全文获取类型
收费全文 | 22628篇 |
免费 | 1618篇 |
国内免费 | 1639篇 |
出版年
2024年 | 55篇 |
2023年 | 403篇 |
2022年 | 556篇 |
2021年 | 727篇 |
2020年 | 715篇 |
2019年 | 1053篇 |
2018年 | 909篇 |
2017年 | 612篇 |
2016年 | 637篇 |
2015年 | 795篇 |
2014年 | 1463篇 |
2013年 | 1752篇 |
2012年 | 1079篇 |
2011年 | 1515篇 |
2010年 | 1147篇 |
2009年 | 1194篇 |
2008年 | 1208篇 |
2007年 | 1213篇 |
2006年 | 1036篇 |
2005年 | 954篇 |
2004年 | 792篇 |
2003年 | 690篇 |
2002年 | 616篇 |
2001年 | 430篇 |
2000年 | 386篇 |
1999年 | 343篇 |
1998年 | 315篇 |
1997年 | 262篇 |
1996年 | 241篇 |
1995年 | 214篇 |
1994年 | 233篇 |
1993年 | 184篇 |
1992年 | 196篇 |
1991年 | 181篇 |
1990年 | 146篇 |
1989年 | 124篇 |
1988年 | 105篇 |
1987年 | 118篇 |
1986年 | 98篇 |
1985年 | 158篇 |
1984年 | 154篇 |
1983年 | 120篇 |
1982年 | 122篇 |
1981年 | 130篇 |
1980年 | 113篇 |
1979年 | 90篇 |
1978年 | 73篇 |
1977年 | 54篇 |
1976年 | 62篇 |
1974年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
851.
852.
Breast cancer cells develop resistance to endocrine therapies by shifting between estrogen receptor (ER)-regulated and growth factor receptor (GFR)-regulated survival signaling pathways. To study this switch, we propose a mathematical model of crosstalk between these pathways. The model explains why MCF7 sub-clones transfected with HER2 or EGFR show three GFR-distribution patterns, and why the bimodal distribution pattern can be reversibly modulated by estrogen. The model illustrates how transient overexpression of ER activates GFR signaling and promotes estrogen-independent growth. Understanding this survival-signaling switch can help in the design of future therapies to overcome resistance in breast cancer. 相似文献
853.
854.
Christian Berger Sandra Berndt Annelie Pichert Stephan Theisgen Daniel Huster 《Biotechnology and bioengineering》2013,110(6):1681-1690
A protocol for the efficient isotopic labeling of large G protein‐coupled receptors with tryptophan in Escherichia coli as expression host was developed that sufficiently suppressed the naturally occurring L‐tryptophan indole lyase, which cleaves tryptophan into indole, pyruvate, and ammonia resulting in scrambling of the isotopic label in the protein. Indole produced by the tryptophanase is naturally used as messenger for cell–cell communication. Detailed analysis of different process conducts led to the optimal expression strategy, which mimicked cell–cell communication by the addition of indole during expression. Discrete concentrations of indole and 15N2‐L‐tryptophan at dedicated time points in the fermentation drastically increased the isotopic labeling efficiency. Isotope scrambling was only observed in glutamine, asparagine, and arginine side chains but not in the backbone. This strategy allows producing specifically tryptophan labeled membrane proteins at high concentrations avoiding the disadvantages of the often low yields of auxotrophic E. coli strains. In the fermentation process carried out according to this protocol, we produced ~15 mg of tryptophan labeled neuropeptide Y receptor type 2 per liter medium. Biotechnol. Bioeng. 2013; 110: 1681–1690. © 2013 Wiley Periodicals, Inc. 相似文献
855.
Liping Zhang Hong Zhang Yining Zhao Zhe Li Shangke Chen Jing Zhai Yunyun Chen Wei Xie Zhong Wang Qing Li Xuehua Zheng Xiaopeng Hu 《FEBS letters》2013
The antineoplastic target aldo–keto reductase family member 1B10 (AKR1B10) and the critical polyol pathway enzyme aldose reductase (AKR1B1) share high structural similarity. Crystal structures reported here reveal a surprising Trp112 native conformation stabilized by a specific Gln114-centered hydrogen bond network in the AKR1B10 holoenzyme, and suggest that AKR1B1 inhibitors could retain their binding affinities toward AKR1B10 by inducing Trp112 flip to result in an “AKR1B1-like” active site in AKR1B10, while selective AKR1B10 inhibitors can take advantage of the broader active site of AKR1B10 provided by the native Trp112 side-chain orientation. 相似文献
856.
Avery L. McIntosh Anca D. Petrescu Heather A. Hostetler Ann B. Kier Friedhelm Schroeder 《FEBS letters》2013
Hepatocyte nuclear factor 4α (HNF4α) regulates liver type fatty acid binding protein (L-FABP) gene expression. Conversely as shown herein, L-FABP structurally and functionally also interacts with HNF4α. Fluorescence resonance energy transfer (FRET) between Cy3-HNF4α (donor) and Cy5-L-FABP (acceptor) as well as FRET microscopy detected L-FABP in close proximity (∼80 Å) to HNF4α, binding with high affinity Kd ∼250–300 nM. Circular dichroism (CD) determined that the HNF4α/L-FABP interaction altered protein secondary structure. Finally, L-FABP potentiated transactivation of HNF4α in COS7 cells. Taken together, these data suggest that L-FABP provides a signaling path to HNF4α activation in the nucleus. 相似文献
857.
Can-Jie Guo Qin Pan Hua Xiong Yu-Qi Qiao Zhao-Lian Bian Wei Zhong Li Sheng Hai Li Lei Shen Jing Hua Xiong Ma Jing-Yuan Fang 《FEBS letters》2013
In our previous study, miR-126 was identified as one of the leading miRNAs that is downregulated during activation of hepatic stellate cells (HSCs). However, the roles and related mechanisms of miR-126 in HSCs are not understood. In this study, we compared expression of miR-126 during HSC activation both in vitro and in vivo. We also applied RNA interference to analyze the role and mechanism of miR-126∗ in the activation of HSCs. Restoring HSCs with Lv-miR-126∗ resulted in decreased proliferation, accumulation of extracellular matrix components, and cell contraction, while also negatively regulating the vascular endothelial growth factor (VEGF) signal transduction pathways by partially targeted VEGF-A. Thus, we postulate that miR-126 may be a biological marker for the activation of HSCs, and useful for reducing intrahepatic vascular resistance and improving the sinusoidal microcirculation in chronic liver diseases. 相似文献
858.
【目的】探讨新城疫病毒(Newcastle disease virus,NDV)基质(matrix,M)蛋白和禽细胞核磷蛋白B23.1在HEK-293T细胞中的相互作用。【方法】分别参照GenBank中NDV JS/5/05/Go株全基因序列(JN631747)和禽细胞核磷蛋白B23.1基因序列(NM205267),设计、合成扩增M基因和B23.1基因的引物,利用RT-PCR扩增出M基因和DF1细胞的B23.1基因,分别克隆至真核表达载体获得重组表达质粒pEGFP-M、pCMV-HA-M和pDsRed-B23.1;将pEGFP-M和pDsRed-B23.1共转染HEK-293T细胞,利用荧光显微镜观察M蛋白与B23.1蛋白的共定位;利用免疫共沉淀(Co-IP)技术进一步验证两种蛋白的相互作用。【结果】Western blot结果表明构建的重组质粒在转染的HEK-293T细胞中正确表达;荧光显微镜观察显示M蛋白与B23.1蛋白在核仁具有共定位特征;Co-IP进一步证实两者能发生相互作用。【结论】NDV M蛋白与禽细胞核磷蛋白B23.1存在相互作用,M蛋白可能通过与B23.1蛋白的相互作用进入核仁。 相似文献
859.
860.
Identification of a new membrane-permeable inhibitor against inositol-1,4,5-trisphosphate-3-kinase A
Dominik Schröder Christoph Rehbach Carola Seyffarth Martin Neuenschwander Jens V. Kries Sabine Windhorst 《Biochemical and biophysical research communications》2013
Ectopic expression of the neuron-specific inositol-1,4,5-trisphosphate-3-kinase A (ITPKA) in lung cancer cells increases their metastatic potential because the protein exhibits two actin regulating activities; it bundles actin filaments and regulates inositol-1,4,5-trisphosphate (InsP3)-mediated calcium signals by phosphorylating InsP3. Thus, in order to inhibit the metastasis-promoting activity of ITPKA, both its actin bundling and its InsP3kinase activity has to be blocked. In this study, we performed a high throughput screen in order to identify specific and membrane-permeable substances against the InsP3kinase activity. Among 341,44 small molecules, 237 compounds (0.7%) were identified as potential InsP3kinase inhibitors. After determination of IC50-values, the three compounds with highest specificity and highest hydrophobicity (EPPC-3, BAMB-4, MEPTT-3) were further characterized. Only BAMB-4 was nearly completely taken up by H1299 cells and remained stable after cellular uptake, thus exhibiting a robust stability and a high membrane permeability. Determination of the inhibitor type revealed that BAMB-4 belongs to the group of mixed type inhibitors. Taken together, for the first time we identified a highly membrane-permeable inhibitor against the InsP3kinase activity of ITPKA providing the possibility to partly inhibit the metastasis-promoting effect of ITPKA in lung tumor cells. 相似文献