全文获取类型
收费全文 | 161篇 |
免费 | 5篇 |
专业分类
化学 | 100篇 |
晶体学 | 1篇 |
数学 | 36篇 |
物理学 | 29篇 |
出版年
2023年 | 5篇 |
2022年 | 2篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 5篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 4篇 |
2009年 | 1篇 |
2008年 | 11篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有166条查询结果,搜索用时 187 毫秒
131.
Stephen Hyde Dr. Janis Veliks Dr. Benoît Liégault Dr. David Grassi Dr. Marc Taillefer Prof. Véronique Gouverneur 《Angewandte Chemie (International ed. in English)》2016,55(11):3785-3789
Copper‐catalyzed Si?H, B?H, P?H, S?H, and N?H insertion reactions of 2,2,2‐trifluoro‐1‐diazoethane and 1‐aryl 2,2,2‐trifluorodiazoethanes generated a large number of new fluorine‐containing chemical entities for medicinal chemists. With selected Si?H and B?H insertion reactions, we demonstrate successful extension to asymmetric catalysis. 相似文献
132.
Nagarajan Ramkumar Larisa Baumane Dzintars Zacs Janis Veliks 《Angewandte Chemie (International ed. in English)》2023,62(12):e202219027
A simple process for the oxy-monofluoromethylation of alkenes is described. In combination with visible-light copper(I) photoredox catalysis, an easily accessible iodine(III) reagent containing monofluoroacetoxy ligands serves as a powerful source of a monofluoromethyl (CH2F) radical, enabling the step economical synthesis of γ-fluoro-acetates from a broad range of olefinic substrates under mild conditions. Applications to late-stage diversification of alkenes derived from complex molecules, amino acids and the synthesis of fluoromethylated heterocycles are also demonstrated. 相似文献
133.
Dunfeng Gao Ilya Sinev Fabian Scholten Rosa M. Arn‐Ais Nuria J. Divins Kristina Kvashnina Janis Timoshenko Beatriz Roldan Cuenya 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(47):17203-17209
Production of multicarbon products (C2+) from CO2 electroreduction reaction (CO2RR) is highly desirable for storing renewable energy and reducing carbon emission. The electrochemical synthesis of CO2RR catalysts that are highly selective for C2+ products via electrolyte‐driven nanostructuring is presented. Nanostructured Cu catalysts synthesized in the presence of specific anions selectively convert CO2 into ethylene and multicarbon alcohols in aqueous 0.1 m KHCO3 solution, with the iodine‐modified catalyst displaying the highest Faradaic efficiency of 80 % and a partial geometric current density of ca. 31.2 mA cm?2 for C2+ products at ?0.9 V vs. RHE. Operando X‐ray absorption spectroscopy and quasi in situ X‐ray photoelectron spectroscopy measurements revealed that the high C2+ selectivity of these nanostructured Cu catalysts can be attributed to the highly roughened surface morphology induced by the synthesis, presence of subsurface oxygen and Cu+ species, and the adsorbed halides. 相似文献
134.
Luana Mifsud Buhagiar Carmel Sammut Yana Chircop Kersty Axisa Nicolette Sammut Bartolo Janis Vella Szijj Anthony Serracino Inglott Godfrey LaFerla 《Biomedical chromatography : BMC》2019,33(12)
Amitriptyline (AMI) has been in use for decades in treating depression and more recently for the management of neuropathic pain. A highly sensitive and specific LC–tandem mass spectrometry method was developed for simultaneous determination of AMI, its active metabolite nortriptyline (NOR) and their hydroxy‐metabolites in human serum, using deuterated AMI and NOR as internal standards. The isobaric E‐10‐hydroxyamitriptyline (E‐OH AMI), Z‐10‐hydroxyamitriptyline (Z‐OH AMI), E‐10‐hydroxynortriptyline (E‐OH NOR) and Z‐10‐hydroxynortriptyline (Z‐OH NOR), together with their parent compounds, were separated on an ACE C18 column using a simple protein precipitation method, followed by dilution and analysis using positive electrospray ionisation with multiple reaction monitoring. The total run time was 6 min with elution of E‐OH AMI, E‐OH NOR, Z‐OH AMI, Z‐OH NOR, AMI (+ deuterated AMI) and NOR (+ deuterated NOR) at 1.21, 1.28, 1.66, 1.71, 2.50 and 2.59 min, respectively. The method was validated in human serum with a lower limit of quantitation of 0.5 ng/mL for all analytes. A linear response function was established for the range of concentrations 0.5–400 ng/mL (r2 > .999). The practical assay was applied on samples from patients on AMI, genotyped for CYP2C19 and CYP2D6, to understand the influence of metaboliser status and concomitant medication on therapeutic drug monitoring. 相似文献
135.
Dr. Janis Veliks Armands Kazia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3786-3789
Diarylfluoromethyl sulfonium salts are efficient fluoromethylene transfer reagents equivalent to fluorocarbene, which is difficult to access. This was demonstrated by the development of a monofluorinated Johnson–Corey–Chaykovsky reaction with ketones and aldehydes, delivering uncommon 2-unsubstituted fluoroepoxides. This is the first evidence for the feasibility of sulfur fluoromethylylide and its action as a reaction intermediate. 相似文献
136.
Volynets N. I. Poddubskaya O. G. Demidenko M. I. Lyubimov A. G. Kuzhir P. P. Suslyaev V. I. Pletnev M. A. Zicans Janis 《Russian Physics Journal》2017,60(4):717-722
Russian Physics Journal - Mechanical and thermogravimetric properties of polymer composite materials with various concentrations of multiwalled carbon nanotubes effectively shielding radiation in... 相似文献
137.
Results of an experimental investigation into the changes of viscosity and the flow character of binary blends of high-density
polyethylene with an elastomer (ethylene-propylene-dicyclopentadiene terpolymer) during the γ-radiation and chemical cross-linking
are reported. The type of functions of the effective viscosity of temperature (activation energy of flow) and shear rate (flow-behavior
index) in relation to the structure of melts of the blends is discussed for a wide range of component ratios and various extents
of cross-linking.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 819–830, November–December, 2005. 相似文献
138.
The results of experimental and theoretical investigation of thermal deformation (expansion or contraction) of poly(vinyl chloride) (PVC) and chlorinated polyethylene (CPE) blends are presented. Eight types of specimens with PVC/CPE weight ratios of 100/0, 90/10, 80/20, 60/40, 40/60, 20/80, 10/90, and 0/100 were tested. The experimental curves of thermal deformation in the longitudinal direction of the specimens are presented. The primary attention is paid to the mathematical prediction of the effective coefficients of thermal expansion for the blends based on the composition and properties of the components. The blends are regarded as heterogeneous two-phase systems where the inversion changes of morphology occur gradually over a rather wide range of intermediate compositions. It is found that the thermal expansion coefficients of PVC/CPE blends can be predicted, with an adequate accuracy over the whole range of blend compositions, by the Levin and Budiansky equations for a two-component medium with randomly arranged component particles. 相似文献
139.
The nickel-catalyzed cycloaddition of unsaturated hydrocarbons and carbonyls is reported. Diynes and enynes were used as coupling partners. Carbonyl substrates include both aldehdyes and ketones. Reactions of diynes and aldehydes afforded the [3,3] electrocyclic ring-opened tautomers, rather than pyrans, in high yields. The cycloaddition reaction of enynes and aldehydes afforded two distinct products. A new carbon-carbon bond is formed, prior to a competitive beta-hydrogen elimination of a nickel alkoxide, between the carbonyl carbon and either one of the carbons of the olefin or the alkyne. The steric hindrance of the enyne greatly affected the chemoselectivity of the cycloaddition of enynes and aldehydes. In some cases, dihydropyran was also formed. The scope of the cycloaddition reaction was expanded to include the coupling of enynes and ketones. No beta-hydrogen elimination was observed in cycloaddition reaction of enynes and ketones. Instead, C-O bond-forming reductive elimination occurred exclusively to afford dihydropyrans in excellent yields. In all cases, complete chemoselectivity was observed; only dihydropyrans where the carbonyl carbon forms a carbon-carbon bond with a carbon of the olefin, rather than of the alkyne, were observed. All cycloaddition reactions occur at room temperature and employ nickel catalysts bearing the hindered 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) or its saturated analogue, 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazolin-2-ylidene (SIPr). 相似文献
140.
The combination of Ni(0) and an N-heterocyclic carbene acts as a precatalyst for the cycloisomerization of enynes to afford 1,3-dienes. During the course of the reaction, a nickel hydride is formed from oxidative addition of the ortho C-H on the carbene ligand. Deuterium labeling studies are presented. 相似文献