全文获取类型
收费全文 | 208篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
化学 | 169篇 |
力学 | 3篇 |
数学 | 8篇 |
物理学 | 39篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2012年 | 11篇 |
2011年 | 10篇 |
2010年 | 12篇 |
2009年 | 5篇 |
2008年 | 16篇 |
2007年 | 22篇 |
2006年 | 7篇 |
2005年 | 11篇 |
2004年 | 14篇 |
2003年 | 9篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有219条查询结果,搜索用时 0 毫秒
61.
Teruyuki Yorioka 《Archive for Mathematical Logic》2003,42(7):695-710
We prove that the covering number of the Marczewski ideal is equal to 1 in the extension with the iteration of Hechler forcing. 相似文献
62.
Hirobumi Takahashi Takehiro Fukami Hisaki Kojima Takeru Yamakawa Hiroyuki Takahashi Toshihiro Sakamoto Teruyuki Nishimura Masayuki Nakamura Takashi Yosizumi Kenji Niiyama Norikazu Ohtake Takashi Hayama 《Tetrahedron》2005,61(14):3473-3481
A robust synthetic method for 2-alkylamino-6-carboxy-5,7-diarylcyclopenteno[1,2-b]pyridines via acylamination at the alpha position of the functionalized pyridine system has been developed. The key step in this method was achieved by treatment of the corresponding pyridine N-oxides with 2.5 equiv of imidoyl chlorides in the presence of triethylamine, thus producing the desired 2-acylaminopyridines in good yields (74-96%). 相似文献
63.
64.
65.
FK888 (NK1 antagonist) is a candidate drug for migraine and selected as a model of amorphous drug. FK888 was micronized to develop as dry powder inhalers (DPIs) taking into consideration of its water insoluble property. The glass transition temperature (Tg) and fragility (m) were 90 degrees C and 118, respectively, and it was categorized as a fragile glass based on Angell's concept. FK888 was structurally relaxed by aging below Tg, then the effect of aging on their physical and aerosol properties were investigated. The investigation on the moisture sorption-desorption isotherms of FK888 indicated that aged FK888 adsorbed less amount of water than that of unaged FK888. This unique moisture sorption-desorption behavior of the aged sample is explained by structural relaxation accompanying decrease of free volume and/or increase of density. As for the dissolution rate of unaged and aged FK888, they showed the similar value, suggesting that there would be no difference in bioavailability. In relation to the stability, FK888 DPIs prepared by unaged and aged FK888 were stored at 70 degrees C, and the respirable fraction of FK888 DPIs was evaluated by using multistage cascade impactor (USP apparatus 3). As a result, the respirable fraction of FK888 DPIs prepared by unaged sample was significantly decreased compared to the aged sample, suggesting that agglomeration may occur in the unaged sample during the storage. This phenomenon was supported by that the unaged sample showed a significant decrease in the surface area compared to that of the aged sample when stored at various conditions. 相似文献
66.
67.
68.
Colloidally dispersed niobate nanosheets with the thickness of 1.8 nm and controlled mean lateral sizes of 0.15-7.8 mum were prepared and their liquid crystallinity was examined. The nanosheet colloids with different lateral sizes were obtained by exfoliation of single crystals of layered niobate K4Nb6O17 and subsequent ultrasonication. Naked-eye and microscope observations of the nanosheet colloids between crossed polarizers revealed liquid crystallinity of the sols characterized by birefringence as functions of the lateral sizes and concentration of the nanosheets. The nanosheet colloids with smaller lateral sizes (0.15-1.9 mum) varied from isotropic to biphasic (isotropic + liquid crystalline), and finally to fully liquid crystalline states as the colloid concentration increased. The phase transition concentrations (from isotropic to biphasic and biphasic to liquid crystalline) decreased with increasing aspect ratio (lateral-to-thickness ratio) of the nanosheets, almost in accordance with the prediction by Onsager theory, indicating that the liquid crystallinity is explained basically by excluded-volume effect between the nanosheets. On the other hand, the colloids with larger lateral sizes (6.2 and 7.8 mum) stably kept liquid crystalline state even at very low concentration (5.1 x 10-6 in volume fraction), which was much lower than that expected from the theory. 相似文献
69.
In their work on spreading models in Banach spaces, Dilworth et al. (Isr J Math 161:387–411, 2007) introduced the notion of a Suslin lower semi-lattice, a seemingly slight weakening of the notion of a Suslin tree. They posed several problems of a set theoretic nature regarding their notion. In this paper, we make a systematic study of the notion of Suslin lower semi-lattice, answering some of the questions raised by Dilworth, Odell, and Sari. 相似文献
70.
Jun-Ichi Matsumoto Teruyuki Miyamoto Akira Minamida Yoshiro Nishimura Hiroshi Egawa Haruki Nishimura 《Journal of heterocyclic chemistry》1984,21(3):673-679
Fluorination of the 2,6-disubstituted 3-aminopyridines 5 and 12 by the Balz-Schiemann reaction is described. 2,6-Dichloro-3-pyridinediazonium tetrafluoroborate ( 6 ) and 2-substituted 6-acetylamino-3-pyridinediazonium tetrafluoroborates 13 were heated with or without a solvent to give the corresponding fluorinated pyridines 7 and 14 , respectively, in good yields. 2-Substituted 6-acetylamino-3-fluoropyridines ( 14 ) were converted by a known method into a series of 7-substituted 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids 21 including enoxacin [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3-carboxylic acid [( 2 )], a new potential antibacterial agent. 相似文献