全文获取类型
收费全文 | 238039篇 |
免费 | 2043篇 |
国内免费 | 610篇 |
专业分类
化学 | 123902篇 |
晶体学 | 4082篇 |
力学 | 10121篇 |
综合类 | 4篇 |
数学 | 27004篇 |
物理学 | 75579篇 |
出版年
2021年 | 1987篇 |
2020年 | 2223篇 |
2019年 | 2518篇 |
2018年 | 3363篇 |
2017年 | 3521篇 |
2016年 | 5046篇 |
2015年 | 2771篇 |
2014年 | 4608篇 |
2013年 | 10495篇 |
2012年 | 8214篇 |
2011年 | 9629篇 |
2010年 | 7241篇 |
2009年 | 7269篇 |
2008年 | 9085篇 |
2007年 | 8856篇 |
2006年 | 8462篇 |
2005年 | 7517篇 |
2004年 | 6996篇 |
2003年 | 6344篇 |
2002年 | 6253篇 |
2001年 | 7087篇 |
2000年 | 5279篇 |
1999年 | 4046篇 |
1998年 | 3483篇 |
1997年 | 3288篇 |
1996年 | 3017篇 |
1995年 | 2830篇 |
1994年 | 2801篇 |
1993年 | 2707篇 |
1992年 | 3061篇 |
1991年 | 3053篇 |
1990年 | 2945篇 |
1989年 | 2881篇 |
1988年 | 2808篇 |
1987年 | 2777篇 |
1986年 | 2622篇 |
1985年 | 3386篇 |
1984年 | 3515篇 |
1983年 | 3083篇 |
1982年 | 3207篇 |
1981年 | 2928篇 |
1980年 | 2895篇 |
1979年 | 3062篇 |
1978年 | 3215篇 |
1977年 | 3174篇 |
1976年 | 3140篇 |
1975年 | 3031篇 |
1974年 | 2996篇 |
1973年 | 3147篇 |
1972年 | 2127篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
A rapid single-step method for the electrosynthesis of chloro and bromo complexes of palladium(II and IV), viz. M2[PdX4] and M2[PdX6], by the dissolution of a palladium anode in chloride or bromide containing media is described. Electrolysis of dilute HX solution in the presence of pyridine, 2,2′-bipyridyl or 1,10-phenanthroline gives rise to non-electrolytes, e.g. trans-[PdX2(py)2], [PdX2(bipy)] and [PdX2(phen)]. Anodic oxidation of palladium in HX medium in the presence of acetonitrile and benzonitrile also gives the non-electrolytes trans-[PdX2(CH3CH2NH2)2] and trans-[PdX2(C6H5CH2NH2)2], respectively. 相似文献
962.
963.
B. Abramovitz 《Acta Appl Math》1994,36(3):211-226
In this work, we consider the regularization method for linear ill-posed problems. For operators and approximating subspaces satisfying certain conditions and for a specific form of the regularization parameter, upper and lower bounds are given for the condition number of the corresponding discrete problem. 相似文献
964.
965.
This paper presents a connection between the defining basis presented by Beilinson-Lusztig-MacPherson [1] in their geometric setting for quantum GLn and the isomorphism classes of linear quiver representations. More precisely, the positive part of the basis in [1] identifies with the defining basis for the relevant Ringel-Hall algebra; hence, it is a PBW basis in the sense of quantum groups. This approach extends to q-Schur algebras, yielding a monomial basis property with respect to the Drinfeld-Jimbo type presentation for the positive (or negative) part of the q-Schur algebra. Finally, the paper establishes an explicit connection between the canonical basis for the positive part of quantum GLn and the Kazhdan-Lusztig basis for q-Schur algebras. 相似文献
966.
C.J. Lu H.M. Shen S.B. Ren Y.N. Wang 《Applied Physics A: Materials Science & Processing》1997,65(4-5):395-401
3 thin films is systematically studied by using X-ray diffraction (XRD). The PbTiO3 thin films with different average grain sizes were prepared on various substrates by a sol-gel process. The films on NaCl
and fused glass are randomly grain-oriented, while those on (111)Pt/Ti/SiO2/Si are highly {100} cubic index grain-oriented . It is found from the XRD patterns of the films on NaCl that with decreasing
average grain size from 230 to 80 nm, the intensities of high h index (h>l) peaks (hkl), such as (100), (110), (200), (201),
(210), (211), etc., decrease rapidly and ultimately disappear, whereas another set of peaks (lkh), including (001), (002),
(102), (112), etc., are still intense. This interesting result suggests that at grain size below a certain critical size an
increasing number of grains no longer show 90°-domains, which is confirmed by TEM observations. Meanwhile, X-ray evidence
of such a grain-size-related absence of 90°-domains is also found for PbTiO3 films on Pt(111) and fused-glass substrates. The volume fractions of single-domain grains (without 90°-domains) in the films
are estimated from their XRD patterns. By combining SEM and TEM investigations, the critical grain size for the formation
of 90°-domains is further determined to be near 200 nm.
Received: 19 December 1996/Accepted: 24 March 1997 相似文献
967.
R. B. Gelfand V. A. Gordeev Yu. V. Gorelkinsky S. A. Kuten A. V. Mudry N. N. Nevinny V. I. Rapoport A. G. Ulyashin 《Hyperfine Interactions》1991,64(1-4):579-584
The electronic structure of muonium (Mu) located at the bond-centered sites of the silicon and diamond crystals is calculated
by the intermediate neglect of differential overlap method. Calculations of the electronicg- and hyperfine interaction tensors of the impurity atom are performed. The results obtained are compared to the experimental
properties of “anomalous” muonium Mu*. It is shown that the properties of Mu located at the bond-centered sites of the Si and C lattices are in qualitative agreement
with the observed properties of Mu*. 相似文献
968.
We derive a q-deformed version of the Lorentz algebra by deforming the algebraSL(2,C). The method is based on linear representations of the algebra on the complex quantum spinor space. We find that the generators usually identified withSL q(2,C) generateSU q (2) only. Four additional generators are added which generate Lorentz boosts. The full algebra of all seven generators and their coproduct is presented. We show that in the limitq→1 the generators are those of the classical Lorentz algebra plus an additionalU(1). Thus we have a deformation ofSL(2,C)×U(1). 相似文献
969.
S. V. Bulyarskii N. A. Butylkina N. S. Grushko A. E. Luk'yanov M. V. Nazarov I. O. Stepin 《Russian Physics Journal》1991,34(4):339-342
Latent macroscopic defects in silicon are detected by electrical and electron microscope measurements. They lead to anomalous temperature dependence of the Fermi level position and growth in the hole capture coefficient. A level with energy of 0.55 eV measured from the conduction zone controls the recombination process. It is proposed that macroscopic defects develop upon association of oxygen-silicon vacancy complexes. Action of an electron beam leads to reversible changes which increase upon multiple scanning, affecting the value of the diffusion length.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 71–75, April, 1991. 相似文献
970.
Yu. I. Golovin R. B. Morgunov M. B. Badylevich S. Z. Shmurak 《Physics of the Solid State》1997,39(8):1232-1234
Observations indicate that illuminating NaCl crystals by ultraviolet light (λ=350 nm) suppresses the magnetoplastic effect. The processes induced by illumination take place in a subsystem of point defects
and are related to a change in the state of magnetically sensitive dislocation pinning sites.
Fiz. Tverd. Tela (St. Petersburg) 39, 1389–1391 (1996) 相似文献