全文获取类型
收费全文 | 2325篇 |
免费 | 124篇 |
国内免费 | 5篇 |
专业分类
化学 | 1568篇 |
晶体学 | 3篇 |
力学 | 49篇 |
数学 | 433篇 |
物理学 | 401篇 |
出版年
2023年 | 15篇 |
2022年 | 17篇 |
2021年 | 31篇 |
2020年 | 35篇 |
2019年 | 37篇 |
2018年 | 44篇 |
2017年 | 31篇 |
2016年 | 106篇 |
2015年 | 83篇 |
2014年 | 86篇 |
2013年 | 150篇 |
2012年 | 154篇 |
2011年 | 181篇 |
2010年 | 114篇 |
2009年 | 86篇 |
2008年 | 125篇 |
2007年 | 135篇 |
2006年 | 129篇 |
2005年 | 103篇 |
2004年 | 87篇 |
2003年 | 71篇 |
2002年 | 75篇 |
2001年 | 47篇 |
2000年 | 35篇 |
1999年 | 19篇 |
1998年 | 21篇 |
1997年 | 27篇 |
1996年 | 30篇 |
1995年 | 25篇 |
1994年 | 20篇 |
1993年 | 18篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 25篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1934年 | 11篇 |
排序方式: 共有2454条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
36.
37.
38.
A simple analytical procedure has been developed for the determination of indican and tryptophan in biological fluids by reversed-phase liquid chromatography using a new electrochemical detector consisting of a tubular anode obtained by moulding graphitized carbon black and polyethylene. The hydrodynamic voltammetry of these compounds has been carried out and it has been found that, by operating in isocratic conditions with phosphate buffer (pH 4.0)-methanol (93:7), the reported compounds can be determined directly. The procedure can be applied for the determination of the free compounds on ultrafiltered serum as well as of their total content on serum deproteinized with methanol. Levels of both compounds in normal and uraemic patients have been measured and the relative ratios between free and total content yield a useful marker for patients with renal disease. The limits of quantitation of indican and tryptophan in serum were 5 and 10 ng/ml, respectively. The within-day assay coefficient of variation for total indican and tryptophan ranged from 3.0 to 3.6% and from 3.8 to 4.1%, respectively. The day-to-day assay coefficient of variation for total indican and tryptophan ranged from 3.4 to 3.7% and from 4.6 to 5.0%, respectively. 相似文献
39.
40.
Klein E Nghiêm HO Valleix A Mioskowski C Lebeau L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(20):4649-4655
Thiamine (vitamin B1) is an essential nutritional factor metabolized inside the body in its mono-, di-, and triphosphate forms. Although the action of thiamine and thiamine diphosphate have been intensely investigated, many questions remain unanswered and the role of thiamine triphosphate is still especially unknown. To probe recent hypotheses on the implication of thiamine triphosphate in a new phosphorylation pathway involving synaptic proteins, we synthesized a series of thiamine di- and triphosphate analogues that are resistant to both enzymatic and chemical hydrolyses. The key step in the preparation of the title compounds is the coupling of thiamine propyl disulfide with adequately protected methylenebis-phosphonic acid, the corresponding triphosphate analogue, and difluoromethylenebisphosphonic acid. 相似文献