全文获取类型
收费全文 | 877篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
化学 | 642篇 |
晶体学 | 10篇 |
力学 | 17篇 |
数学 | 59篇 |
物理学 | 168篇 |
出版年
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 29篇 |
2012年 | 32篇 |
2011年 | 46篇 |
2010年 | 26篇 |
2009年 | 32篇 |
2008年 | 45篇 |
2007年 | 57篇 |
2006年 | 63篇 |
2005年 | 46篇 |
2004年 | 43篇 |
2003年 | 38篇 |
2002年 | 32篇 |
2001年 | 22篇 |
2000年 | 9篇 |
1999年 | 15篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 13篇 |
1974年 | 4篇 |
1973年 | 9篇 |
1971年 | 2篇 |
排序方式: 共有896条查询结果,搜索用时 0 毫秒
171.
172.
Photo-induced enhancement of charge density wave current in the quasi-one-dimensional conductor TaS3
In the near vicinity of Peierls transition temperature TP, we have measured the V-I characteristics of the quasi-one-dimensional conductor TaS3 under dark and photo-irradiation conditions. It is found that a significant enhancement of CDW current occurs only around the threshold voltage Vt under photo-irradiation. This effect can be interpreted as a result of screening of pinning potential for CDW condensate by photo-excited quasi-particles (QP's). Further the distribution of pinning potential intensity is reflected in the behavior of V-I characteristics near Vt. Our finding suggests that the strength of pinning potential can be controlled by the photo-excited QP's in quasi-1D conductors. 相似文献
173.
Yuki Marubashi Tatsuro Higashi Shoichiro Hirakawa Seiji Tani Tomoki Erata Mitsuo Takai Jun Kawamata 《Optical Review》2004,11(6):385-387
The molecular chain orientation of mercerized cellulose II was examined by optical second harmonic generation (SHG) measurements. The SHG intensities of several kinds of mercerized cellulose II were found to be much larger than those expected for a structural model with an antiparallel molecular chain orientation as proposed by X-ray studies. This result suggests that the orientation of mercerized cellulose II is parallel as suggested by molecular dynamics simulation. © 2004 The Optical Society of Japan 相似文献
174.
Yong Feng Lu M. Takai S. Nagatomo S. Namba 《Applied Physics A: Materials Science & Processing》1988,47(4):319-325
Maskless etching of Mn-Zn ferrite in H3PO4 aqueous solution by Ar+-ion laser irradiation has been investigated to obtain high etching rates and aspect-ratios of etched grooves. The etching
processes have been found to be photochemical in the low laser power region and thermochemical in the high laser power region.
High etching rates of up to 340 μm/s and an aspect-ratio of 30 for slab structures have been achieved. In the case of high
aspect-ratio structure, the etching rate was limited by the low diffusion efficiency of etched products in the etchant. Periodic
ripple structures have been observed under specific etching conditions. 相似文献
175.
Shinichi Suto Hirotada Ise Mikio Karasawa 《Journal of Polymer Science.Polymer Physics》1986,24(7):1515-1524
An Abbé refractometer with a rotatable polarizer mounted on the eyepiece is used for determining the two principal refractive indices of birefringent concentrated solutions of ethyl cellulose in m-cresol and in acetic acid. At a certain concentration, birefringence appears for both systems, and the concentration agrees with that for the onset of iridescence (here defined as the critical concentration Ca for formation of the liquid-crystalline phase). The birefringence of concentrated solutions depends strongly on concentration and temperature and can be generalized by a master curve. The refractive index increments for both systems are almost independent of temperature at high concentrations. 相似文献
176.
177.
M. Hoshino M. Takai K. Fukuda K. Imura J. Hayashi 《Journal of polymer science. Part A, Polymer chemistry》1989,27(6):2083-2092
The application of NMR for natural organic compounds has been carried out from the early history of NMR. But they reported on the liquid state NMR and the samples were limited to the materials which dissolved in proper solvents. It has been possible to measure the samples in the solid state in 1970s and is widely used as a familiar analytical method in 1980s. Whereas some of the data is inadequate, concerning cellulose derivatives, in particular, only nitrate and acetate were reported by Patterson1 and Doyle,2 respectively. In this paper, the 13C CP/MAS solid state NMR spectra of several cellulose derivatives are shown and the relationship between the structure and spectrum is discussed. 相似文献
178.
Chitsakon Pakjamsai Noritomo Kobayashi Mikio Koyano Shintaro Sasaki Yusuke Kawakami 《Journal of polymer science. Part A, Polymer chemistry》2004,42(18):4587-4597
The insoluble fraction obtained from the hydrolysis and condensation of (4-dimethylamino-, 2-methyl-, and nonsubstituted)phenyltrimethoxysilanes in the presence of benzyltrimethylammonium hydroxide in benzene was characterized. IR, 1H NMR, and 29Si NMR suggested that the insoluble fraction was composed of RSi(O )3, that is, a T3 structure. X-ray diffraction indicated the presence of a long-range ordered structure composed of a mixture of crystals. Raman spectroscopy strongly suggested a cage structure by the presence of a ring-opening vibration assignable to a cubic structure at 475–482 cm−1. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4587–4597, 2004 相似文献
179.
M. Takai Y. F. Lu T. Koizumi S. Namba S. Nagatomo 《Applied Physics A: Materials Science & Processing》1988,46(3):197-205
Single crystal ferrite has been etched by focused Ar+ laser irradiation in a CCl4 gas atmosphere. The etched groove showed cracks due to thermal stresses when samples were etched by a laser vaporization process in a vacuum, while in a CCl4 atmosphere, such cracks were not observed. An etching rate of 68 /s obtained for a thermochemical process by laser irradiation was four orders of magnitude higher than that for a wet chemical etching process. A high aspect (depth-to-width) ratio of up to 10 was obtained for etched grooves. Under specific conditions, bending of the groove and orientation dependence in etching rate were observed. 相似文献
180.
On the von Neumann-Jordan constant for Banach spaces 总被引:2,自引:0,他引:2
Let be the von Neumann-Jordan constant for a Banach space . It is known that for any Banach space ; and is a Hilbert space if and only if . We show that: (i) If is uniformly convex, is less than two; and conversely the condition implies that admits an equivalent uniformly convex norm. Hence, denoting by the infimum of all von Neumann-Jordan constants for equivalent norms of , is super-reflexive if and only if . (ii) If , (the same value as that of -space), is of Rademacher type and cotype for any with , where ; the converse holds if is a Banach lattice and is finitely representable in or .