全文获取类型
收费全文 | 2798篇 |
免费 | 86篇 |
国内免费 | 9篇 |
专业分类
化学 | 1885篇 |
晶体学 | 46篇 |
力学 | 56篇 |
数学 | 443篇 |
物理学 | 463篇 |
出版年
2023年 | 9篇 |
2022年 | 36篇 |
2021年 | 70篇 |
2020年 | 64篇 |
2019年 | 60篇 |
2018年 | 46篇 |
2017年 | 55篇 |
2016年 | 85篇 |
2015年 | 84篇 |
2014年 | 94篇 |
2013年 | 190篇 |
2012年 | 153篇 |
2011年 | 179篇 |
2010年 | 145篇 |
2009年 | 116篇 |
2008年 | 174篇 |
2007年 | 155篇 |
2006年 | 127篇 |
2005年 | 129篇 |
2004年 | 109篇 |
2003年 | 91篇 |
2002年 | 84篇 |
2001年 | 30篇 |
2000年 | 37篇 |
1999年 | 33篇 |
1998年 | 27篇 |
1997年 | 28篇 |
1996年 | 26篇 |
1995年 | 26篇 |
1994年 | 23篇 |
1993年 | 18篇 |
1992年 | 27篇 |
1991年 | 34篇 |
1990年 | 27篇 |
1989年 | 19篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 20篇 |
1979年 | 11篇 |
1978年 | 14篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1975年 | 7篇 |
1969年 | 6篇 |
排序方式: 共有2893条查询结果,搜索用时 15 毫秒
181.
The reactions of p‐nitrophenyl acetate (PNPA) with a series of monopyridinium oximes, viz. 2‐PAM (2‐hydroxyiminomethyl‐1‐methylpyridinium iodide), 3‐PAM (3‐hydroxyiminomethyl‐1‐methylpyridinium iodide), and 4‐PAM (4‐hydroxyiminomethyl‐1‐methylpyridinium iodide) have been studied in the presence of cationic surfactants of same hydrophobic chain length (C16) within the concentration range of 0.5–6.0 mM at pH 8.0 under the pseudo‐first‐order condition. The observed rate constant (kobs) increases with increasing surfactant concentration culminating into a maximum, and this has been analyzed in detail following the concepts of micellar catalysis. The structure–activity relationship of the investigated oximes has been discussed, and 2‐PAM was found to be the most reactive among all the three investigated oximes for the cleavage of PNPA. Esterolytic decomposition of p‐nitrophenyldiphenyl phosphate with oximate ions (? CH?NO?) was followed in cetyltrimethylammonium bromide micelles at pH 9.0, and 4‐PAM was the most reactive oxime for the micellar hydrolysis of phosphate ester. The apparent acid dissociation constants (pKa) of the investigated oximes have been determined spectrophotometrically. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 569–578, 2011 相似文献
182.
183.
184.
Marek Wichtowski Andrzej Ziółkowski Ewa Weinert-Rączka 《Central European Journal of Physics》2008,6(3):546-554
In our work we propose a novel method of analysis of photorefractive transport equations. The method based on a perturbative
approach can be used in the case of two wave mixing and four wave mixing geometry, i.e. for the samples illuminated by interference
patterns. Presented approach can be employed for a broad range of material and experimental parameters, particularly for arbitrary
depth of light modulation pattern. The approximate analytical solution is compared with results of numerical calculations
and a good agreement practically in every case was found.
Presented at 9-th International Workshop on Nonlinear Optics Applications, NOA 2007, May 17–20, 2007, Šwinoujście, Poland 相似文献
185.
Marek Gaździcki Mark I. Gorenstein Stanislaw Mrówczyński 《The European Physical Journal C - Particles and Fields》1998,5(1):129-133
The pion multiplicity per participating nucleon in central nucleus–nucleus collisions at the energies 2–15 AGeV is significantly smaller than in nucleon–nucleon interactions at the same collision energy. This effect of pion suppression is argued to appear due to the evolution of the system produced at the early stage of heavy–ion collisions towards a local
thermodynamic equilibrium and further isentropic expansion.
Received: 21 July 1997 / Revised version: 12 November 1997 / Published online: 26 February 1998 相似文献
186.
Ohne Zusammenfassung 相似文献
187.
Mathematische Annalen - 相似文献
188.
Marek L. Główka Zbigniew J. Kamiński Gastone Gilli Valerio Bertolasi 《Journal of chemical crystallography》1986,16(4):569-576
C14H17NO4 crystallizes in the monoclinic space groupP21/n (Z=4) witha=10.208(2),b=10.888(2),c=11.909(2) Å, and=90.89(2)°. The structure was solved by direct methods and refined by full-matrix LSQ to anR factor of 0.036. The 4-oxo-1,3-dioxane ring is in a slightly distorted O(1)-sofa conformation flattened at the C(4) end with the 5-isopropyl substituent in a pseudoaxial position and planar lactone group. The molecules form dimers by means of intermolecular N-HO(4) hydrogen bonds of 3.091(2) Å. The1H NMR spectrum of the title compound shows unusual features. 相似文献
189.
190.