全文获取类型
收费全文 | 491篇 |
免费 | 40篇 |
专业分类
化学 | 411篇 |
晶体学 | 7篇 |
力学 | 1篇 |
数学 | 3篇 |
物理学 | 95篇 |
无线电 | 14篇 |
出版年
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 16篇 |
2014年 | 14篇 |
2013年 | 22篇 |
2012年 | 19篇 |
2011年 | 41篇 |
2010年 | 23篇 |
2009年 | 15篇 |
2008年 | 36篇 |
2007年 | 35篇 |
2006年 | 30篇 |
2005年 | 31篇 |
2004年 | 32篇 |
2003年 | 20篇 |
2002年 | 26篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有531条查询结果,搜索用时 218 毫秒
31.
S. Nakahama M. Kobayashi T. Ishizone A. Hirao M. Kobayashi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):1845-1855
Abstract N,N-Dimethyl-, diethyl-, and dipropylacrylamides were polymerized with 1,1-bis(4′-trimethylsilylphenyl)-3-methylpentyllithium (I) in the presence and absence of diethylzinc in THF. Although the polymers produced with I in the absence of diethylzinc have rather broad molecular weight distributions, the addition of diethylzinc to the polymerization systems causes narrow molecular weight distributions of the polymers. The addition of diethylzinc also affect the stereospecificities of the polymers obtained. The poly(N,N-diethylacrylamide) produced with I/diethylzinc (molar ratio of 1/3-15) is highly syndiotactic, while the one obtained with I is isotactic. The configuration of the poly(N,N-dimethylacrylamide) is changed from isotactic to syndio and heterotactic rich by the addition of diethylzinc to the polymerization mixture. Little effect of diethylzinc is observed on the stereospecificity of the polymerization of N,N-dipropylacrylamide. The stoichiometric additive effect of Et2Zn toward the initiator in the polymerization of DEAA suggests that the coordination of Et2Zn aggregates with the propagating carbanionic species narrows the molecular weight distribution and controls the tacticity of the polymer. 相似文献
32.
The acceleration effect of poly(ethylene oxide) on nucleophilic reactions was investigated. The enhancement of the reaction rate was interpreted by the cooperative solvation of alkali metal ions with ethereal oxygens of PEO resulting in active nucleophilic anions. In relation to the complex formation of alkali metal ions with PEO, the oligo(ethylene oxide) derivatives were prepared as the synthetic ionophores, which were able to transport alkali metal ions selectively through a liquid membrane against the alkali metal ion concentration. 相似文献
33.
Syntheses of cyclic oligomer and polymer were attempted with magnesiacyclohexane as the initiator in HMPA. The oligomer of α-methylstyrene, initiated by magnesiacyclohexane, was treated with dimethyldichlorosilane in order to obtain a stable cyclic oligomer. The products were investigated by GPC, IR, NMR, and elemental analysis. It was found that magnesia-cyclohexane could not be activated enough by HMPA, and that the magnesium-carbon bond was not stable in HMPA, and that the chain transfer reaction might occur repeatedly during the polymerization. Consequently, the yield of cyclic oligomer was so low that cyclic compounds could not be discriminated from the linear oligomer. 相似文献
34.
35.
Dr. Toru Amaya Riyo Suzuki Prof. Dr. Toshikazu Hirao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):653-656
N,N′‐Diphenyl‐p‐benzoquinonediimine, a redox‐active unit of polyaniline, efficiently induced the oxidative homocoupling of various aryl‐ and vinylmagnesium reagents in suppressing the side reactions, such as 1,2‐ or 1,4‐addition reaction. 相似文献
36.
37.
Kazuyoshi Kanamori Norio Ishizuka Kazuki Nakanishi Kazuyuki Hirao Hiroshi Jinnai 《Journal of Sol-Gel Science and Technology》2003,26(1-3):157-160
The organo-siloxane gel with co-continuous structure derived from methyltrimethoxysilane (MTMS) was synthesized in a confined space between parallel plates by inducing spinodal decomposition during sol-gel transition. The resultant gel morphology was 3-dimensionally observed by laser scanning confocal microscopy (LSCM). The sliced LSCM photographs revealed that the confined gels have inhomogeneity perpendicular to the plate, exhibiting a layered structure. The layered structure can be divided into three regions according to their morphology; interface, near-surface layer, bulk phase. The organo-siloxane depletion layer had formed in the vicinity of both hydrophobic and hydrophilic plates, and the bulk phase had formed slight away from the plates exhibited co-continuous structure. In addition, the confined gels exhibited no shrinkage during drying process that resulted in the larger domain size compared to the monolithic gel. The attractive interaction between the plates and the resultant organo-siloxane phase accounts for the inhibition of shrinkage of confined gels. 相似文献
38.
39.
Back Cover: Understanding the Origins of Nucleophilic Hydride Reactivity of a Sodium Hydride–Iodide Composite (Chem. Eur. J. 21/2016)
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
40.
Infrared femtosecond laser pulse induced permanent reduction of Eu3+ to Eu2+ in a fluorozirconate glass 总被引:3,自引:0,他引:3
We report what is believed to be the first observation of permanent photoreduction of Eu(3+) to Eu(2+) in transparent and colorless Eu(3+) -doped fluorozirconate glass at room temperature, using an infrared femtosecond laser. Difference absorption and electron-spin-resonance spectra of the glass before and after laser irradiation showed that a portion of the Eu(3+) ions in the focused part of the laser inside the glass were reduced to Eu(2+) ions after laser irradiation. It is suggested that Eu(3+) ions act as electron-trapping centers, whereas active sites in the glass matrix act as hole-trapping centers, leading to the formation of Eu(2+) ions. The observed phenomenon is inferred to be useful in the fabrication of optical memory devices with high storage density and waveguide-type micro-optical devices. 相似文献