全文获取类型
收费全文 | 275篇 |
免费 | 3篇 |
专业分类
化学 | 146篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 28篇 |
物理学 | 101篇 |
出版年
2019年 | 4篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 9篇 |
2013年 | 14篇 |
2012年 | 8篇 |
2011年 | 3篇 |
2010年 | 9篇 |
2009年 | 4篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 15篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有278条查询结果,搜索用时 140 毫秒
1.
Takanari Yasui Takeshi Ohtsuka Tetsu Suzuki Shigeki Okajima Kazuya Nakayama Mitsuru Tomioka Katsuhiro Kamimura Takeo Namekata Hiroaki Minamide Hiromasa Ito 《International Journal of Infrared and Millimeter Waves》2006,27(2):199-210
A new, wide-band, high-speed and high-sensitivity THz detector has been developed. The prototype detector consists of a parabolic
cylindrical mirror, a long wire antenna and a Schottky barrier diode. Direct detection measurements have shown a stable sensitivity
of 150 ± 50 V/W for 1–2 THz without any adjustments. The long wire antenna was fixed at the focus of parabolic cylindrical
mirror then it has been realized less operation steps, easy coupling to the external THz signals and a dramatic enhancement
in the practicality of this system. The optically polished mirror and frosted surface one showed comparable sensitivities,
thus easy polishing and less cost mirror fabrication can be applied for this system. The radiation pattern showed a maximum
radiation angle of approximately 23° with its dominant main lobe, which was attributed to the wire antenna character and confirmed
good agreements with classical antenna theory. 相似文献
2.
3.
H. Kawaguchi S. Kataiwa T. Mita Y. Ohtsuka T. Takeuchi S. Kobayashi 《Colloid and polymer science》1990,268(12):1167-1173
Dichlorophene was used as a model drug. Drug-carrying latex particles were prepared by soap-free emulsion copolymerization of dichlorophene acrylate with some hydrophilic methacrylate comonomers. The comonomers used affected not only the structure and colloidal stability of particles, but also the drug-activity of particles. Preliminary study of the drug activity revealed that highly hydrophilic latex particles were very stable and too inactive to be engulfed by amoebae and kill them. On the contrary, less hydrophilic particles carrying a large amount of drug can be an effective device to release drugs at a moderate rate to fight against extracelluar targets such as parasites. 相似文献
4.
5.
K Take K Okumura K Takimoto M Ohtsuka Y Shiokawa 《Chemical & pharmaceutical bulletin》1992,40(4):899-906
A series of 1,1'-biphenyl-2,6-dicarboxylic acid diesters with an aminoalkyl group in the ester function were synthesized and examined for their inhibitory activity on detrusor contraction in vitro and in vivo. In the in vivo test, arrhythmia was observed as a side effect. Among those compounds synthesized, 2-methyl 6-[4-(1-methylpiperidinyl)] 3-hydroxy-5-methyl-2'-nitro-1,1'-biphenyl-2,6-dicarboxylate (18) showed strong inhibitory activity on detrusor contractions in vivo (ED50 = 0.54 mg/kg i.v., ED50 = 7.2mg/kg i.d.) and good separation from the side effect. Compound 18 was chosen for further pharmacological evaluation as an agent for the treatment of overactive detrusor. 相似文献
6.
This paper reports the synthesis of several 11,14-dimethoxydeoxypodocarpic acid derivatives from (+)-podocarpic acid. The synthesis of the naturally occurring sesquiterpene, (+)-winterin, from Drimys winteri illustrates a synthetic application of the 11,14-dimethoxy intermediates and establishes the absolute configuration for winterin. 相似文献
7.
N Saito H Kawaguchi Y Ohtsuka N Shimizu S Inayama 《Chemical & pharmaceutical bulletin》1991,39(11):3085-3087
Hansenula anomala, which catalyzes an asymmetric reduction, was immobilized in bulk or spherical crosslinked polymers. The catalytic activity of the yeast for enantio-selective reduction of 3,8-dioxo-4-methoxycarbonyl-9-methyl-delta 4(10)-octalin (lab) was severely affected by the immobilization conditions, such as the crosslink density, and by hydrophobicity of polymers and other components used for immobilization, oxygen concentration in the medium, etc. In some immobilized systems, the ratio of resulting enantiomers was inverted from that in a free yeast system. 相似文献
8.
Fumiko Ohtsuka 《Geometriae Dedicata》1991,38(2):151-157
The theory of the ideal boundary has arisen as a method of a study of noncompact manifolds. In this paper we shall investigate properties of manifolds whose ideal boundaries satisfy some conditions related to the Tits metric. In Section 2 we shall consider in what conditions the Tits topology is equivalent to the sphere topology and in Section 3 the property of points at infinity which characterize the R-factor. Furthermore, in Section 4 we shall give a sufficient condition for a projective map to be isometríc.Partially supported by Grant-in-Aid for Encouragement of Young Scientists (No. 01740011), The Ministry of Education, Science and Culture, Japan. 相似文献
9.
A tritriacontanucleotide which has the sequence of the 5half molecule of E.coli glycine tRNA2, was synthesized by the phosphotriester method involving p-anisidate protection for the 3phosphate ends. Di- and trinucleotide units were prepared from 5dimethoxytrityl-2O-tetrahydrofuranyl-3?-O-(o-chlorophenyl)phosphoryl derivatives of uridine, N-benzoylcytidine, N-benzolyadenosine and N-iso-butyrylguanosine by condensation with 35unprotected nucleosides followed by phosphorylation to give 3phosphodiester blocks. The 3terminal dimers and trimers were synthesized by using 3(o- chlorophenyl)phosphoro-p-anisidates instead of 3?,5?-unprotected nucleosides. The 3?-phosphodiesters of oligonucleotides with a chain length of larger than 5 were obtained by removal of the 3?-phosphoro-p-anisidate with isoamyl nitrite. The 5dimethoxytrityl group was removed by treatment with zinc bromide under anhydrous conditions. Fragments were designed to use common dimer blocks and to reduce the step for 5deblocking of larger fragments. Finally a 3phosphodiester block with a chain length of 20 was condensed with a 5OH component (tridecanucleotide). The fully protected 33 mer was deblocked and purified by chromatography. The structural integrity of the product was confirmed by mobility shift analysis and complete digestion with RNase T2. 相似文献
10.
Abstract Ribozymes that distinguish a single base change in RNA were synthesized and used to specifically cleave c-Ha-ras messenger RNA. Using phosphorothioate containing oligonucleotide substrates, we have shown that Mg2+ binds to the pro-R oxygen of the phosphate and that the RNA cleavage reaction occurs via an in-line mechanism. Oligoribonucleotides containing a modified nucleoside are described. 相似文献