全文获取类型
收费全文 | 356篇 |
免费 | 38篇 |
国内免费 | 46篇 |
专业分类
化学 | 180篇 |
晶体学 | 5篇 |
力学 | 24篇 |
数学 | 12篇 |
物理学 | 219篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 30篇 |
2012年 | 15篇 |
2011年 | 22篇 |
2010年 | 12篇 |
2009年 | 14篇 |
2008年 | 19篇 |
2007年 | 34篇 |
2006年 | 18篇 |
2005年 | 24篇 |
2004年 | 15篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 15篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 12篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有440条查询结果,搜索用时 578 毫秒
91.
92.
多次漫反射法测量粉末中的杂质吸收光谱及其计算机模拟 总被引:1,自引:0,他引:1
本文提出了用多次漫反射法来测定粉末样品的杂质吸收光谱,其结果与同材料的透明片状样品的杂质吸收光谱基本一致,为了验证更普遍的对不同折射率粉末情况,文中采用假设模型,以计算机模拟方法,其所得的结果说明,当颗粒足够小,色散又不太大时,所得的粉末样品与透明片状样品的吸收光谱一致,只差一个未知的吸收光程,如再与另一特性参数(寿命或量子效率)测量相结合,即可用来确定稀土杂质在材料中的辐射跃迁几率等物理参数。 相似文献
93.
J. Kristóf M. Tóth M. Gábor P. Szabó R. L. Frost 《Journal of Thermal Analysis and Calorimetry》1997,49(3):1441-1448
Intercalation complexes of three different Hungarian kaolinites with hydrazine and potassium acetate were investigated by FT-IR (DRIFT) spectrometry, X-ray diffraction, and thermogravimetry combined with mass spectrometry. Differences were found in the thermal behaviour of the complexes as well as in the rehydration — reexpansion patterns of the heated intercalates. An XRD method is proposed for the distinction of kaolinite and 7.2 Å halloysite present in the same mineral.The authors wish to thank Dr. E. Máttyás for providing the kaolinite samples and for carrying out their chemical analysis. Financial support from the Hungarian Scientific Research Fund under grant No. OTKA-014179 is gratefully acknowledged. 相似文献
94.
基于球扩展光源模型的物体三维形状的恢复 总被引:3,自引:1,他引:2
计算机视觉中传统的物体三维形状恢复方法大都基于光源是无穷远点光源的假设,如由单幅图像恢复三维形状(shapefromshading)光度立体视觉(photometricstereo)方法等。实际环境中的光源往往不能满足这个假设,因此大大限制了这些方法的应用,本文提出了一种更加实用的球扩光源模型,并推导出此光源下反射物体表面的反射图,此模型在三维坐标系中描述了球光源位置,亮度,漫反射物体表面反射度与 相似文献
95.
The temperature variation of the Debye-Waller factors of Cs+ and Br− ions in CsBr powder has been studied using powder X-ray diffraction. The integrated intensities of the Bragg peaks at different
temperatures have been obtained. These results have been verified by structure factor least squares refinement program. Theoretical
shell model lattice dynamical calculations have been done using a 7-parameter model in the harmonic approximation and the
values compared with the present X-ray measurements. The observed intensities have been corrected for first order thermal
diffuse scattering. 相似文献
96.
97.
The polycrystalline samples of Pb(Li1/4Dy1/4W1/2)O3 have been synthesized by high-temperature solid-state reaction techniques. Room temperature X-ray diffraction (XRD) studies
of the compound provided preliminary structural data, and hence formation of a single phase desired material was confirmed.
Detailed studies of dielectric constant (ε) and loss (tanδ) as a function of frequency (100 Hz to 10 kHz) at room temperature (298 K) and also as a function of temperature (liquid
nitrogen to 403 K) at 10 kHz suggest that the compound undergoes a ferroelectric phase transition of diffuse type. 相似文献
98.
研制了一台多参数的主被动船载蓝绿光海洋激光雷达系统(BLOL),它可用于我国东海海域的海色遥感印证。该海洋激光雷达系统能被动地测量离水辐亮度Lw,主动测量漫散射衰减系数k和叶绿素a浓度C。雷达系统安装在青岛海洋大学的调查船上(约2500吨位),曾在21个站位进行了实验。实验的区域从上海东开始到冲绳岛附近。用该海洋激光雷达系统测量的结果与用传统的方法测量的结果符合的很好。 相似文献
99.
We state and analytically solve the linearized problem of the reflection of plasma waves from the half-space boundary in gas
plasma for the first time. We consider mirror and diffusion boundary conditions and find the reflection coefficient as a function
of the original problem parameters. We analyze the long-wave limit.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 150, No. 3, pp. 498–510, March, 2007. 相似文献
100.
R.S. Tiwari P. Mandal O.N. Srivastava 《Progress in Crystal Growth and Characterization of Materials》1997,34(1-4):271-285
Amongst the non-aluminium based quasicrystalline alloys, investigations of titanium containing alloys in regard to the occurrence and stability of quasicrystalline phases have aroused considerable interest in recent years. Employing X-ray and TEM techniques a systematic investigation of the influence of substitution for Fe by Si and Ni on the stability of icosahedral phase in rapidly quenched Fe-Ti alloy has been carried out. The occurrence of metastable phases including commensurately modulated phase and the decagonal phase in Fe-Ti-Si system have been found. In addition, the occurrence ofstructural disorder manifested by arcs of diffuse scattering in diffraction patterns and anisotropy in the shape of idffraction spots has also been pointed out. It has been observed that 6 at.% of Si in Fe-Ti-Si system results in the formation of single-phase icosahedral quasicrystals. We have shown that contrary to some earlier reported results on Ti2Ni, Ti2Ni(Si) and Ti56Ni23Fe5Si16 alloys do not possess the icosahedral phase. In Ti68Fe26−xNixSi6 alloy system, icosahedral phase formation ability is limited to the value of x < 9. The occurrence of icosahedral phase in these alloy systems has been analysed in terms of e/a ratio. 相似文献