全文获取类型
收费全文 | 649346篇 |
免费 | 5709篇 |
国内免费 | 1912篇 |
专业分类
化学 | 334628篇 |
晶体学 | 9359篇 |
力学 | 31973篇 |
综合类 | 24篇 |
数学 | 82811篇 |
物理学 | 198172篇 |
出版年
2021年 | 5748篇 |
2020年 | 6260篇 |
2019年 | 7063篇 |
2018年 | 9205篇 |
2017年 | 9372篇 |
2016年 | 13260篇 |
2015年 | 7576篇 |
2014年 | 12239篇 |
2013年 | 29111篇 |
2012年 | 22722篇 |
2011年 | 27366篇 |
2010年 | 19889篇 |
2009年 | 19821篇 |
2008年 | 25628篇 |
2007年 | 25419篇 |
2006年 | 23422篇 |
2005年 | 21060篇 |
2004年 | 19489篇 |
2003年 | 17514篇 |
2002年 | 17240篇 |
2001年 | 18550篇 |
2000年 | 14334篇 |
1999年 | 11090篇 |
1998年 | 9431篇 |
1997年 | 9234篇 |
1996年 | 8738篇 |
1995年 | 7836篇 |
1994年 | 7767篇 |
1993年 | 7472篇 |
1992年 | 8041篇 |
1991年 | 8536篇 |
1990年 | 8007篇 |
1989年 | 7908篇 |
1988年 | 7730篇 |
1987年 | 7542篇 |
1986年 | 7212篇 |
1985年 | 9440篇 |
1984年 | 9759篇 |
1983年 | 8137篇 |
1982年 | 8572篇 |
1981年 | 7996篇 |
1980年 | 7693篇 |
1979年 | 8122篇 |
1978年 | 8409篇 |
1977年 | 8270篇 |
1976年 | 8235篇 |
1975年 | 7913篇 |
1974年 | 7692篇 |
1973年 | 8023篇 |
1972年 | 5657篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
V. G. Domelunksen I. R. Krylov G. A. Polyanskaya M. A. Tsygankov 《Optics and Spectroscopy》2004,97(1):136-140
An interference method for measuring certain parameters of a substance in the vicinity of the critical state is proposed. The essence of the method is to decipher the interference pattern arising upon grazing incidence of a laser beam on a curved liquid-vapor interface. The deciphering allows one to determine the difference between the refractive indices of the two phases and the scaling factor of the wetting meniscus shape. This, in turn, makes it possible to calculate the critical exponents for the temperature dependences of the surface tension and the difference in the densities of the two phases. The ratio of these critical exponents for xenon, measured in the paper, is 3.81±0.03. 相似文献
992.
The synthesis of a specific isotopomer, C6D4H(ortho)-H(ortho)D4C6 of biphenyl is reported. The intramolecular dipolar coupling of the protons leads to a well-resolved single-crystal proton
nuclear magnetic resonance (NMR) spectrum and allows one to study the dynamics of the phenyl rings in a unique way. At room
temperature and above, the most conspicuous dynamical mode consists of 180° ring flips. The present data together with previous
measurements of the total flip rate allow us to conclude that the rings flip almost exclusively independently of each other.
Between the incommensurate (IC) phase transition of biphenyl at 38 K andT=250 K, the prominent namical mode consists of oscillatory twists ϕ(t) of the two rings. The data allow us to infer the mean square, (φ2), of these twists. (φ2) is found to grow linearly withT for 50<T<200 K. From the slope of (φ2) vs.T the frequency (the wave number[(v)\tilde]\tilde v) is derived. The result is[(v)\tilde] = 20\tilde v = 20 cm−1. ForT<38 K, the spectra give direct evidence of the IC phase transition and its nature (stripelike rather than quiltlike). The
temperature dependence of the magnitude of the order parameter of the IC phase is obtained. 相似文献
993.
A. M. Povolotsky V. B. Priezzhev Chin-Kun Hu 《Journal of statistical physics》2003,111(5-6):1149-1182
An asymmetric stochastic process describing the avalanche dynamics on a ring is proposed. A general kinetic equation which incorporates the exclusion and avalanche processes is considered. The Bethe ansatz method is used to calculate the generating function for the total distance covered by all particles. It gives the average velocity of particles which exhibits a phase transition from an intermittent to continuous flow. We calculated also higher cumulants and the large deviation function for the particle flow. The latter has the universal form obtained earlier for the asymmetric exclusion process and conjectured to be common for all models of the Kardar–Parisi–Zhang universality class. 相似文献
994.
For an arbitrary finite time interval, the unique solvability of a linear half-space problem is obtained in Hölder classes of functions. The problem arises as the result of the linearization of a free boundary problem for the Navier--Stokes system governing the unsteady motion of a finite mass of a compressible fluid. The boundary conditions in the linear problem are noncoercive because of the surface tension acting on the free boundary. This fact presents the main difficulty in the problem, while the differential system in itself is parabolic in the sense of Petrovskii. The principal idea of the investigation is to reduce the noncoercive problem to a coercive one with zero coefficient of the surface tension. Bibliography: 6 titles. 相似文献
995.
O. Wibbelhoff C. Meier A. Lorke P. Schafmeister A. D. Wieck 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):516
We use frequency-dependent capacitance–voltage spectroscopy to study the dynamic charging of self-assembled InAs quantum dots. With increasing frequency, the AC charging becomes suppressed, beginning with the low-energy states. By applying an in-plane magnetic field, we generate an additional magnetic confinement that alters the tunneling barrier and hence the charging dynamics. In traveling through the potential barrier, the electrons acquire an additional momentum k0, proportional to the magnetic field B. As the tunneling is enhanced, when k0 matches the maximum of the electronic wave function Ψ (in momentum representation), we are able to map out the shape of Ψ by varying B. 相似文献
996.
997.
D. Chithrani R. L. Williams J. Lefebvre P. J. Poole G. C. Aers 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):290
We discuss the preparation and spectroscopic characterisation of a single InAs/InP quantum dot suitable for long-distance quantum key distribution applications around λ=1.55 μm. The dot is prepared using a site-selective growth technique which allows a single dot to be deposited in isolation at a controlled spatial location. Micro-photoluminescence measurements as a function of exciton occupation are used to determine the electronic structure of the dot. Biexciton emission, shell filling and many-body re-normalization effects are observed for the first time in single InAs/InP quantum dots. 相似文献
998.
J. Wang J. Kono A. Oiwa H. Munekata C. J. Stanton 《Superlattices and Microstructures》2003,34(3-6):563
We have carried out an ultrafast time-resolved differential reflectivity study of a ferromagnetic semiconductor InGaMnAs and made a systematic comparison with low-temperature grown and high-temperature grown InGaAs reference films. Very short carrier lifetimes (2 ps) were observed in InGaMnAs and the low-temperature grown InGaAs film, but not in the high-temperature grown InGaAs film. We attribute the short lifetimes to carrier trapping by mid-gap states introduced during low-temperature MBE growth. Furthermore, at long times, we observed periodic oscillations in the differential reflectivity signal with period 20 ps, which we interpret as coherent acoustic phonons. 相似文献
999.
1000.
CRACK DETECTION THROUGH WAVELET TRANSFORM FOR A RUN-UP ROTOR 总被引:1,自引:0,他引:1
A.S. SEKHAR 《Journal of sound and vibration》2003,259(2):461-472