全文获取类型
收费全文 | 545篇 |
免费 | 20篇 |
国内免费 | 3篇 |
专业分类
化学 | 421篇 |
晶体学 | 4篇 |
力学 | 5篇 |
数学 | 27篇 |
物理学 | 111篇 |
出版年
2023年 | 4篇 |
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 13篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 13篇 |
2013年 | 24篇 |
2012年 | 30篇 |
2011年 | 30篇 |
2010年 | 16篇 |
2009年 | 16篇 |
2008年 | 35篇 |
2007年 | 23篇 |
2006年 | 40篇 |
2005年 | 25篇 |
2004年 | 34篇 |
2003年 | 30篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 14篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1988年 | 4篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 8篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1960年 | 2篇 |
1959年 | 1篇 |
1926年 | 1篇 |
1899年 | 1篇 |
排序方式: 共有568条查询结果,搜索用时 15 毫秒
1.
2.
An InGaAs/InAlAs five-layer asymmetric coupled quantum well (FACQW) is expected to show very large electrorefractive index change. n in a wideband transparency region. Band structures of the FACQW are analyzed with Luttinger-Kohn Hamiltonian. The electrorefractive characteristics of the FACQW are discussed. 相似文献
3.
1,3-Di-tert-butylazulene reacted with highly electrophilic trifluoromethanesulfonate of N-containing heterocycles to give 5-(dihydroheteroaryl)azulene derivatives in good yield and treatment of the 5-(dihydroheteroaryl)azulene derivatives with KOH afforded 5-(heteroaryl)azulenes in excellent yield. 相似文献
4.
Kentaro Suzuki Taro Toyota Katsuhiko Sato Masakazu Iwasaka Shoogo Ueno Tadashi Sugawara 《Chemical physics letters》2007,440(4-6):286-290
Collagen-containing tubular giant vesicles (Col–tGVs) under a high static magnetic field were found to constitute characteristic curved structures (e.g. circular, 8-figure, and hairpin-loop), which were sustained by polymerization of collagen units inside the tGV. We ascribed the formation of these structures to the elasticity of the tGV and to the competing diamagnetic anisotropies between collagen and the tGV. These curved structures can be well expressed by the equation of elastica. 相似文献
5.
The title racemate-to-conglomerate transformation which occurs in the solid state on heating or contact with MeOH vapour has been studied by IR and DTA spectral measurements, microscopic observation, and by X-ray structural and X-ray powder diffraction analysis. 相似文献
6.
Summary Pyridinium ylide complexes of methylcobaloxime were synthesized by the treatment of an ylide with Co(Hdmg)2 Me(SMe2). The crystal structure of one of the complexes, [Co(Hdmg)2Me C5H5NCHCOPh]C6H6 has been determined by x-ray diffraction techniques. The crystals are monoclinic, space group P21/c, witha = 10.456(5),b = 11.079(4),c = 24.58(1) Å, = 99.58(6), V = 2808 Å3, Z = 4. The Co-C (ylide) bond distance is 2.18 Å and Co-C(methyl) 2.04 Å. C(ylide)-Co-C(methyl) bond angle is 174.9°. The crystal, i.r. and1H n.m.r. data suggest that thetrans-influence of the ylide ligands is larger than that of py, Melm, OH2 or PPh3. 相似文献
7.
Shigendo?Enomoto Ken-ichi?Kumagai Taro?Tamura Miki?Hasegawa Kyoko?Nakada Toshihiko?Hoshi Michio?KobayashiEmail author 《Monatshefte für Chemie / Chemical Monthly》2004,135(5):471-481
Summary. Fluoranthene (FA) forms a 1:1 van der Waals complex with benzene in cyclohexane. The 1H NMR spectrum of this complex shows that the FA moiety in the complex state has five kinds of hydrogen atoms and that the 1H NMR peaks assigned to the protons attached to the naphthalene skeleton are largely shifted to higher magnetic field on complex formation with benzene. These observations indicate that the complex takes the structure of CS symmetry, in which the benzene molecule mainly interacts with the electronic system localized on the naphthalene moiety of FA. The present ab initio calculations reproduce well the 1H NMR spectral shifts mentioned above and the experimentally predicted CS structure of the complex. According to the PPP calculations for the electronic absorption spectral changes on the complex formation, the FA-benzene complex is considered to take a sandwich type structure. 相似文献
8.
9.
10.
Shinji Toyota Takashi Nakagawa Masashi Kotani Michinori
ki Hidehiro Uekusa Yuji Ohashi 《Tetrahedron》2002,58(52):10345-10351
All the three possible rotamers of the title compound were separated by chromatography, and unambiguously identified by NMR and X-ray analysis. One of the isomers was optically inactive Ci conformation. The other optical active forms were resolved to give a pair of enantiomers, which were characterized by optical rotation and CD spectra. Thus the optical inactivity of a compound such as meso-tartaric acid that can take Ci conformation in solution, is now ascribed to that the molecule has an optically inactive Ci conformer and equal amounts of optically active conformers, that are enantiomers, in solution. 相似文献