全文获取类型
收费全文 | 14915篇 |
免费 | 459篇 |
国内免费 | 323篇 |
专业分类
化学 | 9311篇 |
晶体学 | 103篇 |
力学 | 419篇 |
综合类 | 30篇 |
数学 | 1939篇 |
物理学 | 3895篇 |
出版年
2022年 | 174篇 |
2021年 | 194篇 |
2020年 | 187篇 |
2019年 | 186篇 |
2018年 | 179篇 |
2017年 | 151篇 |
2016年 | 341篇 |
2015年 | 305篇 |
2014年 | 380篇 |
2013年 | 787篇 |
2012年 | 654篇 |
2011年 | 750篇 |
2010年 | 537篇 |
2009年 | 515篇 |
2008年 | 681篇 |
2007年 | 726篇 |
2006年 | 575篇 |
2005年 | 590篇 |
2004年 | 599篇 |
2003年 | 586篇 |
2002年 | 617篇 |
2001年 | 443篇 |
2000年 | 400篇 |
1999年 | 310篇 |
1998年 | 226篇 |
1997年 | 206篇 |
1996年 | 223篇 |
1995年 | 237篇 |
1994年 | 229篇 |
1993年 | 180篇 |
1992年 | 170篇 |
1991年 | 176篇 |
1990年 | 192篇 |
1989年 | 155篇 |
1988年 | 141篇 |
1987年 | 137篇 |
1986年 | 123篇 |
1985年 | 216篇 |
1984年 | 233篇 |
1983年 | 159篇 |
1982年 | 178篇 |
1981年 | 148篇 |
1980年 | 151篇 |
1979年 | 140篇 |
1978年 | 118篇 |
1977年 | 162篇 |
1976年 | 142篇 |
1975年 | 118篇 |
1974年 | 111篇 |
1973年 | 114篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
V. De Sabbata C. Sivaram H.-H. v. Borzeszkowski H.-J. Treder 《Annalen der Physik》1991,503(7):497-502
It is shown that in gravitational theories with torsion one is led to commutation rules corresponding to Landau-Peierls type uncertainty relations. 相似文献
12.
D. De Salvador A. Coati E. Napolitani M. Berti A.V. Drigo M.S. Carroll J.C. Sturm J. Stangl G. Bauer L. Lazzarini 《Applied Physics A: Materials Science & Processing》2002,75(6):667-672
In this work we investigate the diffusion and precipitation of supersaturated substitutional carbon in 200-nm-thick SiGeC
layers buried under a silicon cap layer of 40 nm. The samples were annealed in either inert (N2) or oxidizing (O2) ambient at 850 °C for times ranging from 2 to 10 h. The silicon self-interstitial (I) flux coming from the surface under
oxidation enhances the C diffusion with respect to the N2-annealed samples. In the early stages of the oxidation process, the loss of C from the SiGeC layer by diffusion across the
layer/cap interface dominates. This phenomenon saturates after an initial period (2–4 h), which depends on the C concentration.
This saturation is due to the formation and growth of C-containing precipitates that are promoted by the I injection and act
as a sink for mobile C atoms. The influence of carbon concentration on the competition between precipitation and diffusion
is discussed.
Received: 19 October 2001 / Accepted: 19 December 2001 / Published online: 20 March 2002 / Published online: 20 March 2002 相似文献
13.
T. Temesvári C. De Dominicis I.R. Pimentel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(3):361-372
Symmetry considerations and a direct, Hubbard-Stratonovich type, derivation are used to construct a replica field-theory relevant
to the study of the spin glass transition of short range models in a magnetic field. A mean-field treatment reveals that two
different types of transitions exist, whenever the replica number n is kept larger than zero. The Sherrington-Kirkpatrick critical point in zero magnetic field between the paramagnet and replica
magnet (a replica symmetric phase with a nonzero spin glass order parameter) separates from the de Almeida-Thouless line,
along which replica symmetry breaking occurs. We argue that for studying the de Almeida-Thouless transition around the upper
critical dimension d = 6, it is necessary to use the generic cubic model with all the three bare masses and eight cubic couplings. The critical
role n may play is also emphasized. To make perturbative calculations feasible, a new representation of the cubic interaction is
introduced. To illustrate the method, we compute the masses in one-loop order. Some technical details and a list of vertex
rules are presented to help future renormalisation-group calculations.
Received 9 October 2001 相似文献
14.
15.
Zuo LIU Zhen De WU 《数学学报(英文版)》2005,21(5):997-1000
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given. 相似文献
16.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive
projections in Dedekind complete vector lattices and f-algebras.
AMS Classification: 47B65, 46A40, 06F25 相似文献
17.
Let Ψ(x,y) (resp. Ψm(x,y)) denote the number of integers not exceeding x that are y-friable, i.e. have no prime factor exceeding y (resp. and are coprime to m). Evaluating the ratio Ψm(x/d,y)/Ψ(x,y) for 1≤slantd≤slantx, m≥slant 1, x≥slant y≥slant 2, turns out to be a crucial step for estimating arithmetic sums over friable integers. Here, it is crucial to obtain formulae with a very wide range of validity. In this paper, several uniform estimates are provided for the aforementioned ratio, which supersede all previously known results. Applications are given to averages of various arithmetic functions over friable integers which in turn improve corresponding results from the literature. The technique employed rests mainly on the saddle-point method, which is an efficient and specific tool for the required design.2000 Mathematics Subject Classification: Primary—11N25; Secondary—11K65, 11N37 相似文献
18.
Journal d'Analyse Mathématique - 相似文献
19.
Michael De Castro 《Tetrahedron letters》2004,45(34):6501-6504
2-Deoxy-2-iodo-glycosylamides have been prepared from a variety of protected d-glucals by their reaction with N-iodosuccinimide and amides. Benzyl protected 2-iodoamides, when treated with sodium hydride and 15-crown-5, gave stable C1 N-linked 2-glycooxazolines as the major products. Silyl protected 2-iodoamides afforded the C1 O-linked 2-glycooxazolines; presumably by the rearrangement of unstable N-acylaziridine intermediates. 相似文献
20.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献