae K35 was demonstrated to have high tolerance to inhibitory compounds and not to need any detoxification for ethanol production
from hydrolysates. 相似文献
99.
Screening and characterization of astaxanthin-hyperproducing mutants of Haematococcus pluvialis 总被引:1,自引:0,他引:1
Haematococcus pluvialis was mutated by UV or ethyl methanesulphonate. Mutants resistant to nicotine, diphenylamine, fluridone or norflurazon were then selected. Several nicotine-resistant mutants showed increased (1.9% to 2.5% vs. 1.2% w/w) astaxanthin production. Mutants maintained high astaxanthin production over 4 months of repeated culture. 相似文献
100.
Ascorbate biosynthesis in Arabidopsis cell suspension culture. 总被引:10,自引:0,他引:10
M W Davey C Gilot G Persiau J Ostergaard Y Han G C Bauw M C Van Montagu 《Plant physiology》1999,121(2):535-543
The biosynthesis of L-ascorbic acid (L-AA) in an Arabidopsis (L.) Heynh. cell suspension culture was studied by quantifying the effects of incubation with a range of potential biosynthetic precursors, analogs, and inhibitors on the intracellular levels of reduced and oxidized forms of L-AA. Our results support the recently published biosynthetic pathway of L-AA from L-galactose (G.L. Wheeler, M.A. Jones, N. Smirnoff [1998] Nature 393: 365-369), but suggest that Arabidopsis cell suspension culture simultaneously contains two other routes leading to L-AA. The possible physiological significance of these alternate routes is discussed. 相似文献