全文获取类型
收费全文 | 1044篇 |
免费 | 38篇 |
国内免费 | 5篇 |
专业分类
化学 | 854篇 |
晶体学 | 7篇 |
力学 | 18篇 |
数学 | 64篇 |
物理学 | 144篇 |
出版年
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 18篇 |
2019年 | 18篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 30篇 |
2015年 | 24篇 |
2014年 | 27篇 |
2013年 | 58篇 |
2012年 | 65篇 |
2011年 | 81篇 |
2010年 | 36篇 |
2009年 | 34篇 |
2008年 | 72篇 |
2007年 | 88篇 |
2006年 | 80篇 |
2005年 | 66篇 |
2004年 | 59篇 |
2003年 | 52篇 |
2002年 | 39篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 4篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1990年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1969年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有1087条查询结果,搜索用时 15 毫秒
21.
Syuji Fujii Shinji Yamashita Yuichi Kakigi Kodai Aono Sho Hamasaki Shin-ichi Yusa Yoshinobu Nakamura 《Colloid and polymer science》2013,291(5):1171-1180
Hydroxy-functional macrodisulfides have been synthesized by atom transfer radical polymerization of 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate in 2-propanol. Mean degrees of polymerization of the polymer chains beside the disulfide were fixed at 30, 60, and 90; since ATRP has reasonably good living character, the molecular weight distribution is relatively narrow. Furthermore, the macrodisulfides were reduced to synthesize corresponding thiol-terminated polymers with relatively narrow molecular weight distributions. 1H nuclear magnetic resonance and gel permeation chromatography were used to characterize the macrodisulfides and thiol-terminated polymers in terms of their chemical structure, molecular weight, and polydispersity, respectively. Dispersion polymerizations of styrene using the thiol-terminated hydroxy-functional polymers as a transtab (chain transfer agent + colloidal stabilizer) in ethanol resulted in colloidally stable submicrometer-sized polystyrene latex particles. Scanning electron microscopy, Fourier transform infrared spectroscopy, and elemental microanalysis were used to characterize the particles in terms of their morphologies, particle sizes and their distributions, and chemical compositions. 相似文献
22.
Inside Cover: Enhancement of Light Absorption Ability of Synthetic Chlorophyll Derivatives by Conjugation with a Difluoroboron Diketonate Group (Chem. Eur. J. 29/2016) 下载免费PDF全文
23.
Abstract
A stereoscopic method of identifying story patterns in literary works is newly developed. The pattern is extracted from textual information by the detection of thematically assigned keywords, and depicted as visual imageries. The applicability of the method is demonstrated in several of Shakespeare’s plays. The complex scenario patterns in Shakespeare’s tragedies are successfully captured with applying the method for two different themes in each play. As the result, the organization of story accompanying multiple themes in a single play has been obtained as a pair of visual imageries, i.e. stereoscopic story visualization. This approach, in combination with a quadrant analysis of the plots, allows us in interpretation further complexity of human psychology in the characters and scene-by-scene transitions in each play. 相似文献24.
25.
Yasuhiro Morisaki Masayuki GonYuichi Tsuji Yuichi KajiwaraYoshiki Chujo 《Tetrahedron letters》2011,52(42):5504-5507
A new [2.2]paracyclophane compound consisting of two 1,3,5-tris[(2,5-dimethylphenyl)ethynyl]benzenes stacked in proximity to each other. The compound exhibited a unique absorption band (cyclophane band) and an emission from the phane state, both of which were derived from the π-π stacking of the poorly extended conjugation systems of 1,3,5-tris[(2,5-dimethylphenyl)ethynyl]benzene. In addition, a conjugated microporous polymer (CMP) that comprises pseudo-para-substituted [2.2]paracyclophane was prepared. The obtained CMP is regarded as a polymer, in which 1,3,5-tris[(2,5-dimethylphenyl)ethynyl]benzenes are infinitely stacked to form a network structure. The CMP exhibited a type I nitrogen gas sorption profile and an H4-like hysteresis loop, and possessed the slit-like mesopores with a BET surface area of 501 m2 g−1. 相似文献
26.
Hideo Nagashima Yuichi KuboMitsunobu Kawamura Takashi NishikataYukihiro Motoyama 《Tetrahedron》2011,67(40):7667-7672
A triruthenium cluster, (μ3, η2, η3, η5-acenaphthylene)Ru3(CO)7 effectively catalyzes primary-alkylation reaction of electron-rich aromatic rings using a combination of hydrosilane and ester as a source of the primary-alkyl group. The reaction involves electrophilic substitution of arenes by carbocationic species stabilized by a neighboring alkoxy or siloxy group generated during the reduction of esters giving alkylated arenes after reductive removal of the alkoxy or siloxy group at the benzylic position. 相似文献
27.
We have developed an efficient method for preparation of triazolamers using a dicobalt hexacarbonyl complex of propargyl azides (CPA) as a synthetic component. Several types of CPAs possessing the side chains found in the natural amino acids were prepared by Nicholas reaction as well as by a reaction of propargyl azides with dicobalt octacarbonyl. Triazolamers with both amino and carboxyl termini were readily synthesized by repetitive reaction sequence involving a copper-catalyzed 1,3-dipolar cycloaddition followed by an oxidative deprotection. 相似文献
28.
Jie Zhu Dr. Ryota Osuga Prof. Ryo Ishikawa Prof. Naoya Shibata Prof. Yuichi Ikuhara Prof. Junko N. Kondo Prof. Masaru Ogura Prof. Jihong Yu Prof. Toru Wakihara Prof. Zhendong Liu Prof. Tatsuya Okubo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19837-19842
Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM-5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn-ZSM-5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity. 相似文献
29.
Soliman Mohamed A. Mohamed Nader M. A. Takamiya Koichi Sekimoto Shun Inagaki Makoto Oki Yuichi Ohtsuki Tsutomu 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(3):1099-1107
Journal of Radioanalytical and Nuclear Chemistry - To assess the capability of Kyoto University Research Reactor to supply the domestic needs of medical isotopes, its neutron flux has been fully... 相似文献
30.
Development of highly functional cesium selective adsorbents for the decontamination of high-activity-level water(HALW) from the Fukushima NPP-1 accident is very urgent. In order to selectively adsorb the radioactive cesium, three kinds of novel porous silica gels loaded with insoluble ferrocyanides(SLFC) were prepared using a successive impregnation/precipitation method. Based on the results of previous research, the SLFC composites have relatively large uptake ratio above 95%, distribution coefficients(Kd) above 103 cm3/g, and excellent adsorption kinetics even in seawater. The solidification results also indicate that zeolites have an excellent Cs immobilization characteristic, gas-trapping and self-sintering abilities, and low leachability. We chose three kinds of SLFC composites to achieve the optimization of solidification by mixing with nine kinds of additives at high temperatures(up to 1200 °C). The Cs contents in the three composites were estimated to be below 30% of the initial contents and decreased with the three stages at calcination temperatures ranging from 25 to 1200 °C. By contrast, the Cs immobilization ratio was markedly lowered by mixing with additives: of those, allophane had the best immobilization result. By increasing the additive ratio to 50 wt%, the Cs immobilization ratio became almost 100% and no volatilization of Cs was detected even after calcination at 1200 °C. This result indicates that calcination of the mixture of SLFC composites after adsorbing Cs+ ions and specific additives under appropriate ratio is effective for stable solidification. 相似文献