全文获取类型
收费全文 | 10161篇 |
免费 | 861篇 |
国内免费 | 835篇 |
专业分类
化学 | 7732篇 |
晶体学 | 109篇 |
力学 | 285篇 |
综合类 | 66篇 |
数学 | 1706篇 |
物理学 | 1959篇 |
出版年
2024年 | 9篇 |
2023年 | 105篇 |
2022年 | 198篇 |
2021年 | 304篇 |
2020年 | 329篇 |
2019年 | 297篇 |
2018年 | 255篇 |
2017年 | 252篇 |
2016年 | 481篇 |
2015年 | 430篇 |
2014年 | 498篇 |
2013年 | 711篇 |
2012年 | 900篇 |
2011年 | 983篇 |
2010年 | 695篇 |
2009年 | 603篇 |
2008年 | 756篇 |
2007年 | 740篇 |
2006年 | 654篇 |
2005年 | 549篇 |
2004年 | 476篇 |
2003年 | 304篇 |
2002年 | 255篇 |
2001年 | 131篇 |
2000年 | 114篇 |
1999年 | 121篇 |
1998年 | 68篇 |
1997年 | 67篇 |
1996年 | 67篇 |
1995年 | 52篇 |
1994年 | 42篇 |
1993年 | 42篇 |
1992年 | 40篇 |
1991年 | 33篇 |
1990年 | 35篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 24篇 |
1986年 | 15篇 |
1985年 | 28篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1975年 | 6篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
Dr. Juan M. Ortiz‐Sánchez Dr. Ricard Gelabert Prof. Miquel Moreno Prof. José M. Lluch 《Chemphyschem》2010,11(17):3696-3703
A quantum electronic study of the effect of substituents on (2,2′‐bipyridyl)‐3,3′‐diol and (2,2′‐bipyridyl)‐3,3′‐diamine is presented. A large difference in the photochemical behavior between the original and the substituted selected systems is expected. For the sake of simplicity, the study is restricted to the symmetrically bi‐substituted compounds: fluorine, the more electronegative atom and thus a strong σ‐acceptor but also a weak π‐donor group, and NO2, a strong π‐acceptor substituent. Among the large set of compounds studied, two receive special attention: 5,5′‐dinitro‐(2,2′‐bipyridyl)‐3,3′‐diamine and 6,6′‐difluoro‐(2,2′‐bipyridyl)‐3,3′‐diol. While in the former case the nitro substitution transforms (2,2′‐bipyridyl)‐3,3′‐diamine, previously suggested to behave as a photomemory material, into a simple fluorescent species, the latter substitution turns (2,2′‐bipyridyl)‐3,3′‐diol into a fresh new candidate for a photomemory device. 相似文献
993.
994.
The electrochemistry of platinum single crystals is historically reviewed. After a brief revision of historical results dating before the publication of the landmark experiment by J. Clavilier of the flame annealing in 1980, the controversy introduced by this experiment into the surface electrochemistry community is described. Questions about the structure and composition of the platinum surface after the flame annealing and their implications on the characteristic voltammetry of platinum single crystal electrodes were slowly answered in the years that followed the first introduction of this methodology. One of the last questions to be solved was that about the nature of the chemical species responsible for the charge transfer process that leads to the so-called unusual features in the voltammogram. This was solved with the charge displacement experiment. Nowadays, a great deal of knowledge has been gathered about the structure of the interphase between platinum electrodes and electrolytic solutions and also about the electrocatalytic behaviour of platinum surfaces. State-of-the-art information about platinum electrochemistry is provided, with emphasis on results from our group, especially those obtained with a thermodynamic analysis, involving either constant or variable temperatures and with the laser-induced temperature jump method. 相似文献
995.
996.
997.
998.
999.
In the even dimensional case the discrete Dirac equation may be reduced to the so-called discrete isotonic Dirac system in
which suitable Dirac operators appear from both sides in half the dimension. This is an appropriated framework for the development
of a discrete Martinelli–Bochner formula for discrete holomorphic functions on the simplest of all graphs, the rectangular
\mathbbZm{\mathbb{Z}^m} one. Two lower-dimensional cases are considered explicitly to illustrate the closed analogy with the theory of continuous
variables and the developed discrete scheme. 相似文献
1000.
Carbon black (CB) without micropores was functionalized by mixed acid and used to explore the surface chemistry effect on the production of hydrogen peroxide (H2O2). The CB materials were characterized by N2 adsorption‐desorption, XRD, SEM, FTIR, and TPD. The results of different characterization methods indicated that both the textural features and the surface chemical properties of CB were significantly modified by the acidic treatment. The catalytic performance of the modified CBs for hydroxylamine (NH2OH) oxidation increased with increasing the surface oxygen‐containing species. The yield of H2O2 approached 30% with the corresponding concentration of 73.9 mmol·L?1 (w=0.25%) over the most promising CB catalyst, which was much superior to the results obtained on supported noble metals. Correlations between catalytic activity and concentration of different surface functional groups on the CB samples confirmed that the quinonoid species might be the active species. 相似文献