全文获取类型
收费全文 | 5781篇 |
免费 | 989篇 |
国内免费 | 681篇 |
专业分类
化学 | 4211篇 |
晶体学 | 53篇 |
力学 | 373篇 |
综合类 | 51篇 |
数学 | 600篇 |
物理学 | 2163篇 |
出版年
2023年 | 139篇 |
2022年 | 128篇 |
2021年 | 186篇 |
2020年 | 293篇 |
2019年 | 235篇 |
2018年 | 239篇 |
2017年 | 192篇 |
2016年 | 299篇 |
2015年 | 248篇 |
2014年 | 341篇 |
2013年 | 399篇 |
2012年 | 484篇 |
2011年 | 595篇 |
2010年 | 373篇 |
2009年 | 401篇 |
2008年 | 403篇 |
2007年 | 342篇 |
2006年 | 300篇 |
2005年 | 229篇 |
2004年 | 182篇 |
2003年 | 141篇 |
2002年 | 134篇 |
2001年 | 118篇 |
2000年 | 104篇 |
1999年 | 120篇 |
1998年 | 96篇 |
1997年 | 79篇 |
1996年 | 94篇 |
1995年 | 71篇 |
1994年 | 80篇 |
1993年 | 61篇 |
1992年 | 58篇 |
1991年 | 51篇 |
1990年 | 46篇 |
1989年 | 40篇 |
1988年 | 29篇 |
1987年 | 29篇 |
1986年 | 21篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1957年 | 5篇 |
排序方式: 共有7451条查询结果,搜索用时 15 毫秒
1.
Qiang Yuan Bing-Qiang Qiao Yi-Qing Guo Yi-Zhong Fan Xiao-Jun Bi 《Frontiers of Physics》2021,16(2):24501
Recently the AMS-02 reported the precise measurements of the energy spectra of medium-mass compositions (Neon, Magnesium, Silicon) of primary cosmic rays, which reveal different properties from those of light compositions (Helium, Carbon, Oxygen). Here we propose a nearby source scenario, together with the background source contribution, to explain the newly measured spectra of cosmic ray Ne, Mg, Si, and particularly their differences from that of He, C, O. Their differences at high energies can be naturally accounted for by the element abundance of the nearby source. Specifically, the abundance ratio of the nearby source to the background of the Ne, Mg, Si elements is lower by a factor of ∼ 1.7 than that of the He, C, O elements. Such a difference could be due to the abundance difference of the stellar evolution of the progenitor star or the acceleration process/environment, of the nearby source. This scenario can simultaneously explain the high-energy spectral softening features of cosmic ray spectra revealed recently by CREAM/NUCLEON/DAMPE, as well as the energy-dependent behaviors of the large-scale anisotropies. It is predicted that the dipole anisotropy amplitudes below PeV energies of the Ne, Mg, Si group are smaller than that of the He, C, O group, which can be tested with future measurements. 相似文献
2.
3.
近年来,二维层状材料由于其丰富的材料体系和独特的物理化学性质而受到人们的广泛关注.后摩尔时代要求器件高度集成化,大面积、高质量的二维材料可以保证器件中结构和电子性能的连续性.要实现二维材料工业级别的规模化生产,样品的可控制备是其前提.化学气相沉积是满足上述要求的一种强有力的方法,已广泛应用于二维材料及其复合结构的生长制备.但是要实现多种二维材料大尺寸以至晶圆级的批量制备仍然是很困难的,因此,需要进一步建立对各种二维材料生长控制的系统认识.本文基于材料生长机理分析了化学气相沉积反应中的物质运输、成核、产物生长过程对二维材料尺寸的影响,以及如何通过调控这些过程实现二维材料大面积薄膜的可控制备.通过对目前研究成果的总结分析,讨论了如何进一步实现二维材料的高质量大面积制备. 相似文献
4.
Hu Yuanyuan Ji Wenxuan Qiao Jinjuan Li Heng Zhang Yun Luo Jun 《Journal of fluorescence》2021,31(5):1379-1392
Journal of Fluorescence - Although carbon dots (CDs) as fluorescent sensors have been widely exploited, multi-component detection using CDs without tedious surface modification is always a... 相似文献
5.
Rational Design of Two-Dimensional Magnetic Chromium Borides Based on First-Principles Calculation 下载免费PDF全文
Two-dimensional(2D) magnetic materials have been experimentally recognized recently,however,the Curie temperatures(TC) of known 2D systems are quite low.Generally,magnetic systems can be seen as constituent magnetic elements providing spins and the non-magnetic elements providing frameworks to host the magnetic elements.Short bond lengths between the magnetic and non-magnetic elements would be beneficial for strong magnetic interactions and thus high TC.Based on this,we propose to combine the magnetic element Cr and the non-magnetic element boron to design novel 2D magnetic systems.Using our self-developed software package IM2 ODE,we design a series of chromium-boride based 2D magnetic materials.Nine stable magnetic systems are identified.Among them,we find that CrB4-Ⅰ,CrB4-Ⅱ and CrBs-Ⅰ with common structural units [CrB8] are ferromagnetic metals with estimated TC of 270 K,120 K and 110 K,respectively.On the other hand,five CrB3 phases with structural units [Cr2B12] are antiferromagnetic metals.Additionally,we also find one antiferromagnetic semiconductor CrB2-Ⅰ.Our work may open new directions for identifying 2D magnetic systems with high TC. 相似文献
6.
Simulation of nuclide migration in a middle- and low-level radioactive waste repository based on GMS
Wang Litao Cheng Jianfeng Bao Chenyang Wang Yanhui Jiang Qiao Pan Yuelong Liu Yu Hong Tao Tuo Xianguo Leng Yangchun 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2159-2167
Journal of Radioanalytical and Nuclear Chemistry - Groundwater is the most important factor contributing to the diffusion and migration of radionuclides in the repository. In this paper, the... 相似文献
7.
利用9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)和马来酸酐(MA)对淀粉进行改性得到磷化淀粉(DOPOMASt),通过红外光谱(FTIR)、核磁共振谱(1H-NMR)和X射线光电子能谱(XPS)确定其结构.利用DOPOMASt作为碳源,与聚磷酸铵(APP)复配后通过熔融共混制备了阻燃聚乳酸(PLA)复合材料.采用垂直燃烧(UL-94)、极限氧指数(LOI)、热重分析(TGA)研究DOPOMASt对PLA的阻燃性能和热性能的影响.利用扫描电子显微镜(SEM)观察阻燃剂在PLA中的分散和燃烧后残炭的微观形貌,同时采用TG-IR联用技术对PLA复合材料热降解气相产物进行分析.结果表明,DOPOMASt促进APP在PLA中分散均匀,当DOPOMASt和APP质量比为1∶1,总质量为10%时,LOI达到26.0%且通过UL-94 V0测试.DOPOMASt与APP协效阻燃促进PLA树脂成碳,形成更加致密的炭层并减少可燃气体的产生,赋予PLA良好的阻燃性能. 相似文献
8.
Efficient,robust and cost-effective electrocatalysts that catalyze hydrogen evolution/oxidation reaction(HER/HOR)in alkaline media are highly demanded.Recently,single-atom catalysts(SACs)have emerged as new promising candidates;however,the rational design of supports and the optimization of coordination environment between supports and metal atoms are challenging.In this work,we successfully fabricate atomically dispersed ruthenium(Ru)species,which are strongly coordinated by N and S dual heteroatoms on holey graphene(RuSA/NSG),as an excellent bifunctional catalyst for HER/HOR.In alkaline media,the developed catalyst exhibits high catalytic performance with a low overpotential of 57.3 mV to drive a current density of 10 mA cm-1 for HER,and its mass activity is about 5.8 times higher than that of commercial Pt/C and Ru/C catalysts at an overpotential of 100 mV.Similarly,considerable HOR performance of Ru SA/NSG is verified to be superior to Pt/C and Ru/C.Furthermore,X-ray-based spectroscopy measurements and density-functional theory calculations have confirmed that,compared with Ru–N4,the tailored Ru–N4–S2 with nearby S dopants can act as more active centers to greatly accelerate the sluggish HER/HOR kinetics in alkaline media.The present work provides a new atomic-level engineering strategy to modulate catalytic activities of SACs via the coordination design using dual heteroatoms on the carbon support. 相似文献
9.
Xiangli Qian Huiying Sun Tianlu Chen Danzengluobu Youliang Feng Qi Gao Quanbu Gou Yiqing Guo Hongbo Hu Mingming Kang Haijin Li Cheng Liu Maoyuan Liu Wei Liu Bingqiang Qiao Xu Wang Zhen Wang Guangguang Xin Yuhua Yao Qiang Yuan Yi Zhang 《Frontiers of Physics》2022,17(6):64602
The High Altitude Detection of Astronomical Radiation (HADAR) experiment is a refracting terrestrial telescope array based on the atmospheric Cherenkov imaging technique. It focuses the Cherenkov light emitted by extensive air showers through a large aperture water-lens system for observing very-high-energy γ-rays and cosmic rays. With the advantages of a large field-of-view (FOV) and low energy threshold, the HADAR experiment operates in a large-scale sky scanning mode to observe galactic sources. This study presents the prospects of using the HADAR experiment for the sky survey of TeV γ-ray sources from TeVCat and provids a one-year survey of statistical significance. Results from the simulation show that a total of 23 galactic point sources, including five supernova remnant sources and superbubbles, four pulsar wind nebula sources, and 14 unidentified sources, were detected in the HADAR FOV with a significance greater than 5 standard deviations (σ). The statistical significance for the Crab Nebula during one year of operation reached 346.0 σ and the one-year integral sensitivity of HADAR above 1 TeV was ~1.3%–2.4% of the flux from the Crab Nebula. 相似文献
10.
采用态平均(CASSCF)/高度相关多参考组(MRCI)方法,对N2分子A3Σu+、B3Пg、C3Пu电子态的势能、跃迁偶极矩进行了高度相关的精确计算.计算的势能在平衡位置附近与RKR拟合的势能曲线非常一致,获得的跃迁偶极矩与已有实验值符合很好。首次对A3Σu+、B3Пg、C3Пu电子态的振转光谱常数随振动量子数v的变化进行系统定量计算,其结果与已有的实验观测数据相符.同时,获得了N2分子第一正带系的0-1、0-2、1-0、1-2、1-3、2-0、2-1、2-3、3-0、3-1和3-2光谱带分别在300,3000,6000,10000K时的谱线强度,如1-0带在3000,6000,10000K时的高温谱线带强度分别为1.58543×10-16 cm-1/(分子 cm-2)、6.07889×10-17 cm-1/(分子 cm-2)和2.3781×10-17 cm-1/(分子 cm-2).这些结果对N2分子进一步的理论研究、实际应用和高温大气的建模与研究具都有一定的参考价值. 相似文献