全文获取类型
收费全文 | 1092篇 |
免费 | 22篇 |
国内免费 | 6篇 |
专业分类
化学 | 797篇 |
晶体学 | 10篇 |
力学 | 22篇 |
数学 | 55篇 |
物理学 | 236篇 |
出版年
2023年 | 9篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 4篇 |
2016年 | 12篇 |
2015年 | 10篇 |
2014年 | 27篇 |
2013年 | 38篇 |
2012年 | 50篇 |
2011年 | 56篇 |
2010年 | 24篇 |
2009年 | 30篇 |
2008年 | 66篇 |
2007年 | 55篇 |
2006年 | 64篇 |
2005年 | 44篇 |
2004年 | 48篇 |
2003年 | 49篇 |
2002年 | 28篇 |
2001年 | 34篇 |
2000年 | 25篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 14篇 |
1994年 | 20篇 |
1993年 | 16篇 |
1992年 | 35篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 10篇 |
1988年 | 15篇 |
1987年 | 20篇 |
1986年 | 24篇 |
1985年 | 27篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1973年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有1120条查询结果,搜索用时 0 毫秒
81.
Rotational isomers (rotamers) of the three structural isomers of benzenedicarboxaldehydes (1,2-, 1,3-, and 1,4-derivatives) have been investigated in detail using matrix-isolation infrared spectroscopy in the 600-4000 cm-1 region, combined with UV photoexcitation and density-functional theory (DFT) calculations. Two rotamers were identified for 1,2- and 1,4-benzenedicarboxaldehyde (1,2- and 1,4-BDA, respectively), while three rotamers were identified for 1,3-benzenedicarboxaldehyde (1,3-BDA) in infrared spectra upon UV-irradiation. Most of the observed infrared bands of each rotamer have been assigned. The energetic relationships among the rotamers were revealed based on the infrared data and the DFT calculations. It is shown that the intramolecular C-H...H-C interaction in the H-syn rotamer or the C-H...O=C hydrogen bonding in the anti rotamer of 1,2-BDA results in the blue-shift of the aldehyde C-H stretching band and the shortening of the aldehyde C-H bond length. Both photoinduced rotational isomerization and rearrangement were observed upon UV irradiation for 1,2-BDA. The structure of the major enol isomer formed as the result of the photochemical rearrangement of 1,2-BDA is determined. 相似文献
82.
The buffer extracts (3S) of sclerotia of Sclerotinia sclerotiorum IFO 9395 contained mitogenic substance(s) to murine splenocytes (Shinohara et al. Chem. Pharm. Bull., 38, 2219 (1990)). Although the native 3S was slightly mitogenic, heating of 3S induced significant mitogenic activity. To isolate the mitogen, we separated 3S by ion-exchange and gel filtration chromatographies. The isolated mitogen, named sclerogen, has a molecular mass of 32 kilodaltons (kDa) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the isoelectric point (pI) of 5.9 by chromatofocusing. Sclerogen was significantly mitogenic in vitro against murine splenocytes after heat denaturation, and also showed the augmentation of the primary mixed lymphocyte reaction (MLR) in vitro. However, sclerogen did not show the activation of an alternative pathway of complement and hemagglutination activity. These results suggest that sclerogen is a unique mitogen which differs from lectins and shows mitogenicity after heat denaturation. 相似文献
83.
Y Nomoto H Takai T Hirata M Teranishi T Ohno K Kubo 《Chemical & pharmaceutical bulletin》1991,39(1):86-90
A series of 1-(6,7-dimethoxy-4-quinazolinyl)piperidines carrying various 5-membered heterocycles at the 4-position was synthesized and examined for cardiotonic activity in anesthesized dogs. The (4-oxo-2-thioxo-3-imidazolindinyl)amino derivatives showed the most potent inotropic activity. Marked loss of activity was observed in the 2,4-dihydro-3-thioxo-3H-1,2,4-triazolyl, the 2,4-dihydro-3-oxo-3H-pyrazolyl and the (2,3-dihydro-2-thioxo-3H-1,3,4-thiadiazol-5-yl)amino derivatives. The synthesis and structure-activity relationships are discussed. 相似文献
84.
Yoshinori Tominaga Syuichirou Ohno Shinya Kohra Hiroshi Fujito Hisako Mazurae 《Journal of heterocyclic chemistry》1991,28(4):1039-1042
N-Bis(methylthio)methylenecyanamide ( 1 ) was allowed to react with active methylene compounds (methyl cyanoacetate, dimethyl malonate, ethyl acetoacetate, ethyl phenylacetate) in the presence of potassium carbonate or potassium hydroxide in dimethyl sulfoxide followed by the treatment using appropriate a base or an acid to give the corresponding 6-methylthiouracil derivatives in 15–80% yields. These uracil derivatives are found to be useful intermediates for the synthesis of 6-aminouracils and fused pyrimidine derivatives. 相似文献
85.
Ananya Banik Theodosios Famprikis Michael Ghidiu Saneyuki Ohno Marvin A. Kraft Wolfgang G. Zeier 《Chemical science》2021,12(18):6238
The development of high-performance inorganic solid electrolytes is central to achieving high-energy- density solid-state batteries. Whereas these solid-state materials are often prepared via classic solid-state syntheses, recent efforts in the community have shown that mechanochemical reactions, solution syntheses, microwave syntheses, and various post-synthetic heat treatment routines can drastically affect the structure and microstructure, and with it, the transport properties of the materials. On the one hand, these are important considerations for the upscaling of a materials processing route for industrial applications and industrial production. On the other hand, it shows that the influence of the different syntheses on the materials'' properties is neither well understood fundamentally nor broadly internalized well. Here we aim to review the recent efforts on understanding the influence of the synthetic procedure on the synthesis – (micro)structure – transport correlations in superionic conductors. Our aim is to provide the field of solid-state research a direction for future efforts to better understand current materials properties based on synthetic routes, rather than having an overly simplistic idea of any given composition having an intrinsic conductivity. We hope this review will shed light on the underestimated influence of synthesis on the transport properties of solid electrolytes toward the design of syntheses of future solid electrolytes and help guide industrial efforts of known materials.Influence of synthesis and processing on the nature of ultimate product and the ionic transport properties of superionic conductors. 相似文献
86.
Yongjoon Kim Prof. Dr. Tomohiro Iwai Prof. Dr. Sho Fujii Prof. Dr. Kosei Ueno Prof. Dr. Masaya Sawamura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2289-2293
2,2’-Bipyridine ligands (dsbpys) with dumbbell-like shapes and differently substituted triarylmethyl groups at the C5 and C5’ positions showed high ligand performance in the Ni-catalyzed cross-electrophile coupling and the Ni/photoredox-synergistically catalyzed decarboxylative coupling reactions. The superior ligand effects of dsbpys compared to the conventional bpy ligands were attributed to the monochelating nature of dsbpys. 相似文献
87.
Anionic cycloaddition of methyl isocyanoacetate to diethoxyacetonitrile afforded methyl 5-diethoxymethylimidazole-4-carboxylate, a useful imidazole nucleus with two different functional groups. 相似文献
88.
The reactions of α-silyloxy-ga,β-unsaturated ketone and aldehyde with diene afforded [4+2] and [4+3] cycloadducts respectively in the presence of a catalyst. 相似文献
89.
Atsuyoshi Ohno Yuji Ishihara Satoshi Ushida Shinzaburo Oka 《Tetrahedron letters》1982,23(31):3185-3188
Benzaldehyde are reduced to benzyl alcohol by a model compound of NAD(P)H almost quantitatively. Reductions of some other aldehydes are also mentioned. 相似文献
90.