全文获取类型
收费全文 | 417942篇 |
免费 | 3754篇 |
国内免费 | 1247篇 |
专业分类
化学 | 195419篇 |
晶体学 | 5751篇 |
力学 | 22393篇 |
综合类 | 24篇 |
数学 | 61848篇 |
物理学 | 137508篇 |
出版年
2021年 | 3233篇 |
2020年 | 3513篇 |
2019年 | 3996篇 |
2018年 | 12053篇 |
2017年 | 12727篇 |
2016年 | 10792篇 |
2015年 | 5000篇 |
2014年 | 7422篇 |
2013年 | 16395篇 |
2012年 | 16105篇 |
2011年 | 25020篇 |
2010年 | 17088篇 |
2009年 | 17083篇 |
2008年 | 22083篇 |
2007年 | 24828篇 |
2006年 | 12613篇 |
2005年 | 16061篇 |
2004年 | 12732篇 |
2003年 | 11721篇 |
2002年 | 10213篇 |
2001年 | 10871篇 |
2000年 | 8176篇 |
1999年 | 6200篇 |
1998年 | 5184篇 |
1997年 | 4987篇 |
1996年 | 4802篇 |
1995年 | 4111篇 |
1994年 | 4034篇 |
1993年 | 3934篇 |
1992年 | 4232篇 |
1991年 | 4463篇 |
1990年 | 4250篇 |
1989年 | 4161篇 |
1988年 | 3933篇 |
1987年 | 4088篇 |
1986年 | 3841篇 |
1985年 | 4843篇 |
1984年 | 4931篇 |
1983年 | 4134篇 |
1982年 | 4193篇 |
1981年 | 3900篇 |
1980年 | 3869篇 |
1979年 | 4203篇 |
1978年 | 4208篇 |
1977年 | 4135篇 |
1976年 | 4201篇 |
1975年 | 3946篇 |
1974年 | 3911篇 |
1973年 | 3962篇 |
1972年 | 2880篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
The ferromagnetic shape memory alloy with nominal composition Ni54Fe19Ga27 is investigated by Ac susceptibility and resistivity measurements. The alloy shows long-range ferromagnetic order below 290 K. The anomaly due to the martensitic transition is observed in the susceptibility and resistivity data in the temperature range around 220 K, which is associated with clear thermal hysteresis. Minor hysteresis loop technique was used to investigate the phase coexistence across the martensitic transition, and our analysis indicate that both martensite and austenite phases mutually coexist in the region of hysteresis. 相似文献
992.
The capability of a modern interpretation system for IR spectra has been tested, in which the process of structural assignment
is modelled by methods of fuzzy logic. Figures of merit were generated for different interpretation algorithms. These figures
of merit permit the validation as well as a comparison of independent interpretation systems. The influence of the sample
preparation practice onto the information content of the resulting spectrum has been evaluated as well. Automatically generated
band tables show only restricted reliability.
Received: 13 February 1997 / Revised: 1 April 1997 / Accepted: 3 April 1997 相似文献
993.
K. S. Birdi 《Colloid and polymer science》1997,275(6):561-566
The surface tension versus temperature data of homologous series of n-alkanes and n-alkenes is analyzed. Critical temperatures are shown to be predicted from these data, with a very high precision, after some
corrections are made. The corrections are shown to arise from the effect of the critical pressure on the extrapolated data
to surface tension approaching zero.
Received: 29 October 1996 Accepted: 13 December 1996 相似文献
994.
S. M. Dunaevskii A. L. Malyshev V. A. Trunov V. V. Popov 《Physics of the Solid State》1997,39(10):1636-1637
The results of investigating the temperature dependence of the resistivity, the differential magnetic susceptibility, and
the magnetoresistance of a partially substituted perovskite Sm1−x
SrxMnO3 (x=0.16–0.4) are presented. Colossal intrinsic magnetoresistance, reaching 90% in an external magnetic field of 30 kOe, is discovered
in the compound with x=0.30 at 77 K.
Fiz. Tverd. Tela (St. Petersburg) 39, 1831–1832 (October 1997) 相似文献
995.
S. Gukov 《JETP Letters》1997,65(8):694-700
The manifestly supersymmetric four-dimensional Wess-Zumino model with quenched disorder is considered at the one-loop level.
The infrared fixed points of a beta function form the moduli space ℳ=RP
2, where two types of phases are found: with and without replica symmetry. While the former phase possesses only a trivial
fixed point, this point become unstable in the latter phase, which may be interpreted as a spin glass phase.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 657–662 (25 April 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
996.
Auluck S.K.H. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(1):37-41
The validity of the snowplow model of plasma sheath propagation in a plasma focus (PF) and the localization of the magnetic field in the low density region behind the dense plasma sheath are two well-established experimental facts. It is shown that, when taken together, these two imply a deficiency in the momentum balance. The hypothesis that the current-carrying plasma layer is rotating while the dense plasma layer is not rotating is shown not only to resolve this momentum balance anomaly (MBA), but also to explain many observed phenomena in a unified manner 相似文献
997.
The relativistic four-quark equations are found in the framework of the dispersion relation technique. The behaviour of the low-energy four-particle amplitude is determined by its leading singularities in the pair invariant masses. The approximate solutions of these equations using the method based on the extraction of leading singularities of the amplitudes are obtained. The mass values of lowest exotic mesons are calculated. 相似文献
998.
It is shown that the potential perturbation that shifts a chosen standing wave in space is a block of potential barrier and well for every wave bump between neighbouring knots. The algorithms shifting the range of the primary localization of a chosen bound state in a potential well of finite width are as well applicable to the scattering functions if states of the continuous spectrum are considered as bound states normalized to unity but distributed on an infinite interval with vanishing density. The potential perturbations of the same type on the half-axis concentrate the scattering wave at the origin, thus creating a bound state embedded into the continuous spectrum (zero width resonance). 相似文献
999.
New effects are observed wherein the internal structure of the domain walls in a thin magnetic iron garnet film are modified
by the action of focused laser radiation. A single laser pulse with increasing power gives rise to the following: 1) displacement
of vertical Bloch lines in a domain wall; 2) generation of a pair of vertical Bloch lines on initially line-free walls; and,
3) an irreversible change in shape of a domain wall and the domain structure as a whole. The mechanism leading to the generation
and displacement of Bloch lines is connected with the motion of domain walls which is induced by a local change in the distribution
of demagnetizing fields as a result of a heating-induced decrease of the magnetization in the focal spot of the laser radiation.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 6, 398–402 (25 September 1997) 相似文献
1000.
Changes in thin zinc-sulfide films under the action of the γ-radiation of Co60 are studied by investigating electroluminescence spectra of terbium embedded in these films as a luminescent probe. It is
shown that changes in the relation of the intensities of bands, a decrease in their halfwidth and the background component,
and simplification of the spectrum are observed in a short-wave region of the Tb radiation spectrum that corresponds to5D3→7Fj transitions. The same modification of the radiation spectrum is characteristic of ZnS films whose crystalline structure is
ordered in the course of thermal annealing at a temperature of 350°C. Based on the analysis of the data obtained it is inferred
that irradiating the ZnS films with small radiation doses of 104–105 rad leads to the ordering of their crystalline structure due to the elimination of one of the types of structural defects.
Institute of Physics of Semiconductors, National Academy of Sciences of Ukraine, 45, Nauka Ave., Kiev-28, 252650. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 338–341, May–June, 1997. 相似文献