全文获取类型
收费全文 | 1556篇 |
免费 | 38篇 |
国内免费 | 10篇 |
专业分类
化学 | 1133篇 |
晶体学 | 39篇 |
力学 | 30篇 |
数学 | 124篇 |
物理学 | 278篇 |
出版年
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 15篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 26篇 |
2015年 | 20篇 |
2014年 | 37篇 |
2013年 | 90篇 |
2012年 | 74篇 |
2011年 | 79篇 |
2010年 | 46篇 |
2009年 | 62篇 |
2008年 | 93篇 |
2007年 | 90篇 |
2006年 | 97篇 |
2005年 | 95篇 |
2004年 | 91篇 |
2003年 | 65篇 |
2002年 | 75篇 |
2001年 | 22篇 |
2000年 | 34篇 |
1999年 | 26篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 25篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 17篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 21篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 17篇 |
1972年 | 5篇 |
1968年 | 7篇 |
排序方式: 共有1604条查询结果,搜索用时 31 毫秒
41.
Tetsuji Kametani Shiroshi Shibuya Hideo Sugi Keiichiro Fukumoto 《Journal of heterocyclic chemistry》1973,10(4):451-453
The absolute configuraiton at the C1-position of 1,2,3,4-tetrahydro-1-phenylisoquinolines can be deduced from the CD curves of either the free base or its methiodide. Furthermore, the absolute con figuration of (+)-2-amino-1-(3-hydroxyphenyl)ethanol (V) was revised and found to have R-configuration at the C1 -position. 相似文献
42.
Water-swellable polyelectrolyte microgels polymerized in an inverse microemulsion using a nonionic surfactant 总被引:5,自引:0,他引:5
A series of poly(dimethylacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid) microgels slightly crosslinked by methylene-bis-acrylamide (MBA) were polymerized in a novel inverse microemulsion polymerization (IMEP) system. To determine a suitable composition of the IMEP system, the phase diagram of a pseudoternary system was made. The pseudoternary polymerization system consisted of n-hexane, a nonionic surfactant (polyoxyethylene oleyl ether, C18En), and an aqueous monomer solution. Polymerization was performed in a single-phase reversed micelle solution. The reversed micelles were about 50 nm in diameter, as determined by FF-TEM. The viscometric characteristics of the polymers extracted from the IMEP system were studied in 3 mM sodium chloride aqueous solution. The intrinsic viscosity values for the noncrosslinked and crosslinked (0.1 mol% MBA was incorporated) samples were 25 and 7.4 dl/g, respectively. The overlap concentration (c*) of crosslinked polymer microgel occurred at c[eta] = 1 in the solvent. When the volume fraction (phi) of the microgel was 0.7, the value of the apparent yield stress of the microgel solution was observed. These results show that the microgel has a significant thickening effect above c* due to friction between the microgel particles. It is assumed that the microgels polymerized in a confined space retain the shape or size of the nanosized reactor with a diameter on the order of 50 nm. 相似文献
43.
New ring-opening reaction of thiazoline-azetidinones 1 to dithioazetidinones 2 was achieved with 2-benzothiazolyl disulfide in aqueous acidic media and its potentiality for the preparation of a variety of cephalosporins 3 from various thiazoline-azetidinones 1 is demonstrated. 相似文献
44.
A fundamental study about the selective foam separation of protein mixture was carried out. A solution containing two proteins, ovalbumin (OA) and lysozyme (LZ), and an anionic surfactant, sodium dodecyl sulfate (SDS), was adjusted to pH 6.0, which referred to an intermediate state between the isoelectric points of the proteins. The solution was processed by continuous foam separation. The results showed that a proper addition of SDS greatly improved the selective recovery of LZ to OA. The experimental data were well explained by a simple model that most of cationic protein molecules (LZ) are associated with SDS and the adsorption of all the species including LZ-SDS complexes are subjected to Langmuir adsorption isotherm. The results also showed that one of the Langmuir parameters, which means a kind of lyophillic property of adsorbed material, of LZ-SDS complexes was extremely large as compared with that of primary protein. 相似文献
45.
Tanaka H Yamada T Sugiyama S Shiratori H Hino R 《Journal of colloid and interface science》2005,286(2):812-815
Using a hydroxyl group appended free base porphyrin derivative (HP), porphyrin-introduced silica gels were synthesized by a sol-gel process. The HP content in the materials linearly increased with increasing the HP concentration. Meanwhile, free base tetraphenylporphyrin (TPP) with no hydroxyl groups were almost not incorporated into the silica gels. These facts suggested that the interaction between hydroxyl groups of the HP molecules and silica network is considerably strong. The UV-vis characters of HP-introduced materials were almost the same as pure HP molecules. The Beer's plot indicated that the HP molecules in the materials are dispersed. 相似文献
46.
Smectic layer structure of ferroelectric liquid crystal formed between fine polymer fibres 总被引:1,自引:0,他引:1
Hideo Fujikake Takashi Toyooka Takeshi Murashige Hiroto Sato Yoshiki Iino Masahiro Kawakita Hiroshi Kikuchi 《Liquid crystals》2002,29(7):881-887
This paper describes the alignment of ferroelectric liquid crystal (FLC) structures formed between aligned polymer fibres, where the FLC smectic layers are determined by polarising microscopy and X-ray diffraction. The FLC/polymer composite films were formed from a nematic phase FLC/monomer solution using a photopolymerisation-induced phase separation method. It was found that bending of the FLC smectic layers was induced in both the film plane and the cross-sectional plane at the phase transition from smectic A to chiral smectic C of the FLC material. The light transmittance properties of the composite film between crossed polarizers was analysed by light propagation simulation in several optical anisotropic media, based on the evaluated smectic layer model. 相似文献
47.
Hideo Kurosawa 《Journal of organometallic chemistry》2004,689(24):4511-4520
This review summarizes the author’s contributions to the field of chemistry of group 10 metal complexes containing unsaturated hydrocarbon ligands, with a brief introduction showing how his research subject has shifted from mononuclear type to multinuclear type complexes. New structure and reactivity trends in the multipalladium complexes with bridging allyl and allenyl/propargyl ligands, as well as bridging conjugated polyene molecules are discussed in terms of some unique bonding features of these complexes. 相似文献
48.
The oxygen ions of the β-VOPO4 catalyst were exchanged with an
tracer by a reduction–oxidation method and by a catalytic oxidation of but-1-ene using
2. The bands at 992 and 900 cm−1 were more shifted to lower frequencies than those at 1076 and 1002 cm−1. Applying the correlation between the Raman bands and stretching vibrations in the literature, the exchanged oxygen species were estimated. The results suggest that the P–O–V vacancies corresponding to 992 and 900 cm−1 were responsible for reoxidation and the V=O oxygen corresponding to the 1002 cm−1 band of β-VOPO4 was not. The (VO)2P2O7 was oxidized to β-VOPO4 by O2 above 823 K. The insertion position of oxygen was determined at the bands at 992 and 900 cm−1 of β-VOPO4 using
2, which is the same as the exchanged position. 相似文献
49.
Liao Shijie Ying Weiyong Fang Dingye Kameyama Hideo 《Reaction Kinetics and Catalysis Letters》2005,85(1):205-213
Summary Catalytic combustion of toluene, propylene and CO over Pt/Al2O3 /Al catalyst was investigated. Strong inhibition effects are observed when the mixture of toluene, propylene and CO is oxidized. A reaction mechanism of catalytic combustion over Pt/Al2O/Al is proposed. The results from kinetic models are in good agreement with the experimental data. 相似文献
50.
Masahiro Manabe Toshihiro Ochi Hideo Kawamura Hajime Katsu-ura Masaki Shiomi Mandeep Singh Bakshi 《Colloid and polymer science》2005,283(7):738-746
The partial molar volumes (Va) of 1-alkanols (carbon number, m=5, 6, 7) in - and -cyclodextrin (CD) solutions at 5.00 mmol kg–1 have been determined as a function of alkanol concentration (Ca) between 293.2 and 308.2 K by using a dilatometer. It has been observed that with an increase in Ca, Va increased in -CD solution but decreased in -CD solution, asymptotically to a value of Va in CD-free water. The dependence of Va on Ca provided the binding constant (K) of 1:1 complex, the volume change in complex formation, and the partial molar volume of complex itself. The complex formation mechanism has been discussed on the basis of these values and their carbon number dependences in the respect of geometric behavior, hydrophobic interaction, and van der Waals interaction. It is concluded that the CD cavity in water is not rigid but flexible for fitting in nicely with guest molecule. 相似文献