全文获取类型
收费全文 | 194篇 |
免费 | 6篇 |
专业分类
化学 | 122篇 |
数学 | 4篇 |
物理学 | 74篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2007年 | 9篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 14篇 |
2003年 | 11篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 1篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有200条查询结果,搜索用时 281 毫秒
41.
42.
The surface electronic state on the stepped surface of Cu(755) has been investigated by means of angle-resolved ultraviolet photoelectron spectroscopy using synchrotron radiation(SR-ARUPS). We have observed a free-electron-like surface state below the Fermi level. In spite of the anisotropy of the atomic arrangement due to steps, the surface state is shown to be isotropic since the dispersion profile and the peak shape are almost identical in the directions parallel and perpendicular to the steps. This result makes a clear contrast with the previous SR-ARUPS results on Ni(755) surfaces which have the surface structure similar to Cu(755). Those experimental evidences are discussed based upon the electron configurations of both metal substrates. 相似文献
43.
To study noise-induced sleep disturbance, a new procedure called “noise interrupted method”has been developed. The experiment is conducted in the bedroom of the house of each subject. The sounds are reproduced with a mini-disk player which has an automatic reverse function. If the sound is disturbing and subjects cannot sleep, they are allowed to switch off the sound 1 h after they start to try to sleep. This switch off (noise interrupted behavior) is an important index of sleep disturbance. Next morning they fill in a questionnaire in which quality of sleep, disturbance of sounds, the time when they switched off the sound, etc. are asked. The results showed a good relationship between LAeq and the percentages of the subjects who could not sleep in an hour and between LAeq and the disturbance reported in the questionnaire. This suggests that this method is a useful tool to measure the sleep disturbance caused by noise under well-controlled conditions. 相似文献
44.
M. Takai Y. F. Lu T. Koizumi S. Namba S. Nagatomo 《Applied Physics A: Materials Science & Processing》1988,46(3):197-205
Single crystal ferrite has been etched by focused Ar+ laser irradiation in a CCl4 gas atmosphere. The etched groove showed cracks due to thermal stresses when samples were etched by a laser vaporization process in a vacuum, while in a CCl4 atmosphere, such cracks were not observed. An etching rate of 68 /s obtained for a thermochemical process by laser irradiation was four orders of magnitude higher than that for a wet chemical etching process. A high aspect (depth-to-width) ratio of up to 10 was obtained for etched grooves. Under specific conditions, bending of the groove and orientation dependence in etching rate were observed. 相似文献
45.
Racemic α-monosubstituted cyclopentanones were converted to optically active forms by a thermodynamically controlled deracemization using TADDOL-type host molecule 1 in alkaline aqueous MeOH. The efficiency of this conversion was strongly influenced by the ratio of the solvent components (H2O/MeOH) and the functionality and architecture of the α-side-chain on the cyclopentanones. For example, (R)-2-(2-benzyloxyethyl)cyclopentanone (9) was obtained in 89% yield with 97% ee using a 7:3 mixture of H2O/MeOH as the solvent. X-ray analytical studies were also carried out and disclosed the nature of this chiral molecular recognition process in the solid phase. 相似文献
46.
The martensitic phase of 301 stainless steel has been locally transformed into the austenitic phase by irradiating it with a focused Ar-ion laser beam in order to investigate the local change of magnetic properties accompanying the phase transformation. The intensity of the magnetic signal was found to locally reduce at a laser power of 350 mW and almost extinguish at 550 mW with a beam spot size of 13.2 m (at 1/e intensity), indicating the local austenitic phase transformation of the irradiated stainless steel.On leave from Ltd., Shimoteno, Himeji, Hyogo 670, Japan 相似文献
47.
Reactions of pyridine N-oxides, pyrazine di-N-oxides, and their benzologues with formamide are described. Carbamoylation mainly occurred at aromatic ring with loss of the N-oxide oxygen atom, however, 2,4,6-trimethylpyridine 1-oxide gave 2- and 4-pyrimidinyl derivatives. 相似文献
48.
Z M Gu D X Zhang X W Yang M Hattori T Namba 《Chemical & pharmaceutical bulletin》1990,38(9):2498-2502
From the ether extract of the underground part of Notopterygium forbesii, two new coumarin glycosides, bergaptol-O-beta-D-glucopyranoside and 6'-O-trans-feruloylnodakenin, were isolated along with known compounds including seven furanocoumarins, two dihydrofuranocoumarins, a sterol glucoside and two phenolic compounds. Analysis of their contents by high-performance liquid chromatography (HPLC) revealed that the underground part of N. forbesii contained large amounts of p-hydroxphenethyl anisate (0.7%), bergaptol glucoside (0.2%), nodakenin (2%) and 6'-O-trans-feruloylnodakenin (0.7%) and a lesser amount of notopterol (0.08%), while that of N. incisum contained a large amount of notopterol (1.2%) and less amounts of the others. The characteristic difference in chemical composition between the two species enabled us to identify the respective botanical sources of a Chinese crude drug, Qiang-huo derived from N. incisum and N. forbesii by HPLC. 相似文献
49.
The performance of a capillary magnetophoretic device was improved by enhancing the magnetic field gradient using a pair of small iron tips attached to the Nd-Fe-B magnets. The magnetophoretic intensity, B(dB/dx), was determined as a function of distance along the gap between the tips from the magnetophoretic velocity of a 3 microm polystyrene microparticle in 0.6 M manganese(II) chloride solution. The maximum intensity was increased 4.5 times by the attached iron pieces. The magnetophoresis of a single human blood cell in 0.1 M manganese(II) solution was studied by this method and its magnetic susceptibility was estimated. Magnetophoretic trapping of red blood cells was demonstrated under counter-current flow conditions in the capillary. 相似文献
50.