全文获取类型
收费全文 | 1336篇 |
免费 | 58篇 |
国内免费 | 5篇 |
专业分类
化学 | 877篇 |
晶体学 | 9篇 |
力学 | 17篇 |
数学 | 198篇 |
物理学 | 298篇 |
出版年
2023年 | 9篇 |
2022年 | 10篇 |
2021年 | 30篇 |
2020年 | 28篇 |
2019年 | 23篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 45篇 |
2015年 | 30篇 |
2014年 | 41篇 |
2013年 | 61篇 |
2012年 | 68篇 |
2011年 | 92篇 |
2010年 | 49篇 |
2009年 | 47篇 |
2008年 | 64篇 |
2007年 | 80篇 |
2006年 | 88篇 |
2005年 | 50篇 |
2004年 | 62篇 |
2003年 | 28篇 |
2002年 | 26篇 |
2001年 | 21篇 |
2000年 | 13篇 |
1999年 | 19篇 |
1998年 | 24篇 |
1997年 | 13篇 |
1996年 | 19篇 |
1995年 | 17篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 18篇 |
1979年 | 9篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1972年 | 9篇 |
排序方式: 共有1399条查询结果,搜索用时 15 毫秒
111.
Mixtures of a calix[4]arene and a naphthyridine derivative dissolved in 1,2-dichlorobenzene form thermoreversible aggregates. The aggregation process was followed by means of time-resolved multiangle light scattering at two different mixing ratios, 1:3 and 1:4, yielding a detailed record of the relative mass, the radius of gyration, and the particle scattering function of the growing aggregates. On the basis of these data, a conclusive model of the structure is presented for the developing aggregates: monomers aggregate to wormlike filaments which form branching points. Formation of branching points proceeds in a frequency and distribution which is similar to the polycondensation of ABC monomers toward non-randomly branched macromolecules (Burchard, W. Macromolecules 1977, 10, 919-927). Thus, aggregation results in hyperbranched-like particles with striking analogies to the polymerization of glucose to amylopectin. 相似文献
112.
Recent measurements revealed that commercial magnesium standard solutions showed isotopic abundance variations, which cannot clearly be distinguished from each other by calibrating against the only available isotopic reference material, SRM 980, or reference materials made from SRM 980 like IRMM-009. Therefore new SI-traceable magnesium isotopic reference materials are required. 相似文献
113.
114.
Micro- and nanotubes of an amorphous carbon nitride material were synthesized by metathesis reactions between cyanuric chloride (C3N3Cl3) and different nitrogen sources, such as Li2(CN2) or Li3(BN2). The intermediate formation of needle-shaped crystals of N(C3N3Cl2)3 was always observed in our reactions, and investigated with respect to their role as a template in the formation of tubes. Chemical analyses of the micro- and nanotubes reveal carbon to nitrogen ratios near 3:4, consistent with the suspected material C3N4. Synthesized carbon nitride materials were thermally stable up to 600 °C in inert atmosphere. They were inspected by a number of physical measurements, mainly using TEM, EDX and IR investigations. 相似文献
115.
116.
117.
118.
119.
120.