全文获取类型
收费全文 | 226篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 147篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 26篇 |
物理学 | 50篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 22篇 |
2012年 | 13篇 |
2011年 | 26篇 |
2010年 | 14篇 |
2009年 | 14篇 |
2008年 | 17篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有235条查询结果,搜索用时 15 毫秒
31.
B. Nasr Esfahani M. Ahmadi F. Ahmadi 《International Journal of Theoretical Physics》2008,47(12):3130-3138
Fidelity for two-particle wave packets of spin-
particles moving around the Schwarzschild spacetime is discussed. Both acceleration and gravity cause to produce a Wigner
rotation that transforms the wave packet as it moves along a specified path in the gravitational field. For considered circular
paths, the fidelity between the spin parts of initial and final states of the system, called the spin fidelity, is obtained
as a function of angular velocity, elapsed proper time and radius of circular paths. For fixed elapsed proper time and angular
momentum of the centroid, there always exists one circular orbit with determined radius on which the fidelity of spin parts
is minimum. Using a numerical approach, the behavior of the spin fidelity in terms of the angular velocity, as well as the
radius of paths is described for both the spin singlet and spin triplet states. 相似文献
32.
Soumaya Touzani Hamada Imtara Shankar Katekhaye Hamza Mechchate Hayat Ouassou Ali S. Alqahtani Omar M. Noman Fahd A. Nasr Hugo Fearnley James Fearnley Anant Paradkar Ilham ElArabi Badiaa Lyoussi 《Molecules (Basel, Switzerland)》2021,26(15)
The biological activities of propolis samples are the result of many bioactive compounds present in the propolis. The aim of the present study was to determine the various chemical compounds of some selected propolis samples collected from Palestine and Morocco by the High-Performance Liquid Chromatography–Photodiode Array Detection (HPLC-PDA) method, as well as the antioxidant and antibacterial activities of this bee product. The chemical analysis of propolis samples by HPLC-PDA shows the cinnamic acid content in the Palestinian sample is higher compared to that in Moroccan propolis. The results of antioxidant activity demonstrated an important free radical scavenging activity (2,2-Diphenyl-1-picrylhydrazyl (DPPH); 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and reducing power assays) with EC50 values ranging between 0.02 ± 0.001 and 0.14 ± 0.01 mg/mL. Additionally, all tested propolis samples possessed a moderate antibacterial activity against bacterial strains. Notably, Minimum Inhibitory Concentrations (MICs) values ranged from 0.31 to 2.50 mg/mL for Gram-negative bacterial strains and from 0.09 to 0.125 mg/mL for Gram-positive bacterial strains. The S2 sample from Morocco and the S4 sample from Palestine had the highest content of polyphenol level. Thus, the strong antioxidant and antibacterial properties were apparently due to the high total phenolic and flavone/flavonol contents in the samples. As a conclusion, the activities of propolis samples collected from both countries are similar, while the cinnamic acid in the Palestinian samples was more than that of the Moroccan samples. 相似文献
33.
The electronic sensitivity and effectiveness of the pristine, Fe,- Mg-, Al- and Ga-doped ZnO nanoclusters interacted with 5-fluorouracil (5-FU) anticancer drug are theoretically investigated in the gas phase using the B3LYP/wB97XD density functional theory calculations with LANL2DZ basis set. It is concluded that 5-FU adsorption on the doped nanoclusters has relatively higher adsorption energy as compared with the pristine zinc oxide. A number of thermodynamic parameters, such as band gap energy (Eg), adsorption energy (Ead), molecular electrostatic potential, global hardness (η) and density of electronic states, are attained and compared. Also, calculated geometrical parameters and electronic properties for the studied systems indicate that Mg- and Ga-doped Zn12O12 present higher sensitivity to 5-FU compared with the pristine nanocluster. Theoretical results reveal that adsorption of 5-FU on the doped nanoclusters is influenced by the electronic conductance of the nanocluster. Therefore, Mg- and Ga-doped ZnO can be considered as promising nanobiosensors for detection of 5-FU in medicine. 相似文献
34.
Sufficient conditions for the oscillation of forced super-linear second order differential equations with oscillatory potential 总被引:2,自引:0,他引:2
A. H. Nasr 《Proceedings of the American Mathematical Society》1998,126(1):123-125
In the case of oscillatory potentials, we give sufficient conditions for the oscillation of the forced super-linear equation
This answers a question raised by J. S. W. Wong.
35.
Mohammad Javad Nasr Isfahani Maxym Myndyk Armin Feldhoff Vladimir Šepelák 《Journal of magnetism and magnetic materials》2009,321(3):152-156
Mn0.5Zn0.5Fe2O4 nanoparticles (10-30 nm) have been prepared via mechanochemical processing, using a mixture of two single-phase ferrites, MnFe2O4 and ZnFe2O4. SQUID measurements (field-cooled magnetization curves and hysteresis loops) were performed to follow the mechanically induced evolution of the MnFe2O4/ZnFe2O4 mixture submitted to the high-energy milling process. The resulting single MnZn nanoferrite phase was characterized by SQUID (M-H curve), Faraday balance (M-T curve) and transmission electron microscopy. The magnetic characteristics of the mechanosynthesized material were compared with those of bulk Mn0.5Zn0.5Fe2O4. It was found that the saturation magnetization of nanostructured Mn0.5Zn0.5Fe2O4 (87.2 emu/g) is lower than that of the bulk Mn0.5Zn0.5Fe2O4, but, the Néel temperature of the sample (583 K) is higher than that of the bulk Mn0.5Zn0.5Fe2O4. 相似文献
36.
37.
Quantum Brownian motion of a rod-like particle is investigated in the frame work of system plus reservoir model. The quantum mechanical and classical limit for both translational and rotational motions are discussed. Correlation functions, fluctuation-dissipation relations and mean squared values of translational and rotational motions are obtained. 相似文献
38.
Let
\mathfrakA\mathfrak{A} be a normed algebra with identity, Ω be a locally compact Hausdorf space and λ be a positive Radon measure on Ω with supp(λ) = Ω. In this paper, we establish a necessary and sufficient condition for L
1(Ω,
\mathfrakA\mathfrak{A}) to be an algebra with pointwise multiplication. Under this condition, we then characterize compact and weakly compact left
multipliers on L
1(Ω,
\mathfrakA\mathfrak{A}). 相似文献
39.
In this paper, we deal with the Nagata ring R(n) in case R is obtained by a (T, I, D) construction. We characterize when R(n) is a strong S-domain and catenarian. This study allows us to provide several interesting applications and examples. 相似文献
40.
Mathematical Notes - Let Fq be a finite field, and let Fq[X] be the ring of polynomials with coefficients in Fq. A 2-Pisot element is a pair of algebraic integers of formal Laurent series over... 相似文献