全文获取类型
收费全文 | 1619篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
化学 | 874篇 |
晶体学 | 22篇 |
力学 | 49篇 |
数学 | 73篇 |
物理学 | 353篇 |
无线电 | 272篇 |
出版年
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 19篇 |
2018年 | 23篇 |
2017年 | 14篇 |
2016年 | 35篇 |
2015年 | 15篇 |
2014年 | 34篇 |
2013年 | 56篇 |
2012年 | 105篇 |
2011年 | 177篇 |
2010年 | 133篇 |
2009年 | 131篇 |
2008年 | 136篇 |
2007年 | 111篇 |
2006年 | 99篇 |
2005年 | 95篇 |
2004年 | 81篇 |
2003年 | 34篇 |
2002年 | 27篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 34篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1936年 | 3篇 |
排序方式: 共有1643条查询结果,搜索用时 0 毫秒
1.
2.
3.
N. Ponpandian A. Narayanasamy D. Prabhu K. Ganesan M. Manivel Raja K. Chattopadhyay 《Journal of magnetism and magnetic materials》2006
The Fe73.5Cu1Nb3Si13.5B9 FINEMET alloy has been prepared by the rapid solidification technique. The critical behaviour of this alloy in the amorphous as well as in its nanocrystalline states has been studied near their respective Curie temperatures. From the values of the critical exponents one can conclude that the alloy behaves like a 3D Heisenberg ferromagnet in the amorphous and nanocrystalline states. But there exists a slight increase in the value of β for the alloy annealed at 823 K (the nanocrystalline state) as observed in most of the amorphous alloys. 相似文献
4.
5.
Milind V. Kulkarni Annamraju Kasi Viswanath R. Marimuthu Tanay Seth 《Journal of polymer science. Part A, Polymer chemistry》2004,42(8):2043-2049
Spectroscopic [UV–visible and Fourier transform IR (FTIR)] and thermal properties of chemically synthesized polyanilines are found to be affected by varying the protonation media (acetic, citric, oxalic, and tartaric acid). The optical spectra show the presence of a greater fraction of fully oxidized insulating pernigraniline phase in polyaniline doped with acetic acid. In contrast, the selectivity in the formation of the conducting phase is higher in oxalic acid as a protonic acid media. The FTIR spectra of these polymers reveal a higher ratio of the relative intensities of the quinoid to benzenoid ring modes in acetic acid doped polyaniline. Scanning electron micrographs revealed a sponge‐like structure derived from the aggregation of the small granules in acetic acid and oxalic acid doped polyaniline. A three‐step decomposition pattern is observed in all the polymers, regardless of the protonic acid used for the doping. The second step loss related to the loss of dopant is found to be higher in the oxalic acid doped polymer. In accordance with these results the conductivity is also found to be higher in oxalic acid doped material. The temperature dependent conductivity measurements show the thermal activated behavior in all the polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2043–2049, 2004 相似文献
6.
A convenient and enantioselective synthesis of ethyl (8RS, 15R)-8-acetoxy-15-hydroxyhexadecanoate15 via a chemoenzymatic approach has been described. The salient features of the synthesis were operational simplicity, use of easily accessible materials, and excellent enantiocontrol via lipase catalyzed acetylation of 2-alkanol. 相似文献
7.
8.
9.
J. Mohanty H. Pal S. K. Nayak S. Chattopadhyay A. V. Sapre 《Chemical physics letters》2003,370(5-6):641-646
Fluorescence quenching of methoxycalixarenes (MOCX) by chloroalkanes (CA) has been investigated in acetonitrile solutions. Observed quenching is attributed to photoinduced dissociative electron transfer (DET) interaction, which is supported by the characterization of the Cl− ions and by the radical scavenging experiments. Comparing the Cl− yields with different DET systems, it is inferred that both concerted and stepwise DET mechanisms operate simultaneously in MOCX–CA systems. A correlation of the quenching constants with the free-energy changes following a suitable DET theory supports the above inference. 相似文献
10.