全文获取类型
收费全文 | 4919篇 |
免费 | 395篇 |
国内免费 | 487篇 |
专业分类
化学 | 1113篇 |
晶体学 | 27篇 |
力学 | 1069篇 |
综合类 | 10篇 |
数学 | 485篇 |
物理学 | 1160篇 |
综合类 | 1937篇 |
出版年
2024年 | 24篇 |
2023年 | 113篇 |
2022年 | 107篇 |
2021年 | 101篇 |
2020年 | 127篇 |
2019年 | 101篇 |
2018年 | 109篇 |
2017年 | 157篇 |
2016年 | 157篇 |
2015年 | 210篇 |
2014年 | 244篇 |
2013年 | 302篇 |
2012年 | 251篇 |
2011年 | 293篇 |
2010年 | 210篇 |
2009年 | 252篇 |
2008年 | 258篇 |
2007年 | 290篇 |
2006年 | 307篇 |
2005年 | 233篇 |
2004年 | 237篇 |
2003年 | 207篇 |
2002年 | 201篇 |
2001年 | 155篇 |
2000年 | 158篇 |
1999年 | 142篇 |
1998年 | 131篇 |
1997年 | 96篇 |
1996年 | 89篇 |
1995年 | 81篇 |
1994年 | 76篇 |
1993年 | 76篇 |
1992年 | 56篇 |
1991年 | 56篇 |
1990年 | 35篇 |
1989年 | 32篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1971年 | 3篇 |
1957年 | 3篇 |
1955年 | 1篇 |
排序方式: 共有5801条查询结果,搜索用时 31 毫秒
991.
Wing Kin Chan Jianrong Li Yong Wang Shengyao Zhang Tongyi Zhaug 《Acta Mechanica Solida Sinica》2010,23(4):283-296
This paper analyzes nanobridge tests with consideration of adhesive contact deformation, which occurs between a probe tip and a tested nanobeam, and deformation of a substrate or template that supports the tested nanobeam.Analytical displacement-load relation, including adhesive contact deformation and substrate deformation, is presented here for small deformation of bending.The analytic results are confirmed by finite element analysis.If adhesive contact deformation and substrate deformation are not considered in the analysis of nanobridge test data, they might lead to lower values of Young's modulus of tested nanobeams. 相似文献
992.
In this paper AlGaInP light emitting diodes with different types of electrodes:Au/Zn/Au-ITO Au/Ti-ITO Au/Ge/Ni-ITO and Au-ITO are fabricated. The photoelectricity properties of those LEDs are studied. The results show that the Au/Zn/Au electrode greatly improves the performance of LEDs compared with the other electrodes. Because the Au/Zn/Au electrode not only forms a good Ohmic contact with indium tin oxide (ITO), but also reduces the specific contact resistances between ITO and GaP, which are 1.273×10-6 ·cm2 and 1.743×10-3 ·cm2 between Au/Zn/Au-ITO and ITO-GaP respectively. Furthermore, the textured Zn/Au-ITO/Zn electrode is designed to improve the performances of LEDs, reduce the forward-voltage of the LED from 1.93 to 1.88 V, and increase the luminous intensity of the LEDs from 126 to 134 mcd when driven at 20 mA. 相似文献
993.
结合轴线偏移情况开展回转窑滚圈多轴疲劳寿命研究,采用了Wang和Brown提出的多轴疲劳准则和雨流计数法及Miner准则进行累积损伤评估.回转窑运行轴线偏移会导致滚圈承受的支承载荷分布严重不均,因此引入载荷比来描述轴线偏移程度以进一步定量分析滚圈应力.采用有限元软件ANSYS进行了各载荷比下滚圈的接触应力分析,并根据滚动接触区域情况计算得到了切向摩擦应力.以某回转窑滚圈为分析对象,计算得到了随载荷比变化的疲劳寿命曲线,揭示了轴线偏移对滚圈疲劳寿命的影响规律.研究对减少滚圈疲劳失效有重要意义,同时也可作为轴线调整和优化调窑的理论依据. 相似文献
994.
M. Hiane J. Ebothé 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(4):485-495
We show that the electrodeposition of Ni-Zn alloys at the lowest growth velocities, v < 0.5μm/s, exclusively proceeds from an abnormal co-deposition phenomenon. The growth process in this v region greatly depends on the initial [Co2+] concentration of the film deposition bath. A theoretical approach of this process including the role of the saturation surface
roughness of the alloy, , leads to an estimation of the transport properties of the ad-atoms involved during the deposit formation. Their surface
diffusion coefficient varying between 1.76×10-10 and 2.40×10-8 cm-2/s exhibits a minimal value, D
s = 2.10×10-10 cm-2/s located between v = 0.17 and 0.35μm/s. The spatial scaling analysis of the local roughness, σ, examined according to the power-law σ≈L
α reveals that the resulting roughness exponents concurs with the Kardar-Parisi-Zhang dynamics including the restricted surface
diffusion. Two main v regions leads to different fractal textural features of the alloy film surface. Below 0.10 μm/s, the roughness exponent obtained
is α≈ 0.6, depicting a limited ad-atom mobility. Over v = 0.30μm/s, this exponent stabilises at α≈ 0.82, indicating an increase of the surface diffusion.
Received 16 August 2000 and Received in final form 20 June 2001 相似文献
995.
996.
Reinhard Lipowsky 《Interface Science》2001,9(1-2):105-115
Recent theoretical and experimental studies have shown that structured surfaces, which contain patterns of lyophilic surface domains, lead to morphological wetting transitions at which the wetting layer changes its shape in a characteristic and typically abrupt manner. These transitions have been determined for several specific surface domain patterns consisting of circular, striped, or ring-shaped domains, as well as for slit pores and slabs bounded by striped surfaces. Such transitions are predicted to be rather generic and to occur for any type of structured surface. 相似文献
997.
Summary An interface crack problem is investigated under various assumptions on an interface between two elastic materials. The interface
is modeled by an additional third structure (thin elastic wedge of differing elastic properties) matching the bonded materials,
or by introducing special boundary conditions on the crack line ahead. The main emphasis of the paper is placed on a comparison
of the asymptotic expansion of the elastic solutions near the crack tip obtained for the different models. In particular,
the behaviour of the stress singularity exponent and the generalized SIF are discussed. Numerical examples are presented.
Received 16 August 2000; accepted for publication 26 May 2001 相似文献
998.
999.
线接触弹性接触变形的解析算法 总被引:14,自引:1,他引:13
以一般光滑性体接触理论为基础,结合有限长弹性体接触的特点,求出线接触弹性接蟹变形的解析公式,并发现其解析解与数值解具有很好的一致性,所得公式可以对赫兹线接触理论加以补充,与经验公式相比,它能够确切反映材料、载荷以及曲率半径等对接触变形的影响,为工程中的精确计算提供了方便。 相似文献
1000.
Nano-tribology through molecular dynamics simulations 总被引:1,自引:0,他引:1
The solidification and interfacial slip in nanometer-scale lubricating films as well as the contact and adhesion of metal
crystals have been studied via molecular dynamics simulations. Results show that the critical pressure for the solid-liquid
transition declines as the film thickness decreases, indicating that the lubricant in the thin films may exist in a solid-like
state. It is also found that the interfacial slip may occur in thin films at relatively low shear rate, and there is a good
correlation between the slip phenomenon and the lubricant solidification. The simulations reveal that a micro-scale adhesion
may take place due to the atomic jump during the process of approaching or separating of two smooth crystal surfaces, which
provides important information for understanding the origin of interfacial friction. 相似文献