全文获取类型
收费全文 | 201篇 |
免费 | 2篇 |
专业分类
化学 | 167篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 32篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2018年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 8篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 13篇 |
2007年 | 11篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 3篇 |
1999年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1962年 | 2篇 |
1959年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有203条查询结果,搜索用时 0 毫秒
1.
Tetsuji Kametani Hideo Lida Shinzo Kano Sadao Tanaka Keiichiro Fukumoto Shiroshi Shibuya Haruhiko Yagi 《Journal of heterocyclic chemistry》1967,4(1):85-92
Schotten-Baumann reaction of the amine (X) with 4-benzyloxy-3,4′-oxydiphenylacetyl chloride (XI) gave two amides, (XIIa) and (XIIb), which were cyclized to give the corresponding 3,4-dihydroisoquinolines, respectively. Methylation of the above 3,4-dihydro-isoquinolines, followed by hydrolysis, afforded the compounds having the same composition as berbamine (Ia) and oxyacanthine (Ib), whose structures are under examination. 相似文献
2.
Ihara M Katsumata A Setsu F Tokunaga Y Fukumoto K 《The Journal of organic chemistry》1996,61(2):677-684
[Ni(cyclam)](ClO(4))(2)-catalyzed indirect electroreduction of olefinic bromides produced six-membered compounds in low to high yields. The synthetic intermediate 49 of Ipecac and Corynanthe alkaloids was obtained in 88% yield in a highly stereoselective manner. Lactam 66, the synthetic precursor of tacamonine, was prepared in 49% yield as a mixture of two diastereoisomers. The electrolysis of the bromoacetates gave the debrominated compounds in good yields. 相似文献
3.
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
4.
Some molecules with a molecular skeleton similar to that of stilbenes and azobenzenes show orientational disorder in the crystals. If the disorder is dynamic, a conformational interconversion takes place through a pedal motion. In this study X-ray diffraction analyses of (E)-stilbene (1) and azobenzene (2) were carried out at various temperatures. We succeeded in observing thermodynamic nonequilibrium states that were generated by fast freezing of the conformational interconversion at low temperatures. The populations of the two conformers in crystals of 1 at 90 K varied with the cooling rate. Flash cooling of a crystal of 2 from room temperature to 90 K made it possible to observe the minor unstable conformer that does not exist in the equilibrium state at the same temperature. 相似文献
5.
6.
A stereoselectivity in an intramolecular cycloaddition of the olefinic -quinodimethanes 13 and 23 generated from the thermolysis of optically active 4β-[2-(4-methoxybenzocyclobutenyl)ethyl] -5α-methoxymethyl-3-phenyl-thio-methylenefuran-2-ones 12 and 22, respectively, is studied and a stereoselective synthesis of (+)--4,5-( 4-methoxybenzo) -1β,7aβ-(2α-methoxymethyl-5-oxofuro)hydrindane 1 is also described. 相似文献
7.
Keiichiro Fukumoto Masatoshi Chihiro Yuichi Shiratori Masataka Ihara Tetsuji Kametani Toshio Honda 《Tetrahedron letters》1982,23(29):2973-2976
Thermolysis of a benzocyclobutene derivative () prepared from norcamphor produced stereoselectively a tetracyclic compound (), which was converted to a lactone () having correct stereochemistry at C7, C8, C9, C11, C13, and C14 positions of (±)-klaineanone. 相似文献
8.
Nobukatsu Nemoto Keiichiro Kakimoto Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2002,40(11):1698-1705
This work deals with the cationic ring‐opening polymerization of cyclic thiocarbonates with a norbornene or norbornane moiety, that is, 5,5‐(bicyclo[2.2.1]hept‐2‐ene‐5,5‐ylidene)‐1,3‐dioxane‐2‐thione ( TC1 ) or 5,5‐(bicyclo[2.2.1]heptane‐5,5‐ylidene)‐1,3‐dioxane‐2‐thione ( TC2 ), respectively. The reaction of TC1 initiated by trifluoromethanesulfonic acid (TfOH), methyl trifluoromethanesulfonate (TfOMe), boron trifluoride etherate (BF3OEt2), or triethyloxonium tetrafluoroborate (Et3OBF4) afforded unidentified products; however, TC1 underwent cationic ring‐opening polymerization with methyl iodide as an initiator to afford polythiocarbonate because the propagating end was stabilized by the covalent‐bonding property. The polymerization of TC2 initiated by TfOH, TfOMe, BF3OEt2, or Et3OBF4 afforded polythiocarbonate with good solubility in common organic solvents and a narrow molecular weight distribution because of the absence of a double‐bond moiety. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1698–1705, 2002 相似文献
9.
Ono K Yoshida A Saito N Fujishima T Honzawa S Suhara Y Kishimoto S Sugiura T Waku K Takayama H Kittaka A 《The Journal of organic chemistry》2003,68(19):7407-7415
Six novel 2-substituted analogues of 1alpha,25-dihydroxy-19-norvitamin D(3), 6a,b-8a,b, were efficiently synthesized utilizing (-)-quinic acid as the A-ring precursor. The C2-modified A-rings were prepared as 4-alkylated (3R,5R)-3,5-dihydroxycyclohexanones 12-15 from (-)-quinic acid based on radical allylation at the C4 position of methyl (-)-quinicate. The new type of the CD-ring coupling partner 23 was synthesized from 25-hydroxy Grundmann's ketone 19 to apply to the modified Julia olefination to construct a diene unit between the A-ring and the CD-ring. The coupling yields, including a deprotection step, were 47-62%. After the separation of the diastereomers based on C2 stereochemistry, the structure (2alpha or 2beta) was determined by (1)H NMR experiments and compared to DeLuca's 2-methyl- and 2-ethyl-1alpha,25-dihydroxy-19-norvitamin D(3). Thus, the synthesized 2alpha-(3-hydroxypropyl)-1alpha,25-dihydroxy-19-norvitamin D(3) (8a) showed almost the same potency in binding to the bovine thymus vitamin D receptor (VDR) as the natural hormone 1, while its beta-isomer 8b had only a 3% affinity. Both 2alpha-allyl- and 2alpha-propyl-1alpha,25-dihydroxy-19-norvitamin D(3) (6a and 7a) and their 2beta-analogues (6b and 7b) possessed a weak affinity for the VDR. The strong VDR ligand 8a was ca. 36-fold more potent in induction of HL-60 cell differentiation than 1, and interestingly, even the weaker ligand 8b showed a 6.7-fold higher potency in the cell differentiation activity than that of 1. 相似文献
10.