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181.
Sage JT Durbin SM Sturhahn W Wharton DC Champion PM Hession P Sutter J Alp EE 《Physical review letters》2001,86(21):4966-4969
We report the complete vibrational spectrum of the probe nucleus 57Fe at the oxygen-binding site of the protein myoglobin. The Fe-pyrrole nitrogen stretching modes of the heme group, identified here, probe asymmetric interactions with the protein environment. Collective oscillations of the polypeptide, rather than localized heme vibrations, dominate the low frequency region. We conclude that the heme "doming" mode is significantly delocalized, so that distant sites respond to oxygen binding on vibrational time scales. This has ramifications for understanding long-range interactions in biomolecules, such as those that mediate cooperativity in allosteric proteins. 相似文献
182.
Bergmann U Sturhahn W Linn DE Jenney FE Adams MW Rupnik K Hales BJ Alp EE Mayse A Cramer SP 《Journal of the American Chemical Society》2003,125(14):4016-4017
Metal-hydrogen bonding is important in chemistry and catalysis, but H atoms are often difficult to observe, especially in metalloproteins. In this work we show that Fe-H interactions can be probed by nuclear resonance vibrational spectroscopy at the 14.4 keV 57Fe nuclear resonance. An important advantage of this method, compared to Raman and IR spectroscopy, is the selectivity for modes that involve 57Fe motion. We present data on the FeS4 site in rubredoxin and the [FeH(D)6]2- ion. Prospects for studying more complex systems are discussed. 相似文献
183.
Shvyd'ko YV Lerche M Wille HC Gerdau E Lucht M Rüter HD Alp EE Khachatryan R 《Physical review letters》2003,90(1):013904
We demonstrate an interferometer for hard x rays with two back-reflecting sapphire crystal mirrors--a prototype x-ray Fabry-Pérot interferometer. A finesse of 15 and 0.76 mu eV broad Fabry-Pérot transmission resonances are measured by the time response of the interferometer. Interference patterns are observed directly in spectral dependences of reflectivity. 相似文献
184.
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186.
The new 2-[2-(6-tert-butyl-2H-1,3-benzoxazin-3(4H)-yl)ethoxy]ethanol 1 and 2-[2-(6-pentyl-2H-1,3-benzoxazin-3(4H)-yl)ethoxy]ethanol 2 have been synthesized. Axially disubstituted silicon phthalocyanines 3 and 4 have been synthesized by introducing 2-[2-(6-tert-butyl-2H-1,3-benzoxazin-3(4H)-yl)ethoxy]ethanol and 2-[2-(6-pentyl-2H-1,3-benzoxazin-3(4H)-yl)ethoxy]ethanol at the axial positions of silicon(IV) phthalocyanine, respectively. The electrochemical properties of silicon phthalocyanines 3 and 4 were also investigated by cyclic voltammetry (CV) and square wave voltammetry. Voltammetric studies show that while 3 showed two reversible reduction and one irreversible oxidation couples, 4 showed two quasi-reversible reduction and one irreversible oxidation couples. 相似文献
187.
Smith MC Xiao Y Wang H George SJ Coucouvanis D Koutmos M Sturhahn W Alp EE Zhao J Cramer SP 《Inorganic chemistry》2005,44(16):5562-5570
[NEt(4)][FeCl(4)], [P(C(6)H(5))(4)][FeCl(4)], and [NEt(4)](2)[Fe(2)S(2)Cl(4)] have been examined using (57)Fe nuclear resonance vibrational spectroscopy (NRVS). These complexes serve as simple models for Fe-S clusters in metalloproteins. The (57)Fe partial vibrational density of states (PVDOS) spectra were interpreted by computation of the normal modes assuming Urey-Bradley force fields, using additional information from infrared and Raman spectra. Previously published force constants were used as initial values; the new constraints from NRVS frequencies and amplitudes were then used to refine the force field parameters in a nonlinear least-squares analysis. The normal-mode calculations were able to quantitatively reproduce both the frequencies and the amplitudes of the intramolecular-mode (57)Fe PVDOS. The optimized force constants for bending, stretching, and nonbonded interactions agree well with previously reported values. In addition, the NRVS technique also allowed clear observation of anion-cation lattice modes below 100 cm(-1) that are nontrivial to observe by conventional spectroscopies. These features were successfully reproduced, either by assuming whole-body motions of point-mass anions and cations or by simulations using all of the atoms in the unit cell. The advantages of a combined NRVS, Raman, and IR approach to characterization of Fe-S complexes are discussed. 相似文献
188.
The dehydration and decomposition of the red mud from Seydięehir Aluminum factory, mixed with soda were investigated under
dynamic and isothermal conditions. Soda was added to the red mud samples as much as 50, 100 and 150 mass% of Na2CO3 of the red mud sample's mass. To determine the effect of soda additive on the red mud's thermal properties, using TG and
DTA techniques simultaneously under atmospheric conditions. Furthermore, the original red mud sample's XRD and IR spectrum
curves were investigated. It seems that the temperatures of the endothermic peaks of the red mud decreased with the amount
of soda added. However the endothermic peak's temperature readings showed that the melting of soda increased gradually with
the quantity of soda used.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
189.
Zeng W Silvernail NJ Wharton DC Georgiev GY Leu BM Scheidt WR Zhao J Sturhahn W Alp EE Sage JT 《Journal of the American Chemical Society》2005,127(32):11200-11201
We use nuclear resonance vibrational spectroscopy (NRVS) to identify the Fe-NO stretching frequency in the NO adduct of myoglobin (MbNO) and in the related six-coordinate porphyrin Fe(TPP)(1-MeIm)(NO). Frequency shifts observed in MbNO Raman spectra upon isotopic substitution of Fe or the nitrosyl nitrogen confirm and extend the NRVS results. In contrast with previous assignments, the Fe-NO frequency of these six-coordinate complexes lies 70-100 cm-1 lower than in the analogous five-coordinate nitrosyl complexes, indicating a significant weakening of the Fe-NO bond in the presence of a trans imidazole ligand. This result supports proposed mechanisms for NO activation of heme proteins and underscores the value of NRVS as a direct probe of metal reactivity in complex biomolecules. 相似文献
190.