全文获取类型
收费全文 | 508篇 |
免费 | 64篇 |
国内免费 | 79篇 |
专业分类
化学 | 342篇 |
晶体学 | 12篇 |
力学 | 15篇 |
综合类 | 5篇 |
数学 | 130篇 |
物理学 | 147篇 |
出版年
2024年 | 4篇 |
2023年 | 29篇 |
2022年 | 43篇 |
2021年 | 44篇 |
2020年 | 51篇 |
2019年 | 19篇 |
2018年 | 25篇 |
2017年 | 18篇 |
2016年 | 16篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 15篇 |
2012年 | 17篇 |
2011年 | 18篇 |
2010年 | 15篇 |
2009年 | 13篇 |
2008年 | 23篇 |
2007年 | 24篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 23篇 |
1996年 | 27篇 |
1995年 | 28篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有651条查询结果,搜索用时 203 毫秒
141.
This paper is a continuation of the authors recent work [Beir?o da Veiga, H.and Yang, J., On mixed pressure-velocity regularity criteria to the Navier-Stokes equations in Lorentz spaces, Chin. Ann. Math., 42(1), 2021, 1–16], in which mixed pressure-velocity criteria in Lorentz spaces for Leray-Hopf weak solutions of the three-dimensional NavierStokes equations, in the whole space R~3 and in the periodic torus T~3, are established. The purpose of the present work is to extend the result of mentio... 相似文献
142.
Dr. Quentin Lefebvre Dr. Riccardo Porta Dr. Anthony Millet Dr. Jiaqi Jia Prof. Dr. Magnus Rueping 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(6):1363-1367
Owing to their wide range of biological properties, γ-aminobutyric acid derivatives (GABA) have been extensively studied and found noteworthy industrial applications. However, atom-economical and efficient processes for their production are scarce and would greatly benefit from further investigations. Herein, we demonstrate that an iridium-based photocatalyst promotes the direct reductive cross-coupling of imines with olefins upon irradiation with visible light to give GABA derivatives in good yields and selectivities. We also stress the enabling triple role of tributylamine additive in this process, discuss the advantages of strategies based on proton-coupled electron transfer (PCET) and demonstrate the scale-up of this reaction in continuous flow. 相似文献
143.
一类奇摄动非线性方程的激波解 总被引:2,自引:0,他引:2
利用匹配条件讨论一类奇摄动非线性方程激波解.得出了对应的激波解与边界条件的关系. 相似文献
144.
讨论了一类具有超抛物型方程的反应扩散问题.首先,证明了比较定理.其次,构造了形式渐近解.然后,利用微分不等式方法,研究了问题解的存在、唯一性和渐近性态.最后得到了原问题解的渐近展开式. 相似文献
145.
Zhaolai Huang Jiaqi Li Mengxiao Zhang Weilin Feng Chuanjie Fang Liping Zhu 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2298-2308
Polymers of intrinsic microporosity (PIMs) are promising materials for membrane separation because their special rigid and contorted structures contribute to high permeability. However, their chain rearrangement to fill excessive free volume makes the permeability stability a tough challenge. In this work, we report on a new use of rutile nano-TiO2 to mitigate the physical aging of PIM-1 (a typical PIM) nanofilms for stable permeability by mixing matrix. It was shown that the PIM-1 membrane incorporated with nano-TiO2 displayed remarkably higher aging resistance with a lower swelling degree in long-term ethanol soaking, having more stable ethanol permeance with only a 5% decrease after 35 days, lower than 25% of the pure one. The mechanism of anti-aging was revealed by molecular simulation, thermal, tensile mechanical, and dynamic mechanical analysis. It was found that nano-TiO2 had good compatibility with PIM-1 due to strong coordination interaction, making its uniform dispersion in polymer. Additional solvent permeation channels were also created to increase solvent permeance without compromising solute rejection. Due to the reliable interaction of nano-TiO2, which makes particles serve as physical crosslinking points, the movement of PIM-1 chains was limited partially to mitigate aging, enabling PIM-1-based membranes to have robust solvent permeation. 相似文献
146.
Sheng Xianxian Xu Zhiqiang Liu Yulong Wang Peng Dong Jiaqi Lu Zhanpeng Shan Ali Lyu Shuguang 《Research on Chemical Intermediates》2022,48(4):1645-1663
Research on Chemical Intermediates - In this study, the removal performance and degradation mechanisms of fluoranthene (FLT) in sodium percarbonate (SPC) activated by Fe(II) system were... 相似文献
147.
Carbon has three hybridization forms of sp−, sp2− and sp3−, and the combination of different forms can obtain different kinds of carbon allotropes, such as diamond, carbon nanotubes, fullerene, graphynes (GYs) and graphdiyne (GDY). Among them, the GDY molecule is a single-layer two-dimensional (2D) planar structure material with highly π-conjugation formed by sp− and sp2− hybridization. GDY has a carbon atom ring composed of benzene ring and acetylene, which makes GDY have a uniformly distributed pore structure. In addition, GDY planar material have some slight wrinkles, which makes GDY have better self-stability than other 2D planar materials. The excellent properties of GDY make it attract the attention of researchers. Therefore, GDY is widely used in chemical catalysis, electronics, communications, clean energy and composite materials. This paper summarizes the recent progress of GDY research, including structure, preparation, properties and application of GDY in the field of catalysts. 相似文献
148.
作为新一代低成本、高效率的光伏器件,以有机卤化铅CH3NH3PbX3(MAPbX3,X=Br、I、Cl)为光吸收层的钙钛矿太阳能电池(PSCs)相比于其他类型的光伏器件,具有原料丰富、工艺简单等特点。在较短的时间内,该类电池效率已由3.8%迅速攀升至25.7%,几乎可以媲美商用硅太阳能电池,成为能源应用领域的一颗新星。氧化锌(ZnO)因其具有材料易于加工、电子迁移率高、制造成本低廉且形貌结构多样等优点,被作为该类电池较为重要的一种电子传输层(ETL)而被广为研究。本文主要以不同结构的ZnO纳米薄膜ETL作为研究对象,对其在PSCs中的应用进行了总结,详细介绍了基于不同形貌ZnO纳米结构PSCs的研究进展,分析了该类电池面临的主要问题与解决处理方式,并对未来的发展趋势进行了展望。 相似文献
149.
BOUNDARY VALUE PROBLEMS TO A CLASS OF SINGULARLY PERTURBED NONLINEAR SYSTEM WITH TURNING POINTS 总被引:1,自引:0,他引:1
ConsidertheboundaryvalueproblemtothesingularlyperturbednonlinearsystemintheformofwhereEisasmallpositiveparameter,y=(yi,'..)y.),f=(fi,...)fn),A=(Al,'',A.)andB=(BI,sn).MohasdiscussedtheseDroblemsundervarioussituationsusingthemethodofdifferentialinequalities[1--'].Inthispaperweconsiderthecaseoffi.:(0,y,y')=0anduseaclassofnewboundarylayerfunctions.TheoremAssumethat(a)fi(x,y,z)Hfi(x,yi,'',yn,if)''jz.)eC'{xE[~l,1],yie[di,ei],ifER}andtherearepositivenondecreasingcontinuousfunctionsif,i=1,2,'… 相似文献
150.
Pu Wenjing Xi Xuyao Tao Pengyu Shi Bo Wen Jiaqi Lu Wei 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3295-3301
Journal of Radioanalytical and Nuclear Chemistry - Polysilane is expected to be a highly efficient and environmentally friendly liquid scintillator, for its unique fluorescence performance based on... 相似文献