全文获取类型
收费全文 | 8565篇 |
免费 | 315篇 |
国内免费 | 4篇 |
专业分类
化学 | 5200篇 |
晶体学 | 171篇 |
力学 | 183篇 |
数学 | 1665篇 |
物理学 | 1665篇 |
出版年
2023年 | 42篇 |
2022年 | 68篇 |
2021年 | 84篇 |
2020年 | 138篇 |
2019年 | 188篇 |
2018年 | 204篇 |
2017年 | 234篇 |
2016年 | 442篇 |
2015年 | 338篇 |
2014年 | 415篇 |
2013年 | 738篇 |
2012年 | 476篇 |
2011年 | 505篇 |
2010年 | 370篇 |
2009年 | 296篇 |
2008年 | 532篇 |
2007年 | 476篇 |
2006年 | 411篇 |
2005年 | 334篇 |
2004年 | 266篇 |
2003年 | 201篇 |
2002年 | 174篇 |
2001年 | 123篇 |
2000年 | 121篇 |
1999年 | 80篇 |
1998年 | 82篇 |
1997年 | 57篇 |
1996年 | 69篇 |
1995年 | 61篇 |
1994年 | 52篇 |
1993年 | 35篇 |
1992年 | 44篇 |
1991年 | 61篇 |
1990年 | 46篇 |
1989年 | 58篇 |
1988年 | 63篇 |
1987年 | 51篇 |
1986年 | 52篇 |
1985年 | 111篇 |
1984年 | 108篇 |
1983年 | 73篇 |
1982年 | 65篇 |
1981年 | 80篇 |
1980年 | 67篇 |
1979年 | 54篇 |
1978年 | 42篇 |
1977年 | 33篇 |
1976年 | 47篇 |
1975年 | 42篇 |
1974年 | 34篇 |
排序方式: 共有8884条查询结果,搜索用时 343 毫秒
71.
72.
Tadeusz Bałaban 《Communications in Mathematical Physics》1987,109(2):249-301
We study four-dimensional pure gauge field theories by the renormalization group approach. The analysis is restricted to small field approximation. In this region we construct a sequence of localized effective actions by cluster expansions in one step renormalization transformations. We construct also -functions and we define a coupling constant renormalization by a recursive system of renormalization group equations. 相似文献
73.
The Monte-Carlo model of a light-emitting diode 总被引:1,自引:0,他引:1
The first complete Monte-Carlo model of a surface light-emitting diode is presented in this paper. In the model all important phenomena (including the two-dimensional diffusion of minority carriers before their recombination in the active region and the re-emission of radiation) are taken into account. The influence of various construction parameters on the external quantum efficiency of the homojunction GaAs diode is examined. 相似文献
74.
75.
Summary
A simple two-velocity model (-model)of the Boltzmann-Enskog equation for a gas of hard spheres is proposed. Physical properties of such a model are analyzed and its differences with respect to the Carleman model are investigated. Global existence theorems and some qualitative properties of solutions of the -model are also proved.On leave from Dept. of Mathematics and Mechanics, University of Warsaw, Poland. 相似文献
76.
The thermal decomposition of cadmium acetate dihydrate in helium and in air atmosphere has been investigated by means of a
coupled TG-DTA-MS method combined with X-ray diffraction analysis. Dehydration of Cd(CH3COO)2·2H2O is a two-stage process with Cd(CH3COO)2·H2O as intermediate. The way of Cd(CH3COO)2 decomposition strongly depends on the surrounding gas atmosphere and the rate of heating. CdO, acetone and CO2 are the primary products of decomposition in air. In helium decomposition goes by two parallel and consecutive reactions
in which intermediates, Cd and CdCO3, are formed. Metallic cadmium oxidizes and cadmium carbonate decomposes giving CdO. Some of the metallic cadmium, depending
on the heating rate and the concentration of oxygen, evaporates. Acetone is partially oxidized in secondary reactions with
oxygen.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
77.
D. Płusa J. J. Wysłocki B. Wysłocki R. Pfranger 《Applied Physics A: Materials Science & Processing》1986,40(3):167-170
From measurements of the magnetic domain widthsD versus grain thicknessL, we have determined the domain wall energy in the demagnetized state for a sintered Nd15Fe77B8 magnet: = 56 erg/cm2. Using this wall energy and the published magnetocry-stalline constantK
1=4.9×107 erg/cm3, we have calculated the exchange constantA=4.0×10–6 erg/cm, domain wall thickness
B=89 Å, and the critical diameter for single domain particlesD
c=0.67 m. 相似文献
78.
[reaction: see text] Starting from tetrakis(3,5-bis(bromomethyl)phenyl)porphyrin, pincer-porphyrin hybrid molecules (tetrakis(ECE-pincer)porphyrin; E = N, P, S) based on a tetraphenylporphyrin skeleton have been prepared in high yields. These multi-ligand site compounds could be selectively metalated at their peripheries, which was shown by X-ray crystallography. 相似文献
79.
Katleen Boussu Jérémie De Baerdemaeker Charles Dauwe Marc Weber Kelvin G Lynn Diederik Depla Steliana Aldea Ivo F J Vankelecom Carlo Vandecasteele Bart Van der Bruggen 《Chemphyschem》2007,8(3):370-379
This study presents a methodology for an in-depth characterization of six representative commercial nanofiltration membranes. Laboratory-made polyethersulfone membranes are included for reference. Besides the physical characterization [molecular weight cut-off (MWCO), surface charge, roughness and hydrophobicity], the membranes are also studied for their chemical composition [attenuated total reflectance Fourier spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS)] and porosity [positron annihilation spectroscopy (PAS)]. The chemical characterization indicates that all membranes are composed of at least two different layers. The presence of an additional third layer is proved and studied for membranes with a polyamide top layer. PAS experiments, in combination with FIB (focused ion beam) images, show that these membranes also have a thinner and a less porous skin layer (upper part of the top layer). In the skin layer, two different pore sizes are observed for all commercial membranes: a pore size of 1.25-1.55 angstroms as well as a pore size of 3.20-3.95 angstroms (both depending on the membrane type). Thus, the pore size distribution in nanofiltration membranes is bimodal, in contrast to the generally accepted log-normal distribution. Although the pore sizes are rather similar for all commercial membranes, their pore volume fraction and hence their porosity differ significantly. 相似文献
80.
Z. Rzączyńska A. Ostasz M. Sikorska-Iwan H. Głuchowska E. Olszewska S. Pikus 《Journal of Thermal Analysis and Calorimetry》2006,84(3):575-579
The complexes
of yttrium(III) and lanthanides(III) with 1,2,4,5-benzenetetracarboxylic acid
were prepared as crystalline solids of the general formula Ln4(C10H2O8)3⋅14H2O. They
are insoluble in water. On heating in air or inert gas atmosphere all compounds
lose water molecules; next anhydrous compounds decompose to oxides. The yttrium
complex and heavy lanthanide (from Ho to Lu) ones crystallize in monoclinic
crystal system. The dehydration does not change the crystal structure of the
compounds. 相似文献