全文获取类型
收费全文 | 454111篇 |
免费 | 3187篇 |
国内免费 | 914篇 |
专业分类
化学 | 224399篇 |
晶体学 | 6674篇 |
力学 | 23369篇 |
综合类 | 9篇 |
数学 | 61701篇 |
物理学 | 142060篇 |
出版年
2020年 | 4532篇 |
2019年 | 5395篇 |
2018年 | 7673篇 |
2017年 | 7806篇 |
2016年 | 10237篇 |
2015年 | 5127篇 |
2014年 | 9146篇 |
2013年 | 18857篇 |
2012年 | 14837篇 |
2011年 | 17560篇 |
2010年 | 13743篇 |
2009年 | 13860篇 |
2008年 | 17049篇 |
2007年 | 16832篇 |
2006年 | 15446篇 |
2005年 | 13693篇 |
2004年 | 12752篇 |
2003年 | 11743篇 |
2002年 | 11899篇 |
2001年 | 11971篇 |
2000年 | 9577篇 |
1999年 | 7143篇 |
1998年 | 6482篇 |
1997年 | 6401篇 |
1996年 | 5937篇 |
1995年 | 5129篇 |
1994年 | 5250篇 |
1993年 | 5237篇 |
1992年 | 5427篇 |
1991年 | 5816篇 |
1990年 | 5685篇 |
1989年 | 5705篇 |
1988年 | 5413篇 |
1987年 | 5432篇 |
1986年 | 5148篇 |
1985年 | 6291篇 |
1984年 | 6637篇 |
1983年 | 5529篇 |
1982年 | 5928篇 |
1981年 | 5511篇 |
1980年 | 5158篇 |
1979年 | 5764篇 |
1978年 | 6005篇 |
1977年 | 6138篇 |
1976年 | 6185篇 |
1975年 | 5812篇 |
1974年 | 5680篇 |
1973年 | 5962篇 |
1972年 | 4620篇 |
1971年 | 4151篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Iodine(III)‐Catalyzed Rearrangements of Imides: A Versatile Route to α,α‐Dialkylated α‐Hydroxy Carboxylamides 下载免费PDF全文
Anna Ulmer Dr. Maciej Stodulski Stefanie V. Kohlhepp Christoph Patzelt Dr. Alexander Pöthig Dr. Wolfgang Bettray Dr. Tanja Gulder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1444-1448
A tertiary hydroxy group α to a carboxyl moiety comprises a key structural motif in many bioactive substances. With the herein presented metal‐free rearrangement of imides triggered by hypervalent λ3‐iodane, an easy and selective way to gain access to such a compound class, namely α,α‐disubstituted‐α‐hydroxy carboxylamides, was established. Their additional methylene bromide side chain constitutes a useful handle for rapid diversification, as demonstrated by a series of further functionalizations. Moreover, the in situ formation of an iodine(III) species under the reaction conditions was proven. Our findings clearly corroborate that hypervalent λ3‐benziodoxolones are involved in these organocatalytic reactions. 相似文献
92.
93.
94.
95.
96.
Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented. 相似文献
97.
Elasasy M. E. A. Elnaggar D. H. Hafez N. A. Abdel Azab M. E. Amr A. E. Omran M. M. Mohamed A. M. 《Russian Journal of General Chemistry》2021,91(5):915-925
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity.... 相似文献
98.
Colloid Journal - An Erratum to this paper has been published: https://doi.org/10.1134/S1061933X21330024 相似文献
99.
Vyacheslav V. Sentyurin Oleg A. Levitskiy Tatiana V. Magdesieva 《Current Opinion in Electrochemistry》2020
This mini-review highlights key structural features that should be taken into account when creating ambipolar redox-active closed-shell metal-free molecules. This type of compound is strongly required for the fabrication of all-organic ‘poleless’ batteries and semiconductors. The suggested strategies aimed at stabilization of both oxidized (cationic) and reduced (anionic) redox-states are based on the comprehensive analysis of the most successful structures taken from the recent publications. 相似文献
100.