全文获取类型
收费全文 | 1349篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 61篇 |
晶体学 | 1篇 |
力学 | 14篇 |
综合类 | 3篇 |
数学 | 708篇 |
物理学 | 272篇 |
无线电 | 309篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 13篇 |
2012年 | 61篇 |
2011年 | 215篇 |
2010年 | 206篇 |
2009年 | 215篇 |
2008年 | 194篇 |
2007年 | 151篇 |
2006年 | 107篇 |
2005年 | 63篇 |
2004年 | 30篇 |
2003年 | 26篇 |
2002年 | 18篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
排序方式: 共有1368条查询结果,搜索用时 966 毫秒
201.
Taizo Kawauchi Katsuyuki Fukutani Shunji Kishimoto Yoshitaka Yoda 《Applied Surface Science》2009,256(4):962-964
Measurements of the internal-conversion electron emission due to the inelastic nuclear resonant excitation are reported. thin films of 20 and 1.3 nm thickness were deposited on Si(1 1 1), and the internal-conversion electrons were measured as a function of the photon energy. From the inelastic part of the spectra, the phonon density of states was obtained. Whereas the phonon density of states of 20-nm thick film resembles that of bulk -Fe, the 1.3-nm thick film revealed an obvious softening of the acoustic mode. 相似文献
202.
Ayako Imai Kenji Mawatari Nobuo Ueno Kazuyuki Sakamoto 《Applied Surface Science》2009,256(4):1156-1159
The thickness-dependent electronic structures of Dy silicide films grown on a Si(1 1 1) surface have been investigated by angle-resolved photoelectron spectroscopy. Two (1×1) periodic bands, both of them cross the Fermi level, have been observed in the silicide films formed by Dy coverages of 1.0 monolayer and below, and more than five () periodic bands have been observed in thicker films. Taking the () periodic structure of Dy atoms in the submonolayer silicide film into account, the periodicity of the two metallic bands indicate that they mainly originate from the orbitals of Si atoms, which form a (1×1) structure. Of the () periodic bands observed in thick films, four of them are well explained by the folding of the (1×1) bands into a () periodicity. Regarding the other band, the three () periodic bands would originate from the electronic states related to the inner Si layers that form a () structure, and the one observed in the 3.0 ML film only might originate from the electron located at the interface between bulk Si and the Dy silicide film. 相似文献
203.
C.A.C. Passos M.T.D. Orlando J.L. Passamai Jr. E.V.L. de Mello 《Physica B: Condensed Matter》2009,404(19):3123-3126
A model to describe the critical current density behavior of high-Tc polycrystalline superconductors is proposed for all magnetic field values. The main features of the model are as follows: the transport critical current density is controlled by the weak-link network at grain boundaries. The size distribution of weak links is well represented by a Gamma-type distribution. Finally, the tunneling critical current between grains follows a Fraunhofer diffraction pattern or a modified pattern if the applied magnetic field is lower or higher than the first critical field Hc1. 相似文献
204.
The damping of the motion of domain walls of a sandwich domain structure by the eddy currents magnetic fields, the stray fields and the hysteresis friction fields is investigated. The blocking of the motion of domain walls by the eddy currents magnetic fields is discovered. 相似文献
205.
The crystallization of single-phase nanocrystalline Nd10.8Dy1.5Fe79.7(NbZrCu)2.0B6.0 ribbons has been investigated. The as-spun ribbons are mainly composed of an amorphous matrix with a small amount of α-Fe, Nd2Fe14B and/or other crystallization phases. Cu-enriched clusters with different sizes have been found in the as-spun ribbons. These clusters almost disappear after crystallization, which can possess effects on the refinement of grains. 相似文献
206.
Although simple acids, replacing buffers, have been widely applied to suppress the ionization of weakly ionizable acidic analytes in reversed-phase liquid chromatography (RPLC), none of the previously reported works focused on the systematic studies about the retention behavior of the acidic solutes in this ion-suppression RPLC mode. The subject of this paper was therefore to investigate the retention behavior of monobasic weak acidic compounds using acetic, perchloric and phosphoric acids as the ion-suppressors. The apparent octanol-water partition coefficient (K″ow) was proposed to calibrate the octanol-water partition coefficient (Kow) of these weak acidic compounds, which resulted in a better linear correlation with log kw, the logarithm of the hypothetical retention factor corresponding to neat aqueous fraction of hydroorganic mobile phase. This log K″ow−log kw linear correlation was successfully validated by the results of monocarboxylic acids and monohydrating phenols, and moreover by the results under diverse experimental conditions for the same solutes. This straightforward relationship not only can be used to effectively predict the retention values of weak acidic solutes combined with Snyder-Soczewinski equation, but also can offer a promising medium for directly measuring Kow data of these compounds via Collander equation. In addition, the influence of the different ion-suppressors on the retention of weak acidic compounds was also compared in this RPLC mode. 相似文献
207.
The geodesic and induced path transit functions are the two well-studied interval functions in graphs. Two important transit functions related to the geodesic and induced path functions are the triangle path transit functions which consist of all vertices on all u,v-shortest (induced) paths or all vertices adjacent to two adjacent vertices on all u,v-shortest (induced) paths, for any two vertices u and v in a connected graph G. In this paper we study the two triangle path transit functions, namely the IΔ and JΔ on G. We discuss the betweenness axioms, for both triangle path transit functions. Also we present a characterization of pseudo-modular graphs using the transit function IΔ by forbidden subgraphs. 相似文献
208.
This paper introduces an iteration scheme for viscosity approximation of a zero of accretive operator in a reflexive Banach space with weakly continuous duality mapping. A new iterative sequence is introduced and strong convergence of the algorithm {xn} is proved. The results improve and extend the results of Su [Xiaolong Qin, Yongfu Su, Approximation of a zero point of accretive operator in Banach spaces, J. Math. Anal. Appl. 320 (2007) 415-424] and some others. 相似文献
209.
We consider L1-solutions of the following refinement type equations
210.
Marita Gazzini 《Journal of Mathematical Analysis and Applications》2009,352(1):99-3007
In this paper we deal with some Sobolev-type inequalities with weights that were proved by Maz'ya in [V.G. Maz'ja, Sobolev Spaces, Springer-Verlag, Berlin, 1980] and by Caffarelli, Kohn and Nirenberg in [L. Caffarelli, R. Kohn, L. Nirenberg, First order interpolation inequalities with weight, Compos. Math. 53 (1984) 259-275]. For integers 1?k?N denote points ξ∈RN=Rk×RN−k as pairs (x,y). Let p∈(1,N), q∈(p,p∗] and assume . Then there exists c>0 such that