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51.
The structural parameters of the effective r g configuration of the LaI3 molecule were calculated using the DFT/B3LYP method. The difference between the calculated values of r e (La-I) and r g (La-I) is mostly due to the anharmonicity of the ν1 and ν2 vibrations and does not exceed the error in determining the distance r g (La-I) in the electron diffraction experiment. Inclusion of the anharmonicity of the ν2 and ν4 deformation vibrations in calculations leads to decreased amplitudes l(I…I) and shrinking effect δ(I…I) compared to the respective values obtained in the harmonic approximation. The LaI3 molecule proved to be more rigid than predicted by B3LYP calculations. 相似文献
52.
Free vibration problems of lattice sandwich beams under several typical boundary conditions are investigated in the present paper. The lattice sandwich beam is transformed to an equivalent homogeneous three-layered sandwich beam. Unlike the traditional analytical model in which the rotation angles of the face sheets and the core are assumed the same, different rotation angles are considered in this paper to characterize the real response of sandwich beams. The analytical solutions of the natural frequencies for several typical boundary conditions are obtained. The effects of material properties and geometric parameters on the natural frequencies are also investigated. 相似文献
53.
George Pitsevich Elena Shalamberidze Alex Malevich Valdas Sablinskas Vytautas Balevicius Lars G. M. Pettersson 《Molecular physics》2017,115(20):2605-2613
The frequencies and intensities of vibration–rotational transitions of water molecules in an argon matrix were calculated for temperatures of 6 and 30 K. The rigid asymmetric top approximation was used with available literature values of the effective rotational constants in the ground and excited vibrational states. The calculations were carried out by taking into account the existence of a non-equilibrium population distribution between the rotational levels of ortho- and para-water isomers. It was assumed that the temperature relaxation of the population of rotational levels is independent of the ortho- and para-isomers. Comparison of the results of the theoretical calculations with experimental literature data shows good agreement for the majority of the rotational structure lines for symmetric and antisymmetric stretching vibrations both in the frequency values and in the values of the relative intensities. 相似文献
54.
The dynamic string motion, which displacement is unilaterally constrained by the rigid termination condition of an arbitrary geometry has been simulated and analyzed. The treble strings of a grand piano usually terminate at a capo bar, which is situated above the strings. The apex of a V-shaped section of the capo bar defines the end of the speaking length of the strings. A numerical calculation based on the traveling wave solution is proposed for modeling the nonlinearity inducing interactions between the vibrating string and the contact condition at the point of string termination. It was shown that the lossless string vibrates in two distinct vibration regimes. In the beginning the string starts to interact in a nonlinear fashion with the rigid terminator, and the resulting string motion is aperiodic. Consequently, the spectrum of the string motion depends on the amplitude of string vibrations, and its spectral structure changes continuously with the passage of time. The duration of that vibration regime depends on the geometry of the terminator. After some time of aperiodic vibration, the string vibrations settle in a periodic regime where the resulting spectrum remains constant. 相似文献
55.
Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) were employed to study the microstructure of self-reinforced high-density polyethylene (HDPE) prepared by conventional injection molding (CIM) and a low frequency vibration-assisted injection molding (VAIM). SEM micrographs following permanganic etching showed the self-reinforcement of HDPE is mainly due to the existence of shish-kebab morphology within the core region for VAIM-processed HDPE samples. Pronounced molecular alignment was identified by the WAXD data. An approximate 9% increase in the crystallinity was confirmed by DSC. Both preferred molecular orientation and increased crystallinity serve to yield stronger VAIM-processed injection moldings. 相似文献
56.
The secondary radiation after resonant excitation of F center and its linear polarization P correlated to the polarization of resonant light have been measured for five alkali halides at low temperatures. In KC1, the spectrum of P over the whole Stokes region is divided into three successive regions, the depolarization range at the one-phonon Raman scattering, the near plateau range, and the depolarization range down to vanishing. The former two have common relevance to resonant energy and symmetries of coupled phonons. These relevances are interpreted adopting a configuration coordinate model for 2s- and 2p-like excited states. 相似文献
57.
《合成通讯》2013,43(11):2117-2126
Abstract Solvent‐free reactions of C60 and C70 with diethyl bromomalonate in the presence of various inorganic bases were investigated under the high‐speed vibration milling (HSVM) conditions, and are shown to give methanofullerenes 1 and 2 in good to excellent yields based on consumed fullerenes. Several weak inorganic bases were found to be quite effective in promoting the solvent‐free mechanochemical Bingel reactions of C60 and C70 under the HSVM conditions. Among the studied bases, sodium acetate gave the highest yield of monoadducts, while potassium carbonate afforded a considerable amount of bisadducts for both C60 and C70. 相似文献
58.
Andreas Braeuer Robert Fabian Hankel Markus Konstantin Mehnert Julian Jonathan Schuster Stefan Will 《Journal of Raman spectroscopy : JRS》2015,46(11):1145-1149
We report a Raman technique applicable for the in situ analysis of the development of hydrogen bonds in the liquid water‐rich phase just before the onset of gas hydrate formation. Herewith, the phase transition as well as the working principle of hydrate formation inhibitors and promoters can be analyzed. © 2015 The Authors. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd. 相似文献
59.
负热膨胀(NTE)是一种反常的物理现象, 已在合金和框架结构化合物等材料中被观察到, 但NTE材料的种类仍然有限. 本文合成了一种单轴NTE材料Zn(NCN), 该材料在c轴方向及在100~475 K下的热膨胀系数为-3.35×10?6 K?1, 而a轴和b轴方向则呈低热膨胀性, 体积具有低的热膨胀系数[6.13×10?6 K?1(100~475 K)]. 通过同步辐射X射线衍射、 扩展X射线吸收精细结构和拉曼光谱等方法, 研究了Zn(NCN)的NTE机理. 结果表明, Zn—N键具有明显的横向振动, 一些低频振动模Grüneisen参数为负值. 直接的实验证据表明, N=C=N的横向振动以及准刚性ZnN4四面体的耦合旋转和扭摆导致了c轴方向的NTE. 相似文献
60.
Hua Lei Meixuan Wu Ying Liu Fan Mo Jiayao Chen Shilong Ji Yan Zou Xiaoping Dong 《中国化学快报》2021,32(7):2317-2321
Photocatalysis technology has been proved to be a potential strategy for removal of organic dyes, however high-power light sources are generally necessary to initiate photocatalytic reaction. In this work, we employed an excellent photocatalyst of Bi2WO6 with visible light harvest and meanwhile an intrinsic ferroelectricity, which realized the efficient degradation of organic dye via the synergetic photopiezocatalysis. Through coupling the illumination by a low-power (9 W) LED and the ultrasonic vibration (120 W) by an ultrasonic cleaner, the nanoflower-like Bi2WO6 composed of ultrathin nanosheets showed a much more enhanced photopiezocatalysis performance for purification of organic dye than the individual photocatalysis and piezocatalysis. Furthermore, the high mineralization efficiency and the good durability of the Bi2WO6 catalyst were demonstrated. The possible mechanism of photopiezocatalysis was finally proposed, where the ultrasound-induced piezoelectric field in Bi2WO6 drove photo-generated electrons and holes to diffuse along opposite directions, consequently promoting the separation efficiency of charge carriers. This work indicates that the synergetic photopiezocatalysis by coupling irradiation and ultrasonic vibration is a promising strategy to purify organic pollutants in wastewater. 相似文献