全文获取类型
收费全文 | 303篇 |
免费 | 6篇 |
专业分类
化学 | 257篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 4篇 |
物理学 | 41篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 12篇 |
2012年 | 14篇 |
2011年 | 22篇 |
2010年 | 8篇 |
2009年 | 13篇 |
2008年 | 16篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1974年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有309条查询结果,搜索用时 31 毫秒
51.
Natsuki Hashitsumae Fumiaki Shibata Mayumi Shing¯u 《Journal of statistical physics》1977,17(4):155-169
A new memoryless expression for the equation of motion for the reduced density matrix is derived. It is equivalent to that proposed by Tokuyama and Mori, but has a more convenient form for the application of the perturbational expansion method. The master equation derived from this form of equation in the first Born approximation is applied to two examples, the Brownian motion of a quantal oscillator and that of a spin. In both examples the master equation is rewritten into the coherent-state representation. A comparison is made with the stochastic theory of the spectral line shape given by Kubo, and it is shown that this theory of the line shape can be incorporated into the framework of the present theory. 相似文献
52.
53.
54.
Taishi Taken Obu Hideo Shimoda Yoshihiro Iwasa Tadaoki Mitani Mayumi Kosaka Kats Umi Tanigaki 《Molecular Crystals and Liquid Crystals》2013,570(1):599-604
Abstract Correlations among lattice parameter, external pressure, and critical temperature Tc has been surveyed on fullerene superconductors with a wide range of lattice parameters and various valence states. The observed value of dTc/dP for Na2Rb0.5Cs0.5C60 and Li3CsC60, having small interfullerene separations, is about a few times lager than that of K3C60. In contrast, small dTc/dP values are found in fullerides with expanded unit cells, such as (NH3)xNaAA?C60 (A, A? = K, Rb and Cs) and A3Ba3C60. Interestingly, the chemical and physical pressure effects on Tc are considerably different in these fullerides with large interfullerene spacings. Our results suggest that the pressure dependence is scaled by an interfullerene distance when the interfullerene distances is small, but that this scaling fails when the unit cell is expanded. 相似文献
55.
Stereoselective synthesis of triply isotope-labeled Ser, Cys, and Ala: amino acids for stereoarray isotope labeling technology 总被引:1,自引:0,他引:1
Efficient access to highly enantioselective isotope-labeled serine, cysteine, and alanine for stereoarray isotope labeling (SAIL) is described. 相似文献
56.
Iijima M Yoshimura M Tsuchiya T Tsukada M Ichikawa H Fukumori Y Kamiya H 《Langmuir : the ACS journal of surfaces and colloids》2008,24(8):3987-3992
A novel thermo- and pH-sensitive nanogel particle, which is a core-shell structured particle with a poly(N-isopropylacrylamide) (p(NIPAAm)) hydrogel core and a poly(ethylene glycol) monomethacrylate grafted poly(methacrylic acid) (p(MMA-g-EG)) shell, is of interest as a vehicle for the controlled release of peptide drugs. The interactions between such nanogel particles and artificial mucin layers during both approach and separation were successfully measured by using colloid probe atomic force microscopy (AFM) under various compression forces, scan velocities, and pH values. While the magnitudes of the compression forces and scan velocities did not affect the interactions during the approach process, the adhesive force during the separation process increased with these parameters. The pH values significantly influenced the interactions between the nanogel particles and a mucin layer. A large steric repulsive force and a long-range adhesive force were measured at neutral pH due to the swollen p(MMA-g-EG) shell. On the other hand, at low pH values, the steric repulsive force disappeared and a short-range adhesive force was detected, which resulted from the collapse of the shell layer. The nanogel particles possessed a pH response that was sufficient to protect the incorporated peptide drug under the harsh acidic conditions in the stomach and to effectively adhere to the mucin layer of the small intestine, where the pH is neutral. The relationships among the nanogel particle-mucin layer interactions, pH conditions, scan velocities, and compression forces were systemically investigated and discussed. 相似文献
57.
Otsuki J Imai A Sato K Li DM Hosoda M Owa M Akasaka T Yoshikawa I Araki K Suenobu T Fukuzumi S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(9):2709-2718
A star-shaped Ru/Os tetranuclear complex, in which a central Os unit is linked to three peripheral Ru units by 4,4'-azobis(2,2'-bipyridine) (azobpy) bridging ligands, was prepared to examine the unique photodynamics regulated by its redox state. The Ru/Os tetranuclear complex exhibits Ru-based luminescence at 77 K, whereas the three-electron reduction (one for each azobpy) of the Ru/Os complex results in luminescence from the Os unit. The photoexcited state of the Ru/Os complex rapidly decays into low energy metal-to-ligand charge-transfer states, in which the excited electron is localized in the azobpy ligand in the form of azobpy(.-). Upon the one-electron reduction of the azobpy ligands, the above-mentioned low-energy states become unavailable to the photoexcited complex. As a result, an energy transfer from the Ru-based excited state to the Os-based excited state becomes possible. Ultrafast transient absorption measurements revealed that the energy transfer process consists of two steps; intramolecular electron transfer from the terminal bipyridine ligand (bpy(.-)) to form azobpy(2-) followed by a metal-to-metal electron transfer. Thus, the Ru/Os tetranuclear complex collects light energy into the central Os unit depending on the redox state of the bridging ligands, qualifying as a switchable antenna. 相似文献
58.
Iwaura R Kikkawa Y Ohnishi-Kameyama M Shimizu T 《Organic & biomolecular chemistry》2007,5(21):3450-3455
Templated self-assembly of nucleotide bolaamphiphile 1 (in which a 3'-phosphorylated thymidine moiety is connected to each end of a long oligomethylene chain) with a 10-, 20-, 30-, or 40-meric single-stranded oligoadenylic acid (2, 3, 4, or 5) led to the formation of right-handed helical nanofibers in 0.1x Tris/EDTA (TE) buffer solutions. The helical pitch increased as the length of the oligoadenylic acid template increased. DNA composed of oligoadenylic and oligocytidylic acid sequences (6, 7, and 8) also acted as templates to induce the formation of helical nanofiber structures. The diameter of the nanofibers remained constant (6-6.6 nm) irrespective of the template used. The binary self-assembly of 1 with 4 also produced higher-order, double-stranded nanofibers. 相似文献
59.
To examine the nature of the lower closure point of adsorption hysteresis in ordered mesoporous silicas, we measured the temperature dependence of the adsorption-desorption isotherm of nitrogen for three kinds of ordered silicas with cagelike pores and three kinds of ordered silicas with cylindrical pores. The lower closure point pressure of nitrogen in the cagelike pores with sufficiently small necks, that is, the cavitation pressure of a confined liquid, did not depend appreciably on the cage size in the temperature region far away from a hysteresis critical temperature (Tch) but its cage-size dependence was noticeable in the vicinity of Tch. The lower closure point in the cylindrical pores depended on the pore size, and its thermal behavior was totally different from that in the cagelike pores. Nevertheless, the hysteresis critical points of nitrogen in the ordered mesoporous silicas, which are defined as a threshold of temperatures (Tch) and pressure above which reversible capillary condensation takes place in a given size and shape of pores, fell on a common line in a temperature-pressure diagram regardless of the pore geometries. We consider this finding as evidence that capillary evaporation in the cylindrical pores follows a cavitation process in the vicinity of Tch in the same way as that in the cagelike pores and also that the low limit of the hysteresis loop that has been long recognized since 1965 is due to the occurrence of a vapor bubble in a stretched metastable liquid confined to the pores with decreasing pressure (cavitation). 相似文献
60.
Akira Hirao Masahiro Kitamura Mayumi Hayashi Surapich Loykulnant Kenji Sugiyama 《Macromolecular Symposia》2005,226(1):35-50
Anionic polymerizations of four new dual-functionalized styrene and α-methylstyrene derivatives, 3-(4-(4-isopropenylphenoxy)butyl)styrene ( 4 ), 3-(4-(2-isopropenylphenoxy)butyl)-α-methylstyrene ( 5 ), 4-(4-(4-isopropenylphenoxy)butyl)-α-methylstyrene ( 6 ), and 4-(4-(2-vinylphenoxy)butyl)styrene ( 7 ), were carried out in THF at -78 °C with sec-BuLi as an initiator. Both 4 and 5 underwent anionic polymerization in a living manner to quantitatively afford functionalized polystyrenes and poly(α-methylstyrene)s having α-methylstyrene moiety in each monomer unit and precisely controlled chain lengths. On the other hand, insoluble polymers were obtained by the anionic polymerization of 6 and 7 under the same conditions. The positional effect of substituent on anionic polymerization was discussed. 相似文献