全文获取类型
收费全文 | 174篇 |
免费 | 5篇 |
国内免费 | 19篇 |
专业分类
化学 | 139篇 |
晶体学 | 5篇 |
数学 | 7篇 |
物理学 | 47篇 |
出版年
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 18篇 |
2011年 | 13篇 |
2010年 | 7篇 |
2009年 | 15篇 |
2008年 | 13篇 |
2007年 | 20篇 |
2006年 | 13篇 |
2005年 | 13篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有198条查询结果,搜索用时 15 毫秒
1.
Studies of thickness and temperature dependencies of the dielectric susceptibility of nitrobenzene interlayers formed on conductive substrates were carried out. The obtained data were processed under the assumption of the existence of dimers (with opposite directions of molecular dipole moments) in orientationally ordered wall-adjacent layers. The results were treated on the basis of Lifshits theory. 相似文献
2.
The millimeter wave spectrum of the isotopically substituted CO dimer, (13C16O)2, has been studied for the first time, confirming and extending a recent infrared study. Eighty-seven transitions in the 77-180 GHz region have been assigned and analyzed in terms of a model-independent term value scheme involving 57 rotational levels with J=0-8. The levels can be classified into 7 “stacks” which have symmetry classifications of either A−/B+ or A+/B− and K-values of either 0 or 1. For the normal isotope, symmetry and nuclear spin statistics cause alternate rotational levels to be missing, but for (13C16O)2 all levels are present with an intensity alternation of 1:3 between A and B symmetries. The four A−/B+ stacks have not previously been observed, and the lowest of them establishes the tunneling splitting of (13C16O)2 to be 3.769 cm−1, slightly larger than the (12C16O)2 value of 3.731 cm−1. A large amount of precise experimental data is now available for the CO dimer, which should lead to greater theoretical insight into its structure and tunneling dynamics. 相似文献
3.
The mid-infrared (1500-3800 cm−1) absorption spectrum of gaseous nitric oxide has been studied at low temperature (99 K) with a long absorption path (160 m) in order to observe weak combination, difference, and overtone bands of the NO dimer. About ten new bands were assigned with greater or lesser certainty. Combined with previous results, they lead to a set of 12 secure and 7 tentative vibrational term values for (NO)2, essentially doubling our knowledge of NO dimer vibrational states. The strongest non-fundamental bands in this region, other than the ν1 (symmetric N-O stretch) + ν5 (asymmetric N-O stretch) overtone, involve combinations of ν5 with ν3 (intermolecular stretch). Excitation of ν5 results in increased frequencies for the intermolecular modes ν2, ν3, and ν4. A new value of 155.5 cm−1 was obtained for ν4, the elusive infrared-inactive out-of-plane fundamental vibration. 相似文献
4.
Hans Junek Taher El Sarhan Heinz Sterk 《Monatshefte für Chemie / Chemical Monthly》1988,119(6-7):717-726
Synthesis of methyl 3-amino-4-carbomyl-2-cyano-2-butenoate is described and2 a classified as a dimer of methyl cyanoacetate and cyanoacetamide. By ammonolysis of the dimer of methyl cyanoacetate with dimethylamine and anilines, resp. the dimethylamide and anilides, resp. (2 b and3 a–j) are obtained. Condensation with salicylaldehyde to the pyrone derivative4 proves the structure of2 a, ring closure reactions in basic or acidic medium yield the pyridones6 a and7 a,b, coupling with diazonium salts the pyridazines8 a–d. The amides2 and the anilides3 show hindered rotation of the enamino- and the amide-group by hydrogen bonds between the nitrogen functions and the ester carbonyl (Z-form). The G
values are reported. 相似文献
5.
Dr. Yogesh Kumar Maurya Dr. Pingchun Wei Takahide Shimada Dr. Kazuhisa Yamasumi Dr. Shigeki Mori Prof. Dr. Ko Furukawa Dr. Hajime Kusaba Prof. Dr. Tatsumi Ishihara Prof. Dr. Yongshu Xie Dr. Masatoshi Ishida Prof. Dr. Hiroyuki Furuta 《化学:亚洲杂志》2021,16(7):743-747
A facile synthetic strategy towards conformationally stable chiral chromophores based on dimeric porphyrinoids has been established. A peculiar class of face-to-face intramolecularly interlocked corrole dimers were formed by the oxidative C−C coupling linked at the inner carbon sites upon simple treatment of copper(II) ions. Their intrinsic electronic structures were modulated by the peripheral corrole ring annulations, which lead to distinct optical properties and redox profiles. The stereogenic carbon centers implemented in the confused corrole skeleton provided a rationale for designing novel chiral materials. 相似文献
6.
《Journal of Coordination Chemistry》2012,65(14):1209-1215
The synthesis, molecular structure and spectroscopic and magnetic properties of (NH4)2(15-crown-5)3[Ni(mnt)2]2 (mnt?=?maleonitriledithiolate dianion) are reported. The most notable structural feature of (NH4)2(15-crown-5)3[Ni(mnt)2]2 is that the ions form a stacked structure with well-separated columns along the c and a axes. Variable temperature magnetic susceptibility measurements indicate strong antiferromagnetic interactions in the complex. 相似文献
7.
Frederick H. Roos William H. Daly Marietta N. Aniano-Ilao Ioan I. Negulescu 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):275-290
Abstract The synthesis of a variety of substituted bisphenol A polysulfones, including nitro, amino, aminomethyl, ethyl, and methyl derivatives, is described. Nuclear magnetic resonance (NMR) (both proton and carbon, and several 2-D experiments) data confirm conclusions on the substitution site based on arguments on inductive effects in the phenyl rings. The proton ortho to the oxygen in the bisphenol A (BPA) residue is replaced in electrophilic substitution reactions. The degree of substitution was also calculated from the NMR results. The ethyl and methyl derivatives were expected, from the starting reactants, to each have a BPA ring substituted. The NMR data showed that, on the average, this is true. The nitro derivative also has substitution in every BPA ring, while the amino and aminomethyl derivatives have only intermittent BPA rings substituted. Measured degrees of substitution (DS) varied from 0.11 to 2.25. 相似文献
8.
Based on the fact that anthracene (Anth) possesses much higher similarity in electron-releasing ability to porphyrin nucleus than the other polyacenes, the dimeric octaethylporphyrin (OEP) derivatives 4 and 5 (OEP–Anth–OEP) were synthesized and their structure–property relationships were examined, as compared with related OEP dimers 1–3. Among them, the derivative 4 showed enormously high electronic communication between two terminal OEP rings, potentially providing a suitable unit of the electronic structure for molecular design of the OEP devices operating with less energy and with higher sensitivity to outside stimuli. 相似文献
9.
采用密度泛函理论的B3LYP, B3P86, B1B95, P3PW91和PBE1PBE方法结合SDD, LANL2DZ和CEP-121G基组计算了d~(10)组态二聚物MN(M=Ga, Ge, In, Sn和Sb; N=M和Al)的几何结构.采用B3P86/SDD进一步研究了MN@H_2O团簇的几何结构及吸附能.结果表明,水分子结合在二聚物M_2上时,对二聚物影响较大,对水分子自身影响较小.将M_2中Ga, Ge, In, Sn或Sb替换一个原子为Al时,水分子在GeAl和SnAl上的吸附能变化较大,而在GaAl, InAl和SbAl上吸附能变化较小.另外, H_2O吸附在Ga, Ge, In, Sn和Sb上时,与吸附在Al上时,吸附能的变化不大. 相似文献
10.
Naoyuki Toriumi Atsuya Muranaka Daisuke Hashizume Masanobu Uchiyama 《Tetrahedron letters》2017,58(23):2267-2271
Methylene-bridged benziphthalocyanine dimer 2 was unexpectedly generated by the reaction of dihydroxybenziphthalocyanine 1 and formaldehyde in the presence of a catalytic amount of a base at room temperature. Single-crystal X-ray diffraction analysis of 2 revealed a V-shaped structure. Dimer 2 exhibited longer-wavelength absorption and fluorescence bands than monomer 1 in the near-IR region. 相似文献