全文获取类型
收费全文 | 656篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
综合类 | 2篇 |
化学工业 | 143篇 |
金属工艺 | 24篇 |
机械仪表 | 9篇 |
建筑科学 | 8篇 |
矿业工程 | 5篇 |
能源动力 | 70篇 |
轻工业 | 29篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 68篇 |
一般工业技术 | 232篇 |
冶金工业 | 9篇 |
原子能技术 | 4篇 |
自动化技术 | 55篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 9篇 |
2021年 | 19篇 |
2020年 | 30篇 |
2019年 | 30篇 |
2018年 | 24篇 |
2017年 | 34篇 |
2016年 | 30篇 |
2015年 | 25篇 |
2014年 | 40篇 |
2013年 | 31篇 |
2012年 | 20篇 |
2011年 | 43篇 |
2010年 | 29篇 |
2009年 | 24篇 |
2008年 | 27篇 |
2007年 | 26篇 |
2006年 | 21篇 |
2005年 | 20篇 |
2004年 | 6篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 15篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有670条查询结果,搜索用时 15 毫秒
1.
Sodium‐ion conducting polymer electrolytes based on poly(vinyl alcohol) complexed with sodium bromide were prepared with a solution‐casting technique. The structure of these films was determined with X‐ray diffraction, and the complexation of the salt with the polymer was confirmed with Fourier transform infrared spectroscopy studies. Electrical conductivity was measured with an alternating‐current impedance analyzer in the frequency range of 100 Hz to 1 MHz and in the temperature range of 303–373 K. It was observed that the magnitude of conductivity increased with the increase in the salt concentration as well as the temperature. The nature of the charge transport in these polymer electrolyte films was determined with both Wagner's polarization technique and the Watanabe technique. The dominant conducting species were found to be ions, particularly anions. Optical absorption studies were performed in the wavelength range of 200–600 nm, and the absorption edge, direct band gap, and indirect band gap values were evaluated. Electrochemical cells were fabricated, and their discharge characteristics were studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
2.
3.
《Inorganic chemistry communications》2007,10(4):467-470
The complex [Cd2(phen)4(p-phth)(H2O)2](p-phth) · 10H2O (1) has been synthesized by the reaction Cd(NO3)2 with phen and p-phth (where phen = 1,10-phenanthroline, p-phth = p-phthalic acid) in a solution of ethanol and distilled water. The crystal structure was characterized by X-ray single-crystal diffraction and infrared spectrum. In 1, a novel 2D supramolecular structure was formed, containing water octamer and tetramer. 相似文献
4.
R. Venugopal R. P. Vijayalakshmi D. R. Reddy B. K. Reddy 《Journal of Materials Science》1996,31(15):4081-4085
Thin films of ZnSe
x
CdS1–x (t 0.6 m) over the entire range of x, were deposited on glass substrates at two temperatures, T
s (350 and 470 K) by vacuum evaporation. X-ray diffraction studies showed that all the films were polycrystalline in nature. Films prepared at 470 K were nearly stoichiometric. Grain size increased with substrate temperature, T
s. The electrical conductivity and Hall measurements were carried out by d.c. van der Pauw technique. Hall effect studies/hot probe test showed that all the films were of n-type conductivity. Hall mobility increased with T
s. In addition, mobilities increased with temperature in films of all compositions, indicating the dominance of grain-boundary scattering. Grain-boundary potentials were in range 0.03–0.06 eV. 相似文献
5.
Abolfazl AleAhmad Hadi Amiri Ehsan Darrudi Masoud Rahgozar Farhad Oroumchian 《Knowledge》2009,22(5):382-387
The Persian language is one of the dominant languages in the Middle East, so there are significant amount of Persian documents available on the Web. Due to the different nature of the Persian language compared to the other languages such as English, the design of information retrieval systems in Persian requires special considerations. However, there are relatively few studies on retrieval of Persian documents in the literature and one of the main reasons is the lack of a standard test collection. In this paper, we introduce a standard Persian text collection, named Hamshahri, which is built from a large number of newspaper articles according to TREC specifications. Furthermore, statistical information about documents, queries and their relevance judgments are presented in this paper. We believe that this collection is the largest Persian text collection, so far. 相似文献
6.
7.
Summary The flow of a viscous conducting fluid between two parallel plates of infinite length (one of which is at rest and the other moving parallel to itself with a linear axial temperature variation) under the influence of a uniform transverse magnetic field is considered. It is assumed that the fluid is injected into the channel through the lower wall and sucked from the channel through the upper wall with the same velocityv
0. The velocity and temperature distributions, the coefficient of skin friction and the rate of heat transfer coefficient are evaluated. The effects of magnetic parameterM, the suction Reynolds numberR, the Grashoff numberG and Binkmann numberB
on the above mentioned physical quantities are investigated.With 21 Figures 相似文献
8.
This paper reports on the affect of lead content on the absorption and emission spectra of the Ho3+ ion doped lead-zinc-borate glasses in the composition (mol%) of (20 − x)PbO-20ZnO-(59 + x)B2O3-1.0Ho2O3 where x = 0, 5,10,15 of PbO content with λexc = 405 nm. The experimental absorption band energies have satisfactorily been correlated with the theoretical results with an r.m.s deviation of zero with the following correction factors obtained by a least square fit analysis: ΔE1 = 348.495936 cm− 1, ΔE2 = 1.436043 cm− 1, ΔE3 = 46.481575 cm− 1, Δξ4f = − 28.512979 cm− 1, Δα = 55.508936 cm− 1, Δβ = − 1394.339908 cm− 1 and Δγ = 1208.424336 cm− 1. By applying the Judd-Ofelt intensity parameter Ω2 has been found to be linearly decreasing with the PbO content from 5 to 10 mol% and then increasing. And also radiative (A, AT, β, τr) characteristic factors of the luminescent transitions (5I8 ← 5F3,4,5 and 5S2) of the glasses have been evaluated. Stimulated emission cross-sections (σpE) of the measured emission transitions of holmium glasses have also been computed. 相似文献
9.
《Materials Letters》2006,60(13-14):1702-1705
Nanocrystalline MMoO4 (M = Ni, Zn) phosphors, which have wolframite-type structure, were successfully synthesized at low temperatures via a modified citrate complex route assisted by microwave irradiation. The citrate complex precursors were heat-treated from 300 to 600 °C for 3 h. Crystallization of the MMoO4 (M = Ni, Zn) nanocrystallites were detected at 500 °C, and entirely completed at a temperature of 600 °C. The nanoparticles presented primarily dispersed and homogeneous morphology with particle size of 20–40 nm. The nanocrystalline MMoO4 (M = Ni, Zn) phosphors prepared at 600 °C exhibited broad luminescence in green and blue wavelength region, respectively. 相似文献
10.
《Solid-state electronics》1986,29(9):903-905
In the calculation of the true value of specific resistivity of reacted ohmic contacts, a modification in the conductivity of the semiconductor that may occur below the contact must be considered. Contacts to GaAs are discussed. A substantial decrease in the sheet resistance of p-type GaAs is measured for Pt-reacted contacts in which a single thin layer of Mg is interposed. It is pointed out that this lowering, which is attributed to the doping action of Mg, if not taken into account, can lead to serious errors in the estimation of specific contact resistivity. 相似文献