全文获取类型
收费全文 | 337篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 266篇 |
晶体学 | 4篇 |
力学 | 5篇 |
数学 | 16篇 |
物理学 | 65篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 12篇 |
2012年 | 14篇 |
2011年 | 24篇 |
2010年 | 14篇 |
2009年 | 6篇 |
2008年 | 11篇 |
2007年 | 17篇 |
2006年 | 36篇 |
2005年 | 16篇 |
2004年 | 26篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有356条查询结果,搜索用时 78 毫秒
81.
Ionic liquids (ILs) are salts with an extremely low melting point. Substantial efforts have been made to address their low melting point from the enthalpic standpoint (i.e. interionic interactions). However, this question is still open. In this study, we report our findings that entropic (large fusion entropy), rather than enthalpic, contributions are primarily responsible for lowering the melting point in many cases, based on a large thermodynamic dataset. We have established a computational protocol using molecular dynamics simulations to decompose fusion entropy into kinetic (translational, rotational, and intramolecular vibrational) and structural (conformational and configurational) terms and successfully applied this approach for two representatives of ILs and NaCl. It is revealed that large structural contribution, particularly configurational entropy in the liquid state, plays a deterministic role in the large fusion entropy and consequently the low melting point of the ILs.Large structural entropy makes salts liquid at room temperature. 相似文献
82.
Nobuo Yamada Dr. Hiroki Noguchi Yoshifumi Orimoto Dr. Yutaka Kuwahara Prof. Dr. Makoto Takafuji Shaheen Pathan Dr. Reiko Oda Almara Mahammadali Rahimli Prof. Dr. Mahammadali Ahmed Ramazanov Prof. Dr. Hirotaka Ihara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(43):10141-10148
In this work, a new class of totally organic fluorescent nanogel particles and their exceptionally specific behaviors based on their unique structures are introduced, which draws a sharp line from conventional fluorophore-doped and fluorophore-branched-type particles. The nanogel particles, the diameter of which could be controlled by adjusting reaction conditions, such as the solvent system, were spontaneously fabricated with a spherical shape by direct polymerization of non-heterocyclic aromatic compounds, such as 2,6-dihydroxyanthracene, 2,6-dihydroxynaphthalene, and 9,9-bis(4-hydroxyphenyl)fluorene with triazinane as the cross-linker. A fluorophoric moiety formed from a polymer main chain was realized in the particle, and consequently, the resultant content of the fluorophoric moiety was around 70–80 wt % per particle. The uniqueness and versatility of the particles can be emphasized by their good compatibility with various solvents due to their amphiphilic and ampholytic swelling properties, but also by their remarkable fluorescent solvatochromism in the dispersion state. Furthermore, these behaviors were preserved even in their polymer composite system. This study also demonstrates that various fluorescent polymer films can be fabricated with emission color control due to memorization of the solvatochromism phenomenon of the dispersed fluorescent nanoparticles. 相似文献
83.
84.
The extraction of Cu(II) with 1-phenyl-3-methyl-4-acyl-5-pyrazolone (HA), in different organic solvents has been studied. The extraction mechanism of Cu(II) and the composition of the extracted species has been determined. Cu(II) was extracted as CuA2, or in the presence of TOPO, as CuA2TOPO. The extraction constants do not change regularly with increasing the length of acyl chain in the 1-phenyl-3-methyl-4-acyl-5-pyrazolone derivatives. The effect of the temperature on the extraction of Cu(II) has also been investigated. 相似文献
85.
Mizue Fujio Toshikazu Adachi Yoshifumi Shibuya Akihisa Murata Yuho Tsuno 《Tetrahedron letters》1984,25(40):4557-4560
Substituent effects of p-MeO and p-MeS groups deactivated by additional m-substituents in cumyl and α-phenylethyl solvolyses were studied to provide evidence for the higher resonance demand in the α-phenylethyl system. 相似文献
86.
Yutaka Nagai Nakahara Kouji Yoneyama Yoshifumi Kawano Katsuyasu Tanaka Katsumi Nakata Ryouhei 《Journal of Physics and Chemistry of Solids》2004,65(11):1861-1870
The characteristics of high-temperature ionic thermocurrent (HT ITC) in CaF2 doped with different sodium concentrations were studied by the Teflon-insulated electrode ITC method. It was shown that, with increasing sodium concentration, the HT ITC band moved toward a Na+-FV dipole band with a peak at 162 K. The results of analyses of the HT ITC spectra using an equivalent electric circuit proved that the activation energy of space charge migration related to HT ITC was also strongly dependent on the doped sodium concentrations if varied from 0.94 to 0.46 eV with increasing sodium concentration in our ITC study. In addition, the broadening of the Na+-FV dipole band was observed in 3 nominal mole% NaF-doped CaF2, which was accompanied by a considerable decrease of the activation energy from 0.46 to 0.29 eV without showing marked temperature shifts of the peak ITC bands. 相似文献
87.
Hiroyuki Usui Yoshifumi Watanabe Munefumi Kanao 《Journal of heterocyclic chemistry》1993,30(2):551-552
The preparation of bicyclic 1,3,5-triazine-2,4(3H)-diones 3 has been investigated. Diphenyl iminodicarboxylate ( 2 ) reacted smoothly with cyclic amidines to give bicyclic triazinediones in good yields. 相似文献
88.
Pyrimido[5,4-
]pteridine
-oxide (1) oxidizes efficiently benzene, toluene, and anisole under UV irradiation to give the corresponding phenol derivatives 4, though the easiness of the reaction significantly depends upon the nature of the substituents on the benzene ring. 相似文献
89.
Shouhei Toyoda Yoshifumi Yamaguchi Masataka Hiwatashi Yasuhiko Tomonari Hiroto Murakami Dr. Naotoshi Nakashima Prof. 《化学:亚洲杂志》2007,2(1):145-149
We designed and synthesized 4‐dodecyloxybenzenediazonium tetrafluoroborate ( 1 ), which preferentially reacts with metallic single‐walled carbon nanotubes (SWNTs) by kinetic control. We first determined the suitable experimental conditions for the preferential reaction of 1 with individually dissolved SWNTs by monitoring the decrease in absorbance for the metallic SWNT in the range of 400–650 nm in the absorption spectrum of the SWNTs. The reacted SWNTs were thoroughly rinsed with THF to obtain THF‐insoluble SWNTs. The Raman spectrum of the THF‐insoluble SWNTs showed a strong peak near 180 cm?1, which corresponds to a semiconducting breathing band. The metallic breathing bands (≈220 cm?1) and Breit–Wingner–Fano (BWF) modes (1520 cm?1) corresponding to the metallic SWNTs were much weaker than those of the pristine SWNTs. We also confirmed that metallic peaks in the range of 400–650 nm in the absorption spectrum of THF‐insoluble SWNTs that were individually dissolved in an aqueous micelle of sodium cholate were almost nondetectable. All the results indicate that the THF‐insoluble SWNTs are semiconducting. 相似文献
90.