全文获取类型
收费全文 | 1562篇 |
免费 | 67篇 |
国内免费 | 4篇 |
专业分类
化学 | 1188篇 |
晶体学 | 17篇 |
力学 | 32篇 |
数学 | 83篇 |
物理学 | 313篇 |
出版年
2023年 | 15篇 |
2022年 | 44篇 |
2021年 | 53篇 |
2020年 | 40篇 |
2019年 | 30篇 |
2018年 | 36篇 |
2017年 | 43篇 |
2016年 | 53篇 |
2015年 | 45篇 |
2014年 | 71篇 |
2013年 | 105篇 |
2012年 | 148篇 |
2011年 | 152篇 |
2010年 | 73篇 |
2009年 | 55篇 |
2008年 | 94篇 |
2007年 | 92篇 |
2006年 | 82篇 |
2005年 | 98篇 |
2004年 | 63篇 |
2003年 | 62篇 |
2002年 | 39篇 |
2001年 | 28篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1964年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有1633条查询结果,搜索用时 15 毫秒
131.
Takashi Seo 《Journal of multivariate analysis》2006,97(9):1976-1983
In this paper, we consider simultaneous confidence intervals for all contrasts in the means when the observations are missing at random in the intraclass correlation model. An exact test statistic for the equality of the means and Scheffé, Bonferroni and Tukey types of simultaneous confidence intervals are given by an extension of Bhargava and Srivastava [On Tukey's confidence intervals for the contrasts in the means of the intraclass correlation model, J. Royal Statist. Soc. B35 (1973) 147-152] when the missing observations are of the monotone type. Finally, numerical results of simultaneous confidence intervals are presented. 相似文献
132.
Eu(2+)-doped monophosphates NaSrPO(4) and KBaPO(4) with the β-K(2)SO(4) structure were synthesized using the conventional high temperature solid state reaction. The X-ray powder diffraction, photoluminescence excitation, and emission spectra and decay curves were measured. The phosphors can be efficiently excited by UV-visible light from 220 to 430 nm to realize emission in the visible range. The natures of the Eu(2+) emission, e.g., the chromaticity coordinates, the Stokes shifts, and the luminescence absolute quantum efficiencies, were reported. The luminescence quenching temperatures and the thermal activation energies for NaSrPO(4):Eu(2+) and KBaPO(4):Eu(2+) were obtained from the temperature dependent (10-435 K) luminescence intensities and decay curves. KBaPO(4):Eu(2+) presents only one emission center; however, Eu(2+) ions have a "disordered environment" in NaSrPO(4) lattices. The relationship between the luminescence thermal stabilities and the crystal structures was discussed. The crystallographic occupations of rare earth ions doped in these hosts were analyzed by the site-selective emission spectra and the excitation spectra of Eu(3+) ions in the (7)F(0)→(5)D(0) transitions using a pulsed, tunable, and narrow-band dye laser. In KBaPO(4), the Eu(3+) ions could be distributed in the host with a high "ordered state" in only one site in the lattices. However, the multiple site structure of Eu(3+) ions with highly disordered distributions in NaSrPO(4) lattices was suggested. 相似文献
133.
Dr. Robert J. Messinger Dr. Kyungsu Na Dr. Yongbeom Seo Prof. Dr. Ryong Ryoo Prof. Dr. Bradley F. Chmelka 《Angewandte Chemie (International ed. in English)》2015,54(3):927-931
Mesoporous zeolites are a new and technologically important class of materials that exhibit improved diffusion and catalytic reaction properties compared to conventional zeolites with sub‐nanometer pore dimensions. During their syntheses, the transient developments of crystalline and mesoscopic order are closely coupled and challenging to control. Correlated solid‐state NMR, X‐ray, and electron microscopy analyses yield new molecular‐level insights on the interactions and distributions of complicated organic structure‐directing agents with respect to crystallizing zeolite frameworks. The analyses reveal the formation of an intermediate layered silicate phase, which subsequently transforms into zeolite nanosheets with uniform nano‐ and mesoscale porosities. Such materials result from coupled surfactant self‐assembly and inorganic crystallization processes, the interplay between which governs the onset and development of framework structural order on different length and time scales. 相似文献
134.
Ki Cheol Hwang Hyun Young Shin Woo Jung Kim Mi Suk Seo Hoon Kim 《Molecules (Basel, Switzerland)》2021,26(6)
Persimmon (Diospyros kaki), a familiar and widespread fruit worldwide, is known to exhibit several physiological effects because of the presence of pharmacologically active compounds called phytochemicals. However, its high-molecular-weight compounds, particularly polysaccharides, have not been extensively studied. In this study, D. kaki extract (DK) was fractionated into low- and high-molecular-weight fractions (DK-L and DK-H, respectively) through ethanol fractionation, and their effects on antioxidant, anti-inflammatory, and antiwrinkle activities were investigated by an in vitro system. DK-H contained significantly higher contents of neutral sugar, uronic acid, and polyphenols compared to DK and DK-L. Furthermore, DK-H exhibited significantly improved pharmacological activities, such as antioxidant, anti-inflammatory, and antiwrinkle properties, compared to those of DK and DK-L, demonstrating that DK-H may play an important role in mediating the beneficial effects of persimmon. Sugar composition analysis and molecular characterization indicated that DK-H consisted of a galacturonic acid (GalA)-rich polysaccharide with a molecular weight of >345 kDa that mainly comprised GalA and small amounts of neutral sugar and polyphenol residues. These results suggest that the bioactive fraction DK-H is likely to be a GalA-rich pectic polysaccharide containing a small number of polyphenol residues, which may be a novel candidate in the pharmaceutical and cosmeceutical industries. 相似文献
135.
We investigated pretilt angle generation and liquid crystal (LC) alignment by ultraviolet exposure during the imidization of polyimide (PI). The generated pretilt angle of a nematic (N) LC using an in situ photo-alignment method is smaller than that using a conventional photo-alignment method on a surface of PI having side chains. The NLC pretilt angles using an in situ photo-alignment method injected at isotropic phase increased with annealing were observed. 相似文献
136.
A new photoalignment material, copoly(4-methacryloyloxychalcone-cholesteryl methacrylate) (copoly(M4Ch-ChMA)), was synthesized and the electro-optical characteristics for the photoaligned vertically aligned (VA) liquid crystal display (LCD) were studied. Excellent voltagetransmittance characteristics were achieved for the photoaligned VA-LCD with 1 min polarized UV exposure at an oblique direction of 30° on the copoly(M4Ch-ChMA) surfaces. The response time of the VA-LCD was about 39 ms, and increased with increasing UV exposure time. We suggest that the proportion of photodimerized chalcone group increased with increasing UV exposure time, contributing to a higher response time. 相似文献
137.
Abstract The hysteresis behaviour of the nematic-cholesteric phase transition in liquid crystals is closely connected with the alignment of the liquid crystal molecules on the surfaces of treated solid substrates. We have investigated the hysteresis as a function of rubbing strength, using rubbing technology that controls the orientation of the liquid crystal molecules. The surface alignment direction contributes to the hysteresis width, is not dependent on rubbing strength, and is only slightly related to pretilt angles. A no-rubbing treatment, that is, random alignment, is important in-order to create a large hysteresis width on homogeneously aligned polyimide films. 相似文献
138.
Daigeun Kim Geunseok Jang Jongho Kim Seongwon Seo Won Ho Park Taek Seung Lee 《Macromolecular rapid communications》2012,33(18):1510-1516
A highly efficient colorimetric and fluorescence turn‐off probe for the sensitive and selective detection of the biologically important amino acid, cysteine (Cys), is demonstrated using a newly synthesized water‐soluble hyperbranched polymer (HP) containing sulfonic acid groups. The detection mechanism involves two steps: (i) the slight quenching of HP in the presence of Co2+ in advance; and (ii) the gradual quenching of the HP–Co2+ complex according to the concentration of Cys due to the absorption screening effect of the formation of the Cys‐Co2+ complex, which prevents HP from absorbing excitation energy. 相似文献
139.