全文获取类型
收费全文 | 892篇 |
免费 | 21篇 |
国内免费 | 14篇 |
专业分类
化学 | 53篇 |
晶体学 | 4篇 |
力学 | 33篇 |
综合类 | 2篇 |
数学 | 240篇 |
物理学 | 405篇 |
综合类 | 190篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 19篇 |
2016年 | 9篇 |
2015年 | 17篇 |
2014年 | 39篇 |
2013年 | 46篇 |
2012年 | 30篇 |
2011年 | 60篇 |
2010年 | 70篇 |
2009年 | 60篇 |
2008年 | 69篇 |
2007年 | 66篇 |
2006年 | 52篇 |
2005年 | 49篇 |
2004年 | 40篇 |
2003年 | 41篇 |
2002年 | 27篇 |
2001年 | 18篇 |
2000年 | 18篇 |
1999年 | 21篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有927条查询结果,搜索用时 9 毫秒
1.
在经济全球一体化和经济区域化已成为当今世界经济发展大势的背景下,西部区域经济之所以发展不利,根本原因是区域经济理论陈旧落后,缺乏创新的区域发展思维。这些深层次的问题得不到解决,西部的城镇化水平和区域经济难以得到快速发展。因此,“三分构想”的提出是十分必要和迫切的。 相似文献
2.
根据数学物理理论,对尖端导体表面附近的静电场进行研究。得出尖端导体表面附近的电势分布和等势线方程。利用场强与电势的关系,导出尖端导体表面附近的电场强度的数学表达式,并求出尖端导体表面的面电荷密度,进而又利用电场强度与等势线的关系,导出尖端附近的电力线方程。 相似文献
3.
非对称数字用户线路传输技术原理及应用优势 总被引:1,自引:0,他引:1
介绍了非对称数字用户线路( ADS L) 这种新的高速宽带接入网传输技术, 探讨了它的基本原理和关键技术;比较了ADSL 与传统接入网技术的优劣,指出了 ADSL 技术发展的前景. 相似文献
4.
对超级数字用户线路倍增系统的实现进行了讨论,给出了一个实际实现系统的设计方案及其实测数据,对利用高比特率数字用户线(HDSL)技术提出了一些建议。 相似文献
5.
O.M. Lyulin V.I. Perevalov H. Tran J.-Y. Mandin V. Dana L. Rgalia-Jarlot X. Thomas D. Dcatoire 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(17):1815-1824
Using the Fourier transform spectra of the acetylene molecule recorded near 1.5-μm, the intensities of 111 lines belonging to seven hot bands of the main isotopologue 12C2H2 have been retrieved by means of a multispectrum fitting procedure. Considering the density of lines in the spectra, and the fact that the measured bands are the weakest observed, the accuracy of the measurements is around 10%. At first stage, an empirical treatment of these data has been performed, leading to the vibrational transition dipole moment squared and some Herman–Wallis coefficients. Then the measured line intensities of this work and collected ones from the literature have been treated simultaneously within the framework of the effective operator approach. 相似文献
6.
Y. Marandet H. Capes L. Godbert-Mouret M. Koubiti J. Rosato R. Stamm 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):247-260
In this work we investigate the influence of low
frequency turbulence on Doppler spectral line shapes in magnetized
plasmas. Low frequency refers here to fluctuations whose typical
time scale is much larger than those characterizing the atomic
processes, such as radiative decay, collisions and charge exchange.
This ordering is in particular relevant for drift wave turbulence,
ubiquitous in edge plasmas of fusion devices. Turbulent fluctuations
are found to affect line shapes through both the spatial and time
averages introduced by the measurement process. The profile is
expressed in terms of the fluid fields describing the plasma.
Assuming the spectrometer acquisition time to be much larger than
the turbulent time scale, an ordering generally fulfilled in
experiments, allows to develop a statistical formalism. We proceed
by successively investigating the effects of density, fluid velocity
and temperature fluctuations on the Doppler profile of a spectral
line emitted by a charge exchange population of neutrals. Line
shapes, and especially line wings are found to be affected by ion
temperature or fluid velocity fluctuations, and can in some cases
exhibit a power-law behavior. These effects are shown to be
measurable with existing techniques, and their interpretation in
each particular case would rely on already existing tools. From a
fundamental point of view, this study gives some insights in the
appearance of non-Boltzmann statistics, such as Lévy statistics,
when dealing with averaged experimental data. 相似文献
7.
Martin Bohner Gusein Sh. Guseinov 《Journal of Mathematical Analysis and Applications》2007,326(2):1124-1141
In this paper we study curves parametrized by a time scale parameter, introduce line delta and nabla integrals along time scale curves, and obtain an analog of Green's formula in the time scale setting. 相似文献
8.
9.
Tiziana Boffa Ballaran 《Phase Transitions》2013,86(1-2):137-154
Following recent developments in the application of autocorrelation analysis of line broadening in powder absorption IR spectra, the possibility that elastic strain heterogeneities are responsible both for such broadening and for enthalpy variations in solid solutions has been explored systematically. Recent data for five silicate solid solutions, augite-jadeite, almandine-grossular, albite-anorthite, anthophyllite-grunerite and clinoenstatite-clinoferrosilite, are reviewed. Variations in the autocorrelation parameter for line broadening, j corr, scale linearly with calorimetric data for enthalpy variations, j H , associated with cation substitutions and ordering in these systems. It is proposed that, while there may not be a universal calibration of j H in terms of j corr for all structures, it should be possible to produce empirical calibrations for groups of solid solutions with the same basic structure. Variations in j corr at different phonon frequency ranges provide additional insights into the structural mechanisms by which ordering, mixing, displacive and reconstructive processes occur in silicate solid solutions. 相似文献
10.
S. Djenie A. Srekovi S. Bukvi 《Spectrochimica Acta Part B: Atomic Spectroscopy》2005,60(12):1552-1555
The Stark widths (W) and shifts (d) of two neutral (520.908 and 546.550 nm), eleven singly (211.382, 224.643, 224.874, 232.029, 232.468, 233.140, 241.141, 241.323, 243.781, 244.793 and 276.754 nm) and three doubly (216.189, 231.004 and 239.569 nm) ionized silver (Ag I, Ag II and Ag III, respectively) spectral lines have been measured in nitrogen plasma at about 18,000 K electron temperature and electron density ranged between 0.65 × 1023 and 1.15 × 1023 m− 3. They are the first measured W and d values while those of the Ag II and Ag III lines are the first published data in these spectra. The modified version of the linear, low-pressure, pulsed arc was used as a plasma source operated in nitrogen with silver atoms, as impurities, evaporated from silver cylindrical plates located in the homogeneous part of the discharge. No theoretical predictions exist for W and d values of above mentioned spectral lines. Besides, we have checked the transition probability ratio of two investigated Ag I lines. An agreement with theoretical predictions was found. 相似文献