全文获取类型
收费全文 | 2306篇 |
免费 | 150篇 |
国内免费 | 226篇 |
专业分类
化学 | 722篇 |
晶体学 | 32篇 |
力学 | 439篇 |
综合类 | 31篇 |
数学 | 627篇 |
物理学 | 831篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 14篇 |
2021年 | 24篇 |
2020年 | 43篇 |
2019年 | 42篇 |
2018年 | 45篇 |
2017年 | 68篇 |
2016年 | 73篇 |
2015年 | 53篇 |
2014年 | 97篇 |
2013年 | 212篇 |
2012年 | 119篇 |
2011年 | 153篇 |
2010年 | 80篇 |
2009年 | 146篇 |
2008年 | 144篇 |
2007年 | 155篇 |
2006年 | 131篇 |
2005年 | 106篇 |
2004年 | 107篇 |
2003年 | 91篇 |
2002年 | 65篇 |
2001年 | 83篇 |
2000年 | 69篇 |
1999年 | 76篇 |
1998年 | 63篇 |
1997年 | 50篇 |
1996年 | 45篇 |
1995年 | 44篇 |
1994年 | 46篇 |
1993年 | 29篇 |
1992年 | 27篇 |
1991年 | 20篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 3篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有2682条查询结果,搜索用时 218 毫秒
161.
The mark-tracking method was used in the uniaxial tensile test to determine the elastic properties of optical fibers. The mark-tracking method is based on the follow-up of two markers on the specimen with the help of an image processing technique. It allows us to determine the true strain with respect to the small strains assumption (≤1%) or the finite strains (>1%) without any impact of the rigid solid movement or pulley fiber sliding on the measured strain. Both coated optical fiber and stripped fiber were subjected to the uniaxial tensile test and the cantilever beam bending test. The Young’ modulus results of the stripped fiber were found to be very similar for both tests. Thus, the mark-tracking method is adaptable to the tensile test of optical fibers and the elastic behaviors of both coated optical fiber and stripped fiber are found to be non-linear. Their Young's moduli are 22 and 79 GPa, respectively. These results revealed that those coatings play a mechanical role in fiber elongation. 相似文献
162.
S. Abdalla 《Physica B: Condensed Matter》2011,406(3):584-587
The complicated structure of human blood has been characterized based on relaxation time, τ, and the Cole-Cole parameter, α, obtained from dielectric measurements. As previously reported by different authors, the experimental data show net deviation from the classical Debye model with certain distribution of relaxation times (Dτ). Plots of α versus width of the relaxation rate distribution of micro-particles inside the blood show that Dτ drastically affects the dielectric properties of the fluid. The mathematical function of Dτ is found to be Gaussian and we find that the α values of normal blood have net lower magnitude than that of diabetic blood. These results suggest that glucose in blood increases the broadness of the parameter α, which have significant importance in diabetic-biosensor manufacture. 相似文献
163.
采用低压等离子体聚合技术,通过调整工作气压和反式二丁烯(T2B)与H2流量比制备了辉光放电聚合物(GDP)涂层. 利用傅里叶变换红外吸收光谱和元素分析法讨论了工作气压和T2B与H2流量比对GDP涂层内部H原子含量及结构的影响,并且通过纳米压痕技术对GDP涂层的硬度及杨氏模量进行了表征.研究结果表明:降低工作气压和T2B与H2流量比,GDP涂层内sp3 C
关键词:
傅里叶变换红外光谱
纳米压痕
杨氏模量
硬度 相似文献
164.
The dc and ac electrical transport property of Polyvinyl Alcohol-Multiwall Carbon Nanotubes (PVA-MWNT) composites has been investigated within a temperature range and in the frequency range 20Hz-1MHz. The temperature variation of dc conductivity gives the presence of two different activation energies. The dielectric properties of the samples have been explained in terms of electric modulus vector.The dielectric relaxation has been explained in terms of interfacial polarization occurring in between the insulating PVA matrix and MWNT conductive filler. The variation of the relaxation time with temperature also indicates the presence of two different activation energies. 相似文献
165.
Young′s moduli of various epoxy coated polyethylene terephthalate (PET) micro-cantilevers were determined from the deflection results obtained using the phase-shift shadow moiré (PSSM) method. The filler materials for epoxy coatings were aluminum and graphite powders that were mixed with epoxy at various percentages. Young′s moduli were calculated from theory based on the deflection results. The PET micro-cantilever coated with aluminum-epoxy coating showed increasing value of Young′s modulus when the ratios of the aluminum-epoxy were increased. The graphite-epoxy coating on the PET micro-cantilever also showed the same trend. The experimental results also show that Young′s modulus of the graphite-epoxy coating is higher than aluminum-epoxy coating in comparison at the same mixing ratio. 相似文献
166.
167.
γ-Fe2O3 has a spinel structure with cation vacancy and is expected to perform as a favorable electrode material for secondary lithium-ion battery. When lithium is inserted electrochemically into γ-Fe2O3, prolonged potential change is observed after the insertion. In this study, we inserted various amount of Li into γ-Fe2O3 (x = 0.66, 1.1, 1.5 in terms of LiXFe2O3), then made the circuit open, measured X-ray diffraction (XRD) patterns at various elapsed time, and analyzed the crystal structure change of γ-Fe2O3 with time by the Rietveld method. The X-ray Rietveld analysis revealed that the iron occupancy of 8a site decreased and that of 16c site increased with lithium insertion process and after lithium insertion, the iron occupancy of 8a site increased and that of 16c site decreased gradually with relaxation time. It is indicated that lithium prefer 8a site to occupy kinetically, on the other hand, prefer 16c site thermodynamically. 相似文献
168.
In this study, clad layers of iron-based alloy with a nature of self-fluxing were melted on low carbon steel by plasma cladding process. Nanoindentation with atomic force microscopy (AFM) has been used to investigate the mechanical properties of the coating. Hardness and elastic modulus at ultra-low loads were first determined using the method proposed by Giannakopoulos and Suresh (G&S method). The true contact area and mechanical properties were then determined using atomic force microscopy (AFM) combined with the Oliver and Pharr method (new proposed method) as the correction group. The mechanical properties calculated by the two methods showed the same distribution while had deviation in specific values. The effect of surface roughness to the calculated mechanical properties was investigated. Both hardness and elastic modulus were found to exhibit certain surface roughness dependence. When root mean square (RMS) roughness ranged from 2.2 nm to 4.4 nm, hardness calculated by both the methods increased obviously and reached maximums around 4.1 nm. Elastic modulus calculated by G&S method at different RMS showed the same distribution with that of hardness, while reduced elastic modulus obtained by AFM was insensitive to the range of RMS. 相似文献
169.
A combination of molecular dynamics (MD), continuum elasticity and FEM is used to predict the effect of CNT orientation on the shear modulus of SWCNT-polymer nanocomposites. We first develop a transverse-isotropic elastic model of SWCNTs based on the continuum elasticity and MD to compute the transverse-isotropic elastic constants of SWCNTs. These constants are then used in an FEM-based simulation to investigate the effect of SWCNT alignment on the shear modulus of nanocomposites. Furthermore, shear stress distributions along the nanotube axis and over its cross-sectional area are investigated to study the effect of CNT orientation on the shear load transfer. 相似文献
170.
George TEPHNADZE 《数学物理学报(B辑英文版)》2014,(5):1593-1602
The main aim of this paper is to find necessary and sufficient conditions for the convergence of Walsh-Kaczmarz-Fej′er means in the terms of the modulus of continuity on the Hardy spaces Hp, when 0〈p≤1/2. 相似文献