全文获取类型
收费全文 | 992篇 |
免费 | 61篇 |
国内免费 | 6篇 |
专业分类
化学 | 649篇 |
晶体学 | 7篇 |
力学 | 40篇 |
综合类 | 1篇 |
数学 | 97篇 |
物理学 | 265篇 |
出版年
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 28篇 |
2015年 | 34篇 |
2014年 | 37篇 |
2013年 | 52篇 |
2012年 | 82篇 |
2011年 | 73篇 |
2010年 | 45篇 |
2009年 | 59篇 |
2008年 | 49篇 |
2007年 | 51篇 |
2006年 | 46篇 |
2005年 | 39篇 |
2004年 | 31篇 |
2003年 | 20篇 |
2002年 | 27篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 23篇 |
1998年 | 8篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 13篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1974年 | 7篇 |
1973年 | 4篇 |
1970年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有1059条查询结果,搜索用时 187 毫秒
51.
(2-Bromoethyl)oxirane is converted in 39% yield to poly-[(2-bromoethyl)oxirane] of inherent viscosity 1.99 dL/g. The AlEt3/H2O/AcAc system is a very effective initiator for the polymerization of (2-bromoethyl)oxirane. Poly[(2-bromoethyl)-oxirane] is a white elastomer, soluble in CHCl3 and insoluble in CH3OH. Polyether-urethane hydrogels are prepared by the room temperature crosslinking of poly[(3-hydroxypropyl)oxirane] with aliphatic or aromatic diisocyanates. These networks absorb 100–200% of their weights in water, and can be prepared in transparent form with potential application as biomaterials or contact lenses. 相似文献
52.
Cindy X. Qiu Ishiang Shih 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):409-417
Abstract Using thin film devices of the form CdS(n)/CuInSe2(p) fabricated on electrodeposited CuInSe2, electrical and optical measurements have been made. From temperature-dependent I-V measurements, it was observed that the recombination current became progressively more important as the temperature was decreased. Results of dark C-V measurements indicated that CuInSe2 films with carrier concentrations in the range from 1015 to 1017 cm?3 can be easily prepared using the electrodeposition method. Photoresponse of the devices was also measured, giving an essentially flat region in the range from 0.6 to 1.0 micron. At wavelengths beyond 1 micron, the quantum efficiency decreased continuously with the increase in the wavelength. This continuous decrease in the quantum efficiency could be due to the presence of interface states as suggested by the photo capacitance measurements. 相似文献
53.
54.
Hélène Beucher Dr. Sudhir Kumar Dr. Roopender Kumar Dr. Estíbaliz Merino Wei-Hsu Hu Gerrit Stemmler Sergio Cuesta-Galisteo Dr. Jorge A. González Léonard Bezinge Dr. Jakub Jagielski Dr. Chih-Jen Shih Prof. Dr. Cristina Nevado 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17604-17612
Efficient OLED devices have been fabricated using organometallic complexes of platinum group metals. Still, the high material cost and low stability represent central challenges for their application in commercial display technologies. Based on its innate stability, gold(III) complexes are emerging as promising candidates for high-performance OLEDs. Here, a series of alkynyl-, N-heterocyclic carbene (NHC)- and aryl-gold(III) complexes stabilized by a κ3-(N^C^C) template have been prepared and their photophysical properties have been characterized in detail. These compounds exhibit good photoluminescence quantum efficiency (ηPL) of up to 33 %. The PL emission can be tuned from sky-blue to yellowish green colors by variations on both the ancillary ligands as well as on the pincer template. Further, solution-processable OLED devices based on some of these complexes display remarkable emissive properties (ηCE 46.6 cd.A−1 and ηext 14.0 %), thus showcasing the potential of these motifs for the low-cost fabrication of display and illumination technologies. 相似文献
55.
Xingwen Lu Lingmin Zeng Kaimin Shih 《Journal of Physics and Chemistry of Solids》2012,73(9):1191-1195
A new ternary intermetallic compound, Nd2Cu0.8Ge3, was synthesized and its crystal structure was determined by Rietveld refinement of X-ray powder diffraction data. The Nd2Cu0.8Ge3 compound crystallizes in space group I41/amd (No. 141), with a tetragonal a-ThSi2 structure type, and a=0.41783(2) nm, c=1.43689(9) nm, Z=2 and Dcalc=7.466 g/cm3. Using the high temperature powder X-ray diffraction (HTXRD) technique, the lattice thermal expansion behavior of the compound was investigated in the temperature range of 298–648 K, and the result shows that its unit-cell parameters increased anisotropically when temperature increased. The magnetic susceptibility measured in the temperature range of 5–300 K indicated antiferromagnetic order of Nd2Cu0.8Ge3 at low temperatures, and the magnetic susceptibility can be well described over the range of 50–300 K using Curie–Weiss law. The calculated effective magnetic moment (μeff) is 3.53 μB and dominated by the contribution of the Nd3+ ions. 相似文献
56.
57.
A general method for the preparation of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines is described. These heterocycles can be synthesized from their respective anilines with 2‐chloro‐2‐imidazoline or 2‐chloro‐1,4,5,6‐tetrahydropyrimidine, generated in situ from imidazolidin‐2‐one and tetrahydropyrimidin‐2(1H)‐one activated by dimethyl chlorophosphate, in good to excellent yields. 相似文献
58.
Jiun-An Gu Yu-Jen Lin Yu-Ming Chia Hsin-Yi Lin Sheng-Tung Huang 《Mikrochimica acta》2013,180(9-10):801-806
We report on a sensitive detection scheme for fluoride that is based on a quinone-methide-type of rearrangement reaction to trigger a color change among cloaked gold nanoparticle agglomeration probes. Fluoride ions remove silyl moieties from phenol groups on the surface of the probes, and this causes a quinone-methide-type of rearrangement reaction to occur. This is accompanied by the release of a dithiol in a spontaneous and irreversible reaction at room temperature in aqueous medium. The released dithiol causes aggregation of the AuNPs which leads to a color change from pink-red to violet-blue that can easily be seen with bare eyes.. The generation of color by this cascade reactions is only caused by fluoride and not interfered by any other anions. The assay platform developed here offers a sensitive colorimetric assay for fluoride. The lower limit of detection is 120 μM, and the dynamic concentration range is from 120 μM to 1.5 mM. Figure
We report on a sensitive detection scheme for fluoride that is based on a quinone-methide-rearrangement reaction to trigger a color change among cloaked gold nanoparticle agglomeration probes. The lower limit of detection is 120 μM, and the dynamic concentration range is from 120 μM to 1.5 mM. 相似文献
59.
In practical applications, information about the accuracy or ‘fidelity’ of alternative surrogate systems may be ambiguous and difficult to determine. To address this problem, we propose to treat surrogate system fidelity level as a categorical factor in optimal response surface design. To design the associated experiments, we apply the Expected Integrated Mean Squared Error optimal design criterion, which takes into account both variance and bias errors. The performance of the proposed design was compared using three test cases to four types of alternatives using the Empirical Integrated Squared Error. Because of its ability to foster relatively accurate predictions, the proposed design is recommended in fidelity experimental design, particularly when the experimenters lack sufficient information about the fidelity levels of surrogate systems. The method was applied to the case of intraday trading optimization in which data were collected from the Taiwan Futures Exchange. We also calculated the implied volatility from the Merton's Jump‐diffusion model via the fast Fourier transform algorithm with three different models of varying fidelity levels. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
60.
Jayachandran Jayakumar Kanniyappan Parthasarathy Yi‐Hsiang Chen Tai‐Hua Lee Shih‐Ching Chuang Chien‐Hong Cheng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(37):10047-10050
A new method for the synthesis of highly substituted naphthyridine‐based polyheteroaromatic compounds in high yields proceeds through rhodium(III)‐catalyzed multiple C H bond cleavage and C C and C N bond formation in a one‐pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π‐conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation‐assisted ortho C H activation, alkyne insertion, and reductive elimination, is proposed for this transformation. 相似文献