全文获取类型
收费全文 | 351篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 278篇 |
力学 | 3篇 |
数学 | 13篇 |
物理学 | 65篇 |
出版年
2022年 | 6篇 |
2021年 | 3篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 11篇 |
2011年 | 26篇 |
2010年 | 12篇 |
2009年 | 9篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 25篇 |
2003年 | 17篇 |
2002年 | 16篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有359条查询结果,搜索用时 15 毫秒
271.
Takao Yamazaki Hiroki Takahata Yoko Hama Yoshiaki Takano Masanori Nagata Raymond N. Castle 《Journal of heterocyclic chemistry》1979,16(3):525-526
The condensation of 1-aminoethyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline 1 with 1,2-cyclohexanedione 2 gave the 8,12-diaza- D -homosteroid system 3 , which was reduced with Adams' catalyst followed by acetic anhydride acetylation to afford the 8,12-diaza- D -homosteroids 4a,b . 相似文献
272.
We demonstrate that two-photon fluorescence microscopy is a useful tool for monitoring the diffusion of molecules through polymeric solid supports. As a proof of principle, TentaGel beads were bound to a cover slip, and diffusion of Rhodamine 6G through single beads was observed in real time. Diffusion experiments performed in 40 different beads indicate that there is a considerable degree of heterogeneity in diffusion rates from bead to bead. 相似文献
273.
Swelled plastics in supercritical carbon dioxide provide unique environments for stabilizing palladium and rhodium nanoparticles and for catalytic hydrogenation. Complete hydrogenation of benzene to cyclohexane can be achieved in 10 minutes using the plastic stabilized Rh nanoparticles at 50 degrees C in supercritical CO(2). High efficiency, reusability, and rapid separation of products are some advantages of the plastic stabilized metal nanoparticles for catalytic hydrogenation in supercritical CO(2). 相似文献
274.
FUNCTIONAL ROLE OF CALCIUM IN PHOTORECEPTOR CELLS 总被引:1,自引:0,他引:1
Naomasa Miki Che-Hui Kuo Yokichi Hayashi Mariko Akiyama 《Photochemistry and photobiology》1980,32(4):503-508
Abstract— Ca-uptake by disc membranes prepared from frog rod photoreceptor outer segments was examined. Ca-uptake study revealed two affinity sites which were saturated with 10–5 M and 10–3 M of ATP. When disc membranes in 20 m M Tris-HCl buffer (pH 7.5) were stored at -20°C for 6 h, more than 95% of Ca-uptake activity was lost. Ca-uptake activity was, however, preserved if the disc membrane suspension was mixed with 1–10m M ATP and stored at -20°C. Furthermore the reactivation of Ca-uptake was observed if disc membranes, which had lost Ca-uptake ability by storing at 4°C for 3 h, were mixed with 10 m M ATP and then frozen at -20°C for 5 h or 28 h (ATP-induced ATP-dependent Ca-uptake). When the contents of ATP bound to disc membranes were measured during a brief aging at 37°C, the decrement of bound ATP content was correlated well with the decreasing of Ca-uptake activity. Carbonylcyanide m -chlorophenylhydrazone (CCCP), a conductor of protons, inhibited Ca-uptake activity and half maximal inhibition was achieved at 2 × 10–8 M. When 10–6 M of CCCP was added to the 45 Ca-accumulated disc membranes, rapid release of 45 Ca from the disc membranes was observed. These results suggest that ATP may play a role in the Ca-pump regulation in disc membranes and a [H+ ] gradient across disc membrane may be linked to Ca-uptake mechanism. 相似文献
275.
New iridoids from Gelsemium species 总被引:1,自引:0,他引:1
Kogure N Ishii N Kobayashi H Kitajima M Wongseripipatana S Takayama H 《Chemical & pharmaceutical bulletin》2008,56(6):870-872
Four new iridoids structurally related to gelsemide (5) were isolated from two Loganiaceous plants, Gelsemium elegans and G. rankinii. Among them, GEIR-1 (1) has a novel tetracyclic caged structure. 相似文献
276.
The first total synthesis of (+/-)-psychotrimine, a novel trimeric indole alkaloid isolated from Psychotria rostrata, was achieved. In the total synthesis, the copper-mediated intramolecular and intermolecular aminations of halobenzenes, which respectively contributed to the construction of a pyrrolidinoindoline core and the installation of a third tryptamine unit, were used as key steps. 相似文献
277.
Production of gaseous OH radicals in the 248-350 nm photoirradiation of NO3(-) doped on amorphous ice at 100 K was monitored directly by using resonance-enhanced multiphoton ionization. The translational energy distribution of the OH product was represented by a Maxwell-Boltzmann energy distribution with the translational temperature of 3250 +/- 250 K. The rotational temperature was estimated to be 175 +/- 25 K. We have confirmed that the OH production should be attributed to the secondary photolysis of H2O2 produced on ice surface on the basis of the results of controlled photolysis experiments for H2O2 doped on ice surface. 相似文献
278.
279.