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   147篇
  免费   4篇
化学   76篇
晶体学   4篇
物理学   71篇
  2020年   1篇
  2019年   4篇
  2018年   2篇
  2016年   4篇
  2015年   3篇
  2014年   2篇
  2013年   4篇
  2012年   3篇
  2011年   7篇
  2010年   5篇
  2009年   2篇
  2008年   4篇
  2007年   2篇
  2006年   4篇
  2005年   4篇
  2004年   3篇
  2003年   4篇
  2002年   5篇
  2001年   2篇
  2000年   3篇
  1999年   7篇
  1998年   2篇
  1997年   2篇
  1996年   7篇
  1995年   3篇
  1994年   5篇
  1993年   9篇
  1992年   1篇
  1991年   8篇
  1990年   2篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1985年   4篇
  1984年   2篇
  1983年   5篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
  1976年   3篇
  1975年   4篇
  1974年   1篇
  1972年   1篇
  1967年   3篇
排序方式: 共有151条查询结果,搜索用时 781 毫秒
11.
A quality assessment method for commercially available, optically active flavor compounds, namely, menthol, menthyl acetate, borneol, perillaldehyde, and 1,8-cineol, was developed. A gas chromatograph equipped with a flame ionization detector and a DB-5ms capillary column was used for the chemical purity test. A GC/MS with a beta-DEX cyclodextrin column was used for the optical purity test, by which the enantiomeric separation of each flavor compound was achieved. Enantiomeric excess was calculated as an expression of optical purity. Of the 25 standard samples subjected to the chemical purity test, six were found to have lower purity than the data provided by the manufacturers. When the same samples were subjected to the optical purity test, 11 were found to have lower purity than that indicated on the reagent labels. These results suggest that there is a need to conduct an optical purity test, in addition to a chemical purity test, for the quality assessment of flavor standards.  相似文献   
12.
In order to investigate the electronic structure around oxygen in superconducting La2–x Sr x CuO4 (x=0.10 and 0.14), precise measurements were carried out on the paramagnetic Knight shifts in the spin rotation frequency of the negative muon bound to the oxygen with reference to antiferromagnetic La2–x Sr x CuO4 (x=0.05). Remarkable temperature as well as crystalline-axis dependence was observed for the highT c case with a divergence character towardsT c. Possible mechanisms to explain the observed results are given.  相似文献   
13.
We compare the PCAC prediction based on the chiral anomaly for the π0 lifetime with a recent experiment. We find that the QED corrections are as large as 3%. After these corrections the experiment and the PCAC prediction disagree by 8.5 ± 2%. We estimate the corrections to the PCAC prediction. We find that reliably calculable corrections are not large enough to account for the discrepancy. However, contributions from the excited π0's may be able to explain the difference.  相似文献   
14.
In order to determine the copper content x of copper Chevrel compound CuxMo6S8?y(0?y?0.4) as a function of copper activity aCu and sulfur deficit y, a solid state electrochemical cell, Cu/Rb4Cu16I7Cl13/CuxMo6S8?y/Pt, was constructed and coulometric titration studies were made at 400 K. For the evaluation of the coulometric titration data, measurements were made on the electronic conductivity of copper-ion conductor Rb4Cu16I7Cl13. Also, a brief investigation was made on the condition of formation of single phase Chevrel CuxMo6S8?y with varying x and y at 1000°C. The structural change of CuxMo6S8?y with a change in x and y was studied by the X-ray diffraction method. It was found that x for constant aCu decreases with increasing y. The maximum value xmax of x in CuxMo6S8?y in equilibrium with metallic copper was found to be expressed by xmax=-(103)y+5. In the region of y<0.3, xmax exceeded 4, contrary to a presupposition that xmax is less than 4. X-ray analysis revealed that most of the copper Chevrel compounds denoted by CuxMo6S8 so far were sulfur deficient ones with y?0.4. The importance of sulfur deficit on the properties of the copper Chevrel compound was emphasized.  相似文献   
15.
16.
17.
18.
19.
20.
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