全文获取类型
收费全文 | 1224篇 |
免费 | 69篇 |
国内免费 | 6篇 |
专业分类
化学 | 754篇 |
晶体学 | 23篇 |
力学 | 35篇 |
综合类 | 3篇 |
数学 | 270篇 |
物理学 | 214篇 |
出版年
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 19篇 |
2020年 | 35篇 |
2019年 | 34篇 |
2018年 | 41篇 |
2017年 | 36篇 |
2016年 | 70篇 |
2015年 | 49篇 |
2014年 | 91篇 |
2013年 | 198篇 |
2012年 | 64篇 |
2011年 | 51篇 |
2010年 | 64篇 |
2009年 | 48篇 |
2008年 | 61篇 |
2007年 | 46篇 |
2006年 | 27篇 |
2005年 | 17篇 |
2004年 | 15篇 |
2003年 | 20篇 |
2002年 | 23篇 |
2001年 | 17篇 |
2000年 | 16篇 |
1999年 | 15篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1967年 | 3篇 |
1938年 | 3篇 |
排序方式: 共有1299条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
Dr. Martin Pichette Drapeau Prof. Dr. Lukas J. Gooßen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18654-18677
The selective transformation of C?H bonds is one of the most desirable approaches to creating complexity from simple building blocks. Several directing groups are efficient in controlling the regioselectivity of catalytic C?H bond functionalizations. Among them, carboxylic acids are particularly advantageous, since they are widely available in great structural diversity and at low cost. The carboxylate directing groups can be tracelessly cleaved or may serve as the anchor point for further functionalization through decarboxylative couplings. This Minireview summarizes the substantial progress made in the last few years in the development of reactions in which carboxylate groups direct C?H bond functionalizations with formation of C?C, C?O, C?N, or C?halogen bonds at specific positions. It is divided into sections on C?C, C?O, C?N, and C?halogen bond formation, each of which is subdivided by reactions and product classes. Particular emphasis is placed on methods that enable multiple derivatizations by combining carboxylate‐directed C?H functionalization with decarboxylative couplings. 相似文献
36.
Vinzenz Thönnißen Prof. Dr. Frederic W. Patureau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(25):7189-7192
The atroposelective formation of C−N bonds has recently emerged within the field of amination reactions. On first sight, it may seem quite surprising that such an ancient class of organic coupling reactions (Gabriel, Ullmann, Goldberg, Buchwald, Hartwig and many others) has so few enantioselective solutions, and this in spite of asymmetric synthesis being now a mature concept and field. Why should enantioselective C−N bond formation be so difficult? This question and some of the first examples that promise an imminent change of paradigm are herein discussed. 相似文献
37.
F.A. Mikailov E. Başaran E. Şentürk L. Tümbek T.G. Mammadov V.P. Aliev 《Phase Transitions》2013,86(12):1057-1064
The results of measurements of the dielectric constant of TlGaSe2 in temperature range of successive phase transitions are presented. An anomaly in the temperature dependence of the real part of dielectric constant in TlGaSe2 has been observed at about 242?K in addition to anomalies at 115, 108, and also near 65?K as reported in previous publications. The presence of temperature hysteresis effects in temperature interval between 115 and 242?K allowed making a conclusion about possible existence of an incommensurate phase in the mentioned temperature range. A model of succession of the structural phase transitions in TlGaSe2 has been suggested. 相似文献
38.
Nader Noroozi Pesyan Alireza Shokr Mohammad Behroozi Ertan Şahin 《Journal of the Iranian Chemical Society》2013,10(3):565-575
Reaction of 5,5-dimethylcyclohexane-1,3-dione (dimedone), aldehydes and cyanogen bromide in the presence of triethylamine leads to the selective formation of spiro dihydrofurans in moderate to good yields at room temperature. 相似文献
39.
The aim of this paper is to establish some stability results involving generalized divided differences. 相似文献
40.
Piano‐stool ([(p‐cymene)Ru(thz)Cl], 2 ) and six‐coordinated ([Ru(thz)2(PPh3)2], 3 ) ruthenium complexes derived from 2‐phenylthiazoline‐4‐carboxylic acid (Hthz, 1 ) were synthesized for the first time, and fully characterized using conventional methods. Also, the molecular structure of complex 3 was determined using X‐ray analysis. These complexes were evaluated as catalysts for transfer hydrogenation of carbonyl compounds in the presence of isopropyl alcohol and KOtBu. Complex 2 was found to be more active than 3 in transfer hydrogenation. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献