全文获取类型
收费全文 | 221篇 |
免费 | 0篇 |
国内免费 | 3篇 |
专业分类
化学 | 120篇 |
晶体学 | 1篇 |
数学 | 103篇 |
出版年
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2008年 | 14篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 16篇 |
2004年 | 5篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 11篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 22篇 |
1981年 | 17篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有224条查询结果,搜索用时 234 毫秒
1.
A general procedure using triphenylphosphine and diethylazodicarboxylate to prepare 2-oxazolines is described. 相似文献
2.
3.
[reaction: see text] A synthesis of the C(43)-C(67) fragment of amphidinol 3 (AM3) has been accomplished by a route that features the use of a double allylboration reaction for synthesis of 1,5-diol 4b, which serves as a precursor to dihydropyran 11. 相似文献
4.
Syntheses of the vertical (3) and horizontal (4) bis-spirotetronate units of quartromicins A3 and D3 are described, along with an efficient synthesis of alpha-hydroxy aldehyde exo-8b, a precursor to the exo-spirotetronate fragments 19 and 21. 相似文献
5.
[reaction: see text] An efficient synthesis of the C(11)-C(29) fragment 31 of amphidinolide F has been accomplished via a diastereoselective [3 + 2]-annulation reaction of allylsilane 5 and ethyl glyoxylate to prepare the key tetrahydrofuran 15 and a highly stereoselective methyl ketone aldol reaction to generate the C(11)-C(16) segment. 相似文献
6.
syn-beta-Hydroxyallylsilanes of general structure 11 and 28 are prepared in 50-86% yield and 91-95% ee (for aliphatic aldehydes; 50% ee for benzaldehyde) via the BF(3).Et(2)O-promoted gamma-silylallylboration reactions, using reagents 14 and 15. 相似文献
7.
A synthesis of 2-epi-amphidinolide E (1) has been accomplished via an unexpected and highly diastereoselective C(2) stereochemical inversion during the modified Yamaguchi esterification of alcohol 4b and Fe(CO)3-complexed dienoic acid 7. [reaction: see text]. 相似文献
8.
Dunetz JR Julian LD Newcom JS Roush WR 《Journal of the American Chemical Society》2008,130(48):16407-16416
Convergent total syntheses of the potent cytotoxins (+)-tedanolide (1) and (+)-13-deoxytedanolide (2) are described. The carbon framework of these compounds was assembled via a stereoselective aldol reaction that unifies the C(1)-C(12) ketone fragment 5 with a C(13)-C(23) aldehyde fragment 6 (for 13-deoxytedanolide) or 52 (for tedanolide). Multiple obstacles were encountered en route to (+)-1 and (+)-2 that required very careful selection and orchestration of the stereochemistry and functionality of key intermediates. Chief among these issues was the remarkable stability and lack of reactivity of hemiketals 33b and 34 that prevented the tedanolide synthesis from being completed from aldol 4. Key to the successful completion of the tedanolide synthesis was the observation that the 13-deoxy hemiketal 36 could be oxidized to C(11,15)-diketone 38 en route to 13-deoxytedanolide. This led to the decision to pursue the tedanolide synthesis via C(15)-(S)-epimers, since this stereochemical change would destabilize the hemiketal that plagued the attempted synthesis of tedanolide via C(15)-(R) intermediates. However, use of C(15)-(S)-configured intermediates required that the side-chain epoxide be introduced very late in the synthesis, owing to the ease with which the C(15)-(S)-OH cyclized onto the epoxide of intermediate 50. 相似文献
9.
10.