全文获取类型
收费全文 | 1820篇 |
免费 | 29篇 |
国内免费 | 313篇 |
专业分类
化学 | 1506篇 |
晶体学 | 9篇 |
数学 | 1篇 |
物理学 | 646篇 |
出版年
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 4篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 9篇 |
2016年 | 38篇 |
2015年 | 43篇 |
2014年 | 54篇 |
2013年 | 89篇 |
2012年 | 73篇 |
2011年 | 104篇 |
2010年 | 91篇 |
2009年 | 117篇 |
2008年 | 143篇 |
2007年 | 137篇 |
2006年 | 148篇 |
2005年 | 105篇 |
2004年 | 98篇 |
2003年 | 128篇 |
2002年 | 97篇 |
2001年 | 93篇 |
2000年 | 118篇 |
1999年 | 96篇 |
1998年 | 96篇 |
1997年 | 45篇 |
1996年 | 41篇 |
1995年 | 21篇 |
1994年 | 21篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 17篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有2162条查询结果,搜索用时 31 毫秒
961.
962.
Using the DFT-B3LYP calculations we investigate the adsorption of Li atom on CNT, BNNT, AlNNT and SiCNT. We found that Li atom can be chemisorbed on zig-zag SiCNT with binding energy of −2.358 eV and charge transfer of 0.842 |e|, which are larger than the results of other nanotubes. The binding energy of Li on SiCNT is foun to be stronger than activation energy barrier indicating that Li metal could be well dispersed on SiCNTs. Furthermore, the average voltage caused by the lithium adsorption on SiCNT demonstrated that SiCNTs could exhibit as a stable anode similar to the lithium metal anode. The binding nature has been rationalized by analyzing the electronic structures. Our findings demonstrate that Li-BNNT, Li-SiCNT and Li-AlNNT systems exhibit spin polarized behaviors and can fascinating potential application in future spintronics. Also, Li-SiCNT system with rather small band gap might be a promising material for optical applications and active molecule in its environment. 相似文献
963.
Guanping Li Dr. Olaf Stefanczyk Dr. Kunal Kumar Yuuki Mineo Dr. Koji Nakabayashi Prof. Dr. Shin-ichi Ohkoshi 《Angewandte Chemie (International ed. in English)》2023,62(7):e202214673
Self-assembly FeII complexes of phenazine (Phen), quinoxaline (Qxn), and 4,4′-trimethylenedipyridine (Tmp) with tetrahedral building blocks of [HgII(XCN)4]2− (X=S or Se) formed six new high-dimensional frameworks with the general formula of [Fe(L)m][Hg(XCN)4]⋅solvents (L=Phen, m/X=2/S, 1 ; L=Qxn, m/X=2/S, 2 ; L=Qxn, m/X=1/S, 3 ; L=Qxn, m/X=1/Se, 3-Se ; L=Tmp, m/X=1/S, 4 ; and L=Tmp, m/X=1/Se, 4-Se ). 1 , 3 , and 3-Se show an intense sub-terahertz (sub-THz) absorbance of around 0.60 THz due to vibrations of the solvent molecules coordinated to the FeII ions and crystallization organic molecules. In addition, crystals of 1 , 4 , and 4-Se display low-frequency Raman scattering with exceptionally low values of 0.44, 0.51, and 0.53 THz, respectively. These results indicate that heavy metal FeII−HgII systems are promising platforms to construct sub-THz absorbers. 相似文献
964.
Ramalingam M Sundaraganesan N Saleem H Swaminathan J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(1):23-30
The FTIR and FT-Raman spectra of 5-amino-2-nitrobenzoic acid (ANB) have been recorded in the region 400-4000cm(-1). The observed frequencies were assigned to different modes of vibrations on the basis of fundamental, combination and overtones. The geometry has been optimized with complete relaxation on the potential energy surface at HF, MP2 and B3LYP level of theories using 6-311++G(d,p) basis set and compared with the crystal data. The possible hydrogen bond interaction has been estimated taking a model compound. Further harmonic vibrational frequency calculations have been carried out at HF and B3LYP levels and the scaled values were in good agreement with majority of the experimental observations. The theoretically constructed spectra coincide satisfactorily with those of experimental spectra. 相似文献
965.
Subramanian MK Anbarasan PM Ilangovan V Babu SM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(1):59-67
The gas phase infrared spectrum of 3-aminoacetophenone (3AAP) was measured in the range 5000-500cm(-1) and with a resolution of 0.5cm(-1). The Fourier transform Raman (FT-Raman) and Fourier transform infrared (FT-IR) spectra of 3AAP were recorded in the solid phase. Geometry optimizations were done without any constraint and several thermodynamic parameters were calculated for the minimum energy conformer at ab initio and density functional theory (DFT) levels invoking 6-311G(2df 2p) basis set and the results are compared with the experimental values. Harmonic-vibrational wavenumber was also calculated for the minimum energy conformer at ab initio and DFT levels using 6-31G(d,p) basis set and the results are compared with related molecules. With the help of specific scaling procedures, the observed vibrational wavenumbers in gas phase, FT-IR and FT-Raman spectra were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range, the error obtained was in general very low. The appropriate theoretical spectrogram for the FT-IR spectra of the title molecule is also constructed. 相似文献
966.
Hafid Anane Soufiane El Houssame Abdelali El Guerraze Abdeladim Guermoune Abderrahim Boutalib Abedellah Jarid Ignacio Nebot-Gil Francisco Tomás 《Central European Journal of Chemistry》2008,6(3):400-403
The complexation energies of H3BNHnCl3−n (n= 3-0) complexes and the proton affinities of NHnCl3−n compounds have been computed at the G2(MP2) level of theory. G2(MP2) results show that the successive chlorine substitution
on the ammonia decreases both the basicity of the NHnCl3−n ligands and the stability of H3BNHnCl3−n complexes. The findings are interpreted in terms of the rehybridisation of the nitrogen lone-pair orbital. The NBO partitioning
scheme shows that the variation of the N-H and N-Cl bond lengths, upon complexation, is due to variation of “s” character
in these bonds.
相似文献
967.
968.
Raman and FTIR spectra for 2,3,4- and 2,3,6-tri-fluoro-benzonitriles have been recorded in the regions 50–4000 cm−1 and 400–4000 cm−1, respectively. Measurement of depolarization ratios for the Raman lines has also been made. Optimized geometrical parameters, charge distributions and vibrational wavenumbers were calculated using ab initio quantum chemical method. Normal coordinate analysis has also been carried out to help assign the fundamentals of these molecules. Each vibration has been assigned using observed wavenumbers in the IR and Raman spectra and their relative intensities, depolarization ratios of the Raman lines, the calculated frequencies, vector displacements and potential energy distributions (PEDs). 相似文献
969.
970.