全文获取类型
收费全文 | 219980篇 |
免费 | 3917篇 |
国内免费 | 2862篇 |
专业分类
化学 | 117101篇 |
晶体学 | 3624篇 |
力学 | 11190篇 |
综合类 | 245篇 |
数学 | 24140篇 |
物理学 | 70459篇 |
出版年
2021年 | 2401篇 |
2020年 | 2474篇 |
2019年 | 3105篇 |
2018年 | 4138篇 |
2017年 | 4158篇 |
2016年 | 5522篇 |
2015年 | 3112篇 |
2014年 | 5282篇 |
2013年 | 9852篇 |
2012年 | 8138篇 |
2011年 | 9498篇 |
2010年 | 7585篇 |
2009年 | 7794篇 |
2008年 | 8932篇 |
2007年 | 8785篇 |
2006年 | 7828篇 |
2005年 | 6955篇 |
2004年 | 6467篇 |
2003年 | 5817篇 |
2002年 | 5960篇 |
2001年 | 6142篇 |
2000年 | 4595篇 |
1999年 | 3456篇 |
1998年 | 2923篇 |
1997年 | 2929篇 |
1996年 | 2711篇 |
1995年 | 2327篇 |
1994年 | 2437篇 |
1993年 | 2315篇 |
1992年 | 2601篇 |
1991年 | 2718篇 |
1990年 | 2613篇 |
1989年 | 2681篇 |
1988年 | 2594篇 |
1987年 | 2591篇 |
1986年 | 2446篇 |
1985年 | 3087篇 |
1984年 | 3147篇 |
1983年 | 2633篇 |
1982年 | 2616篇 |
1981年 | 2574篇 |
1980年 | 2395篇 |
1979年 | 2756篇 |
1978年 | 2734篇 |
1977年 | 2911篇 |
1976年 | 2903篇 |
1975年 | 2709篇 |
1974年 | 2641篇 |
1973年 | 2738篇 |
1972年 | 2107篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Yuanbo Gao Tingting Yang Xueli Wang Jizong Chen Yong He 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1610-1623
Two series of novel alternating copolyoxamides (PAnT-alt-n2 and PAn2-alt-62) are synthesized via solution/solid-state polycondensation (SSP). The alternating structures are analyzed carefully with 1H NMR and 13C NMR spectra. The melting behaviors, thermal stabilities, crystal structures and crystallinities are systematically evaluated by DSC, TGA and WAXD. The results reveal that these alternating copolyoxamides possess almost perfect alternating chain structures and have high melting temperature (Tm > 270 °C), high crystallinity (Xc > 32%) and high decomposition temperature (T5 > 405 °C) as well as low saturated water absorption (<3.5 wt%), which suggests that they have high potential as engineering plastic of high heat resistant. 相似文献
2.
JETP Letters - A new approach to search for axions in the storage ring experiments, applicable at a short coherence time of the in-plane polarization as is the case for protons is discussed. The... 相似文献
3.
Qianqian Fan Zirui Liu Feng Qiu Prof. Yong Mao Prof. Qingju Liu Prof. Longzhou Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202202700
The artificially accurate design of nonmetal electrocatalysts’ active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom. 相似文献
4.
Gaineev A. M. Galkina I. V. Davletshin R. R. Davletshina N. V. Kuznetsov N. O. Grishaev D. Yu. Shulayeva M. P. Pozdeev O. K. 《Russian Journal of General Chemistry》2022,92(7):1208-1213
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a... 相似文献
5.
Mamatkulova N. M. Mukarramov N. I. Sasmakov S. A. Khidirova N. K. 《Chemistry of Natural Compounds》2022,58(4):726-727
Chemistry of Natural Compounds - 相似文献
6.
Petrov P. A. Filippova E. A. Kompankov N. B. Sukhikh T. S. Sokolov M. N. 《Journal of Structural Chemistry》2022,63(3):470-475
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the... 相似文献
7.
Russian Chemical Bulletin - New representatives of (O-Si)-chelate compounds, N-(fluorosilyl)methyl derivatives of N-methylacetamide, N-methylbenzamide, N-phenylacetamide, and N-phenylbenzamide,... 相似文献
8.
Russian Journal of General Chemistry - A mechanochemical method was developed for the synthesis of ferromagnetic Pd–Fe–Co–Ni composites based on the natural biopolymer chitosan,... 相似文献
9.
Yuki Shintani Taku Ohtomi Dr. Aya Shibata Dr. Yoshiaki Kitamura Koichiro M. Hirosawa Prof. Kenichi G. N. Suzuki Prof. Masato Ikeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(8):e202104421
Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging. 相似文献
10.
Journal of Structural Chemistry - Atomic and electronic structures of cyclic organosilicon compound 9,9,10,10-tetraethynyl-9,10-dihydrodisilaanthracene are studied by the density functional theory.... 相似文献