全文获取类型
收费全文 | 6890篇 |
免费 | 237篇 |
国内免费 | 14篇 |
专业分类
化学 | 4997篇 |
晶体学 | 59篇 |
力学 | 81篇 |
数学 | 690篇 |
物理学 | 1314篇 |
出版年
2023年 | 32篇 |
2021年 | 68篇 |
2020年 | 89篇 |
2019年 | 89篇 |
2018年 | 50篇 |
2017年 | 48篇 |
2016年 | 133篇 |
2015年 | 144篇 |
2014年 | 163篇 |
2013年 | 258篇 |
2012年 | 330篇 |
2011年 | 407篇 |
2010年 | 221篇 |
2009年 | 181篇 |
2008年 | 353篇 |
2007年 | 336篇 |
2006年 | 337篇 |
2005年 | 334篇 |
2004年 | 297篇 |
2003年 | 258篇 |
2002年 | 236篇 |
2001年 | 149篇 |
2000年 | 138篇 |
1999年 | 84篇 |
1998年 | 62篇 |
1997年 | 62篇 |
1996年 | 113篇 |
1995年 | 75篇 |
1994年 | 89篇 |
1993年 | 79篇 |
1992年 | 79篇 |
1991年 | 68篇 |
1990年 | 60篇 |
1989年 | 48篇 |
1988年 | 55篇 |
1987年 | 70篇 |
1986年 | 61篇 |
1985年 | 64篇 |
1984年 | 66篇 |
1983年 | 51篇 |
1982年 | 59篇 |
1981年 | 62篇 |
1980年 | 48篇 |
1979年 | 52篇 |
1978年 | 53篇 |
1977年 | 57篇 |
1976年 | 61篇 |
1975年 | 57篇 |
1974年 | 56篇 |
1973年 | 45篇 |
排序方式: 共有7141条查询结果,搜索用时 31 毫秒
21.
A relatively simple procedure is described for the selective and highly sensitive determination of amitrole (3-amino-1,2,4-triazole) by ionpair HPLC with amperometric detection. The separation was achieved on a polar CN-column using hexane, propanol, water (62:36:2) with LiClO4 (2.5 g·l–1) and trichloroacetic acid (2 g·l–1) as electrolytes. The determination range lies between 500 pg and 500 ng and the limit of detection was found to be 200 pg (s.d.: 11%; N=9). The minimum detectability for the alternative UV-monitoring was 2.5 ng. The developed method may be helpful in production and quality control and for the selective determination of amitrole in commercial formulations. 相似文献
22.
23.
Nicolas Meyer Mohamad Nasser Eddine Christelle Delaite Guy Hurtrez Philippe Dumas 《Journal of polymer science. Part A, Polymer chemistry》2003,41(21):3329-3335
The reactions of polystyryllithium and potassium on dimethoxymethyl 1,1‐diphenylethylene derivatives were studied in different solvents. In a polar medium, A3 and A6 star types were formed according to the stoichiometry, whereas in a nonpolar medium, hyperbranched structures were synthesized. Extensions of an already proposed mechanism in polar and nonpolar media were examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3329–3335, 2003 相似文献
24.
Lisa A. Liotta Irene Medina Jennifer L. Robinson Po-Shen Pan Jennifer V.C. Johnston Fiona A. Curtis Shelli R. McAlpine 《Tetrahedron letters》2004,45(46):8447-8450
Described are the syntheses of 15 macrocyclic peptides designed to trap Holliday junctions (HJs) in bacteria during site-specific and homologous recombination. This leads to inhibiting bacterial growth. These second generation macrocycles were based on the C-2 symmetrical HJ. They were synthesized using a strategy that permits elucidation of the amino acid role in binding HJs. The syntheses of these macrocycles are an important step in the development of a new class of antibiotics. 相似文献
25.
Thomas J. Delia Dennis P. Anderson Jennifer M. Schomaker 《Journal of heterocyclic chemistry》2004,41(6):991-993
In a continuation of our studies involving the nucleophilic displacement of one of the chlorines from 2,4,6‐trichloropyrimidine, we now report the initial displacement of one of the fluorine atoms from 2,4,6‐trifluoropyrimidine using both aliphatic and aromatic amines. The monosubstitution products favor 2‐substitution with ammonia and ethanolamine while aniline gave the 4‐substituted derivative as the preferred product. 相似文献
26.
S. Bouneau F. Azaiez J. Duprat I. Deloncle M.G. Porquet A. Astier M. Bergström C. Bourgeois L. Ducroux B.J.P. Gall M. Kaci Y. Le Coz M. Meyer E.S. Paul N. Redon M.A. Riley H. Sergolle J.F. Sharpey-Schafer J. Timar A.N. Wilson R. Wyss 《The European Physical Journal A - Hadrons and Nuclei》1998,2(3):245-248
27.
28.
29.
30.