全文获取类型
收费全文 | 1937篇 |
免费 | 63篇 |
国内免费 | 22篇 |
专业分类
化学 | 1283篇 |
晶体学 | 4篇 |
力学 | 91篇 |
数学 | 194篇 |
物理学 | 450篇 |
出版年
2023年 | 11篇 |
2022年 | 31篇 |
2021年 | 56篇 |
2020年 | 42篇 |
2019年 | 31篇 |
2018年 | 38篇 |
2017年 | 17篇 |
2016年 | 57篇 |
2015年 | 44篇 |
2014年 | 52篇 |
2013年 | 91篇 |
2012年 | 66篇 |
2011年 | 98篇 |
2010年 | 78篇 |
2009年 | 60篇 |
2008年 | 103篇 |
2007年 | 87篇 |
2006年 | 96篇 |
2005年 | 80篇 |
2004年 | 64篇 |
2003年 | 77篇 |
2002年 | 57篇 |
2001年 | 56篇 |
2000年 | 55篇 |
1999年 | 48篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 29篇 |
1995年 | 27篇 |
1994年 | 30篇 |
1993年 | 33篇 |
1992年 | 25篇 |
1991年 | 19篇 |
1990年 | 13篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 24篇 |
1984年 | 23篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1976年 | 17篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1973年 | 10篇 |
排序方式: 共有2022条查询结果,搜索用时 0 毫秒
171.
172.
In the on-going evolution of GaAs quantum well infrared photodetectors (QWIPs) we have developed a 1,024 × 1,024 (1K × 1K), 8–12 μm infrared focal plane array (FPA). This 1 megapixel detector array is a hybrid using an L3/Cincinnati Electronics silicon readout integrated circuit (ROIC) bump bonded to a GaAs QWIP array fabricated jointly by engineers at the Goddard Space Flight Center (GSFC) and the Army Research Laboratory (ARL). We have integrated the 1K × 1K array into an SE-IR based imaging camera system and performed tests over the 50–80 K temperature range achieving BLIP performance at an operating temperature of 57 K. The GaAs array is relatively easy to fabricate once the superlattice structure of the quantum wells has been defined and grown. The overall arrays costs are currently dominated by the costs associated with the silicon readout since the GaAs array fabrication is based on high yield, well-established GaAs processing capabilities. One of the advantages of GaAs QWIP technology is the ability to fabricate arrays in a fashion similar to and compatible with silicon IC technology. The designer’s ability to easily select the spectral response of the material from 3 μm to beyond 15 μm is the result of the success of band-gap engineering and the Army Research Lab is a leader in this area. In this paper we will present the first results of our 1K × 1K QWIP array development including fabrication methodology, test data and imaging capabilities. 相似文献
173.
We analyze in some detail the course that Ettore Majorana gave on theoretical physics at the University of Naples between
January and March 1938, just prior to his mysterious disappearance. We discuss, in particular, the recently discovered Moreno
Lecture Notes, in which all of Majorana’s lectures are recorded, six of which are not present in those that are preserved
in the Domus Galilaeana in Pisa, Italy.
Antonino Drago is a retired professor of history of physics at the University of Naples “Federico II.” Salvatore Esposito
is a researcher on theoretical physics and history of physics at the University of Naples “Federico II.” 相似文献
174.
J.-M. Chauveau C. Morhain B. Lo B. Vinter P. Vennéguès M. Laügt D. Buell M. Tesseire-Doninelli G. Neu 《Applied Physics A: Materials Science & Processing》2007,88(1):65-69
Non polar ZnO and (Zn, Co)O layers were successfully grown on (11̄02) sapphire (R-plane sapphire). The growth process was
shown to directly influence the surface morphology as well as the strain state in (112̄0) ZnO (A-plane ZnO). The dominant
defect lines seen in photoluminescence were due to basal stacking faults as demonstrated by means of selective photoluminescence
and transmission electron microscopy. We present a novel method for growing high quality A-plane ZnO by inserting a (Zn, Co)O
thin buffer layer, which strongly reduced the surface roughness. Finally (Zn, Mg)O/ZnO quantum well structures were grown
on such a buffer layer. These quantum wells exhibited no intrinsic quantum confined Stark effect.
PACS 81.05.Dz; 81.15.Hi; 78.67.Hc; 68.65.Fg 相似文献
175.
Herein we report the copper-catalyzed asymmetric conjugate addition of Grignard reagents to cyclic and acyclic enones, with SimplePhos as chiral ligands. A variety of Grignard reagents can be added to a range of cyclic and acyclic enones, with moderate to good enantioselectivities (ee’s up to 86%). 相似文献
176.
177.
G. Filippone N. Tz. Dintcheva F. P. La Mantia D. Acierno 《Journal of Polymer Science.Polymer Physics》2010,48(5):600-609
A study was made on the effect of small amounts of organically modified clay on the morphology and mechanical properties of blends of low‐density polyethylene and polyamide 11 at different compositions. The influence of the filler on the blend morphology was investigated using wide angle X‐ray diffractometry, scanning and transmission electron microscopy and selective extraction experiments. The filler was found to locate predominantly in the more hydrophilic polyamide phase. Although such uneven distribution does not have a significant effect on the onset of phase co‐continuity of the polymer components, it brings about a drastic refinement of the microstructure for the blends both with droplets/matrix and co‐continuous morphologies. In addition to the expected reinforcing action of the filler, the resulting fine microstructure plays an important role in enhancing the mechanical properties of the blends. This is essentially because of a good quality of stress transfer across the interface between the constituents, which also seems to benefit for a good interfacial adhesion promoted by the filler. Our results provide the experimental evidence for the capabilities of nanoparticles added to multiphase polymer systems to act selectively as a reinforcing agent for specific domains of the material and as a medium able to assist the refinement of the polymer phases during mixing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 600–609, 2010 相似文献
178.
V. Cucinotta Alessandro Giuffrida Giulia Grasso Giuseppe Maccarrone Antonino Mazzaglia Graziella Vecchio 《Analytical and bioanalytical chemistry》2001,370(4):363-366
The separation of three pairs of enantiomeric herbicides has been successfully achieved by capillary electrophoresis at two different pH values in the presence of cyclodextrin derivatives previously synthesized in our laboratory. Two of these derivatives constitute a new class of receptor, the hemispherodextrins, in which a trehalose capping moiety is bonded to β-cyclodextrin. Because of their peculiar structure hemispherodextrins have very promising characteristics and the low receptor concentration required to achieve separation deserves particular interest. 相似文献
179.
Barbara La Ferla Laura Russo Cristina Airoldi Francesco Nicotra 《Tetrahedron: Asymmetry》2009,20(6-8):744-745
A C-glycoside mimetic of l-galactose 1-diphosphate, a potential ligand of GDP-l-galactose hydrolase, an enzyme involved in the biosynthesis of vitamin C, has been designed, stereoselectively synthesised by C-allylation of tribenzylated l-fucose, by periodate-osmium tetroxide degradation of the double bond, by condensation of the obtained aldehydes with benzylacetate and by deprotection. The obtained mimetic was linked to a sepharose resin. 相似文献
180.