全文获取类型
收费全文 | 428篇 |
免费 | 35篇 |
国内免费 | 42篇 |
专业分类
化学 | 271篇 |
晶体学 | 6篇 |
力学 | 45篇 |
数学 | 31篇 |
物理学 | 152篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 7篇 |
2020年 | 21篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 4篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 22篇 |
2013年 | 24篇 |
2012年 | 33篇 |
2011年 | 48篇 |
2010年 | 19篇 |
2009年 | 22篇 |
2008年 | 29篇 |
2007年 | 21篇 |
2006年 | 20篇 |
2005年 | 22篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有505条查询结果,搜索用时 15 毫秒
51.
多孔有限大弹性薄板弯曲应力集中问题 总被引:3,自引:0,他引:3
应用弹性力学的复变函数理论,采用多保角变换的方法,推出了含有任意多孔有限大弹性薄板弯曲的多复变量应力函数的表达式.在内边界上进行复Fourier级数展开,在外边界采用配点法来确定应力函数的未知系数,从而计算有限大弹性薄板的应力场.本文以外边界为矩形,内边界为任意多椭圆孔的有限薄板为例,编制了相应的计算程序,进行了算例分析.结果表明本方法对处理多孔有限大弹性平面问题是简单且行之有效的. 相似文献
52.
借助边界元法设计了一种迭代修正方法来求解单侧界面裂纹模型与弹性波的相互作用问题,作为对算法的检验,用这种方法我们具体地分析了平面简谐弹性波对一个单侧界面裂纹的入射,给出了裂纹面的接触形态及应力场. 相似文献
53.
Ni(OAc)2 was found to be an efficient catalyst for the synthesis of β‐enamino ketones or esters from β‐dicarbonyl compounds and amines under solvent‐free conditions. The reusability of the catalyst was successfully examined without noticeable loss of its catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
54.
Zhi‐Yong Guo Pan‐Pan Gai Jing Duan Jin‐Xia Zhai Sha‐Sha Zhao Sui Wang Dan‐Yi Wei 《Biomedical chromatography : BMC》2010,24(10):1094-1099
A gas chromatography–mass spectrometry assay was developed and validated for the simultaneous determination of phthalates and adipates in human serum. The phthalates and adipates studied were dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzylbutyl phthalate, di‐2‐ethylhexyl phthalate, di‐n‐octyl phthalate, diethyl adipate, dibutyl adipate, diisobutyl adipate, bis(2‐butoxyethyl) adipate and di‐2‐ethylhexyl adipate, with diisooctyl phthalate as internal standard. The extraction and cleaning up procedure was carried out with solid‐phase extraction cartridges containing dimethyl butylamine groups, which showed extraction efficiencies over 88% for each analyte and the internal standard. The calibration curves obtained were linear with correlation coefficients greater than 0.98. For all analytes, the assay gave CV% values for intra‐day precision from 4.9 to 13.3% and mean accuracy values from 91.4 to 108.4%, while inter‐day precision was 5.2–13.4% and mean accuracy 91.0–110.2%. The limits of detection for the assay of phthalates and adipates were in the range 0.7–4.5 ng/mL. The method is simple, sensitive and accurate, and allows for simultaneous determination of nanogram levels of phthalates and adipates in human serum. It was successfully applied to an investigation on the level of phthalates and adipates in a non‐occupationally exposed population. 相似文献
55.
磷光光度法在药物分析中的应用 总被引:4,自引:1,他引:3
本文评述了固体基质室温磷光,流体介质室温磷光,低温磷光和室温磷光传感器在药物分析中的应用,涉及到的药物有生物碱,中草药有效成分,四环素类,喹喏酮类,维生素B2,抗癌药物,萘唑啉,萘普生和血管扩张剂潘生丁双嘧哌胺醇等,在药物分析中,固体基质室温磷光取样量只有微升级,操作快,成本低,流体室温磷光结合流动注射和化学传感技术,在药物的快速连续在线监测方面优势明显,而经过改善的低温磷体室温磷光结合流动注射和化学传感技术,在药物的快速连续在线监测方面优势明显,而经过改善的低温磷光方法,除了克服操作方面的某些弱点外,仍然保持高灵敏度的特点,随着敏化和猝死发光,能量转移,衍生发光和免疫发光等技术的发展,磷光方法在药物分析中的应用将会更加广泛。 相似文献
56.
For calculating the stiffness function of a structure, the differential equation of the vibration of the structure was divided into the differential equation on the original stiffness function that was known, and Fredholm integral equation of the first kind on the undetermined stiffness function that was unknown. And the stable solutions of the integral equation, when the smooth factor was equal to zero, was solved by the extrapolation with p smooth factors. So the stiffness function of the structure is obtained. Applied examples show that the method is feasible and effective. 相似文献
57.
Three unprecedented nitronyl nitroxide radical‐bridged 3d–4f clusters, [Ln2Cu2(hfac)10(NIT‐3py)2(H2O)2](LnIII=Y, Gd, Dy), have been obtained from the self‐assembly of Ln(hfac)3, Cu(hfac)2, and the radical ligand. The Dy complex shows a slow relaxation of magnetization, representing the first nitronyl nitroxide radical‐based 3d–4f cluster with single‐molecule magnet behavior. 相似文献
58.
59.
This paper presents the results of an experimental study on the heat transfer and pressure drop in diagonally finned tube banks. The investigations have been carried out using the napthalene analogy. The performance of a heat exchanger with fins arranged a certain angle to the flow direction with the plain tube heat exchanger have been compared. 相似文献
60.