全文获取类型
收费全文 | 1030篇 |
免费 | 13篇 |
国内免费 | 12篇 |
专业分类
化学 | 770篇 |
晶体学 | 15篇 |
力学 | 10篇 |
数学 | 72篇 |
物理学 | 188篇 |
出版年
2023年 | 4篇 |
2021年 | 4篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 14篇 |
2013年 | 78篇 |
2012年 | 34篇 |
2011年 | 46篇 |
2010年 | 26篇 |
2009年 | 31篇 |
2008年 | 52篇 |
2007年 | 60篇 |
2006年 | 55篇 |
2005年 | 53篇 |
2004年 | 43篇 |
2003年 | 52篇 |
2002年 | 55篇 |
2001年 | 17篇 |
2000年 | 22篇 |
1999年 | 7篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 5篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 17篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 5篇 |
1979年 | 21篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 11篇 |
1975年 | 16篇 |
1974年 | 11篇 |
1973年 | 9篇 |
1972年 | 4篇 |
排序方式: 共有1055条查询结果,搜索用时 31 毫秒
991.
Mitsutaka Natsume Yasuo Sekine Masashi Ogawa Hiroe Soyagimi Yoshinori Kitagawa 《Tetrahedron letters》1979,20(36):3473-3476
A novel type of a nucleophilic substitution on the piperidine ring was achieved by a stannous chloride-effected reaction of endoperoxides of N-alkoxycarbonyl-1,2-dihydropyridines with various kinds of carbon nucleophiles. 相似文献
992.
Yasuo Gotoh Yoshitaka Nagara Tamaki Nakano Yoshio Okamoto Yutaka Ohkoshi Masanobu Nagura 《Journal of Polymer Science.Polymer Physics》2004,42(5):800-808
The viscoelastic behavior and molecular motion of highly syndiotactic poly(vinyl alcohol) (S‐PVA) fibers with a dyad syndiotacticity (r) of 69% were studied by dynamic mechanical thermal analysis and wide‐angle X‐ray diffraction and compared with those of atactic poly(vinyl alcohol) (A‐PVA) fibers with r = 54%. The βc dispersion, based on the molecular motion of the chain molecules in the crystalline regions, was observed for A‐PVA around 120–140 °C, and the only primary (αc) dispersion was observed for S‐PVA around 180 °C. The thermal expansion coefficients for the a and c axes of the A‐PVA crystal changed discontinuously around 120 °C, which corresponded to the βc dispersion. For S‐PVA, the coefficient for the (002) plane changed discontinuously around 100 °C, similarly to A‐PVA, but that for the (100) plane remained unchanged between 20 and 220 °C. These results showed that the intermolecular hydrogen bonding of S‐PVA was stronger in the direction of the a axis than in the other directions, suppressing the βc dispersion. The storage modulus and thermal expansion coefficient of the (020) plane (molecular axis) of S‐PVA decreased markedly around 180 °C, and this indicated that the αc dispersion was due to the torsional motion of the molecular chains in the crystalline regions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 800–808, 2004 相似文献
993.
994.
Seiko Nan'Ya Hirofumi Ishida Ester J. Moiji Yasuo Butsugan Ashok C. Bajji 《Journal of heterocyclic chemistry》1994,31(2):401-403
2-Bromo-3-phenylinden-1-one 2 reacted with phenylthiourea to produce 2-phenylimino-8-phenylindeno[1,2-d]thiazole (heteropentalene) 4 in moderate yield and bis-substituted-indenyl sulfide 5 in low yield. Whereas, from the reaction of 2 with thiourea or its methyl derivative only 5 was obtained in moderate yield. Another brominated compound, dibromoacetylbenzophenone and several primary amines afforded iminoindanone derivatives 6 . 相似文献
995.
We have observed dispersive two-phonon Raman scattering of polaritons by LO and acoustic phonons near the lowest exciton state of ZnTe. From the Stokes shifts of these Raman lines, it has been found that the scattering process switches from an acoustic phonon followed by one LO phonon to the reversed one: a LO phonon followed by an acoustic one. 相似文献
996.
997.
Masahiro Ojima Yasuo Oka Takashi Kushida Shigeo Shionoya 《Solid State Communications》1977,24(12):845-848
Luminescence spectra of excitonic molecules in CuCl resonantly created by nano-second dye laser excitation are measured at 4.2 K changing the lenghts of the excited region. The spectra are dominated by stimulated emission. The gain coefficient for the MT line is saturated more easily than that for ML, though the former is larger under unsaturated conditions. These gain characteristics explain well various stimulated emission effects observed. 相似文献
998.
999.
Koichi Ito Yasuo Murase Yuya Yamashita 《Journal of polymer science. Part A, Polymer chemistry》1975,13(1):87-96
In the polymerization of diallyl phthalate in bulk at 60°C with azobisisobutyronitrile, extensive branching of the polymers obtained before gelation was ascertained from the enhanced broadening of the molecular weight distribution, coupled with the decrease of the residual unsaturation. Copolymerization of poly(diallyl phthalate) and styrene in bulk at 80°C with benzoyl peroxide was studied in detail with regard to the gel formation. The gel time increased with increasing fraction of styrene in feed. Both the gel yield and the conversion of styrene incorporated into the gel increased steadily with polymerization time, even after the total conversion of styrene exceeded 95%. The polystyrene recovered by saponification of the gel was found to carry hydroxyl groups, which should come from the copolymerized diallyl phthalate units. It was concluded that styrene behaved as a diluent in the early stage, and that the crosslinking after gelation of the system proceeded mainly through polymer–polymer reactions involving the occluded polystyryl radicals and poly(diallyl phthalate). 相似文献
1000.