全文获取类型
收费全文 | 93707篇 |
免费 | 25709篇 |
国内免费 | 20801篇 |
专业分类
化学 | 61597篇 |
晶体学 | 1129篇 |
力学 | 6194篇 |
综合类 | 351篇 |
数学 | 12294篇 |
物理学 | 58652篇 |
出版年
2024年 | 446篇 |
2023年 | 826篇 |
2022年 | 937篇 |
2021年 | 915篇 |
2020年 | 1253篇 |
2019年 | 1874篇 |
2018年 | 1727篇 |
2017年 | 2356篇 |
2016年 | 2718篇 |
2015年 | 3000篇 |
2014年 | 2985篇 |
2013年 | 5098篇 |
2012年 | 5519篇 |
2011年 | 8292篇 |
2010年 | 10943篇 |
2009年 | 11061篇 |
2008年 | 4488篇 |
2007年 | 3908篇 |
2006年 | 3573篇 |
2005年 | 3830篇 |
2004年 | 4990篇 |
2003年 | 3988篇 |
2002年 | 3851篇 |
2001年 | 3943篇 |
2000年 | 2834篇 |
1999年 | 2960篇 |
1998年 | 2513篇 |
1997年 | 2173篇 |
1996年 | 2502篇 |
1995年 | 2937篇 |
1994年 | 2948篇 |
1993年 | 3127篇 |
1992年 | 2757篇 |
1991年 | 2364篇 |
1990年 | 2018篇 |
1989年 | 2085篇 |
1988年 | 1915篇 |
1987年 | 1179篇 |
1986年 | 1232篇 |
1985年 | 892篇 |
1984年 | 999篇 |
1982年 | 908篇 |
1981年 | 738篇 |
1980年 | 777篇 |
1979年 | 532篇 |
1978年 | 540篇 |
1977年 | 649篇 |
1976年 | 1046篇 |
1973年 | 442篇 |
1972年 | 538篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
International Journal of Theoretical Physics - We consider the stationary state of a spin-orbit coupled (SOC) binary Bose-Einstein condensates with dipole-dipole interaction (DDI). Our results are... 相似文献
4.
Zhen Xi 《中国科学:化学(英文版)》2015,(3):434-435
Redox-based post-translational modification of protein thiols has become an attractive strategy in cellular homeostasis and cell signaling.Due to the reductive end of the redox buffer network,the vicinal dithiol-containing proteins(VDPs)maintains an appropriate oxidation-reduction state of proteins through the reversible transformation from vicinal dithiols to disulfide,which is responsible for a variety of 相似文献
5.
量子自旋液体是最近几年刚被人们证实除铁磁体、反铁磁体之外的第三种磁性类型,因其有望解释高温超导的运行机制、改变计算机硬盘信息存储方式而在物理、材料等领域备受关注。自旋阻挫作为量子自旋液体的最小单元可能是解开量子自旋液体诸多问题的钥匙,所以在磁学、电学研究领域再一次成为人们研究的热点。基于文献报道的三核铜配合物[Cu3(μ3-OH)(μ-OPz)3(NO3)2(H2O)2]·CH3OH(1),我们合成了三维金属有机框架配合物{[Ag(HOPz)Cu3(μ3-OH)(NO3)3(OPz)2Ag(NO3)]·6H2O}n(2)(HOPz=甲基(2-吡嗪基)酮肟),并从自旋阻挫的角度对二者磁性质进行对比和详细分析。磁化率数据表明自旋间有很强的反铁磁相互作用和反对称交换。通过包含各向同性和反对称交换的哈密顿算符对两者磁学数据进行拟合并研究其磁构关系,所获最佳拟合参数为:配合物1:Jav=-426 cm^-1,g⊥=1.83,g∥=2.00;配合物2:Jav=-401 cm^-1,g⊥=1.85,g∥=2.00。 相似文献
6.
Lijuan Shen Li Li Sheng Lu Xiaohan Zhang Jie Liu Junlin An Guojun Zhang Bo Wu Fei Wang 《中国颗粒学报》2015,(3):10-15
We conducted measurements of black carbon(BC) aerosol in Jiaxing,China during autumn from September 26 to November 30,2013.We investigated temporal and diurnal variations of BC,and its correlations with meteorological parameters and other major pollutants.Results showed that hourly mass concentrations of BC ranged from 0.2 to 22.0 μg/m3,with an average of 5.1 μg/m3.The diurnai variation of BC exhibited a bimodal distribution,with peaks at 07:00 and 18:00.The morning peak was larger than the evening peak.The mass percentages of BC in PM2.5 and PM10 were 7.1%and 4.8%,respectively.The absorption coefficient of BC was calculated to be 44.4 Mm-1,which accounted for 11.1%of the total aerosol extinction.BC was mainly emitted from local sources in southwestern Jiaxing where BC concentrations were generally greater than 11 μg/m3 during the measurement period.Correlation analysis indicated that the main sources of BC were motor vehicle exhaust,and domestic and industrial combustion. 相似文献
7.
This minireview describes the strategies for synthesis of fiuorinated surfactants potentially nonbioaccumulable.Various strategies have been focused on(Ⅰ) reducing the length of the perfluorocarbon chain,(Ⅱ) introducing hetero atoms into the fluorocarbon chain,(Ⅲ) introducing branch(herein and after branch means the fluoro-carbon chain section is not straight).In most cases,the surface tensions versus the surfactant concentrations have been assessed.These above strategies led to various highly fiuorinated(perfluorinated or not perfluorinated) surfactants whose chemical changes enabled to obtain novel alternatives to perfluorooctanoic acid(PFOA) and perfluorooctane sulphonate(PFOS). 相似文献
8.
9.
10.
Simultaneous quantitative determination of 20 active components in the traditional Chinese medicine formula Zhi‐Zi‐Da‐Huang decoction by liquid chromatography coupled with mass spectrometry: application to study the chemical composition variations in different combinations 下载免费PDF全文
Zheng Tang Ran Yin Kaishun Bi Heyun Zhu Fei Han Kelin Chen Fenrong Wang 《Biomedical chromatography : BMC》2015,29(9):1406-1414