全文获取类型
收费全文 | 568篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
化学 | 438篇 |
晶体学 | 6篇 |
力学 | 5篇 |
数学 | 12篇 |
物理学 | 131篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 16篇 |
2014年 | 23篇 |
2013年 | 30篇 |
2012年 | 21篇 |
2011年 | 32篇 |
2010年 | 20篇 |
2009年 | 21篇 |
2008年 | 32篇 |
2007年 | 17篇 |
2006年 | 35篇 |
2005年 | 30篇 |
2004年 | 38篇 |
2003年 | 37篇 |
2002年 | 30篇 |
2001年 | 19篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1990年 | 6篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1974年 | 3篇 |
1966年 | 1篇 |
1960年 | 1篇 |
1929年 | 2篇 |
排序方式: 共有592条查询结果,搜索用时 15 毫秒
531.
Koji Suzuki Hiroyuki Ohzora Koji Tohda Kyota Miyazaki Kazuhiko Watanabe Hidenari Inoue Tsuneo Shirai 《Analytica chimica acta》1990
A novel lipophilic anionic dye, N-2,4-dinitro-6-octyloxyphenyl-2′,4′-dinitro-6′-trifluoromethylphenylamine (LAD), was synthesized. On deprotonation at neutral Ph it forms anions and brings about a change in the absorption spectrum in the visible region. This anionic dye was incorporated into a poly(vinyl chloride) matrix membrane with dibenzo-18-crown-6 (DB18C6) or valinomycin, which are K+-selective neutral ionophores. An optical K+ sensor was prepared using the polymeric membrane set 1 mm apart from the tip of a bifurcated optical fibre with a cylindrical plastic support. This sensor could detect a wide range of K+ concentrations (10?6?1 M K+ for the DB18C6-based sensor, 10?8?10?2 M K+ for the valinomycin-based sensor) at Ph 7.0 by measuring the absorbance change at 513 nm. The factors that influence the response sensitivity of the sensor are discussed theoretically. 相似文献
532.
533.
Influence of specific gravity and food on movement of granules in the gastrointestinal tract of rats 总被引:1,自引:0,他引:1
M Mori Y Shirai Y Uezono T Takahashi Y Nakamura H Makita Y Nakanishi Y Imasato 《Chemical & pharmaceutical bulletin》1989,37(3):738-741
The suitability of rats as an animal model for estimating the bioavailability of controlled-release granules in humans was investigated. Non-disintegrating granules (diameter of 0.8 mm; specific gravity of 0.9-1.85) were used as a model preparation. Twenty granules were administered to fed rats, fasted rats and rats given soft food, and the number of granules remaining in the gastrointestinal tract was counted at suitable intervals. Granules with a specific gravity of 1.25 administered to fasted rats were rapidly emptied from the stomach with a 50% gastric emptying time of 1 h as compared with granules with a specific gravity of less than 1.0 or with a high specific gravity such as 1.85. The presence of food in the stomach reduced the emptying rate of granules. The mean transit time of granules through the small intestinal tract was not influenced by the specific gravity or the presence of food. The mean transit time was about 3 h. It was found that the transit profile of granules through the gastrointestinal tract in rats was similar to that of granules in humans. Accordingly, it is possible to use rats at the preformulation stage for estimating the bioavailability of controlled-release granules in humans. 相似文献
534.
The simultaneous determination of some heavy metals in their mixtures is described. The method is based on the differential reaction rate of ligand substitution reactions involving ethyleneglycol bis(2-aminoethylether)N,N,N',N'-tetraacetic acid (EGTA) and 4-(2-pyridylazo)-resorcinol (PAR). Various combinations at the 10-6M level of heavy metal ions such as manganese(II), iron(III), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), mercury(II) and lead(II) can be determined photometrically. 相似文献
535.
Kimura M Saito Y Ohta K Hanabusa K Shirai H Kobayashi N 《Journal of the American Chemical Society》2002,124(19):5274-5275
A second-generation 1,3,5-phenylene-based dendritic porphyrin decorated with flexible alkyl chains exhibited a liquid crystallinity, and the inclusion of fullerene within the nanospace of the dendritic porphyrin strongly affected the mesophase structure in the thermotropic liquid-crystalline phase. 相似文献
536.
[reaction: see text] A series of fullerene-terminated oligo(phenylene ethynylene)s (OPEs) (1a-d and 2) have been synthesized and further characterized by cyclic voltammetry (CV) and UV-vis spectroscopy. The key step in the syntheses is an effective one-pot reaction that allows the attachment of C(60) to multiple terminal alkynes. 相似文献
537.
S Fujita T Yoshida B. M Bhanage M Shirai M Arai 《Journal of molecular catalysis. A, Chemical》2002,180(1-2):277-284
Supported liquid phase catalysts (SLPC) were prepared using a porous silica, ethylene glycol, palladium acetate, and triphenylphosphine trisulfonate sodium salt (TPPTS). The SLPC samples prepared were used for Heck reaction of iodobenzene and butyl acrylate with triethylamine base in toluene and the influence of catalyst preparation conditions was examined. The rate of reaction depends on the concentration of palladium–TPPTS complexes in the dispersed phase of ethylene glycol but not on the quantity of the dispersed liquid used. The SLPC sample can be easily separated by simple filtration and it is recyclable; interestingly, the rate of reaction is promoted on the repeated runs, due to the formation and accumulation of Et3NHI adduct in the dispersed phase. 相似文献
538.
Kimura M Shiba T Yamazaki M Hanabusa K Shirai H Kobayashi N 《Journal of the American Chemical Society》2001,123(24):5636-5642
A series of 1,3,5-phenylene-based rigid dendritic porphyrins were synthesized by Suzuki coupling between a porphyrin core and dendron units. The intramolecular energy transfer was studied by absorption and fluorescence spectroscopies. The encapsulation of the porphyrin core within the 1,3,5-phenylene dendron units was found to provide highly efficient energy transfer from the dendron units to the porphyrin core. The dendritic wedge structure affected the energy transfer efficiency. The 1,3,5-phenylene-based rigid dendron units act as highly efficient light-harvesting antennae. These dendritic porphyrins have also been examined as C(60) hosts and substrate-selective oxidation catalysts. The attachment of the second generation of 1,3,5-phenylene-based dendron units with the porphyrin core enabled a stable inclusion of C(60) in toluene. Furthermore, the size and shape of the nanospace in the rigid dendritic porphyrins were found to affect the selectivity of substrates in the catalytic olefin oxidations. 相似文献
539.
Hiroaki Taira Hiromasa Nagase Tomohiro Endo Haruhisa Ueda 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):23-28
Large-ring cyclodextrins (LR-CDs) composed of more than 9 d-glucose units are not well studied. In this study, LR-CDs composed of 36, 37, 38 and 39 d-glucose units (CD36∼
∼CD39) were isolated and purified from a LR-CD mixture, and their physicochemical properties including aqueous solubility, surface tension, specific rotation and acid-catalyzed hydrolysis rate were elucidated. The aqueous solubilities of CD36∼
∼CD39 were greater than those of α-, β-, γ-CD, CD9, CD10, CD14 and CD26. CD36∼
∼CD39 did not show any surface activity. The acid-catalyzed hydrolysis of CD36∼
∼CD39 was a little faster than that of other LR-CDs (CD9∼
∼CD35). There was no marked difference in specific rotation or the acid-catalyzed hydrolysis rate among CD36∼
∼CD39. Furthermore, we compared these findings with the physicochemical properties of α-, β-, γ-CD and other LR-CDs (CD9∼
∼CD35). 相似文献
540.
8-METHOXYPSORALEN PLUS UVA INDUCES THE 72 kDa HEAT SHOCK PROTEIN IN ORGAN-CULTURED NORMAL HUMAN SKIN
T. Muramatsu Y. Yamashina H. Tada N. Kobayashi M. Yamaji H. Ohno T. Shirai A. Takahashi T. Ohnishi 《Photochemistry and photobiology》1993,58(6):809-812
Abstract The proteins induced by heat and other stressors, called heat shock proteins (HSP) or stress proteins, are considered to play a general role in protection from cellular injury. Exposure to UVA (320400 nm) following application of 8-methoxypsoralen (8-MOP), termed PUVA is commonly used in the field of dermatology. In order to understand the induction of HSP in PUVA-treated human skin, indirect immunofluorescence using a monoclonal antibody specific for the 72 kDa HSP (HSP 72) was carried out in organ-cultured normal human skin that was treated with PUVA. When the organ-cultured skin was treated at 37°C for 1 h with 8-MOP at a final concentration of 10 or 100 μg/mL and exposed to UVA (51.3 kJ/m2 ), nuclear immunofluorcscence of HSP 72 was detected in the epidermal cells 12 h after UVA irradiation. In contrast, the induction of HSP 72 was not detected either by UVA irradiation or 8-MOP treatment. These results suggest that PUVA treatment is one of the stressors for human skin, and DNA damage caused by PUVA induces HSP 72. 相似文献