全文获取类型
收费全文 | 700篇 |
免费 | 40篇 |
国内免费 | 3篇 |
专业分类
化学 | 452篇 |
晶体学 | 1篇 |
力学 | 40篇 |
数学 | 90篇 |
物理学 | 160篇 |
出版年
2024年 | 4篇 |
2023年 | 6篇 |
2022年 | 53篇 |
2021年 | 37篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 21篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 23篇 |
2014年 | 38篇 |
2013年 | 41篇 |
2012年 | 39篇 |
2011年 | 38篇 |
2010年 | 47篇 |
2009年 | 36篇 |
2008年 | 39篇 |
2007年 | 31篇 |
2006年 | 34篇 |
2005年 | 28篇 |
2004年 | 29篇 |
2003年 | 22篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1989年 | 2篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1967年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
1927年 | 1篇 |
排序方式: 共有743条查询结果,搜索用时 15 毫秒
71.
Metallocene catalyst based polyethylene‐co‐7‐octenyldimethyl phenyl silane (PE/Si? Ph ) and its post‐treated functional forms PE/Si? X ( X = Cl , F , OCH3 , OCH2CH3 ) were used as additives in PE/ATH composites. The impact strength of the composites was significantly increased after a small addition (0.5–3.0 wt %) of the functionalized form of the copolymer (PE/Si? X ). The thermal study of the composites gave us more information about the additive's behavior at the filler/matrix interphase and correlation to the mechanical properties was found. According to this thermal data, the original untreated form of PE/Si? Ph also seemed to interact weakly with the ATH‐filler particles, which was seen in an altered interphase at the filler/matrix boundary layer. The interaction was not strong enough to improve the impact strength of composites but an increase was observed in some other mechanical properties (tensile stress, yield strain). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5597–5608, 2005 相似文献
72.
A method which employs an integrating sphere and a single-wavelength (1.6 μm) pyrometer for measuring the spectral effective emissivities of superalloys in the temperature range (=650–1050°C) is described. The spectral effective emissivities for five superalloys, namely, MARM-247, MARM-509, CMSX-4, Inconel-718, N-155 and two René-N6 samples coated with YSZ thermal barrier coating were measured. Correcting the pyrometer measurements for the variations in the object emissivity would reduce the uncertainty in the temperature measurements to <±1%. 相似文献
73.
The formyl carbonyl group in bis(4-methoxyphenyl)-acetaldehyde does not contribute to the formation of the carbonyl group in 4,4′-dimethoxydeoxybenzoin when the former rearranges to the latter by treatment with 50% (w/w) sulfuric acid. 相似文献
74.
Sami A. Shakir 《Physics letters. A》1983,93(9):510-512
We describe two methods for employing materials with giant Kerr nonlinearities for modulating waveguides. A beam, of relatively intense light, is used to vary the propagation constant of a waveguide with the guiding layer, or the substrate, made from a nonlinear material. 相似文献
75.
Sami F. Masri 《Experimental Mechanics》1967,7(2):49-55
An experimental study is made of the general behavior of single-particle impact dampers, using an electronic-analog computer
and a mechanical model. It is found that, under practically realizable conditions, impact damping is effective in reducing
the vibration-amplitude levels resulting from sinusoidal or random excitation.
Paper was presented at 1966 SESA Spring Meeting held in Detroit, Mich., on May 4–6. 相似文献
76.
Quantum confinement effect on the energy levels of Eu2+ doped K2Ca2(SO4)3 nanoparticles has been observed. The broad photoluminescence (PL) emission band of Eu2+ doped K2Ca2(SO4)3 microcrystalline sample observed at ~436 nm is found to split into two narrow well resolved bands, located at 422 and 445 nm in the nanostructure form of this material. This has been attributed to the reduction in the crystal field strength of the nanomaterials, which results in widening the energy band gap and splitting the broad 4f65d energy level of Eu2+. Energy band gap values of the micro and nanocrystalline K2Ca2(SO4)3 samples were also determined by measuring the UV–visible absorption spectra. These values are 3.34 and 3.44 eV for the micro and nanocrystalline samples, respectively. These remarkable results suggest that activators having wide emission bands might be subjected to weak crystal strength via nanostructure materials to modify their electronic transitions. This might prove a powerful technique for producing new-advanced materials for use in the fields of solid state lasers and optoelectronic devises. 相似文献
77.
This work presents a fast method for the simultaneous separation and determination of glimepiride, glibenclamide, and two related substances by RP LC. The separation was performed on a Chromolith Performance (RP-18e, 100 mm x 4.6 mm) column. As mobile phase, a mixture of phosphate buffer pH 3, 7.4 mM, and ACN (55:45 v/v) was used. Column oven temperature was set to 30 degrees C. The total chromatographic run time was 80 s. This was achieved using a flow program from 5 to 9.9 mL/min. Precisions of the interday and the intraday assay for both retention times and peak areas for the four analyzed compounds were less than 1.2%. The method showed good linearity and recovery. The short analysis time makes the method very valuable for quality control and stability testing of drugs and their pharmaceutical preparations. 相似文献
78.
Sami I. Muslih Om P. Agrawal Dumitru Baleanu 《International Journal of Theoretical Physics》2010,49(8):1746-1752
This paper presents a fractional Schrödinger equation and its solution. The fractional Schrödinger equation may be obtained using a fractional variational principle and a fractional Klein-Gordon equation; both methods are considered here. We extend the variational formulations for fractional discrete systems to fractional field systems defined in terms of Caputo derivatives to obtain the fractional Euler-Lagrange equations of motion. We present the Lagrangian for the fractional Schrödinger equation of order α. We also use a fractional Klein-Gordon equation to obtain the fractional Schrödinger equation which is the same as that obtained using the fractional variational principle. As an example, we consider the eigensolutions of a particle in an infinite potential well. The solutions are obtained in terms of the sines of the Mittag-Leffler function. 相似文献
79.
The Fourier transform method is used to solve fractional Poisson’s equation with Riesz fractional derivative of order α. It is shown that the solution is given in terms of the fractional dimensional space D. Gauss law for the electrostatic problem is given and the total electric flux is obtained in terms of α and D. 相似文献
80.