全文获取类型
收费全文 | 264037篇 |
免费 | 4756篇 |
国内免费 | 1351篇 |
专业分类
化学 | 149804篇 |
晶体学 | 2959篇 |
力学 | 10202篇 |
综合类 | 47篇 |
数学 | 31037篇 |
物理学 | 76095篇 |
出版年
2021年 | 2347篇 |
2020年 | 2849篇 |
2019年 | 3072篇 |
2018年 | 4337篇 |
2017年 | 4063篇 |
2016年 | 5964篇 |
2015年 | 3955篇 |
2014年 | 5478篇 |
2013年 | 12427篇 |
2012年 | 10517篇 |
2011年 | 12161篇 |
2010年 | 8362篇 |
2009年 | 7869篇 |
2008年 | 11287篇 |
2007年 | 11286篇 |
2006年 | 10390篇 |
2005年 | 9595篇 |
2004年 | 8432篇 |
2003年 | 7448篇 |
2002年 | 7113篇 |
2001年 | 6831篇 |
2000年 | 5467篇 |
1999年 | 4077篇 |
1998年 | 3478篇 |
1997年 | 3427篇 |
1996年 | 3176篇 |
1995年 | 2619篇 |
1994年 | 2753篇 |
1993年 | 2797篇 |
1992年 | 2948篇 |
1991年 | 2959篇 |
1990年 | 2823篇 |
1989年 | 2795篇 |
1988年 | 2676篇 |
1987年 | 2665篇 |
1986年 | 2531篇 |
1985年 | 3354篇 |
1984年 | 3476篇 |
1983年 | 2730篇 |
1982年 | 3082篇 |
1981年 | 2957篇 |
1980年 | 2728篇 |
1979年 | 2925篇 |
1978年 | 3019篇 |
1977年 | 3014篇 |
1976年 | 3032篇 |
1975年 | 2869篇 |
1974年 | 2860篇 |
1973年 | 3005篇 |
1972年 | 1938篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
41.
42.
Nasirizadeh Navid Dehghani Mohammad Yazdanshenas Mohammad E. 《Journal of Sol-Gel Science and Technology》2015,73(1):14-21
Journal of Sol-Gel Science and Technology - In this paper, a simple method is presented for making a conductive and hydrophobic cotton fabric using a multi-walled carbon nanotube (MWCNT). The... 相似文献
43.
Triesterase and Promiscuous Diesterase Activities of a Di‐CoII‐Containing Organophosphate Degrading Enzyme Reaction Mechanisms 下载免费PDF全文
Dr. Marta E. Alberto Gaspar Pinto Prof. Nino Russo Dr. Marirosa Toscano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3736-3745
The reaction mechanism for the hydrolysis of trimethyl phosphate and of the obtained phosphodiester by the di‐CoII derivative of organophosphate degrading enzyme from Agrobacterium radiobacter P230(OpdA), have been investigated at density functional level of theory in the framework of the cluster model approach. Both mechanisms proceed by a multistep sequence and each catalytic cycle begins with the nucleophilic attack by a metal‐bound hydroxide on the phosphorus atom of the substrate, leading to the cleavage of the phosphate‐ester bond. Four exchange‐correlation functionals were used to derive the potential energy profiles in protein environments. Although the enzyme is confirmed to work better as triesterase, as revealed by the barrier heights in the rate‐limiting steps of the catalytic processes, its promiscuous ability to hydrolyze also the product of the reaction has been confirmed. The important role played by water molecules and some residues in the outer coordination sphere has been elucidated, while the binuclear CoII center accomplishes both structural and catalytic functions. To correctly describe the electronic configuration of the d shell of the metal ions, high‐ and low‐spin arrangement jointly with the occurrence of antiferromagnetic coupling, have been herein considered. 相似文献
44.
Pd0‐Catalyzed Intramolecular α‐Arylation of Sulfones: Domino Reactions in the Synthesis of Functionalized Tetrahydroisoquinolines 下载免费PDF全文
Prof.Dr. Daniel Solé Ferran Pérez‐Janer Dr. Raffaella Mancuso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4580-4584
A new strategy for the synthesis of tetrahydroisoquinolines based on the Pd0‐catalyzed intramolecular α‐arylation of sulfones is reported. The combination of this Pd‐catalyzed reaction with intermolecular Michael and aza‐Michael reactions allows the development of two‐ and three‐step domino processes to synthesize diversely functionalized scaffolds from readily available starting materials. 相似文献
45.
46.
47.
Yi Han Zibo Xue Dr. Guangwu Li Dr. Yanwei Gu Dr. Yong Ni Dr. Shaoqiang Dong Prof. Chunyan Chi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9111-9116
Incorporation of a non-hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene-bridged double [6]helicene and heptagon-containing nanographene by the Scholl reaction, an unexpected azulene-embedded nanographene and its triflyloxylated product were obtained, as confirmed by X-ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring-fused substructure containing two formal azulene units is formed, but only one of them shows an azulene-like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2-phenyl migration and a naphthalene to azulene rearrangement reaction according to an in-silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene-based molecular materials. 相似文献
48.
V. A. Bespalov V. M. Glazov E. A. Il’ichev Yu. A. Klimov S. V. Kuklev A. E. Kuleshov R. M. Nabiev G. N. Petrukhin B. G. Potapov G. S. Rychkov D. S. Sokolov V. V. Fandeev E. A. Fetisov S. S. Yakushov 《Technical Physics》2015,60(4):553-560
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied. 相似文献
49.
50.