全文获取类型
收费全文 | 384篇 |
免费 | 20篇 |
专业分类
化学 | 250篇 |
晶体学 | 4篇 |
力学 | 9篇 |
数学 | 87篇 |
物理学 | 54篇 |
出版年
2023年 | 1篇 |
2022年 | 12篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 17篇 |
2013年 | 29篇 |
2012年 | 21篇 |
2011年 | 20篇 |
2010年 | 11篇 |
2009年 | 18篇 |
2008年 | 33篇 |
2007年 | 16篇 |
2006年 | 19篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 24篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1975年 | 3篇 |
排序方式: 共有404条查询结果,搜索用时 15 毫秒
111.
Abstract The electrical charge assosiated with dislocation motion in KCl:Ba has been studied within the interval from 77 to 292K using on indentation method. The comparison of the potential difference values at 77 and 292K was performed on condition that the impression diagonals were roughly equal. The kinetics of the potential change was studied. 相似文献
112.
113.
Nataliya F. Lazareva Alexandr I. Albanov Bagrat A. Shainyan Erich Kleinpeter 《Tetrahedron》2012,68(4):1097-1104
A number of N-substituted 2,2-dimethyl-1,4,2-oxazasilinanes 1 were synthesized and studied by variable temperature dynamic 1H and 13C NMR spectroscopy, room temperature 15N NMR spectroscopy and theoretical calculations at the DFT and MP2 levels of theory. Both the preferred conformers were assigned and the barrier to the ring inversion of the saturated six-membered ring determined. From 1 the corresponding methyl iodide salts were produced, their structure studied by X-ray analysis and found to be in excellent agreement with the results of the theoretical calculations. 相似文献
114.
115.
116.
The main objective of the paper is to describe asymptotic behaviour of Fourier–Haar coefficients of functions from Marcinkiewicz spaces. We also discuss the Cesàro summability and the almost convergence of sequences related to Fourier–Haar coefficients and generalise a result from [17]. Some analogues of Mercer's theorem for Fourier coefficients are proved. 相似文献
117.
118.
Dr. Lei Zhang Alexandr Fonari Yue Zhang Guangyao Zhao Dr. Veaceslav Coropceanu Prof. Wenping Hu Dr. Sean Parkin Prof. Jean‐Luc Brédas Prof. Alejandro L. Briseno 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(52):17907-17916
Tri‐isopropylsilylethynyl (TIPS)‐functionalized polycyclic aromatic hydrocarbon (PAH) molecules incorporate structural components of graphene nanoribbons and represent a family of model molecules that form organic crystal semiconductors for electronic devices. Here, we report a series of TIPS‐functionalized PAHs and discuss their electronic properties and crystal packing features. We observe that these soluble compounds easily form one‐dimensional (1 D) packing arrangements and allow a direct evolution of the π stacking by varying the geometric shape. We find that the aspect ratio between length and width plays an important role on crystal packing. Our result indicates that when the PAH molecules have zigzag edges, these can provide enough volume for the molecules to rotate and reorient, alleviating the unfavorable electrostatic interactions found in perfectly cofacial π–π stacking. Density functional theory calculations were carried out to provide insights into how the molecular geometric shape influences the electronic structure and transport properties. The calculations indicate that, among the compounds studied here, “brick‐layer” stacks provide the highest hole mobility. 相似文献
119.
Liliya I. Kasyan Stanislav A. Prid'ma Vitaliy A. Palchikov Leonid D. Karat Alexandr V. Turov Olexandr Isayev 《Journal of Physical Organic Chemistry》2011,24(8):705-713
Reactions of 2‐nitro‐, 4‐nitro‐ and 2,4‐dinitrophenylglycidyl ethers with bicyclo[2.2.1]hept‐5‐ene‐endo‐2‐ylmethylamine in isopropanol have been studied. The mixtures of products were chromatographed on silica gel and eluted with ether or ether/2‐propanol (1:1), the structures of individual products have been confirmed by IR spectra, NMR 1H, 13C spectra, using experiments that involve homonuclear and heteronuclear scalar coupling interactions (COSY, TOCSY, HMQC, HMBC), and mass spectrometry. Amino alcohols as the major products of regioselective aminolysis of epoxides (according to the Krasusky rule) have been obtained. The minor products were the compounds with two hydroxyalkyl fragments at the nitrogen atom. In case of dinitrophenylglycidyl ether, it was the minor product of aryl nucleophilic substitution (SNAr). The abnormal course of aminolysis has been confirmed by the results of quantum‐chemical calculations of activation barries and Free Gibbs energies of the competitive reactions of epoxides (at the B3LYP/6‐311 + G(d,p) level of theory). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
120.
Aleshkina SS Likhachev ME Pryamikov AD Gaponov DA Denisov AN Bubnov MM Salganskii MY Laptev AY Guryanov AN Uspenskii YA Popov NL Février S 《Optics letters》2011,36(18):3566-3568
A design of a polarizing all-glass Bragg fiber with a microstructure core has been proposed for the first time. This design provides suppression of high-order modes and of one of the polarization states of the fundamental mode. The polarizing fiber was fabricated by a new, simple method based on a combination of the modified chemical vapor deposition (MCVD) process and the rod-in-tube technique. The mode field area has been found to be about 870 μm2 near λ=1064 nm. The polarization extinction ratio better than 13 dB has been observed over a 33% wavelength range (from 1 to 1.4 μm) after propagation in a 1.7 m fiber piece bent to a radius of 70 cm. 相似文献