全文获取类型
收费全文 | 5418篇 |
免费 | 159篇 |
国内免费 | 14篇 |
专业分类
化学 | 3968篇 |
晶体学 | 73篇 |
力学 | 57篇 |
综合类 | 2篇 |
数学 | 243篇 |
物理学 | 1248篇 |
出版年
2023年 | 35篇 |
2022年 | 46篇 |
2021年 | 45篇 |
2020年 | 76篇 |
2019年 | 92篇 |
2018年 | 63篇 |
2017年 | 35篇 |
2016年 | 113篇 |
2015年 | 126篇 |
2014年 | 100篇 |
2013年 | 269篇 |
2012年 | 254篇 |
2011年 | 274篇 |
2010年 | 168篇 |
2009年 | 192篇 |
2008年 | 279篇 |
2007年 | 301篇 |
2006年 | 283篇 |
2005年 | 295篇 |
2004年 | 233篇 |
2003年 | 210篇 |
2002年 | 206篇 |
2001年 | 124篇 |
2000年 | 121篇 |
1999年 | 80篇 |
1998年 | 61篇 |
1997年 | 43篇 |
1996年 | 84篇 |
1995年 | 62篇 |
1994年 | 52篇 |
1993年 | 71篇 |
1992年 | 69篇 |
1991年 | 72篇 |
1990年 | 57篇 |
1989年 | 55篇 |
1988年 | 60篇 |
1987年 | 63篇 |
1986年 | 52篇 |
1985年 | 92篇 |
1984年 | 83篇 |
1983年 | 47篇 |
1982年 | 65篇 |
1981年 | 59篇 |
1980年 | 58篇 |
1979年 | 59篇 |
1978年 | 50篇 |
1977年 | 36篇 |
1976年 | 39篇 |
1974年 | 29篇 |
1973年 | 30篇 |
排序方式: 共有5591条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
995.
Kenji Ogino Aiko Kanegae Ryoji Yamaguchi Hisaya Sato Jan Kurjata 《Macromolecular rapid communications》1999,20(3):103-106
4‐Methyltriphenylamine was oxidatively polymerized in chloroform (CL) or propylene carbonate (PC) in the presence of ferric chloride (FeCl3) at 50°C. Polymerization proceeded more rapidly and the molecular weight of the resulting polymer was higher in CL than in PC due to the higher oxidation potential of the solution. The linear structure was confirmed by 13C NMR, and the resulting polymer exhibited high thermal stability and electrochemical activity. 相似文献
996.
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
997.
Effects of polyethylene spacer length in polymeric electrolytes on gelation of ionic liquids and ionogel properties 下载免费PDF全文
Jun'ichi Nagasawa Sonoko Wakahara Hajime Matsumoto Hideyuki Kihara Masaru Yoshida 《Journal of polymer science. Part A, Polymer chemistry》2015,53(2):249-255
Polymer electrolytes containing N,N′-(trans-cyclohexane-1,4-diyl)dibenzamide linkages, polyethylene ((CH2)m, m = 2, 4, 10) spacers, and bis(trifluoromethanesulfonyl)amide (TFSA) or bis(fluorosulfonyl)amide (FSA) counteranions (polymer abbreviation: CDBAm•X; m = 2, 4, 10; X = TFSA, FSA) have been synthesized, adding to our previous report (m = 6). In addition, their ability to effect the gelation of six ionic liquids and the properties of the resulting ionogels have been examined. The polymers, except for CDBA10•TFSA, effect the gelation for all ionic liquids used in this study at fairly low concentrations (0.9–50 g/L). Ionogel ionic conductivity is not dependent on the spacer length, but does decrease slightly as increasing amounts of the gelatinizer are introduced. In contrast to ionic conductivity, the temperatures at which these ionogels transition into isotropic fluids is dependent on the spacer length; the gel composed of [EMI][FSA] and 100 g/L of CDBA6•FSA transforms at 120 °C, while the gel composed of [EMI][FSA] and 5 g/L of CDBA2•FSA does not transform into a sol even when temperatures become 155 °C. In brief, ionogel heat resistance can be improved by changing the spacer length of the polyelectrolyte. Finally, it has been determined using cyclic voltammetry that the potential window of the polyelectrolytes is particularly wide, ranging from −1.6 to 2.5 V. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 249–255 相似文献
998.
999.
1000.