全文获取类型
收费全文 | 224篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 198篇 |
数学 | 13篇 |
物理学 | 17篇 |
出版年
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 6篇 |
2008年 | 15篇 |
2007年 | 10篇 |
2006年 | 18篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有228条查询结果,搜索用时 31 毫秒
41.
Toyohide Takeuchi Tomoo Miwa Rongzong Hu Jianhua Chu 《Journal of separation science》1995,18(12):745-748
The retention behavior of aromatic hydrocarbons and dansylamino acids on cation-exchangers modified with alkylammonium ions has been examined by microcolumn liquid chromatography. Several parameters affected the retention of analytes, involving concentration of the modifier in the mobile phase, its alkyl chain length and mobile phase composition. Stationary phases modified with a reagent having longer alkyl chains achieved better column efficiency. 相似文献
42.
43.
44.
45.
46.
47.
Hosoe T Itabashi T Kobayashi N Udagawa S Kawai K 《Chemical & pharmaceutical bulletin》2006,54(2):185-187
Three new type indoloditerpenes, emindoles PA (1), PB (2), and PC (3), were isolated from the mycelium of Emericella purpurea along with the sesterterpenes variecolol and variecolactone, and the dicyanide derivatives epurpurins A to C. The structures of 1-3 were confirmed by the spectroscopic investigation. The structure of emindoles PA (1) was revised from our preliminary report. Emindoles PA (1), PB (2), and PC (3) are the indoloditerpenes having a new type of carbon skeleton. 相似文献
48.
Motokura K Nakagiri N Mori K Mizugaki T Ebitani K Jitsukawa K Kaneda K 《Organic letters》2006,8(20):4617-4620
Nucleophilic addition of sulfonamides and carboxamides to simple alkenes proceeded smoothly using a proton-exchanged montmorillonite catalyst. The spent catalyst was recovered easily from the reaction mixture and was reusable at least five times without any loss of activity. The unique acidity of the proton-exchanged montmorillonite (H-mont) catalyst was found to be applicable to additional reactions: substitution of hydroxyl groups of alcohols with amides and anilines. 相似文献
49.
The concave spherically annular transducer is regarded as a negative and a positive concave spherical transducer, and the spheroidal beam equation is used to simulate the linear and nonlinear sound field in a tissue medium generated by this transducer. It is found that the acoustic focus of the ring does not coincide with the acoustic focus of its central part. If the width of the ring increases, its acoustic focus will move toward the geometric focus and the amplitudes of nonlinear harmonics will increase obviously. If there are several coaxial rings placed on the concave spherical surface, more than one peak will appear along the axial direction for the fundamental, and high harmonics focus better. The distribution of sound field will change with the number and the excited signals of rings, so it maybe is a potential approach to treat locally big tumors. 相似文献