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91.
采用镀膜/循环伏安法制备了PbO2修饰玻碳电极.在Pb(NO3)2溶液中,在-0.7 V 将Pb膜沉积在玻碳电极表面,然后在5 mol/L NaOH溶液中以100 mV/s速度在-1.0~1.0 V循环伏安扫描20次,PbO2膜均匀沉积在玻碳电极表面.采用交流阻抗法监控电极修饰每一过程,环境扫描电镜表征电极表面形貌.探讨了PbO2膜的沉积机理及其电化学行为,表面活性位点覆盖量为7.5×10-10 mol/cm2.PbO2修饰电极对H2O2电氧化表现出较高催化活性,起始氧化电位低至0.1 V,考察了影响催化活性的因素.计时电流法测定H2O2 (工作电位0.40 V),响应时间小于2 s; 线性范围为5.0 ×10-6 ~ 5.5×10-4 mol/L;检出限1.1×10-6 mol/L (信噪比为3).在实际水样中H2O2测定结果满意.电极在室温环境下储存30 d,其催化活性基本不变.该修饰电极制备工艺简单、重现性良好、稳定性高. 相似文献
92.
The effect of photodynamic therapy (PDT) on oesophageal motility and acid clearance in patients with Barrett's oesophagus 总被引:1,自引:0,他引:1
Globe J Smythe A Kelty CJ Reed MW Brown NJ Ackroyd R 《Journal of photochemistry and photobiology. B, Biology》2006,85(1):17-22
BACKGROUND: Barrett's oesophagus is the major risk factor for oesophageal adenocarcinoma. It is proposed that long-term re-epithelialisation, which has been achieved following ablation using 5-aminolaevulinic acid (5-ALA) photodynamic therapy (PDT) may reduce the risk of malignant change. However, it is not known whether PDT modifies oesophageal motility. AIM: To assess oesophageal pH and motility before and after PDT ablation in treated and untreated areas of the oesophagus. METHODS: Twelve patients (10 male) with Barrett's oesophagus, median segment length 4 cm, were treated with PDT ablation. Twenty-four hours pH assessment and oesophageal manometry were performed before and 4-6 weeks after ablation. PDT was carried out using 635 nm red light, 4-6h after administration of 30 mg/kg 5-ALA. Proximal (untreated) and distal (treated) oesophageal resting pressure, wave amplitude, percentage peristalsis and percentage study time oesophageal pH<4, were assessed. Proton pump inhibitors (PPI) were administered throughout the study. RESULTS: There were no significant differences in oesophageal motility in treated or untreated areas of the oesophagus after PDT compared to pre-treatment values. Patients who continued to experience oesophageal acid exposure required more treatments to achieve complete Barrett's ablation. CONCLUSIONS: Oesophageal motility following ALA-PDT suggests a trend toward enhanced wave propagation however continued oesophageal acid exposure may affect PDT efficacy. 相似文献
93.
Darwen PJ Tran TT Bourne GT Nielson JL Smythe ML 《Combinatorial chemistry & high throughput screening》2006,9(7):559-563
Combinatorial chemistry has become an invaluable tool in medicinal chemistry for the identification of new drug leads. For example, libraries of predetermined sequences and head-to-tail cyclized peptides are routinely synthesized in our laboratory using the IRORI approach. Such libraries are used as molecular toolkits that enable the development of pharmacophores that define activity and specificity at receptor targets. These libraries can be quite large and difficult to handle, due to physical and chemical constraints imposed by their size. Therefore, smaller sub-libraries are often targeted for synthesis. The number of coupling reactions required can be greatly reduced if the peptides having common amino acids are grouped into the same sub-library (batching). This paper describes a schedule optimizer to minimize the number of coupling reactions by rotating and aligning sequences while simultaneously batching. The gradient descent method thereby reduces the number of coupling reactions required for synthesizing cyclic peptide libraries. We show that the algorithm results in a 75% reduction in the number of coupling reactions for a typical cyclic peptide library. 相似文献
94.
Green [HIPTN3N]V(THF) ([HIPTN3N]3- = [(HIPTNCH2CH2)3N]3-, where HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3) can be prepared in a 70-80% yield via the addition of H3[HIPTN3N] to VCl3(THF)3 in THF, followed by the addition of LiN(SiMe3)2. From [HIPTN3N]V(THF), the following have been prepared: {[HIPTN3N]VN2}K, [HIPTN3N]V(NH3), [HIPTN3N]V=NH, [HIPTN3N]V=NSiMe3, [HIPTN3N]V=O, [HIPTN3N]V=S, and [HIPTN3N]V(CO). No ammonia is formed from dinitrogen using {[HIPTN3N]VN2}K, [HIPTN3N]V=NH, or [HIPTN3N]V(NH3) as the initial species under conditions that were successful in the analogous [HIPTN3N]Mo system. X-ray structural studies are reported for [HIPTN3N]V(THF) and [HIPTN3N]V(NH3). 相似文献
95.
Hom-李代数是一类满足反对称和Hom-Jacobi等式的非结合代数.扭Heisenberg-Virasoro代数是次数不超过1的微分算子代数的中心扩张,它是一类重要的无限维李代数,与一些曲线的模空间有关.文章主要研究扭Heisenberg-Virasoro代数上Hom-李代数结构,确定了扭Heisenberg-Virasoro代数上存在非平凡的Hom-李代数结构. 相似文献
96.
97.
Miranda LP Meutermans WD Smythe ML Alewood PF 《The Journal of organic chemistry》2000,65(18):5460-5468
Overcoming the phenomenon known as "difficult" synthetic sequences has been a major goal in solid-phase peptide synthesis for over 30 years. In this work the advantages of amide backbone-substitution in the solid-phase synthesis of "difficult" peptides are augmented by developing an activated N(alpha)()-acyl transfer auxiliary. Apart from disrupting troublesome intermolecular hydrogen-bonding networks, the primary function of the activated N(alpha)()-auxiliary was to facilitate clean and efficient acyl capture of large or beta-branched amino acids and improve acyl transfer yields to the secondary N(alpha)()-amine. We found o-hydroxyl-substituted nitrobenzyl (Hnb) groups were suitable N(alpha)()-auxiliaries for this purpose. The relative acyl transfer efficiency of the Hnb auxiliary was superior to the 2-hydroxy-4-methoxybenzyl (Hmb) auxiliary with protected amino acids of varying size. Significantly, this difference in efficiency was more pronounced between more sterically demanding amino acids. The Hnb auxiliary is readily incorporated at the N(alpha)()-amine during SPPS by reductive alkylation of its corresponding benzaldehyde derivative and conveniently removed by mild photolysis at 366 nm. The usefulness of the Hnb auxiliary for the improvement of coupling efficiencies in the chain-assembly of difficult peptides was demonstrated by the efficient Hnb-assisted Fmoc solid-phase synthesis of a known hindered difficult peptide sequence, STAT-91. This work suggests the Hnb auxiliary will significantly enhance our ability to synthesize difficult polypeptides and increases the applicability of amide-backbone substitution. 相似文献
98.
A pulse-polarography method is described for the determination of traces of platinum in ores after fire-assay separation and preconcentration. The silver bead from the fire assay is dissolved and treated with ammonia and ethylenediamine to produce a sensitive catalytic polarographic wave. Measurement of the wave by differential pulse polarography allows determination of Pt with a detection limit of 0.0025 ppm. Platinum in ore samples was determined in the range 0.1-0.9 ppm and a correlation coefficient of 0.98 was obtained on comparison with AAS results. 相似文献
99.
Horton DA Severinsen R Kofod-Hansen M Bourne GT Smythe ML 《Journal of combinatorial chemistry》2005,7(3):421-435
Peptidyl privileged structures have been widely used by many groups to discover biologically active molecules. In this context, privileged substructures are used as "hydrophobic anchors", to which peptide functionality is appended to gain specificity. Utilization of this concept has led to the discovery of many different active compounds at a wide range of biological receptors. A synthetic approach to these compounds has been developed on a "safety-catch" linker that allows rapid preparation of large libraries of these molecules. Importantly, amide bond formation/cleavage through treatment with amines is the final step; it is a linker strategy that allows significant diversification to be easily incorporated, and it only requires the inclusion of an amide bond. In addition, chemistry has been developed that permits the urea moiety to be inserted at the N-terminus of the peptide, allowing the same set of amines (either privileged substructures or amino acid analogues) to be used at both the N- and C-termini of the molecule. To show the robustness of this approach, a small library of peptidyl privileged structures were synthesized, illustrating that large combinatorial libraries can be synthesized using these technologies. 相似文献
100.
A variety of complexes Cu(NS2)(Im)(NO3)2 and Cu(NS2)(Py)(NO3)2 where NS2=HN(CH2CH2SR)2(R=CH3CH2CH2, (CH3)2CH,CH3CH2CH2CH2 and (CH3)2CHCH2), have been synthesized and characterized by elementary analyses, molar conductivity, IR, UV/Vis and ESR spectra as well as by electrochemical methods. The new complexes exhibit exceptionally high redox potentials(500~580 mV) and complexes for HN(CH2CH2SCH(CH3)2)2 exihibit rather hyperfine splitting constants(a‖<70G) in the powder ESR spectra, which are close to those for the blue copper proteins. 相似文献