全文获取类型
收费全文 | 780篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
化学 | 596篇 |
晶体学 | 15篇 |
力学 | 8篇 |
数学 | 18篇 |
物理学 | 161篇 |
出版年
2021年 | 3篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 20篇 |
2012年 | 34篇 |
2011年 | 44篇 |
2010年 | 26篇 |
2009年 | 24篇 |
2008年 | 51篇 |
2007年 | 77篇 |
2006年 | 39篇 |
2005年 | 41篇 |
2004年 | 42篇 |
2003年 | 40篇 |
2002年 | 30篇 |
2001年 | 36篇 |
2000年 | 29篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1966年 | 3篇 |
1965年 | 4篇 |
排序方式: 共有798条查询结果,搜索用时 31 毫秒
741.
Taro Tsubomura Shigenobu Yano Sadao Yoshikawa Koshiro Toriumi Tasuku Ito 《Polyhedron》1983,2(2):123-124
742.
Hisayoshi Itoh Akira Uedono Takeshi Ohshima Yasushi Aoki Masahito Yoshikawa Isamu Nashiyama Shoichiro Tanigawa Hajime Okumura Sadafumi Yoshida 《Applied Physics A: Materials Science & Processing》1997,65(3):315-323
2
+ and Al+ at temperatures from room temperature (RT) to 1200 °C at doses of 1013 and 1015/cm2. It is found from Doppler broadening spectra of annihilation gamma-rays obtained by varying the incident positron energy
that hot-implantation gives rise to clustering of vacancies, whereas it suppresses amorphization and diminishes the thickness
of damaged layers. The average size of such clusters increases with increasing implantation dose and temperature. Vacancy
clustering by hot-implantation can be interpreted by the combination of vacancies during implantation. Vacancy type defects
in the low-dose (1013/cm2) implanted samples are found to be removed by annealing at 1400 °C, whereas large vacancy clusters still remain after 1400 °C
annealing in the high-dose (1
015/cm2) implanted samples. It is also derived from the depth profile of positron diffusion length that positron scattering centers
are produced after annealing at 1400 °C in all implanted samples.
Received: 7 March 1997/Accepted: 6 May 1997 相似文献
743.
S. Kawasaki S. Yoshikawa T. Imasaka N. Ishibashi 《Applied physics. B, Lasers and optics》1993,56(5):259-262
A laser beam at two different frequencies separated by 587 cm–1 is focused into pressurized hydrogen (rotational transition energy, 587 cm–1) to generate multi-color stimulated Raman emission. The polarization state and the pulse energy are measured for each generated emission line using linearly and circularly polarized pump beams. The effect of the polarization is discussed by using a parameter characterizing the polarizability of hydrogen and a conservation rule for the angular momentum in four-wave mixing. Many rotational lines are generated with linearly polarized pump beams through a four-wave mixing process. This is in striking contrast to the results obtained by using a single-color circularly polarized pump beam which generates only one rotational line through a conventional stimulated Raman process. 相似文献
744.
745.
Masanori Yoshikawa Michio Sorai Hiroshi Suga 《Journal of Physics and Chemistry of Solids》1984,45(7):753-760
The heat capacity of the title complex, Fe[S2CN(CH3)2]2Cl, has been measured between 0.4 and 300 K. A λ -type phase transition with a small shoulder arising from magnetic ordering was found at (0.609 ± 0.005) K. The character of the ordered phase has been suggested to be ferromagnetic on the basis of comparison between the methyl- and ethyl-homologues. The magnetic hyperfine structure of the Mössbauer spectra and the line broadening due to electronic relaxation effects at 1.2 K hitherto reported are concluded to result from a critical slowing-down when the magnetic transition temperature is approached from the high-temperature side. A Schottky-type anomaly arising from the zero-field splitting of a single ferric ion was observed around 2 K. The excess entropy beyond the lattice contribution at low temperatures amounts to (14.05 ±0.27) J K?1mol?1, which cannot be accounted for solely by the magnetic entropy of Rln 4 (= 11.53 JK?1mol?1) for the intermediate spin of . Two possibilities concerning additional conntribution have been discussed; one is a mixing of spin species of and the other is a tunnel-splitting of the rotational levels of four methyl-constituents. The present study cannot give a definite conclusion as to the existence of dimeric units suggested from Mössbauer spectroscopy. 相似文献
746.
747.
Michio Sorai Masanori Yoshikawa Naoto Arai Hiroshi Suga Syûzô Seki 《Journal of Physics and Chemistry of Solids》1978,39(4):413-425
The heat capacity of the tetranuclear nickel cluster complex, tetrakis [μ3-methoxo-2,4-pentanedionato (methanol) nickel (2)], has been measured from 0.4 to 285 K. Contrary to the previous prediction by Bertrand et al.[6], that this complex exhibits an intercluster ferromagnetic spin coupling, the present heat capacity measurement shows no indication of the spin-ordering effect caused by the intercluster interaction at least down to 0.4 K. Instead, a heat capacity anomaly centered around 1.5 K with a shoulder at 0.5 K has been observed. This anomaly is well accounted for in terms of both a level splitting of the ground S = 4 state due to a uni-axial crystalline anisotropy and a tunnel-splitting of the rotational levels of methyl groups. The intracluster spin exchange constant J and the single-ion zero-field splitting parameter D are determined to be and (h being the Planck constant and c the speed of light in a vacuum). The temperature dependence of the effective Bohr magneton [6] is also satisfactorily accounted for on the basis of this model. The tunnel-splitting δ of the lowest rotational level of the four methyl groups belonging to methoxides is estimated to be and the corresponding potential barrier Vo is found to be Vo = 1.9–1.5 kJmol?1. 相似文献
748.
Sakaia T Sugano N Tsuji T Nishii T Yoshikawa H Ohzono K 《Magnetic resonance imaging》2000,18(7):897-905
We investigated the time-dependent natural course of experimental osteonecrosis (ON), including initial changes in ON and the reparative process, using in vivo serial repetitive magnetic resonance imaging (MRI) in a non-traumatic rabbit serum sickness ON model. Some necrotic lesions were detected at 1 week (3 of 16 femora with necrotic lesions) and some in the metaphysis were detected by 12 weeks (2 of 6 femora with lesions) on T(1)-weighted, T(2)-weighted, and fat suppression T(1)-weighted images. On contrast-enhanced MRI, extravasation of the erythrocytes was detected at 72 h (7 of 26 femora with lesions) as a small, focal enhanced area. Necrotic lesions were detected in all abnormal femora by 6 weeks (16 of 16 femora with lesions) as focal, homogeneously or inhomogeneously enhanced areas. Reparative tissue replaced with new vascular and trabecular formation in necrotic areas was detected as an extended marginal enhanced area at 12 weeks. These results suggest that the enhancement patterns on contrast-enhanced MRI may provide helpful information about the developmental and reparative process of clinical ON. 相似文献
749.
K. Yatsu T. Cho M. Ichimura K. Ishii A. Itakura Y. Ishimoto I. Katanuma T. Kato J. Kohagura Y. Nakashima T. Natori K. Orito T. Saito Y. Tatematsu M. Yoshikawa 《Czechoslovak Journal of Physics》2001,51(10):977-982
Potential confinement was demonstrated experimentally under various electron cyclotron resonance heating (ECRH) scenarios. The particle confinement time and the plasma confining potential increased with ECRH power. The plug potential formation by means of only ce ECRH was studied by Monte-Carlo simulation. Potential confinement experiments have advanced in higher density region up to 4×1012 cm-3. The higher density plasma was obtained by high frequency ICRF heating and recently installed neutral beam injector in the central cell. Studies of scaling relation of the potential confinement with respect to the plasma density have started with the high density plasma. 相似文献
750.
We have investigated the dynamical behaviour of the rhythmic conformational change between the folded compact state and the unfolded state in a single polymer chain under thermodynamically open conditions. It is shown that the spontaneous rhythmic change in the conformation of a single polymer chain (T4DNA, 166 kbp, contour length: 56 microns) is generated using a focused continuous wave (CW) Nd:YAG laser beam (wavelength lambda = 1064 nm), where the focused laser beam plays a dual role, both trapping a polymer chain at the focus and creating a temperature gradient around the focus. Furthermore, the whole process of the rhythmic conformational change: the course of melting, nucleation and growth between the folded and unfolded states has been clarified. The rhythmic change in the conformation is discussed in terms of the limit-cycle oscillation driven by the dissipation of the photon energy. 相似文献