全文获取类型
收费全文 | 122417篇 |
免费 | 2086篇 |
国内免费 | 126篇 |
专业分类
化学 | 68641篇 |
晶体学 | 1482篇 |
力学 | 4013篇 |
综合类 | 2篇 |
数学 | 16510篇 |
物理学 | 33981篇 |
出版年
2022年 | 854篇 |
2021年 | 1317篇 |
2020年 | 1625篇 |
2019年 | 1700篇 |
2018年 | 2530篇 |
2017年 | 2536篇 |
2016年 | 3784篇 |
2015年 | 2384篇 |
2014年 | 3031篇 |
2013年 | 6216篇 |
2012年 | 5684篇 |
2011年 | 5897篇 |
2010年 | 4353篇 |
2009年 | 4082篇 |
2008年 | 5298篇 |
2007年 | 4963篇 |
2006年 | 4627篇 |
2005年 | 4348篇 |
2004年 | 3890篇 |
2003年 | 3455篇 |
2002年 | 3330篇 |
2001年 | 3136篇 |
2000年 | 2547篇 |
1999年 | 1883篇 |
1998年 | 1622篇 |
1997年 | 1450篇 |
1996年 | 1447篇 |
1995年 | 1231篇 |
1994年 | 1280篇 |
1993年 | 1236篇 |
1992年 | 1321篇 |
1991年 | 1316篇 |
1990年 | 1299篇 |
1989年 | 1261篇 |
1988年 | 1174篇 |
1987年 | 1090篇 |
1986年 | 1051篇 |
1985年 | 1291篇 |
1984年 | 1361篇 |
1983年 | 1139篇 |
1982年 | 1156篇 |
1981年 | 1072篇 |
1980年 | 973篇 |
1979年 | 1028篇 |
1978年 | 1153篇 |
1977年 | 1170篇 |
1976年 | 1082篇 |
1975年 | 1008篇 |
1974年 | 1031篇 |
1973年 | 1020篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Z. U. Dzhabua T. O. Dadiani A. V. Gigineishvili M. Yu. Stamateli K. D. Davitadze G. N. Iluridze 《Physics of the Solid State》2006,48(8):1481-1485
A technique for preparing γ-Nd2S3 crystalline thin films through discrete vacuum thermal evaporation of a presynthesized bulk material is developed. The films deposited are doped with cadmium and lead. The reflectance and transmittance spectra of the films are measured in the photon energy range 0.2–3.0 eV at a temperature of 300 K. The frequency analysis of the absorption coefficient demonstrates that the γ-Nd2S3 films are characterized by an exponential absorption edge. The photoconductivity spectra and temperature dependences of the photoconductivity for the γ-Nd2S3 films doped with cadmium and lead are measured in the photon energy range 0.2–3.3 eV at temperatures varying from 115 to 380 K. The experimental data obtained are interpreted under the assumption that the acceptor levels formed by vacancies in the cation sublattice and compensated for by cadmium and lead donor dopants play a crucial role in the photoconduction. The ionization energy at the lead donor level is determined. 相似文献
992.
A. N. Titov O. N. Suvorova S. Yu. Ketkov S. G. Titova A. I. Merentsov 《Physics of the Solid State》2006,48(8):1466-1471
Single crystals and polycrystals of titanium diselenide TiSe2 intercalated with ferrocene Fe(η5-C5H5)2 and cobaltocene Co(η5-C5H5)2 are synthesized. The magnetic susceptibility and electrical resistivity of the intercalation compounds are measured. The results obtained demonstrate that the intercalation brings about the formation of an impurity band with a temperature-dependent width. 相似文献
993.
Antimonide-based superlattices dedicated to the elaboration of opto-electronic devices have been studied by X-ray scattering techniques. In particular, specular and non-specular X-ray reflectometry experiments have been performed on two MBE-samples elaborated with different shutter sequences at the interfaces. The results have shown a limitation of the incorporation of Sb species in the subsequent InAs layer for one of the samples, as expected.Then, a study on a InGaAs-cap layer/(InGaAs/AlAsSb)N superlattice grown on a InGaAs/InP buffer layer by both specular X-ray reflectometry and High resolution X-ray diffraction is reported. In particular, the results have revealed the presence of a highly disturbed thin-layer on top of the MOVPE-made GaInAs, whose presence has been explained by In-concentration modification during the desoxidation procedure at the surface of the MOVPE-made GaInAs.Beside the results on the Sb-based heterostructures, the use of X-ray scattering metrology as a routinely working non-destructive testing method has been emphasized. 相似文献
994.
We obtain the one-loop quantum corrections to the Kählerian and superpotentials in the generic chiral superfield model on the nonanticommutative superspace. Unlike all previous works, we use a method which does not require to rewrite a star-product of superfields in terms of ordinary products. In the Kählerian potential sector the one-loop contributions are analogous to ones in the undeformed theory while in the chiral potential sector the quantum corrections contain a deformation parameter. 相似文献
995.
J. Balogh D. Kaptás L. F. Kiss T. Kemény L. Bujdosó I. Vincze 《Hyperfine Interactions》2006,169(1-3):1343-1347
Magnetic multilayers of 57Fe with nominal thickness, T
nom, between 0.4 and 1.0 nm separated by 3.0 nm Al spacer layers were prepared by alternate deposition of the constituents in
high vacuum. The samples were investigated at 4.2 K in external magnetic field. A fraction of Fe atoms corresponding to about
0.3 nm equivalent Fe-thickness was found to mix into the Al spacer. The extremely strong magnetic anisotropy observed for
T
nom < 0.8 nm is attributed to Fe layers of approximately two atomic planes thick. The anisotropy decreases considerably after
the building up of the third Fe atomic layer starts at T
nom = 0.8 nm, but full saturation was not achieved even for T
nom = 1 nm and 3 T magnetic field applied perpendicularly to the sample plane. 相似文献
996.
O. Volkova K. Klimov O. Savelieva N. Tristan E. Goodilin B. Buechner A. Vasiliev 《Journal of magnetism and magnetic materials》2006
Magnetic and transport properties of double distorted perovskites CaCuMn6O12 and CaCu2Mn5O12 are studied in a range 2–300 K. The leading role in magnetism of these compounds belongs to antiferromagnetic exchange interaction of Cu2+ in square coordination with Mn3+/Mn4+ in octahedral coordination. The values of saturation magnetization indicate that Mn3+ ions in square coordination are coupled ferromagnetically with Mn3+/Mn4+ in octahedral coordination. The colossal magnetoresistance in the pellet samples is due assumingly to intergranular spin-polarized tunneling of current carriers. 相似文献
997.
The stoichiometric reactions of trimethylaluminum with 2,6‐(MeOCH2)2C6H3OH (LH) revealed compounds L3Al ( 1 ) and L2AlMe ( 2 ). On the other hand reaction of 1 equiv. of LH with trimethylaluminum did not lead to the formation of complex LAlMe2 ( 3 ), rather 2 together with Me3Al were observed as a result of a disproportionation of 3 . Compounds 1 and 2 were characterized by elemental analysis, 1H and 13C NMR spectroscopy and in the case of 1 by X‐ray diffraction. Derivative 2 underwent transmetalation with Ph3SnOH, giving LSnPh3 ( 4 ) as the result of a migration of ligand L from the aluminum to the tin atom. The identity of 4 was established by elemental analysis, 1H, 13C and 119Sn NMR spectroscopy and 1H, 119Sn HMBC experiments. The system 2 and B(C6F5)3 in a 1:1 molar ratio was shown to be active in the polymerization of propylene oxide and ε‐caprolactone. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
998.
Abull is the (self-complementary) graph with verticesa, b, c, d, e and edgesab, ac, bc, bd, ce; a graphG is calledBerge if neitherG not its complement contains a chordless cycle whose length is odd and at least five. We prove that bull-free Berge graphs are perfect; a part of our argument relies on a new property of minimal imperfect graphs.This work was done while both authors were at the School of Computer Science, McGill University; support by NSERC is gratefully acknowledged. 相似文献
999.
1000.
The properties of the solutions of a family of non-linear parametric problems are investigated in the neighbourhood of regular and irregular values of the parameter. Rules are proposed for constructing feedback-type controlling for non-linear dynamical systems with perturbations. An example is presented. 相似文献