全文获取类型
收费全文 | 1714篇 |
免费 | 68篇 |
国内免费 | 5篇 |
专业分类
化学 | 1493篇 |
晶体学 | 10篇 |
力学 | 8篇 |
数学 | 108篇 |
物理学 | 168篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 113篇 |
2021年 | 79篇 |
2020年 | 47篇 |
2019年 | 52篇 |
2018年 | 36篇 |
2017年 | 47篇 |
2016年 | 78篇 |
2015年 | 67篇 |
2014年 | 65篇 |
2013年 | 111篇 |
2012年 | 97篇 |
2011年 | 135篇 |
2010年 | 85篇 |
2009年 | 74篇 |
2008年 | 112篇 |
2007年 | 88篇 |
2006年 | 59篇 |
2005年 | 79篇 |
2004年 | 59篇 |
2003年 | 41篇 |
2002年 | 34篇 |
2001年 | 18篇 |
2000年 | 18篇 |
1999年 | 6篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 11篇 |
1995年 | 17篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
排序方式: 共有1787条查询结果,搜索用时 0 毫秒
991.
992.
Cellulose--model films and the fundamental approach 总被引:1,自引:0,他引:1
This critical review describes the recent arrival of ultrathin films of cellulose. The methodology of preparation as well as the applications of the films for fundamental research is fully covered. The review places cellulose in a wider scientific context where cellulose research is no longer a field of interest for specialised scientists only. Cellulose and cellulosic materials should interest communities such as biochemists, physical chemists, surface chemists, organic chemists, polymer chemists and also physicists working close the disciplines mentioned. (149 references.). 相似文献
993.
Starting from a general operator representation in the time-frequency domain, this paper addresses the problem of approximating
linear operators by operators that are diagonal or band-diagonal with respect to Gabor frames. A characterization of operators
that can be realized as Gabor multipliers is given and necessary conditions for the existence of (Hilbert-Schmidt) optimal
Gabor multiplier approximations are discussed and an efficient method for the calculation of an operator’s best approximation
by a Gabor multiplier is derived. The spreading function of Gabor multipliers yields new error estimates for these approximations.
Generalizations (multiple Gabor multipliers) are introduced for better approximation of overspread operators. The Riesz property
of the projection operators involved in generalized Gabor multipliers is characterized, and a method for obtaining an operator’s
best approximation by a multiple Gabor multiplier is suggested. Finally, it is shown that in certain situations, generalized
Gabor multipliers reduce to a finite sum of regular Gabor multipliers with adapted windows. 相似文献
994.
995.
Aleksandra Deptuch Teresa Jaworska-Gołąb Monika Marzec Magdalena Urbańska Marzena Tykarska 《Phase Transitions》2019,92(2):126-134
Cold crystallization of liquid crystalline (S)-4’-(1-methylheptyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-2-fluorobenzoate (3F7HPhF) was studied in isothermal as well as non-isothermal conditions. For isothermal conditions at temperatures between 233 and 250?K X-ray diffraction and differential scanning calorimetry were used. The crystallization kinetics was described by the Avrami–Avramov model, and the values of Avrami exponent, characteristic time and activation energy were determined. The kinetics of the cold crystallization in non-isothermal conditions for chosen heating rates up to 0.5?K/s was studied by differential scanning calorimetry and analyzed using Ozawa, Mo and Augis–Bennett models. Cold crystallization was found to be three-dimensional and controlled by diffusion both in the isothermal and non-isothermal process, however the activation energy determined in the non-isothermal process is about two times smaller than in the isothermal one. 相似文献
996.
Tobias Paintner Jonas Bjrk Ping Du Svetlana Klyatskaya Mateusz Paszkiewicz Raphael Hellwig Martin Uphoff Murat A.
ner Edoardo Cuniberto Peter S. Deimel Yi‐Qi Zhang Carlos‐Andres Palma Francesco Allegretti Mario Ruben Johannes V. Barth Florian Klappenberger 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11407-11412
Reaction pathways involving quantum tunneling of protons are fundamental to chemistry and biology. They are responsible for essential aspects of interstellar synthesis, the degradation and isomerization of compounds, enzymatic activity, and protein dynamics. On‐surface conditions have been demonstrated to open alternative routes for organic synthesis, often with intricate transformations not accessible in solution. Here, we investigate a hydroalkoxylation reaction of a molecular species adsorbed on a Ag(111) surface by scanning tunneling microscopy complemented by X‐ray electron spectroscopy and density functional theory. The closure of the furan ring proceeds at low temperature (down to 150 K) and without detectable side reactions. We unravel a proton‐tunneling‐mediated pathway theoretically and confirm experimentally its dominant contribution through the kinetic isotope effect with the deuterated derivative. 相似文献
997.
998.
Densities (ρ) and speeds of sound (u) for the binary mixtures of 1-hexanol with n-hexane, n-octane and n-decane have been measured over the entire composition range at 298.15, 303.15 and 308.15 K. The dynamic viscosities (η) for these systems have been measured at 298.15 K. From experimental data, excess molar volumes (VmE), molar isentropic compressibility (Ks,m), excess molar isentropic compressibility (Ks,mE), deviation in speed of sound (uD) from their ideal values (uid) in an ideal mixture, and excess free volumes (VfE) have been calculated. The excess functions have also been correlated with the Redlich–Kister polynomial equation. The viscosity data have been analysed in terms of some semi-empirical equations. The theoretical values of speed of sound (u) and isentropic compressibility (κS) have also been estimated using the Prigogine–Flory–Patterson (PFP) theory with the van der Waals (vdW) potential energy model and the results have been compared with experimental values. The effect of chain-length of n-alkanes as well as the temperature on the excess properties has also been studied. 相似文献
999.
1000.