全文获取类型
收费全文 | 458919篇 |
免费 | 6049篇 |
国内免费 | 2633篇 |
专业分类
化学 | 234519篇 |
晶体学 | 6522篇 |
力学 | 22138篇 |
综合类 | 117篇 |
数学 | 64170篇 |
物理学 | 140135篇 |
出版年
2020年 | 2997篇 |
2019年 | 3170篇 |
2018年 | 11709篇 |
2017年 | 12576篇 |
2016年 | 9632篇 |
2015年 | 5178篇 |
2014年 | 6179篇 |
2013年 | 16165篇 |
2012年 | 17339篇 |
2011年 | 27622篇 |
2010年 | 17541篇 |
2009年 | 17554篇 |
2008年 | 24635篇 |
2007年 | 27788篇 |
2006年 | 14758篇 |
2005年 | 19434篇 |
2004年 | 15170篇 |
2003年 | 13582篇 |
2002年 | 11595篇 |
2001年 | 11754篇 |
2000年 | 9163篇 |
1999年 | 6668篇 |
1998年 | 5353篇 |
1997年 | 5304篇 |
1996年 | 5459篇 |
1995年 | 4732篇 |
1994年 | 4691篇 |
1993年 | 4435篇 |
1992年 | 4891篇 |
1991年 | 4926篇 |
1990年 | 4518篇 |
1989年 | 4421篇 |
1988年 | 4374篇 |
1987年 | 4222篇 |
1986年 | 4183篇 |
1985年 | 5754篇 |
1984年 | 5806篇 |
1983年 | 4812篇 |
1982年 | 5196篇 |
1981年 | 4874篇 |
1980年 | 4612篇 |
1979年 | 4760篇 |
1978年 | 5057篇 |
1977年 | 4969篇 |
1976年 | 4965篇 |
1975年 | 4683篇 |
1974年 | 4724篇 |
1973年 | 4874篇 |
1972年 | 3407篇 |
1971年 | 2620篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A. Lashgari S. Ghammamy R. Ramirez-Tagle G. Salgado-Moran 《Journal of Structural Chemistry》2015,56(8):1505-1513
Two new compounds of fluorine: (C2H5)4N[I2F] and (C2H5)4N[Br2F], have been easily synthesized in a nearly quantitative by a direct reaction of (C2H5)4NF, I2 and Br2. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied computationally with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by timedependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values showes that the experimental results correlate well with the predicted data. 相似文献
52.
53.
54.
55.
56.
57.
58.
59.
60.
M. Kroon E. Andreasson E. Persson Jutemar V. Petersson L. Persson M. Dorn P.A.T. Olsson 《Experimental Mechanics》2018,58(1):75-86
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters. 相似文献