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21.
Jang JS Ham DJ Ramasamy E Lee J Lee JS 《Chemical communications (Cambridge, England)》2010,46(45):8600-8602
Mesoporous tungsten carbides displayed an excellent solar conversion efficiency (7.01%) as a counter electrode for dye sensitized solar cells under 100 mW cm(-2), AM 1.5G illumination, which corresponded to ca. 85% of the efficiency of the conventional platinum electrode. 相似文献
22.
Highly Enantioselective Extraction of Underivatized Amino Acids by the Uryl‐Pendant Hydroxyphenyl‐Binol Ketone 下载免费PDF全文
Dr. Haofei Huang Qian Chen Misun Choi Prof. Raju Nandhakumar Dr. Zhishan Su Prof. Dr. Sihyun Ham Prof. Kwan Mook Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(10):2895-2900
The hydroxyphenyl chiral ketone, (S)‐ 3 , reacts with D ‐amino acids bearing hydrophobic side chains exclusively over the L ‐amino acids in a two‐phase liquid–liquid extraction, and thus acts as a highly stereoselective extractant. Calculations for the energy‐minimized structures for the imine diastereomers and the comparison of the selectivities with other phenyl ketones, (S)‐ 4 and (S)‐ 5 , demonstrate that the hydrogen bond between the carboxylate group and the phenolic hydroxyl group contributes to the remarkable enantioselectivities. The multiple hydrogen bonds present in the imine of (S)‐ 3 reinforce the rigidity, and results in the difference between the stabilities of the imine diastereomers. The imine could be hydrolyzed in methanolic HCl solution, and the extraction of the evaporated residues revived the organic layer of (S)‐ 3 , which could enter into a new extractive cycle and leaves the D ‐amino acid with enantiomeric excess (ee) values of over 97 % in the aqueous layer. 相似文献
23.
Min‐kyoung Ham Ji HoYouk Yong‐Ku Kwon Young‐Je Kwark 《Journal of polymer science. Part A, Polymer chemistry》2012,50(12):2389-2397
A photoinitiation process was investigated to develop a rapid and well‐controlled RAFT polymerization method applied to vinyl acetate (VAc) using methyl (ethoxycarbonothioyl)sulfanyl acetate (MESA) and bis(2,4,6‐trimethylbenzoyl)phenylphosphine oxide as the RAFT agent and photoinitiator, respectively. MESA was selected as the photochemically inert RAFT agent to minimize photolysis of the thiocarbonylthio groups during polymerization. Poly(vinyl acetate) with a prespecified well‐controlled molecular weight (MW) and a narrow MW distribution was successfully synthesized. The polymerization reaction proceeded as a living polymerization and was remarkably rapid compared with approaches that use thermally initiated processes with a very short induction period. A detailed kinetic study of the mechanism underlying the polymerization reaction, however, revealed that the chain ends containing xanthate moieties were not perfectly stable upon UV‐irradiation, and they generated radicals via homolytic cleavage. This reaction appeared to proceed by a combination of a degenerative transfer RAFT mechanism and a dissociation‐combination mechanism. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
24.
[reaction: see text] Natural 6-epiplakortolide E was first synthesized from readily available 1-bromo-10-phenyldecane in 10 steps by using singlet oxygen-mediated Diels-Alder reaction to form cyclic peroxide followed by a directed iodolactonization to give the peroxylactone core. 相似文献
25.
26.
S. W. Ham J. O. Im S. K. Oh 《The European Physical Journal C - Particles and Fields》2008,58(4):579-590
Within the framework of the minimal non-minimal supersymmetric standard model (MNMSSM) with tadpole terms, CP violation effects
in the Higgs sector are investigated at the one-loop level, where the radiative corrections from the loops of the quark and
squarks of the third generation are taken into account. Assuming that the squark masses are not degenerate, the radiative
corrections due to the stop and sbottom quarks give rise to CP phases which trigger the CP violation explicitly in the Higgs
sector of the MNMSSM. The masses, the branching ratios for dominant decay channels, and the total decay widths of the five
neutral Higgs bosons in the MNMSSM are calculated in the presence of explicit CP violation. The dependence of these quantities
on the CP phases is quite recognizable, for given parameter values. 相似文献
27.
P.H. Cannington Norman S. Ham 《Journal of Electron Spectroscopy and Related Phenomena》1983,31(2):175-179
Band intensifies in the He(I) and HE(II) photoelectron spectra of some simple organic molecules (methanol, methylamine, formaldehyde, acetaldehyde, formic acid, acetic acid, methyl formate, ethylene, butadiene and methyl isothiocyanate) have been measured. The relative band intensity ratios for a number of ionizations from n and π orbitals are presented. 相似文献
28.
A bimolecular rate constant, kOH + dihydromyrcenol, of (38 ± 9) × 10?12 cm3 molecule?1 s?1 was measured using the relative rate technique for the reaction of the hydroxyl radical (OH) with 2,6‐dimethyl‐7‐octen‐2‐ol (dihydromyrcenol,) at 297 ± 3 K and 1 atm total pressure. Additionally, an upper limit of the bimolecular rate constant, k, of approximately 2 × 10?18 cm3 molecule?1 s?1 was determined by monitoring the decrease in ozone (O3) concentration in an excess of dihydromyrcenol. To more clearly define part of dihydromyrcenol's indoor environment degradation mechanism, the products of the dihydromyrcenol + OH and dihydromyrcenol + O3 reactions were also investigated. The positively identified dihydromyrcenol/OH and dihydromyrcenol/O3 reaction products were acetone, 2‐methylpropanal (O?CHCH(CH3)2), 2‐methylbutanal (O?CHCH(CH3)CH2CH3), ethanedial (glyoxal, HC(?O)C(?O)H), 2‐oxopropanal (methylglyoxal, CH3C(?O)C(?O)H). The use of derivatizing agents O‐(2,3,4,5,6‐pentafluorobenzyl)hydroxylamine (PFBHA) and N,O‐bis(trimethylsilyl)trifluoroacetamide (BSTFA) clearly indicated that several other reaction products were formed. The elucidation of these other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible dihydromyrcenol/OH and dihydromyrcenol/O3 reaction mechanisms based on previously published volatile organic compound/OH and volatile organic compound/O3 gas‐phase reaction mechanisms. © 2006 Wiley Periodicals, Inc. * 1 This article is a US Government work and, as such, is in the public domain of the United States of America Int J Chem Kinet 38: 451–463, 2006 相似文献
29.
Alcohol-containing potassium organotrifluoroborates as starting reagents were prepared from their corresponding dibromobenzenes through a sequential one-pot reaction. The oxidation reactions of these substrates, which were carried out using 3.0 equiv of 8 N Jones reagent in acetone at 0 °C, provided a high yield of the desired carbonyl-functionalized compounds. In addition, the cross-coupling reactions of these organocarbonyltrifluoroborates were successfully performed in the presence of 3 mol % of Pd(PPh3)4 catalyst at 100 °C. 相似文献
30.