全文获取类型
收费全文 | 3315篇 |
免费 | 325篇 |
国内免费 | 109篇 |
专业分类
化学 | 725篇 |
晶体学 | 12篇 |
力学 | 265篇 |
综合类 | 10篇 |
数学 | 220篇 |
物理学 | 2517篇 |
出版年
2024年 | 2篇 |
2023年 | 90篇 |
2022年 | 141篇 |
2021年 | 187篇 |
2020年 | 184篇 |
2019年 | 44篇 |
2018年 | 88篇 |
2017年 | 147篇 |
2016年 | 162篇 |
2015年 | 88篇 |
2014年 | 246篇 |
2013年 | 149篇 |
2012年 | 206篇 |
2011年 | 155篇 |
2010年 | 139篇 |
2009年 | 141篇 |
2008年 | 160篇 |
2007年 | 166篇 |
2006年 | 144篇 |
2005年 | 135篇 |
2004年 | 138篇 |
2003年 | 114篇 |
2002年 | 109篇 |
2001年 | 85篇 |
2000年 | 82篇 |
1999年 | 71篇 |
1998年 | 63篇 |
1997年 | 53篇 |
1996年 | 56篇 |
1995年 | 32篇 |
1994年 | 32篇 |
1993年 | 24篇 |
1992年 | 25篇 |
1991年 | 25篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有3749条查询结果,搜索用时 46 毫秒
191.
使图像获得不受光照和几何条件影响的颜色特性描述是实现颜色恒常性的关系,利用双色反射模型和有限维线性模型,提取归一化偏差体反射特征。被实验证明是实现颜色恒常性的一个重要途径,本文详细阐述了归一化偏差本体反射特征的特性,其计算方法,应用的前提条件,以及应用限制,并在实际图像处理中,考虑到了这些影响的因素。 相似文献
192.
193.
The introduction of UV-Vis absorption spectrophotometry to the study of radiation chemistry of polymers has opened the possibility to investigate even very opaque samples. The virgin powder polypropylene, as obtained from the industrial production line, shows after irradiation unstable products of radiolysis. Until now they were investigated mainly by EPR method. Optical absorption spectra (by diffuse reflection spectrophotometry) contribute to better identification and study of changes in time, temperature and diffusion of reactive gases. Studying the formation of stable compounds, which do not produce EPR signal, we are able to examine these species on the basis of their electronic spectra. The most important results concern the peroxides in irradiated polypropylene. 相似文献
194.
195.
Dilute aqueous solutions of dodecyl-benzenesulfonic acid sodium salt (DBS-Na) and polyoxyethylenenonylphenyl ethers (PONPEs) were ultrasonically atomized. The surfactants were concentrated in collected mist droplets. The enrichment ratio increased with decreasing surfactant concentration. Depending on the surfactant’s molecular weight and affinity to water, different enrichment ratio was observed in the range of low feed concentrations. For anionic surfactant, DBS-Na, the enrichment ratio was significantly improved by KCl addition and a peak appeared on the plot of the ratio against KCl concentration. Addition of NaCl or CaCl2 · 2H2O to the surfactant solution also enhanced the enrichment ratio; however, the effect was relatively small. Such behaviors of the ratio were interpreted as enhanced interfacial adsorption of the surfactant and a lack of supply of surfactant monomers from liquid bulk because of slow breaking of surfactant micelles. Time required for collecting an amount of mist was also observed. Among the three salt systems, the time for KCl system was twice as long as others. This fact suggested that the formation of smaller droplets in KCl system. 相似文献
196.
The functions of the main indices of refraction n(ν) and absorption κ(ν) of uniaxial thin polyethylene terephthalate films
have been calculated by the experimental spectra of frustrated total reflection of s-and p-polarized radiation in the 700–760-cm−1 range. The κo(ν) maximum falls at the the 727-cm−1 frequency and the maximum of κe(ν) falls at the the 724-and 732-cm− 1 frequencies.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 756–759, November–December, 2005. 相似文献
197.
We show that every finite subgroup of U(2) is contained with index two in a group generated by involutions fixing Lagrangian planes. We describe fundamental domains for their action on
related to the configuration of these Lagrangian planes. 相似文献
198.
S. Heilliette A. Chedin N.A. Scott R. Armante 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,86(2):201-214
The recent launch of the Advanced Infrared Sounder (AIRS) on board EOS-Aqua and the scheduled launch of the Infrared Atmospheric Sounder Interferometer (IASI) on board the Meteorological Operational Satellite (METOP) in 2005 open interesting perspectives for remote sensing applications. Owing to their enhanced spectral resolution and sensitivity, this new generation of high-resolution infrared vertical sounders is first aimed at improving the vertical resolution of temperature and water vapor profile retrievals needed by the weather forecasting community. Another important possible use of these instruments, in the context of the study of global warming, is to permit the retrieval of the concentrations of greenhouse gases like , etc. In order to reach these two main objectives, improvement in the modeling of the radiative transfer is therefore necessary. One of the points which still needs some improvements is the contribution of the downward radiation reflected by the surface back to the satellite which is often improperly accounted for in radiative transfer calculation to save computer time. In this article, we show how it is possible to simplify the problem through the computation of a spectrally dependent “effective” emissivity for which a simple parametrization is proposed, while preserving the accuracy of the results. 相似文献
199.
A. S. Mellit V. I. Rabanovich Yu. S. Samoilenko 《Functional Analysis and Its Applications》2004,38(2):157-160
We describe the set
of values of the parameter for which there exists a Hilbert space H and n partial reflections A
1,...,A
n
(self-adjoint operators such that A
k
3
=Ak or, which is the same, self-adjoint operators whose spectra belong to the set {-1,0,1}) whose sum is equal to the scalar operator I
H
. 相似文献
200.
We point out a connection between reflection principles and generic large cardinals. One principle of pure reflection is introduced that is as strong as generic supercompactness of 2 by -closed forcing. This new concept implies CH and extends the reflection principles for stationary sets in a canonical way.Mathematics Subject Classification (2000): 03E50, 03E55 相似文献