全文获取类型
收费全文 | 560篇 |
免费 | 92篇 |
国内免费 | 51篇 |
专业分类
化学 | 369篇 |
晶体学 | 5篇 |
力学 | 1篇 |
综合类 | 4篇 |
数学 | 23篇 |
物理学 | 301篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 21篇 |
2021年 | 23篇 |
2020年 | 44篇 |
2019年 | 26篇 |
2018年 | 12篇 |
2017年 | 14篇 |
2016年 | 24篇 |
2015年 | 24篇 |
2014年 | 26篇 |
2013年 | 60篇 |
2012年 | 25篇 |
2011年 | 20篇 |
2010年 | 25篇 |
2009年 | 29篇 |
2008年 | 30篇 |
2007年 | 35篇 |
2006年 | 35篇 |
2005年 | 25篇 |
2004年 | 26篇 |
2003年 | 19篇 |
2002年 | 15篇 |
2001年 | 25篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1980年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有703条查询结果,搜索用时 62 毫秒
81.
于昂扬 《原子与分子物理学报》2013,30(6)
研究了气相甲醇分子(CH3OH)基态和激发态性质。在对不同方法基组所得计算结果和实验结果进行比较之后,选用MP2(full)/6-311++G(2d,2p)理论方法进行计算,得到甲醇分子(CH3OH)基态和三重激发态的几何结构、能量以及频率信息;频率计算显示基态和三重态都为稳定构型。从三重态的结构出发,解释了三重态势能面为排斥型势能面的合理性。计算了甲醇分子单重激发态的垂直激发能,比较不同方法不同基组计算的甲醇分子单重激发态的垂直激发能,发现用TDDFT 中的b3p86方法使用6-311++G**基组的计算值和实验值符合得最好。计算得到的甲醇分子在MP2(full)/6-311++G(2d,2p)的绝热电离能和垂直电离能分别为11.18eV和11.32eV;计算得到的绝热电子亲和势与垂直电子亲和势分别为0.888eV和0.893eV。计算结果对实验研究有指导意义。 相似文献
82.
Oleg L. Berman Yurii E. Lozovik David W. Snoke Rob D. Coalson 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):268
The theory of what happens to a superfluid in a random field, known as the “dirty boson” problem, directly relates to a real experimental system presently under study by several groups, namely excitons in coupled semiconductor quantum wells. We consider the case of bosons in two dimensions in a random field, when the random field can be large compared to the repulsive exciton–exciton interaction energy, but is small compared to the exciton binding energy. The interaction between excitons is taken into account in the ladder approximation. The coherent potential approximation (CPA) allows us to derive the exciton Green's function for a wide range of the random field strength, and in the weak-scattering limit CPA results in the second-order Born approximation. For quasi-two-dimensional excitonic systems, the density of the superfluid component and the Kosterlitz–Thouless temperature of the superfluid phase transition are obtained, and are found to decrease as the random field increases. 相似文献
83.
Gustavo A. Narvaez Lixin He Gabriel Bester Alex Zunger 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):93
We show how an atomistic pseudopotential plus many-body configuration interaction theory can address the main spectroscopic features of self-assembled dots including, excitons, trions, biexcitons, fine-structure, charging spectra as well as electric-field dependence of entanglement in dot molecules. 相似文献
84.
Maruthi Janaki Ram Reddy V. Venkat Reddy U. Srinivas M. Janaki Ram Reddy V. Jayathirtha Rao 《Journal of Chemical Sciences》2002,114(6):603-609
Naphthyldiene derivatives,1-4, carrying electron-donating groups at one end and electron-withdrawing groups at the other, were synthesized to study the
photoisomerization process. All the compounds showed efficient photoisomerization upon direct excitation leading to the formation
of 4-Z isomer with high selectivity. Triplet sensitization studies indicated inefficientE-Z isomerization process. Room temperature fluorescence of1 and2 displayed fine structure in hexane solvent and the same was replaced by broad or structureless fluorescence in acetonitrile
and methanol solvents. A mechanism involving a polarized or charge transfer singlet excited state is proposed for the observed
photoisomerization in these naphthyldiene derivatives. 相似文献
85.
86.
理论上研究了基于Hanbury Brown Twiss 探测方式,利用单光子和双光子统计概率P RS(1),PRS(2),直接测量单分子光子源的信号背景比.在研究过程中同时考 虑到单分子布居于暂稳态和探测器量子效率对测量结果的影响.在满足PRS(1)2 PRS(2)-3PRS(2)的条件时,研究给出了一种有效测量信号背景比的方 法SBR=P2RS(1)/2PRS(2).另外,分析讨论了Mandel参数Q 与信号背景比之间的关系.
关键词:
单分子光子源
信号背景比
光子统计
暂稳态
Mandel参数 相似文献
87.
A. P. Losev S. M. Bachilo D. I. Volkovich Yu. S. Avlasevich K. N. Solov’yov 《Journal of Applied Spectroscopy》1997,64(1):62-71
Photoinduced electron transfer (PET) in a Pd-porphyrin-quinone complex (Pd-P-Q) was investigated using the flash photolysis
method in microsecond and picosecond range and by luminescence. The investigations were performed for toluene solutions. Intramolecular
PETs in the lower excited singlet state (kCT=1.7·1010 sec−1) and in the triplet state (kCT=2.5·108sec−1) were observed. For a quantum yield of the triplet state that is close to 1 in Pd-porphyrin (Pd-P) this yield is equal to
0.4 in Pd-P-Q. This decrease is the result of PET in the excited state and, possibly, in an unrelaxed triplet state. Triplet
Pd-P-Q molecules were efficiently quenched by unexcited molecules, and this process is related to intermolecular charge transfer.
This electron transfer is likely to occur from the Pd-P protion of an excited molecule to the quinone protion of an unexcited
molecule in the collisional complex (Pd-P-Q)2. Charged radicals, formed once the collisional complex is transferred and separated, have a wide absorption band with a maximum
of about 960 nm. The average lifetime of the radicals was about 2 msec.
Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No 1 pp. 61–70, January–February, 1997. 相似文献
88.
89.
S. L. Bondarev 《Journal of Applied Spectroscopy》1997,64(1):1-15
A review of data on the photophysics of carotenoids is presented. Results of investigations of spectroscopic, temporal, and
energy parameters of excited S1 and S2 singlet states of β-carotene and related compounds are critically examined. These states give rise to extremely high probabilities
(1011–1013 sec−1) of radiationless deactivation of the electronic excitation energy in carotenoids. Results of investigations of photophysical
properties of triplet states of carotenoids are considered mainly from the standpoint of quenching of singlet oxygen and triplet
states of organic molecules by carotenoids.
Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 5–19, January–February, 1997. 相似文献
90.
L. V. Levshin G. A. Ketsle G. V. Mel’nikov Yu. D. Lantukh 《Journal of Applied Spectroscopy》1997,64(5):639-641
Investigation of deactivation processes in triplet states of a series of aromatic hydrocarbon molecules (antracene, 1,2-benzantracene,
and 3,4-benzpyrene) made it possible to reveal the presence of triplet-triplet annihilation of the molecules in aqueous micellar
solutions of sodium dodecyl sulfate. It is shown that the effect of microheterogeneous solutions on the process of triplet-triplet
annihilation manifests itself in an increase in the probability of excimerization upon dissociation of triplet pairs of 1,2-benzantracene
and 3,4-benpyrene molecules compared to one-component solutions.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 626–628, September–October, 1997. 相似文献