全文获取类型
收费全文 | 1786篇 |
免费 | 86篇 |
国内免费 | 10篇 |
专业分类
化学 | 1430篇 |
晶体学 | 22篇 |
力学 | 13篇 |
数学 | 113篇 |
物理学 | 304篇 |
出版年
2023年 | 15篇 |
2022年 | 20篇 |
2021年 | 26篇 |
2020年 | 35篇 |
2019年 | 40篇 |
2018年 | 21篇 |
2017年 | 17篇 |
2016年 | 48篇 |
2015年 | 34篇 |
2014年 | 52篇 |
2013年 | 89篇 |
2012年 | 134篇 |
2011年 | 121篇 |
2010年 | 83篇 |
2009年 | 55篇 |
2008年 | 132篇 |
2007年 | 101篇 |
2006年 | 112篇 |
2005年 | 122篇 |
2004年 | 112篇 |
2003年 | 89篇 |
2002年 | 67篇 |
2001年 | 23篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 11篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 6篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 8篇 |
排序方式: 共有1882条查询结果,搜索用时 62 毫秒
161.
Atsuko Ito Keiko Iwai Chiyuki Oyama Setsu Morimoto Hiroaki Kato 《Hyperfine Interactions》1992,71(1-4):1371-1374
Magnetization and Mössbauer measurements have been made on a diluted antiferromagnets FexMg1?xTiO3 with x=0.2, 0.3 and 0.7. It has been demonstrated that this system exhibits a spin glass or a reentrant spin glass like behavior in the samples with x around the percolation concenrration xc≈0.25. It has been shown that various sizes of magnetic clusters are formed well above the transition temperatures determined by the magnetization measurements in the samples with x near xc. The behavior of Fe0.2Mg0.8TiO3 is discussed as a typical cluster glass. 相似文献
162.
The present work deals with the electrochemical formation of superlattice structures on n-type (1 0 0) InP in HCl solutions. The superlattices consist of a stack of two layers with alternating high and low porosity on n-type material obtained by changing the anodizing current or the potential periodically in HCl solutions. The superlattice structures were characterized by scanning electron microscopy. The pore morphology and structure depend strongly on the electrochemical conditions. For anodization with low currents (e.g., 1 or 10 mA) or at low potentials (e.g., 1.5 VAg/AgCl), a porous layer with a facet-like structure was formed. For higher currents or potentials, such as 50 or 100 mA or 3 VAg/AgCl, respectively, a tree-like structure with random and/or tangled branches was observed. Finally, samples anodized at 5 VAg/AgCl, show a porous layer with a regular array of straight pores. The morphology and structure of the stacks of the porous layers can be controlled in the nanometer range, depending on the electrochemical conditions. 相似文献
163.
164.
Yu Ding Ruggero Micheletto Hiroaki Hanada Toshihiko Nagamura Satoshi Okazaki Koji Otsuka 《Optical Review》2002,9(6):277-281
This work describes a groundbreaking process that provides a direct highly localized measurement of the atomic mass on surfaces at room temperature. Employing an original system that joins a scanning tunneling microscopy (STM) device and a time of flight (TOF) mass analyzer, we could previously ionize surface atoms by the combination of an optical laser pulse and an electric pulse at the STM tip. Desorbed ions from a localized area were accelerated and detected by a TOF chamber. We will demonstrate in this paper that high localization and mass discrimination can be obtained even without the aid of an electric pulse from the tip. We reduced the angle of incidence of the laser beam to zero (laser beam parallel to the sample surface). In this condition we were able to demonstrate for the first time ionic desorption at a confinement level of the order of 5-10nm, an order of magnitude better than previous configurations.This paper was originally presented at the 11th Optical Near Field Workshop, which was held on June 28, 2002 at Tokyo Institute of Technology, Yokohama, organized by the Optical Near Field Group of the Optical Society of Japan, an affiliate of the Japan Society of Applied Physics. 相似文献
165.
Hiroaki Yamamoto Youji Kanie Masakazu Arakawa Keiji Taniguchi 《Applied Physics A: Materials Science & Processing》1990,50(6):577-581
The transmission coefficient and the resonance condition in the one-dimensional rectangular double-, triple-, quadruple-, and quintuple-barrier structures are derived theoretically under the assumption of the constant tunneling effective mass. It is found that the resonance energies are different from the eigenvalues in the quantum well due to coupling between wells in the multiple-barrier (much more than triple-barrier) structures. It is confirmed that the transmission spectrum is a Lorentzian near to energies of resonance. 相似文献
166.
Hidekatsu Yokoyama Toshiyuki Sato Tateaki Ogata Hiroaki Ohya-Nishiguchi Hitoshi Kamada 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,129(2):201-206
A signal detector of longitudinally detected ESR (LODESR) is independent of the resonant frequency. We developed anin vivoLODESR spectrometer operating in the regions of 300, 700, and 900 MHz. Using this apparatus, we estimated signal intensities at different operating frequencies obtained from non- or high-dielectric loss phantoms that contained nitroxide radical solutions and from live rats that had received a nitroxide radical. Our result, higher signal intensities in the high-dielectric loss samples (such as physiological saline solution and animals) at a lower frequency, shows that the influence of a decrease in dielectric loss dominates over the signal reduction caused by smaller Zeeman splitting. We believe that this finding strongly supports anin vivoESR resonant frequency that tends to be low. 相似文献
167.
This paper describes a practical method for design and fabrication of holographic optical elements (HOEs) as off-axis imaging optics. The authors have designed and fabricated a compact glass-like and see-through display using HOE and a total internal reflection prism. Observers can see through the display because wavelength selectivity of the HOE provides high transparency. Wave front of the HOE is designed by commercial software, though the actual fabrication method is not provided. The authors propose a practical method to fabricate HOEs, which can be applied to a wide range of imaging optics.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15–17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan. 相似文献
168.
Hiroaki Taniguchi 《Graphs and Combinatorics》2007,23(4):455-465
Let q = 2l with l≥ 1 and d ≥ 2. We prove that any automorphism of the d-dimensional dual hyperoval
over GF(q), constructed in [3] for any (d + 1)-dimensional GF(q)-vector subspace V in GF(qn) with n≥ d + 1 and for any generator σ of the Galois group of GF(qn) over GF(q), always fixes the special member X(∞). Moreover, we prove that, in case V = GF(qd+1), two dual hyperovals
and
in PG(2d + 1,q), where σ and τ are generators of the Galois group of GF(qd+1) over GF(q), are isomorphic if and only if (1) σ = τ or (2) σ τ = id. Therefore, we have proved that, even in the case q > 2, there exist non isomorphic d-dimensional dual hyperovals in PG(2d + 1,q) for d ≥ 3. 相似文献
169.
170.
Masashi Shigenobu Kazuhiro Takenaka Hiroaki Sasai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(33):9708-9712
A palladium‐catalyzed direct arylation of isoxazoles with aryl iodides has been achieved. The C H bond at the 5‐position is activated selectively to give coupling products in moderate to good yields. This direct arylation was applied to the synthesis of a spiro‐type chiral ligand, which proved to be most effective to the palladium‐catalyzed tandem cyclization of a dialkenyl alcohol. 相似文献