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排序方式: 共有175条查询结果,搜索用时 15 毫秒
41.
K. Jaouadi N. Zouari T. Mhiri A. Daoud F. Romain 《Journal of Raman spectroscopy : JRS》2007,38(3):344-348
Raman spectra (10–1200 cm−1) of polycrystalline samples of Rb2(HSeO4)(H2PO4) were studied at temperatures ranging from 300 to 423 K. An assignment of most of the observed bands is proposed. The first‐order phase transition previously detected at 382 K was characterized as: This superionic‐protonic transition is believed to be governed by librations of the HSe/PO42− ion and the A OH (A = Se, P) stretching mode. It corresponds to the weakening of Se(P) O H˙˙˙ H O Se(P) hydrogen bonds and to the melting of the proton sublattice into a quasi‐liquid state in which the protons and the HSe/PO42− ions contribute to the unusually high conductivity. The activation energy that was determined from the plot Δν1/2 versus temperature for the ν (A OH) band has the same order of magnitude as that determined from conductivity measurements. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
42.
R. Ben Hassen A. Ben Salah A. Kallel A. Daoud J. Jaud 《Journal of chemical crystallography》2002,32(11):427-430
CH3NH3CdBr3 crystallizes in the space group Ccm21, a = 13.693(1) Å, b = 7.906(1) Å, c = 6.886(1) Å, V = 745.46(15) Å3, Z = 4, D
x
= 3.42 Mg m–3. The structure of the title compound is one-dimensional consisting of infinite chains made of face sharing CdBr6 octahedra. The methylammonium groups are situated in the space between chains. The cations and anions are joined by hydrogen bonding. 相似文献
43.
Ikram Dhouib Zakaria Elaoud Tahar Mhiri Abdelaziz Daoud 《Journal of chemical crystallography》2012,42(5):513-518
Abstract
The salt bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate [C6H5CH2NH3 +]2HAsO4 2−·H2O, M = 373.92, Triclinic, P−1. a = 6.514(1), b = 8.910(2), c = 15.061(3) ?, α = 99.26(2), β = 93.93(1), γ = 97.64(1)°, V = 851.5(3), Z = 2, D x = 1.460, λ (MoKα) = 0.71073 ?, μ = 0.99 mm−1, F(000) = 126, T = 20(2) °C, final R = 0.673 for 5488 unique reflections. Planes of HAsO4 2− alternate with planes of C6H5CH2NH3 + groups. The structure consists of infinite parallel two-dimensional planes built of mutually connected ions and water molecules by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than van der Waals interactions between the layers. Differential scanning calorimetry study on bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate was carried out. The infrared of polycrystalline samples of this compound have been recorded at room temperature. 相似文献44.
Daoud Siniora 《Mathematical Logic Quarterly》2023,69(2):221-230
We show that the countable universal ω-categorical bowtie-free graph admits generic automorphisms. Moreover, we show that this graph is not finitely homogenisable. 相似文献
45.
Triboelectric and Piezoelectric Effects in a Combined Tribo‐Piezoelectric Nanogenerator Based on an Interfacial ZnO Nanostructure 下载免费PDF全文
In this contribution, combined triboelectric and piezoelectric generators (TPEG) with a sandwich structure of aluminum‐polydimethylsiloxane/polyvinylidene fluoride composite‐carbon (Al‐PPCF‐Carbon) are fabricated for the purpose of mechanical energy harvesting. Improved by the surface modification of PPCF with zinc oxide (ZnO) nanorods through a hydrothermal method, the TPEG generates an open‐circuit voltage (Voc) of ≈40 V, a short‐circuit current (Isc) of 0.28 μA with maximum power density of ≈70 mWm?2, and maximum conversion efficiency of 34.56%. Subsequently, in order to understand the transduction mechanism of the triboelectric and piezoelectric effects, analyses focusing on the potential composition ratio in the final output and the impact of ZnO interfacial nanostructure are carried out. The observed potential ratio between triboelectric and piezoelectric effects is 12.75:1 and the highest potential improvement by ZnO nanorods of 21.8 V is achieved by the TPEG fabricated with spacer. Finally, the relationships between the voltage, power density, conversion efficiency, and the external load resistances are also discussed. Overall, the fabricated TPEG is proved to be a simple and effective nanogenerator in mechanical energy conversion with enhanced output potential and conversion efficiency. 相似文献
46.
S. A. El-Reefy J. A. Daoud H. F. Aly 《Journal of Radioanalytical and Nuclear Chemistry》1992,158(2):303-312
It is found that from aqueous nitric acid media, Pd is highly extracted by chloroform solutions containing triphenylphosphine (Ph3P) and not extracted by triphenylphosphine oxide (Ph3PO) diluted with chloroform. The effect of diluent, nitric acid molarities, Ph3P concentration and temperature on palladium extraction by Ph3P was investigated. Slope analysis of the experimental results indicated that the main extracted species is in the form of Pd(NO3)2·2Ph3P.IR spectrum analysis of the extracted complex indicated the direct extraction of palladium as nitrate and bonding to phosphorus. Extraction of some fission product radionuclides from 2M HNO3 showed the selective extraction of palladium by Ph3P in chloroform. 相似文献
47.
Vapor pressure is one of the fundamental properties which govern the distribution of organic compounds in the environment. This property is estimated for five series of homologous substituted alkanes of the type H—(CH2)n—Y, where Y denotes Cl, Br, CHO, COOCH3, OCOCH3 and n varies from 5 to 14 using extrapolation of adjusted retention times to 25 °C. The results are compared with those obtained by using indirect methods for 40 compounds and a significant improvement is obtained. Indeed, the absolute average error percentage for the same series does not exceed 2.6% 相似文献
48.
Alexandre Campos Moraes Daniel Benevides da Costa Michel Daoud Yacoub 《Wireless Personal Communications》2012,64(1):3-19
Wireless communications systems in a frequency reuse environment are subject to cochannel interference. In order to improve
the system performance, diversity techniques are deployed. Among the practical diversity schemes used, Equal-Gain Combining
(EGC) appears as a reasonably simple and effective one. Unfortunately, the exact analysis of the outage probability of EGC
receivers is rather intricate for it involves the evaluation of multifold nested integrals. It becomes mathematically intractable
with the increase of the number of diversity branches and/or interferers. For example, for N
B
diversity branches and N
I
arbitrary independent cochannel interferers, the exact formulation using the convolutional approach requires 2 + N
B
+ (N
B
× N
I
) nested integrals, which, very quickly, and for any practical system, turns out to be mathematically intractable. In this
paper, we propose accurate approximate formulations for this problem, whose results are practically indistinguishable from
the exact solution. In our model, the system is composed by N
B
branches and N
I
interferers so that the desired signals are coherently summed, whereas the interfering signals are incoherently summed at
the EGC receiver. Three sets of fading scenarios, namely α-μ , κ-μ, and η-μ, are investigated. The proposed approach is indeed flexible and accommodates a variety of mixed fading scenarios for desired
and interfering signals. 相似文献
49.
This paper describes the physical models behind the various fading distributions applicable in wireless-communications systems, and presents the probability density functions, both for the signal envelope and for the power of the mobile radio signal. It addresses the problem of co-channel interference in terms of its mean value, for macrocellular and microcellular structures, and illustrates how the outage probability is influenced by a series of factors such as reuse pattern, modulation scheme, traffic load, and others 相似文献
50.