全文获取类型
收费全文 | 255篇 |
免费 | 30篇 |
专业分类
化学 | 216篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 42篇 |
物理学 | 22篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 12篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 13篇 |
2013年 | 17篇 |
2012年 | 20篇 |
2011年 | 18篇 |
2010年 | 14篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 13篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有285条查询结果,搜索用时 15 毫秒
11.
Chung‐Cheng Chang Kuo‐Ching Yang Jeng‐Gong Guo Leigh‐May Huang Li‐Chyung Wang Gene‐Hsiang Lee Shie‐Ming Peng 《中国化学会会志》2003,50(5):965-971
The insertion reaction of CS2 with Mg(NR2)2 (R= Et, iPr), MgR′2 (R′= Et, Ph) and R″MgBr (R″= iPr, Ph) respectively lead solid products, Mg(S2CNR2)2(THF)n ( 1 : R= Et, n=2; 2 : R= iPr, n=1), Mg(S2C′R)2(THF)2 ( 3 : ′R= Et, 4 : ′R= Ph), BrMg(S2C″R) (THF)3 ( 5 : ″R= iPr, 6 : ″R= Ph) in which the inserted carbon disulfides act as terminal chelating ligands. These compounds were characterized with 1H, 13C NMR, IR spectroscopy, mass spectrometry, elemental analyses, and X‐ray crystallography. 相似文献
12.
13.
Sulfur‐substituted 4‐quinolizidinones, previously prepared by aza‐Diels‐Alder reactions and ring‐closing metathesis, are now subjected to further synthetic transformations. Formal synthesis of cermizine C and 5‐epi‐cermizine C, and some other useful reactions have been achieved. 相似文献
14.
Jayachandran Jayakumar Kanniyappan Parthasarathy Yi‐Hsiang Chen Tai‐Hua Lee Shih‐Ching Chuang Chien‐Hong Cheng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(37):10047-10050
A new method for the synthesis of highly substituted naphthyridine‐based polyheteroaromatic compounds in high yields proceeds through rhodium(III)‐catalyzed multiple C H bond cleavage and C C and C N bond formation in a one‐pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π‐conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation‐assisted ortho C H activation, alkyne insertion, and reductive elimination, is proposed for this transformation. 相似文献
15.
16.
By employing the technique of asynchronous mode locking, we have successfully demonstrated direct generation of stable 10 GHz 816 fs pulse trains with a supermode-suppression ratio >70 dB from a hybrid mode-locked Er-fiber laser. When the modulation frequency deviates from the cavity harmonic frequency by 15-40 kHz, stable femtosecond soliton pulses are formed. Our results demonstrate that asynchronous mode locking can act as an effective mechanism for achieving a shorter pulse width and for stabilizing high-repetition-rate pulse trains in soliton fiber lasers. 相似文献
17.
Quantitative enantiomeric analysis of chlorcyclizine,hydroxyzine, and meclizine by capillary electrophoresis 总被引:1,自引:0,他引:1
A simple capillary zone electrophoresis method was developed for the quantitative enantiomeric analysis of piperazine antihistamines with teratogenic suspicion in animals. Enantioseparation of chlorcyclizine, hydroxyzine, and meclizine was performed in glycine buffer (0.6 mol L-1; pH 3.00) with sulfated -cyclodextrin (5 mg mL-1) as a chiral selector; and the separated drugs were monitored by ultra-violet detector. The lower quantitation of the individual enantiomer is attainable at 10 µmol L-1, using an achiral piperazine drug (cyclizine) as internal standard. The method is simple and rapid with a short run time (<5 min) for the analysis of chlorcyclizine, hydroxyzine or meclizine enantiomers. 相似文献
18.
In this study, an improved process for the synthesis of etorphine and dihydroetorphine from codeine with an overall yield of 2.7% and 1.5% respectively is described. The structure of 19‐propylthevinol 7 was verfied by X‐ray structure analysis. This result is promising for synthesizing various morphine‐based drugs. 相似文献
19.
JavaStatSoft, implemented using Java, is an open-source software for performing statistics. The current features of JavaStatSoft
are described. Several well-known patterns the software used are introduced. In addition, based on these patterns and the
experience in developing the software, a new framework, referred to as Data Analysis Module, is proposed to help programmers
develop a user-friendly software for data analysis. 相似文献
20.