全文获取类型
收费全文 | 346篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
化学 | 289篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 15篇 |
物理学 | 49篇 |
出版年
2023年 | 1篇 |
2021年 | 10篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 15篇 |
2012年 | 22篇 |
2011年 | 17篇 |
2010年 | 11篇 |
2009年 | 11篇 |
2008年 | 20篇 |
2007年 | 20篇 |
2006年 | 28篇 |
2005年 | 31篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 21篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有356条查询结果,搜索用时 122 毫秒
31.
Takayoshi Kimura Sekai Iwama Satoko Kido Mohammad Abdullah Khan 《The Journal of chemical thermodynamics》2009,41(10):1170-1177
Enthalpies of mixing and the densities of ethanol solution of R- and S-enantiomers of camphor, 10-camphorsulfonamide, 10-camphorsulfonic acid, camphorquinone, and 10-camphorsulfonyl chloride have been measured for a wide range of mole fractions of heterochiral components at 298.15 K. Enthalpies of mixing were exothermic for all concentrations and heterochiral solutions were more stable than each of the homochiral solutions. Enthalpic stabilization of mixing of heterochiral solutions was increased with a decreasing concentration of all the camphor derivatives measured. The sequence of enthalpic stabilization on mixing was 10-camphorsulfonyl chloride, 10-camphorsulfonic acid, 10-camphorsulfonamide, camphor, and camphorquinone. Apparent molar volumes were determined and excess volumes of mixing of heterochiral solutions were small and negative. Enthalpic stabilizations were found to be dependent on dipole–dipole interaction between solutes and solvents. 相似文献
32.
Oxidative Degradation of Aqueous Cresols Induced by Gaseous Plasma with Contact Glow Discharge Electrolysis 总被引:2,自引:0,他引:2
The oxidative degradation of cresols smoothly proceeded toward inorganic end products when a gaseous plasma generated by means
of dc glow discharge was sustained in contact with the surface of aqueous solution containing organic compounds. In order
to get mechanistic insight, the monohydroxylation products from each isomeric cresol were closely examined as primary intermediates
to reveal that the aromatic hydroxylation preferentially occurred at the position para to the hydroxyl group of each starting
material. It was also established that the degradation of cresols strictly followed the first-order rate law. On the basis
of the orientational analysis and the kinetical consideration including the effects of Fe ions added on the reaction rate,
it was concluded that hydroxyl radical, which might result from the homolytic cleavage of water molecules by the action of
plasma, was the most likely reagent responsible for the mineralization of cresols. 相似文献
33.
Keisuke Akita Youhi Morii Hisashi Nakamura Takuya Tezuka Kaoru Maruta 《Proceedings of the Combustion Institute》2021,38(2):2247-2255
Two-dimensional axisymmetric numerical simulation reproduced flames with repetitive extinction and ignition (FREI) in a micro flow reactor with a controlled temperature profile with a stoichiometric n-heptane/air mixture, which have been observed in the experiment. The ignition of hot flame occurred from consumption reactions of CO that was remained in the previous cycle of FREI. Between extinction and ignition locations of hot flames, several other heat release rate peaks related to cool and blue flames were observed for the first time. After the extinction of the hot flame, cool flame by the low-temperature oxidation of n-heptane appeared first and was stabilized in a low wall temperature region. In the downstream of the stable cool flame, a blue flame by the consumption reactions of cool flame products of CH2O and H2O2 appeared. After that, the hot flame ignition occurred from the remaining CO in the downstream of the blue flame. Then after the next hot flame ignition, the blue flame was swept away by the propagating hot flame. Soon before the hot flame merged with the stable cool flame, the hot flame propagation was intensified by the cool flame. After the hot flame merged with the stable cool flame, the hot flame reacted with the incoming fresh mixture of n-C7H16 and O2. 相似文献
34.
Kotaro Nagatani Yunosuke Hoshino Haruka Tezuka Masahisa Nakada 《Tetrahedron letters》2017,58(10):959-962
A synthetic pathway to the C-ring fragment of cotylenin A which emerged from our retrosynthetic analysis of cotylenin A is described. The catalytic asymmetric intramolecular cyclopropanation (CAIMCP) of the α-diazo-β-keto ester bearing 2,4,6-trimethylphenyl group as the ester part has been found to afford the crystalline product with high ee, which allowed to establish the approach to the C-ring fragment which required ten-pot operations. The developed approach would be beneficial to a large scale synthesis of the C-ring fragment for the total synthesis of cotylenin A. 相似文献
35.
Enthalpies of mixing of ethanol solution of R- and S-enantiomers of limonene in large concentration have been measured at 298.15 K. The enthalpies of mixing were negligibly small
for all concentrations. Enthalpies of mixing showed negative in less than 30 mol%, but positive in more than the high concentration
of limonenes. The heterochiral solutions were more stable than each of the homochiral solutions in dilute solutions. The concentration
dependence on enthalpies of mixing in dilute concentration of less than 10 mol% was much sharper in inclination than the dense
solutions limonene. 相似文献
36.
The cytotoxicity of 39 compounds, including eighteen flavonoids (flavanones, 1-10; flavones, 11-17; flavanol, 18), sixteen phenolic acid derivatives (aromatic acids, 19-24; aldehyde, 25; esters, 26-34) and five glycerides (35-39), isolated from Mexican propolis, were evaluated against a panel of six different cancer cell lines; murine colon 26-L5 carcinoma, murine B16-BL6 melanoma, murine Lewis lung carcinoma, human lung A549 adenocarcinoma, human cervix HeLa adenocarcinoma and human HT-1080 fibrosarcoma. A phenylpropanoid-substituted flavanol, (2R,3S)-8-[4-phenylprop-2-en-1-one]-4',7-dihydroxy-3',5-dimethoxyflavan-3-ol (18), showed the most potent cytotoxicity against A549 cells (IC50, 6.2 microM) and HT-1080 cells (IC50, 3.9 microM), stronger than those of the clinically used anticancer drug, 5-fluorouracil (IC50, 7.5 microM and 5.4 microM, respectively). Based on the observed results, the structure-activity relationships are discussed. 相似文献
37.
Decomposition of Benzene in Air in a Plasma Reactor: Effect of Reactor Type and Operating Conditions 总被引:2,自引:0,他引:2
Ogata A. Miyamae K. Mizuno K. Kushiyama S. Tezuka M. 《Plasma Chemistry and Plasma Processing》2002,22(4):537-552
The decomposition of benzene was carried out in two types of plasma reactors packed with BaTiO3 pellets: one reactor had two stainless steel electrodes (SUS reactor), and the other reactor had a glass layer between two concentric electrodes (GL reactor). The decomposition efficiency and the suppression of formation of N2O and NOx were greater in the GL reactor than in the SUS reactor. In contrast, the suppression of O3 formation and the oxidation to COx in the SUS reactor were superior to those in the GL reactor. The effect of wa eform and frequency of applied ac power was in estigated for each reactor. 相似文献
38.
Satoko Ishibe Ikuyoshi Tomita 《Journal of polymer science. Part A, Polymer chemistry》2005,43(15):3403-3410
A novel synthetic method for soluble precursor polymers of poly(p‐phenylene vinylene) (PPV) derivatives by the palladium‐catalyzed three‐component coupling polycondensation of aromatic diiodides, aromatic bis(boronic acid) derivatives, and norbornadiene is described. For example, the polymerization of 1,4‐diiodo‐2,5‐dioctyloxybenzene, benzene‐1,4‐bis(boronic acid propanediol ester), and norbornadiene at 100 °C for 3 days provided a polymer consisting of the three monomer units in a 97% yield (number‐average molecular weight = 3100, weight‐average molecular weight/number‐average molecular weight = 1.37). A derivative of PPV was produced smoothly by the retro Diels–Alder reaction of the polymer both in a dodecyloxybenzene solution and in a film at 200 °C in vacuo. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3403–3410, 2005 相似文献
39.
Kato S Tani K Ishida M Nonogaki J Ebihara M Hayashi S Nakanishi W Niyomura O Ando F Koketsu J 《Dalton transactions (Cambridge, England : 2003)》2011,40(32):8156-8169
A series of selenium and tellurium bis(carbodithioates and carbothioates) were synthesized. X-Ray structure analysis revealed that Se(SSCC(6)H(4)OMe-2)(2), Te(SSCC(6)H(4)OMe-2)(2) and Te(SSCC(6)H(4)Me-4)(2) have trapezoidal-planar configuration of ES(4) (E = Se, Te) and despite the larger atomic radii, the C=S···Te distances in Te(SSCC(6)H(4)OMe-2)(2) are comparable to those in the corresponding selenium derivatives Se(SSCC(6)H(4)OMe-2)(2). Molecular-orbital calculations performed on compounds E(E'SCR)(2) (E = S, Se, Te; E' = O, S; R = Me, Ph, C(6)H(4)OMe-2) showed that the syn-conformers of Se(SSCR)(2) and Te(SSCR)(2) are more stable than the corresponding anti-ones, while, in the case of carbothioic acid derivatives, E(SOCR)(2) showed that their anti-conformers are all more stable than the corresponding syn-ones. Natural bond orbital (NBO) analyses of these dithio-compounds revealed that two types of orbital interactions, n(S(1))→σ*(E-S(2)) and n(O)→σ*(E-S(2)), play a role in the bonding of E[S(2)S(1)CC(6)H(4)OMe-2](2) (E = Se, Te) and the former play a particularly predominant role. 相似文献
40.
The relativistic effects on absolute magnetic shielding tensors (σ(Se)) are explicitly evaluated for various selenium species (40 species) with the DFT(BLYP)-GIAO method. Calculations are performed under relativistic and nonrelativistic conditions with the Slater-type basis sets in ADF 2010 in the framework of ZORA, employing the optimized structures under nonrelativistic conditions at B3LYP of Gaussian 03. Quadruple zeta all electron with four polarization functions (QZ4Pae) are mainly applied to evaluate σ(Se). Ranges of the effect on diamagnetic (σ(d)(Se)), paramagnetic shielding tensors (σ(p)(Se)), and σ(d+p)(Se) (= σ(d)(Se) + σ(p)(Se)) are -24 to -20 ppm, -115 to -3 ppm, and -136 to -26 ppm, respectively. The spin-orbit terms (σ(so)(Se)) are evaluated to be 92-225 ppm with QZ4Pae, which clarifies the effect on total shielding tensors (σ(t)(Se) = σ(d+p)(Se) + σ(so)(Se)) to be -8 to 152 ppm, at the spin-orbit ZORA level. The calculated σ(t)(Se) values reproduced well the observed values. 相似文献