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Hiroyuki Oku Hitoshi Ohashi Jun Fujimoto Masayuki Shimizu Masaru Yoshida Ryoichi Katakai 《Journal of polymer science. Part A, Polymer chemistry》2000,38(24):4524-4530
Poly(acryloyl‐L ‐proline‐methyl ester) ( 1 ) has optically active side chain, and constitutes thermoresponsive hydrogels upon crosslinking. In this study, we have prepared uncrosslinked polymer of 1 with a 10‐kGy irradiation dose of γ‐ray. For this polymer, 1 , variable temperature circular dichroism (CD) and 1H NMR spectra have been studied in the range of 0–30 °C. The intense CD spectrum at 0 °C suggests that the side chains in 1 have an ordered orientation. The CD intensity decreases gradually with increasing temperature. The decreased intensity of CD spectra indicates that the disordering occurs for the side‐chain orientation. The CD band shape changes discontinuously at 20 °C. In the 1H NMR spectra, signals disappear above 20 °C. These spectral change at 20 °C indicate that the phase transition occurs at around 20 °C from swollen to shrunken phase. Even after the phase transition, the CD spectra are still changing with isochromic point at 212 nm. It appears that the side‐chain conformation is still changing from one state to the other state in the shrunken phase polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4524–4530, 2000 相似文献
776.
Hiroyuki Oku Jun Fujimoto Takafumi Ohyama Akihiro Hiroki Masaru Yoshida Ryoichi Katakai 《Journal of polymer science. Part A, Polymer chemistry》2000,38(15):2671-2677
Poly(methacryloyl‐L ‐alanine‐methyl ester) (1) has an optically active side chain and consists of thermoshrinking hydrogels upon crosslinking. We synthesized an uncrosslinked polymer of 1 by the γ‐ray polymerization method. For the prepared polymer, variable‐temperature circular dichroism (CD) and 1H NMR spectra were studied, and we found conformational changes in the optically active side chains during the thermally induced phase transition. Intense CD spectra reveal ordered conformation in the side chain of 1 below the phase transition temperature (∼28 °C). A well‐resolved 1H NMR spectrum of 1 at 0 °C shows that the conformational angles in the polymer side chain are fixed at low‐energy minima. With increasing temperature, the frozen side chain starts rotating vigorously and takes an unordered orientation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2671–2677, 2000 相似文献
777.
Masaru Kitagawa Shinsuke Takegami Yutaka Tokiwa 《Macromolecular rapid communications》1998,19(3):155-158
To develop a new synthetic polymer containing sugar branches, radical polymerization of the reducing vinyl sugar ester 6-O-vinyladipoyl-D -glucose ( 1 ) was performed in an organic solvent or in water. The polymers obtained with several azoinitiators in dimethylformamide (DMF) showed comparatively low average molecular weight (M̄n ≈ 4500). In contrast, the use of a redox initiator (FeSO4 and H2O2) in water gave polymers of higher average molecular weight (M̄n ≈ 33000) in higher yield (90%), followed by crosslinking at high conversions. 相似文献
778.
K. C. Nicolaou Nareshkumar F. Jain Swaminathan Natarajan Robert Hughes Michael E. Solomon Hui Li Joshi M. Ramanjulu Masaru Takayanagi Alexandros E. Koumbis Toshikazu Bando 《Angewandte Chemie (International ed. in English)》1998,37(19):2714-2716
A triazene-based synthetic strategy for the construction of the complex biaryl ethers and a Suzuki coupling reaction were the key steps in the synthesis of precursor 1 of the aglycon of vancomycin, which already contains the complete skeleton of the target compound. The cleavage of the triazene unit from the D ring and the removal of the other protecting groups led to the aglycon of vancomycin. These strategies should be particularly valuable for the synthesis of other naturally occurring glycopeptide antibiotics and offer opportunities for the synthesis of combinatorial libraries of compounds of the vancomycin family for chemical biology studies. 相似文献
779.
Natsumi Koga Dr. Masaru Tanioka Prof. Dr. Shinichiro Kamino Prof. Dr. Daisuke Sawada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(11):3761-3765
Superior pH-responsive molecules are required for the development of functional materials applicable to advanced molecular technologies. Despite having been widely developed, many rhodamine-based pH-responsive molecules exhibit a single configurational switch for “turn-on”. Herein, we report a new type of rhodamine-based pH-responsive molecule with multi-configurational switches displaying stable two-step structural and color conversion in response to pH. This rhodamine analogue could be successfully applied to optical sensing of pH gradient under extreme acidic environments both in solution and on hydrogel through high-contrast color change. We demonstrated that this multi-responsive character enabled optical memory of different pH information. 相似文献
780.
Kun'ichi Miyazawa Takuro Nagai Koji Kimoto Masaru Yoshitake Yumi Tanaka 《Surface and interface analysis : SIA》2020,52(1-2):23-33
A glassy carbon (GC) substrate was irradiated by Pt ions using a coaxial arc plasma gun in vacuum. The structure of the substrate was studied in the atomic scale using high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) with a thin foil specimen prepared by cross-sectioning using focused ion beam milling. HRTEM combined with the EELS measurements of the cross-sectioned sample indicated a disordering of the GC substrate surface and the detection of phenol-type species, carbon atoms in aliphatic chain molecules, and carboxyl groups, which are considered to have been formed by chemical reaction between the carbon atoms of the GC substrate surface and hydrogen or oxygen atoms. Penetrated Pt atoms were observed inside the GC substrate, and the surface position of the GC substrate was located from the depth profiles of the EELS spectra. STEM-EELS analyses of a pristine GC substrate without Pt ion irradiation were also conducted for reference. 相似文献