全文获取类型
收费全文 | 348篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
化学 | 247篇 |
晶体学 | 3篇 |
力学 | 5篇 |
数学 | 25篇 |
物理学 | 84篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 14篇 |
2012年 | 23篇 |
2011年 | 24篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 23篇 |
2007年 | 15篇 |
2006年 | 26篇 |
2005年 | 13篇 |
2004年 | 17篇 |
2003年 | 22篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 11篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1960年 | 2篇 |
1959年 | 1篇 |
1926年 | 1篇 |
1899年 | 1篇 |
排序方式: 共有364条查询结果,搜索用时 15 毫秒
51.
Taro Yoshizawa 《International Journal of Non》1985,20(5-6):519-528
We discuss some sufficient conditions for attractivity of a closed set by using Liapunov functions and show how to apply our results to the study of asymptotic behaviors of solutions in nonautonomous systems. We also discuss the convergence of solutions by the same idea. These results are extendable to functional differential equations. 相似文献
52.
Saito K Arai T Takahashi N Tsukuda T Tsubomura T 《Dalton transactions (Cambridge, England : 2003)》2006,(37):4444-4448
A series of Cu(I) mixed-ligand complexes containing dmp (2,9-dimethyl-1,10-phenanthroline) and one of simple diphosphine ligands (Ph2P(CH2)nPPh2) were prepared. Among the complexes, [Cu(dppp)(dmp)]PF6 (n=3) and [Cu2(dppb)2(dmp)2](PF6)2 (n=4) were characterized by X-ray structure analyses. The dppp complex has been characterized as a mononuclear complex, while [Cu2(dppb)2(dmp)2]2+ exists as a dinuclear complex in which two dppb ligands bridge between the two Cu(I) atoms. Although the distorted tetrahedral structures around the central metals of the two complexes are similar, the P-Cu-P angles are different between the two complexes. All of the series of complexes show photoluminescence in solution, and the intensity of the luminescence increases with n (n=2-4). The non-radiative rate constants of the complexes decrease markedly with n although radiative rate constants of the complexes are similar. 相似文献
53.
Sakai K Ozawa H Yamada H Tsubomura T Hara M Higuchi A Haga MA 《Dalton transactions (Cambridge, England : 2003)》2006,(27):3300-3305
A tris(2,2'-bipyridine)ruthenium(II) derivative having two N-(3-ammoniopropyl)carbamoyl pendant units has been prepared and reacted with cis-PtCl2(DMSO)2 (DMSO = dimethyl sulfoxide) to give a heteronuclear Ru(II)Pt(II) dimer having a cis-Pt(II)Cl2(aliphatic amine)2 unit, [Ru(bpy)2(mu-bridge)PtCl2](PF6)2 (bpy = 2,2'-bipyridine, bridge = 4,4'-bis(N-(3-aminopropyl)carbamoyl)-2,2'-bipyridine). The ESI-TOF mass spectrum of the Ru(II)Pt(II) dimer shows a set of signals corresponding to {[Ru(bpy)2(mu-bridge)PtCl2](PF6)}(+) (m/z 1181.1). The MLCT (metal-to-ligand charge transfer) luminescence intensity is enhanced upon the platination of two amine units, presumably due to the formation of a relatively rigid metallocycle. More interestingly, the luminescence intensity is further enhanced by the complexation of the Ru(II)Pt(II) dimer with either 5'-GMP (guanosine 5'-monophosphate disodium salt) or calf thymus DNA. Visible-light-induced scission of supercoiled pBR322 DNA is found to be efficiently enhanced in the presence of the title Ru(II)Pt(II) dimer. 相似文献
54.
Endo O Furuta T Ozaki H Sonoyama M Mazaki Y 《The journal of physical chemistry. B》2006,110(26):13100-13106
The aggregation and reaction of 17,19-hexatriacontadiyne molecules are studied on a Au(111) surface. The molecular orientation and arrangement are elucidated by infrared reflection absorption spectroscopy (IRAS) and scanning tunneling microscopy (STM). A vapor-deposited monolayer and a multilayered film formed by adsorption from the solution provide IRA spectra with bands due to the antisymmetric and symmetric stretching of methylenes in the gauche conformation. After the adsorbed film is rinsed with the solvent, however, the spectrum loses the gauche bands and is characterized by the enhanced C-H(distal) and C-H(proximal) stretching bands, which means that all-trans molecules are laid flat. Only STM images for the rinsed film display columnar structures on the herringbones of the reconstructed Au(111) surface; the alkyl chain direction is found to be parallel to the Au atom row. The results indicate that an ordered monolayer is formed first at the liquid-solid interface, and then, disordered overlayers with the gauche conformation are grown but removed by a rinse. Upon exposure to UV light, thus obtained monomer columns are converted into oligomers with flexible backbones and an increased gauche population in the alkyl chains, which resemble red phase polydiacetylenes in LB films. 相似文献
55.
Nomura A Uyeda TQ Yumoto N Tatsu Y 《Chemical communications (Cambridge, England)》2006,(34):3588-3590
To design a nanoscale biodevice that can be controlled by an external stimulus, we have introduced photochemical switching peptides derived from the kinesin C-terminus domain into the kinesin-microtubule in vitro motility system. 相似文献
56.
The development of children's understanding of mathematical patterns through mathematical activities
In this paper we report how children (aged 8) developed their mathematical understanding through number tasks based on the Fibonacci sequence (Bamboo numbers) used in the context of a Substantial Learning Environment (SLE), which is designed to be mathematically rich, have a clear purpose and give opportunities to utilise mathematical thinking. The flexible nature of the SLEs makes it possible for teachers and children to explore various mathematical patterns. To capture children's activities when working within SLEs, we make particular reference to Pegg and Tall's work in 2005, and consider a theoretical framework based on the SOLO taxonomy (Biggs and Collis 1982) and the developmental process of understanding mathematical concepts. It was found that the key progression to be made through learning using our Bamboo number-based SLEs is from Multi-structural to Relational levels. It was also suggested that it is difficult for many children to understand the structural aspects of number patterns. 相似文献
57.
Hideya Sugimoto Masanori Tachikawa Taro Udagawa 《International journal of quantum chemistry》2019,119(10):e25895
The hydrogen transfer reaction in the reaction of HOSO + NO2 with and without H2O have been investigated using multicomponent quantum-mechanics method, which can directly take nuclear quantum effect (NQE) of light nuclei into account. For the case of the reaction without H2O, our calculation reveals that the reaction leading to trans-HONO is preferred. For the reaction with H2O, water-non-mediated and water-mediated (hydrogen-relay) hydrogen transfer mechanism are investigated. The NQE of hydrogen nucleus lowers the relative energy of the stationary point structures and reduces the activation barrier of the reactions. The largest stabilization is found in the transition state structure of the hydrogen-relay type reaction. H/D isotope effects for the reactions are also analyzed. In particular, H/D isotope effect on the activation barrier is analyzed in detail with the aid of the active strain model. 相似文献
58.
Ryosuke Sugiyama Takahiro Nakatani Shinichi Nishimura Kei Takenaka Taro Ozaki Shumpei Asamizu Hiroyasu Onaka Hideaki Kakeya 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(38):13620-13625
Organisms often produce secondary metabolites as a mixture of biosynthetically related congeners. However, why are metabolites with minor chemical variations produced simultaneously? 5‐Alkyl‐1,2,3,4‐tetrahydroquinolines (5aTHQs) are small, lipophilic metabolites produced by Streptomyces nigrescens HEK616 when cultured with Tsukamurella pulmonis TP‐B0596. A mixture of 5aTHQs forms aggregates that show enhanced membrane affinity and biological activity. The ability to form aggregates and membrane‐binding activity is regulated by the length of the alkyl chains. Aggregates with long alkyl chains were too stable to fuse with lipid membranes. However, if inactive 5aTHQ congener was mixed with active congener, the mixture showed increased membrane affinity, enabling cellular entry and biological activity. Therefore, it is shown that sloppiness in a biosynthetic pathway, by which minor structural variations can be produced, is functionally rational, as the metabolites show synergistic action. 相似文献
59.
Vladimir V. Plashnitsa Taro Ueda Perumal Elumalai Toshikazu Kawaguchi Norio Miura 《Ionics》2008,14(1):15-25
The nanostructured thin NiO films with the thicknesses of 30–180 nm were examined as a sensing electrode (SE) for the planar
mixed-potential-type yttria-stabilized zirconia (YSZ)-based NO2 sensor. The sensing characteristics were examined in the temperature range of 600–800 °C under the wet condition (5 vol.%
water vapor). Among the NiO-SEs tested, the 60 nm-thick NiO-SE sintered at 1,000 °C was found to give the highest NO2 sensitivity in the NO2 concentration range of 50–400 ppm accompanying with fast response/recovery at the operating temperatures of 600–700 °C. The
high NO2 sensitivity was attributed to the high catalytic activity for both electrochemical reactions of O2 and NO2 at the interface of NiO-SE/YSZ. The ultrathin gold layer with the thickness of about 60 nm was additionally formed on the
60 nm-thick NiO-SE to fabricate the laminated-type (60 nm NiO/60 nm Au)-SE. It was demonstrated that the use of this laminated
(NiO–Au)-SE improved both the sensitivity and the selectivity to NO2. 相似文献
60.
Yulu Jiang Dr. Taro Ozaki Mei Harada Tadachika Miyasaka Dr. Hajime Sato Dr. Kazunori Miyamoto Dr. Junichiro Kanazawa Dr. Chengwei Liu Prof. Dr. Jun-ichi Maruyama Dr. Masaatsu Adachi Dr. Atsuo Nakazaki Prof. Dr. Toshio Nishikawa Prof. Dr. Masanobu Uchiyama Dr. Atsushi Minami Prof. Dr. Hideaki Oikawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18152-18158
Lolitrems are tremorgenic indole diterpenes that exhibit a unique 5/6 bicyclic system of the indole moiety. Although genetic analysis has indicated that the prenyltransferase LtmE and the cytochrome P450 LtmJ are involved in the construction of this unique structure, the detailed mechanism remains to be elucidated. Herein, we report the reconstitution of the biosynthetic pathway for lolitrems employing a recently established genome-editing technique for the expression host Aspergillus oryzae. Heterologous expression and bioconversion of the various intermediates revealed that LtmJ catalyzes multistep oxidation to furnish the lolitrem core. We also isolated the key reaction intermediate with an epoxyalcohol moiety. This observation allowed us to establish the mechanism of radical-induced cyclization, which was firmly supported by density functional theory calculations and a model experiment with a synthetic analogue. 相似文献