全文获取类型
收费全文 | 10146篇 |
免费 | 1468篇 |
国内免费 | 1457篇 |
专业分类
化学 | 7359篇 |
晶体学 | 179篇 |
力学 | 491篇 |
综合类 | 141篇 |
数学 | 1582篇 |
物理学 | 3319篇 |
出版年
2024年 | 30篇 |
2023年 | 194篇 |
2022年 | 329篇 |
2021年 | 364篇 |
2020年 | 455篇 |
2019年 | 439篇 |
2018年 | 396篇 |
2017年 | 402篇 |
2016年 | 502篇 |
2015年 | 520篇 |
2014年 | 582篇 |
2013年 | 846篇 |
2012年 | 936篇 |
2011年 | 907篇 |
2010年 | 711篇 |
2009年 | 684篇 |
2008年 | 764篇 |
2007年 | 643篇 |
2006年 | 577篇 |
2005年 | 436篇 |
2004年 | 318篇 |
2003年 | 269篇 |
2002年 | 319篇 |
2001年 | 229篇 |
2000年 | 175篇 |
1999年 | 149篇 |
1998年 | 97篇 |
1997年 | 81篇 |
1996年 | 83篇 |
1995年 | 50篇 |
1994年 | 63篇 |
1993年 | 55篇 |
1992年 | 39篇 |
1991年 | 40篇 |
1990年 | 42篇 |
1989年 | 25篇 |
1988年 | 31篇 |
1987年 | 22篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1980年 | 18篇 |
1979年 | 11篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Analysis and pharmacokinetic study of polyphyllin H in beagle dog plasma after oral administration of Rhizoma Paridis Extracts by LC‐MS/MS 下载免费PDF全文
2.
3.
4.
玻璃陶瓷材料中Tm3+离子红外到蓝色上转换发光 总被引:4,自引:0,他引:4
系统研究了PbF2+GeO2+WO3ⅩⅣTmF3玻璃陶瓷材料中,在近红外光(1.06μm)激发下,Tm3+离子的发光特性.实验中观测到Tm3+离子的两组峰值位置分别在20920cm-1和22173cm-1的蓝色上转换发光,并证实这两组上转换发光分别与吸收三个和四个光子有关,同时建立了上转换发光的模型.为了选择最佳掺杂浓度,详细地测量了Tm3+离子峰值为20920cm-1的蓝色上转换发光强度与TmF3浓度的关系. 相似文献
5.
We employ a first-principles plane wave method with the
relativistic analytic pseudopotential of Hartwigsen, Goedecker and Hutter
(HGH) scheme in the frame of DFT to calculate
the equilibrium lattice parameters and the thermodynamic properties of
AlB2 compound with hcp structure. The obtained lattice parameters are in
good agreement with the available experimental data and those calculated by
others. Through the quasi-harmonic Debye model, obtained successfully are
the dependences of the
normalized lattice parameters a/a0 and c/c0 on pressure P, the normalized
primitive cell volume V/V0 on pressure P, the variation of the thermal
expansion α with pressure P and temperature T, as well as the Debye
temperature \ThetaD and the heat capacity CV on pressure P and
temperature T. 相似文献
6.
Qipeng Guo Fei Chen Ke Wang Ling Chen 《Journal of Polymer Science.Polymer Physics》2006,44(21):3042-3052
An amphiphilic poly(ethylene oxide)‐block‐poly(dimethylsiloxane) (PEO–PDMS) diblock copolymer was used to template a bisphenol A type epoxy resin (ER); nanostructured thermoset blends of ER and PEO–PDMS were prepared with 4,4′‐methylenedianiline (MDA) as the curing agent. The phase behavior, crystallization, hydrogen‐bonding interactions, and nanoscale structures were investigated with differential scanning calorimetry, Fourier transform infrared spectroscopy, transmission electron microscopy, and small‐angle X‐ray scattering. The uncured ER was miscible with the poly(ethylene oxide) block of PEO–PDMS, and the uncured blends were not macroscopically phase‐separated. Macroscopic phase separation took place in the MDA‐cured ER/PEO–PDMS blends containing 60–80 wt % PEO–PDMS diblock copolymer. However, the composition‐dependent nanostructures were formed in the cured blends with 10–50 wt % PEO–PDMS, which did not show macroscopic phase separation. The poly(dimethylsiloxane) microdomains with sizes of 10–20 nm were dispersed in a continuous ER‐rich phase; the average distance between the neighboring microdomains was in the range of 20–50 nm. The miscibility between the cured ER and the poly(ethylene oxide) block of PEO–PDMS was ascribed to the favorable hydrogen‐bonding interaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3042–3052, 2006 相似文献
7.
Theoretical and experimental investigations on the performance of micro-perforated -panel absorbers are reviewed in this paper. By reviewing recent research work, this paper reveals a relationship between the maximum absorption coefficient and the limit of the absorption frequency bandwidth. It has been demonstrated that the absorption frequency bandwidth can be extended up to 3 or 4 octaves as the diameters of the micro-holes decrease. This has become possible with the development of the technologies for manufacturing micro-perforated panels, such as laser drilling, powder metallurgy, welded meshing and electro-etching to form micrometer order holes. In this paper, absorption characteristics of such absorbers in random fields and in high sound intensity are discussed both theoretically and experimentally. A new absorbing structure based on micro-perforated-panel absorbers demonstrate experimentally high sound absorption capability. This review shows that the micro-perforated-panel absorber has potentials to be one of ideal absorbing materials in the 21st century. 相似文献
8.
9.
10.
Dan Voiculescu 《Reports on Mathematical Physics》2005,55(1):127-133
This short note summarizes the circumstances of the birth of free probability theory andsome of the recent achievements. 相似文献