全文获取类型
收费全文 | 658篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
化学 | 464篇 |
晶体学 | 3篇 |
力学 | 26篇 |
数学 | 43篇 |
物理学 | 144篇 |
出版年
2023年 | 7篇 |
2021年 | 3篇 |
2020年 | 15篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 8篇 |
2013年 | 25篇 |
2012年 | 30篇 |
2011年 | 38篇 |
2010年 | 21篇 |
2009年 | 13篇 |
2008年 | 35篇 |
2007年 | 33篇 |
2006年 | 33篇 |
2005年 | 37篇 |
2004年 | 20篇 |
2003年 | 24篇 |
2002年 | 19篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 3篇 |
1997年 | 3篇 |
1996年 | 15篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1975年 | 10篇 |
1974年 | 14篇 |
1973年 | 7篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1930年 | 2篇 |
排序方式: 共有680条查询结果,搜索用时 31 毫秒
101.
An enantioselective synthesis of the structure, 3, assigned to the alkaloid (+)-montabuphine has been achieved using the readily available metabolite 4 as starting material. A comparison of the physical and spectral data recorded on compound 3 with those reported for (+)-montabuphine suggests that they are different compounds. 相似文献
102.
103.
Caldwell LM Hill AF Wagler J Willis AC 《Dalton transactions (Cambridge, England : 2003)》2008,(27):3538-3541
The first examples of isoselenocarbonyl linked bimetallics arise from the chemoselective insertion of platinum(0) into the alkynyl-selenium bond of a molybdenum alkynylselenolatoalkyidyne complex. 相似文献
104.
105.
Dabb SL Messerle BA Otting G Wagler J Willis A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(32):10058-10065
The methylhydrazine complex [Ru(NH(2)NHMe)(PyP)(2)]Cl(BPh(4)) (PyP=1-[2-(diphenylphosphino)ethyl]pyrazole) was synthesised by addition of methylhydrazine to the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(BPh(4))(2). The methylhydrazine ligand of the ruthenium complex has two different binding modes: side-on (eta(2)-) when the complex is in the solid state and end-on (eta(1)-) when the complex is in solution. The solid-state structure of [Ru(PyP)(2)(NH(2)NHMe)]Cl(BPh(4)) was determined by X-ray crystallography. 2D NMR spectroscopic experiments with (15)N at natural abundance confirmed that in solution the methylhydrazine is bound to the metal centre by only the -NH(2) group and the ruthenium complex retains an octahedral conformation. Hydrazine complexes [RuCl(PyP)(2)(eta(1)-NH(2)NRR')]OSO(2)CF(3) (in which R=H, R'=Ph, R=R'=Me and NRR'=NC(5)H(10)) were formed in situ by the addition of phenylhydrazine, 1,1-dimethylhydrazine and N-aminopiperidine, respectively, to a solution of the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(OSO(2)CF(3))(2) in dichloromethane. These substituted hydrazine complexes of ruthenium were shown to exist in an equilibrium mixture with the bimetallic starting material. 相似文献
106.
A C2 hexadentate diester derived from (5-hydroxymethyl)pyridine-2-aldehyde 2'-pyridylhydrazone (5-HOCH2PAPHY) and an enantiomerically pure (aS)-spirane dicarboxylic acid diastereoselectively reacts with iron(II) benzenesulfonate in methanol to furnish a 20% diastereomeric excess (de) of a two-bladed propeller, octahedral iron complex in which the P configuration of the newly created (+/-)-[Fe(PAPHY)2](2+) stereocenter predominates; when the reaction mixture is heated under reflux for 12 h, however, the excess of the diastereomer having the P configuration at iron increases to 80%, as determined by (1)H NMR spectroscopy. The configuration at iron in the major diastereomer of the complex was determined by comparison of the circular dichroism spectrum of the deprotonated complex with that of a related complex of known configuration. Repositioning of the hydroxymethyl group of the pyridine-2-aldehyde from the 5- to the 6-position produced a C2-spirane ligand that generates a double-stranded diiron(II) helicate in >99% de. Single crystal X-ray structure determinations of the racemates of the protonated and deprotonated helicates revealed that the complexes crystallize diastereoselectively, that is, two ligand strands of a S configuration generate two octahedral iron(II) stereocenters of P configuration to give a dinuclear metal helicate of P configuration and vice versa for the ligand of a R configuration. 相似文献
107.
Dr. Nicholas J. Green Dr. Anthony C. Willis Prof. Dr. Michael S. Sherburn 《Angewandte Chemie (International ed. in English)》2016,55(32):9244-9248
[Pd(PPh3)4] catalyzes a Suzuki–Miyaura‐like twofold cross‐coupling sequence between underivatized propargylic diols and either aryl or alkenyl boronic acids to furnish highly substituted 1,3‐dienes. Thus, 2,3‐diaryl‐1,3‐butadienes and their dialkenic congeners ([4]dendralenes) are delivered in a (pseudo)halogen‐free, single‐step synthesis which supersedes existing methods. Allenols are also readily formed. Treatment of these single‐ and twofold cross‐coupled products with acid leads to remarkably short syntheses of highly‐substituted benzofulvenes and aryl indenes, respectively. 相似文献
108.
Heterologous Production of Fungal Maleidrides Reveals the Cryptic Cyclization Involved in their Biosynthesis
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Katherine Williams Agnieszka J. Szwalbe Dr. Nicholas P. Mulholland Dr. Jason L. Vincent Dr. Andrew M. Bailey Prof. Christine L. Willis Prof. Thomas J. Simpson Prof. Russell J. Cox 《Angewandte Chemie (International ed. in English)》2016,55(23):6784-6788
Fungal maleidrides are an important family of bioactive secondary metabolites that consist of 7, 8, or 9‐membered carbocycles with one or two fused maleic anhydride moieties. The biosynthesis of byssochlamic acid (a nonadride) and agnestadride A (a heptadride) was investigated through gene disruption and heterologous expression experiments. The results reveal that the precursors for cyclization are formed by an iterative highly reducing fungal polyketide synthase supported by a hydrolase, together with two citrate‐processing enzymes. The enigmatic ring formation is catalyzed by two proteins with homology to ketosteroid isomerases, and assisted by two proteins with homology to phosphatidylethanolamine‐binding proteins. 相似文献
109.
110.
A catalyst generated from Pd(OAc)2 and dppp is effective for the direct intramolecular arylation of alkenyl triflates. Conjugated alkene-arene-containing carbocycles are produced in good yield. The process tolerates a variety of aryl substituents as well a simple heteroaryl groups. Electron-deficient aryl rings deliver faster reactions. 相似文献