全文获取类型
收费全文 | 2318篇 |
免费 | 725篇 |
国内免费 | 127篇 |
专业分类
化学 | 349篇 |
晶体学 | 17篇 |
力学 | 402篇 |
综合类 | 129篇 |
数学 | 488篇 |
物理学 | 1785篇 |
出版年
2024年 | 3篇 |
2023年 | 24篇 |
2022年 | 70篇 |
2021年 | 66篇 |
2020年 | 63篇 |
2019年 | 66篇 |
2018年 | 78篇 |
2017年 | 97篇 |
2016年 | 121篇 |
2015年 | 92篇 |
2014年 | 170篇 |
2013年 | 174篇 |
2012年 | 165篇 |
2011年 | 182篇 |
2010年 | 168篇 |
2009年 | 150篇 |
2008年 | 145篇 |
2007年 | 161篇 |
2006年 | 138篇 |
2005年 | 155篇 |
2004年 | 119篇 |
2003年 | 127篇 |
2002年 | 103篇 |
2001年 | 92篇 |
2000年 | 78篇 |
1999年 | 51篇 |
1998年 | 57篇 |
1997年 | 41篇 |
1996年 | 29篇 |
1995年 | 22篇 |
1994年 | 22篇 |
1993年 | 20篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有3170条查询结果,搜索用时 15 毫秒
161.
162.
163.
164.
§ 1.Introduction Allgraphsconsideredinthispaperarefinite,undirected ,unloopedandsimplegraphs.WedenotethechromaticpolynomialofagraphGbyP(G ,λ)orP(G) .WesaygraphsGandHtobechromatiallyequivalentifP(G) =P(H) .ThechromaticuniquenessofagraphGisestablishedifitcanbeded… 相似文献
165.
Single CO2 laser pulses, of 10.6μm wavelength, are used to form blind microvias (holes in electronic boards for through-plating conducting paths) in copper-clad epoxy-glass laminates. The microvia dimensions depend on pulse energy and duration, the thicknesses of the epoxy-glass laminate and copper cladding, and the distribution of glass within the epoxy-glass laminate. The useful range of laser parameters, especially pulse energy, is primarily determined by the ability to metallize subsequently the blind microvias. Several conclusions can be drawn from the data. The pulse enegy should be within ±20% of the optimum value in order to form vias with a cylindrical geometry. For 300 μm thick laminates, the thickness of the copper on the bottom should be 18 μm or more. A larger range of pulse energies could be used if the glass fibre density was more uniform and if subsequent copper metallization of the blind vias could be improved. 相似文献
166.
You Ming-Chang 《International Journal of Infrared and Millimeter Waves》1986,7(6):919-925
The configurations of the coupling network, which can effectively aecrease the effect of the noise sources within the amplifier on the equivalent input noise of the whole pyroelectric detector-amplifier system, are studied. The influences of feedback upon the noise properties of the basic amplifiers are analyzed. The procedures of designing low-noise pyroelectric detector-amplifier systems are followed. 相似文献
167.
Zi Qiang Yang Tao Yang Yu You 《International Journal of Infrared and Millimeter Waves》2005,26(10):1437-1444
This paper reports on the design of a Ka-band monolithic Lange coupler and its application in the monolithic fourth-harmonic
image rejection mixer. Detailed design and analysis using Ansoft-HFSS simulator have been carried out. The simulated results
of the Lange Coupler show the insert loss is better than −3.64 dB; the amplitude balance is less than 0.55 dB and the phase
balance is less than 0.65° from the 90° phase difference over the 30 to 40 GHz frequency range. The Lange Coupler is employed
in a monolithic image rejection mixer that is fabricated by a commercial 0.18-μm pseudomorphic high electron-mobility transistor
(pHEMT) process. The chip size is 1.4 mm × 1.9 mm. The image rejection ratio (IMR) is from 15 to 34 dB in the RF frequency
range of 30 to 40 GHz. 相似文献
168.
Zhisheng Lin Zaichun Zhong Shiqing Yu 《International Journal of Infrared and Millimeter Waves》2001,22(4):545-552
Automatic Gain Controlled (AGC) Loops are used in MM-Wave receiver in wide-ranging. In this paper, the equivalent model and loop equation of AGC Loop are built, the loop errors are analyzed and then the design steps of AGC Loop are given out. 相似文献
169.
量子隧穿中的等效势垒 总被引:2,自引:0,他引:2
本文给出等效垫垒的概念及性质,利用等效势垒的性质可以使量子遂穿中的有关问题更容易解决。 相似文献
170.
A new approach to an equivalent circuit analysis of impedance spectra of a conducting polyaniline (PAni) layer is presented.
Film properties are often modeled by constant-phase elements (CPE), which are closer to experimental results than capacitors.
We want to take an insight into the CPE. We propose a novel equivalent circuit based on the Frumkin-Melik-Gaikazyan adsorption
model, as we suppose that the PAni layer molecules may behave like other adsorbing and relaxing organic compounds. Measurements
are performed using recently developed experimental technique—dynamic electrochemical impedance spectroscopy. Obtained spectra
are analyzed using the proposed equivalent circuits. Characteristics of several parameters are analyzed and discussed.
Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 9, pp. 1111–1119.
The text was submitted by the authors in English. 相似文献