全文获取类型
收费全文 | 56381篇 |
免费 | 4857篇 |
国内免费 | 4948篇 |
专业分类
化学 | 20981篇 |
晶体学 | 222篇 |
力学 | 3999篇 |
综合类 | 1202篇 |
数学 | 24126篇 |
物理学 | 15656篇 |
出版年
2023年 | 435篇 |
2022年 | 685篇 |
2021年 | 1640篇 |
2020年 | 1242篇 |
2019年 | 1397篇 |
2018年 | 1161篇 |
2017年 | 1316篇 |
2016年 | 1626篇 |
2015年 | 1518篇 |
2014年 | 2363篇 |
2013年 | 4008篇 |
2012年 | 2655篇 |
2011年 | 3149篇 |
2010年 | 2897篇 |
2009年 | 3641篇 |
2008年 | 3688篇 |
2007年 | 3986篇 |
2006年 | 3235篇 |
2005年 | 2578篇 |
2004年 | 2257篇 |
2003年 | 2135篇 |
2002年 | 1968篇 |
2001年 | 1845篇 |
2000年 | 1426篇 |
1999年 | 1199篇 |
1998年 | 1101篇 |
1997年 | 917篇 |
1996年 | 883篇 |
1995年 | 774篇 |
1994年 | 726篇 |
1993年 | 680篇 |
1992年 | 653篇 |
1991年 | 462篇 |
1990年 | 411篇 |
1989年 | 308篇 |
1988年 | 335篇 |
1987年 | 287篇 |
1986年 | 285篇 |
1985年 | 413篇 |
1984年 | 316篇 |
1983年 | 193篇 |
1982年 | 367篇 |
1981年 | 531篇 |
1980年 | 470篇 |
1979年 | 511篇 |
1978年 | 408篇 |
1977年 | 308篇 |
1976年 | 270篇 |
1974年 | 85篇 |
1973年 | 175篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
22.
23.
24.
25.
Chengwei Deng 《中国物理 B》2022,31(11):118702-118702
RNAs play crucial and versatile roles in cellular biochemical reactions. Since experimental approaches of determining their three-dimensional (3D) structures are costly and less efficient, it is greatly advantageous to develop computational methods to predict RNA 3D structures. For these methods, designing a model or scoring function for structure quality assessment is an essential step but this step poses challenges. In this study, we designed and trained a deep learning model to tackle this problem. The model was based on a graph convolutional network (GCN) and named RNAGCN. The model provided a natural way of representing RNA structures, avoided complex algorithms to preserve atomic rotational equivalence, and was capable of extracting features automatically out of structural patterns. Testing results on two datasets convincingly demonstrated that RNAGCN performs similarly to or better than four leading scoring functions. Our approach provides an alternative way of RNA tertiary structure assessment and may facilitate RNA structure predictions. RNAGCN can be downloaded from https://gitee.com/dcw-RNAGCN/rnagcn. 相似文献
26.
《Arabian Journal of Chemistry》2022,15(10):104145
In the present study, novel representatives of the important group of biologically-active, dehydroabietic acid-bearing dithiocarbamate moiety, were synthesized and characterized by 1H NMR, 13C NMR, HR-MS. The in vitro antiproliferative activity evaluation (MTT) indicated that these compounds exhibited potent inhibitory activities in various cancer cell lines (HepG-2, MCF-7, HeLa, T-24, MGC-803). Particularly, compound III-b possessed extraordinary cytotoxicity with low micromolar IC50 values ranging from 4.07 to 38.84 µM against tested cancer cell lines, while displayed weak cytotoxicity on two normal cell lines (LO-2 and HEK 293 T). Subsequently, the potential mechanisms of representative compound III-b were elementarily investigated by Transwell experiment, which showed III-b can inhibit cancer cells migration. Annexin-V/PI dual staining showed that the compound can induce HepG-2 cells apoptosis in a dose-dependent manner. Meanwhile this apoptosis may be related to the upregulated protein expression of cleaved-caspase 3, cleaved-caspase 9, Bax and downregulated of Bcl-2 indicated by Western Blot. Later study further confirmed that ROS levels in HepG-2 cells increased significantly with the rise of concentrations. In addition, through the network pharmacology data analyzing, the core targets and signaling pathways of compound III-b for treatment of liver neoplasms were forecasted. Molecular docking model showed that compound III-b had high affinity with hub targets (CASP3, EGFR, HSP90AA1, MAPK1, ERBB2, MDM2), suggesting that compound III-b might target the hub protein to modulate signaling activity. Taken together, these data indicated that dehydroabietic acid structural modification following the “Molecular hybridization” principle is a feasible way to discover the potential multi-targeted antitumor compounds. 相似文献
27.
28.
29.
30.