全文获取类型
收费全文 | 1320篇 |
免费 | 36篇 |
国内免费 | 6篇 |
专业分类
化学 | 703篇 |
晶体学 | 5篇 |
力学 | 85篇 |
数学 | 301篇 |
物理学 | 268篇 |
出版年
2023年 | 12篇 |
2022年 | 7篇 |
2021年 | 26篇 |
2020年 | 26篇 |
2019年 | 30篇 |
2018年 | 21篇 |
2017年 | 24篇 |
2016年 | 64篇 |
2015年 | 41篇 |
2014年 | 48篇 |
2013年 | 80篇 |
2012年 | 103篇 |
2011年 | 115篇 |
2010年 | 69篇 |
2009年 | 57篇 |
2008年 | 80篇 |
2007年 | 86篇 |
2006年 | 54篇 |
2005年 | 52篇 |
2004年 | 46篇 |
2003年 | 51篇 |
2002年 | 27篇 |
2001年 | 21篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 24篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有1362条查询结果,搜索用时 15 毫秒
1.
Particularly-shaped silver nanostructures are successfully applied in many scientific fields, such as nanotechnology, catalysis, (nano)engineering, optoelectronics, and sensing. In recent years, the production of shape-controlled silver-based nanostructures and the knowledge around this topic has grown significantly. Hence, on the basis of the most recent results reported in the literature, a critical analysis around the driving forces behind the synthesis of such nanostructures are proposed herein, pointing out the important role of surface-regulating agents in driving crystalline growth by favoring (or opposing) development along specific directions. Additionally, growth mechanisms of the different morphologies considered here are discussed in depth, and critical points highlighted. 相似文献
2.
3.
4.
5.
Francesca Al Francesca Miraglia Alessandro Orticoni Elda Judica Maria Cotelli Paolo Maria Rossini Fabrizio Vecchio 《Entropy (Basel, Switzerland)》2020,22(11)
Human brain, a dynamic complex system, can be studied with different approaches, including linear and nonlinear ones. One of the nonlinear approaches widely used in electroencephalographic (EEG) analyses is the entropy, the measurement of disorder in a system. The present study investigates brain networks applying approximate entropy (ApEn) measure for assessing the hemispheric EEG differences; reproducibility and stability of ApEn data across separate recording sessions were evaluated. Twenty healthy adult volunteers were submitted to eyes-closed resting EEG recordings, for 80 recordings. Significant differences in the occipital region, with higher values of entropy in the left hemisphere than in the right one, show that the hemispheres become active with different intensities according to the performed function. Besides, the present methodology proved to be reproducible and stable, when carried out on relatively brief EEG epochs but also at a 1-week distance in a group of 36 subjects. Nonlinear approaches represent an interesting probe to study the dynamics of brain networks. ApEn technique might provide more insight into the pathophysiological processes underlying age-related brain disconnection as well as for monitoring the impact of pharmacological and rehabilitation treatments. 相似文献
6.
7.
Dr. Mojtaba Alidoost Anna Mangini Dr. Fabrizio Caldera Dr. Anastasia Anceschi Dr. Julia Amici Dr. Daniele Versaci Dr. Lucia Fagiolari Prof. Francesco Trotta Prof. Carlotta Francia Prof. Federico Bella Prof. Silvia Bodoardo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(6):e202104201
Manufactured globally on industrial scale, cyclodextrins (CD) are cyclic oligosaccharides produced by enzymatic conversion of starch. Their typical structure of truncated cone can host a wide variety of guest molecules to create inclusion complexes; indeed, we daily use CD as unseen components of food, cosmetics, textiles and pharmaceutical excipients. The synthesis of active material composites from CD resources can enable or enlarge the effective utilization of these products in the battery industry with some economical as well as environmental benefits. New and simple strategies are here presented for the synthesis of nanostructured silicon and sulfur composite materials with carbonized hyper cross-linked CD (nanosponges) that show satisfactory performance as high-capacity electrodes. For the sulfur cathode, the mesoporous carbon host limits polysulfide dissolution and shuttle effects and guarantees stable cycling performance. The embedding of silicon nanoparticles into the carbonized nanosponge allows to achieve high capacity and excellent cycling performance. Moreover, due to the high surface area of the silicon composite, the characteristics at the electrode/electrolyte interface dominate the overall electrochemical reversibility, opening a detailed analysis on the behavior of the material in different electrolytes. We show that the use of commercial LP30 electrolyte causes a larger capacity fade, and this is associated with different solid electrolyte interface layer formation and it is also demonstrated that fluoroethylene carbonate addition can significantly increase the capacity retention and the overall performance of our nanostructured Si/C composite in both ether-based and LP30 electrolytes. As a result, an integration of the Si/C and S/C composites is proposed to achieve a complete lithiated Si−S cell. 相似文献
8.
9.
Dr. Juan P. Mora-Fuentes Marcos D. Codesal Marco Reale Dr. Carlos M. Cruz Dr. Vicente G. Jiménez Dr. Alice Sciortino Prof. Marco Cannas Prof. Fabrizio Messina Dr. Victor Blanco Dr. Araceli G. Campaña 《Angewandte Chemie (International ed. in English)》2023,62(21):e202301356
We report the synthesis and characterization of a novel type of nanohoop, consisting of a cycloparaphenylene derivative incorporating a curved heptagon-containing π-extended polycyclic aromatic hydrocarbon (PAH) unit. We demonstrate that this new macrocycle behaves as a supramolecular receptor of curved π-systems such as fullerenes C60 and C70, with remarkably large binding constants (ca. 107 M−1), as estimated by fluorescence measurements. Nanosecond and femtosecond spectroscopic analysis show that these host-guest complexes are capable of quasi-instantaneous charge separation upon photoexcitation, due to the ultrafast charge transfer from the macrocycle to the complexed fullerene. These results demonstrate saddle-shaped PAHs with dibenzocycloheptatrienone motifs as structural components for new macrocycles displaying molecular receptor abilities and versatile photochemical responses with promising electron-donor properties in host-guest complexes. 相似文献
10.
Dr. Maximilian Muhr Hao Liang Dr. Lars Allmendinger Raphael Bühler Fabrizio E. Napoli Dr. Dardan Ukaj Dr. Mirza Cokoja Dr. Christian Jandl Dr. Samia Kahlal Prof. Dr. Jean-Yves Saillard Dr. Christian Gemel Prof. Dr. Roland A. Fischer 《Angewandte Chemie (International ed. in English)》2023,62(36):e202308790
The bimetallic, decanuclear Ni3Ga7-cluster of the formula [Ni3(GaTMP)3(μ2-GaTMP)3(μ3-GaTMP)] ( 1 , TMP=2,2,6,6-tetramethylpiperidinyl) reacts reversibly with dihydrogen under the formation of a series of (poly-)hydride clusters 2 . Low-temperature 2D NMR experiments at −80 °C show that 2 consist of a mixture of a di- ( 2Di ), tetra- ( 2Tetra ) and hexahydride species ( 2Hexa ). The structures of 2Di and 2Tetra are assessed by a combination of 2D NMR spectroscopy and DFT calculations. The cooperation of both metals is essential for the high hydrogen uptake of the cluster. Polyhydrides 2 are catalytically active in the semihydrogenation of 4-octyne to 4-octene with good selectivity. The example is the first of its kind and conceptually relates properties of molecular, atom-precise transition metal/main group metal clusters to the respective solid-state phase in catalysis. 相似文献