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71.
72.
Kohei Mishima Daiki Kaji Prof. Dr. Michiya Fujiki Prof. Dr. Yoshitane Imai 《Chemphyschem》2021,22(17):1728-1737
Herein, magnetic circularly polarized luminescence (CPL) (MCPL) spectroscopy was conducted to analyze an EuIII(hfa)3 complex with three chiral PIII-ligands. Resultantly, (R)-chirality luminophores with S-up orientation and (S)-chirality luminophores with N-up orientation were observed to possess symmetrical mirror image spectra, i. e., they were enantiomers. Similarly, the (R)-chirality luminophores with N-up orientation and the (S)-chirality luminophores with S-up orientation were also enantiomers. Contrarily, (R)-S-up and (S)-S-up were diastereomers and did not possess a mirror-image relationship. Likewise, (R)-N-up and (S)-N-up were diastereomers. The J-dependency of gMCPL and gCPL datasets suggested that the N-up/S-up external magnetic field, with the aid of chiral PIII-ligands, increased the gMCPL values by two- to sixteen-fold and modulated the gMCPL signs at J=1–4. Additionally, the origins of the nonideal mirror-symmetric CPL and MCPL spectral characteristics of EuIII(hfa)3 with three chiral PIII-ligands were discussed in terms of parity (space-inversion, P)-symmetry, time-reversal (T)-symmetry, and PT-symmetry laws. 相似文献
73.
Kouhei Watanabe Ayano Taniguchi Daiki Kaji Nobuyuki Hara Tomomasa Hosoya Aoba Kanesaka Takunori Harada Hiroyuki Nishikawa Yoshitane Imai 《Tetrahedron》2019,75(21):2944-2948
Organic fluorescent molecules are gaining importance because of their potential applications in many devices. Optically active N,N′-bis((1R)-1-naphthylethyl)perylene-3,4,9,10-tetracarboxylic diimide [(R,R)-1-BNP] and N,N′-bis((1R)-2-naphthylethyl)perylene-3,4,9,10-tetracarboxylic diimide [(R,R)-2-BNP] and their antipode, [(S,S)-1-BNP and (S,S)-2-BNP], emit aggregation-induced enhanced (AIEnh) circularly polarized luminescence (CPL) on both a solid organic polymer film (poly(methyl methacrylate)) and solid inorganic KBr pellet. An opposite chirality is essential for generating CPL of inverted sign. However, a pair of enantiomeric organic molecules may not always be easy to prepare. Interestingly, the chiral perylene fluorophores synthesized in this study can emit both positive and negative AIEnh-CPL in the solid state, depending on their position on the naphthylene groups. In addition, no CPL was observed in these compounds from their dilute solutions. 相似文献
74.
Prof. Shuichi Nakamura Daiki Hayama 《Angewandte Chemie (International ed. in English)》2017,56(30):8785-8789
The first highly enantioselective nucleophilic addition reaction of phosphites with 2H-azirines has been developed. The reaction was applied to various 3-substituted 2H-azirines using novel chiral bis(imidazoline)/ZnII catalysts to afford products in good yield with high enantioselectivity. The transformation of the obtained optically active aziridines showed that 2H-azirines act as either α,β- or β,β-dicarbocationic amine synthons. 相似文献
75.
Yuko Ichiyanagi Yuki Moro Hikaru Katayanagi Shinji Kimura Daiki Shigeoka Tomoyuki Hiroki Toshiyuki Mashino 《Journal of Thermal Analysis and Calorimetry》2010,99(1):83-86
Magnetic nanoparticles were prepared by a wet chemical method. Precursors of MFe2O4 (M = Co, Mn, Zn) were prepared from a mixture of metal chloride and metasilicate nonahydrate aqueous solutions. The precipitates
obtained in the wet chemical method were calcined to obtain MFe2O4 nanoparticles encapsulated by amorphous SiO2. The blocking temperatures T
B’s were between 20 and 320 K, in this temperature range, the anisotropy energy of the particles decreased below their thermal
energy. T
B increased with the particle size. In order to clarify the nanoparticle formation process, differential thermal analysis and
thermogravimetric (TG-DTA) measurements were performed for the as-prepared samples. 相似文献
76.
Yoshihide Usami Yumika Kubo Toshiki Takagaki Nao Kuroiwa Jun Ono Kohei Nishikawa Ayaka Nakamizu Yuya Tatsui Shinya Harusawa Noboru Hayama Hiroki Yoneyama 《Molecules (Basel, Switzerland)》2021,26(11)
The direct 4-alkoxylation of 4-iodo-1H-pyrazoles with alcohols was achieved by a CuI-catalyzed coupling protocol. The optimal reaction conditions employed excess alcohol and potassium t-butoxide (2 equiv) in the presence of CuI (20 mol%) and 3,4,7,8-tetramethyl-1,10-phenanthroline (20 mol%) at 130 °C for 1 h under microwave irradiation. The present method was efficiently applied to the synthesis of withasomnine and its six- and seven-membered cyclic homologs. 相似文献
77.
Kentaro Yoshimura Lee Chuin Chen Daiki Asakawa Kenzo Hiraoka Sen Takeda 《Journal of mass spectrometry : JMS》2009,44(6):978-985
Probe electrospray ionization (PESI) is a recently developed technique that uses a fine solid needle as a probe for sampling biological materials. In this study, we quantified the volume of liquid sample picked up by the solid needle with the tip diameter of ~700 nm and the apex angle of ~60°. The amounts of low‐viscosity samples (rat urine) loaded on the tip of the needle by a single stroke were 0.35 ± 0.09 pl. Interestingly, the amount of liquid adhered to the tip did not significantly depend on the protein concentration, but viscosity and surface tension of the sample. Under these conditions, we successfully obtained mass spectra for each biological sample. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
78.
A new ionization method, electrospray droplet impact ionization (EDI), has been developed for matrix-free secondary-ion mass spectrometry (SIMS). The charged droplets formed by electrospraying 1 M acetic acid aqueous solution are sampled through an orifice with a diameter of 400 microm into the first vacuum chamber, transported into a quadrupole ion guide, and accelerated by 10 kV after exiting the ion guide. The droplets impact on a dry solid sample (no matrix used) deposited on a stainless steel substrate. The secondary ions formed by the impact are transported to a second quadrupole ion guide and mass-analyzed by an orthogonal time-of-flight mass spectrometer (TOF-MS). Ten pmol of gramicidin S could be detected with the presence of as much as 10 nmol of NaCl. The ion signal for arginine disappeared with decrease in the substrate temperature below 150 K owing to the formation of ice film over the sample surface. While 10 fmol of gramicidin S could be detected for 30 min, the ionization/desorption efficiency for EDI becomes smaller with an increase in the molecular weight (MW) of a biological sample. The largest protein samples detected to date are cytochrome c and lysozyme. The high sensitivity for EDI is due to the fact that samples only a few monolayers thick are subject to desorption/ionization by EDI, with little fragmentation. A coherent phonon excitation may be the main mechanism for the desorption/ionization of the solid sample. 相似文献
79.
Kawabata T Matsuda S Kawakami S Monguchi D Moriyama K 《Journal of the American Chemical Society》2006,128(48):15394-15395
An enantiodivergent asymmetric cyclization of N-Boc-N-omega-bromoalkyl-alpha-amino acid derivatives has been developed. With potassium amide bases in DMF, cyclization proceeds with retention of configuration, while inversion of configuration was observed with lithium amide bases in THF. Chirality of the parent amino acids was preserved during enolate formation and cyclization to give aza-cyclic amino acids in up to 98% ee with retention of configuration or inversion of configuration, depending on the reaction conditions. Thus, both enantiomers of cyclic amino acids with a tetrasubstituted stereocenter were prepared in high enantiomeric purity from readily available l-alpha-amino acids. This protocol is also applicable to a spirocyclization and an intramolecular conjugate addition of alpha-amino acid derivatives, giving either of the enantiomers of a diazaspiro compound and a tetrahydroisoquinoline derivative, respectively, in up to 99% ee. 相似文献
80.
Kenichiro Todoroki Hiroki Hashimoto Tomohiko Mikawa Miki Itoyama Tadashi Hayama Eijiro Kojima Hideyuki Yoshida Hitoshi Nohta Masatoshi Yamaguchi 《Analytical and bioanalytical chemistry》2010,397(6):2409-2416
We developed a fluorous scavenging–derivatization method for reagent peak-free liquid chromatography (LC)–fluorescence analysis
of carboxylic acids. In this method, carboxylic acids were fluorescently derivatized with 1-pyrenemethylamine in the presence
of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 1-hydroxy-1H-benzotriazole. Residual excess unreacted reagent was tagged with 2-(perfluorooctyl)ethyl isocyanate and could be selectively
removed by microfluorous solid-phase extraction before LC analysis. With use of this method, eight fluorescent derivatives
of linear aliphatic carboxylic acids (C1–C8) can be separated within 30 min by reversed-phase LC with gradient elution. In the chromatogram obtained, the fluorous-tagged
unreacted reagent peak is greatly decreased after microfluorous solid-phase extraction and does not interfere with the quantification
of each acid. With use of microfluorous solid-phase extraction with 80% (v/v) aqueous methanol elution, over 99.9% of the
unreacted fluorescent reagent was removed. The detection limits (signal-to-noise ratio of 3) for the carboxylic acids examined
are 2.3–8.0 fmol per 10-μL injection. We also applied this method successfully to the analysis of highly polar carboxylic
acids such as α-keto acids and tricarboxylic acid cycle metabolites. 相似文献