全文获取类型
收费全文 | 3479篇 |
免费 | 765篇 |
国内免费 | 424篇 |
专业分类
化学 | 3057篇 |
晶体学 | 99篇 |
力学 | 2篇 |
综合类 | 7篇 |
物理学 | 1503篇 |
出版年
2024年 | 10篇 |
2023年 | 33篇 |
2022年 | 139篇 |
2021年 | 135篇 |
2020年 | 218篇 |
2019年 | 154篇 |
2018年 | 109篇 |
2017年 | 109篇 |
2016年 | 273篇 |
2015年 | 204篇 |
2014年 | 262篇 |
2013年 | 349篇 |
2012年 | 256篇 |
2011年 | 249篇 |
2010年 | 211篇 |
2009年 | 227篇 |
2008年 | 229篇 |
2007年 | 202篇 |
2006年 | 191篇 |
2005年 | 171篇 |
2004年 | 177篇 |
2003年 | 134篇 |
2002年 | 148篇 |
2001年 | 77篇 |
2000年 | 55篇 |
1999年 | 45篇 |
1998年 | 55篇 |
1997年 | 48篇 |
1996年 | 37篇 |
1995年 | 39篇 |
1994年 | 50篇 |
1993年 | 20篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有4668条查询结果,搜索用时 156 毫秒
41.
M. U. Belyi N. E. Bartnitskaya I. F. Mel'nik B. A. Okhrimenko S. M. Yablochkov 《Journal of Applied Spectroscopy》1995,62(3):564-567
T. Shevchenko Kiev University, 252022 Kiev, Pr. Akad. Glushakova, 6, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 62, No. 3, pp. 192–196, May–June, 1995. 相似文献
42.
通过改变紫外线的辐射照能量范围,研究了Eu^2+:BaFCl的光激励发光性质。发现紫外线能量大于Eu^2+的最低激发态能量及紫外线的能量小于Eu^2+最低激发态的能量两种情况下,光激励发光具有明显的差异,分析了产生差异的原因,给出了紫外线的辐照能量发生转时所对应的能级位置。 相似文献
43.
Solid-Phase Luminescence Determination of Ciprofloxacin and Norfloxacin in Biological Fluids 总被引:1,自引:0,他引:1
Svetlana Beltyukova Olga Teslyuk Alla Egorova Elena Tselik 《Journal of fluorescence》2002,12(2):269-272
A simple, rapid, and sensitive luminescence test method for the determination of ciprofloxacin (CIP) and norfloxacin (NOR) has been described. The method is based on the intramolecular energy transfer from organic acid to terbium (Tb3+) ion. Luminescence of terbium (III) complex with CIP (NOR), sorbed on the zeolite has been studied. Under optimized conditions the detection limit is 1 g/mL in urine and human plasma. 相似文献
44.
闪光灯反光罩结构设计的目标是使得所拍摄视场内的光能量分布尽量均衡。不同于基于几何光学理论的闪光灯计算和设计方法,采用了蒙特卡罗光子追迹法来分析闪光灯的结构设计。通过对照相机闪光灯几何结构的分析,引入余弦随机变量等方法,建立了闪光灯系统中光源、反光罩、菲涅耳透镜等部件的数学模型。先用蒙特卡罗光子追迹法模拟了单光子在闪光灯中飞行的各种可能状态,再通过产生大量光子仿真真实的情况。并对一个具体的闪光灯结构进行了计算,计算得到了光强和光子方向矢量在水平、垂直两个方向的投影角之间的分布曲线图。仿真结果符合设计要求并与实测曲线很接近,从而验证了蒙特卡罗光子追迹法在闪光灯结构设计中的可行性。 相似文献
45.
Yasuhiro Shiraishi Yugo Furubayashi Go Nishimura Takayuki Hirai 《Journal of luminescence》2007,127(2):623-632
Dinuclear lanthanide (Ln=Tb3+ or Eu3+) complexes (Ln2L2) of two octadentate macrocyclic polyaminopolycarboxylic ligands connected through a benzophenone (BP) moiety (L2) have been synthesized. Sensitized luminescence properties of Ln2L2 in water have been studied in comparison to those of BP-conjugated mononuclear Ln complexes (LnL1). The luminescence intensity of Tb2L2 is lower than that of TbL1 because of lower triplet quantum yield of the BP moiety. In contrast, Eu2L2 shows higher intensity than EuL1. For both Eu complexes, energy level of triplet excited-state BP (3BP*) is only 3 kJ mol−1 higher than that of 5D2 excited-state of Eu3+. The 5D2 state formed by a triplet-energy transfer (TET) from 3BP* is therefore deactivated by a back energy transfer (BET) to the ground-state BP, resulting in low luminescence intensity of EuL1. In contrast, within Eu2L2, TET from 3BP* to 5D0 state of two Eu3+ ions is accelerated, thus leading to higher luminescence intensity. Another notable feature of Eu2L2 is the luminescence quantum yield independent of its concentration. In contrast, for EuL1 system, an intermolecular BET occurs from 5D2 state of Eu3+ to the ground-state BP conjugated to another EuL1 complex, resulting in a yield decrease with the concentration increase. 相似文献
46.
采用燃烧法合成了La1.6(MoO4)3∶Eu3+0.4纳米晶末,研究了其声子-掺杂-晶格相互作用和发光性质。 X射线粉末衍射(XRD)分析表明,在500~900℃退火后,La1.6(MoO4)3∶Eu3+0.4样品为单一晶相。对样品进行了光致发光(PL)测量,激发Mo6+-O2-电荷迁移带,观察到Eu3+的系列发光,表明Mo6+-O2-带和Eu3+间存在能量传递,中心波长分别在λ1=469 nm和λ2=426 nm处的两个one-phonon边带,相应的声子能量分别为767和1202 cm-1,分别对应于Mo O和Mo—O—Mo伸缩振动。同时,计算了两个局域模电子-声子耦合强度的黄昆因子分别为S1=0.055和S2=0.037,为揭示其三价离子高传导特性及其负热膨胀物理特性提供了实验基础。 相似文献
47.
W. Chewpraditkul D. Chen B. Yu Q. Zhang Y. Shen M. Nikl R. Kucerkova A. Beitlerova C. Wanarak A. Phunpueok 《固体物理学:研究快报》2011,5(1):40-42
High silica glass doped with Eu2+ ions was prepared as a scintillating material by impregnation of Eu ions into a porous silica glass followed by reduction sintering in CO atmosphere. A dominant emission band of the Eu2+ 5d–4f transition peaking around 430 nm was observed in the luminescence spectrum with the excitation peak around 280 nm and no emission from Eu3+ was present. Photoluminescence decay kinetics was governed by decay times of a few microseconds. The Eu2+‐doped high silica glass exhibited comparable energy resolution and slightly higher photoelectron yield with respect to the Bi4Ge3O12 crystal in the pulse height spectra for X‐ray photon energies within 22–60 keV. Furthermore, a factor of 1.2 higher radioluminescence intensity was observed as well. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
48.
Li Li Wang XiaochunWei xiantao Chen YonghuGuo Changxin Yin Min 《Physica B: Condensed Matter》2011,406(3):609-613
Lutetium oxide nanopowders codoped with Tm3+ and Yb3+ were synthesized by the reverse-strike co-precipitation method. Effects of precipitant solution pH on the structural, morphological and upconversion luminescent properties of Lu2O3:2%Yb, 0.2%Tm nanopowders had been investigated. The results show that pH value of the precipitant (NH4HCO3) solution has a significant effect on the particle size, morphology and upconversion emission intensity of the Lu2O3:2%Yb, 0.2%Tm nanopowders. All the samples obtained from different pH value of precipitant solution can be readily indexed to pure cubic phase of Lu2O3, indicating good crystallinity. The upconversion emission intensity of Lu2O3:2%Yb, 0.2%Tm nanopowders obtained from the precipitant solution with pH=11 is the strongest. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing the number of OH− groups and the enlarged nanopowder size. The strong blue, weak red and near infrared emissions from the prepared nanopowders were observed under 980 nm laser excitation, and attributed to the 1G4→3H6, 1G4→3F4 and 3H4→3H6 transitions of Tm3+ ion, respectively. 相似文献
49.
50.