全文获取类型
收费全文 | 1294篇 |
免费 | 35篇 |
国内免费 | 11篇 |
专业分类
化学 | 790篇 |
晶体学 | 49篇 |
力学 | 18篇 |
数学 | 71篇 |
物理学 | 412篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 17篇 |
2017年 | 10篇 |
2016年 | 21篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 66篇 |
2012年 | 44篇 |
2011年 | 63篇 |
2010年 | 37篇 |
2009年 | 52篇 |
2008年 | 58篇 |
2007年 | 90篇 |
2006年 | 61篇 |
2005年 | 46篇 |
2004年 | 70篇 |
2003年 | 50篇 |
2002年 | 38篇 |
2001年 | 54篇 |
2000年 | 35篇 |
1999年 | 34篇 |
1998年 | 18篇 |
1997年 | 15篇 |
1996年 | 18篇 |
1995年 | 22篇 |
1994年 | 21篇 |
1993年 | 37篇 |
1992年 | 30篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 14篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1973年 | 9篇 |
1972年 | 8篇 |
排序方式: 共有1340条查询结果,搜索用时 15 毫秒
61.
62.
Qingbin Xue Tatsumi Kimura Takashi Fukuda Satoru Shimada Hiro Matsuda Corresponding author 《Liquid crystals》2013,40(2):137-143
Chiral helical polymers have been expected to exhibit optical activity with a significantly large optical rotation power. In this paper polymethylphenylethylcarbodiimides (Poly-PhEMCDI) with helical structure were synthesized by the insertion polymerization of a corresponding chiral monomeric carbodiimide initiated by a copper complex. The circular dichroism spectra and optical rotation power induced by the ordered rigid main chain helical structure of polycarbodiimides, in solution and as cast films, were studied. Polycarbodiimides have a rigid rod helical structure and form lyotropic liquid crystal (LLC) in organic solvents such as dichloromethane (DCM), chloroform and THF. The LLC phase was studied using polarizing optical microscopy and X-ray diffraction. A chiral nematic phase was formed in DCM and chloroform in the concentration range 20–36%. Spherulites were formed in more concentrated solution. The formation of a LLC phase in polycarbodiimides organic solutions makes it possible to align the polymer helical chain to form an ordered film for electro-optical applications. 相似文献
63.
64.
Y Takeuchi H Yasukawa Y Yamaoka Y Morimoto S Nakao Y Fukumori T Fukuda 《Chemical & pharmaceutical bulletin》1992,40(2):484-487
Whole skin lipid bio-liposomes (skin bio-liposomes), in size ranging from 2 to 8 microns, were prepared by a reverse phase evaporation technique using rat full thickness skin. Leakage of an encapsulated fluorescence probe, ANTS (delta-amino-1,3,6-naphthalene-trisulfonate), was measured by adding transdermal penetration enhancers (penetrants) into the medium where the skin bio-liposomes were present. Oleylamine induced a fast release of ANTS from the liposomes compared to lauryl-amine which showed a weak action. With these penetrants, the degree of ANTS release from the prepared bio-liposomes was found to correlate well with the results of frequency changes in the CH-asymmetric stretching band near 2920 cm-1 in the rat stratum corneum. The penetrant which caused relatively strong leakage of ANTS induced the significantly large shift of the peak toward the higher wave-numbers due to the perturbation in the structure of lipids of the stratum corneum. The skin bio-liposomes prepared from the rat full thickness skin could be useful in evaluating the penetrants. 相似文献
65.
T Kawakita T Kuroita M Yasumoto M Sano K Inaba T Fukuda T Tahara 《Chemical & pharmaceutical bulletin》1992,40(3):624-630
A series of 3,4-dihydro-3-oxo-1,4-benzoxazine-8-carboxamide derivatives was synthesized and evaluated for serotonin-3 (5-HT3) receptor antagonistic activity assessed by their ability to antagonize the von Bezold-Jarish (BJ) effect in rats. Derivatives bearing 1-azabicyclo[2.2.2]oct-3-yl moiety as a basic function attached to the carboxamide at position 8 showed more potent antagonistic activity than those bearing the other three basic moieties. Structure-activity relationships of this series showed that methyl and chloro groups were more effective as substituents at positions 4 and 6, respectively. The representative compound 15 (Y-25130) in this series showed potent antagonistic activity on the BJ effect (ED50 = 1.3 micrograms/kg i.v.), high affinity for 5-HT3 receptor (Ki = 2.9 nM) and complete protection against cisplatin-induced emesis in dogs at a dose of 0.1 mg/kg i.v. 相似文献
66.
Four possible diastereomers of pentenocin B were synthesized in a stereocontrolled manner, and the first total synthesis of a natural enantiomer of (+)-pentenocin B unequivocally established the absolute stereochemistry to be 4S,5R,6R. 相似文献
67.
The delta form of crystalline syndiotactic polystyrene is a clathrate molecular compound in which various aromatic molecules are encaged. We have investigated the size, shape, and connectivity of the molecular cavity in the crystal using a molecular dynamics simulation. The effects of the guest species on the cavity structure were investigated in detail. In order to systematically vary the guest structure, various aromatic guests, e.g., benzene, toluene, p-xylene, m-xylene, o and mesitylene were examined. The interstitial spaces between the guests and the polymer chains were analyzed by cluster analysis of the free volumes. The individual cavity volumes into which the guests are clathrated were also evaluated. It was found that the guest molecules can greatly affect not only the cavity size and shape but also the connectivity of the cavities. The transport of small molecules in the crystal is discussed in connection with the cavity structure. 相似文献
68.
Kyoungmoo Koh Kohji Ohno Yoshinobu Tsujii Takeshi Fukuda 《European Polymer Journal》2004,40(12):2665-2670
Copper-mediated atom transfer radical polymerization (ATRP) of a protected silanol group-holding methacrylate, methacryloxypropyltrimethoxysilane (MOPS), was investigated. In a dry condition using carefully distilled solvent and monomer, the polymerization proceeded in a living fashion providing a low-polydispersity polymer with a predicted molecular weight. The ATRP in conjunction with the sequential monomer addition of methyl methacrylate (MMA) and MOPS afforded a block copolymer of the type PMMA-b-poly(MMA-r-MOPS). The heat treatment of a solution of the block copolymer in the presence of a catalytic amount of ammonia gave a polymeric core-shell nanoparticle with a shell of PMMA moieties and a core of the poly(MMA-r-MOPS) blocks cross-linked via the condensation of the trimethoxysilane groups of the MOPS moieties. 相似文献
69.
Ruslim C Hashimoto M Matsunaga D Tamaki T Ichimura K 《Langmuir : the ACS journal of surfaces and colloids》2004,20(1):95-100
The inherent chromonic lyotropic liquid crystalline properties of a dye have been manipulated to fabricate multi-axial micropolarizing thin films by means of the photoalignment technique. The dye aqueous solution is deposited on a photopatterned polymer film to result in the macroscopic alignment of the dye molecules, followed by drying at ambient temperature. The solid polarizing dye layers thus produced exhibit very a high contrast ratio and degree of polarization in the region of visible light. Addition of a small amount of surfactant to the dye solution is a prerequisite for the generation of a nematic chromonic phase and for the formation of homogeneous thin dye layers on the polymer film. The correlation between the optical and surface morphological properties of the dye layers is discussed. 相似文献
70.
Miyagawa T Nagai K Yamada A Sugihara Y Fukuda T Fukuda T Uchida R Tomoda H Omura S Nagamitsu T 《Organic letters》2011,13(5):1158-1161
The first total synthesis of citridone A has been achieved through regioselective intramolecular iodocyclization and regio- and stereoselective Pd(0)-catalyzed coupling as key reactions. 相似文献