全文获取类型
收费全文 | 42803篇 |
免费 | 4100篇 |
国内免费 | 2594篇 |
专业分类
电工技术 | 972篇 |
综合类 | 2027篇 |
化学工业 | 10058篇 |
金属工艺 | 3814篇 |
机械仪表 | 1545篇 |
建筑科学 | 3109篇 |
矿业工程 | 814篇 |
能源动力 | 2109篇 |
轻工业 | 1575篇 |
水利工程 | 284篇 |
石油天然气 | 328篇 |
武器工业 | 520篇 |
无线电 | 4167篇 |
一般工业技术 | 14911篇 |
冶金工业 | 1994篇 |
原子能技术 | 368篇 |
自动化技术 | 902篇 |
出版年
2024年 | 124篇 |
2023年 | 950篇 |
2022年 | 1014篇 |
2021年 | 1498篇 |
2020年 | 1741篇 |
2019年 | 1505篇 |
2018年 | 1398篇 |
2017年 | 1530篇 |
2016年 | 1442篇 |
2015年 | 1481篇 |
2014年 | 2214篇 |
2013年 | 2508篇 |
2012年 | 2640篇 |
2011年 | 3627篇 |
2010年 | 2627篇 |
2009年 | 2761篇 |
2008年 | 2543篇 |
2007年 | 2803篇 |
2006年 | 2443篇 |
2005年 | 2285篇 |
2004年 | 1875篇 |
2003年 | 1629篇 |
2002年 | 1334篇 |
2001年 | 991篇 |
2000年 | 874篇 |
1999年 | 650篇 |
1998年 | 621篇 |
1997年 | 432篇 |
1996年 | 349篇 |
1995年 | 284篇 |
1994年 | 284篇 |
1993年 | 204篇 |
1992年 | 165篇 |
1991年 | 156篇 |
1990年 | 131篇 |
1989年 | 110篇 |
1988年 | 51篇 |
1987年 | 35篇 |
1986年 | 31篇 |
1985年 | 22篇 |
1984年 | 37篇 |
1983年 | 23篇 |
1982年 | 29篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1963年 | 2篇 |
1955年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
A route to synthesize ZSM‐5 crystals with a bimodal micro/mesoscopic pore system has been developed in this study; the successful incorporation of the mesopores within the ZSM‐5 structure was performed using tetrapropylammonium hydroxide (TPAOH)‐impregnated mesoporous materials containing carbon nanotubes in the pores, which were encapsulated in the ZSM‐5 crystals during a solid rearrangement process within the framework. Such mesoporous ZSM‐5 zeolites can be readily obtained as powders, thin films, or monoliths. 相似文献
73.
In this paper, the moving least-squares differential quadrature (MLSDQ) method is employed for free vibration of thick antisymmetric laminates based on the first-order shear deformation theory. The generalized displacements of the laminates are independently approximated with the centered moving least-squares (MLS) technique within each domain of influence. The MLS nodal shape functions and their partial derivatives are computed quickly through back-substitutions after only one LU decomposition. Subsequently, the weighting coefficients in the MLSDQ discretization are determined with the nodal partial derivatives of the MLS shape functions. The MLSDQ method combines the merits of both the differential quadrature and meshless methods which can be conveniently applied to complex domains and irregular discretizations without loss of implementation efficiency and numerical accuracy. The natural frequencies of the laminates with various edge conditions, ply angles, and shapes are calculated and compared with the existing solutions to study the numerical accuracy and stability of the MLSDQ method. Effects of support size, order of completeness of basis functions, and node irregularity on the numerical accuracy are investigated in detail. 相似文献
74.
75.
The present paper includes experimental and analytical data on the fracture properties of a nickel-iron superalloy, a ferromagnetic austenite, at 4 K in magnetic fields of 0 and 6 T. The tensile, notch tensile and small punch tests are employed. A finite element analysis is also performed to convert the experimentally measured load-displacement data into useful engineering information. To interpret the results we review the available theory of the influence of magnetic field on the stress intensity factor for a crack in ferromagnetic materials. 相似文献
76.
77.
滑坡相似材料试验结果优化分析研究 总被引:2,自引:0,他引:2
在运用模糊综合评判确定的滑坡相似材料试验配合比隶属度基础上,利用方差分析确定各因素的数学优化区间,结合变量有上下界的改进单纯形法,获得技术,经济上的最佳配合比,克服了统计优化理论不能在连续区间寻优的缺点,这对从事滑坡相似材料试验研究具有一定的实际意义。 相似文献
78.
A.L. Pan H.G. ZhengZ.P. Yang F.X. Liu Z.J. Ding Y.T. Qian 《Materials Research Bulletin》2003,38(5):789-796
Small Ag particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: First the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, then they were soaked in AgNO3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements. 相似文献
79.
机械合金化Fe-Ni粉末的相结构 总被引:1,自引:0,他引:1
使用XRD和Moessbauer等方法,研究了在Ar气氛下机械合金化Fe—Ni粉末相结构的变化.结果表明,在机械合金化Fe64-Ni36粉末过程中,fcc相的数量随着球磨时间的增加先增加然后减少,与加乙醇球磨Fe64-Ni36的情形相同.当Ni的含量(原子分数)大于50%时,有fcc相、顺磁相和FeNi3形成,当Ni的含量低于50%时,bcc相的数量随着Ni含量减少而增加.Moessbauer谱的结果表明,因球磨时间或Fe、Ni比例的不同,Fe—Ni球磨粉末固溶体具有不同结构的原子配比。 相似文献
80.