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   569篇
  免费   27篇
  国内免费   6篇
化学   496篇
晶体学   4篇
力学   2篇
数学   18篇
物理学   82篇
  2023年   7篇
  2022年   7篇
  2021年   16篇
  2020年   28篇
  2019年   28篇
  2018年   7篇
  2017年   10篇
  2016年   19篇
  2015年   17篇
  2014年   19篇
  2013年   30篇
  2012年   46篇
  2011年   46篇
  2010年   17篇
  2009年   19篇
  2008年   49篇
  2007年   32篇
  2006年   26篇
  2005年   31篇
  2004年   22篇
  2003年   21篇
  2002年   23篇
  2001年   4篇
  2000年   6篇
  1998年   7篇
  1997年   5篇
  1996年   4篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   3篇
  1991年   4篇
  1990年   1篇
  1989年   2篇
  1987年   2篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   5篇
  1979年   3篇
  1978年   4篇
  1977年   3篇
  1976年   1篇
  1975年   5篇
  1972年   1篇
  1930年   2篇
  1927年   1篇
  1925年   2篇
排序方式: 共有602条查询结果,搜索用时 484 毫秒
41.
42.
43.
The electron transfer quenching of 2-aminopurine by guanine and 7-deazaguanine was investigated in B- and Z-DNA, and an increase in the fluorescence intensity of 2-aminopurine upon B- to Z-DNA transition was demonstrated.  相似文献   
44.
Ice crystallisation in crosslinked dextran (Sephadex) gels was studied by the method of two-dimensional X-ray diffraction (XRD) in combination with the simultaneous measurement of differential scanning calorimetry (DSC). With a Sephadex G25 gel where an exotherm due to ice crystallisation is observed in the DSC rewarming trace, it was indicated by the XRD pattern that small ice crystals less than approximately 10 microns in diameter are readily formed during freezing, and that the endothermic trend prior to the exotherm is not due to the glass transition but due to the melting of the small ice crystals. Moreover, the diffraction pattern observed with frozen Sephadex gels depended on the density of crosslink indicating that ice crystals of different size and dimension are formed in the gels.  相似文献   
45.
Oki Y  Nakazono S  Nonaka Y  Maeda M 《Optics letters》2000,25(14):1040-1042
A new nonlinear Raman spectroscopy technique for trace-gas detection was proposed and demonstrated. The technique involved the use of a thermal-lens detection scheme to monitor thermal emission from the stimulated Raman process. We termed this technique thermal-lens Raman spectroscopy, and it was combined with a novel scheme involving a nonlinear Raman spectroscopy without a tunable laser. This technique was applied to detecting trace hydrogen molecules in the atmosphere by use of a pulsed Nd:YAG laser and a continuous-wave He-Ne probe laser. A detection limit of 9 parts in 10(6) was attained.  相似文献   
46.
47.
Rapid separation of hydrophobic compounds such as bisindolylmaleimides, indolocarbazoles or fullerene C60 derivatives by ultra performance liquid chromatography was developed. Bisindolylmaleimides and indolocarbazoles were separated within 7 and 5 min, respectively. The linear ranges for the determination of bisindolylmaleimides and indolocarbazoles were 1.25?500 pmol and 0.5?50 pmol per injection (r > 0.99), respectively. Fullerene C60 derivatives were separated within 9 min, and the linear range for the determination of fullerene C60 derivatives was 0.1?10 pmol per injection (r > 0.99).  相似文献   
48.
In this paper, we consider the behavior of the total absolute and the total curvature under the Ricci flow on complete surfaces with bounded curvature. It is shown that they are monotone non-increasing and constant in time, respectively, if they exist and are finite at the initial time. As a related result, we prove that the asymptotic volume ratio is constant under the Ricci flow with non-negative Ricci curvature, at the end of the paper.   相似文献   
49.
Wittig reagents were successfully changed to symmetrical olefins when treated with elemental selenium. The reaction proceeds through a selenocarbonyl intermediate, which existence was confirmed by Diels-Alder reaction.  相似文献   
50.
The authors have demonstrated white light emission of rare earth (RE)-free Mn-doped SnO-ZnO-P(2)O(5) glass. The RE-free glass shows white light emission with a high value of quantum efficiency (QE) comparable to conventional crystalline phosphor. It is notable that the high QE value is attained for RE-free transparent glass, and the broad emission can be continuously tuned by both the amount of activator and the composition of the glass. Since this glass possesses low-melting property, we emphasize that the glass phosphor will lead to the development of a novel inorganic white-light-emitting device in combination with a solid state UV light-emitting source.  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