全文获取类型
收费全文 | 1117篇 |
免费 | 90篇 |
国内免费 | 16篇 |
专业分类
化学 | 868篇 |
晶体学 | 1篇 |
力学 | 16篇 |
数学 | 58篇 |
物理学 | 280篇 |
出版年
2024年 | 29篇 |
2023年 | 72篇 |
2022年 | 135篇 |
2021年 | 76篇 |
2020年 | 22篇 |
2019年 | 21篇 |
2018年 | 21篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 19篇 |
2014年 | 37篇 |
2013年 | 18篇 |
2012年 | 89篇 |
2011年 | 148篇 |
2010年 | 45篇 |
2009年 | 27篇 |
2008年 | 91篇 |
2007年 | 85篇 |
2006年 | 75篇 |
2005年 | 49篇 |
2004年 | 32篇 |
2003年 | 11篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 4篇 |
1993年 | 15篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1986年 | 1篇 |
排序方式: 共有1223条查询结果,搜索用时 78 毫秒
81.
Insight into influence of thermodynamic coefficients on transient negative capacitance in Zr-doped HfO2 ferroelectric capacitors
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yuan-Yuan Zhang 《中国物理 B》2021,30(12):127701-127701
We study the influence of the thermodynamic coefficients on transient negative capacitance for the Zr-doped HfO2 (HZO) ferroelectric capacitors by the theoretical simulation based on the Landau-Khalatnikov (L-K) theory and experimental measurement of electrical properties in the resistor-ferroelectric capacitor (R-FEC) circuit. Our results show that the thermodynamic coefficients α, β and γ also play a key role for the transient NC effect besides the viscosity coefficient and series resistor. Moreover, the smaller coefficients α and β, the more significant the transient NC effect. In addition, we also find that the thermodynamic process of transient NC does not obey the generally accepted viewpoint of Gibbs free energy minimization. 相似文献
82.
Danqing Zhou 《中国物理 B》2021,30(11):116106-116106
Laser-accelerated ion beams (LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here we explore an application of using laser-accelerated ion beams to prepare graphene. The pulsed LIBs produced a great instantaneous beam current and thermal effect on the SiC samples with a shooting frequency of 1 Hz. In the experiment, we controlled the deposition dose by adjusting the number of shootings and the irradiating current by adjusting the distance between the sample and the ion source. During annealing at 1100 ℃, we found that the 190 shots ion beams allowed more carbon atoms to self-assemble into graphene than the 10 shots case. By comparing with the controlled experiment based on ion beams from a traditional ion accelerator, we found that the laser-accelerated ion beams could cause greater damage in a very short time. Significant thermal effect was induced when the irradiation distance was reduced to less than 1 cm, which could make partial SiC self-annealing to prepare graphene dots directly. The special effects of LIBs indicate their vital role to change the structure of the irradiation sample. 相似文献
83.
Facile synthesis of a melt-spinnable polyborazine from asymmetric alkylaminoborazine 总被引:1,自引:0,他引:1
Yong Peng Lei Ying De Wang Yong Cai Song Yi He Li Hao Wang Cheng Deng Zheng Fang Xie 《中国化学快报》2010,21(9):1079-1082
<正>A novel asymmetric alkylaminoborazine monomer,2-propylamino-4,6-bis(methylamino)borazine,was synthesized for the first time,and directly polymerized to give a melt-spinnable polyborazine(PBN).This asymmetric alkylaminoborazine was synthesized by an aminolysis reaction of 2,4,6-trichloroborazine(TCB) with different amines under mild conditions.This route turns out to be much cheaper and simpler than the conventional routes.The chemical composition,structure,molecular weights and ceramic yield were investigated by EA,FTIR,NMR,GPC and TG analysis.The PBN exhibits suitable rheological property for melt-spinning, which suggests that it is a potential precursor for BN fibers. 相似文献
84.
By controlling the reflux time and the quantity of the shell materials, different sizes of thioglycollic acid (TGA) modified
CdTe/CdSe core/shell quantum dots were synthesized in aqueous solution. This type of QDs was used for sensitive and selective
determination of ascorbic acid in commercial tablets. Under optimal conditions, a good linearity was observed between the
relative fluorescence (FL) intensity and the concentration of ascorbic acid in the range of 4.0 to 64.0 μg/mL with a correlation
coefficient of 0.9968. The limit of detection was 2.4 μg/mL. This method was applied to the determination of the ascorbic
acid in Vitamin C tablets and Vitamin C Yinqiao pills, and satisfactory results were obtained. 相似文献
85.
A stability analysis for the resistive wall mode is studied in the presence of trapped energetic particles (EPs). When the EPs' beta exceeds a critical value, a fishbonelike bursting mode (FLM) with an external kink eigenstructure can exist. This offers the first analytic interpretation of the experimental observations [Phys. Rev. Lett. 103, 045001 (2009)]. The mode-particle resonances for the FLM and the q=1 fishbone occur in different regimes of the precession frequency of EPs. In certain ranges of the plasma rotation speed and the EPs' beta, a mode conversion can occur between the resistive wall mode and FLM. 相似文献
86.
87.
基于抽取和连续投影算法的可见近红外光谱变量筛选 总被引:1,自引:0,他引:1
大多数短波CCD硅检测器为2 048或3 648像元,相邻波长间隔小,预处理算法对其适用性差.本文在600.09~980.47 nm光谱范围内,采用等间隔抽取方法重构光谱矩阵.经不同光谱预处理后,分别采用遗传算法(GA)和连续投影算法(SPA),筛选偏最小二乘法(PLS)建模变量.采用留一法交叉验证评价模型的预测能力,... 相似文献
88.
铕与4-(4-吡啶甲酰基)苯甲酸配合物的合成与荧光性能研究 总被引:2,自引:0,他引:2
以Eu3+为中心离子,4-(4-吡啶甲酰基)苯甲酸(HPFBA)、1,10-菲罗啉(Phen)和三苯基氧膦(TPPO)为配体,合成了新型配合物Eu(PFBA)3(H2O)4,Eu(PFBA)3Phen(H2O)3和Eu(PFBA)3TPPO(H2O)3(PFBA=4-(4-吡啶甲酰基)苯甲酸根).红外光谱表明,形成配合... 相似文献
89.
A simple sensor system for high spatial resolution distributed strain field measurement is proposed and demonstrated experimentally. The fiber loop ringdown technique combined with a linear chirped fiber Bragg grating is used to realize the high spatial resolution. A proof-of-concept distributed strain sensor with 2?mm spatial resolution is realized. The sensor network is also explored and researched experimentally. The proposed technique suggests a broad range of applications for real-time distributed physical parameter sensing, such as strain or temperature. 相似文献
90.
Gnetifolin L and O, Two Dimeric Stilbenes from Gnetum Montanum 总被引:1,自引:0,他引:1
GnetuI)1monlanlImgr0wsinthes0uthernpart0fChinaandhasbeenusedf0rthetreatment0fbronchitisandarthritisinf0lkmedicinel.Previously,aninvestigationofthisspeciesledt0theis0lationofs0meaIkal0idsanddibenzyletherderivatives2.lnourstudies,tenc0mp0nentsincludingresveratr0l,is0rhapontigenin,daucoster0l,O-sitosterol,stearicacid,gnetif0linE,gnet0l,is0rhapontigenin-3-O-6-gluc0pyra(-)8-viniferinandgnetifolinCwere0btainedfromthisplant'.Inthefurtherstudy,f0urnewdimericstilbenesnamedgnetif0IinMandN',gnetifoli… 相似文献