全文获取类型
收费全文 | 49624篇 |
免费 | 7526篇 |
国内免费 | 5590篇 |
专业分类
化学 | 26305篇 |
晶体学 | 520篇 |
力学 | 2488篇 |
综合类 | 287篇 |
数学 | 4436篇 |
物理学 | 15207篇 |
无线电 | 13497篇 |
出版年
2024年 | 237篇 |
2023年 | 1194篇 |
2022年 | 1478篇 |
2021年 | 1859篇 |
2020年 | 1882篇 |
2019年 | 1730篇 |
2018年 | 1516篇 |
2017年 | 1489篇 |
2016年 | 2088篇 |
2015年 | 2268篇 |
2014年 | 2684篇 |
2013年 | 3306篇 |
2012年 | 4029篇 |
2011年 | 4108篇 |
2010年 | 2927篇 |
2009年 | 3057篇 |
2008年 | 3213篇 |
2007年 | 2902篇 |
2006年 | 2819篇 |
2005年 | 2230篇 |
2004年 | 1709篇 |
2003年 | 1523篇 |
2002年 | 1401篇 |
2001年 | 1182篇 |
2000年 | 1175篇 |
1999年 | 1127篇 |
1998年 | 1025篇 |
1997年 | 908篇 |
1996年 | 931篇 |
1995年 | 814篇 |
1994年 | 691篇 |
1993年 | 538篇 |
1992年 | 559篇 |
1991年 | 422篇 |
1990年 | 349篇 |
1989年 | 280篇 |
1988年 | 237篇 |
1987年 | 188篇 |
1986年 | 176篇 |
1985年 | 162篇 |
1984年 | 112篇 |
1983年 | 74篇 |
1982年 | 68篇 |
1981年 | 39篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1959年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
Fabrication of microfluidic optical waveguides on glass chips with femtosecond laser pulses 总被引:1,自引:0,他引:1
We describe the fabrication of microfluidic channel structures on the surface of a borosilicate glass slide by femtosecond laser direct writing for optical waveguide application. Liquid with a variable refractive index is fed into the microchannel, serving as the core of the waveguide. We demonstrate that either a multimode or a single-mode waveguide can be achieved by controlling the refractive index of the liquid. 相似文献
902.
A high power continuous-wave (CW) diode-pumped Nd:YAG laser operated in heat capacity mode is demonstrated by use of two identical highly efficient diode-pumped laser heads placed in a plane-plane resonator. The laser heads are uniformly pumped with a five-fold symmetrical side-pumping configuration,and each head is able to output maximum output power of 2200 W at 808 nm. Under a total pump power of 4290 W, the output power of the laser at 1064 nm is up to 2277 W, corresponding to an optical-to-optical efficiency of 53.1%. 相似文献
903.
Wan WQ Pan QH Jia GJ Xu YZ Lai GQ Liu SX Chen J Yang LM Zhang YF Weng SF Wu JG 《光谱学与光谱分析》2011,31(2):353-356
采用傅里叶变换衰减全反射中红外光谱法检测了24例液氮冻存的脑膜瘤离体样品(其中良性肿瘤12例,有恶性倾向的肿瘤12例),对得到的红外光谱进行整理分析,发现不同类型脑膜瘤组织(如纤维型脑膜瘤和内皮型脑膜瘤)的红外光谱存在着差异,并且同一种类型的脑膜瘤组织,其恶性倾向的程度不同,他们的红外光谱也表现出较为明显的区别,因此,我们可以从各个特征吸收峰的峰位、峰形及峰强等信息的变化来区分脑膜瘤,并可以初步鉴别脑膜瘤的性质;研究结果发现,通过某些特征吸收峰(如1 160cm-1)峰位的变化来鉴别脑膜瘤的性质与病理诊断结果的符合率大于85%,说明傅里叶变换衰减全反射中红外光谱法有可能发展成为一种对样品无损伤、快速的脑肿瘤诊断新方法。 相似文献
904.
Background
ALPK1 (α-kinase 1) is a member of an unconventional alpha-kinase family, and its biological function remains largely unknown. Here we report the phenotypic characterization of one mutant line, in which the piggyBac (PB) transposon is inserted into the Alpk1 gene. 相似文献905.
We propose and experimentally demonstrate a 40 Gb/s secure optical communication system with on-off-keying (OOK) modulation format by using a time domain spectral phase en/decoding scheme, which employs a highly dispersive element and high-speed phase modulator for introducing significant symbol overlapping for both the encoded and incorrectly decoded noiselike signals to enhance the information security against eavesdropping using a power detector. The influence of dispersion and chip modulation rate on the symbol overlapping of the incorrectly decoded signal has been analytically investigated and experimentally verified. Security enhancement for 40 Gb/s OOK data using fast reconfigurable 40 Gchip/s optical codes with code lengths of up to 1024 has been demonstrated and compared with a 10 Gb/s system. 相似文献
906.
907.
908.
The enhancement of phase-conjugnte wave in cerium-doped bismuth germanatecrystal(Ce:BGO) was investigated.The result indicated that the phase congugate mirror(PCM) reflectivity of the doped BGO is one order higher than that of pure BGO and the re-sponse time is also decreased for doped BGO.Their mechanism were discussed. 相似文献
909.
Y. Xu K. S. Krane M. A. Gummin J. L. Wood M. M. Jarrio J. B. Breitenbach E. F. Zganjar D. Rupnik H. K. Carter P. F. Mantica Jr. B. E. Zimmerman 《Hyperfine Interactions》1992,75(1-4):481-487
The184Au→184Pt decay, studied on-line with the UNISOR facility at HHIRF, is discussed. Gamma-ray and conversion-electron spectroscopy
of184Pt as well as on-line nuclear orientation measurements of184Au were done. A new low-lying level scheme of184Pt is proposed. Two coexisting bands with different deformations and their respective γ-vibrational bands are established.
Internal conversion coefficients for interband transitions between states with the same spin are extracted from the spectroscopy
measurements. The relative E0 contents of the transitions are determined by combining internal conversion coefficients with
E2/M1 mixing ratios deduced from gamma-ray anisotropies measured from oriented nuclei. 相似文献
910.
Nd:YAG激光器中的自锁模 总被引:3,自引:2,他引:3
本文报道在Nd:YAG激光器中首次获得的自锁模脉冲序列.自锁模是由于Nd:YAG棒中的自相位调制引起的.在主被动对撞锁模运转情况下,自锁模对脉冲波形有较大的影响. 相似文献