全文获取类型
收费全文 | 1743篇 |
免费 | 61篇 |
国内免费 | 17篇 |
专业分类
化学 | 971篇 |
晶体学 | 12篇 |
力学 | 73篇 |
数学 | 404篇 |
物理学 | 361篇 |
出版年
2023年 | 13篇 |
2022年 | 47篇 |
2021年 | 72篇 |
2020年 | 74篇 |
2019年 | 69篇 |
2018年 | 44篇 |
2017年 | 52篇 |
2016年 | 89篇 |
2015年 | 60篇 |
2014年 | 78篇 |
2013年 | 107篇 |
2012年 | 131篇 |
2011年 | 120篇 |
2010年 | 59篇 |
2009年 | 59篇 |
2008年 | 71篇 |
2007年 | 70篇 |
2006年 | 51篇 |
2005年 | 53篇 |
2004年 | 46篇 |
2003年 | 35篇 |
2002年 | 45篇 |
2001年 | 26篇 |
2000年 | 25篇 |
1999年 | 14篇 |
1998年 | 19篇 |
1997年 | 9篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 17篇 |
1982年 | 24篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1968年 | 3篇 |
排序方式: 共有1821条查询结果,搜索用时 15 毫秒
41.
42.
43.
Chieu D. Tran Dora Ilieva Santhosh Challa 《Journal of Sol-Gel Science and Technology》2004,32(1-3):207-217
Concentration distributions and conformations of bovine serum albumin (BSA) entrapped in sol–gels were successfully determined for the first time by use of the recently developed NIR multispectral imaging instrument. It was found that BSA molecules were inhomogeneously distributed within the sol–gel matrix, independent of its concentration. At relatively high concentration (366 mg/mL) the encapsulation process does not seem to produce any observable changes in the conformation of BSA. However, when the concentration of BSA was decreased to 220 mg/mL, pronounced changes in the spectra of the protein were observed as a function of (sol–gel reaction) time. The observed inhomogenity might be traced to both a non-uniform concentration distribution of BSA and changes in protein native conformation resulting from interactions between the charged protein and the silicate anions. Results obtained seem to suggest that the protein molecules might adapt themselves to accommodate evolving geometry and sites of the silica network. 相似文献
44.
45.
46.
Dr. Ngoc-Anh Tran Nhan Do Van Thanh Prof. My Loan Phung Le 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9198-9217
Magnesium batteries, like lithium-ion batteries, with higher abundance and similar efficiency, have drawn great interest for large-scale applications such as electric vehicles, grid energy storage and many more. On the other hand, the use of organic electrode materials allows high energy-performance, metal-free, environmentally friendly, versatile, lightweight, and economically efficient magnesium storage devices. In particular, the structural diversity and the simple activity of organic molecules make redox properties, and hence battery efficiency, easy to monitor. While organic magnesium batteries still in their infancy, this field becomes more and more promising because significant results were reported. To summarize the achievements in studies on organic cathodes for magnesium systems, their synthesis is discussed, combined with electrode design to provide the basis for controlling the electrochemical properties. Moreover, the techniques to synthesize organic materials with high-yield are mentioned. Finally, potential problems and prospects are explored to further improve organic cathodes. 相似文献
47.
Tran Dan Thu 《Annals of Combinatorics》2013,17(4):755-763
The LYMinequality (Lubell, Yamamoto, Meshalkin) is a generalization of Sperner’s theorem for antichains. Kleitman and Harper independently proved that the LYM inequality and the normalized matching property (or local LYM inequality) are equivalent. Many contributions have been proposed to sharpen the LYM inequality. Noticeably, Ahlswede and Zhang lifted the LYM inequality to an identity, called the AZ identity. Thus, one expects that the same sharpening of the local LYM inequality is equivalent to the AZ identity. In this paper, we introduce a local LYM identity which sharpens the local LYM inequality and prove that it is equivalent to the AZ identity. The local LYM identity shows local relationships between components in the AZ identity. 相似文献
48.
49.
50.
A. P. Molchanov T. Q. Tran A. V. Stepakov G. L. Starova R. R. Kostikov 《Russian Journal of Organic Chemistry》2014,50(1):78-82
N-Aryl-C-(arylcarbamoyl)nitrones regioselectively add to methyl 2-(2-phenylcyclopropylidene)-acetate and methyl 2-methylidene-3-phenylcyclopropanecarboxylate to give in each case two diastereoisomeric 5-oxa-6-azaspiro[2.4]heptane-4-carboxylates. 相似文献