全文获取类型
收费全文 | 1833篇 |
免费 | 188篇 |
国内免费 | 111篇 |
专业分类
化学 | 1323篇 |
晶体学 | 10篇 |
力学 | 119篇 |
综合类 | 18篇 |
数学 | 187篇 |
物理学 | 475篇 |
出版年
2024年 | 5篇 |
2023年 | 30篇 |
2022年 | 42篇 |
2021年 | 50篇 |
2020年 | 59篇 |
2019年 | 55篇 |
2018年 | 46篇 |
2017年 | 42篇 |
2016年 | 58篇 |
2015年 | 71篇 |
2014年 | 105篇 |
2013年 | 129篇 |
2012年 | 148篇 |
2011年 | 148篇 |
2010年 | 87篇 |
2009年 | 87篇 |
2008年 | 127篇 |
2007年 | 135篇 |
2006年 | 118篇 |
2005年 | 86篇 |
2004年 | 64篇 |
2003年 | 56篇 |
2002年 | 45篇 |
2001年 | 38篇 |
2000年 | 45篇 |
1999年 | 28篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 20篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1958年 | 3篇 |
1956年 | 2篇 |
排序方式: 共有2132条查询结果,搜索用时 31 毫秒
61.
Suji Lee Ryeong Ha Kwon Ju Hyung Kim Hyemin Na So-Jeong Lee Yu-Mi Choi Hyemyeong Yoon So Young Kim Yong-Suk Kim Sang Hoon Lee Seon Mi Yoo Heon-Woong Kim Chi-Do Wee 《Molecules (Basel, Switzerland)》2022,27(13)
In this study, thirty-eight isoflavone derivatives were comprehensively identified and quantified from the raw, steamed and fermented seeds of four selected soybean cultivars based on UPLC-DAD-QToF/MS results with reference to the previously reported LC-MS library and flavonoid database, and summarized by acylated group including glucosides (Glu), malonyl-glucosides (Mal-Glu), acetyl-glucosides (Ac-Glu), succinyl-glucosides (Suc-Glu) and phosphorylated conjugates (Phos) in addition to aglycones. Among them, Suc-Glu and Phos derivatives were newly generated due to fermentation by B. subtilis AFY-2 (cheonggukjang). In particular, Phos were characterized for the first time in fermented soy products using Bacillus species. From a proposed roadmap on isoflavone-based biotransformation, predominant Mal-Glu (77.5–84.2%, raw) decreased rapidly by decarboxylation and deesterification into Ac-Glu and Glu (3.5–8.1% and 50.0–72.2%) during steaming, respectively. As fermentation continued, the increased Glu were mainly succinylated and phosphorylated as well as gradually hydrolyzed into their corresponding aglycones. Thus, Suc-Glu and Phos (17.3–22.4% and 1.5–5.4%, 36 h) determined depending on cultivar type and incubation time, and can be considered as important biomarkers generated during cheonggukjang fermentation. Additionally, the changes of isoflavone profile can be used as a fundamental report in applied microbial science as well as bioavailability research from fermented soy foods. 相似文献
62.
余弦二值编码纯相位全息图的数字微镜器件显示 总被引:1,自引:0,他引:1
分析了采用错误减算法的迭代过程,在已知物波函数傅里叶谱的振幅和物波函数振幅的情况下恢复出纯相位的物波函数,最大限度地保留物波的振幅及相位信息.提出采用余弦二值编码生成二值全息图,即全息图的透射率函数取0或1.二值全息图通过数字微镜器件全息显示系统进行了重构显示,重构效果很好.理论分析了数字微镜器件的衍射效率,表明其最大衍射效率仅和微镜之间的间隔尺寸与微镜边长之比有关.余弦二值编码方法从理论上消除了零级衍射,可以制作像素较多的全息图. 相似文献
63.
Yu Xiangtao Yang Jun Sui Zhuyin Wang Mingyong 《Journal of Solid State Electrochemistry》2021,25(8):2201-2212
Journal of Solid State Electrochemistry - Self-supporting porous Ni film with uniform honeycomb-like micropores and a thickness of up to 66 μm is electrodeposited by dynamic hydrogen... 相似文献
64.
DNA methylation is the most promising biomarker for estimating human age. There are various methods used for analyzing DNA methylation. Among those, the SNaPshot assay-based method provides a semi-quantitative measurement of DNA methylation using capillary electrophoresis on genetic analyzers. However, DNA methylation measures produced using different types of genetic analyzers have never been compared, although differences in methylation values can directly affect age estimates. To evaluate the differences between the results generated by different genetic analyzers, we analyzed the same blood, saliva, and control methylated DNA using three genetic analyzers—the Applied Biosystems 3130, 3500, and SeqStudio—and compared the methylation values at five CpG sites: ELOVL2, FHL2, KLF14, MIR29B2C, and TRIM59. The methylation value at each of the five CpG sites decreased in the order 3130, 3500, and SeqStudio. The differences in the results produced by the different genetic analyzers resulted in significant errors when applying the 3500 and SeqStudio data to a previous age estimation model constructed using the 3130 Genetic Analyzer data. Therefore, DNA methylation measurements from 3500 and SeqStudio were corrected using the regression functions obtained by plotting the DNA methylation data of one instrument versus the other to facilitate the application of DNA methylation data from one instrument to the age prediction model based on other instruments. The age prediction accuracy obtained by applying corrected 3500 and SeqStudio data to the existing age estimation model was as high as observed in the 3130 data. 相似文献
65.
66.
67.
Yuanting Su Xingyong Wang Xin Zheng Zaichao Zhang You Song Yunxia Sui Yizhi Li Xinping Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(11):2901-2905
Three bis(triarylamine) dications were isolated by using weakly coordinating anions. Their electronic structures in the ground state were investigated by various experiments in conjunction with theoretical calculations. The ground‐state electronic structures of these species were tunable by substituent effects, with two of them as closed‐shell singlets and one of them as an open‐shell singlet in the solid state. The excited state of the latter is thermally accessible, indicated by EPR and SQUID measurements. The work provides a new and stable diradicaloid structure motif with an excited triplet sate. 相似文献
68.
Investigation on the stress behavior of cellulose acetate and the development of highly moisture‐resistant optical films for display devices
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Min Sang Park Seokwon Jung So Jeong Heo Seung Geol Lee 《Journal of Polymer Science.Polymer Physics》2017,55(19):1470-1479
An optical film with high optical anisotropy was prepared by the stretching of a cellulose acetate film and the consequential orienting of a retardation‐enhancing additive. The change in retardation in response to moisture absorption was explored and it was found that the degree of the retardation variation is strongly related to the stretching temperature. Stress generated by the stretching and its relaxation was systematically investigated to elucidate the effect of stretching temperature on the irreversible change in retardation upon moisture absorption. The results show that the magnitude of releasable stress plays an important role in controlling changes in optical properties. In addition, the difference in the deformation behavior between glassy and rubbery states should be taken into account in the development of a moisture‐resistant optical film. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1470–1478 相似文献
69.
70.
Chao Zuo Qian Chen Guohua Gu Xiubao Sui Jianle Ren 《Infrared Physics & Technology》2012,55(4):263-269
In this paper, an improved interframe registration based nonuniformity correction algorithm for focal plane arrays is proposed. The method simultaneously estimates detector parameters and carries out the nonuniformity correction by minimizing the mean square error between the two properly registered image frames. A new masked phase correlation algorithm is introduced to obtain reliable shift estimates in the presence of fixed pattern noise. The use of an outliers exclusion scheme, together with a variable step size strategy, could not only promote the correction precision considerably, but also eliminate ghosting artifacts effectively. The performance of the proposed algorithm is evaluated with clean infrared image sequences with simulated nonuniformity and real pattern noise. We also apply the method to a real-time imaging system to show how effective it is in reducing noise and the ghosting artifacts. 相似文献