全文获取类型
收费全文 | 402篇 |
免费 | 29篇 |
国内免费 | 35篇 |
专业分类
化学 | 192篇 |
晶体学 | 2篇 |
力学 | 49篇 |
综合类 | 4篇 |
数学 | 22篇 |
物理学 | 56篇 |
无线电 | 141篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 14篇 |
2014年 | 19篇 |
2013年 | 15篇 |
2012年 | 13篇 |
2011年 | 20篇 |
2010年 | 14篇 |
2009年 | 20篇 |
2008年 | 23篇 |
2007年 | 16篇 |
2006年 | 22篇 |
2005年 | 28篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 13篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1998年 | 19篇 |
1997年 | 7篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 2篇 |
1993年 | 18篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有466条查询结果,搜索用时 218 毫秒
311.
Effect of realgar on extracellular amino acid neurotransmitters in hippocampal CA1 region determined by online microdialysis–dansyl chloride derivatization–high‐performance liquid chromatography and fluorescence detection
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)
Taoguang Huo Yinghua Zhang Weikai Li Huilei Yang Hong Jiang Guifan Sun 《Biomedical chromatography : BMC》2014,28(9):1254-1262
An online microdialysis (MD)–dansyl chloride (Dns) derivatization–high‐performance liquid chromatography (HPLC) and fluorescence detection (FD) system was developed for simultaneous determination of eight extracellular amino acid neurotransmitters in hippocampus. The MD probe was implanted in hippocampal CA1 region. Dialysate and Dns were online mixed and derivatized. The derivatives were separated on an ODS column and detected by FD. The developed online system showed good linearity, precision, accuracy and recovery. This online MD‐HPLC system was applied to monitor amino acid neurotransmitters levels in rats exposed to realgar (0.3, 0.9 and 2.7 g/kg body weight). The result shows that glutamate concentrations were significantly increased (p < 0.05) in hippocampal CA1 region of rats exposed to three doses of realgar. A decrease in γ‐aminobutyric acid concentrations was found in rats exposed to medium and high doses of realgar (p < 0.05). Elevation of excitotoxic index (EI) values in hippocampal CA1 region of realgar‐exposed rats was observed (p < 0.05). Positive correlation was found between EI values and arsenic contents in hippocampus of realgar‐exposed rats, which indicates that the change in extracellular EI values is associated with arsenic accumulation in hippocampus. The developed online MD–Dns derivatization–HPLC–FD system provides a new experimental method for studying the effect of toxic Chinese medicines on amino acid neurotransmitters. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
312.
Previous advances in WDM technology are now beginning to shift the focus more toward optical networking and network-level issues. Providing survivability at the optical layer is inherently attractive, but whether it makes practical sense, given similar mechanisms that are already available at the higher layers, poses serious challenges and raises many questions. Today's core network architecture model has functional overlap among its layers, contains outdated functionality, and is too slow to scale. If IP can be mapped directly onto the WDM layer, some of the unnecessary network layers can be eliminated, opening up new possibilities for developing a simple and integrated-protection/restoration scheme that can be coordinated at both the IP and WDM layers. This article presents an overview of existing optical protection/restoration schemes. Then we present a novel mesh-based hybrid optical protection scheme that utilizes multifiber physical links along with a hierarchical OXC structure. An overview of the envisioned IP-centric DWDM-based optical data network architecture is then presented. The basis of how to implement a more direct IP standard-based approach for closer and efficient IP-WDM integration is also discussed. Finally, we articulate a view of how to provide a joint protection/restoration scheme that is coordinated at both the IP and WDM layers 相似文献
313.
314.
介绍了LCD(液晶显示器)的基本工作原理和三星S3C44B0X的内置LCD控制器以及Linux操作系统下的设备管理.讨论了基于三星S3C44B0X内置LCD控制器的LCD驱动程序开发,重点介绍了将LCD驱动程序添加到Linux内核配置系统中的方法,使LCD驱动在Linux系统下得以实现. 相似文献
315.
介绍了一种与传统MTF法完全不同的测量电流密度因子n的新型动态电流斜坡测试法。测试了4种不同样品。结果表明,n值与材料有关,并符合BLACK方程。 相似文献
316.
In this paper, we discuss the construction of the confidence intervals for the regression vector β in a linear model under negatively associated errors. It is shown that the blockwise empirical likelihood (EL) ratio statistic for β is asymptotically χ2-type distributed. The result is used to obtain an EL based confidence region for β. 相似文献
317.
Wei S Zhang H Wang Y Wang L Li X Wang Y Zhang H Xu X Shi Y 《Journal of chromatography. A》2011,1218(29):4599-4605
The ultrasonic nebulization extraction-heating gas flow transfer coupled with headspace single drop microextraction (UNE-HGFT-HS-SDME) was developed for the extraction of essential oil from Zanthoxylum bungeanum Maxim. The gas chromatography-mass spectrometry was applied to the determination of the constituents in the essential oil. The contents of the constituents from essential oil obtained by the proposed method were found to be more similar to those obtained by hydro-distillation (HD) than those obtained by ultrasonic nebulization extraction coupled with headspace single drop microextraction (UNE-HS-SDME). The heating gas flow was firstly used in the analysis of the essential oil to transfer the analytes from the headspace to the solvent microdrop. The relative standard deviations for determining the five major constituents were in the range from 1.5 to 6.7%. The proposed method is a fast, sensitive, low cost and small sample consumption method for the determination of the volatile and semivolatile constituents in the plant materials. 相似文献
318.
To lower the operation temperature and increase the durability of solid oxide fuel cells(SOFCs), increasing attentions have been paid on developing cathode materials with good oxygen reduction reaction(ORR)activity at intermediate-temperature(IT, 500–750 °C) range. However, most cathode materials exhibit poor catalytic activity, or they thermally mismatch with SOFC electrolytes and undergo severe degeneration. Infiltrating catalysts on existing backbone materials has been proved to be an efficie... 相似文献
319.
Dynamics control of geometric quantum discord for two coupling qubits in a squeezed vacuum reservoir
We investigate the dynamics of geometric quantum discord of coupled qubits in a squeezed vacuum reservoir. The results show that there is distinct difference between the dynamics of geometric quantum discord and that of quantum entanglement near (or away from) the decoherence free subspace. We also find that the squeezed vacuum reservoir with high squeezed amplitude is more suitable for geometric quantum discord to survive. The robustness of geometric quantum discord is stronger than that of quantum entanglement. 相似文献
320.
Cheng Yang Yan Hu Ruiqi Shen Yinghua Ye Shouxu Wang Tianli Hua 《Applied Physics A: Materials Science & Processing》2014,114(2):459-464
Al/Ni multilayer bridge films, which were composed of alternate Al and Ni layers with bilayer thicknesses of 50, 100 and 200 nm, were prepared by RF magnetron sputtering. In each bilayer, the thickness ratio of Al to Ni was maintained at 3:2 to obtain an overall 1:1 atomic composition. The total thickness of Al/Ni multilayer films was 2 μm. XRD measurements show that the compound of AlNi is the final product of the exothermic reactions. DSC curves show that the values of heat release in Al/Ni multilayer films with bilayer thicknesses of 50, 100 and 200 nm are 389.43, 396.69 and 409.92 J?g?1, respectively. The temperatures of Al/Ni multilayer films were obviously higher than those of Al bridge film and Ni bridge film. Al/Ni multilayer films with modulation of 50 nm had the highest electrical explosion temperature of 7000 K. The exothermic reaction in Al/Ni multilayer films leads to a more intense electric explosion. Al/Ni multilayer bridge films with modulation period of 50 nm explode more rapidly and intensely than other bridge films because decreasing the bilayer thickness results in an increased reaction velocity. 相似文献