首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   187篇
  免费   4篇
化学   135篇
晶体学   4篇
力学   5篇
数学   12篇
物理学   35篇
  2020年   2篇
  2019年   2篇
  2016年   2篇
  2015年   6篇
  2014年   2篇
  2013年   5篇
  2012年   12篇
  2011年   12篇
  2010年   21篇
  2009年   9篇
  2008年   13篇
  2007年   7篇
  2006年   6篇
  2005年   4篇
  2004年   3篇
  2003年   1篇
  2002年   3篇
  2000年   2篇
  1999年   4篇
  1998年   1篇
  1997年   3篇
  1996年   3篇
  1995年   2篇
  1994年   3篇
  1993年   5篇
  1992年   2篇
  1990年   1篇
  1989年   4篇
  1988年   1篇
  1987年   5篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1983年   5篇
  1982年   3篇
  1981年   2篇
  1980年   4篇
  1979年   1篇
  1978年   4篇
  1977年   3篇
  1973年   1篇
  1972年   4篇
  1968年   1篇
  1967年   3篇
  1966年   1篇
  1965年   1篇
  1962年   1篇
  1961年   1篇
  1954年   1篇
  1897年   1篇
排序方式: 共有191条查询结果,搜索用时 21 毫秒
31.
Pionic 3He atoms have been produced in a gaseous target. Energies and strong absorption broadening of the 2 → 1 and the 3 → 1 transition lines have been measured. The 1s level is shifted by 44 ± 5 eV by the (attractive) strong interaction, and the natural 1s level width is 42 ± 14 eV.  相似文献   
32.
33.
It is suggested that the ideal smectic-C reorientation model be modified to include both some rotational slipping of the smectic-C domains and hindered reorientation of a small percentage of molecules to account for the behaviour of proton NMR in smectic-C di-heptyloxyazoxybenzene. The calculated poly-domain line shapes are rather insensitive to the characteristic biaxial order parameter predicted by molecular models of the smectic-C phase.  相似文献   
34.
Similarities and differences : Far‐infrared spectra of protic ionic liquids could be assigned to intermolecular bending and stretching modes of hydrogen bonds. The characteristics of the low‐frequency spectra resemble those of water. Both liquids form three‐dimensional network structures, but only water is capable of building tetrahedral configurations. EAN: ethylammonium nitrate, PAN: propylammonium nitrate, DMAN: dimethylammonium nitrate.

  相似文献   

35.
Three new uranyl tungstates, α-, β-Cs(2)[(UO(2))(2)(W(2)O(9))], and Rb(6)[(UO(2))(7)(WO(5))(2)(W(3)O(13))O(2)], have been obtained by high temperature solid state reactions. All three compounds display novel structure topologies: α- and β-Cs(2)[(UO(2))(2)(W(2)O(9))] are based upon layers with a new topology that can be related to the uranophane topology; Rb(6)[(UO(2))(7)(WO(5))(2)(W(3)O(13))O(2)] is a rare example of a non-molecular inorganic phase with layers containing oxo-tungstate trimers. The structural relationship between α- and β-Cs(2)[(UO(2))(2)(W(2)O(9))] can be assigned to polytypism.  相似文献   
36.
37.
We propose a new method for measuring the difference $\Delta f = f(0) - \bar f(0)$ of the forward scattering amplitudes for K0 and $\bar K^0 $ by use of decay rates of initially pure strangeness states after passage through a regenerator. The phenomenology of coherent kaon regeneration is presented for arbitrary mixtures of K0 and $\bar K^0 $ .  相似文献   
38.
39.
Abstract— Near-infrared Fourier transform Raman spectroscopy is an analytical, nondestructive technique that provides information about the molecular structure of the investigated sample. The molecular structure of proteins and lipids differs between neoplastic and normal tissues and therefore Raman spectroscopy has been considered promising for the diagnosis of cancer. We aimed to compare the molecular structure of normal skin, benign and malignant skin lesions by the near-infrared Fourier transform Raman spectroscopy. Biopsies were obtained from the following skin lesions: skin tag, dermatofibroma, seborrhoeic keratosis, actinic keratosis, keratoacan-thoma, basal cell carcinoma, squamous cell carcinoma, nevus intradermal, nevus compositus, dysplastic nevus and lentigo maligna. Control skin was harvested from the vicinity of these lesions. In the Raman spectra, the secondary structure of the proteins was reflected by the amide vibrations of peptide bonds. The principal lipid vibrations were twisting and wagging (CH2) and CH stretching vibrations. Histologically distinguishable lesions showed specific combinations of band changes indicating alterations in the protein conformation and in the molecular structure of the lipids. Histogenetically related lesions (actinic keratosis and sqamous cell carcinoma) produced similar but not identical patterns of spectral changes. Because the examined skin lesions produced reproducible and unique spectra, we suggest that Raman spectroscopy will be useful for diagnosis of skin lesions.  相似文献   
40.
In this study, magnetic cores made of amorphous rectangular tape layers are investigated. The quality factor Q of the tape material decreases rapidly, however, when stacking at least two tape layers. The hysteresis loop becomes non-linear, and the coercivity increases. These effects are principally independent of the frequency and occur whether tape layers are insulated or not. The Kerr-microscopy was used to monitor local hysteresis loops by varying the distance of two tape layers. The magnetization direction of each magnetic domain is influenced by the anisotropy axis, the external magnetic field and the stray field of magnetic domains of the neighboring tape layers. We found that crossed easy axes (as the extreme case for inclined axes) of congruent domains retain the remagnetization and induce a plateau of the local loop. Summarizing local loops leads to the observed increase of coercivity and non-linearity of the inductively measured loop. A high Q-factor can be preserved if the easy axes of stacked tape layers are identical within the interaction range in the order of mm.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号