全文获取类型
收费全文 | 128篇 |
免费 | 7篇 |
国内免费 | 12篇 |
专业分类
化学 | 48篇 |
晶体学 | 18篇 |
力学 | 36篇 |
综合类 | 1篇 |
数学 | 12篇 |
物理学 | 32篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 8篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有147条查询结果,搜索用时 16 毫秒
21.
High-quality centimeter-sized single crystals of La1.2Sr1.8−yCayMn2O7 (0.0y0.2) were successfully grown using a floating zone method associated with an image furnace. We present the growth conditions together with a characterization of the single crystals by means of optical and electron microscopy, EDX and ICPAES analysis, DTA-TGA measurements and redox titration, X-ray powder diffraction, Laue X-ray back-reflection and neutron diffraction. We also stress the main aspects of the complex thermodynamical and kinetic behaviors of these compounds. 相似文献
22.
Xiu-li Yan Xing Wu Jian-fei Zhou Zhi-guo Zhang Jinguo Wang 《Journal of Crystal Growth》2000,220(4):543-547
High optical quality Er3+:YVO4 laser crystals have been grown by using the floating zone method (FZ). The spectroscopic properties and 3 μm lasing of Er3+:YVO4 were investigated. It is found that the Er3+ concentration has a negative effect on the emission of the transition 4I13/2→4I15/2(1.55 μm ), and a positive effect on that of the 4I11/2→4I13/2 transition (2.68 μm). With direct upper-state pumping and a plane-concave cavity a self-terminating laser was achieved at the wavelength of 2.724 μm in the 30 at% Er3+ doped sample. 相似文献
23.
DOPC,DOPE和神经酰胺对鞘磷脂/胆固醇双层膜结构的影响 总被引:1,自引:1,他引:0
用LB技术和原子力显微镜(AFM)研究了1,2-二油酸甘油-3-磷脂酰胆碱(DOPC)、1,2-二油酸甘油-3-磷脂酰乙醇胺(DOPE)和神经酰胺(Ceramide)对鞘磷脂(SM)/胆固醇(Chol)结构的影响. 实验结果表明, 在表面压力较低时, 每种混合脂双层膜都呈现均匀分布的脂双层结构. 随着表面压力的增加, 形态发生了明显的变化: (1) SM/Chol二元组分双层膜形成均一的液态有序相微区结构, 衬底覆盖率达到80%; (2) DOPC的加入促使SM/Chol双层膜出现相分离现象, SM/Chol形成的液态有序相 “岛状” 微区结构漂浮在液态无序相的DOPC上部, 约占总面积的30%; (3) DOPE与SM/Chol形成的双层膜明显不同于DOPC/SM/Chol, 呈现出液态无序相、液态有序相及凝胶相3相共存的结构; (4) Ceramide诱导了SM/Chol双层膜结构发生重排, 两层脂分子间发生翻转形成囊泡结构, 部分神经酰胺从液态有序相中分离形成小颗粒结构. 在较高膜压下, 各系统都呈现出具有特定形态的双层膜结构. 分子官能团的成键能力决定了双层膜形态结构. 相似文献
24.
一种新型铅钐锡正极板栅合金 总被引:1,自引:0,他引:1
目前,铅钙锡合金已广泛用作阀控式铅酸蓄电池(VRLAB)的板栅材料.由于钙的存在,使铅钙锡合金阳极氧化时易形成高阻抗的阳极腐蚀层,并出现晶间腐蚀,电池循环充放电能力仍不理想.为克服铅钙锡合金作为正极板栅材料的不利因素. 相似文献
25.
《Current Applied Physics》2020,20(1):96-101
Sr-doped single crystals (C1-xSx)12A7:e− (x = 0, 0.01, 0.02, 0.03) were successfully fabricated by floating zone method. It is found that Sr-doping decreases the reduction time from 30 h to 20 h. The maximum emission current of (C1-xSx)12A7:e− is greatly improved by 50% than that of the un-doped. The DFT calculations show Sr-doping in C12A7 contributed to the free O2− in the cages spread out, leading to a short reduction time; increase the “window” between two adjacent cages that is conducive to the electrons in cages to escape. And the work function of the (C1-xSx)12A7:e− is lower than that of C12A7:e−. 相似文献
26.
27.
MM-4中电位和分布实验 总被引:1,自引:1,他引:0
本文描述了用静电探针测量探针悬浮电位的方法,给出了MM-4电位分布的实验结果。结果表明,轴向电位分布不对称;在等离子体中沿轴向和径向存在双离子位阱。在离子能谱测量中观察到双离子温度。产生这样电位分布的机制,归于会切系统中的斯托沫区和电子枪的不同工作方式。测量的等离子体电位为-200——300V。 相似文献
28.
Reyhaneh Rahnama Parichehr Farrokhmanesh 《International journal of environmental analytical chemistry》2018,98(3):247-257
A rapid, simple, and sensitive method was developed for lead preconcentration and separation in various real samples by dispersive liquid–liquid microextraction based on the freezing of floating organic drop. In this method, a suitable extraction solvent dissolved in a dispersive solvent was quickly syringed into the water sample so that the solution became turbid. Then, two phases were separated by centrifugation. The floating extractant droplet can be easily solidified on an ice bath and taken out of the water sample. Then, it can be liquefied instantly at room temperature, and analyte can be determined in it. In the creation of a hydrophobic complex with lead, 1-(2-pyridylazo)-2-naphthole (PAN) was used as the chelating agent. 1-Undecanol and acetone were used as extraction and disperser solvent. To achieve the highest recovery, some factors (type and volume of dispersive and extraction solvent, pH, PAN concentration, and salt concentration) were optimised. Under optimised conditions (pH = 9, 1.0 × 10–3 mol L?1 PAN, 15% w/v NaCl, 100 µL 1-undecanol, and 0.3 mL acetone), the lead calibration graph was linear from 1.5 to 80 μg L?1. The detection limit and preconcentration factor were 0.5 μg L?1 and 50, respectively. Lead was successfully determined in water and food (spinach, rice, potato, carrot, and black tea bag) samples by this method. 相似文献
29.
In this research, the complete general formulas for the analytical second derivative of the molecular integrals for spherical gaussian orbitals of electronic energy are presented. Formulas were given for the second derivative for orbital exponent, orbital and nuclear cartesian coordinates and coefficients of contracted gaussians. In order to save computational time, the formulas for the second derivative are written in terms of the original integrals. Although the formulas were presented in general for any type of application, the Floating Spherical Gaussian Orbital (FSGO) method is applied to some molecules such as LiH, H2O and CH2 (singlet) to check the formulas. The results were compared with the results of the finite difference method. Besides the accuracy of the analytical derivative, the saving in computational time is significant. 相似文献
30.
Takio Hikono Takashi Fuyuki Ichiro Yamashita Masaki Takeguchi 《Surface science》2006,600(13):2817-2822
For application to floating nanodots gate memory, ferritin core, ferrihydrite nanodot, array was made and reduced to be conductive. Ammonia plasma treatment was employed to reduce the ferrihydrite cores. X-ray photoelectron spectroscopy analysis confirmed that the plasma treated cores embedded in a SiN film are successfully reduced from ferrihydrite to metal iron. It was elucidated that hydrogen radicals or ions in the plasma combine with oxygen atoms in the core and, consequently, the core is reduced to a conductive state. Transmission electron microscope analysis before and after the treatment showed that the reduced core size was smaller than ferrihydrite core by approximately 2 nm, which is consistent with theoretical calculation of the shrink size accompanying core reduction to α-Fe. The plasma treated cores embedded in SiO2 film are found to be iron oxides, which indicates that the metal iron nanodots are vulnerable to oxygen and easy to be reoxidized. 相似文献