全文获取类型
收费全文 | 1974篇 |
免费 | 55篇 |
国内免费 | 9篇 |
专业分类
化学 | 1409篇 |
晶体学 | 20篇 |
力学 | 61篇 |
数学 | 103篇 |
物理学 | 445篇 |
出版年
2022年 | 10篇 |
2021年 | 23篇 |
2020年 | 13篇 |
2019年 | 25篇 |
2018年 | 21篇 |
2017年 | 14篇 |
2016年 | 32篇 |
2015年 | 25篇 |
2014年 | 43篇 |
2013年 | 105篇 |
2012年 | 102篇 |
2011年 | 101篇 |
2010年 | 64篇 |
2009年 | 50篇 |
2008年 | 86篇 |
2007年 | 97篇 |
2006年 | 91篇 |
2005年 | 97篇 |
2004年 | 107篇 |
2003年 | 85篇 |
2002年 | 87篇 |
2001年 | 41篇 |
2000年 | 40篇 |
1999年 | 30篇 |
1998年 | 19篇 |
1997年 | 25篇 |
1996年 | 36篇 |
1995年 | 25篇 |
1994年 | 30篇 |
1993年 | 33篇 |
1992年 | 35篇 |
1991年 | 30篇 |
1990年 | 21篇 |
1989年 | 20篇 |
1988年 | 33篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 28篇 |
1984年 | 44篇 |
1983年 | 20篇 |
1982年 | 34篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 16篇 |
1976年 | 11篇 |
1974年 | 12篇 |
1973年 | 9篇 |
1970年 | 9篇 |
排序方式: 共有2038条查询结果,搜索用时 31 毫秒
101.
102.
103.
Room temperature chiral spiro ionic liquids 1 and 2 based on 1,2,3-triazolium salts, were synthesized via an intramolecular double Huisgen reaction. The preparation of the enantiomerically pure spiro triazolium salts was achieved by resolution by HPLC using a chiral stationary phase column and subsequent N-dialkylations of spiro triazoles 6 and 10. 相似文献
104.
Akihiko Ishii Masashi Saitoh Tetsuhiko Kawai Masami Murata Juzo Nakayama 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8-9):2025-2026
The reaction of isolable dithiirane 1-oxides with (Ph 3 P) 2 Pt( m 2 -C 2 H 4 ) provided the title complexes in high yields. 31 P NMR spectroscopy of the phosphine ligands of the complexes and x-ray crystallographic analysis of a complex were reported. 相似文献
105.
Cellulosic biomass is a promising alternative energy resource from the viewpoint of sustainability. The use of waste materials as cellulosic biomass could additionally contribute to a recycling society. It is thus essential to develop safer processes in order to expand utilization of cellulosic biomass as a useful resource in the future. For example, in some cases, construction wastes contain wood preservatives, including metal oxides that can act as catalysts for the oxidation of organic materials. Copper(II) oxide (CuO) is a major component in wood preservatives and is known to catalyze the oxidation of cellulose. There is, therefore, possibility for spontaneous ignition within large piles of wood chips from construction wastes. In this study, we focused on the thermal behavior of a cellulose/CuO mixture, measured using a Calvet-type heat flux calorimeter. In addition, Fourier transform infrared spectroscopy and gas chromatography were applied to analyze the oxidative decomposition gases of the cellulose/CuO mixture, and a reaction mechanism was proposed. It was revealed that CuO promotes the oxidative decomposition of cellulose and increases the quantity of the gases that evolved from cellulose with a catalytic cycle. The influence of CuO on oxidation of cellulose is greater at lower temperatures and spontaneous ignition, fires, and explosions are likely to increase when wood chips containing CuO are stored for long periods of time. 相似文献
106.
Shuichi Hirata Kouichi Tanaka Katsuya Matsui Fernando Arteaga Arteaga Yasushi Yoshida Shinobu Takizawa Hiroaki Sasai 《Tetrahedron: Asymmetry》2013,24(19):1189-1192
The introduction of a 1,3-propanediamine unit at the 3-position of (S)-BINOL using a methylene spacer led to the formation of a chiral bifunctional organocatalyst for the aza-Morita–Baylis–Hillman (aza-MBH) reaction. The organocatalyst 1k mediated aza-MBH transformations with high chemical yields and with up to 82% ee. 相似文献
107.
108.
109.
110.