全文获取类型
收费全文 | 109篇 |
免费 | 1篇 |
专业分类
化学 | 40篇 |
物理学 | 70篇 |
出版年
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 1篇 |
排序方式: 共有110条查询结果,搜索用时 15 毫秒
101.
102.
The molecular rotational spectrum of 3-butynenitrile (3BN, propargyl cyanide), HCCCH2CN, has been investigated in the vibrational ground state. A total of 222 transitions up to J = 69 have been measured between 8 and 300 GHz. The Hamiltonian used for the spectral analysis was required to include all centrifugal terms of fourth and sixth orders and one term of eighth order in the angular momentum components in order to reproduce the transition frequencies within the experimental error. Significant values for the respective distortion coefficients could be determined. The molecular dipole moment components were calculated from measured Stark effect shifts as |μa| = (3.23 ± 0.05) D, |μb| = (2.34 ± 0.02) D; μtot = (3.99 ± 0.05) D. 相似文献
103.
B.P. Van Eijck A. Dubrulle J. Demaison J.L. Ripoll 《Journal of Molecular Spectroscopy》1985,112(1):95-103
In the rotational spectrum of methoxyethyne 173 new transitions (J ≤ 30) have been measured between 150 and 240 GHz. In the centimeter range 25 new transitions (J ≤ 11) of the first excited torsional state have also been assigned. An overall fit of the measurements using a structure relaxation model has allowed us to accurately determine the internal rotation parameters. For the A substate effective rotational parameters are given which allow the calculation of transition frequencies of possible astrophysical interest. 相似文献
104.
Ilyushin VV Alekseev EA Dyubko SF Podnos SV Kleiner Margulès L Wlodarczak G Demaison J Cosléou J Maté B Karyakin EN Golubiatnikov GY Fraser GT Suenram RD Hougen JT 《Journal of Molecular Spectroscopy》2001,205(2):286-303
A global fit of microwave and millimeter-wave rotational transitions in the ground and first excited torsional states (v(t) = 0 and 1) of acetic acid (CH(3)COOH) is reported, which combines older measurements from the literature with new measurements from Kharkov, Lille, and NIST. The fit uses a model developed initially for acetaldehyde and methanol-type internal rotor molecules. It requires 34 parameters to achieve a unitless weighted standard deviation of 0.84 for a total of 2518 data and includes A- and E-species transitions with J = 30 and K(a) = 15. While these results represent a significant improvement over past fitting attempts, it should be cautioned that the present data set is dominated by v(t) = 0 transitions, and no direct infrared measure of the v(t) = 1 <-- 0 torsional interval is available. Copyright 2001 Academic Press. 相似文献
105.
Bürger H Ma S Demaison J Le Guennec M Degli Esposti C Bizzocchi L 《Journal of Molecular Spectroscopy》2000,201(1):109-115
The vibrational excitations of bent triatomic molecules, including both bending and stretching vibrations, are studied in the framework of the U(4) algebra. For the bent triatomic molecules H(2)O and H(2)S, the highly excited vibrational levels (up to 14) are obtained using the U(4) algebraic approach. We have found that the spectra are made up of clustering structure. The number of levels in one cluster depends on the total quanta of stretching and bending. In addition, some other properties are also discussed. Copyright 2000 Academic Press. 相似文献
106.
Bürger H Ruland H Merke I Sarka K Margulès L Demaison J 《Journal of Molecular Spectroscopy》2000,203(2):268-272
The high-resolution infrared spectrum of the nu(8) band of SO(2)F(2) (nu(as) SF(2)) centered at 887.2 cm(-1) has been recorded with a resolution of 2.4 x 10(-3) cm(-1). More than 8000 transitions of the C-type band with DeltaK(a) = +/-1 (and in addition some DeltaK(a) = +/-3 transitions) have been assigned. Microwave and millimeter-wave spectra of the v(8) = 1 state up to 450 GHz have been recorded, and 177 pure rotational transitions have been measured. Rotational and rovibrational data have been combined, and excited state parameters up to sextic centrifugal distortion constants have been determined using a Watson-type Hamiltonian in S-reduction. No perturbation was indicated. Copyright 2000 Academic Press. 相似文献
107.
The equilibrium structure of acetylene (also named ethyne) has been reinvestigated to resolve the small discrepancies noted between different determinations. The size of the system as well as the large amount of available experimental data provides the quite unique opportunity to check the magnitude and relevance of various contributions to equilibrium structure as well as to verify the accuracy of experimental results. With respect to pure theoretical investigation, quantum-chemical calculations at the coupled-cluster level have been employed together with extrapolation to the basis set limit, consideration of higher excitations in the cluster operator, inclusion of core correlation effects as well as relativistic and diagonal Born-Oppenheimer corrections. In particular, it is found that the extrapolation to the complete basis set limit, the inclusion of higher excitations in the electronic-correlation treatment and the relativistic corrections are of the same order of magnitude. It also appears that a basis set as large as a core-valence quintuple-zeta set is required for accurately accounting for the inner-shell correlation contribution. From a pure experimental point of view, the equilibrium structure has been determined using very accurate rotational constants recently obtained by a "global analysis" (that is to say that all non-negligible interactions are explicitly included in the Hamiltonian matrix) of rovibrational spectra. Finally, a semi-experimental equilibrium structure (where the equilibrium rotational constants are obtained from the experimental ground state rotational constants and computed rovibrational corrections) has been obtained from the available experimental ground-state rotational constants for ten isotopic species corrected for computed vibrational corrections. Such a determination led to the revision of the ground-state rotational constants of two isotopologues, thus showing that structural determination is a good method to identify errors in experimental rotational constants. The three structures are found in a very good agreement, and our recommended values are r(CC) = 120.2958(7) pm and r(CH) = 106.164(1) pm. 相似文献
108.
The available experimental rotational constants of cis,trans-1,4-difluorobutadiene do not permit a determination of a complete structure. However, this problem, rather frequent in finding structures, may be solved by the mixed estimation method. The experimental ground state rotational constants are corrected for the rovibrational contribution calculated from an ab initio force field. These semiexperimental data are supplemented by structural parameters from ab initio calculations and a weighted least-squares fit allows us to obtain a reasonable structure. The accuracy of the fitted parameters is checked by optimizing a structure at the coupled cluster level. A good agreement is found between the two methods, validating our procedure. 相似文献
109.
Askeland E Møllendal H Uggerud E Guillemin JC Aviles Moreno JR Demaison J Huet TR 《The journal of physical chemistry. A》2006,110(46):12572-12584
Z-3-Amino-2-propenenitrile, H2NCH=CHCN, a compound of astrochemical and astrobiological interest, has been studied by Stark and Fourier transform microwave spectroscopy along with eight of its isotopologues; the synthesis of five of these are reported. The spectra of the ground vibrational state and of three vibrationally excited states belonging to the two lowest normal modes were assigned for the parent species, whereas the ground states were assigned for the isotopologues. The frequency of the lowest in-plane bending fundamental vibration was determined to be 152(20) cm(-1) and the frequency of the lowest out-of-plane fundamental mode was found to be 176(20) cm(-1) by relative intensity measurements. A delicate problem is whether this compound is planar or slightly nonplanar. It was found that the rotational constants of the nine species cannot be used to conclude definitely whether the molecule is planar or not. The experimental dipole moment is mu(a) = 16.45(12), mu(b) = 2.86(6), mu(c) = 0 (assumed), and mu(tot.) = 16.70(12) x 10(-30) C m [5.01(4) D]. The quadrupole coupling constants of the two nitrogen nuclei are chi(aa) = -1.4917(21) and chi(cc) = 1.5644(24) MHz for the nitrogen atom of the cyano group and chi(aa) = 1.7262(18) and chi(cc) = -4.0591(17) MHz for the nitrogen atom of the amino group. Extensive quantum-chemical calculations have been performed, and the results obtained from these calculations have been compared with the experimental values. The equilibrium structures of vinylamine, vinyl cyanide, and Z-3-amino-2-propenenitrile have been calculated. These calculations have established that the equilibrium structure of the title compound is definitely nonplanar. However, the MP2/VQZ energy difference between the planar and nonplanar forms is small, only -423 J/mol. Z-Amino-2-propenenitrile and E-3-amino-2-propenenitrile are formed simply by mixing ammonia and cyanoacetylene at room temperature. A plausible reaction path has been modeled. G3 calculations indicate that the enthalpy (298.15 K, 1 atm) of the transition state is about 130 kJ/mol higher than the sum of the enthalpies of the reactants ammonia and cyanoacetylene. This energy difference is comparatively high, which indicates that both E- and Z-3-aminopropenenitrile are not likely to be formed in the gas phase in cold interstellar clouds via a collision between ammonia and cyanoacetylene. An alternative reaction between protonated cyanoacetylene (H-C[triple bond]C-C[triple bond]NH+) and ammonia is predicted to have a much lower activation energy than the reaction between the neutral molecules. Although protonated E- and Z-3-aminopropenenitrile in principle may be formed this way, it is more likely that a collision between NH3 and H-C[triple bond]C-C[triple bond]NH+ leads to NH4+ and H-C[triple bond]C-C[triple bond]N. 相似文献
110.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献