全文获取类型
收费全文 | 10800篇 |
免费 | 2015篇 |
国内免费 | 1291篇 |
专业分类
化学 | 8212篇 |
晶体学 | 108篇 |
力学 | 609篇 |
综合类 | 119篇 |
数学 | 1335篇 |
物理学 | 3723篇 |
出版年
2024年 | 30篇 |
2023年 | 222篇 |
2022年 | 333篇 |
2021年 | 427篇 |
2020年 | 546篇 |
2019年 | 449篇 |
2018年 | 414篇 |
2017年 | 385篇 |
2016年 | 549篇 |
2015年 | 598篇 |
2014年 | 667篇 |
2013年 | 823篇 |
2012年 | 998篇 |
2011年 | 1061篇 |
2010年 | 758篇 |
2009年 | 690篇 |
2008年 | 710篇 |
2007年 | 651篇 |
2006年 | 590篇 |
2005年 | 429篇 |
2004年 | 353篇 |
2003年 | 250篇 |
2002年 | 279篇 |
2001年 | 189篇 |
2000年 | 186篇 |
1999年 | 194篇 |
1998年 | 150篇 |
1997年 | 160篇 |
1996年 | 137篇 |
1995年 | 139篇 |
1994年 | 114篇 |
1993年 | 119篇 |
1992年 | 84篇 |
1991年 | 66篇 |
1990年 | 70篇 |
1989年 | 42篇 |
1988年 | 41篇 |
1987年 | 40篇 |
1986年 | 14篇 |
1985年 | 32篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1977年 | 6篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1972年 | 11篇 |
1971年 | 6篇 |
1969年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
The spin-locking mechanism of the spin I=3/2 quadrupolar nuclei under magic angle spinning (MAS) has been theoretically and experimentally investigated, and the criterion of adiabatic passage around zero-crossings of the quadrupole splitting was inferred from the time-dependent Shrödinger equation in this article. The theory, numerical simulations, and experiments conducted in this work all indicated that second-order quadrupole interaction and off-resonance play important roles in the spin-locking of the quadrupolar nuclei, and they were responsible for the great loss of the spin-locking signals. The spin-locking for a spin I=3/2 nucleus might be achieved by minimizing the effect of the second-order quadrupole interaction by using a radio frequency (RF) offset. This offset was realized by setting the RF to the opposite position of the isotropic second-order quadrupolar shift of single quantum coherences. 相似文献
912.
Moore CI Krushelnick K Ting A Burris HR Hubbard RF Sprangle P 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(1):788-792
Low energy electron beams (E approximately 300 keV) generated in a self-modulated laser wakefield accelerator experiment were observed to filament and be deflected away from the laser axis forming radial jets in the electron beam profile. At higher energies (E>900 keV), the filamentation and jets were suppressed and smooth electron beams copropagating with the laser were observed. The observed electron beam filamentation likely results from laser beam filamentation in the plasma due to relativistic self-focusing effects. The radial jets of low energy electrons are likely caused by transverse ejection of the electrons due to the radial structure of the wakefield and space charge deflection of electrons as they exit the laser focus. 相似文献
913.
914.
不同条件下,在单晶硅基片上沉积了含氮氟化类金刚石(FN-DLC)薄膜.原子力显微(AFM)形貌显示,掺N后,薄膜变得致密均匀.傅里叶变换吸收红外光谱(FTIR)表明,随着r(r=N2/[N2+CF4+CH4])的增大薄膜中C—H键的逐渐减少,C〖FY=,1〗N和C≡N键含量逐渐增加.X射线光电子能谱(XPS)的C1s和N1s峰拟合结果发现,N掺入导致在薄膜中出现β-C3N4和a-CNx(x=1,2,3)成分.Roman散射谱的G峰向高频方向位移和峰值展宽等证明:随着r的增大,薄膜内sp2键态含量增加.
关键词:
氟化类金刚石膜
键结构
氮掺杂 相似文献
915.
Wang Xiaodan Zhao Zhiwei Xu Xiaodong Jiang Benxue Tang Huili Wang Jingya Xu Jun Deng Peizhen 《光学学报》2007,(8)
采用提拉法生长Y3Al5O12(YAG)晶体和Yb3 掺杂原子数分数分别为5%,10%,15%,20%,25%,50%和100%的Yb∶Y3Al5O12(Yb∶YAG)晶体。系统表征和分析了Yb3 掺杂浓度对拉曼光谱的影响。随着Yb3 掺杂浓度的增加,晶体的振动模式没有明显的变化,晶体结构没有改变;在370 cm-1和785 cm-1附近,振动吸收峰的半峰全宽逐渐增大。分析得出,Yb3 掺杂浓度对晶体的晶格、对称性、荧光寿命均有影响,从而可能影响到晶体的光谱和激光性能。 相似文献
916.
应用群论及原子分子反应静力学方法推导了SiO2分子的电子态及其离解极限,采用B3P86方法,在6-311G**水平上,优化出SiO2基态分子稳定构型为单重态的C2V构型,其平衡核间距Re=RSi-O=0.1587 nm,∠OSiO=111.2°,能量为-440.4392 a.u..同时计算出基态的简正振动频率:对称伸缩振动频率v(B2)=945.4cm-1,弯曲振动频率v(A1)=273.5 cm-1和反对称伸缩振动频率v(A1)=1362.9cm-1.在此基础上,使用多体项展式理论方法,导出了基态SiO2分子的全空间解析势能函数,该势能函数准确再现了SiO2(C2V)平衡结构. 相似文献
917.
918.
A protocol of quantum secret sharing between multiparty and multiparty with four states was presented. It was shown that this
protocol can nullify the Trojan horse attack with a multi-photon signal, the fake-signal attack with Einstein-Podolsky-Rosen
pairs, the attack with single photons, and the attack with invisible photons. In addition, the upper bounds of the average
success probabilities were given for dishonest agent eavesdropping encryption using the fake-signal attack with any two-particle
entangled states.
Supported by the National Natural Science Foundation of China (Grant No. 10671054), the Key Project of Science and Technology
Research of Education Ministry of China (Grant No. 207011) and the Natural Science Foundation of Hebei Province, China (Grant
Nos. A2005000140 and 07M006) 相似文献
919.
C.V. Subba Reddy Z.R. Deng Q.Y. Zhu Y. Dai J. Zhou W. Chen S.-I. Mho 《Applied Physics A: Materials Science & Processing》2007,89(4):995-999
Molybdenum trioxide (MoO3) and PPyxMoO3 (x=0.5 and 1) nanobelts were obtained by the simple hydrothermal process from MoO3 sol. The morphology and structure of the samples were characterized using X-ray diffractometry (XRD), Fourier transformation
infrared spectroscopy (FTIR), Raman spectra, SEM and AFM. The results show that the H atoms in polypyrrole are H-bonded with
the O atoms in the Mo=O bonds of MoO3 nanobelts. Using the electrolyte, we fabricated electrochemical cells with a configuration of Li/(LiPF6+EC+DMC)/(MoO3+acetyleneblack+PTFE) and studied discharge profiles.
PACS 81.07.BC; 81.05.Je; 82.47.Aa; 82.45.Fk; 82.45.Gj 相似文献
920.