全文获取类型
收费全文 | 33864篇 |
免费 | 879篇 |
国内免费 | 161篇 |
专业分类
化学 | 20384篇 |
晶体学 | 232篇 |
力学 | 977篇 |
综合类 | 10篇 |
数学 | 4612篇 |
物理学 | 8689篇 |
出版年
2023年 | 161篇 |
2022年 | 159篇 |
2021年 | 564篇 |
2020年 | 528篇 |
2019年 | 468篇 |
2018年 | 531篇 |
2017年 | 486篇 |
2016年 | 886篇 |
2015年 | 744篇 |
2014年 | 892篇 |
2013年 | 1447篇 |
2012年 | 1868篇 |
2011年 | 2151篇 |
2010年 | 1224篇 |
2009年 | 1094篇 |
2008年 | 1814篇 |
2007年 | 1826篇 |
2006年 | 1674篇 |
2005年 | 2103篇 |
2004年 | 2043篇 |
2003年 | 1473篇 |
2002年 | 1029篇 |
2001年 | 733篇 |
2000年 | 673篇 |
1999年 | 437篇 |
1998年 | 371篇 |
1997年 | 382篇 |
1996年 | 482篇 |
1995年 | 390篇 |
1994年 | 384篇 |
1993年 | 401篇 |
1992年 | 377篇 |
1991年 | 309篇 |
1990年 | 256篇 |
1989年 | 241篇 |
1988年 | 232篇 |
1987年 | 207篇 |
1986年 | 208篇 |
1985年 | 301篇 |
1984年 | 255篇 |
1983年 | 210篇 |
1982年 | 233篇 |
1981年 | 211篇 |
1980年 | 199篇 |
1979年 | 183篇 |
1978年 | 207篇 |
1977年 | 173篇 |
1976年 | 159篇 |
1974年 | 155篇 |
1973年 | 137篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Dr. Yolimar Gil Dr. Alejandro Castro-Alvarez Dr. Pablo Fuentealba Prof. Evgenia Spodine Dr. Daniel Aravena 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202200336
Enhancement of axial magnetic anisotropy is the central objective to push forward the performance of Single-Molecule Magnet (SMM) complexes. In the case of mononuclear lanthanide complexes, the chemical environment around the paramagnetic ion must be tuned to place strongly interacting ligands along either the axial positions or the equatorial plane, depending on the oblate or prolate preference of the selected lanthanide. One classical strategy to achieve a precise chemical environment for a metal centre is using highly structured, chelating ligands. A natural approach for axial-equatorial control is the employment of macrocycles acting in a belt conformation, providing the equatorial coordination environment, and leaving room for axial ligands. In this review, we present a survey of SMMs based on the macrocycle belt motif. Literature systems are divided in three families (crown ether, Schiff-base and metallacrown) and their general properties in terms of structural stability and SMM performance are briefly discussed. 相似文献
2.
Peralta Cecilia Mariana Acosta Gimena Henestrosa Cecilia Gil Raúl Andrés Fernández Liliana Patricia 《Journal of Analytical Chemistry》2022,77(3):308-317
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,... 相似文献
3.
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
4.
5.
6.
7.
Guizellini Filipe Corrêa Franzin Bruno Trevizan da Silva Matheus Antonio Abra Luciana Mazotti Hojo Ossamu Pastre Iêda Aparecida Ribeiro Clóvis Augusto Paiva-Santos Carlos de Oliveira Fertonani Fernando Luis 《Journal of Thermal Analysis and Calorimetry》2021,143(1):47-60
Journal of Thermal Analysis and Calorimetry - The aim of this work is to synthesize and characterize a new structured silver–clay dried, calcined or sintered at different temperatures... 相似文献
8.
9.
10.
Mathieu Boiret Anna de Juan Nathalie Gorretta Yves-Michel Ginot Jean-Michel Roger 《Analytica chimica acta》2015
Raman chemical imaging provides chemical and spatial information about pharmaceutical drug product. By using resolution methods on acquired spectra, the objective is to calculate pure spectra and distribution maps of image compounds. With multivariate curve resolution-alternating least squares, constraints are used to improve the performance of the resolution and to decrease the ambiguity linked to the final solution. Non negativity and spatial local rank constraints have been identified as the most powerful constraints to be used. 相似文献