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211.
Si Jia Li Zhuo Yue Li Guo Shai Huang Xiao Bin Liu Rui Qi Li Xiang Yu Cao 《Frontiers of Physics》2022,17(6):62501
Orbital angular momentum (OAM) is a phenomenon of vortex phase distribution in free space, which has attracted enormous attention in theoretical research and practical application of wireless communication systems due to its characteristic of infinitely orthogonal modes. However, traditional methods generating OAM beams are bound to complex structure, large device, multiple layers, complex feed networks, and limited beams in microwave range. Here, a digital coding transmissive metasurface (DCTMS) with a single layer substrate and the bi-symmetrical arrow is proposed and designed to generate multi-OAM-beam based on Pancharatnam−Berry (PB) phase principle. The 3-bit phase response can be realized by encoding the geometric phase into rotation angle of unit cell for DCTMS. Additionally, the phase compensation of the metasurface is introduced to achieve the beam focusing and the conversion from spherical wave to plane wave. According to the digital convolution theorem, the far-field patterns and near-field distributions of multi-OAM-beam withl= −2 modes are adequately demonstrated by DCTMS prototypes. The OAM efficiency and the purity are calculated to demonstrate the excellent multi-OAM-beam. The simulated and experimental results illustrate their performance of OAM beams. The designed DCTMS has profound application in multi-platform wireless communication systems and the multi-channel imaging systems. 相似文献
212.
本文采用Sn自熔剂法,制备Mg掺杂Sn基单晶笼合物Ba8Ga16-XMgXSn30(0 X 1.5),并对其结构及电传输性能进行研究.结果表明所制备化合物为具有空间群Iˉ43m的VIII型单晶笼合物,随Mg掺杂量的增加,对应化合物的熔点略有升高,晶格常数减小,掺杂样品中填充原子Ba的实际含量低于理想值8.0,其在十二面体空洞中的占有率约为0.93(Mg的名义含量X=1.5时).所有样品均表现为n型传导,Mg的掺入对材料的能带结构有一定影响,Mg掺杂后,样品的载流子浓度降低,Seebeck系数的绝对值、电阻率增加,Mg的名义含量X=1.5时,样品的功率因子在430 K附近取得最大值1.26×10-3W·m-1·K-2. 相似文献
213.
本文采用Sn自熔剂法,制备Mg掺杂Sn基单晶笼合物Ba8Ga16-XMgXSn30 (0 ≤ X ≤ 1.5),并对其结构及电传输性能进行研究. 结果表明所制备化合物为具有空间群I43 m的Ⅷ型单晶笼合物,随Mg掺杂量的增加,对应化合物的熔点略有升高,晶格常数减小,掺杂样品中填充原子Ba的实际含量低于理想值8.0,其在十二面体空洞中的占有率约为0.93(Mg的名义含量X=1.5时). 所有样品均表现为n型传导,Mg的掺入对材料的能带结构有一定影响,Mg掺杂后,样品的载流子浓度降低,Seebeck系数的绝对值、电阻率增加,Mg的名义含量X=1.5时,样品的功率因子在430 K附近取得最大值1.26×10-3 W·m-1·K-2.
关键词:
Ⅷ型笼合物
n型传导
单晶 相似文献
214.
Maksimoska J Feng L Harms K Yi C Kissil J Marmorstein R Meggers E 《Journal of the American Chemical Society》2008,130(47):15764-15765
A strategy for targeting protein kinases with large ATP-binding sites by using bulky and rigid octahedral ruthenium complexes as structural scaffolds is presented. A highly potent and selective GSK3 and Pim1 half-sandwich complex NP309 was successfully converted into a PAK1 inhibitor by making use of the large octahedral compounds Lambda-FL172 and Lambda-FL411 in which the cyclopentadienyl moiety of NP309 is replaced by a chloride and sterically demanding diimine ligands. A 1.65 A cocrystal structure of PAK1 with Lambda-FL172 reveals how the large coordination sphere of the ruthenium complex matches the size of the active site and serves as a yardstick to discriminate between otherwise closely related binding sites. 相似文献
215.
Transition-metal dichalcogenides (TMDs) have promising properties for their use as catalysts of CO2 reduction to methane via the Sabatier reaction. In this article we use density-functional theory calculations to gain insight into the energetics of this reaction for Mo/W-based and S/Se-based TMDs with non-, Ni- and Cu-doping. We show that sulfur-based TMDs with Ni/Cu doping exhibit better indicators for catalytic performance of the CO2 reduction reaction than non-doped and doped TMDs without active sites. In addition, the role of the transition metal was found to a much smaller influence in the reaction than the role of the chalcogen and dopant atoms, which influence the bonding strength and type, respectively. 相似文献
216.
Zangi R 《The Journal of chemical physics》2012,136(18):184501
Ions with like-charges repel each other with a magnitude given by the Coulomb law. The repulsion is also known to persist in aqueous solutions albeit factored by the medium's dielectric constant. In this paper, we report results from molecular dynamics simulations of alkali halides salt solutions indicating an effective attraction between some of the like-charged monovalent ions. The attraction is observed between anions, as well as between cations, leading to the formation of dimers with lifetimes on the order of few picoseconds. Two mechanisms have been identified to drive this counterintuitive attraction. The first is exhibited by high-charge density ions, such as fluoride, at low salt concentrations, yielding effective attractions with magnitude up to the order of 1-2 kT. In this case, the stronger local electric field generated when the two ions are in contact augments the alignment of neighboring waters toward the ions. This results in a gain of substantial favorable ion-water interaction energy. For fluorides, this interaction constitutes the major change among the different energy components compensating for the anion-anion repulsion, and therefore, rendering like-charge association possible. The second mechanism involves mediation by counterions, the attractions increase with salt concentration and are characterized by small magnitudes. In particular, clusters of ion triplets, in which a counterion is either bridging the two like-charged ions or is paired to only one of them, are formed. Although these two mechanisms may not yield net attractions in many cases, they might still be operational and significant, explaining effective repulsions between like-charged ions with magnitudes much smaller than expected based on continuum electrostatics. 相似文献
217.
Ronen Bar‐Ziv Dr. Israel Zilbermann Dr. Olga Oster‐Golberg Dr. Tomer Zidki Guy Yardeni Prof. Haim Cohen Prof. Dan Meyerstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4699-4705
Methyl radicals react in fast reactions, with rate constants k>1×108 M ?1 s?1, with Au0, Ag0 and TiO2 nanoparticles (NPs) dispersed in aqueous solutions to form intermediates, (NP)? (CH3)n, in which the methyl groups are covalently bound to the NPs. These intermediates decompose to form ethane. As n≥2 is required for the formation of C2H6, the minimal lifetime (τ) of the methyls bound to the NPs, (NP)? CH3, can be estimated from the rate of production of the CH3. radicals and the NPs concentration. The results obtained in this study, using a very low dose rate γ‐source for NP=Ag0, Au0, and TiO2 point out that τ of these intermediates is surprisingly long, for example, ≥8 and ≥188 sec for silver and gold, respectively. These data point out that the NP? C bond dissociation energies are ≥70 kJ mol?1. Under low rates of production of CH3., that is, when the rate of formation of ethane is very low, other reactions may occur, consequently the mechanism proposed is “broken”. This is observed in the present study only for TiO2 NPs. These results have to be considered whenever alkyl radicals are formed near surfaces. Furthermore, the results point out that the rate of reaction of methyl radicals with (NP)? (CH3)n depends on n, that is, the number of methyl radicals bound to the NPs affect the properties of the NPs. 相似文献
218.
219.
We show that the convex hull of any N points in the hyperbolic space ${\mathbb{H}^{n}}$ is of volume smaller than ${\frac{2 (2 \sqrt \pi)^n}{\Gamma(\frac n 2)} N}$ , and that for any dimension n there exists a constant C n > 0 such that for any set ${A \subset \mathbb{H}^{n}}$ , $$Vol(Conv(A_1)) \leq C_n Vol(A_1)$$ where A 1 is the set of points of hyperbolic distance to A smaller than 1. 相似文献
220.
We first point out that the subpixel response function is another kernel function in digital imaging. Then we show that the subpixel response function of CMOS imaging sensor pixels can be measured with an aperture array pixel mask in a single-shot image capture. Our technique permits high-resolution subpixel response function measurement of imaging pixels for superresolution imaging applications. 相似文献