全文获取类型
收费全文 | 389篇 |
免费 | 47篇 |
国内免费 | 16篇 |
专业分类
化学 | 62篇 |
晶体学 | 12篇 |
综合类 | 1篇 |
物理学 | 377篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 11篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 10篇 |
2009年 | 72篇 |
2008年 | 64篇 |
2007年 | 51篇 |
2006年 | 30篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 22篇 |
2002年 | 26篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 19篇 |
1998年 | 19篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1985年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有452条查询结果,搜索用时 262 毫秒
31.
Improving the specularity of magnetic mirrors for atoms 总被引:1,自引:0,他引:1
G. Zabow M. Drndić J.H. Thywissen K.S. Johnson R.M. Westervelt M. Prentiss 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):351-359
An array of anti-parallel current-carrying wires creates an inhomogeneous magnetic field capable of reflecting neutral atoms.
We present analytical and numerical analyses of the magnetic field produced by such an array, and describe methods for reducing
the resulting rms angular deviation from specular reflection to less than 0.1 mrad. Careful choice of cross-sectional wire
profiles is shown to dramatically improve specularity of reflection close to the surface. Additionally, we find that the specularity
depends on whether the number of wires in the mirror is even or odd, and that there exists an optimal turning height above
the surface that maximizes the specularity of reflection from the mirror.
Received 16 November 1998 相似文献
32.
A. Narayanan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(1):13-22
An effective four-level system around the D2 line
of 85Rb at room temperature, is experimentally investigated
by fluorescent studies
under the action of two driving fields L1 and L2.
This system exhibits unique features in fluorescence as a function of frequency
separation between L1 and L2. In particular, at two-photon resonance,
when the Rabi frequency of L1 exceeds that of L2,
signatures of Electromagnetically Induced Transperancy effect (EIT)
arising from the three-level Λ sub-system
is present as a sub-natural dip in fluorescence from the fourth level.
At comparable strengths of L1 and L2
the fluorescence features indicate a regime, where
the effects arising
from optical pumping and EIT effect due to ground hyperfine level coherence
coexist. We see in the coexistence regime, saturation
effects arising from difference frequency crossing (DFC) resonances and optical
pumping around the EIT window. At low strengths of L1, all signs of
coherence vanishes from the system and the fluorescent features result
from incoherent optical pumping through the
Autler-Townes split states of the excited state
hyperfine levels, which are split due to the stronger L2 laser.
The dominant role of the L1 laser in creating a robust transparency signal even
in the presence of an off-resonant excitation is brought out.
The results are supported by density matrix calculations. 相似文献
33.
利用中子飞行时间技术和BC501A液体闪烁探测器的粒子分辨特性,测量了0°方向、20 MeV氘束轰击厚金属铍靶反应产生的中子源能谱,测量的中子能谱范围为0.7~25.0 MeV。在60°方向放置芪晶体闪烁探测器,由刻度好的BC501A液体闪烁探测器归一校正后,用于中子源强度监测。利用Be(d, n) 反应中子源,采用单粒子灵敏度标定方法,实验标定了0.75~15.75 MeV能量范围内的薄膜闪烁探测器中子能量响应曲线,实验结果与蒙特卡罗模拟计算结果在8%的不确定度范围内一致。 相似文献
34.
Pure TiO2 and nitrogen doped titanium dioxide (N-TiO2) thin films were prepared by sol-gel method through spin coating on soda lime glass substrates. TiCl4 and urea were used as Ti and N sources in the sol. XRD results showed nitrogen doping has retarded anatase to rutile phase transformation. The doping also leads to a decrease in roughness of the samples from 4 nm (TiO2) to 1 nm (N-TiO2). However, surface analysis by statistical methods reveals that both surfaces have self-affine structure. Optical band gap of thin films was shifted from 3.65 eV (TiO2) to 3.47 eV (N-TiO2). Hydrophilic conversion and photocatalytic degradation properties of thin films were investigated and exhibited that N-TiO2 thin film has more preferable hydrophilicity and photocatalytic properties under UV illumination. 相似文献
35.
Adiabatic focusing of cold atoms in a blue-detuned laser standing wave is analyzed. It is shown that using repulsive light
forces that push atoms towards dark regions and thus minimizes heating, cold atoms can be adiabatically compressed by more
than an order of magnitude to yield background-free sub-10-nm (rms) spots. The optimal parameters for the atomic lens and
the maximal compression ratio are predicted using an analytic model and found to be in agreement with the exact results of
our Monte Carlo simulations. A combined adiabatic-coherent scheme is proposed and shown to yield 8.8 nm spot size even for
a thermal atomic beam.
Received: 1 October 1999 / Revised version: 13 December 1999 / Published online: 5 April 2000 相似文献
36.
Y. Kimura 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):175-184
In a magnetic field, Cs2 molecules were excited from the ground X1Σ+g(vX=0,JX=55) level to the D 1Σ+u(v=46,J=54) level by dissociation laser light linearly polarized parallel to the field, for which the magnetic sublevels were
degenerated and thus all the transitions between them were simultaneously stimulated. Probe laser light excited the dissociated
Cs 6p2P3/2 atomic fragments to 6p2D3/2 level and the resultant 6p2P1/2 - 6d2D3/2 emission was detected as the function of the wavelength of the probe light. The populations of the 6p2P3/2,mj magnetic sublevels were determined from the relative strengths of the
6p2P3/2,mj - 6d2D3/2,m'j
transitions induced by the probe light. Non-zero orientation O0 was found in the ensemble of dissociated Cs
6p2P3/2
atomic fragments. The orientation O0 increased as the magnetic field strength increased. It was demonstrated both experimentally and theoretically that the orientation
O0 was induced through the interference in the excitation and dissociation paths in the presence of an external magnetic field,
even when all degenerated transitions between the magnetic sublevels of the molecules are simultaneously excited by the light
linearly polarized parallel to the field. 相似文献
37.
Superhard materials have many industrial applications, wherever resistance to abrasion and wear are important. The synthesis of new superhard materials is one of the great challenges to scientists. We re-examined the phase diagram of the binary osmium-boron system and confirmed the existence of two hexagonal phases, OsB1.1, Os2B3, and an orthorhombic phase, OsB2. Almost nothing is known about the physical properties of osmium borides. Microhardness measurements show that OsB2 is extremely hard. Ab initio calculations show that this is due to formation of covalent bonds between boron atoms. OsB2 is also a low compressibility material. It can be used as hard coating. 相似文献
38.
S. Willmann A. Terenji J. Osterholz H.J. Schwarzmaier P. Hering 《Applied physics. B, Lasers and optics》2002,74(6):589-595
The aim of our studies was to develop a method to determine the absorption coefficient of a turbid medium in a reflection
geometry with small source–detector separations. Therefore, the time-integrated microscopic Beer–Lambert law (MBL) was modified
in order to obtain the absolute absorption coefficient from mean time of flight and dc-intensity measurements. The new technique
was evaluated using turbid phantoms having varying scattering (μs
′ between 0.2 and 2.2 mm-1) and absorbing properties (μa between 0.04 and 0.14 mm-1), comparable to many biological tissues at various source–detector separations between 3 and 11 mm. The measurements were
performed at a wavelength of 1064 nm. We found that this new method was able to determine the absolute absorption coefficient
of the selected phantoms with a standard error of less than 0.005 mm-1 over the range of optical properties investigated.
Received: 23 November 2001 / Revised version: 28 February 2002 / Published online: 14 May 2002 相似文献
39.
We describe a detector for metastable rare gas atoms which allows the investigation of transverse atomic beam distributions
on the single atom level with lateral dimensions of 1 m, which occur frequently in the field of atom optics. In contrast to existing detection techniques, the conversion step from
the metastable atom to an electron is separated from the charge amplification to improve spatial resolution. The conversion
is performed at a metal surface, which is followed by an electron-optical system imaging the electron distribution with a
proper magnification onto a single electron detection unit. The spatial resolution that we achieve with this technique is
on the order of 1 m, the temporal resolution on the order of 1 s. The application of the detector for atom interferometry is discussed.
Received: 22 May 1996 / Revised version: 21 June 1996 相似文献
40.
M. Koch X. Luo P. Mürtz W. Urban K. Mörike 《Applied physics. B, Lasers and optics》1997,64(6):683-688
15 N2 in a gas phase sample is described. The nitrogen is transformed by a microwave discharge into nitric oxide NO. The latter
is analyzed by recording both a 15NO and a 14NO Faraday LMR signal. The determination of the transformation rate from N2 into NO is described. The method of measurement and the achieved sensitivity (∼0.1 ppm 15N2≈4 nanomoles 15N2/litergas) of the spectrometer are discussed. An application in pharmacology, where 15N is used as a tracer for metabolism is indicated. First experiments with the exhalation of a rat show that the apparatus
is useful to give a new quality of results.
Received: 30 April 1996/Revised version: 29 July 1996 相似文献