全文获取类型
收费全文 | 100篇 |
免费 | 48篇 |
国内免费 | 56篇 |
专业分类
化学 | 76篇 |
数学 | 21篇 |
物理学 | 107篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 14篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 5篇 |
2005年 | 10篇 |
2004年 | 10篇 |
2003年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
排序方式: 共有204条查询结果,搜索用时 31 毫秒
51.
通过控制结晶法和浓度梯度进料的方式制备了Ni、Co和Mn三元素组分含量呈全梯度分布的类球形Ni0.7Co0.15Mn0.15(OH)2前驱体,与LiOH·H2O均匀混合并焙烧后获得LiNi0.7Co0.15O2正极材料,系统研究了不同焙烧温度对材料Ni、Co和Mn三元素扩散情况、晶体结构及电化学性能的影响规律。通过能谱仪(EDXS)分析不同焙烧温度下材料颗粒中Ni、Co、Mn三元素的扩散程度。研究结果表明,在800℃下焙烧得到的正极材料梯度分布特征明显且电化学性能最佳,首次放电比容量为186.1 mAh·g-1(2.8~4.3 V,0.2C),2C大倍率充放电条件下循环200次后容量保持率为90.1%。这种材料兼具高比容量及良好的循环稳定性,可以用作下一代高能量密度锂离子电池正极材料。 相似文献
52.
从实验和理论上研究了受激布里渊散射(SBS)光脉冲波形.在Nd∶YAG调Q激光器中实验研究了SBS光脉冲波形随抽运光参数、结构参数和介质参数的变化规律,并利用SBS理论模型进行了数值模拟,实验与数值模拟结果的变化趋势基本一致.结果表明,抽运光能量越小,透镜焦距越短,镜-池间距越长,介质声子寿命越长,SBS光脉冲波形就越不容易出现调制现象.分析和讨论了抽运光参数、结构参数和介质参数对SBS光脉冲波形的影响机理.
关键词:
受激布里渊散射
脉冲波形
抽运光参数
结构参数 相似文献
53.
HASI Wuliji 《中国科学G辑(英文版)》2007,50(2):144-151
In this paper,a method of choosing mixture medium in two-cell stimulated Brillouinscattering(SBS)system to improve the system performance is proposed.The Brillouin frequency shift(BFS)of mixture medium varies with the mixing ratio andthus the difference of the BFS between the two cells can be eliminated.The two-cellSBS system with acetone(C3H6O)in its generator cell and mixture liquid ofCCl4/C2Cl4 in its amplifier cell is investigated.The C3H6O has a high optical breakdown threshold and the mixture liquid of CCl4/C2Cl4 has a small absorption coeffi-cient and the same BFS as that of C3H6O when the volume fraction of CCl4 is 4%.Compared with two-cell SBS system with the same liquid(C2Cl4)or different liquid(C3H6O and C2Cl4)in generator and amplifier cell,the SBS system with mixture liq-uid(CCl4/C2Cl4)in amplifier cell and C3H6O in generator cell improves thepower-load,energy reflectivity(ER),phase conjugation(PC)fidelity and ER stabil-ity. 相似文献
54.
Hasi WULAN 《数学学报(英文版)》2005,21(6):1415-1424
Suppose that φ is an analytic self-map of the unit disk Δ. We consider compactness of the composition operator Cφ from the Bloch space B into the spaces QK defined by a nonnegative, nondecreasing function K(r) for 0 ≤ r 〈 Cφ. Our compactness condition depends only on Φ which can be considered as a slight improvement of the known results. The compactness of Cφ from the Dirichlet space D into the spaces QK is also investigated, 相似文献
55.
Rauno Aulaskari Hasi Wulan Ruhan Zhao 《Proceedings of the American Mathematical Society》2000,128(8):2329-2335
For let be the Möbius transformation defined by , and let be the Green's function of the unit disk . We construct an analytic function belonging to for all , , but not belonging to meromorphic in and for any , . This gives a clear difference as compared to the analytic case where the corresponding function spaces ( and ) are same.
56.
A method to measure the Brillouin frequency shift of the medium through Brillouin amplification ratio 下载免费PDF全文
In order to measure the Brillouin frequency shift (BFS) of the
medium, this paper proposes a method using mixtures in a two-cell
stimulated Brillouin scattering system, which uses a medium to be
measured as amplifier medium and a mixture medium as generator
medium. The seed light from the generator gains effective
amplification in the amplifier and the amplification ratio changes
with the mixing fraction. Only when the BFS of the mixture medium is
equal to that of the medium in the amplifier does the seed light
obtain the maximum amplification ratio. The method has the advantage
of independence of the wavelength of the incident light. 相似文献
57.
XU Yan-Bing 《中国物理C(英文版)》2004,28(6):601-606
Using modified surface delta interaction, the deformed Hartree-Fock calculations for twenty two nuclei such as 102—114Ru, 102—116Pd,104—116Cd etc. are performed in the gds and gdsh configuration space, respectively. Prolate and oblate configurations are obtained. It is shown that there exist shape transitions for the nuclei with the mass number from 102 to 116, the resultant single-particle energy spectrum is changed not only with the mass number but also with the configuration, and the results, by considering the 1h11/2 orbit, are quite different from those obtained in the gds configuration space. Moreover, the number of protons in the nucleus and filling up the 1h11/2 orbit, especially with neutrons, play important roles in the single-particle energy spectrum and the shape transition. 相似文献
58.
A Fejér-Riesz inequality for the weighted Besov spaces B
p,q
is given. Some characterizations of functions in B
p,q
in terms of their Taylor coefficients are obtained. 相似文献
59.
Xiang Lin Wu‐Li‐Ji Hasi Xiu‐Tao Lou Shuang Lin Fang Yang Bao‐Shen Jia Yu Cui De‐Xin Ba Dian‐Yang Lin Zhi‐Wei Lu 《Journal of Raman spectroscopy : JRS》2014,45(2):162-167
Surface‐enhanced Raman spectroscopy (SERS) was used for rapid detection of sodium thiocyanate in milk employing silver aggregates as active substrate. Silver nanoparticles were induced to silver aggregates by trichloroacetic acid (TCA). The limit of detection (LOD) for sodium thiocyanate was 10−2 µg ml−1 in water with an analytical enhancement factor of 5.4 × 106. The silver aggregates represent good reproducibility and stability. Good linear relationship was obtained for sodium thiocyanate in milk at concentration ranges from 0.1 to 10 µg ml−1 (R2 = 0.995). Using TCA as protein precipitator, silver colloid would aggregate spontaneously when mixing with samples during SERS measurement without the need of additional aggregating agent. The simple pretreatment procedures and analytical methods are less time consuming (<10 min) and environmentally friendly, making the proposed method much practical for in situ detection of sodium thiocyanate in market milk. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
60.
Wei Huang Qi Su Xia Wu Yan-Bing Li Ying Sun 《International Journal of Theoretical Physics》2014,53(9):2891-2901
A robust and efficient quantum key agreement (QKA) protocol is presented with decoherence-free (DF) states and single-particle measurements. Compared with all the previous QKA protocols, which are designed in ideal condition, this protocol can not only guarantee both the security and fairness of the shared key but also be immune to collective decoherence. In addition, our protocol has a high intrinsic efficiency due to the utilization of the delayed measurement technique. Finally, we show that the proposed protocol is secure against the attacks from both outside eavesdroppers and inside dishonest participants. 相似文献