全文获取类型
收费全文 | 1118篇 |
免费 | 13篇 |
国内免费 | 6篇 |
专业分类
化学 | 874篇 |
晶体学 | 12篇 |
力学 | 9篇 |
数学 | 37篇 |
物理学 | 205篇 |
出版年
2022年 | 13篇 |
2021年 | 9篇 |
2020年 | 8篇 |
2019年 | 15篇 |
2018年 | 7篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 17篇 |
2013年 | 43篇 |
2012年 | 40篇 |
2011年 | 57篇 |
2010年 | 29篇 |
2009年 | 24篇 |
2008年 | 50篇 |
2007年 | 57篇 |
2006年 | 59篇 |
2005年 | 69篇 |
2004年 | 56篇 |
2003年 | 53篇 |
2002年 | 56篇 |
2001年 | 26篇 |
2000年 | 24篇 |
1999年 | 27篇 |
1998年 | 13篇 |
1997年 | 24篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 6篇 |
1993年 | 15篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 18篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1973年 | 16篇 |
1967年 | 4篇 |
排序方式: 共有1137条查询结果,搜索用时 0 毫秒
11.
Toshikatsu Koga Shinichi Morishita 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,34(2):71-74
An extensive optimization has been performed for the composition ofN terms, as well as the exponent and the mixing coefficients, of Kinoshita wave functions for heliumlike atoms with atomic numberZ. The optimalN-term Kinoshita functions have been constructed forN=1–10, 20, 30, 40, 50, 100 andZ=1(H–)–10(Ne8+). The present results demonstrate that the optimal term selection dramatically improves the accuracy of the Kinoshita function: In the case of He, for example, the optimal 100-term Kinoshita function gives – 2.903 724 376 95 hartrees, which is only 8×10–11 hartrees higher than the most accurate literature value. 相似文献
12.
13.
A thermosonimetric study has shown that the Phase II/III polymorphic transition of hexachloroethane emits acoustic signals. This solid-solid phase transition is known to occur by a nucleation-growth process during which a nucleus of the new phase, once formed, grows at the expense of the mother phase to form a complete crystal without fracture. Acoustic emissions from a conditioned multi-crystal sample have been used to study the transition. Acoustic activity correlated well with dilatometric measurements. Frequency analysis on waveforms of many hundreds of individual acoustic emissions revealed marked differences between individual signals. Principal-components analysis on 24 signal features revealed a single dispersed cluster with a highly non-uniform distribution of signals. These experiments provided highly reproducible average power spectra. Time-resolved acoustic power spectra were also generated. These additional types of information cannot be obtained by other techniques. 相似文献
14.
The relations between the Hellmann-Feynman forces in laboratory fixed (L-) and relative (R-) coordinate systems are clarified. In the usualL-coordinate system, the force is interpreted as force on nucleus, while in theR-coordinate system, it means force on whole particles consisting of the electrons and nuclei of each interacting subsystem. From a perturbation theoretical viewpoint, the concept of the force on whole particles correctly corresponds to the perturbation energy and is superior to the force on the nucleus. 相似文献
15.
Toshikatsu Koga 《International journal of quantum chemistry》1984,25(2):347-354
The recently proposed method of using momentum densities for interatomic interactions is applied to the long-range force between the ground-state hydrogen atom and the proton, and the results are compared with those from using the position density based on the electrostatic Hellmann–Feynaman theorem. A new physical interpretation of the long-range force is obtained, which is complementary to that in position space. It is found that some perturbative changes in the position density do not accompany changes in the momentum density. 相似文献
16.
Edgar Heilbronner Rolf Gleiter Toshihiko Hoshi Armin de Meijere 《Helvetica chimica acta》1973,56(5):1594-1604
To obtain further information concerning the interaction between Walsh-orbitols of ‘conjugated’ cyclopropane rings, the photoelectron spectra of the following compounds have been recorded: bicyclo[4.1.0]heptane 1 , cis- and trans-tricyclo[5.1.03, 5]octane 2, 3 , diademane 4 , trans-pentacyclo[3.3.2.02, 9.04, 10, 06, 8]decan 5 and bicyclo[4.1.0]heptene-2 6 . The first bands in the PE.-spectra of these compounds have been assigned on the basis of a ZDO HMO-approximation. For 2 and 4 the value for resonance integral between linked 2p atomic orbitals of two adjacent eclipsed cyclopropane rings is found to be ?1.73 eV. 相似文献
17.
F. Kokai Y. Koga Y. Kakudate M. Kawaguchi S. Fujiwara M. Kubota K. Fukuda 《Applied Physics A: Materials Science & Processing》1994,59(3):299-304
Laser-ionization Time-Of-Flight (TOF) mass-spectrometric studies have been carried out on the 532 nm and 1064 nm laser ablation products from a nitrogen-rich polymer. The polymer used had an elemental composition of C6.0N8.9H3.4 and consisted of C=N, C-N, and N-H chemical bonds. The TOF mass spectra observed were composed of various peaks (150 amu) depending on the ablation laser wavelength. The primary peaks were assigned to C+, CN+, CHnN+
2 (n=1–3) and C2H2N+
3 for 532 nm ablation, and C+, C+
3, HCN+, HCCN+, CH2NH+, HNCN+, H3NCN+, and C4H4N+
7 for 1064 nm ablation. The flight velocity distributions with peak velocities ranging from 8.6×103 cm/s to 3.8×104 cm/s were measured for these products. The distinct velocity distributions observed between small and large products indicate the presence of two origins in the fragment ejection process from the polymer for both 532 nm and 1064 nm ablation. Furthermore, we suggest an importance of the translational energy of the fragments for the product generation in the laser plume. 相似文献
18.
A novel approach to the mimicking of enzyme-catalyzed bond-forming reactions has been examined using multifunctionalized chiral crown ethers. In addition to the 18-crown-6 moiety as a binding site, the host have one thiol and one thio ester with an N-protected alpha-amino acid or a peptide, and have successfully achieved peptide synthesis in an enzyme-mimetic reaction mode. This new method involves the following three key reactions. (1) Intra-complex thiolysis: the host carries out the rapid intra-complex thiolysis of alpha-amino acid ester salts to form the dithioester, corresponding to the assembly of two guests by the host. (2) Amide formation: intramolecular aminolysis occurs between the bound guests to form the amide bond. (3) Peptide chain elongation: as the thiol reactive group is regenerated, the above two reactions are repeated to elongate the peptide chain. Formal turnover of the enzyme model has been demonstrated by the synthesis of a tetrapeptide derivative by the repetition of the above processes. 相似文献
19.
Hanai T 《Journal of chromatography. A》2004,1030(1-2):13-16
Retention mechanism on a graphitic carbon was analyzed by computational chemical calculation. The model graphitic carbon phase was a large polycyclic aromatic hydrocarbon (PAH) and analytes were carbohydrates and hydrocarbons separated by liquid and gas chromatography. Molecular mechanics calculation was fast and suggested their retention order and main retention force. Molecular orbital package calculation (MOPAC) demonstrated their complex form. 相似文献
20.
Koga T Taguchi K Kinoshita T Higuchi M 《Chemical communications (Cambridge, England)》2002,(3):242-243
A novel artificial protein with simple primary structure, poly(gamma-methyl-L-glutamate)-grafted polyallylamine, has been prepared and the resultant peptide has shown a unique property of pH-regulated conformation and morphology. 相似文献