全文获取类型
收费全文 | 20358篇 |
免费 | 2458篇 |
国内免费 | 1980篇 |
专业分类
化学 | 7449篇 |
晶体学 | 156篇 |
力学 | 5334篇 |
综合类 | 315篇 |
数学 | 5539篇 |
物理学 | 6003篇 |
出版年
2024年 | 11篇 |
2023年 | 188篇 |
2022年 | 346篇 |
2021年 | 541篇 |
2020年 | 607篇 |
2019年 | 496篇 |
2018年 | 498篇 |
2017年 | 670篇 |
2016年 | 789篇 |
2015年 | 638篇 |
2014年 | 915篇 |
2013年 | 1485篇 |
2012年 | 940篇 |
2011年 | 1128篇 |
2010年 | 990篇 |
2009年 | 1178篇 |
2008年 | 1257篇 |
2007年 | 1374篇 |
2006年 | 1260篇 |
2005年 | 1087篇 |
2004年 | 966篇 |
2003年 | 950篇 |
2002年 | 730篇 |
2001年 | 685篇 |
2000年 | 587篇 |
1999年 | 542篇 |
1998年 | 506篇 |
1997年 | 445篇 |
1996年 | 431篇 |
1995年 | 407篇 |
1994年 | 316篇 |
1993年 | 282篇 |
1992年 | 246篇 |
1991年 | 214篇 |
1990年 | 147篇 |
1989年 | 126篇 |
1988年 | 117篇 |
1987年 | 106篇 |
1986年 | 89篇 |
1985年 | 91篇 |
1984年 | 66篇 |
1983年 | 37篇 |
1982年 | 74篇 |
1981年 | 70篇 |
1980年 | 33篇 |
1979年 | 47篇 |
1978年 | 26篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Jose M. Guisan Gloria Fernandez-Lorente Javier Rocha-Martin Daniel Moreno-Gamero 《Current Opinion in Green and Sustainable Chemistry》2022
Different strategies for the preparation of efficient and robust immobilized biocatalysts are here reviewed. Different physico-chemical approaches are discussed.i.- The stabilization of enzyme by any kind of immobilization on pre-existing porous supports.ii.- The stabilization of enzymes by multipoint covalent attachment on support surfaces.iii.- Additional stabilization of immobilized-stabilized enzyme by physical or chemical modification with polymers.These three strategies can be easily developed when enzymes are immobilized in pre-existing porous supports. In addition to that, these immobilized-stabilized derivatives are optimal to develop enzyme reaction engineering and reactor engineering. Stabilizations ranging between 1000 and 100,000 folds regarding diluted soluble enzymes are here reported. 相似文献
2.
3.
Applied Mathematics and Mechanics - Mechanical models of residually stressed fibre-reinforced solids, which do not resist bending, have been developed in the literature. However, in some residually... 相似文献
4.
《中国物理 B》2021,30(5):55207-055207
Trichel pulse is a kind of pulsed mode in negative DC corona discharge, which has attracted significant attention because of its considerable applications in industry. Over eighty years, plenty of effort including simulations and experiments has been spent to reveal the ionization and quenching mechanisms of Trichel pulse. By revisiting and summarizing the basic characteristics and well-accepted ionization and quenching mechanisms, this review provides a basic understanding and the current status of Trichel pulse. 相似文献
5.
《中国物理 B》2021,30(5):56501-056501
Thermal expansion control is always an obstructive factor and challenging in high precision engineering field. Here,the negative thermal expansion of Nb F_3 and Nb OF_2 was predicted by first-principles calculation with density functional theory and the quasi-harmonic approximation(QHA). We studied the total charge density, thermal vibration, and lattice dynamic to investigate the thermal expansion mechanism. We found that the presence of O induced the relatively strong covalent bond in Nb OF_2, thus weakening the transverse vibration of F and O in Nb OF_2, compared with the case of Nb F_3.In this study, we proposed a way to tailor negative thermal expansion of metal fluorides by introducing the oxygen atoms.The present work not only predicts two NTE compounds, but also provides an insight on thermal expansion control by designing chemical bond type. 相似文献
6.
7.
Wacker oxidation is an industry-adopted process to transform olefins into value-added epoxides and carbonyls. However, traditional Wacker oxidation involves the use of homogeneous palladium and copper catalysts for the olefin addition and reductive elimination. Here, we demonstrated an ultrahigh loading Cu single atom catalyst(14% Cu, mass fraction) for the palladium-free Wacker oxidation of 4-vinylanisole into the corresponding ketone with N-methylhydroxylamine hydrochloride as an additive under mild conditions. Mechanistic studies by 18O and deuterium isotope labelling revealed a hydrogen shift mechanism in this palladium-free process using N-methylhydroxylamine hydrochloride as the oxygen source. The reaction scope can be further extended to Kucherov oxidation. Our study paves the way to replace noble metal catalysts in the traditional homogeneous processes with single atom catalysts. 相似文献
8.
9.
10.
Andrey V. Lunchev Dr. Samuel A. Morris Dr. Rakesh Ganguly Prof. Andrew C. Grimsdale 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1819-1823
A route to the synthesis of novel 5,7-diazapentacenes and some preliminary studies on their properties is reported. A single crystal X-ray diffraction study of the dihexyl derivative showed it had formed a dimer during the analysis. The materials possess lower lying frontier orbitals than pentacene and may have potential applications in organic electronic devices. This synthetic method may be applicable to the synthesis of other azaacenes. 相似文献