全文获取类型
收费全文 | 480篇 |
免费 | 101篇 |
国内免费 | 19篇 |
专业分类
化学 | 90篇 |
晶体学 | 14篇 |
力学 | 1篇 |
综合类 | 1篇 |
数学 | 40篇 |
物理学 | 454篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 11篇 |
2012年 | 12篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 78篇 |
2008年 | 80篇 |
2007年 | 47篇 |
2006年 | 36篇 |
2005年 | 27篇 |
2004年 | 24篇 |
2003年 | 31篇 |
2002年 | 23篇 |
2001年 | 24篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1974年 | 1篇 |
排序方式: 共有600条查询结果,搜索用时 46 毫秒
71.
P. M. Bhujbal 《辐射效应与固体损伤》2013,168(6):428-435
The lyoluminescence (LL), thermoluminescence and mechanoluminescence (ML) of a γ -ray-irradiated powder of NaCl:Dy (0.05–0.5 mol%) phosphor are reported in this paper. The nature of intensity variation of the respective luminescence spectra with different γ -ray doses and with different concentrations of Dy3+ doped in NaCl are found to be similar. The LL and ML intensities differed from each other, but their nature is found to be similar in a sublinear form up to a high dose (5.0 kGy) of γ -rays. Thus, the prepared phosphor may be useful for accidental radiation dosimetry up to a high dose (5.0 kGy) of γ -rays using the LL and ML techniques. 相似文献
72.
Doubly nonnegative matrices arise naturally in many setting including Markov random fields (positively banded graphical models) and in the convergence analysis of Markov chains. In this short note, we settle a recent conjecture by C.R. Johnson et al. [Charles R. Johnson, Brian Lins, Olivia Walch, The critical exponent for continuous conventional powers of doubly nonnegative matrices, Linear Algebra Appl. 435 (9) (2011) 2175–2182] by proving that the critical exponent beyond which all continuous conventional powers of n-by-n doubly nonnegative matrices are doubly nonnegative is exactly n−2. We show that the conjecture follows immediately by applying a general characterization from the literature. We prove a stronger form of the conjecture by classifying all powers preserving doubly nonnegative matrices, and proceed to generalize the conjecture for broad classes of functions. We also provide different approaches for settling the original conjecture. 相似文献
73.
74.
P. Khare D. Sa 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):205-209
Using a phenomenological Landau theory, the size dependence on ferroelectric
transition for free-standing long cylindrical nanoparticles is discussed.
We derive
the size dependence of the transition temperature, polarization profile as
well as the static susceptibility. The transition temperature vanishes below
a critical size where the static susceptibility shows divergence obeying
Curie-Weiss law. In order to make this result compared with experiments,
the average polarization and the susceptibility is computed with a Gaussian
particle size distribution. The average polarization in such a case shows
smearing with respect to the particle size whereas the divergence in the
susceptibilty gets rounded. This might correspond to a size dependent soft
mode which can be observed in Raman measurement. 相似文献
75.
Jun-Gill Kang Tack-Jin Kim Hee-Jung Kang Younbong Park Min-Koo Nah 《Journal of luminescence》2008,128(12):1867-1872
Two novel complexes of Sm(III) and Dy(III) with mixed oxydiacetate (ODA) and 1,10-phenanthroline (phen) ligands were synthesized and their structure and luminescence properties were characterized. The complexes of [Ln(ODA)(phen)·4H2O]Cl·5H2O [Ln=Sm and Dy] crystallize in the monoclinic space group P21/n with Sm: a=12.3401(14) Å, b=16.821(2), c=12.6847(11) Å, β=107.939(10)°, V=2505.0(5) Å3, Z=4 and ρ=1.841 mg/m3, and with Dy: a=12.289(7) Å, b=16.805(6) Å, c=12.705(4) Å, β=108.144(18)°, V=2493.4(19) Å3, Z=4 and ρ=1.786 mg/m3. The complexes of [Sm(ODA)(phen)·4H2O]+ and [Dy(ODA)(phen)·4H2O]+ excited by UV light produce orange red and lightly white emissions, respectively, via the nonradiative energy transfer from phen to the metals. The quantum yield of the sensitized luminescence of [Dy(ODA)(phen)·4H2O]+ (Q=19%) is much greater than that of [Sm(ODA)(phen)·4H2O]+ (Q=1.4%). The luminescence decay times of the complexes were in a few microsecond range and independent of temperature. 相似文献
76.
(Na0.52K0.44Li0.04)Nb0.9-xSbxTa0.1O3 Lead-Free Piezoelectric Ceramics with High Performance and High Curie Temperature
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
(Na0.52K0.44Li0.04)Nb0.9-x Sbx Ta0.1O3 lead-free piezoelectric ceramics are prepared by a solid-state reaction method. With increasing Sb content, the transition temperature from orthorhombic to tetragonal polymorphic phase decreased. A composition (Na0.52K0.44Li0.04)Nb0.863Sb0.037Ta0.1O3 is found to possess excellent piezo- electric and electromechanical performances (d33 = 306pC/N, kp =48%, and kt=50%), and high Curie temperature (Tc = 320 ℃). These results indicate that (Na0.52K0.44Li0.04)Nb0.863Sb0.037 Ta0.1O3 is a promising lead-free piezoceramics replacement for lead zirconate titanate. 相似文献
77.
Phase Transition and High Piezoactivity of Sr Doped Lead-Free (Na0.53K0.422Li0.048) (Nb0.89Sb0.06Wa0.05)O3 Ceramics
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lead-free piezoelectric ceramics (Na0.53K0.422Li0.048 ) (Nb0.89Sb0.06 Ta0.05 )03 (NKLNST) + x tool SrCO3 are prepared by conventional solid state sintering method. The specimens with pure perovskite structure show tetragonal phase at x 〈 0.01, and become pseudo-cubic phase at x 〉 0.02. A lattice parameter discontinuity is found in the specimens with 0.004 〈 x 〈 0.0075, along with a great improvement in piezoactivity. The 0.004 mol SrCO3 added NKLNST ceramics possesses outstanding performances of kp = 0.53, kt = 0.26, and d33=309 pC/N. Moreover, the Sr^2+ modification inhibits the gra/n growth, decreases the Curie temperature, and induces a diffuse phase transition. 相似文献
78.
We calculate the reflection probability for ultracold alkali atoms incident on a solid surface. By considering the interatomic interaction and using the WKB method, it is shown that the repulsive interaction between atoms has the effect of increasing the reflection probability. The increasing amplitude is related with the interatomic interaction and the depth of atom-surface potential. In addition, we also perform a numerical calculation to testify the effect of the interatomic interaction, and the analytic result is proven by the numerical result. 相似文献
79.
Effects of Li Substitution and Sintering Temperature on Properties of Bi0.5(Na,K)0.5TiO3 Lead-Free Piezoelectric Ceramics
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bi0.5 (Na0.72K0.28- x Lix )0.5 TiO3 (BNKLT- 100x) lead-free piezoelectric ceramics are synthesized by conventional solid state sintering techniques. The dielectric and piezoelectric properties of the BNKLT-100x ceramics as a function of Li content are systematically investigated. It is found that not only Li content but also the sintering temperature has a strong effect on the piezoelectric properties of BNKLT. The piezoelectric constant d33 Of BNKLT varies from 120 to 252pC/N in the Li content range from 0.03 to 0.16. In the sintering temperature range from 1080 to 1130℃, the d33 value of BNKLT-6 changes from 200pC/N to 252pC/N. The BNKLT-6 sample sintered at 1100℃ has the highest piezoelectric constant d33 of 252pC/N, with the electromechanical coupling factors kp of 0.32 and kt of 0.44. 相似文献
80.
It is shown that the differential form of Friedmann equations of Friedman--Robertson--Walker (FRW) universe can be recast as a similar form of the first law ThdSh = dE + WdV of thermodynamics at the apparent horizon of FRW universe filled with the viscous fluid. It is also shown that by employing the general expression of temperature associated with the apparent horizon of an FRW universe and assumed that the temperature Tm of the energy inside the apparent horizon is proportional to the horizon temperature Tm= bTh, we are able to show that the generalized second law of thermodynamics holds in the Einstein gravity provided Th-Tm/r~A ≤(ρ+P~). 相似文献