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101.
A new silica-supported zinc-copper matrix reagent promotes the conjugate addition of alkyl iodides to cyclic and acyclic alkenenitriles in water. X-ray diffraction and electron microscopy techniques suggest that the active copper species generated from elemental zinc and copper(I) iodide is finely dispersed, zerovalent copper. Alkyl iodides react with the silica-supported reagent to generate putative radicaloid intermediates that efficiently add to alkenenitriles to provide beta-substituted nitriles. Conjugate additions to acyclic and cyclic 5-7-membered alkenenitriles are most effective for primary alkyliodides, although secondary and tertiary alkyliodides are viable reaction partners. The strategy addresses the challenge of performing conjugate additions to disubstituted alkenenitriles and demonstrates the beneficial role of the silica-supported reagent. 相似文献
102.
A versatile strategy involving a sequential intermolecular enyne metathesis of C-alkynyl glycosides with ethylene, Diels-Alder, and aromatization reactions is successfully developed to provide a range of C-aryl glycosides. [reaction: see text] 相似文献
103.
104.
Ayyagari V. Subrahmanyam Dr. Kalanidhi Palanichamy Krishna P. Kaliappan Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(28):8545-8556
An efficient approach for the synthesis of a variety of C‐aryl and spiro‐C‐aryl glycosides is described. This diversity‐oriented strategy employed here relies on a sequential enyne metathesis to generate the 1,3‐diene moiety and Diels–Alder reaction with different dienophiles followed by aromatisation. Whereas cross‐enyne metathesis with ethylene gas is used to install the 1,3‐diene moiety at the anomeric centre for the synthesis of C‐aryl glycosides, an intramolecular enyne metathesis on the sugar enyne is performed to generate the 1,3‐diene moiety for the synthesis of spiro‐C‐aryl glycosides. Efforts to extend this strategy to the synthesis of the core structure of natural C‐aryl glycoside gilvocarcin are also described. A combination of both C‐aryl and spiro‐C‐aryl glycosides in the same moiety to combine the features thereof has also been accomplished. A tandem enyne metathesis/Diels–Alder reaction/aromatisation has also been attempted to directly access the C‐aryl glycosides in one pot albeit in low yield. 相似文献
105.
Basavaraju Srinivas Kannekanti Lalitha Police Anil Kumar Reddy Gajeelli Rajesh Valluri Durga Kumari Machiraju Subrahmanyam Bhudev Ranjan De 《Research on Chemical Intermediates》2011,37(8):1069-1086
Abstract
The liquid-phase selective dehydrogenation of cyclohexanol has been investigated using two classes of catalyst containing either Cu2O or CuO on TiO2 under solar light in deaerated conditions at room temperature using acetonitrile medium in a batch reactor. The effect on dehydrogenation of three conditions, cyclohexanol concentration, copper loading on TiO2, and amount of catalyst, were investigated. The maximum yield of cyclohexanone obtained was 40%. The catalysts were characterized by XRD, UV–DRS, TEM, SEM–EDAX, and XPS. It was found that 1% (w/w) Cu2O/TiO2 was 100% selective for photocatalytic dehydrogenation of cyclohexanol. 相似文献106.
Two different strategies leading to formal total syntheses of platencin are described. The first strategy involving Claisen rearrangement and radical cyclization provides a rapid access to the core structure of platencin, and also use minimum protective-group operations. The second strategy, a protecting group-free route, utilizes a 6-exo-trig radical cyclization and aldol condensation as key steps leading to the formal synthesis of platencin. 相似文献
107.
Given two irreducible representations μ, v of the symmetric group S
d
, the Kronecker problem is to find an explicit rule, giving the multiplicity of an irreducible representation, λ, of S
d
, in the tensor product of μ and v. We propose a geometric approach to investigate this problem. We demonstrate its effectiveness by obtaining explicit formulas
for the tensor product multiplicities, when the irreducible representations are parameterized by partitions with at most two
rows. 相似文献
108.
Devulapalli Venu Gopal Basavaraju Srinivas Mangalampalli Venkata Phanikrishna Sharma Lipsa Panda Pullur Anil Kumar Machiraju Subrahmanyam Valluri Durga Kumari 《Reaction Kinetics and Catalysis Letters》2004,83(1):63-70
The vapor phase hydrogenation of acetophenone at atmospheric pressure is carried out for the synthesis of 1-phenylethanol
in a fixed bed reactor using Cu-Zn-Al-O (LTS-1) and LTS-2, Zn-Cr-Al-O (HTS-1) and Zn-Cu-Cr-Al-O (HTS-2) metal oxide catalysts.
Our studies clearly indicate that a catalyst of low temperature hydrogenation activity, when modified for its acidity with
magnesium oxide, shows maximum selectivity of 1-phenylethanol.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
109.
Sequential addition of i-PrMgCl and BuLi to sp3 hybridized iodoalcohols triggers a facile iodine-metal exchange. Intercepting the resulting cyclic Grignard reagents with a slight excess of an electrophile leads to a diverse range of substituted alcohols. The iodine-magnesium exchange strategy is effective with 3-carbon iodoalcohols bearing alkyl substitutents on the carbinol or adjacent carbons and with the chain-extended homolog 4-iodobutan-1-ol. 相似文献
110.