全文获取类型
收费全文 | 1215篇 |
免费 | 37篇 |
国内免费 | 5篇 |
专业分类
化学 | 897篇 |
晶体学 | 16篇 |
力学 | 13篇 |
数学 | 78篇 |
物理学 | 253篇 |
出版年
2023年 | 8篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 13篇 |
2019年 | 22篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 26篇 |
2015年 | 16篇 |
2014年 | 28篇 |
2013年 | 59篇 |
2012年 | 50篇 |
2011年 | 65篇 |
2010年 | 30篇 |
2009年 | 36篇 |
2008年 | 55篇 |
2007年 | 76篇 |
2006年 | 84篇 |
2005年 | 76篇 |
2004年 | 46篇 |
2003年 | 48篇 |
2002年 | 45篇 |
2001年 | 25篇 |
2000年 | 25篇 |
1999年 | 20篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 25篇 |
1991年 | 10篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 16篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1979年 | 16篇 |
1978年 | 21篇 |
1977年 | 19篇 |
1976年 | 7篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1970年 | 5篇 |
1967年 | 5篇 |
排序方式: 共有1257条查询结果,搜索用时 31 毫秒
991.
Chenting Yan Masato Takeshita Jun-ya Nakatsuji Akihiro Kurosaki Kaoko Sato Rong Shang Masaaki Nakamoto Yohsuke Yamamoto Yohei Adachi Ko Furukawa Ryohei Kishi Masayoshi Nakano 《Chemical science》2020,11(19):5082
Isolation and structural characterization of hypervalent electron-rich pentacoordinate nitrogen species have not been achieved despite continuous attempts for over a century. Herein we report the first synthesis and isolation of air stable hypervalent electron-rich pentacoordinate nitrogen cationic radical (11-N-5) species from oxidation of their corresponding neutral (12-N-5) species. In the cationic radical species, the nitrogen centers adopt a trigonal bipyramidal geometry featuring a 3-center-5-electron hypervalent attractive interaction. The combination of single crystal X-ray diffraction analysis and computational studies revealed weak N–O interactions between the central nitrogen cation and oxygen atoms. This successful design strategy and isolation of air-stable pentacoordinate hypervalent nitrogen species allow further investigations on reactivity and properties resulting from these unusually weakly coordinating interactions in nitrogen compounds.Structural characterization of hypervalent electron-rich pentacoordinate nitrogen species has long been a synthetic challenge. Here we report the first nitrogen cationic radical (11-N-5) species featuring a weak hypervalent 3c-5e interaction. 相似文献
992.
993.
Toi K Watanabe F Tokuzawa T Ida K Morita S Ido T Shimizu A Isobe M Ogawa K Spong DA Todo Y Watari T Ohdachi S Sakakibara S Yamamoto S Inagaki S Narihara K Osakabe M Nagaoka K Narushima Y Watanabe KY Funaba H Goto M Ikeda K Ito T Kaneko O Kubo S Murakami S Minami T Miyazawa J Nagayama Y Nishiura M Oka Y Sakamoto R Shimozuma T Takeiri Y Tanaka K Tsumori K Yamada I Yoshinuma M Kawahata K Komori A;LHD Experiment Group 《Physical review letters》2010,105(14):145003
Reversed-shear Alfvén eigenmodes were observed for the first time in a helical plasma having negative q?' (the curvature of the safety factor q at the zero shear layer). The frequency is swept downward and upward sequentially via the time variation in the maximum of q. The eigenmodes calculated by ideal MHD theory are consistent with the experimental data. The frequency sweeping is mainly determined by the effects of energetic ions and the bulk pressure gradient. Coupling of reversed-shear Alfvén eigenmodes with energetic ion driven geodesic acoustic modes generates a multitude of frequency-sweeping modes. 相似文献
994.
T. Nakamura R. Kita O. Miura A. Ichinose K. Yamada K. Kaneko 《Physica C: Superconductivity and its Applications》2010,470(20):1249-1252
We have prepared Sm0.33Eu0.33Gd0.33Ba2Cu3Oy (SEGBCO) films on LaAlO3 single-crystal substrates by metal-organic deposition using 2-ethylhexanate solutions which contain no fluorine. The SEGBCO film fired at 850 °C under a low oxygen partial pressure of 2 × 10−6 atm exhibited strong c-axis oriented X-ray diffraction peaks and weak a/b-axis oriented peaks of the SEGBCO phase, and had a granular surface. High resolution cross-sectional transmission electron microscope images indicated the epitaxial growth of the SEGBCO film on the substrate with overgrowth of a/b-axis oriented grains. The critical temperature and critical current density values of the SEGBCO film was 86.5 K and 1.29 MA/cm2, respectively, at 77.3 K at the self-field. 相似文献
995.
Pallop Huabsomboon Hideaki Kaneko 《Journal of Computational and Applied Mathematics》2010,234(5):1466-1472
In this paper, we comment on the recent papers by Yuhe Ren et al. (1999) [1] and Maleknejad et al. (2006) [7] concerning the use of the Taylor series to approximate a solution of the Fredholm integral equation of the second kind as well as a solution of a system of Fredholm equations. The technique presented in Yuhe Ren et al. (1999) [1] takes advantage of a rapidly decaying convolution kernel k(|s−t|) as |s−t| increases. However, it does not apply to equations having other types of kernels. We present in this paper a more general Taylor expansion method which can be applied to approximate a solution of the Fredholm equation having a smooth kernel. Also, it is shown that when the new method is applied to the Fredholm equation with a rapidly decaying kernel, it provides more accurate results than the method in Yuhe Ren et al. (1999) [1]. We also discuss an application of the new Taylor-series method to a system of Fredholm integral equations of the second kind. 相似文献
996.
Masahito Tanaka Kazutoshi Yagi‐Watanabe Fusae Kaneko Kazumichi Nakagawa 《Journal of synchrotron radiation》2009,16(4):455-462
Natural circular dichroism (CD) spectra in the extreme ultraviolet (EUV) region down to a wavelength of 80 nm have been observed for the first time, using an alanine thin film deposited on sodium salicylate coated glass as a sample. Calibrated EUV‐CD spectra of l ‐alanine exhibited a large negative peak at around 120 nm and a positive CD signal below 90 nm, which were roughly predicted by theoretical calculations. A CD measurement system with an Onuki‐type polarizing undulator was used to obtain the EUV‐CD spectra. This CD system, the development of which took five years, can be used to observe even weak natural CD spectra. The polarization characteristics of this system were also evaluated in order to calibrate the recorded CD spectra. 相似文献
997.
D. Kaneko K. Yamagishi A. Tsukada T. Manabe M. Naito 《Physica C: Superconductivity and its Applications》2009,469(15-20):936-939
We report the synthesis of infinite-layer LaNiO2 thin films by metal organic decomposition. Our work is aimed to synthesize perovskite-like oxides with 3d9 electronic configuration, which high-Tc copper oxides commonly take. The 3d9 configuration is very rare in oxides other than cuprates. Ni1+ oxides, even though Ni1+ is an unusual oxidation state, may be one of very few candidates. One example is infinite-layer LaNiO2. The bulk synthesis of LaNiO2 is difficult, but we demonstrate in this article that the thin-film synthesis of LaNiO2 by metal organic decomposition is rather easy. This is due to the advantage of thin films with a large-surface-to-volume ratio, which makes oxygen diffusion prompt. Although superconductivity has not been observed yet, resistivity measurements indicate that LaNiO2 is conductive. 相似文献
998.
π‐Electron Systems That Form Planar and Interlocked Anion Complexes and Their Ion‐Pairing Assemblies 下载免费PDF全文
Dr. Ryohei Yamakado Dr. Tsuneaki Sakurai Dr. Wakana Matsuda Prof. Shu Seki Dr. Nobuhiro Yasuda Prof. Shigehisa Akine Prof. Hiromitsu Maeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):626-638
Interactions between designed charged species are important for the ordered arrangements of π‐electron systems in assembled structures. As precursors of π‐electron anion units, new arylethynyl‐substituted dipyrrolyldiketone boron complexes, which showed anion‐responsive behavior, were synthesized. They formed a variety of receptor–anion complexes ([1+1] and [2+1] types) in solution, and the stabilities of these complexes were discussed in terms of their thermodynamic parameters. Solid‐state ion‐pairing assemblies of [1+1]‐ and [2+1]‐type complexes with countercations were also revealed by single‐crystal X‐ray analysis. In particular, a totally charge‐segregated assembly was constructed based on negatively and positively charged layers fabricated from [2+1]‐type receptor–anion complexes and tetrabutylammonium cations, respectively. Furthermore, the [1+1]‐type anion complex of the receptor possessing long alkyl chains exhibited mesophases based on columnar assembled structures with contributions from charge‐by‐charge and charge‐segregated arrangements, which exhibited charge‐carrier transporting properties. 相似文献
999.
Kazunari Takaya Takahiro Kaneko Hajime Tanuma Tatsuhiro Nishide Hiroaki Sugiyama Nobuo Nakano Hisayuki Nagashima Yasuo Seto 《International Journal for Ion Mobility Spectrometry》2016,19(4):227-232
We determined new potential parameters for a calculation of ion mobility in air using the MOBCAL program. In our model, we regard air as a virtual uni-atomic molecular gas. And the Lennard-Jones parameters for various kinds of atoms in molecular ions were determined with simple and systematic methods. Using these parameters, we have calculated the mobilities of product ions from chemical warfare agents, normal saturated hydrocarbons, and illicit drugs. Most of the calculation results showed good agreement with the experimental values. Therefore this calculation method will be useful for understanding of the ion mobility spectrometry in air. 相似文献
1000.