全文获取类型
收费全文 | 8723篇 |
免费 | 1288篇 |
国内免费 | 645篇 |
专业分类
化学 | 1917篇 |
晶体学 | 26篇 |
力学 | 724篇 |
综合类 | 212篇 |
数学 | 1287篇 |
物理学 | 6490篇 |
出版年
2024年 | 15篇 |
2023年 | 55篇 |
2022年 | 166篇 |
2021年 | 241篇 |
2020年 | 181篇 |
2019年 | 196篇 |
2018年 | 205篇 |
2017年 | 337篇 |
2016年 | 371篇 |
2015年 | 352篇 |
2014年 | 592篇 |
2013年 | 633篇 |
2012年 | 478篇 |
2011年 | 539篇 |
2010年 | 422篇 |
2009年 | 536篇 |
2008年 | 551篇 |
2007年 | 589篇 |
2006年 | 475篇 |
2005年 | 432篇 |
2004年 | 416篇 |
2003年 | 377篇 |
2002年 | 336篇 |
2001年 | 237篇 |
2000年 | 234篇 |
1999年 | 212篇 |
1998年 | 200篇 |
1997年 | 187篇 |
1996年 | 167篇 |
1995年 | 122篇 |
1994年 | 106篇 |
1993年 | 84篇 |
1992年 | 81篇 |
1991年 | 78篇 |
1990年 | 52篇 |
1989年 | 51篇 |
1988年 | 46篇 |
1987年 | 48篇 |
1986年 | 33篇 |
1985年 | 41篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 25篇 |
1981年 | 30篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
介绍微通道板电子透射膜在三代微光像增强器中的作用,推导电子透射膜死电压的理论表达式,测量电子透射膜的电子透过特性,并进行初步分析和讨论。 相似文献
992.
本文提出了一种彩色图像相减的新方法.该方法利用互相错动半个周期的两组三色光栅,在黑白底片上分别对待处理的两幅图像进行一次编码记录,然后在白光处理器上对黑白编码片进行彩色译码,即可实现彩色图像的强度相减,文中讨论了三色光栅实时生成和两组三色光栅条纹自动错动半个周期的方法,并给出了实验结果。 相似文献
993.
It is proved that the correlation coefficient between the elements of the order statistics is maximal for a rectangularly (uniformly) distributed population. 相似文献
994.
Sadanori Konishi 《Annals of the Institute of Statistical Mathematics》1985,37(1):87-94
Summary A concept of normalizing transformations of statistics is constructed on the basis of the rate of convergence to normality.
The concept is applied to derive a normalizing transformation of a maximum likelihood estimate of intraclass correlation coefficient
in ap-variate normal sample. Numerical comparisons are made to examine whether the proposed transformation is efficient to achieve
normality. The relationship between normalization and variance stabilization is also considered.
The Institute of Statistical Mathematics 相似文献
995.
J. -L. Charvet R. Dayras D. Durand O. Lopez D. Cussol D. Dor L. Nalpas A. Van Lauwe C. Volant 《Nuclear Physics A》2004,730(3-4):431-447
A previous analysis of the charge (Z) correlations in the ΔZ−Z plane for 129Xe+natSn central collisions at 32 MeV/n has shown an enhancement in the production of equally sized fragments (low ΔZ) which was interpreted as an evidence for spinodal decomposition. However, the signal is weak and rises the question of the estimation of the uncorrelated yield. After a critical analysis of its robustness, we propose in this paper a new technique to build the uncorrelated yield in the charge correlation function. The application of this method to 129Xe+natSn central collision data at 32, 39, 45 and 50 MeV/n does not show any particular enhancement of the correlation function in any ΔZ bin. 相似文献
996.
997.
V. V. Ammosov E. M. Gushchin S. V. Somov M. K. Timofeev V. A. Ryabov G. I. Tipografschik 《Radiation measurements》1995,25(1-4):183-184
The new type of a solid state track detector is described. The detector consists of the fibre or capillary target and the multistage image intensifier. The standard microchannel plate filled with liquid scintillator and the input fibre plate of the image intensifier was investigated as the targets. 相似文献
998.
Arturo Carnicer Santiago Vallmitjana JosRamn de F. Moneo Ignacio Juvells 《Optics Communications》1996,130(4-6):327-336
An original method to detect images in defocused scenes by means of a binary joint transform correlation is presented. Defocused images are described in frequency domain as the product between the Fourier transform of the in-focus scene by the optical transfer function of the imaging lens. This function, which presents positive and negative values, introduces sign errors in the joint power spectrum. The goal of this study is to detect the sign of the optical transfer function starting from the defocused image by means of a digital algorithm. Information provided by the algorithm allows to compensate the sign errors in the binary joint power spectrum and to obtain invariant correlations with respect to defocusing. Theoretical analysis and digital experiments to test the procedure are provided. 相似文献
999.
用光学相关识别方法测量单模光纤的折射率分布和色散 总被引:1,自引:0,他引:1
介绍了一种测量单模光纤剖面折射率分布和色散的新方法--光学相关识别方法。应用计算全息制作高斯-拉盖尔模的匹配滤波器,根据光学相关识别原理测出单模光纤场分布的展开系数,由此推得剖面折射率分布和色散,给出了实际测量结果。 相似文献
1000.
M. Wilhelm H. Feng U. Tracht H.W. Spiess 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,134(2):255-260
A new 2D solid-state CP/MAS13C NMR exchange experiment for through-space isotropic chemical shift correlation is proposed and demonstrated. Through-space correlation is established via a second cross polarization from13C to1H and subsequent1H spin diffusion. A third cross polarization results in the final13C–13C isotropic chemical shift correlation. The1H spin diffusion time is a variable parameter allowing different mean square magnetization displacements to be probed. Experimental results on mixtures of differently13C-labeled alanine and polyethylene indicate that this site-selective 2D technique can be used to characterize domain sizes and proximities over a wide range of length scales (1–200 nm) in solids such as polymers or biological materials. 相似文献