全文获取类型
收费全文 | 162篇 |
免费 | 43篇 |
国内免费 | 34篇 |
专业分类
化学 | 137篇 |
晶体学 | 3篇 |
力学 | 15篇 |
数学 | 20篇 |
物理学 | 64篇 |
出版年
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 13篇 |
2012年 | 24篇 |
2011年 | 17篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 16篇 |
2007年 | 14篇 |
2006年 | 13篇 |
2005年 | 16篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有239条查询结果,搜索用时 15 毫秒
91.
Qiang Zhang Cang Huang Dong Jiang Xiaobo Wei Zhen Qian Fei Wei Beijing Key Laboratory of Green Chemical Reaction Engineering Technology 《中国颗粒学报》2009,7(3)
Based on three-dimensional (3D) acceleration sensing, an intelligent particle spy capable of detecting, transferring, and storing data, is proposed under the name of Particle Measurement Sensor (PMS). A prototype 60-mm-dia PMS was tested to track its freefall in terms of velocity and displacement, and served as a particle spy in a fluidized bed delivering the in situ acceleration information it detects. With increasing superficial gas velocity in the fluidized bed, the acceleration felt by PMS was observed to increase. The variance of the signals, which reflect the fluctuation, increased at first, reaching a maximum at the gas velocity (Uc) which marks the transition from bubbling to turbulent fluidization. Through probability density distribution (PDD) analysis, the PDD peak can be divided into the emulsion phase peak and the bubble phase peak. The average acceleration of emulsion and bubble phase increased, while the variance of both phases reached a maximum at Oc, at the same time. However, the difference between the variances of two phases reached the maximum at Oc. Findings of this study indicate that PMS can record independent in situ information. Further, it can provide other in situ measurements when equipped with additional multi-functional sensors. 相似文献
92.
The error compensation for an error caused from unwanted surfaces when using single autocollimator reflection type centering
error testing. And compare the result with commercial equipment like OptiCentric built by TRIOPTICS GmbH using a concave lens
and a convex lens. 相似文献
93.
Wei Zhang Jiantao Liu Guiyao Zhou Changming Xia Jiale Wu Yun Chen Xuelong Cang Zhiyun Hou 《Optical and Quantum Electronics》2017,49(1):27
The paper demonstrates the optical properties of the ytterbium doped silica glasses that were fabricated by laser sintering technology combined with liquid phase doping method, and analyzed the influence of the fabricated process on the formation of Yb2+. The spectral parameters and laser performance parameters were also calculated and analyzed. The results indicate that the formation of Yb2+ can be effectively restrained through the optimized preparation process. The prepared ytterbium doped silica glass presents typical absorption and emission cross sections of Yb3+, and possesses attractive laser performance parameters. The material would have potential applications for the gain medium of large mode area photonic crystal fiber lasers. 相似文献
94.
The time fractional wave-like differential equation with a variable coefficient is studied analytically. By using a simple transformation, the governing equation is reduced to two fractional ordinary differential equations. Then the homotopy analysis method is employed to derive the solutions of these equations. The accurate series solutions are obtained. Especially, when ?f=?g=−1, these solutions are exactly the same as those results given by the Adomian decomposition method. The present work shows the validity and great potential of the homotopy analysis method for solving nonlinear fractional differential equations. The basic idea described in this Letter is expected to be further employed to solve other similar nonlinear problems in fractional calculus. 相似文献
95.
96.
Chronic kidney disease (CKD) is a progressive systemic disease, which changes the function and structure of the kidneys irreversibly over months or years. The final common pathological manifestation of chronic kidney disease is renal fibrosis and is characterized by glomerulosclerosis, tubular atrophy, and interstitial fibrosis. In recent years, numerous studies have reported the therapeutic benefits of natural products against modern diseases. Substantial attention has been focused on the biological role of polyphenols, in particular flavonoids, presenting broadly in plants and diets, referring to thousands of plant compounds with a common basic structure. Evidence-based pharmacological data have shown that flavonoids play an important role in preventing and managing CKD and renal fibrosis. These compounds can prevent renal dysfunction and improve renal function by blocking or suppressing deleterious pathways such as oxidative stress and inflammation. In this review, we summarize the function and beneficial properties of common flavonoids for the treatment of CKD and the relative risk factors of CKD. 相似文献
97.
98.
在带有石英视窗的可变体积高压釜内,于333,353,373和393K等4个温度下,测定了3.0~15.0MPa范围内超临界CO2与碳酸二乙酯(DEC)二元体系的气-液平衡数据.结果表明,当温度恒定时,随着压力的增大,液相中超临界CO2的浓度急剧增大,气相中碳酸二乙酯的浓度缓慢增加.根据实验结果推测出了体系的pc,Tc,xc和Vc等临界性质. 相似文献
99.
通过测定产物间接测定扁桃甙,如用酶修饰电极测定产物氢氰酸和葡萄糖,其检测限均在10~(-5) mol/L。本文首次采用卷积伏安法研究了扁桃甙的水解以及产物苯甲醛的极谱行为,提高了扁桃甙的检测限。 1 仪器与试剂 XJP-821型新极谱仪(长春应用化学研究所、江苏电分析仪器厂),三电极体系,LZ3-100 相似文献
100.
Yi-Ling Tsai Siang-en Syu Shu-Mei Yang Utpal DasYu-Shiou Fan Chia-Jui LeeWenwei Lin 《Tetrahedron》2014
A Bu3P-mediated mild and efficient synthesis of multi-functional alkenes has been described starting from substituted acrylate with aldehydes. In situ generated zwitterionic intermediates underwent proton-exchange to afford ylide intermediates, which were trapped by corresponding aldehydes providing the products in up to 92% yield with complete E-stereoselectivity. Further derivatization of the products was performed to furnish functional pyridazinones. 相似文献