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61.
1-Deoxy-D-xylulose-5-phosphate (DXP) is a key intermediate in the non-mevalonate pathway to terpenoids in bacteria, and it is the substrate for the enzyme 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXP-R). In order to study the mechanism of DXP-R, we required a flexible synthesis of the substrate which would allow the incorporation of isotopic labels, and the variation of the two stereocentres. Thus 1,4-dihydroxypent-2-yne was selectively reduced to give the E-olefin, and selective phosphorylation of the primary alcohol followed by oxidation of the secondary alcohol gave a substrate suitable for dihydroxylation. Dihydroxylation using stoichiometric OsO4 in the presence of chiral ligands gave protected DXP in high ee. Final hydrogenolysis gave DXP in quantitative yield and high purity. DXP-R was produced by rapid cloning of the dxr gene from Escherichia coli through controlled expression and ion exchange chromatography. The synthetic DXP was fully active in enzyme assays catalysed by recombinant DXP-R. 相似文献
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Lin JF Militzer B Struzhkin VV Gregoryanz E Hemley RJ Mao HK 《The Journal of chemical physics》2004,121(17):8423-8427
The melting curve of H(2)O has been measured by in situ Raman spectroscopy in an externally heated diamond anvil cell up to 22 GPa and 900 K. The Raman-active OH-stretching bands and the translational modes of H(2)O as well as optical observations are used to directly and reliably detect melting in ice VII. The observed melting temperatures are higher than previously reported x-ray measurements and significantly lower than recent laser-heating determinations. However, our results are in accord with earlier optical determinations. The frequencies and intensities of the OH-stretching peaks change significantly across the melting line while the translational mode disappears altogether in the liquid phase. The observed OH-stretching bands of liquid water at high pressure are very similar to those obtained in shock-wave Raman measurements. 相似文献
63.
Singh SB Zink DL Heimbach B Genilloud O Teran A Silverman KC Lingham RB Felock P Hazuda DJ 《Organic letters》2002,4(7):1123-1126
[structure: see text] HIV-1 integrase is a critical enzyme for viral replication, and its inhibition is an emerging target for potential antiviral chemotherapy. We have discovered a novel inhibitor, integramycin, from screening of fermentation extracts using an in vitro assay. Integramycin possesses a hexacyclic ring system and exhibited an IC50 value of 4 microM against HIV-1 integrase (strand transfer). The isolation, structure elucidation, stereochemistry, conformation, and biological activity has been described. 相似文献
64.
Eric J. Carpenter Shaurya Seth Noel Yue Russell Greiner Ratmir Derda 《Chemical science》2022,13(22):6669
Advances in diagnostics, therapeutics, vaccines, transfusion, and organ transplantation build on a fundamental understanding of glycan–protein interactions. To aid this, we developed GlyNet, a model that accurately predicts interactions (relative binding strengths) between mammalian glycans and 352 glycan-binding proteins, many at multiple concentrations. For each glycan input, our model produces 1257 outputs, each representing the relative interaction strength between the input glycan and a particular protein sample. GlyNet learns these continuous values using relative fluorescence units (RFUs) measured on 599 glycans in the Consortium for Functional Glycomics glycan arrays and extrapolates these to RFUs from additional, untested glycans. GlyNet''s output of continuous values provides more detailed results than the standard binary classification models. After incorporating a simple threshold to transform such continuous outputs the resulting GlyNet classifier outperforms those standard classifiers. GlyNet is the first multi-output regression model for predicting protein–glycan interactions and serves as an important benchmark, facilitating development of quantitative computational glycobiology.GlyNet, a neural net model of glycan-protein binding strengths. Given a glycan it outputs binding to each of several protein samples. Reproducing glycan array data, it extrapolates the binding of untested glycans against the protein samples. 相似文献
65.
硅基材料是新一代高容量锂离子蓄电池负极材料的典型代表,近年来已成为理论研究和应用研究的热点.本文介绍了锂离子电池硅基负极材料的制备方法、电化学性能及其研究现状,分析了硅材料作为锂离子电池负极材料存在的问题;讨论了硅材料作为锂离子电池负极材料的研究前景.并指出若能克服目前存在问题,将有望成为新一代锂离子电池负极材料. 相似文献
66.
Lijun Zhang Xun Hu Chengzhong Yu Russell Crawford 《International journal of environmental analytical chemistry》2013,93(12):1274-1285
A new solid phase extractant, sinapinaldehyde (SA) modified SBA-15 mesoporous silica, was developed for selective extraction and preconcentration of trace Pb(II) from aqueous solutions. The successful immobilization of SA on SBA-15 and the strong interaction between SA-SBA-15 and Pb(II) were characterized and confirmed by FTIR spectroscopy and scanning electron microscopy. Parameters such as solution pH, shaking time, eluent condition and sample volume were optimized so that the maximum removal of Pb(II) from solution could be achieved. At pH 4.0, the maximum adsorption capacity of the sorbent for Pb(II) was found to be 33.6?mg?g?1 and the adsorbed Pb(II) could be completely eluted using a mixed solution of 2?M HCl and 5% CS(NH2)2. Some common metal ions such as K(I), Na(I), Mg(II), Ca(II), Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) did not interfere with the adsorption of trace Pb(II). The detection limit of the present method was found to be 1.3?ng?mL?1 and the relative standard deviation was less than 2.0% (n?=?8). These results suggested that this new sorbent is very efficient and selective for the removal of trace Pb(II) in water samples. 相似文献
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70.
Johannes Barth Michael Buback Christopher Barner‐Kowollik Thomas Junkers Gregory T. Russell 《Journal of polymer science. Part A, Polymer chemistry》2012,50(22):4740-4748
The termination of model mid‐chain radicals (MCRs), which mimic radicals that occur in acrylate polymerization over a broad range of reaction conditions, has been studied by single‐pulse pulsed laser polymerization (SP‐PLP) in conjunction with electron paramagnetic resonance spectroscopy. The model radicals were generated by initiator‐fragment addition to acrylic macromonomers that were preformed prior to the kinetic experiments, thus enabling separation of termination from the propagation reaction, for these model radicals propagate sparingly, if at all, on the timescale of SP‐PLP experiments. Termination rate coefficients of the MCRs were determined in the temperature range of 0–60°C in acetonitrile and butyl propionate solution as well as in bulk macromonomer over the range of 0–100 °C. Termination rate coefficients slightly below those of the corresponding secondary radicals were deduced, demonstrating the relatively high termination activity of this species, even when undergoing MCR–MCR termination. For chain length of 10, a reduction by a factor of 6 is observed. Unusually high activation energies were found for the termination rate coefficient in these systems, with 35 kJ mol?1 being determined for bulk macromonomer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献