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51.
Picolinamides as Effective Ligands for Copper‐Catalysed Aryl Ether Formation: Structure–Activity Relationships,Substrate Scope and Mechanistic Investigations 下载免费PDF全文
Carlo Sambiagio Dr. Rachel H. Munday Prof. Stephen P. Marsden Prof. A. John Blacker Dr. Patrick C. McGowan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17606-17615
The use of picolinic acid amide derivatives as an effective family of bidentate ligands for copper‐catalysed aryl ether synthesis is reported. A fluorine‐substituted ligand gave good results in the synthesis of a wide range of aryl ethers. Even bulky phenols, known to be very challenging substrates, were shown to react with aryl iodides with excellent yields using these ligands. At the end of the reaction, the first examples of end‐of‐life Cu species were isolated and identified as CuII complexes with several of the anionic ligands tested. A preliminary mechanistic investigation is reported that suggests that the substituents on the ligands might have a crucial role in determining the redox properties of the metal centre and, consequently, its efficacy in the coupling process. An understanding of these effects is important for the development of new efficient and tunable ligands for copper‐based chemistry. 相似文献
52.
53.
Lauren M. Gehman Kalyan V. Vasudevan Rachel R. Butorac Salem S. Al-Deyab Alan H. Cowley 《Journal of chemical crystallography》2011,41(7):998-1001
Abstract
The coordination of decamethyleuropocene to a “clamshell” 1,2-bis(imino)acenaphthene (BIAN) ligand is accompanied by a one-electron redox process. The crystal structure of the Eu3+ product has been determined. The complex crystallizes in the triclinic space group P-1, with a = 12.065(2), b = 15.391(3), c = 17.266(4) ?, α = 73.71, β = 73.93(3), γ = 81.40(3)°, V = 2948.3(10) ?3 and Z = 2. The pyridine moiety of the clamshell ligand is not coordinated to the Eu3+ center. 相似文献54.
55.
This paper presents a new method for studying the surface of a heterogeneous solid by inverse gas chromatography at infinite dilution (IGC-ID). After saturating the high-energy sites by impregnation with a suitable polymer, the chromatographic probes visit the low energy sites, which are not visible by conventional IGC-ID. This method has been used to study the two types of surface of talc: lateral and basal surfaces. In the second part of the paper the influence of the structure of the polymer on the impregnation is examined. In particular it is shown that a polymer with a linear structure is more able to fit a rough surface than is a branched or a cyclic polymer. 相似文献
56.
Woerdeman DL Parnas RS Giunta RK Wilkerson AL 《Journal of colloid and interface science》2002,249(1):246-252
We employ a direct method, time-of-flight secondary ion mass spectroscopy (ToF-SIMS), to determine experimentally the chemical compositions of the wetted and dewetted regions of an uncured epoxy thin film. Determining the composition of the dewetted region indicated the presence of a very thin sublayer of resin in what was thought to be a region devoid of resin. The capability of ToF-SIMS to probe small 65 x 65 microm(2) areas of the surface has permitted us to directly compare the SIMS spectra of the wetted and dewetted regions to the survey spectra of the reactants. This may indicate the strength of resin/silica interactions, which determine interface formation and properties. 相似文献
57.
A series of derivatisation reactions between p-t-butyl calix[4]arene and ethyl bromoacetate were carried out in order to prepare 1,3 diester substituted calix[4]arene. Mass spectral data, obtained from direct injection of samples, indicated that the reactions were rich in the desired product. Since the ultra violet (UV) spectra of the desired product and possible impurities are very similar, liquid chromatography (LC) chromatographic data seemed to corroborate these results. However, when on-line LC-UV-MS was carried out and each LC peak subjected to MS analysis as it eluted, a very different picture emerged. It was found that many of these reactions actually contained high levels of the monoester product which, having less affinity for sodium in the MS, is therefore seriously underestimated in any direct injection assay. LC-diode array detection (DAD) methods were also used to help successfully identify and characterise the compounds being formed in these complex reactions. The overall results obtained in this paper allowed the optimal reaction conditions to be determined for this reaction. LC-MS analysis of the chromatographic peaks also identified the presence of two isomers of the diester substituted calix[4]arene (1,3 and 1,2 diesters). The combination of LC and UV/MS detection is required for accurate analysis of the products of such reactions. 相似文献
58.
59.
Andrianasolo EH Gross H Goeger D Musafija-Girt M McPhail K Leal RM Mooberry SL Gerwick WH 《Organic letters》2005,7(7):1375-1378
[structure: see text] Chemical investigation of two field collections of marine cyanobacteria has led to the discovery of two new cytotoxic natural products, ankaraholides A (2) and B (3), along with the known compound swinholide A (1). Since swinholide-type compounds were previously localized to the heterotrophic bacteria of sponges, these findings raise intriguing questions about their true metabolic source. 相似文献
60.
When a nonvolatile liquid film dewets from a partly compatible liquid substrate, the advancing dewetting front leaves behind droplets formed through a Rayleigh instability mechanism at its rim. We have found that these droplets continue to move in the direction of the dewetting front for extended periods (of order one day) with an initial droplet velocity varying linearly with the droplet size, and a displacement varying logarithmically with time. We attribute this persistent motion to a transient surface tension gradient on the substrate liquid surface trailing the dewetting front. 相似文献