全文获取类型
收费全文 | 82066篇 |
免费 | 572篇 |
国内免费 | 462篇 |
专业分类
化学 | 26972篇 |
晶体学 | 813篇 |
力学 | 6856篇 |
综合类 | 10篇 |
数学 | 32432篇 |
物理学 | 16017篇 |
出版年
2022年 | 57篇 |
2021年 | 63篇 |
2020年 | 80篇 |
2019年 | 73篇 |
2018年 | 10485篇 |
2017年 | 10305篇 |
2016年 | 6166篇 |
2015年 | 948篇 |
2014年 | 440篇 |
2013年 | 557篇 |
2012年 | 4050篇 |
2011年 | 10792篇 |
2010年 | 5806篇 |
2009年 | 6170篇 |
2008年 | 6836篇 |
2007年 | 8981篇 |
2006年 | 461篇 |
2005年 | 1543篇 |
2004年 | 1715篇 |
2003年 | 2127篇 |
2002年 | 1155篇 |
2001年 | 339篇 |
2000年 | 401篇 |
1999年 | 208篇 |
1998年 | 233篇 |
1997年 | 186篇 |
1996年 | 237篇 |
1995年 | 173篇 |
1994年 | 129篇 |
1993年 | 147篇 |
1992年 | 98篇 |
1991年 | 94篇 |
1990年 | 79篇 |
1989年 | 84篇 |
1988年 | 88篇 |
1987年 | 89篇 |
1986年 | 78篇 |
1985年 | 74篇 |
1984年 | 73篇 |
1983年 | 50篇 |
1982年 | 70篇 |
1981年 | 67篇 |
1980年 | 68篇 |
1979年 | 83篇 |
1978年 | 66篇 |
1977年 | 50篇 |
1976年 | 42篇 |
1914年 | 45篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
2.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers. 相似文献
3.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant. 相似文献
4.
5.
Sarah Peluse 《Israel Journal of Mathematics》2018,227(1):379-396
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser. 相似文献
6.
Panpan Li Quanbin Liang Eugene Yau-Hin Hong Chin-Yiu Chan Yat-Hin Cheng Ming-Yi Leung Mei-Yee Chan Kam-Hung Low Hongbin Wu Vivian Wing-Wah Yam 《Chemical science》2020,11(42):11601
A class of acceptor–donor–acceptor chromophoric small-molecule non-fullerene acceptors, 1–4, with difluoroboron(iii) β-diketonate (BF2bdk) as the electron-accepting moiety has been developed. Through the variation of the central donor unit and the modification on the peripheral substituents of the terminal BF2bdk acceptor unit, their photophysical and electrochemical properties have been systematically studied. Taking advantage of their low-lying lowest unoccupied molecular orbital energy levels (from −3.65 to −3.72 eV) and relatively high electron mobility (7.49 × 10−4 cm2 V−1 s−1), these BF2bdk-based compounds have been employed as non-fullerene acceptors in organic solar cells with maximum power conversion efficiencies of up to 4.31%. Moreover, bistable resistive memory characteristics with charge-trapping mechanisms have been demonstrated in these BF2bdk-based compounds. This work not only demonstrates for the first time the use of a boron(iii) β-diketonate unit in constructing non-fullerene acceptors, but also provides more insights into designing organic materials with multi-functional properties.Boron(iii) β-diketonates have been demonstrated to serve as multi-functional materials in NFA-based OPVs and organic resistive memories. 相似文献
7.
8.
9.
10.
Da Hyeon Choi Jiwon Park Ju Kwang Choi Kyeong Eun Lee Won Hee Lee Jinho Yang Ju Yeon Lee Yoon Jeong Park Chan Oh Ho-Ryun Won Bon Seok Koo Jae Won Chang Yoon Shin Park 《Experimental & molecular medicine》2020,52(9):1564
Oral microbes have the capacity to spread throughout the gastrointestinal system and are strongly associated with multiple diseases. Given that tonsils are located between the oral cavity and the laryngopharynx at the gateway of the alimentary and respiratory tracts, tonsillar tissue may also be affected by microbiota from both the oral cavity (saliva) and the alimentary tract. Here, we analyzed the distribution and association of the microbial communities in the saliva and tonsils of Korean children subjected to tonsillectomy because of tonsil hyperplasia (n = 29). The microbiome profiles of saliva and tonsils were established via 16S rRNA gene sequencing. Based on the alpha diversity indices, the microbial communities of the two groups showed high similarities. According to Spearman’s ranking correlation analysis, the distribution of Treponema, the causative bacterium of periodontitis, in saliva and tonsils was found to have a significant positive correlation. Two representative microbes, Prevotella in saliva and Alloprevotella in tonsils, were negatively correlated, while Treponema 2 showed a strong positive correlation between saliva and tonsils. Taken together, strong similarities in the microbial communities of the tonsils and saliva are evident in terms of diversity and composition. The saliva microbiome is expected to significantly affect the tonsil microbiome. Furthermore, we suggest that our study creates an opportunity for tonsillar microbiome research to facilitate the development of novel microbiome-based therapeutic strategies.Subject terms: Comparative genomics, Metagenomics 相似文献