全文获取类型
收费全文 | 378篇 |
免费 | 9篇 |
专业分类
化学 | 290篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 34篇 |
物理学 | 51篇 |
出版年
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 20篇 |
2011年 | 21篇 |
2010年 | 14篇 |
2009年 | 17篇 |
2008年 | 26篇 |
2007年 | 8篇 |
2006年 | 23篇 |
2005年 | 14篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 11篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1971年 | 3篇 |
1961年 | 1篇 |
1959年 | 2篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有387条查询结果,搜索用时 15 毫秒
361.
362.
363.
A numerical study of ultra-short self-soliton switching along with the corresponding analysis of coupler parameters is carried
out for a Kerr coupler with intermodal dispersion. The influence of perturbations like third-order dispersion, self-steepening
and intrapulse Raman scattering, on switching characteristics is also studied.
相似文献
364.
365.
366.
N. L. Misra S. Sanjay Kumar Sangita Dhara Ajit Kumar Singh G. S. Lodha Suresh Kumar Aggarwal 《X射线光谱测定》2011,40(5):379-384
Studies on the matrix effects of uranium and thorium on the determinations of each other in their mixed oxides using energy dispersive X‐ray fluorescence (EDXRF) spectrometry with tube and radioisotope excitations of U Lα and Th Lα are reported. An internal standard method for the determination of uranium and thorium in these mixed oxides is found suitable. Comparison of the analytical results of EDXRF determinations of uranium and thorium using tube and radioisotope excitation sources has been made. The analytical methodology involves preparation of mixed oxide calibration/sample mixtures of uranium and thorium oxides, mixing of internal standard yttrium in these mixtures, pelletizing the mixtures after thorough mixing and grinding using boric acid binder and measuring EDXRF spectra of the specimens thus prepared using Rh X‐ray tube as well as 109Cd radioisotope source. The samples were analyzed for uranium and thorium on the basis of the calibration plots obtained by plotting the intensity ratios of the analyte and internal standard characteristic X‐ray lines and their corresponding amount ratios. An average precision of 1.2% (1 s RSD) was observed for the determination of U and Th and the results deviated from the corresponding expected values by 3% on average. Due to the refractory nature of thorium oxide, comparatively more grinding time was required for thorium determinations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
367.
N. L. Misra M. K. Tiwari Bal Govind Vats S. Sanjay Kumar Ajit Kumar Singh G. S. Lodha S. K. Deb P. D. Gupta S. K. Aggarwal 《X射线光谱测定》2014,43(3):152-156
A μ‐XRF study to assess the distribution of uranium and thorium in (U,Th)O2 pellets covering the composition of advanced heavy water reactor (AHWR) fuel pellets prepared by powder metallurgical compaction (PMC) and coated agglomerate pelletization (CAP) routes was made using micro‐focus beam line (BL‐16) of Indus‐2 synchrotron radiation facility. The methodology thus developed was successfully applied to these pellets. The study reveals that the uranium distribution in pellets prepared by PMC route is uniform, whereas the pellets prepared through CAP route have a wide range of compositional variation. In addition, the uniformity in CAP route‐prepared pellets improves with increase in the relative amount of uranium in the pellets. The sample preparation in present methodology is very simple compared with scanning electron microscopy. The study reveals the utility of synchrotron‐based μ‐XRF for fuel pellet characterization of AHWR reactors. Alhough CAP route of fuel pellet preparation requires less exposure of personnel to high radiation dose, the non‐uniformity in the fuel pellet must be considered when using these pellets in reactors. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
368.
Chakraborty TK Koley D Ravi R Krishnakumari V Nagaraj R Kunwar AC 《The Journal of organic chemistry》2008,73(22):8731-8744
Sugar amino acid based 24-membered macrocyclic C2-symmetric cationic peptides were designed and synthesized. The cationic group was introduced in the sugar amino acids. The conformation of these cyclic compounds was ascertained through NMR techniques, which proved they were amphipathic in nature. All the compounds were bacteriolytic, showed good activity against the Gr(+ve) and Gr(-ve) bacteria, and exhibited low hemolytic activity. 相似文献
369.
An efficient conversion of artemisinin 1 into three new amino- and hydroxy-functionalized 11-aza prototypes 9, 11, and 12 has been achieved on a multigram scale by reaction with hydrazine, hydroxylamine, and 2-amino ethanol, respectively. Of these, 9 has been further diversified into a wide range of derivatives including imines, amines, amides, and linker based dimers. Prototypes 11 and 12 have been converted into the corresponding ethers in high yields. Some of these compounds have shown a high order of activity against multidrug-resistant malaria in mice by oral route. 相似文献
370.
V Kumar A Kumar U Diwan KK Upadhyay 《Chemical communications (Cambridge, England)》2012,48(76):9540-9542
The mechanism of optical detection of HSO(4)(-) in aqueous medium by Schiff-base receptors has previously been proposed to depend on selective hydrogen-bond interactions. Here, we clearly demonstrate for the first time that the acidic nature of this anion gives rise to hydrolysis of the Schiff base, which leads to the optical changes observed in this family of receptors. 相似文献