全文获取类型
收费全文 | 120篇 |
免费 | 10篇 |
国内免费 | 49篇 |
专业分类
化学 | 129篇 |
力学 | 8篇 |
综合类 | 2篇 |
数学 | 17篇 |
物理学 | 23篇 |
出版年
2022年 | 6篇 |
2021年 | 1篇 |
2020年 | 10篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 13篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有179条查询结果,搜索用时 78 毫秒
121.
122.
自70年代起,Handy[1]等,用变分法计算了H2、SO2等分子的振动-转动光谱,所得结果与实验吻合。但因在于计算久期行列式元素的积分,其计算方法不易推广。 相似文献
123.
自编了E-R[1]定域化计算程序,对HF、LiH、BH、Li2、Be2、CO和CH4等分子作了计算。确定的酉变换算出的定域分子轨道正确。计算了各分子的定域分子轨道能量ε、加和能E′和结合能E″[2],得到三点结论。 相似文献
124.
几种芳香胺类化合物E-12、E-13、E-14和E-15均为性能良好的有机电致发光(EL)和光致发光(PL)材料·采用量子化学计算方法,用RHF/AM1方法优化其构型,用RHF/CIS方法计算其电子光谱,计算结果与实验值基本吻合。 相似文献
125.
126.
Yueqin Li Ye Li Yueying Chu Xian Tao Huihua Xu Yingzhong Shen Anmin Zheng 《Journal of luminescence》2012,132(7):1663-1667
A new ternary samarium complex Sm(β-NBM)3·(PD) has been synthesized by the reaction of SmCl3·6H2O with β-naphthoylbenzoylmethane (β-HNBM) and 1,10-phenanthroline-5,6-dione (PD) in stoichiometry. The new samarium complex obtained was characterized by elemental analysis, 1H NMR, and FT-IR spectroscopy. The absorption and emission of this complex were systematically investigated. Photoluminescence studies indicated that the energy absorbed by the organic ligands was efficiently transferred to the central Sm3+ ions and the complex showed intensely and characteristically orange emission due to the 4G5/2→6Hj transitions of the central Sm3+ ions. The energy levels (HOMO and LUMO) of the ligands and the complex were further confirmed by computer simulation and cyclic voltammetry, respectively. All the results suggested that the synthesized Sm(β-NBM)3·(PD) would have the potential application for organic light-emitting diodes. 相似文献
127.
Tingfeng Wang Jin Guo Junfeng Shao Tao Sun Anmin Chen Hang Liu Dajun Ding 《Optics & Laser Technology》2012,44(5):1551-1555
The heating processes of a two-layer film assembly of Au padded with Cu irradiated by femtosecond laser pulse are studied using a two-temperature model. It is found that the chosen substantially influence the energy transport, and consequently the temperature variation, and thermal equilibrium time. At the same laser fluence, the different thickness of gold film leads to a change of gold surface temperature. By choosing the thickness of the gold layer in the two-layer film assemblies, the damage threshold of the gold film can be maximized. The results can be used to optimize the damage threshold of gold coating optical components. 相似文献
128.
He W Xue Y Zhang H Tian A Wong NB Wong NB 《The journal of physical chemistry. B》2006,110(3):1416-1422
Twelve tautomers of 2,4-dithiothymine are calculated at the MP2/6-31+G(d) level, and the most stable one is referred to the di-keto form (P12). Then four H-bonded complexes between P12 and water are optimized at the MP2/6-31+G(d) level of theory. The calculation of vibrational frequencies and natural bond orbital analysis are also carried out at the same level to investigate the hydrogen bonds involved in all the systems. Within all the four complexes, three types of hydrogen bonds are formed, in which the O-H...S and N-H...O bonds are the normal bonds with the X-H bond elongation and red shift of the corresponding stretch frequencies, while the C-H...O interaction is an improper, blue-shifting hydrogen bond accompanied with the contraction of the C-H bond and a blue shift of the C-H stretch frequency. The topological properties are investigated with the atoms-in-molecules (AIM) theory. The NMR chemical shielding for the isolated and the four monohydrated 2,4-dithiothymine are calculated using the "gauge-including atomic orbital" (GIAO) method. The 1H chemical shifts are influenced by the formation of hydrogen bonds. 相似文献
129.
The density function B3LYP method has been used to optimize the geometries of the luteolin, thymine and luteolin‐thymine complexes at 6‐31+G?? basis. The vibrational frequencies have been studied at the same level to analyze these seventeen complexes, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of the complexes corrected by basis set superposition error are between ?93.00–?76.69 kJ/mol. The calculating results indicate that strong hydrogen bonding interactions have been found in the luteolin‐thymine complexes. 相似文献
130.
A brief review is presented on acidity characterization of solid acid catalysts by means of solid-state phosphor-31 magic-angle-spinning nuclear magnetic resonance ((31)P MAS NMR) spectroscopy using phosphor-containing molecules as probes. It is emphasized that such a simple approach using (31)P MAS NMR of adsorbed phosphorous probe molecules, namely trimethylphosphine (TMP) and trialkylphosphine oxides (R(3)PO), represents a unique technique in providing detailed qualitative and quantitative features, viz. type, strength, distribution, and concentration of acid sites in solid acid catalysts. In particular, it will be shown that when applied with a proper choice of probe molecules with varied sizes and results obtained from elemental analysis, the amounts and locations (intracrystalline vs. extracrystalline) of different types (Br?nsted vs. Lewis) of acid sites may be determined. In addition, by incorporating the NMR results with that obtained from theoretical density functional theory (DFT) calculations, correlations between the (31)P chemical shifts (δ(31)P) and acidic strengths of Br?nsted and Lewis acid sites may also be derived, facilitating a suitable acidity scale for solid acid catalysts. 相似文献