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排序方式: 共有87条查询结果,搜索用时 46 毫秒
1.
2.
A tunable microwave-assisted protocol for the synthesis of two biologically relevant families of heterocycles has been designed. Via a simple switch of reaction conditions, the same starting materials can be engaged in either an improved synthesis of the dihydrotriazine scaffold or a novel, first-in-class MCR to render the challenging 5-aminoimidazole nucleus in a single step. An additional first-in-class MCR is also reported utilizing guanidines to afford 2,5-aminoimidazoles. 相似文献
3.
This report discloses a novel concise synthesis of a series of 3-hydroxypyrazoles 5 via a tandem Ugi/debenzylation /hydrazine-mediated cyclization sequence. Herein, n-butyl isocyanide 4b was utilized as an alternative to classical convertible isocyanides enabling high yielding hydrazine-mediated cyclization. Taken together, a novel class of 3-hydroxypyrazoles 5a-5i was synthesized with potential to be of interest in future library enrichment strategies. 相似文献
4.
Anti-resonant reflecting optical waveguides (ARROW) are described which trap light in a low index layer between a lower, high-index confining layer and an upper total internal reflection boundary. In this configuration, most of the light (greater than 80%) travels in the low index porous polymer layer, the refractive index of which is monitored by examining the angle at which light is coupled out of the waveguide. It is shown that asymmetric ARROW sensors can be constructed using conventional chemical vapour deposition and spin-coating techniques and their sensitivity is as predicted by theoretical modelling. 相似文献
5.
Bienayme H Hulme C Oddon G Schmitt P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(18):3321-3329
With the emergence of high-throughput screening in the pharmaceutical industry in the early 1990's, organic chemists were faced with a new challenge: how to prepare large collections of molecules (the libraries) to "feed" the high-throughput screen? The unique exploratory power of some reactions (such as the 40 year-old Ugi four-component condensation) was soon recognized to be extremely valuable to produce libraries in a time- and cost-effective manner. Over the last five years, industrial and academic researchers have made these powerful transformations into one of the most efficient and cost-effective tools for combinatorial and parallel synthesis. 相似文献
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The following article describes a concise synthesis of a collection of 4,5-dihydro-1H-benzo[e][1,4]diazepines fused to a hydantoin ring. Molecular complexity and biological relevance are high and structures are generated in a mere three steps, employing the Ugi reaction to assemble diversity reagents. The protocol represents a novel UDC (Ugi-deprotect-cyclize) strategy employed in the Ugi-5-component CO2-mediated condensation, followed by further cyclization under basic conditions, to afford the fused hydantoin. Mechanistic caveats, dependent on the aldehydes of choice will be revealed and a facile oxidation of the final products to imidazolidenetriones is briefly discussed. 相似文献
8.
K. F. Hulme 《Optics & Laser Technology》1982,14(4):213-215
Factors affecting the design of compact heterodyne- and direct-detection systems are contrasted. Recent UK achievements are placed in context: a TEA laser direct-detection rangefinder and a chirp-pulse-comparison rangefinder-velocimeter are described. 相似文献
9.
Thomas Tennant Matthew C. Hulme Thomas B.R. Robertson Oliver B. Sutcliffe Ryan E. Mewis 《Magnetic resonance in chemistry : MRC》2020,58(12):1151-1159
Piperazine-based drugs, such as N-benzylpiperazine (BZP), became attractive in the 2000s due to possessing effects similar to amphetamines. Herein, BZP, in addition to its pyridyl analogues, 2-, 3-, and 4-pyridylmethylpiperidine (2-PMP, 3-PMP, and 4-PMP respectively) was subjected to the hyperpolarisation technique Signal Amplification By Reversible Exchange (SABRE) in order to demonstrate the use of this technique to detect these piperazine-based drugs. Although BZP was not hyperpolarised via SABRE, 2-PMP, 3-PMP, and 4-PMP were, with the ortho- and meta-pyridyl protons of 4-PMP showing the largest enhancement of 313-fold and 267-fold, respectively, in a 1.4-T detection field, following polarisation transfer at Earth's magnetic field. In addition to the freebase, 4-PMP.3HCl was also appraised by SABRE and was found not to polarise, however, the addition of increasing equivalents of triethylamine (TEA) produced the freebase, with a maximum enhancement observed upon the addition of 3 equivalents of TEA. Further addition of TEA led to a reduction in the observed enhancement. SABRE was also employed to polarise 4-PMP.3HCl (~20% w/w) in a simulated tablet to demonstrate the forensic application of the technique (138-fold enhancement for the ortho-pyridyl protons). The amount of 4-PMP.3HCl present in the simulated tablet was quantified via NMR using D2O as a solvent and compared well to complimentary gas chromatography–mass spectrometry data. Exchanging D2O for CD3OD as the solvent utilised for analysis resulted in a significantly lower amount of 4-PMP.3HCl being determined, thus highlighting safeguarding issues linked to drug abuse in relation to determining the amount of active pharmaceutical ingredient present. 相似文献
10.
Ricardo A. Luna-Mora Ángeles Torres-Reyes Oscar A. González-Cruz Fernando Ortega-Jiménez Hulme Ríos-Guerra Jessica V. González-Carrillo 《Green Chemistry Letters and Reviews》2018,11(4):371-378
The efficiency of conventional heating energy source compared with Infrared (IR), Ultrasound (US), Microwave and the simultaneous combination US–IR eco-friendly approaches for preparation of new N-(5-R1 -amino-2-nitrophenyl)acetamides and 5-R1-amino-2-nitroaniline by Nucleophilic Aromatic Substitution (SNAr) via addition–elimination reactions on the halogens F, Cl, Br, I, employing amines as nucleophiles were explored. Moreover, phenyldiazenyl derivatives in good yields by an oxidative one-pot SNAr-based amination reaction from an unusual oxidation of 2-phenylhydrazinyl derivatives in DMSO was prepared. 相似文献