全文获取类型
收费全文 | 1487篇 |
免费 | 40篇 |
国内免费 | 13篇 |
专业分类
化学 | 923篇 |
晶体学 | 2篇 |
力学 | 45篇 |
数学 | 343篇 |
物理学 | 227篇 |
出版年
2023年 | 10篇 |
2022年 | 17篇 |
2021年 | 36篇 |
2020年 | 28篇 |
2019年 | 23篇 |
2018年 | 20篇 |
2017年 | 17篇 |
2016年 | 58篇 |
2015年 | 31篇 |
2014年 | 34篇 |
2013年 | 82篇 |
2012年 | 72篇 |
2011年 | 125篇 |
2010年 | 62篇 |
2009年 | 49篇 |
2008年 | 92篇 |
2007年 | 91篇 |
2006年 | 80篇 |
2005年 | 53篇 |
2004年 | 43篇 |
2003年 | 41篇 |
2002年 | 32篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 14篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 21篇 |
1995年 | 14篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 14篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1970年 | 6篇 |
1858年 | 7篇 |
排序方式: 共有1540条查询结果,搜索用时 31 毫秒
91.
92.
Curcumin, a chemical compound present in the well-known Indian spice turmeric, has uses in many different fields ranging from
medicinal chemistry to the dye industry. Its poor water solubility, though, makes Curcumin difficult to handle, making it
less appealing for potential uses. The principal aim of this work is to perform a computational study of the structural and
electronic properties of Curcumin {IUPAC name: 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione} in several solvents,
and a comparison with experimental data. Rotameric equilibria, vibrational and thermochemical analysis, and electronic absorption
spectra (with ab initio and semi-empirical methodologies) have been studied, both in vacuum and in three selected solvents. Different computational
techniques have been applied and the results compared. Combined approaches resulted in very satisfactory results. Interesting
results have emerged, which suggest subsequent investigations about the nature of the excited states and potential derivatives
of Curcumin that possibly have non-linear optical applications, as a π-core for innovative materials in laser engineering and photonics. 相似文献
93.
94.
95.
Ahmed Abouelaz Enrico Casadio Tarabusi Abdallah Ihsane 《Mediterranean Journal of Mathematics》2009,6(3):303-316
We study the Radon transform R on the discrete Grassmannian of rank-d affine sublattices of Z
n
for 0 < d < n, extending and building on previous work of the first- and third-named authors in codimension 1. By analogy with the integral
geometry on Grassmannians in R
n
, various natural questions are treated, such as definition and properties of R and its dual transform R
*, function space setting, support theorems and inversion formulas. 相似文献
96.
Franco Varsano Francesca Decker Enrico Masetti 《Monatshefte für Chemie / Chemical Monthly》2001,132(1):83-95
Summary. Ce-V mixed oxide films have been deposited by RF sputtering with the aim of increasing the Li charge capacity of counter
electrodes in smart windows. Such mixed oxides have shown high transmittance and optical passivity in the visible region.
After electrode pre-conditioning by cyclic voltammetry, a good electrochemical reversibility in LiClO4– propylene carbonate electrolyte was observed, and large Li-charge capacity under galvanostatic charging (up to 50 mCċcm−2) has been measured. The electrode charge capacity decreased after prolonged insertion-deinsertion cycles, whereas the photoptic
transmittance remained about constant. After 800 cycles the Li-charge capacity decreased to 40 mCċcm−2. The Li diffusion coefficient inside the films measured by electrochemical impedance and by galvanostatic titration ranged
from 10−11 cm2ċs−1 to 10−13cm2ċs−1. We observed that the Li charge capacity of the film electrodes is a function of the film deposition conditions, because
it increased with the vanadium oxide concentration in the target and with the oxygen content in the sputtering atmosphere.
Received June 23, 2000. Accepted (revised) August 7, 2000 相似文献
97.
Sabrina Brait Stefano Deabate Selby A. R. Knox Enrico Sappa 《Journal of Cluster Science》2001,12(1):139-173
A survey of the synthetic pathways and of the reactivity and catalytic activity of transition metal carbonyl clusters substituted with benzyne (and, for comparison, benzene and diene) ligands is given. Cluster-surface analogies are helpful in gaining an understanding of the homogeneous and heterogeneous catalytic behaviour of the clusters. 相似文献
98.
99.
100.