全文获取类型
收费全文 | 3929篇 |
免费 | 1036篇 |
国内免费 | 467篇 |
专业分类
化学 | 1298篇 |
晶体学 | 142篇 |
力学 | 250篇 |
综合类 | 32篇 |
数学 | 490篇 |
物理学 | 3220篇 |
出版年
2024年 | 16篇 |
2023年 | 61篇 |
2022年 | 112篇 |
2021年 | 117篇 |
2020年 | 138篇 |
2019年 | 132篇 |
2018年 | 152篇 |
2017年 | 197篇 |
2016年 | 210篇 |
2015年 | 162篇 |
2014年 | 263篇 |
2013年 | 378篇 |
2012年 | 276篇 |
2011年 | 337篇 |
2010年 | 255篇 |
2009年 | 310篇 |
2008年 | 279篇 |
2007年 | 258篇 |
2006年 | 223篇 |
2005年 | 181篇 |
2004年 | 191篇 |
2003年 | 171篇 |
2002年 | 145篇 |
2001年 | 133篇 |
2000年 | 118篇 |
1999年 | 99篇 |
1998年 | 85篇 |
1997年 | 74篇 |
1996年 | 67篇 |
1995年 | 43篇 |
1994年 | 42篇 |
1993年 | 26篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有5432条查询结果,搜索用时 15 毫秒
51.
The electromagnetic ultrasound is used in the detection of interfaces of the adhesive multilayer structures to solve the unstable coupling problem in ultrasonic testing by traditional piezoelectric transducers. Based on the analysis of the transforming mechanism of electromag-netic ultrasound energy and the resultant dead zone from mutual inductance of the transducer, the wavelet filtering by soft-thresholding and adaptive noise canceling methods are used simul-taneously to the detected electromagnetic ultrasonic signals to overcome the drawbacks of the low signal to noise ratio (SNR) and the wide intrinsic dead zone of the transducer. Processed results in the interface detection of a three layered adhesive sample of steel and rubber materials demonstrate that the wavelet filtering enhances the SNR about 12dB while the adaptive noise canceling narrows the dead zone effectively. 相似文献
52.
53.
Deformed Hartree-Fock calculations are performed for some light nuclei in a large configuration space consisting of first
four major shells. The interaction employed is the modified Skyrme interaction in which the deformed density is replaced by
the band averaged scalar density that makes the Hamiltonian rotationally invariant rendering the spectroscopic calculations
feasible. It is shown that the introduction of density dependence spreads out the energy spectra and that the Skyrme variant
SIV which has a weak density dependence gives best overall agreement for energy spectra and the available data for the electromagnetic
properties of the nuclei studied. It is found that the maximum contribution to the energy of any state in the low lying spectrum
comes from thes-state attractive ands-state repulsive parts of the Skyrme interaction. It is also shown that when two-body density dependent version of Skyrme
interaction is used, the Koopmans theorem no longer holds. 相似文献
54.
55.
56.
57.
58.
59.
Structural and optical properties of 1 at % Al-doped Zn1−xMgxO (x=0–8%) powders prepared by sol–gel method were systematically investigated by means of X-ray diffraction, scanning electron microscopy, ultraviolet–visible absorbance measurement, photoluminescence and Raman scattering spectra. All the powders retained the hexagonal wurtzite structure of ZnO. The band gap and near band emission energies determined from absorbance and photoluminescence spectra increased linearly with increasing Mg content, respectively, which implied that the Mg worked effectively on ZnO band gap engineering, irrespective of Al codoping. However, according to the PL and Raman scattering studies, for the sample of x=8%, the Al doping efficiency was decreased by higher Mg codoping. On the other hand, the effect of Mg codoping on photocatalytic degradation of methylene orange was explored experimentally. The substitution of Mg ions at Zn sites shifted the conduction band toward higher energies and then enhanced the photocatalytic activity, while the incorporation of interstitial Mg ions and decreased Al doping efficiency for higher Mg doping sample (x=8%) reduced the photocatalytic activity. 相似文献
60.
Accurate determination of both fundamental and optical gap is necessary for designing molecules relevant for organic photovoltaics. Here, we study how range-separated density functionals reproduce frontier orbital energies, HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) gaps, and optical gaps for molecules relevant for organic photovoltaics. In this study, we consider 12 different range-separated density functional for computing HOMO energy, HOMO–LUMO gap, and optical gap which are compared with available experimental and reported GW values. We found that the reproduction of desired photovoltaic properties primarily depend on range separation parameter. Moreover, the tested functionals are comparable with OT-BNL functional. 相似文献