全文获取类型
收费全文 | 15719篇 |
免费 | 2577篇 |
国内免费 | 1692篇 |
专业分类
化学 | 11599篇 |
晶体学 | 194篇 |
力学 | 843篇 |
综合类 | 72篇 |
数学 | 1543篇 |
物理学 | 5737篇 |
出版年
2024年 | 59篇 |
2023年 | 320篇 |
2022年 | 560篇 |
2021年 | 550篇 |
2020年 | 635篇 |
2019年 | 639篇 |
2018年 | 579篇 |
2017年 | 507篇 |
2016年 | 736篇 |
2015年 | 778篇 |
2014年 | 980篇 |
2013年 | 1209篇 |
2012年 | 1402篇 |
2011年 | 1480篇 |
2010年 | 1061篇 |
2009年 | 905篇 |
2008年 | 1046篇 |
2007年 | 953篇 |
2006年 | 839篇 |
2005年 | 727篇 |
2004年 | 543篇 |
2003年 | 458篇 |
2002年 | 426篇 |
2001年 | 305篇 |
2000年 | 305篇 |
1999年 | 252篇 |
1998年 | 224篇 |
1997年 | 195篇 |
1996年 | 183篇 |
1995年 | 144篇 |
1994年 | 185篇 |
1993年 | 129篇 |
1992年 | 125篇 |
1991年 | 96篇 |
1990年 | 90篇 |
1989年 | 85篇 |
1988年 | 45篇 |
1987年 | 31篇 |
1986年 | 34篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 17篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1967年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
讨论了横向位移双曝光散斑图维纳谱的信息分布,并由此导出杨氏纹图的一般表达式。讨论了条纹可见度与应变,面内转动,照明光束直径与条纹图图空间坐标的关系,指出了在条纹可见度影响下最大可见条纹数目。还讨论了散斑衬比与衍射晕的关系。 相似文献
82.
铝酸锶铕的合成与发光的研究 总被引:35,自引:2,他引:33
本文详细报导4(SrEu)O·7Al2O3.磷光体的合成及激活剂Eu2+离子浓度、硼酸、五氧化二磷等对磷光体发光强度,发射光谱和激发光谱的影响.讨论了不同Eu2+离子之间的能量传递.测量了不同Eu2+浓度下磷光体的荧光寿命和长余辉特性. 相似文献
83.
Haishan Bu Yanwan Pang Dandan Song Tongyin Yu T. M. Voll George Czornyj B. Wunderlich 《Journal of Polymer Science.Polymer Physics》1991,29(2):139-152
Various approaches to the preparation and verification of single-molecule single crystals are discussed for polyethylene and poly (oxyethylene). Analytic tools are electron microscopy, electron diffraction, and differential scanning calorimetry. The main difficulty in producing a single-molecule single crystal is to keep crystals from joining during growth. 相似文献
84.
Xiaodong Xu Pingxin Song Guoqing Zhou Jun Xu Peizhen Deng 《Solid State Communications》2004,129(11):717-720
Cr4+:YbAG (Cr4+:Yb3Al5O12) crystal with a size up to Φ24 mm×30 mm was grown by the Czochralski method. In the absorption spectrum, there are two absorption bands at 939 and 969 nm, respectively, which are suitable for InGaAs diode laser pumping, and there is an absorption band at 1030 nm, which is suitable for passive Q-switched laser output at 1.03 μm. A broad emission spectrum from 970 to 1100 nm was exhibited from 940 nm wavelength pumping. This crystal is promising as a self-Q-switched laser crystal used for compact, efficient, highly stable, passive self-Q-switched thin chip solid-state lasers. 相似文献
85.
We demonstrated a unified two-band broadband light source based on erbium-doped fiber. The proposed scheme generates high output power at both bands and saves doped-fiber and pump lasers. 相似文献
86.
This paper deals with a model of time-dependent double diffusive convection in Darcy flow. In particular it is concerned with the spatial decay of solutions when the flow is confined to a semi-infinite cylinder. Decay bounds for an energy expression are derived. 相似文献
87.
We prove some basic properties of Donaldson’s flow of surfaces in a hyperkähler 4-manifold. When the initial submanifold is symplectic with respect to one Kähler form and Lagrangian with respect to another, we show that certain kinds of singularities cannot form, and we prove a convergence result under a condition related to one considered by M.-T. Wang for the mean curvature flow. 相似文献
88.
Approximation of signals from local averages 总被引:4,自引:0,他引:4
This work is concerned with approximation of a signal from local averages. It improves a result of Butzer and Lei [P.L. Butzer, J. Lei, Approximation of signals using measured sampled values and error analysis, Commun. Appl. Anal. 4 (2000) 245–255]. 相似文献
89.
In this article, composite nanofibers of poly(ε-caprolactone) (PCL) with iron–platinum (FePt) nanoparticles were successfully fabricated via coaxial electrospinning. The structure and morphology of FePt/PCL composite nanofibers were observed using transmission electron microscope and scanning electron microscope, respectively. The magnetic behavior of FePt/PCL composite nanofibers was investigated by alternating gradient magnetometer at room temperature. 相似文献
90.
Meihua Lu H. Gong T. Song Jian-Ping Wang Hong-Wei Zhang T.J. Zhou 《Journal of magnetism and magnetic materials》2006
We present a simple way to synthesize FePt and ZnO (wide-band-gap semiconductor) nanoparticle composites. The FePt nanoparticles were fabricated using the method reported by Sun et al. By controlling the heating rate, 3 nm FePt nanoparticles were synthesized. Well-dispersed FePt and ZnO nanoparticle composites were prepared by further adding zinc acetate and oleyl amine into the 3 nm FePt nanoparticle dispersion. By controlling the molar ratio of the FePt and zinc acetate, FePt and ZnO nanoparticle composites with different FePt particle fractions were obtained. The intensity of photo luminescence spectra of the nanoparticle composites increases very much with decreasing FePt particle fraction, whereas the peak position shifts a little. After annealing at 550 °C for half an hour, the nanoparticle composites become magnetically hard or semi-hard with coercivity much dependent on the FePt particle volume fraction. The coercivity of the composites increases with annealing temperature. The composites hold the promise of applications in new generation recording and/or optical devices. 相似文献