全文获取类型
收费全文 | 27525篇 |
免费 | 652篇 |
国内免费 | 105篇 |
专业分类
化学 | 15532篇 |
晶体学 | 166篇 |
力学 | 882篇 |
综合类 | 9篇 |
数学 | 3949篇 |
物理学 | 7744篇 |
出版年
2023年 | 145篇 |
2022年 | 138篇 |
2021年 | 457篇 |
2020年 | 421篇 |
2019年 | 375篇 |
2018年 | 474篇 |
2017年 | 411篇 |
2016年 | 709篇 |
2015年 | 607篇 |
2014年 | 710篇 |
2013年 | 1177篇 |
2012年 | 1444篇 |
2011年 | 1666篇 |
2010年 | 920篇 |
2009年 | 860篇 |
2008年 | 1378篇 |
2007年 | 1356篇 |
2006年 | 1212篇 |
2005年 | 1631篇 |
2004年 | 1636篇 |
2003年 | 1149篇 |
2002年 | 797篇 |
2001年 | 631篇 |
2000年 | 590篇 |
1999年 | 371篇 |
1998年 | 316篇 |
1997年 | 309篇 |
1996年 | 386篇 |
1995年 | 333篇 |
1994年 | 327篇 |
1993年 | 356篇 |
1992年 | 332篇 |
1991年 | 277篇 |
1990年 | 228篇 |
1989年 | 210篇 |
1988年 | 190篇 |
1987年 | 187篇 |
1986年 | 186篇 |
1985年 | 246篇 |
1984年 | 228篇 |
1983年 | 195篇 |
1982年 | 196篇 |
1981年 | 196篇 |
1980年 | 184篇 |
1979年 | 168篇 |
1978年 | 193篇 |
1977年 | 150篇 |
1976年 | 148篇 |
1974年 | 141篇 |
1973年 | 131篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
1.
2.
Analysis Mathematica - We introduce and study the k-Hankel Gabor transform. We investigate the localization operators for this transform. In particular, we study their trace class properties and we... 相似文献
3.
Corinne Rondeau-Mouro Mireille Cambert Laurent Blondel Yves Diascorn Léo Mbaya Nor Nadiah Binti Ahmad Nazari Sarah Helary Tiphaine Lucas 《Magnetic resonance in chemistry : MRC》2022,60(7):678-691
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample. 相似文献
4.
Nonlinear Dynamics - The nonlinear modes of a non-conservative nonlinear system are sometimes referred to as damped nonlinear normal modes (dNNMs). Because of the non-conservative... 相似文献
5.
6.
7.
Dr. Antonio M. Rodríguez Dr. Pilar Prieto Prof. Antonio de la Hoz Prof. Ángel Díaz-Ortiz D. Raúl Martín Prof. José I. García 《ChemistryOpen》2015,4(3):308-317
The aim of this work was to determine the parameters that have decisive roles in microwave-assisted reactions and to develop a model, using computational chemistry, to predict a priori the type of reactions that can be improved under microwaves. For this purpose, a computational study was carried out on a variety of reactions, which have been reported to be improved under microwave irradiation. This comprises six types of reactions. The outcomes obtained in this study indicate that the most influential parameters are activation energy, enthalpy, and the polarity of all the species that participate. In addition to this, in most cases, slower reacting systems observe a much greater improvement under microwave irradiation. Furthermore, for these reactions, the presence of a polar component in the reaction (solvent, reagent, susceptor, etc.) is necessary for strong coupling with the electromagnetic radiation. We also quantified that an activation energy of 20–30 kcal mol−1 and a polarity (μ) between 7–20 D of the species involved in the process is required to obtain significant improvements under microwave irradiation. 相似文献
8.
9.
10.