全文获取类型
收费全文 | 1488篇 |
免费 | 124篇 |
国内免费 | 2篇 |
专业分类
化学 | 1266篇 |
晶体学 | 17篇 |
力学 | 34篇 |
数学 | 40篇 |
物理学 | 257篇 |
出版年
2023年 | 16篇 |
2022年 | 24篇 |
2021年 | 43篇 |
2020年 | 41篇 |
2019年 | 64篇 |
2018年 | 52篇 |
2017年 | 28篇 |
2016年 | 52篇 |
2015年 | 54篇 |
2014年 | 66篇 |
2013年 | 103篇 |
2012年 | 140篇 |
2011年 | 147篇 |
2010年 | 65篇 |
2009年 | 43篇 |
2008年 | 95篇 |
2007年 | 78篇 |
2006年 | 58篇 |
2005年 | 60篇 |
2004年 | 48篇 |
2003年 | 43篇 |
2002年 | 32篇 |
2001年 | 13篇 |
2000年 | 19篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1990年 | 5篇 |
1988年 | 5篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 12篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1969年 | 4篇 |
1967年 | 5篇 |
排序方式: 共有1614条查询结果,搜索用时 15 毫秒
231.
Prof. Takayuki Nakajima Mizuki Takubo Yurika Komura Yuki Maeda Miwa Sato Maki Zouda Prof. Tomoaki Tanase 《欧洲无机化学杂志》2023,26(9):e202200648
A new series of cationic heterodinuclear complexes, [M1M2Cl2(meso-dpmppp)(RNC)2]PF6 (M1=Ni, M2=Rh, R=tBu ( 1 a ); M1=Pd, M2=Rh, R=tBu ( 2 a ), Xyl ( 2 b ); M1=Pt, M2=Rh, R=tBu ( 3 a ), Xyl ( 3 b ); M1=Pd, M2=Ir, R=tBu ( 4 a )), supported by a tetradentate phosphine ligand, meso-Ph2PCH2P(Ph)(CH2)3P(Ph)CH2PPh2 (meso-dpmppp), were synthesized by stepwise reactions of meso-dpmppp with NiCl2 ⋅ 6H2O or MCl2(cod) (M=Pd, Pt), forming mononuclear metalloligands of [M1Cl2(meso-dpmppp)], and with [M2Cl(cod)]2 (M2=Rh, Ir) and RNC (R=tBu, Xyl) in the presence of [NH4][PF6]. The related neutral PdRh complex, [PdRhCl3(meso-dpmppp)(XylNC)] ( 5 ), was also prepared. The structures of 1 – 5 were determined by X-ray analyses to contain two square planar d8 metal centers with face-to-face arrangement, where meso-dpmppp supports M1 and M2 metal ions in cis/trans-P,P coordination mode, combining cis-{M1P2Cl2} and trans-{M2P2(CNR)2} units. Complexes 1 – 4 showed an intence characteristic absorption around 422–464 nm derived from RhI→RNC MLCT transition (HOMO→LUMO+1), which are influenced by changing M1 (NiII, PdII, PtII) metal ions since HOMO composed of dσ* orbitals appreciably destabilized by changing M1 from Ni to Pd, and Pt. The electronic structures of 1 a – 4 a were investigated on the basis of DFT calculations and NBO analyses to show weak but noticeable d8–d8 metallophilic interaction as empirical dispersion energy of 0.9–1.5 kcal/mol without M1–M2 covalent bonding interaction. In addition, 1 – 5 were utilized as catalysts for hydrosilylation of styrene, and the NiRh complex 1 a was found to show higher activity and chemo- and regioselectivity compared with 2 – 5 . 相似文献
232.
As a model of polymer-sustained-alignment liquid crystal display (PSA-LCD), the liquid crystal (LC) cells having the polymer layers produced from monomers of phenanthrene (Phen)-carrying monomers, 2,7-, 3,8-, 1,8- and 3,6-dimethacryloyl-oxy-phenanthrene (DMAPhen), were prepared and investigated image sticking phenomenon with evaluations of residual direct current voltage (VrDC) and difference in pretilt angle before and after application of alternate current voltage (Δtilt). The VrDC values were small for the LC cells with the polymer layers produced from the Phen-carrying monomers used in this study. On the other hand, Δtilt depends on the molecular structure of the Phen-carrying monomer. The Δtilt values became small with increasing the linearity of the monomer structure for the Phen-carrying monomers. The findings would be useful for obtaining the small level of image sticking in the PSA-LCDs produced from the Phen-carrying monomers. 相似文献
233.
234.
Modification of Wide‐Band‐Gap Oxide Semiconductors with Cobalt Hydroxide Nanoclusters for Visible‐Light Water Oxidation 下载免费PDF全文
Prof. Dr. Kazuhiko Maeda Koki Ishimaki Yuki Tokunaga Dr. Daling Lu Dr. Miharu Eguchi 《Angewandte Chemie (International ed. in English)》2016,55(29):8309-8313
Cobalt‐based compounds, such as cobalt(II) hydroxide, are known to be good catalysts for water oxidation. Herein, we report that such cobalt species can also activate wide‐band‐gap semiconductors towards visible‐light water oxidation. Rutile TiO2 powder, a well‐known wide‐band‐gap semiconductor, was capable of harvesting visible light with wavelengths of up to 850 nm, and thus catalyzed water oxidation to produce molecular oxygen, when decorated with cobalt(II) hydroxide nanoclusters. To the best of our knowledge, this system constitutes the first example that a particulate photocatalytic material that is capable of water oxidation upon excitation by visible light can also operate at such long wavelengths, even when it is based on earth‐abundant elements only. 相似文献
235.
Inside Cover: Direct Transformation of Molecular Dinitrogen into Ammonia Catalyzed by Cobalt Dinitrogen Complexes Bearing Anionic PNP Pincer Ligands (Angew. Chem. Int. Ed. 46/2016) 下载免费PDF全文
236.
Direct Transformation of Molecular Dinitrogen into Ammonia Catalyzed by Cobalt Dinitrogen Complexes Bearing Anionic PNP Pincer Ligands 下载免费PDF全文
Dr. Shogo Kuriyama Dr. Kazuya Arashiba Prof. Dr. Hiromasa Tanaka Yuki Matsuo Dr. Kazunari Nakajima Prof. Dr. Kazunari Yoshizawa Prof. Dr. Yoshiaki Nishibayashi 《Angewandte Chemie (International ed. in English)》2016,55(46):14291-14295
The direct formation of ammonia from molecular dinitrogen under mild reaction conditions was achieved by using new cobalt dinitrogen complexes bearing an anionic PNP‐type pincer ligand. Up to 15.9 equivalents of ammonia were produced based on the amount of catalyst together with 1.0 equivalent of hydrazine (17.9 equiv of fixed nitrogen atoms). 相似文献
237.
Application to Photocatalytic H2 Production of a Whole‐Cell Reaction by Recombinant Escherichia coli Cells Expressing [FeFe]‐Hydrogenase and Maturases Genes 下载免费PDF全文
Dr. Yuki Honda Prof. Hidehisa Hagiwara Prof. Shintaro Ida Prof. Tatsumi Ishihara 《Angewandte Chemie (International ed. in English)》2016,55(28):8045-8048
A photocatalytic H2 production system using an inorganic–bio hybrid photocatalyst could contribute to the efficient utilization of solar energy, but would require the development of a new approach for preparing a H2‐forming biocatalyst. In the present study, we constructed a recombinant strain of Escherichia coli expressing the genes encoding the [FeFe]‐hydrogenase and relevant maturases from Clostridium acetobutylicum NBRC 13948 for use as a biocatalyst. We investigated the direct application of a whole‐cell of the recombinant E. coli. The combination of TiO2, methylviologen, and the recombinant E. coli formed H2 under light irradiation, demonstrating that whole cells of the recombinant E. coli could be employed for photocatalytic H2 production without any time‐consuming and costly manipulations (for example, enzyme purification). This is the first report of the direct application of a whole‐cell reaction of recombinant E. coli to photocatalytic H2 production. 相似文献
238.
Yuki Kanazawa Prof. Hayato Tsuji Prof. Masahiro Ehara Prof. Ryoichi Fukuda Dr. Deborah L. Casher Prof. Kohei Tamao Prof. Hiroshi Nakatsuji Prof. Josef Michl 《Chemphyschem》2016,17(19):3010-3022
The photophysical properties of oligosilanes show unique conformational dependence due to σ‐electron delocalization. The excited states of the SAS, AAS, and AEA conformations of peralkylated n‐hexasilanes, in which the SiSiSiSi dihedral angles are controlled into a syn (S), anti (A), or eclipsed (E) conformation, were investigated by using UV absorption, magnetic circular dichroism (MCD), and linear dichroism spectroscopy. Simultaneous Gaussian fitting of all three spectra identified a minimal set of transitions and the wavenumbers, oscillator strengths, and MCD B terms in all three compounds. The results compare well with those obtained by using the symmetry‐adapted‐cluster configuration interaction method and almost as well with those obtained by time‐dependent density functional theory with the PBE0 functional. The conformational dependence of the transition energies and other properties of free‐chain permethylated n‐hexasilane, n‐Si6Me14, was also examined as a function of dihedral angles, and the striking effects found were attributed to avoided crossings between configurations of σσ* and σπ* character. 相似文献
239.
Nishizawa M Hirakawa H Nakagawa Y Yamamoto H Namba K Imagawa H 《Organic letters》2007,9(26):5577-5580
The reaction of alkyl-substituted sec-ethoxyalkynyl acetates with water catalyzed by Hg(OTf)2 afforded alpha,beta-unsaturated esters in excellent yield with high catalytic turnover up to 1000 times under very mild reaction conditions with virtually complete E-selectivity, superior even to that of the HWE reaction. 相似文献
240.
Yuki H Tanaka Y Hata M Ishikawa H Neya S Hoshino T 《Journal of computational chemistry》2007,28(6):1091-1099
No explicit pi-pi interaction term has been incorporated in the conventional molecular dynamics (MD) simulation programs in spite of its significant role in the folding of biomolecules and the clustering of organic chemicals. In this article, we propose a technique to emphasize the effect of pi-pi interactions using a function of energy and implement it into an MD simulation program. Several trial calculations show that the pi-pi incorporated program gives improved results consistent with experimental data on atom geometry and has no unfavorable interference with the conventional computational framework. This indicates an importance of the explicit consideration of pi-pi interactions in MD simulation. 相似文献