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81.
Tomohiro Hirano Shuhei Masuda Shou Nasu Koichi Ute Tsuneyuki Sato 《Journal of polymer science. Part A, Polymer chemistry》2009,47(4):1192-1203
Radical polymerization of N,N‐dimethylacrylamide (DMAAm) was investigated in the presence of tartrates, such as diethyl L ‐tartrate, diisopropyl L ‐tartrate, and di‐n‐butyl L ‐tartrate, in toluene at low temperatures. Syndiotactic polymers were obtained in the presence of tartrates, whereas isotactic polymers were obtained in the absence of tartrates. The syndiotactic‐specificity increased with increasing amount of tartrates and with decreasing polymerization temperature. NMR analysis suggested that DMAAm and tartrates formed a 1:1 complex through double hydrogen bonding. A mechanism for the syndiotactic‐specific radical polymerization of DMAAm is proposed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1192–1203, 2009 相似文献
82.
Tomohiro Hirano Shou Nasu Akihiro Morikami Koichi Ute 《Journal of polymer science. Part A, Polymer chemistry》2009,47(23):6534-6539
Radical polymerization of N‐methylacrylamide (NMAAm), N,N‐dimethylacrylamide (DMAAm), and N‐methyl‐N‐phenylacrylamide (MPhAAm) was investigated in toluene at low temperatures. Atactic, isotactic, and syndiotactic polymers were obtained by the polymerization of NMAAm, DMAAm, and MPhAAm, respectively, indicating that the stereospecificity of the radical polymerization of acrylamide derivatives depended on the N‐substituents of the monomer used. From the viewpoint of monomer structure, the origin of the stereospecificity of radical polymerization of NMAAm derivatives is discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6534–6539, 2009 相似文献
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85.
Andrei V. Afonin Dmitry V. Pavlov Igor A. Ushakov Natalia A. Keiko 《Magnetic resonance in chemistry : MRC》2012,50(7):502-510
In the 13C NMR spectra of methylglyoxal bisdimethylhydrazone, the 13C‐5 signal is shifted to higher frequencies, while the 13C‐6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the 1H‐6 chemical shift and 1J(C‐6,H‐6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the –CH═N– bond does not change. This paradox can be rationalized by the C–H?N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum‐chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ(1H‐6) and 1J(C‐6,H‐6) parameters. The effect of the C–H?N hydrogen bond on the 1H shielding and one‐bond 13C–1H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The 1H, 13C and 15N chemical shifts of the 2‐ and 8‐(CH3)2N groups attached to the –C(CH3)═N– and –CH═N– moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8‐(CH3)2N group conjugate effectively with the π‐framework, and the 2‐(CH3)2N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N‐2– and N‐8– nitrogen lone pairs to the π‐framework varies, which affects the 1H, 13C and 15N shieldings. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
86.
Keiko Doi-Kawano Etsuko Nishimoto Yoshiaki Kouzuma Daisuke Takahashi Shoji Yamashita Makoto Kimura 《Journal of fluorescence》2009,19(4):631-639
The steady-state and time-resolved fluorescece spectroscopy is one of the most powerful method to detect and analyze subtle
conformation change and interaction between peptide elements in protein. Phytocystatin Scb isolated from sunflower seeds includes
a single Trp residue at position 85. In an attempt to investigate the interaction of the N-terminal region of Scb with the
first and second hairpin loops by fluorescence spectroscopy of Trp residue, two Scb mutants in which single Trp locates at
position 52 and 58, respectively, and their N-terminal removed mutants were generated. The N-terminal truncation changed the
fluorescence decay kinetics of Trp52 from the triple exponential to double. Furthermore, the time-resolved fluorescence anisotropy
residue indicated that the segmental motion of Trp52 was significantly enhanced by its N-terminal truncation. In contrast,
Trp58 and Trp85 had little influence. The N-terminal successive truncations of Scb and its mutants resulted in the weaken
inhibitors to papain. These results suggested that the N-terminal region of Scb interacts with the peptide segment preceding
the first hairpin loop, thereby stabilizing the conformation of the hairpin loop structure. 相似文献
87.
Using the57Fe conversion electron Mössbauer spectroscopy (CEMS), the structural and compositional changes at near surface of the amorphous Fe-13%B-9%Si and Fe-15%Cr-9%Ni stainless steel specimens have been clarified after the bombardment of 25kV accelerated He+ ions. 相似文献
88.
Atsuko Ito Keiko Iwai Chiyuki Oyama Setsu Morimoto Hiroaki Kato 《Hyperfine Interactions》1992,71(1-4):1371-1374
Magnetization and Mössbauer measurements have been made on a diluted antiferromagnets FexMg1?xTiO3 with x=0.2, 0.3 and 0.7. It has been demonstrated that this system exhibits a spin glass or a reentrant spin glass like behavior in the samples with x around the percolation concenrration xc≈0.25. It has been shown that various sizes of magnetic clusters are formed well above the transition temperatures determined by the magnetization measurements in the samples with x near xc. The behavior of Fe0.2Mg0.8TiO3 is discussed as a typical cluster glass. 相似文献
89.
S. Nasu M. Yoshida Y. Oda T. Kohara T. Shinjo K. Asayama F. E. Fujita S. Katsuyama Y. Ueda K. Kosuge 《Hyperfine Interactions》1991,66(1-4):417-421
The57Co emission Mössbauer spectra from YBa2Cu3O6.92 (1-2-307) and YBa2Cu3O6.00 (1-2-306) have been measured and compared with the57Fe absorption spectra from YBa2Cu2.95Fe0.05O7?δ in order to clarify decisively the site assignments for the57Fe quadrupole-split doublets in these compounds. Mössbauer spectra obtained from both specimens consist of four components whose hyperfine interaction parameters well agree with each other. It is shown that the Co and Fe atoms mainly substitute at Cu1 chain sites in 1-2-307, but in 1-2-306 the Co atoms occupy randomly the Cu2 plane sites and indicate magnetically-split sextet which converts to a paramagnetic doublet of S-state Fe3+ in 1-2-307 by a post-annealing in O2 gas. 相似文献
90.
Hyperfine Interactions - First off-line tests at the ion trap facility SHIPTRAP took place. The facility is being set up to deliver very clean and cooled beams of singly-charged recoil ions (Rare... 相似文献