全文获取类型
收费全文 | 2269篇 |
免费 | 254篇 |
国内免费 | 193篇 |
专业分类
化学 | 1714篇 |
晶体学 | 29篇 |
力学 | 96篇 |
综合类 | 12篇 |
数学 | 218篇 |
物理学 | 647篇 |
出版年
2024年 | 3篇 |
2023年 | 40篇 |
2022年 | 70篇 |
2021年 | 71篇 |
2020年 | 77篇 |
2019年 | 96篇 |
2018年 | 69篇 |
2017年 | 54篇 |
2016年 | 91篇 |
2015年 | 86篇 |
2014年 | 111篇 |
2013年 | 151篇 |
2012年 | 179篇 |
2011年 | 199篇 |
2010年 | 126篇 |
2009年 | 109篇 |
2008年 | 141篇 |
2007年 | 135篇 |
2006年 | 118篇 |
2005年 | 116篇 |
2004年 | 68篇 |
2003年 | 54篇 |
2002年 | 76篇 |
2001年 | 48篇 |
2000年 | 35篇 |
1999年 | 33篇 |
1998年 | 30篇 |
1997年 | 30篇 |
1996年 | 33篇 |
1995年 | 32篇 |
1994年 | 23篇 |
1993年 | 18篇 |
1992年 | 30篇 |
1991年 | 13篇 |
1990年 | 23篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1975年 | 3篇 |
1961年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2716条查询结果,搜索用时 15 毫秒
1.
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
2.
This paper presents an evaluation of the capability of turbulence models available in the commercial CFD code FLUENT 6.0 for their application to hydrofoil turbulent boundary layer separation flow at high Reynolds numbers. Four widely applied two‐equation RANS turbulence models were assessed through comparison with experimental data at Reynolds numbers of 8.284×106 and 1.657×107. They were the standard k–εmodel, the realizable k–εmodel, the standard k–ωmodel and the shear‐stress‐transport (SST) k–ωmodel. It has found that the realizable k–εturbulence model used with enhanced wall functions and near‐wall modelling techniques, consistently provides superior performance in predicting the flow characteristics around the hydrofoil. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
3.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
4.
The implementation of a nonzero-order joint transform correlator using the double port Mach-Zehnder interferometric technique is proposed and demonstrated. This approach provides on-line processing for directly removing the zero-order components of a joint power spectrum in one step and performs the nonzero-order optical correlation. Experimental results are presented and discussed. 相似文献
5.
In this article a new technique was developed to fabricate scaffolds with a unique microstructure by solid–liquid separation in combination with particulate-leaching. Firstly, the effects of polymer concentration, quenching temperature on the porous morphology and the mechanical property of obtained scaffolds during solid–liquid separation have been investigated. Then, salt granules as porogen were introduced into the solid–liquid phase separation to produce the unique pore structure of the scaffold. The pore diameter of the scaffold could be controlled with the particulate size and the wall of pores possessed special microstructure, which enhanced the pore interconnectivity. The cell culture results confirmed that a good interconnectivity of the scaffold prepared by the improved solid–liquid separation was useful for nutrition transportation and cell proliferation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
6.
7.
Two novel dithienylethenes with ferrocene units were synthesized by Wittig reaction. The structure of 2a has been established by X‐ray diffraction studies. They could reversibly interconvert between two thermally stable forms, an open and a closed one, using light of different wavelengths as triggers. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
8.
9.
Eight compounds were isolated from Oxytropis myriophylla. On the basis of spectral analyses, their structures were elucidated to be (6R,9R)-roseoside (1), (6R,9S)-roseoside (2), adenosine (3), myriophylloside B (4), myriophylloside C (5), myriophylloside D (6), myriophylloside E (7), and myriophylloside F (8). Five flavonoids (4-8) were new compounds, and the three known compounds were isolated from this plant for the first time. 相似文献
10.