全文获取类型
收费全文 | 234篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 191篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 4篇 |
物理学 | 50篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 16篇 |
2019年 | 15篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 17篇 |
2012年 | 12篇 |
2011年 | 17篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 6篇 |
2005年 | 12篇 |
2004年 | 5篇 |
2003年 | 16篇 |
2002年 | 6篇 |
1999年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有250条查询结果,搜索用时 234 毫秒
81.
Dr. Shinobu Arikawa Dr. Akihiro Shimizu Dr. Daisuke Shiomi Prof. Dr. Kazunobu Sato Prof. Dr. Takeji Takui Dr. Hikaru Sotome Prof. Dr. Hiroshi Miyasaka Dr. Masahito Murai Prof. Dr. Shigehiro Yamaguchi Prof. Dr. Ryo Shintani 《Angewandte Chemie (International ed. in English)》2023,62(29):e202302714
A kinetically-stabilized nitrogen-doped triangulene cation derivative has been synthesized and isolated as the stable diradical with a triplet ground state that exhibits near-infrared emission. As was the case for a triangulene derivative we previously synthesized, the triplet ground state with a large singlet-triplet energy gap was experimentally confirmed by magnetic measurements. In contrast to the triangulene derivative, the nitrogen-doped triangulene cation derivative is highly stable even in solution under air and exhibits near-infrared absorption and emission because the alternancy symmetry of triangulene is broken by the nitrogen cation. Breaking the alternancy symmetry of triplet alternant hydrocarbon diradicals by a nitrogen cation would therefore be an effective strategy to create stable diradicals possessing magnetic properties similar to the parent hydrocarbons but with different electrochemical and photophysical properties. 相似文献
82.
Dr. Hikaru Yanai 《Chemical record (New York, N.Y.)》2023,23(9):e202300076
During the past decade, carbon (C−H) acids depicted as ‘Tf2CHR’ (Tf=CF3SO2) have attracted considerable attention as a new class of superacidic molecules, which show stronger acidity than sulfuric acid molecules. In recent years, the author has developed a synthetic methodology for such strong acids and has opened the door to chemistry of highly stabilised carbanions [Tf2CR]−, which are the conjugate bases of the carbon acids. These carbanion-containing salts are stable and easy-to-handle species. Our efforts have revealed that the ionic but lipophilic characters of this type of carbanion can be used as a unique ‘substituent’ for increasing both the water solubility and the lipophilicity of organic compounds. This Personal Account provides an overview of our [Tf2CR]− chemistry, including its synthesis, structure, reactivity, and applications. 相似文献
83.
Kitamura H 《The Journal of chemical physics》2007,126(13):134509
A variational associating fluid theory is proposed to describe equations of state for expanded fluid mercury. The theory is based on the soft-sphere variational theory, incorporating an ab initio diatomic potential and an attractive many-body potential; the latter is evaluated with quantum chemical methods and expressed as a function of the local atomic coordination number and the nearest-neighbor distance. The resultant equation of state can reproduce the observed gas-liquid coexistence curve with good accuracy, without introducing phenomenological effective pair potentials. Various thermodynamic quantities such as pressure, isocloric thermal pressure coefficient, adiabatic sound velocity, and specific heat are calculated over a wide density-temperature range and compared with available experimental data. 相似文献
84.
Matsushima S Takasu A Inai Y Hirabayashi T Era S Sogami M Sasaki F Ohsaki H Kinosada Y 《Magnetic resonance imaging》2002,20(3):285-293
The values of equivalent cross-relaxation rate (ECR) correlated well with [i] water conditions in various copolymer gels and [ii] nature of malignant cells with regard to nuclear dysplasia and mitotic potential in breast carcinomas. The synthetic copolymer gels composed of any two or three monomers among 2-hydroxyethyl methacrylate (HEMA), glycidyl methacrylate (GMA), N-vinyl-2-pyrrolidinone (N-VP), methyl methacrylate (MMA) and benzyl methacrylate (BMA). The ECR measurement was performed by using an off-resonance saturation pulse under conventional field-echo imaging at frequency within +/- 75 ppm apart from the water resonance frequency. The ECR values were readily to determine and non-time consuming parameter for cross relaxation rate. The ECR values at the frequency offset by 7-ppm (ECR-7) were divided the sample gels two classes, which must correspond to hydrophilic or hydrophobic ones.The sensitivity in the gels was nearly equivalent to the cross-relaxation rate itself. In the breast carcinomas, the ECR-7 correlates with the nature of malignant cells with regard to nuclear dysplasia and mitotic potential. The ECR-7 is better or more accurate than the STR-7 because the SDNRs between carcinoma and glandular tissue increased by approximately 50% on the ECR-7 compared with the STR-7. Thus the ECR values could be a new parameter for malignancy and cell proliferative activity of the breast carcinomas with non-invasive modalities by magnetic resonance imaging. 相似文献
85.
Solvation properties of aliphatic alcohol–water and fluorinated alcohol–water solutions were probed by amide molecules as
solutes using infrared (IR) and 1H and 13C NMR techniques. These include four alcohols: ethanol (EtOH), 2-propanol (2-PrOH), 2,2,2-trifluoroethanol (TFE), and 1,1,1,3,3,3-hexafluoro-2-propanol
(HFIP) and three amides: N-methylformamide (NMF), N-methylacetamide (NMA) and N-methylpropionamide (NMP). The hydrogen bonds of the amide carbonyl oxygen with water are gradually weakened as the alcohol
content increases. This decreases in the order of HFIP > TFE ≈ 2-PrOH > EtOH. In TFE– and HFIP–water solutions, the hydrogen
bond between the amide amino hydrogen and water is also gradually broken with increasing x
A. This trend is more notable in the order of NMP > NMA > NMF. The hydrophobic moieties of the amide methyl and ethyl groups
are solvated by the fluoroalkyl groups of fluorinated alcohols due to the hydrophobic interaction among them. Thus, the steric
hindrance generated by the solvated alkyl group of amides promotes the breaking of the hydrogen bonds between amide and water. 相似文献
86.
Hikaru Morimoto Marie Minato Tomohiko Nakagawa Masahide Sato Yoshio Kobayashi Kohsuke Gonda Motohiro Takeda Noriaki Ohuchi Noboru Suzuki 《Journal of Sol-Gel Science and Technology》2011,59(3):650-657
A preparation method for gadolinium compound (Gd) nanoparticles coated with silica (Gd/SiO2) is proposed. Gd nanoparticles were prepared with a homogeneous precipitation method at 80 °C using 1.0 × 10−3 M Gd(NO3)3 and 0.5 M urea in the presence of 1.0 g/L stabilizer. Among stabilizers examined. Sodium n-dodecyl sulfate (SDS) was suitable
as the stabilizer for preparing small Gd nanoparticles, and consequently Gd nanoparticles with a size of 46.2 ± 12.4 nm were
prepared using the SDS. Silica-coating of the Gd nanoparticles was performed by a St?ber method at room temperature using
0.013 M TEOS and 2.0 × 10−3 M NaOH in water/1-propanol solution in the presence of 1.0 × 10−3 M Gd nanoparticles, which resulted in production of Gd/SiO2 particles with an average size of 64.2 ± 14.4 nm. The Gd/SiO2 particles were surface-modified with 3-aminopropyltrimethoxysilane and succinic anhydride. It was confirmed by measurement
of electrophretic light scattering that amino group or carboxyl group was introduced onto the Gd/SiO2 particles. The gadolinium concentration of 1.0 × 10−3 M in the as-prepared colloid solution was increased up to a gadolinium concentration of 0.4 M by centrifugation. The core–shell
structure of Gd/SiO2 particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The
concentrated Gd/SiO2 colloid solution showed an X-ray image with contrast as high as a commercial Gd complex contrast agent. Internal organs in
a mouse could be imaged injecting the concentrated colloid solution into it. 相似文献
87.
Isozaki K Ogata K Haga Y Sasano D Ogawa T Kurata H Nakamura M Naota T Takaya H 《Chemical communications (Cambridge, England)》2012,48(33):3936-3938
A new type of Pt-complex-bound amino acid was synthesized by condensation of a cyclometalated Pt complex with the side-chain residue of N- and C-alkylated glutamic acid. Self-assembly of the Pt-bound lipophilic amino acid afforded a supramolecular gel in organic solvents, which comprised fibrous lamellar aggregates that supported a highly oriented Pt array. 相似文献
88.
Miura T Kasuga H Imai K Ina M Tada N Imai N Itoh A 《Organic & biomolecular chemistry》2012,10(11):2209-2213
A fluorous organocatalyst promotes direct asymmetric aldol reactions of aromatic aldehydes with ketones in brine to afford the corresponding anti-aldol products in high yield with up to 96% ee. Fluorous organocatalyst can be readily recovered by solid phase extraction using fluorous silica gel and reused without purification. 相似文献
89.
Stanislav Jureckova Maria Jureckova Ferdinand Chovanec Hikaru Kobayashi Masao Takahashi Milan Mikula Emil Pina 《Central European Journal of Physics》2009,7(2):321-326
The roughness of the semiconductor surface substantially influences properties of the whole structure, especially when thin
films are created. In our work 3C SiC, 4H SiC and Si/a-SiC:H/SiO2 structures treated by various oxidation a passivation procedures are studied by atomic force microscopy (AFM) and scanning
tunnelling microscopy (STM). Surface roughness properties are studied by fractal geometry methods. The complexity of the analysed
surface is sensitive to the oxidation and passivation steps and the proposed fractal complexity measure values enable quantification
of the fine surface changes. We also determined the optical properties of oxidized and passivated samples by using visual
modelling and stochastic optimization.
相似文献
90.
Chie Tsukada Hikaru Yoshida Satoshi Ogawa Akitaka Yoshigoe Shinya Yagi Tsuyoshi Yaita 《Surface and interface analysis : SIA》2019,51(1):85-88
In this study, gold nanoparticles (AuNPs) prepared in a 5 mM CsCl aqueous solution using the solution-plasma method are characterized via transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy with synchrotron radiation (SR-XPS). The particle diameter is measured over the process time via TEM. During the solution-plasma process, small particles of 2.1 to 2.2-nm diameter are generated in the CsCl aqueous solution; these particles then enlarge via Ostwald ripening over time until they reach an equilibrium size of ~13 nm after 36 days. In addition, the surface chemical states of the AuNPs are characterized at different depths via SR-XPS. The SR-XPS measurements obtained using incident X-ray energy (hν) of 945.0 eV revealed that Cs─Au, Cl─Au, and Cs─Cl─Au bonds are present 1.2 nm below the surface. The measurements obtained at an incident X-ray energy of 2515.0 eV showed that Cs─Cl─Au bonding is also present 2.5 nm below the surface, indicating that Cs and Cl strongly interact with Au. The TEM and SR-XPS measurements revealed that 2 processes occur cyclically during the growth process via Ostwald ripening: (i) the Cs and Cl in the aqueous solution adsorb on the AuNP surface and (ii) Au atoms subsequently bond to the AuNPs surface. 相似文献