全文获取类型
收费全文 | 1179篇 |
免费 | 53篇 |
专业分类
化学 | 972篇 |
晶体学 | 13篇 |
力学 | 13篇 |
数学 | 27篇 |
物理学 | 207篇 |
出版年
2023年 | 13篇 |
2022年 | 19篇 |
2021年 | 23篇 |
2020年 | 28篇 |
2019年 | 38篇 |
2018年 | 26篇 |
2017年 | 14篇 |
2016年 | 38篇 |
2015年 | 32篇 |
2014年 | 33篇 |
2013年 | 60篇 |
2012年 | 103篇 |
2011年 | 101篇 |
2010年 | 46篇 |
2009年 | 51篇 |
2008年 | 61篇 |
2007年 | 58篇 |
2006年 | 79篇 |
2005年 | 56篇 |
2004年 | 49篇 |
2003年 | 44篇 |
2002年 | 49篇 |
2001年 | 18篇 |
2000年 | 23篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1969年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有1232条查询结果,搜索用时 15 毫秒
991.
Dr. Seiichiro Izawa Kentaro Uchida Mayuko Nakamura Dr. Keisuke Fujimoto Jérémy Roudin Ji-Hyun Lee Dr. Toshiyasu Inuzuka Takumi Nakamura Prof. Dr. Masami Sakamoto Dr. Yasuo Nakayama Prof. Dr. Masahiro Hiramoto Prof. Dr. Masaki Takahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(56):14081-14091
The influence of N-substituents on the photovoltaic properties of singly bay-linked perylene diimides (diPDIs) was systematically investigated to understand the aromatic-aliphatic balance, which is beneficial for achieving high device performance in organic photovoltaic (OPV) systems. The synthesis of various N-substituted diPDIs was successfully achieved using a newly developed one-step procedure, resulting in sufficiently high yields. Detailed investigations of seven variants of diPDIs demonstrated that the primary alkyl substituents, particularly the 2-ethylhexyl group, induce the self-organized growth of thin films with high crystallinity. This is beneficial for enhancing the device performance of bulk heterojunction (BHJ) systems. The results presented herein reveal the important roles of alkyl side chains as hydrophobic solubilizing auxiliaries or primary determinants in the control of the active layer nanomorphology. This offers a valuable guideline that is essential for developing high-performance organic semiconductor materials for future practical applications. 相似文献
992.
Taku Matsuo Hiroshi Nakamura Hiroshi Sakaguchi Kouji Shimomura Isamu Yoshimatsu Keisuke Takuma 《Molecular Crystals and Liquid Crystals》2013,570(2):185-196
Remarkable electric field effects were observed with sensitized fluorescence intensities of a perylene derivative (BPDC), when rectangular AC waves (up to 10 V0-p ) were applied to nematic liquid crystal cells containing a sensitizer (C307 or AHDA) and an acceptor (BPDC) as the guest molecules. Measurements of the fluorescence lifetime of AHDA indicated that the rates of energy transfer from AHDA to BPDC were independent of the electric fields. The electric field effects completely changed the sign when the intensity variation detected at vertical direction was compared with that at the horizontal direction with respect to the liquid crystal cell. The observed electric field effects on the sensitized fluorescence were consequently suggested to come from the orientation control of transition dipole moment of BPDC through the molecular alignment of the liquid crystal. The suggestion was confirmed by the measurement of dichroic absorption of the donor-acceptor systems. 相似文献
993.
Multielectron‐Transfer‐based Rechargeable Energy Storage of Two‐Dimensional Coordination Frameworks with Non‐Innocent Ligands 下载免费PDF全文
Keisuke Wada Dr. Ken Sakaushi Prof. Dr. Sono Sasaki Prof. Dr. Hiroshi Nishihara 《Angewandte Chemie (International ed. in English)》2018,57(29):8886-8890
The metallically conductive bis(diimino)nickel framework (NiDI), an emerging class of metal–organic framework (MOF) analogues consisting of two‐dimensional (2D) coordination networks, was found to have an energy storage principle that uses both cation and anion insertion. This principle gives high energy led by a multielectron transfer reaction: Its specific capacity is one of the highest among MOF‐based cathode materials in rechargeable energy storage devices, with stable cycling performance up to 300 cycles. This mechanism was studied by a wide spectrum of electrochemical techniques combined with density‐functional calculations. This work shows that a rationally designed material system of conductive 2D coordination networks can be promising electrode materials for many types of energy devices. 相似文献
994.
Keisuke Ohdaira Naohito Tomura Shohei Ishii Keisuke Sawada Hideki Matsumura 《Journal of Non》2012,358(17):2154-2158
We investigate the impact of the materials of glass substrates on crack formation during flash lamp annealing (FLA) of 4.5 μm-thick precursor amorphous silicon (a-Si) films for the formation of polycrystalline Si (poly-Si) films. The use of soda lime glass substrates, with the largest thermal expansion coefficient (α) and the lowest glass transition temperature (Tg) in glass materials attempted in this study, results in the serious formation of cracks on and inside the glass substrates. Cracks are also seen on the surface of quartz glass substrates, which have much smaller α and higher Tg, after FLA. Furthermore, flash-lamp-crystallized (FLC) poly-Si films have linearly-connected low-crystallinity regions only when quartz glass substrates are used. These facts indicate that the expansion of Si films induces cracks in quartz glass substrates, while the expansion of the upper part of glass is the cause of the crack formation in glass substrates with large α. The generation of cracks is most significantly suppressed when we use alkali-free glass substrates, with a moderate α and a relatively high Tg, which will contribute to the realization of high-quality poly-Si films and high-performance solar cells. 相似文献
995.
Asymmetric synthesis of (+)-sappanone B (1), a natural product with a 3-hydroxy chromanone structure, was achieved via enantioselective benzoin cyclization by using a modified Rovis catalyst and triethylamine. This catalyst enabled the successful benzoin cyclization of readily enolizable keto-aldehydes. 相似文献
996.
Palladium-catalyzed cyclization-methoxycarbonylation of (2R,3S)-3-methylpenta-4-yne-1,2-diol (6) derived from (2R,3S)-epoxy butanoate 5, followed by methylation, gave the tetrahydro-2-furylidene acetate (-)-7, which was converted to the left-half aldehyde (+)-3. A Wittig reaction between (+)-3 and the phosphoranylide derived from the bithiazole-type phosphonium iodide 4 using lithium bis(trimethylsilyl)amide afforded (+)-cystothiazole B (2), the spectral data of which were identical to those of the natural product (+)-2. Thus the stereochemistry of cystothiazole B (2) was confirmed to be [4R, 5S, 6(E)]. 相似文献
997.
Siloxy amino acid lithium salt, O-tert-butyldiphenylsilyl l-serine lithium salt, was found to be an effective catalyst for the asymmetric Michael addition reaction of malonates to enones. 相似文献
998.
999.
Rikio Settai Keisuke Katayama Tetsuya Takeuchi Ilya Sheikin 《Journal of Physics and Chemistry of Solids》2010,71(4):700-703
We have studied superconducting properties by measuring the electrical resistivity and magnetization for a single crystal of Rh17S15 with a superconducting transition temperature Tc=5.4 K. The upper critical field Hc2(0) and the lower critical field Hc1(0) were obtained as 20.5 and 0.0033 T, respectively. Correspondingly, the coherence length and the penetration depth were estimated to be 40 and 4900 Å, respectively, indicating that Rh17S15 is a typical type-II superconductor with strong correlations of conduction electrons with a 4d-electron character of Rh atoms. The present electron correlations are formed to be enhanced with increasing pressure. 相似文献
1000.
A.B. Couto L.C.D. SantosJ.T. Matsushima M.R. BaldanN.G. Ferreira 《Applied Surface Science》2011,257(23):10141-10146
Copper nanoparticle electrodeposition and consolidation processes were studied on boron doped diamond (BDD) electrode submitted to hydrogen and oxygen plasma treatments. The modified BDD films were applied as electrodes for nitrate electroreduction. The results showed that both treatments have a strong influence on the copper deposition and dissolution processes. For BDD treated with hydrogen plasma the copper electrodeposit was homogeneous with high particle density. This behavior was attributed to the BDD surface hydrogenation that improved its conductivity. On the other hand, the treatment with oxygen plasma was important for the copper nanoparticle consolidation on BDD surface, confirmed by the result's reproducibility for nitrate reduction. This performance may be associated with the formation of oxygen groups that can act as anchor points for Cu-clusters, enhancing the interfacial adhesion between diamond and the metal coating. The best electrochemical nitrate reduction response was obtained in acid media, where occurred the separation of the nitrate reduction process and the water reduction reaction. 相似文献