全文获取类型
收费全文 | 1440篇 |
免费 | 32篇 |
国内免费 | 5篇 |
专业分类
化学 | 926篇 |
晶体学 | 10篇 |
力学 | 48篇 |
数学 | 87篇 |
物理学 | 406篇 |
出版年
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2016年 | 23篇 |
2015年 | 29篇 |
2014年 | 23篇 |
2013年 | 62篇 |
2012年 | 90篇 |
2011年 | 81篇 |
2010年 | 37篇 |
2009年 | 46篇 |
2008年 | 50篇 |
2007年 | 34篇 |
2006年 | 51篇 |
2005年 | 52篇 |
2004年 | 48篇 |
2003年 | 49篇 |
2002年 | 33篇 |
2001年 | 41篇 |
2000年 | 27篇 |
1999年 | 27篇 |
1998年 | 17篇 |
1997年 | 27篇 |
1996年 | 30篇 |
1995年 | 17篇 |
1994年 | 28篇 |
1993年 | 21篇 |
1992年 | 30篇 |
1991年 | 25篇 |
1990年 | 17篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 10篇 |
1982年 | 22篇 |
1981年 | 32篇 |
1980年 | 15篇 |
1979年 | 19篇 |
1978年 | 27篇 |
1977年 | 23篇 |
1976年 | 19篇 |
1975年 | 24篇 |
1974年 | 11篇 |
1972年 | 8篇 |
1970年 | 13篇 |
1969年 | 13篇 |
1932年 | 8篇 |
排序方式: 共有1477条查询结果,搜索用时 15 毫秒
981.
Spin polarized photoemission by optical spin orientation is a simple and elegant means to increase the resolution of photoelectron spectroscopy. This is demonstrated by the experimental observation of the presence of the spin-orbit splitting of the top valence bands of silicon at Γ, which is known to amount to 44 meV only. 相似文献
982.
Application of spontaneous Raman and Rayleigh scattering and 2D LIF for the characterization of a turbulent CH4/H2/N2 jet diffusion flame 总被引:1,自引:0,他引:1
4 /H2/N2 diffusion flame. Important aspects of the measuring technique, such as accuracy, cross talk between different Raman bands,
and the correction procedure for background from laser-induced fluorescence are discussed. In addition, a 2D LIF and Rayleigh
imaging system were used to study the structures of OH, CH, NO, and temperature distributions in the flame. A comparison between
two different CH detection schemes is presented. A main goal of the investigations was a detailed and accurate characterization
of the investigated flame as well as the study of experimental techniques. Joint pdfs of the temperature and major species
concentrations were determined at nearly 100 measuring locations covering the complete flame. Parts of the results are presented
in the paper in order to discuss effects of differential diffusion, flame extinction, and interaction between flow field and
chemistry. The measured data sets which are available on the Internet are well suited for testing and validating mathematical
flame models.
Received: 8 July 1997/Revised version: 23 October 1997 相似文献
983.
Matthias Ernst Aswin Verhoeven Beat H. Meier 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,130(2):176-185
We have investigated the carbon line shape of solid adamantane under high-speed magic-angle sample spinning (MAS) acquired without proton decoupling. The CH-group shows a spinning-speed-dependent line broadening while the CH2-group consists of a spinning-speed-independent sharp component and a spinning-speed-dependent broader part. These phenomena can be explained by self-decoupling of theJ-interaction due to proton spin diffusion. Such a self-decoupling process can be described by a magnetization exchange process between the multiplet lines. Changing the spin-diffusion rate constant by off-resonance irradiation of the protons allows us to observe the full range from slow exchange to coalescence to fast exchange of the carbon spectra. One of the multiplet components in the CH2-group corresponds to a group spin of the protons of zero and therefore does not couple to the other protons. This gives rise to the sharp central line. The magnetization exchange rate constant between the different multiplet lines can be determined from the spectra and is a measure for the spinning-speed-dependent proton spin-diffusion rate constant. Even at an MAS speed of 30 kHz, proton spin diffusion is still observable despite the relatively weak intermolecular proton dipolar-coupling network in adamantane which results in a static proton line width of only 14 kHz (full width at half height). 相似文献
984.
985.
J. G. Meier P. Rudquist A. S. Petrenko J. W. Goodby S. T. Lagerwall 《Liquid crystals》2002,29(2):179-189
By studying the optical textures and the field-induced effects of the recently discovered TGBC A phase we have developed a qualitative model of the microscopic organization of the phase. Inside the smectic blocks, the molecular tilt plane of the local anticlinic structure is perpendicular to the helix of the TGBC A phase. The grain boundaries consist of a regular lattice of +1/2 and -1/2 dispirations; i.e. unit screw dislocations combined with half unit disclinations. Whereas all screw dislocations have the same sign, the sign of the half unit disclinations alternates in adjacent dispirations. Hence, in the grain boundaries the molecular tilt plane between adjacent dispirations is alternately parallel and perpendicular to the TGB helix. 相似文献
986.
987.
988.
989.
990.