全文获取类型
收费全文 | 756篇 |
免费 | 27篇 |
国内免费 | 2篇 |
专业分类
化学 | 588篇 |
晶体学 | 6篇 |
力学 | 9篇 |
数学 | 16篇 |
物理学 | 166篇 |
出版年
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 16篇 |
2019年 | 20篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 21篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 47篇 |
2012年 | 40篇 |
2011年 | 45篇 |
2010年 | 26篇 |
2009年 | 32篇 |
2008年 | 35篇 |
2007年 | 30篇 |
2006年 | 33篇 |
2005年 | 28篇 |
2004年 | 29篇 |
2003年 | 27篇 |
2002年 | 30篇 |
2001年 | 23篇 |
2000年 | 11篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1987年 | 8篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1930年 | 4篇 |
排序方式: 共有785条查询结果,搜索用时 31 毫秒
111.
Vanadium content of the eggs and embryos of ascidian, Halocynthia roretzi was determined by activation analysis. The determination
was performed by the comparison of the activity around 1.434 MeV peak of52V in the sample to that of the standard. The concentration of vanadium in the eggs remained unchanged during the cleavage
stage and the animal accumulated it progressively in the early embryogenesis. The content in the larvae after metamorphosis
amounted to nearly fifteen times of that of the unfertilized eggs. 相似文献
112.
113.
Yukio Inoue Hirokazu Hori Takeki Sakurai Yukiko Tokitomo Junko Saito Taku Misonou 《Optical Review》2002,9(2):75-80
Optical properties of an ultraviolet-absorbing substance (UVAS) extracted from the marine red alga, Porphyra yezoensis, have been investigated. The substance is excited by UV light, and the emitted fluorescence is detected using an intelligent fluorescence detector. The fluorescence of UVAS is weaker by four orders of magnitude than the fluorescence intensity emitted by anthracene in the same optical system. The absorbed energy is apparently not transferred to the photosynthesis process and is believed to be consumed as heat. Using photothermal spectroscopy, a signal is observed indicating that the absorbed photon energy has transferred to the heat. The waveform of the photothermal signal of UVAS is similar to that of quinoxaline, whose fluorescence quantum yield is known to be zero. It is determined that the fluorescence quantum yield and the energy of the triplet state of UVAS are 1.7 ± 0.7 ± 10−4 and 21000 ± 1000 cm −1, respectively. The conclusion is that the excited molecules of UVAS decay by passing through the triplet state and dissipate all absorbed energy as heat. 相似文献
114.
Mikio Hori Tadashi Kataoka Hiroshi Shimizu Kiminori Tomimatsu 《Tetrahedron letters》1982,23(8):901-904
The isolates cis- and trans-9phenylselenoxanthene-N-arylsulfonylselenilimines were not interconverted thermally. cis-Isomers were converted to trans-isomers by chloramine-T or -B in a fashion of SN2 type substitution. cis-Isomers did not rearrange but trans-isomers rearranged thermally to 9-arylsulfonamido-9-phenylselenoxanthenes, whereas both isomers underwent the base-catalyzed intermolecular rearrangement. 相似文献
115.
Non-stereospecific ring expansions of 3-acetylbenzothiazoline sulfoxides to benzothiazines from the reaction with acetic anhydride are reported. 相似文献
116.
117.
118.
119.
Mikio Hori Tadashi Kataoka Hiroshi Shimizu Sachio Ohno Kenichi Narita Hiroaki Takayanagi Haruo Ogura Yoichi Iitaka 《Tetrahedron letters》1979,20(44):4315-4318
The first success of an X-ray analysis of a thiabenzene derivative, 1-benzoyl-2-methyl-2-thianaphthalene is described. 相似文献
120.
The formation and electrolytic reduction of molybdophosphate in aqueous solutions of various water-miscible organic solvents have been extensively investigated. Acetonitrile was found to be the most useful of these solvents. Two species of molybdophosphate are formed in aqueous acetonitrile, one of which changes spontaneously into the other, which is quite stable and undergoes a 2-electron electrolytic reduction. On the basis of these facts, a flow-coulometric method for orthophosphate has been developed, applicable to the range 5 × 10−6-1 × 10−3M. It has been used for determination of orthophosphate in several phosphorus compounds, some of which are acid-labile. 相似文献