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361.
Takaya Murakami Yoshiaki Iwamuro Reiko Ishimaru Satoshi Chinaka Noriyuki Kato Yuki Sakamoto Natsuhiko Sugimura Hiroshi Hasegawa 《Journal of mass spectrometry : JMS》2019,54(3):205-212
A reliable method for structural analysis is crucial for the forensic investigation of new psychoactive substances (NPSs). Towards this end, mass spectrometry is one of the most efficient and facile methods for the identification of NPSs. However, the differentiation among 2‐, 3‐, and 4‐fluoromethcathinones (o‐, m‐, and p‐FMCs), which are ring‐fluorinated positional isomers part of the major class of NPSs referred to as synthetic cathinones, remains a challenge. This is mostly due to their similar retention properties and nearly identical full scan mass spectra, which hinder their identification. In this study, we describe a novel and practical method for differentiating the fluorine substitution position on the phenyl ring of FMCs, based on energy‐resolved mass spectrometry (ERMS) using an electron ionization‐triple quadrupole mass spectrometer. ERMS measurements showed that the three FMC positional isomers exhibited differences in relative abundances of both the fluorophenyl cation (m/z 95) and the fluorobenzoyl cation (m/z 123). The logarithmic plots of the abundance ratio of these two cations (m/z 95 to m/z 123) as a function of the collision energy (CE) followed the order of o‐FMC < p‐FMC < m‐FMC at each CE, which allowed the three isomers to be unambiguously and reliably differentiated. The theoretical dissociation energy calculations confirmed the relationship obtained by ERMS analyses, and additional ERMS measurements of methylmethcathinone positional isomers showed that the differences in abundance among the FMCs were attributed to the differences in their collision‐induced dissociation reactivities arising from the halogen‐induced resonance effects on the phenyl ring. Moreover, the method for differentiation described herein was successfully applied to the actual samples containing seized drugs. We expect that the described methodology will also contribute significantly to the reliable and accurate structural identification of NPSs in the fields of therapeutic, clinical, and forensic toxicology. 相似文献
362.
Mori M Wakamatsu H Tonogaki K Fujita R Kitamura T Sato Y 《The Journal of organic chemistry》2005,70(3):1066-1069
Isoquinoline derivatives were synthesized from cyclobutenylmethylamine derivatives having an alkyne moiety in a tether using a second-generation ruthenium carbene complex under ethylene gas in good yields. 相似文献
363.
Mixing behavior of hydrogenated and fluorinated cationic gemini surfactants was studied at the air-water interface by Brewster angle microscopy and pi-A isotherm curves. In the bulk, these two molecules did not mix and showed phase separation. At the air-water interface, if a monolayer was formed by separate deposition of the two solutions, they formed separate domains, and the compression occurred in two steps: first the domains with hydrogenated gemini surfactant were compressed until they showed collapse; then the domains with fluorinated gemini surfactant were compressed. If the two solutions were mixed before the deposition, they remained mixed upon compression; on the other hand, separate domains under separate deposition were shown to mix if the subphase was heated. 相似文献
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366.
The bimolecular reactions in the title were measured behind shock waves by monitoring the O-atom production in COS? O2? Ar and CS2? O2? Ar mixtures over the temperature range between 1400 and 2200 K. A value of the rate constant for S + O2 → SO + O was evaluated to be (3.8 ± 0.7) × 1012 cm3 mol?1 s?1 between 1900 and 2200 K. This was connected with the data at lower temperatures to give an expression k2 = 1010.85 T0.52 cm3 mol?1 s?1 between 250 and 2200 K. An expression of the rate constant for CS2 + O2 → CS + SO2 was obtained to be k21 = 1012.0 exp(?32 kcal mol?1/RT) cm3 mol?1 s?1 with an error factor of 2 between 1500 and 2100 K. 相似文献
367.
Site-specific introduction of sialic acid into insulin 总被引:1,自引:0,他引:1
Sato M Sadamoto R Niikura K Monde K Kondo H Nishimura S 《Angewandte Chemie (International ed. in English)》2004,43(12):1516-1520
368.
We experimentally investigated spatiotemporal patterns in chains of coupled biological oscillators with boundaries and found hidden symmetric patterns that are not straightforwardly derived from explicit geometrical symmetry of the systems. We propose a model of coupled oscillators in chains with a hidden oscillator interconnecting its boundaries. The model can explain all observed patterns including the hidden symmetric ones, while other models such as discrete analogs of Neumann boundary conditions in continuous systems cannot. 相似文献
369.
In the title reaction, eight vic-dibromides and three vinylene dibromides gave the corresponding debromination products (alkenes and alkynes) at room temperature under neutral condition and an argon atmosphere. 2,3-Dibromosuccinic acid derivatives gave overreduction products or an unusual coupling dimer. 相似文献
370.
Various modified guanine derivatives were synthesized and introduced into G(4) of d(CGCGCG)(2) to evaluate their capacity to stabilize Z-form DNA. It was found that the incorporation of 8-methylguanosine (m(8)rG) in oligonucleotides stabilizes the Z form more dramatically than does the incorporation of 8-methyl-2'-deoxyguanosine (m(8)G). This enhancement is ascribed to a reduction in the entropic penalty, which arises from the introduction of hydrophilic groups in solvent-exposed regions. The incorporation of m(8)rG into DNA sequences markedly stabilizes the Z form even in the absence of NaCl. The Z-DNA stabilizer allows oligonucleotides with a wide range of sequences to be converted to the Z form. It could be a powerful tool for examining the molecular basis of many types of Z-form-specific reactions at the molecular level under physiological salt conditions. 相似文献