全文获取类型
收费全文 | 2993篇 |
免费 | 94篇 |
国内免费 | 20篇 |
专业分类
化学 | 2307篇 |
晶体学 | 51篇 |
力学 | 45篇 |
数学 | 251篇 |
物理学 | 453篇 |
出版年
2023年 | 15篇 |
2021年 | 19篇 |
2020年 | 38篇 |
2019年 | 56篇 |
2018年 | 34篇 |
2017年 | 34篇 |
2016年 | 64篇 |
2015年 | 68篇 |
2014年 | 78篇 |
2013年 | 184篇 |
2012年 | 197篇 |
2011年 | 204篇 |
2010年 | 101篇 |
2009年 | 133篇 |
2008年 | 194篇 |
2007年 | 185篇 |
2006年 | 179篇 |
2005年 | 172篇 |
2004年 | 183篇 |
2003年 | 159篇 |
2002年 | 113篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 36篇 |
1997年 | 32篇 |
1996年 | 33篇 |
1995年 | 24篇 |
1994年 | 11篇 |
1993年 | 16篇 |
1992年 | 22篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1987年 | 26篇 |
1986年 | 12篇 |
1985年 | 32篇 |
1984年 | 23篇 |
1983年 | 23篇 |
1982年 | 24篇 |
1981年 | 22篇 |
1980年 | 32篇 |
1979年 | 20篇 |
1978年 | 21篇 |
1977年 | 16篇 |
1976年 | 19篇 |
1975年 | 14篇 |
1974年 | 11篇 |
1973年 | 15篇 |
排序方式: 共有3107条查询结果,搜索用时 156 毫秒
1.
2.
3.
Nickel‐Promoted Highly Regioselective Carboxylation of Aryl Ynol Ether and Its Application to the Synthesis of Chiral β‐Aryloxypropionic Acid Derivatives 下载免费PDF全文
Nickel(0)‐promoted carboxylation of aryl ynol ether proceeded in a highly regioselective manner to produce α‐substituted‐β‐aryloxyacrylic acid derivatives. The α‐substituted‐β‐aryloxyacrylic acids were transformed into the corresponding β‐aryloxypropionic acid derivative as an optically active form via rhodium‐catalyzed asymmetric hydrogenation. 相似文献
4.
5.
Dr. Hiromi Oshita Takashi Suzuki Kyohei Kawashima Prof. Dr. Hitoshi Abe Prof. Dr. Fumito Tani Prof. Dr. Seiji Mori Prof. Dr. Tatsuo Yajima Prof. Dr. Yuichi Shimazaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(32):7649-7658
In order to gain new insights into the effect of the π–π stacking interaction of the indole ring with the CuII–phenoxyl radical as seen in the active form of galactose oxidase, we have prepared a CuII complex of a methoxy-substituted salen-type ligand, containing a pendent indole ring on the dinitrogen chelate backbone, and characterized its one-electron-oxidized forms. The X-ray crystal structures of the oxidized CuII complex exhibited the π–π stacking interaction of the indole ring mainly with one of the two phenolate moieties. The phenolate moiety in close contact with the indole moiety showed the characteristic phenoxyl radical structural features, indicating that the indole ring favors the π–π stacking interaction with the phenoxyl radical. The UV/Vis/NIR spectra of the oxidized CuII complex with the pendent indole ring was significantly different from those of the complex without the side-chain indole ring, and the absorption and CD spectra exhibited a solvent dependence, which is in line with the phenoxyl radical–indole stacking interaction in solution. The other physicochemical results and theoretical calculations strongly support that the indole ring, as an electron donor, stabilizes the phenoxyl radical by the π–π stacking interaction. 相似文献
6.
7.
Kyoungmin Kang Kosuke Sakamoto Dr. Yoshihiro Nishimoto Prof. Dr. Makoto Yasuda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):4930-4934
The regioselective anti-carboindation of ynamides by using InBr3 and silylated nucleophiles was developed to synthesize (Z)-β-(carbonylamino)alkenylindiums. The X-ray crystallographic analysis of an alkenylindium suggested that the reaction proceeded in an anti-addition fashion. In contrast to reported syn-carbometalations of ynamides by using organometallics, a cooperation of InBr3 and silylated nucleophiles to ynamides achieved an anti-addition, which was supported by DFT calculations. The scope of substrates included various ynamides and silylated nucleophiles, such as silyl ketene acetals and silyl ketene imines. The transformation of synthesized alkenylindiums by iodination, radical coupling, and Pd-catalyzed cross-coupling successfully afforded trisubstituted enamines with high regio- and stereoselectivities. 相似文献
8.
9.
Yuanlin Li Tianfang Zheng Yanxiang Liu Prof. Georgiy G. Levchenko Prof. Wei Han Prof. Aleksey V. Pashchenko Prof. Shin-ichi Sasaki Prof. Hitoshi Tamiaki Prof. Xiao-Feng Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(56):e202201855
Hydrogen energy is an abundant, clean, sustainable and environmentally friendly renewable energy source. Therefore, the production of hydrogen by photocatalytically splitting water on semiconductors has been considered in recent years as a promising and sustainable strategy for converting solar energy into chemical energy to replace conventional energy sources and to solve the growing problem of environmental pollution and the global energy crisis. However, highly efficient solar-driven photocatalytic hydrogen production remains a huge challenge due to the poor visible light response of available photocatalytic materials and the low efficiency of separation and transfer of photogenerated electron-hole pairs. In the present work, organic heterojunction structures based on bacteriochlorophyll (BChl) and chlorophyll (Chl) molecules were introduced and used for solar-driven photocatalytic hydrogen production from water under visible light. Also, noble metal-free photocatalyst was successfully constructed on Ti3C2Tx nanosheets by simple successive deposition of Chl and BChl, which was used for the photocatalytic splitting water to hydrogen evolution reaction (HER). The results show that the optimal BChl@Chl@Ti3C2Tx composite has a high HER performance with 114 μmol/h/gcat, which is much higher than the BChl@Ti3C2Tx and Chl@Ti3C2Tx composites. 相似文献
10.
Dr. Ryohei Doi Akimasa Yabuta Prof. Dr. Yoshihiro Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(23):5884-5888
Palladium-catalyzed decarboxylative alkynylation of α-acyloxyketones triggered by C(sp3)−O bond cleavage is disclosed. The decarboxylation strategy featuring a neutral reaction condition enabled an unprecedent catalytic alkynylation of a ketone enolate. The reaction was applied to a variety of substrates, giving desired products in good yields. We successfully obtained X-ray crystallography of a new palladium–enolate intermediate that was synthesized by a reaction of [Pd(cod)(CH2TMS)2] with XPhos and α-acyloxyketone at room temperature, indicating facile C(sp3)−O bond disconnection. 相似文献