全文获取类型
收费全文 | 988篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
化学 | 789篇 |
晶体学 | 6篇 |
力学 | 11篇 |
数学 | 94篇 |
物理学 | 110篇 |
出版年
2021年 | 5篇 |
2020年 | 9篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 16篇 |
2014年 | 14篇 |
2013年 | 47篇 |
2012年 | 40篇 |
2011年 | 71篇 |
2010年 | 24篇 |
2009年 | 23篇 |
2008年 | 39篇 |
2007年 | 47篇 |
2006年 | 56篇 |
2005年 | 50篇 |
2004年 | 61篇 |
2003年 | 40篇 |
2002年 | 42篇 |
2001年 | 26篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 22篇 |
1997年 | 16篇 |
1996年 | 21篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 6篇 |
1991年 | 18篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 23篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1970年 | 4篇 |
1969年 | 5篇 |
排序方式: 共有1010条查询结果,搜索用时 15 毫秒
1.
2.
The consecutive reactions of (CH3)2Si(OC2H5)2 and CH3Si(OC2H5)3 with methoxide ions were investigated in methanol solutions. The reverse transesterification reactions with ethoxide ions could be neglected in both cases since the concentration of ethoxide in methanol solution was assumed to be low due to the fast equilibrium reaction C2H5O? + CH3OH ? C2H5OH + CH3O?. The progress of the reactions was followed by monitoring the formation of ethanol with a Fourier-transform infrared spectrometer. All rate constants were determined at 295 K. The reactions between the dialkoxydimethylsilanes and methoxide ions were assumed to consist of two consecutive steps that can be represented by the net reaction; (CH3)2Si(OC2H5)2 + 2CH3O? → (CH3)2Si(OCH3)2 + 2C2H5O?. The two consecutive rate constants were established as 1.93 ± 0.12M?1s?1 and 1.00 ± 0.12M?1s?1, respectively. The consecutive rate constants for the reactions between the trialkoxymethylsilanes and methoxide ions can be written according to the total reaction; CH3Si(OC2H5)3 + 3CH3O? → CH3Si(OCH3)3 + 3C2H5O?. The three rate constants corresponding to each consecutive step were established as 1.12 ± 0.09 M?1s?1, 0.82 ± 0.10 M?1s?1, and 0.51 ± 0.06 M?1s?1, respectively. © 1995 John Wiley & Sons, Inc. 相似文献
3.
4.
5.
6.
Ulf Pindur Ludwig Pfeuffer Manfred Eitel Martina Rogge Manfred Haber 《Monatshefte für Chemie / Chemical Monthly》1991,122(4):291-298
Summary Diels-Alder reactions of 2- and 3-vinylindoles with aryne, 1,4-benzo- and 1,4-naphtho-quinone lead to new six-ring annellated carbazoles. Molecular modeling studies predict that the compounds with coplanar framework are able to intercalate with the B-DNA. 相似文献
7.
8.
K Betke 《The Journal of the Acoustical Society of America》1991,89(5):2400-2403
Hearing thresholds for pure tones were measured under free-field listening conditions in the frequency range of 40 Hz-15 kHz. Results are consistent with the standard threshold specified in ISO 226 for frequencies up to 250 Hz, but a few dB below the ISO curve at higher frequencies. Thresholds are distributed normally on a logarithmic level scale with a standard deviation of approximately 5 dB. No significant differences between thresholds of male and female subjects were observed. 相似文献
9.
A straightforward process for the encapsulation of HbHNL under low methanol conditions has been developed. By adding a sol, prepared by hydrolysis of TMOS/MTMS at pH 2.8 with continuous removal of methanol, to a stirred solution of the enzyme in a buffer at pH 6.5, at least 65% of the activity of the free enzyme could be recovered after the encapsulation. The aquagels were successfully used in the synthesis of (S)-cyanohydrins. 相似文献
10.