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61.
Vandana Bhalla Manoj Kumar Tetsutaro Hattori Sotaro Miyano 《Tetrahedron letters》2007,48(9):1581-1585
A series of thiacalixpodands and bisthiacalixarenes with imine units have been prepared by condensation of O,O″-bis(2-aminoethyl)-O′,O?-dipropyl-p-tert-butylthiacalix[4]arene of 1,3-alternate conformation with different aromatic (di)aldehydes. The molecules derived from pyridine-2-carbaldehyde and -2,6-dicarbaldehyde quantitatively extract silver ion from aqueous into organic phase with complete selectivity over other metal ions (Na+, K+ and Cs+) under neutral conditions. The former compound forms a 1:2 (L:M) complex with silver ion as proved by NMR spectroscopy, Job’s plot and X-ray crystallography. 相似文献
62.
63.
Tadaaki Isobe 《Acta Physica Hungarica A》2006,27(2-3):227-230
Neutral pions (π0) in √NN=200 GeV and 62.4 GeV Au+Au collisions were measured at RHIC-PHENIX Year-4 Run. In √NN=200 GeV, π0 spectra are measured up to p T=20 GeV/c. A strong suppression by a factor of ~5 is observed and stays almost constant up to 20 GeV/c. 相似文献
64.
Ultrafast melting of a charge-ordered state has been observed in the photo-irradiated colossal magnetoresistive compound Pr0.7Ca0.3MnO3. Pump-and-probe spectroscopy experiments reveal the formation of a conducting phase with typical features of an insulator–metal
transition (IMT) after less than 1 ps. This phase is metastable and can be maintained for about 1 μs unless it is stabilized
persistently into a pathlike metallic region by an electric field. Although laser-induced lattice heating may play a role
in the initial excitation, electronic correlations are the dominant effect which leads to the formation of the metallic state
upon the breakdown of the charge-ordered state.
Received: 26 January 2000 / Published online: 16 June 2000 相似文献
65.
A novel desalting method, using a column switching technique and a volatile ion-pairing reagent, pentadecafluorooctanoic acid, was developed. This system allows hydrophilic and cationic compounds in a nonvolatile buffer to be directly introduced into a mass spectrometer for structural elucidation. The desalting procedure consists of four steps: (1) the fractionation of a target compound from a separation column, (2) the removal of salts with pentadecafluorooctanoic acid on the trap column, (3) the desorption of the compound from the trap column, and (4) the re-equilibration of the trap column with a pentadecafluorooctanoic acid solution. In this procedure, we investigated the methods for optimizing the desalting and re-equilibration steps. Various amino acids, including branched chain amino acids, aromatic amino acids, basic amino acids and methionine, after separation with phosphate buffer on a cation-exchange column, were successively desalted by this method, and were observed as protonated ions by mass spectrometry. This desalting system could be useful for the structural elucidation of unknown hydrophilic compounds eluted by conventional high-performance liquid chromatography methods, such as ion-exchange chromatography, with mobile phases containing nonvolatile salts. As an example, we present the structural elucidation of unknown metabolites in bovine serum. 相似文献
66.
Nagano Y Liu JG Naruta Y Ikoma T Tero-Kubota S Kitagawa T 《Journal of the American Chemical Society》2006,128(45):14560-14570
Physicochemical properties of the covalently cross-linked tyrosine-histidine-Cu(B) (Tyr-His-Cu(B)) unit, which is a minimal model complex [M(II)-BIAIPBr]Br (M = Cu(II), Zn(II)) for the Cu(B) site of cytochrome c oxidase, were investigated with steady-state and transient absorption measurements, UV resonance Raman (UVRR) spectroscopy, X-band continuous-wave electron paramagnetic resonance (EPR) spectroscopy, and DFT calculations. The pH dependency of the absorption spectra reveals that the pK(a) of the phenolic hydroxyl is ca. 10 for the Cu(II) model complex (Cu(II)-BIAIP) in the ground state, which is similar to that of p-cresol (tyrosine), contrary to expectations. The bond between Cu(II) and nitrogen of cross-linked imidazole cleaves at pH 4.9. We have successfully obtained UVRR spectra of the phenoxyl radical form of BIAIPs and have assigned bands based on the previously reported isotope shifts of Im-Ph (2-(1-imidazoyl)-4-methylphenol) (Aki, M.; Ogura, T.; Naruta, Y.; Le, T. H.; Sato, T.; Kitagawa, T. J. Phys. Chem. A 2002, 106, 3436-3444) in combination with DFT calculations. The upshifts of the phenoxyl vibrational frequencies for 8a (C-C stretching), 7a' (C-O stretching), and 19a, and the Raman-intensity enhancements of 19b, 8b, and 14 modes indicate that UVRR spectra are highly sensitive to imidazole-phenol covalent linkage. Both transient absorption measurements and EPR spectra suggest that the Tyr-His-Cu(B) unit has only a minor effect on the electronic structure of the phenoxyl radical form, although our experimental results appear to indicate that the cross-linked Tyr radical exhibits no EPR. The role of the Tyr-His-Cu(B) unit in the enzyme is discussed in terms of the obtained spectroscopic parameters of the model complex. 相似文献
67.
Observation of a modulation effect caused by a microsphere resonator strongly coupled to a dielectric substrate 总被引:1,自引:0,他引:1
The effect of modulation caused by a microsphere resonator is experimentally investigated with a model system consisting of a microsphere resonator and a plane substrate. We used total internal reflection microscopy (TIRM), which is a combination of conventional optical microscopy and the total internal reflection method, and observed the intensity distribution under the resonator in the evanescent-wave incidence condition. The TIRM patterns drastically change when the wavelength of the incident beam is scanned across a resonance. The response of the system is discussed on the basis of a recent proposal of traveling-wave resonance. 相似文献
68.
Stuart D Breedon RE Chinitz LM Ko W Lander RL Rowe J Smith JR Kirk P Cheng CP Gao WX Yan WG Ye MH Abashian A Gotow K Haim D Mattson ME Morgan N Piilonen L Sterner KL Lusin S Rosenfeld C Wang AT Wilson S Zheng LY Fry CA Tanaka R Abe K Fujii Y Kurihara Y Liu F Maki A Nozaki T Omori T Sagawa H Sakai Y Sasaki T Sugimoto Y Takaiwa Y Terada S Walker R Kanda S Olsen SL Ueno K Kajino F Poling R Thomas T Aso T Miyano K Miyata H Oyoshi M Yamashita Y Lee MH Sannes F Schnetzer S Stone R Vinson J Bodek A 《Physical review D: Particles and fields》1994,49(7):3098-3105
69.
Liu F Chinitz LM Abe K Breedon RE Fujii Y Kurihara Y Maki A Nozaki T Omori T Sagawa H Sakai Y Sasaki T Sugimoto Y Takaiwa Y Terada S Kirk P Cheng CP Gao WX Yan WG Ye MH Abashian A Gotow K Mattson ME Piilonen L Sterner KL Lusin S Rosenfeld C Wilson S Zheng LY Fry CA Tanaka R Ko W Lander RL Rowe J Smith JR Stuart D Kanda S Olsen SL Ueno K Kajino F Poling R Thomas T Aso T Miyano K Miyata H Okubo K Oyoshi M Shirai M Yamashita Y Lee MH Sannes F Schnetzer S Stone R Vinson J Bodek A Kim BJ Kumita T 《Physical review D: Particles and fields》1994,49(9):4339-4347
70.
Hiroshi Takaku Ryuichi Yamaguchi Tadaaki Nomoto Tsujiaki Hata 《Tetrahedron letters》1979,20(40):3857-3860
5-Chloro-8-quinolyl group is found to be very suitable for the protecting group on phosphates in the internucleotidic bonds. The oligoribonucleotides were obtained in good yields by a simple procedure using this phosphate protecting group. 相似文献