全文获取类型
收费全文 | 15860篇 |
免费 | 2785篇 |
国内免费 | 2300篇 |
专业分类
化学 | 11981篇 |
晶体学 | 118篇 |
力学 | 939篇 |
综合类 | 147篇 |
数学 | 1767篇 |
物理学 | 5993篇 |
出版年
2024年 | 51篇 |
2023年 | 354篇 |
2022年 | 523篇 |
2021年 | 571篇 |
2020年 | 676篇 |
2019年 | 601篇 |
2018年 | 491篇 |
2017年 | 469篇 |
2016年 | 754篇 |
2015年 | 720篇 |
2014年 | 867篇 |
2013年 | 1213篇 |
2012年 | 1436篇 |
2011年 | 1408篇 |
2010年 | 1031篇 |
2009年 | 1035篇 |
2008年 | 1102篇 |
2007年 | 982篇 |
2006年 | 876篇 |
2005年 | 797篇 |
2004年 | 643篇 |
2003年 | 628篇 |
2002年 | 530篇 |
2001年 | 406篇 |
2000年 | 374篇 |
1999年 | 365篇 |
1998年 | 282篇 |
1997年 | 248篇 |
1996年 | 286篇 |
1995年 | 211篇 |
1994年 | 184篇 |
1993年 | 165篇 |
1992年 | 135篇 |
1991年 | 108篇 |
1990年 | 108篇 |
1989年 | 65篇 |
1988年 | 56篇 |
1987年 | 57篇 |
1986年 | 40篇 |
1985年 | 30篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Liu Wenbin Huang Yiwei Huang Guolin Fan Lijiao Xie Yuming Shi Jeffery 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2055-2068
Journal of Radioanalytical and Nuclear Chemistry - Eco-friendly and low-cost composite, amidoxime-functionalized microcrystalline cellulose/mesoporous silica (MCC/MS-AO), were synthesized by... 相似文献
2.
Wang Rong Li Xu Zhou Youshi Cao Shuxuan Xu Honghao Han Wenjuan Zhang Yuxia Liu Junhai 《Journal of Russian Laser Research》2022,43(4):476-481
Journal of Russian Laser Research - We demonstrate a passively-mode-locked Pr3+: LuLiF4 laser operated at the 604 nm orange wave-length, using monolayer graphene as a saturable absorber. The... 相似文献
3.
Simultaneous determination of cinnamaldehyde and its metabolite in rat tissues by gas chromatography–mass spectrometry
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hang Zhao Qian Yang Yanhua Xie Jiyuan Sun Honghai Tu Wei Cao Siwang Wang 《Biomedical chromatography : BMC》2015,29(2):182-187
Cinnamaldehyde (CA), an active ingredient isolated from the traditional Chinese medicine Cortex Cinnamomi, has a wide range of bioactivities. To clarify the distribution characteristics of CA, a selective and sensitive method utilizing gas chromatography–mass spetrometry was initially developed for simultaneously determining the concentration of CA and its metabolite cinnamyl alcohol in rat tissues. Selected ion masses of m/z 131, 105 and 92 were chosen, and separation of the analytes was performed on a DB‐5 ms (30 m × 0.25 mm, 0.25 µm, thickness) capillary column by gas chromatography–mass spectrometry. The calibration curves demonstrated good linearity and reproducibility over the range of 20–2000 and 20–4000 ng/mL for various tissue samples. Recoveries ranged from 86.8 to 107.5%, while intra‐ and interday relative standard deviations were all <11.3%. The analysis method was successfully applied in tissue distribution studies for CA and cinnamyl alcohol. As CA and cinnamyl alcohol may inter‐convert to one another, simultaneous determination of both analytes provides a comparative and accurate data for tissue study. The concentrations of CA and cinnamyl alcohol remaining in spleen were the highest among the main organs, including heart, liver, spleen, lung, kidney and brain. In addition, there was no long‐term accumulation of CA in rat tissues. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
4.
5.
6.
Luo Dajuan Liu Bingqian Gao Rong Su Lixia Su Yonghuan 《Journal of Solid State Electrochemistry》2022,26(3):749-759
Journal of Solid State Electrochemistry - Cortisol, a steroid hormone, has been confirmed as a kind of biomarker that reflects the stress response of psychobiology and related adverse health... 相似文献
7.
8.
9.
We propose a system of time-division multiplexing(TDM) and spatial frequency-division multiplexing(SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is-97.2 d B re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is-32.7 d B with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160. 相似文献
10.
We proposed an electro-optic modulator with two-bus one-ring (TBOR) structure to improve the extinction ratio and reduce insert loss. It has a dual output compared with one-bus one-ring structure. In addition, double-layer graphene makes it possible for the modulation in the visible to mid-infrared wavelength range. It shows that this new electro-optic modulator can present two switching states well with low insertion loss, high absorption and high extinction ratio. At , when the switching states are based on the chemical potential, and , the insertion losses of both output ports are less than 2 dB, the absorption of the output port coupled via a micro-ring reaches 45 dB and the extinction ratio reaches 14 dB. When the refractive index of the dielectric material is 4.2, the applied voltage will be less than 1.2 V, thus can be used in low-voltage CMOS technology. 相似文献