全文获取类型
收费全文 | 1275篇 |
免费 | 71篇 |
国内免费 | 10篇 |
专业分类
化学 | 1012篇 |
晶体学 | 21篇 |
力学 | 10篇 |
数学 | 62篇 |
物理学 | 251篇 |
出版年
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 19篇 |
2020年 | 22篇 |
2019年 | 21篇 |
2018年 | 24篇 |
2016年 | 31篇 |
2015年 | 42篇 |
2014年 | 46篇 |
2013年 | 65篇 |
2012年 | 82篇 |
2011年 | 111篇 |
2010年 | 40篇 |
2009年 | 50篇 |
2008年 | 65篇 |
2007年 | 56篇 |
2006年 | 61篇 |
2005年 | 56篇 |
2004年 | 49篇 |
2003年 | 51篇 |
2002年 | 39篇 |
2001年 | 21篇 |
2000年 | 19篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1997年 | 15篇 |
1996年 | 6篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 19篇 |
1991年 | 10篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 15篇 |
1976年 | 6篇 |
1975年 | 14篇 |
1974年 | 8篇 |
1968年 | 6篇 |
排序方式: 共有1356条查询结果,搜索用时 31 毫秒
71.
Yasuhiro Igarashi Daisuke Asano Kazuo Furihata Naoya Oku Satoshi Miyanaga Hiroaki Sakurai Ikuo Saiki 《Tetrahedron letters》2012,53(6):654-656
During the course of screening natural products for the inhibitors of tumor cell invasion, pterocidin, a linear polyketide with a δ-lactone terminus, was rediscovered from a Streptomyces strain of a marine sediment-origin. A series of J-based configuration analyses and NOESY analysis, coupled with chemical derivatization and chiral anisotropy analysis, established the absolute stereochemistry of five asymmetric centers in this compound. 相似文献
72.
Kisuke Tabata Naoya Jinno Keiichi Noda Masahiko Hashimoto Kazuhiko Tsukagoshi 《Chromatographia》2012,75(7-8):423-428
Tube radical distribution chromatography (TRDC) uses an untreated open tubular capillary tube and a ternary mixture of solvents (water and hydrophilic/hydrophobic organic solvents) as a carrier solution. A model analyte mixture comprising 1-naphthol, 1-naphthoic acid, 1-naphthalenesulfonic acid, 2,6-naphthalenedisulfonic acid, and 1,3,6-naphthalenetrisulfonic acid was examined by the TRDC and capillary zone electrophoresis (CZE) systems that comprised mainly a capillary tube and a detector. In the TRDC system the elution order of analytes could be changed by altering the component ratios of the solvents, whereas in the CZE system the elution order was changed by altering the electroosmotic flow direction. The experimental data obtained provide clues about the features and utility of TRDC as a new separation method. 相似文献
73.
Ishibashi Chiaki Ichiyama Mai Ishida Naoya Kitamura Naoto Idemoto Yasushi 《Journal of Solid State Electrochemistry》2022,26(3):663-682
Journal of Solid State Electrochemistry - The stable structures associated with the second charge of MgCo2−xMnxO4 (x = 0, 0.5), where Mg is removed from the stable first-discharge... 相似文献
74.
Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating. 相似文献
75.
Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Angewandte Chemie (International ed. in English)》2013,52(1):223-234
A series of asymmetric catalysts composed of conformationally flexible amide‐based chiral ligands and rare‐earth metals was developed for proton‐transfer catalysis. These ligands derived from amino acids provide an intriguing chiral platform for the formation of asymmetric catalysts upon complexation with rare‐earth metals. The scope of this arsenal of catalysts was further broadened by the development of heterobimetallic catalytic systems. The cooperative function of hydrogen bonding and metal coordination resulted in intriguing substrate specificity and stereocontrol, and the dynamic nature of the catalysts led to a switch of their function. Herein, we summarize our recent exploration of this class of catalysts. 相似文献
76.
Takahiro Egawa Kazuhisa Hirabayashi Dr. Yuichiro Koide Chiaki Kobayashi Dr. Naoya Takahashi Dr. Tomoko Mineno Dr. Takuya Terai Dr. Tasuku Ueno Dr. Toru Komatsu Dr. Yuji Ikegaya Prof. Norio Matsuki Prof. Tetsuo Nagano Dr. Kenjiro Hanaoka 《Angewandte Chemie (International ed. in English)》2013,52(14):3874-3877
77.
During the course of studies on butenolide synthesis1 we have investigated the utilities of 3-sulfur-functionalized propionic acid derivatives. We report the results with 3-carbanion species obtained from 3-phenylsulfiny1- and 3-phenylsulfonylpropionic acids (1) and (2). These compounds were easily prepared from 3-phenylthiopropionic acid. 相似文献
78.
Naoya Hosoda Hideaki Kamito Miki Takano Yoshitaka Takebe Yoshitaka Yamaguchi Masatoshi Asami 《Tetrahedron》2013,69(6):1739-1746
Chiral diamines, 2-(anilinophenylmethyl)pyrrolidines and 2-(anilinodiphenylmethyl)pyrrolidine, were prepared from N-(tert-butoxycarbonyl)pyrrolidine or (S)-proline as a starting material, respectively. These chiral diamines were efficient for the catalytic enantioselective borane reduction of acetophenone. Using (S)-2-(anilinodiphenylmethyl)pyrrolidine, chiral secondary alcohols were obtained from prochiral ketones with good to excellent enantiomeric excesses (up to 98% ee). 相似文献
79.
Nobuyoshi Yamashita Yoshikuni Urushigawa Shigeki Masunaga Mohamed I. Walash Akira Miyazaki 《International journal of environmental analytical chemistry》2013,93(4):289-303
Abstract To assess the risks of organochlorine pesticides discharged into the hydrospheric environment of Egypt, river and lake water, drinking water, suspended solids, sediments and fish were collected during 1993—1994 from the Nile River and Manzala Lake in Egypt and were transported to Japan for chemical analysis. Among different organochlorine pesticides analyzed, p,p′-DDE was the most predominant in fish (7.6 to 67 ng/g wet wt.), sediments (3.2 to 432 ng/g dry wt.) and suspended solids (5.3 tc 138 pg/L). However, in the dissolved phase of water samples HCH compounds predominated (α-HCH, 71 to 2,815 pg/L). Concentrations of organochlorine pesticides, except chlordane, were higher in Manzala Lake than in the River Nile. Concentrations of organochlorine pesticides in fish corresponded with those in sediments from each location. Comparison of organochlorine concentrations in Nile River water with those reported in earlier studies suggested a decrease in concentrations during the last decade. However, concentrations of p,p′-DDE has increased in fish. It appears that the release of this metabolite from contaminated sediment is the major source of p,p′-DDE in fish during recent years. 相似文献
80.
Shin-ichi Kondo Naoya Watanabe Fubuki Takahashi Nobuhiro Takeda Masafumi Unno 《Journal of inclusion phenomena and macrocyclic chemistry》2013,75(1-2):31-38
Two trimethylsilyl groups were introduced at 5- and 5′-positions of 2,2′-binaphthalene to improve the solubility of 2,2′-binaphthalene-based receptors. The X-ray crystallographic analysis revealed the twisted structure of 2 in the solid state. The solubility of 2 was moderately improved by 3.1-fold comparing with mother skeleton 1. As a practical example of 2, receptor 8 bearing two aza-15-crown-5 moieties was prepared and the selective binding of 8 with Ba2+ can be observed by the formation of sandwich-like complex, which shows no prevention of binding ability of the receptor by introduction of the bulky substituents. 相似文献