全文获取类型
收费全文 | 3552篇 |
免费 | 893篇 |
国内免费 | 307篇 |
专业分类
化学 | 1410篇 |
晶体学 | 48篇 |
力学 | 232篇 |
综合类 | 33篇 |
数学 | 147篇 |
物理学 | 2882篇 |
出版年
2023年 | 21篇 |
2022年 | 51篇 |
2021年 | 52篇 |
2020年 | 69篇 |
2019年 | 54篇 |
2018年 | 64篇 |
2017年 | 129篇 |
2016年 | 130篇 |
2015年 | 135篇 |
2014年 | 239篇 |
2013年 | 267篇 |
2012年 | 300篇 |
2011年 | 262篇 |
2010年 | 222篇 |
2009年 | 241篇 |
2008年 | 274篇 |
2007年 | 254篇 |
2006年 | 211篇 |
2005年 | 245篇 |
2004年 | 169篇 |
2003年 | 178篇 |
2002年 | 153篇 |
2001年 | 139篇 |
2000年 | 101篇 |
1999年 | 85篇 |
1998年 | 78篇 |
1997年 | 89篇 |
1996年 | 65篇 |
1995年 | 68篇 |
1994年 | 54篇 |
1993年 | 49篇 |
1992年 | 36篇 |
1991年 | 43篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 23篇 |
1987年 | 25篇 |
1986年 | 22篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有4752条查询结果,搜索用时 922 毫秒
51.
Nitro musks in cosmetic products—determination by headspace solid-phase microextraction and gas chromatography with atomic-emission detection 总被引:1,自引:0,他引:1
Summary The combination of headspace solid-phase microextraction with atomic-emission detection enables highly selective and sensitive
determination of itro musk compounds in cosmetic products. Sample preparation is considerably simplified; there is no solvent
extraction step. Enrichment is influenced by the type and amount of cosmetic product investigated. The lowest amount giving
well detectable peaks is 1 mg musk compound per kg sample. Calibration curves obtained from spiked solutions of selected reference
cosmetics in water show very good linearity. Relative standard deviations of peak areas from repeated measurements are usually
<10%.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
52.
53.
References: 《理论物理通讯》2007,48(9):428-430
By virtue of the technique of integration within an ordered product of operators, we derive the normal ordering expansion of a one- and two-mode combination squeezing operator for two harmonic oscillators with coordinatemomentum coupling. It turns out that this squeezing operator just diagonalizes the Hamiltonian H = p21/2m1 m1ω21x21/2 p22/2m2 m2ω22x22/2 - λx2p1, so its ground state is a one- and two-mode combination squeezed state.Quantum fluctuation in the ground state is calculated. 相似文献
54.
The supersymmetric WKB approximation of ring-shaped oscillator potential in r and θ dimensions with spherical polar coordinates 下载免费PDF全文
According to calculation of the energy spectrum of ring-shape oscillator potential by using the supersymmetric WKB approximation, it is shown that the energy spectrum of some noncentral separable potentials can be exactly obtained in r and θ dimensions by above method. 相似文献
55.
S. Burachas S. Beloglovsky D. Elizarov I. Makov Yu. Saveliev N. Vassilieva M. Ippolitov V. Manko S. Nikulin A. Nyanin A. Vasiliev A. Apanasenko G. Tamulaitis 《Radiation measurements》2004,38(4-6):367-370
Technological conditions ensuring growth of optically homogeneous lead tungstate (PWO) crystals are reported. It is shown that the basic scintillator characteristics of PWO grown from highly purified raw material and properly doped with lanthanides are mainly determined by inclusions of oxides W1−yLyO3−x (L=Y, La, Gd; 0<x<0.3). Moreover, surface-located inclusions with structure close to tungstenite may also be of importance. It is demonstrated that the scintillation properties can be intentionally designed by varying the oxygen content in the inclusions x and the surface structure. The optimal value for x and the most favorable surface structure are achieved by proper thermal regimes and environment content during the crystal annealing. The results enabled low-cost fabrication of PWO scintillators with steady and reproducible characteristics acceptable for the CERN project ALICE and ensured production of PWO on an industrial scale by “North Crystals” company at a rate of 125–135 crystals per year from every growth apparatus. 相似文献
56.
57.
58.
S. Y. Wang S. C. Chen S. D. Lin C. J. Lin C. P. Lee 《Infrared Physics & Technology》2003,44(5-6):527-532
InAs/GaAs quantum dot infrared photodetectors were fabricated with quantum dots grown at three different temperatures. Large detection wavelength shift (5–14.5 μm) was demonstrated by changing 40 degrees of the epitaxy temperature. The smaller quantum dots grown at lower temperature generate 14.5 μm responses. The detectivity of the normal incident 15 μm QDIP at 77 K is 3 × 108 cm Hz1/2/W. A three-color detector was also demonstrated with quantum dots grown at medium temperature. The three-color detection comes from two groups of different sizes of dots within one QD layer. This new type of multicolor detector shows unique temperature tuning behavior that was never reported before. 相似文献
59.
60.
我们对多电子束契伦柯夫自由电子激光进行了首次实验研究。280A,500kV的电子束被引入一多介质矩形谐振腔,在频率为33.4GHz处产生了1.7MW的契伦柯夫相干受激辐射。互作用效率为1.2%。 相似文献