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排序方式: 共有354条查询结果,搜索用时 15 毫秒
91.
将大气压光电离(APPI)、电喷雾(ESI)、实时直接分析(DART)多种电离源和傅立叶变换离子回旋共振质谱(FT-ICR MS)联用对石油芳烃样品中的未知化合物进行研究。通过高分辨质谱的精确质量,结合碰撞诱导解离(CAD)技术,经分析并与文献标准物质谱图比对,推断未知物为三(2,4-二-叔丁基苯基)磷酸酯(TDTBPP),并研究了其在不同大气压电离源中的电离特性。APPI谱图中主要为[M+H]~+峰,同时存在M.~+峰。ESI谱图中主要为[M+Na]~+(不加甲酸)或[M+NH4]~+峰(加甲酸)。DART谱图中主要为[M+NH4]~+峰,而EI谱图中基峰为m/z 57(叔丁基),次强峰为[M-CH3]~+峰。 相似文献
92.
Jun Chen Maoqi Cao Bin Wei Mengmeng Ding Xiaobin Shan Fuyi Liu Liusi Sheng 《Journal of mass spectrometry : JMS》2016,51(2):169-181
In this work, photoionization and dissociation of cyclohexene have been studied by means of coupling a reflectron time‐of‐flight mass spectrometer with the tunable vacuum ultraviolet (VUV) synchrotron radiation. The adiabatic ionization energy of cyclohexene as well as the appearance energies of its fragment ions C6H9+, C6H7+, C5H7+, C5H5+, C4H6+, C4H5+, C3H5+ and C3H3+ were derived from the onset of the photoionization efficiency (PIE) curves. The optimized structures for the transition states and intermediates on the ground state potential energy surfaces related to photodissociation of cyclohexene were characterized at the ωB97X‐D/6‐31+g(d,p) level. The coupled cluster method, CCSD(T)/cc‐pVTZ, was employed to calculate the corresponding energies with the zero‐point energy corrections by the ωB97X‐D/6‐31+g(d,p) approach. Combining experimental and theoretical results, possible formation pathways of the fragment ions were proposed and discussed in detail. The retro‐Cope rearrangement was found to play a crucial role in the formation of C4H6+, C4H5+ and C3H5+. Intramolecular hydrogen migrations were observed as dominant processes in most of the fragmentation pathways of cyclohexene. The present research provides a clear picture of the photoionization and dissociation processes of cyclohexene in the 8‐ to 15.5‐eV photon energy region. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
93.
D. D. Coon S. D. Gunapala R. P. G. Karunasiri H. -M. Muehlhoff 《International Journal of Infrared and Millimeter Waves》1984,5(2):197-205
Recently we have described a new mode of IR detection which utilizes charge storage in localized levels of an extrinsic semiconductor at low temperatures. This method is based on field-assisted impurity photoionization. IR photoionization depletes the population of stored charge in localized impurity states. The integration takes place inside the bulk of the semiconductor. A large negative going pulse causes rapid field ionization of the remaining charge after an IR exposure. Readout is accomplished by measuring this ejected charge. Using a cryogenically cooled monochromator, we have studied the spectral response and its field dependence. Extremely low dark currents (<3×10–18 A) permit IR integration times of up to 12 hours or more. For the first time, significant photoresponse is obtained from a cryogenic Si:P detector at wavelengths up to 43 m, well beyond the nominal long wavelength cutoff of 27 m.This work was supported in part by National Science Foundation grant #ECS-8202473. 相似文献
94.
ZHU Hongping ZHANG Zhaoxia ZHAO Hongwei WANG Wenfeng & YAO Side . Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai China . Graduate University of the Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2006,49(4):308-314
Reactive oxygen species (ROS) are generated dur- ing radiation, respiratory burst, normal metabolic processes and so on. There are enzymatic and non-enzymatic antioxidants such as superoxide dis- mutase (SOD), glutathione peroxidase (GSH-Px), vi- tamin E (VE) and carotenoids that can either inhibit or repair the ROS-induced damage. ROS is essential to maintain physiological homeostasis. However, exces- sive ROS give rise to oxidative damage to proteins, lipids and DNA which related t… 相似文献
95.
96.
用合肥国家同步辐射实验室光化学站的实验装置研究了苯分子的光电离质谱,从所得光电离效率谱精确地定出了苯分子的电离势及苯离子的出现热,并首次报道了三个苯离子的离解能。 相似文献
97.
98.
在Dirac-Slater相对论理论框架下,研究了HCI(高离化态离子)的基本性质及其光电离过程的基本特征. 通常HCI的电场非常强,其电子波函数沿靠近核的径向空间被压缩,这极大地改变了相应的物质的性质,使HCI的光电离过程与一般的原子(离子)的相比较有很大的不同:原子核的尺寸效应和相对论效应变得更加重要,而多极效应对光电离截面的影响却趋于减弱. 相似文献
99.
We investigate the ionization dynamics of atoms by chirped
attosecond pulses using the strong field approximation method. The
pulse parameters are carefully chosen in the regime where the strong
field approximation method is valid. We analyse the effects of the
chirp of attosecond pulses on the energy distributions and the
corresponding left-right asymmetry of the ionized electrons. For a
single chirped attosecond pulse, the ionized electrons can be
redistributed and the left-right asymmetry shows oscillations
because of the introduction of the chirp. For time-delayed double
attosecond pulses at different intensities with the weaker one
chirped, exchanging the order of the two pulses shows a relative
shift of the energy spectra, which can be explained by the different
effective time delays of different frequency components because of
the chirp. 相似文献
100.