全文获取类型
收费全文 | 248篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
化学 | 176篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 30篇 |
物理学 | 50篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 21篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 19篇 |
2011年 | 18篇 |
2010年 | 11篇 |
2009年 | 17篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有263条查询结果,搜索用时 15 毫秒
201.
The microbial transformation of (+)-adrenosterone (1) by Cephalosporium aphidicola afforded three metabolites identified as androsta-1,4-diene-3,11,17-trione (2), 17beta-hydroxyandrost-4-ene-3,11-dione (3) and 17beta-hydroxyandrosta-1,4-diene-3,11-dione (4). The fermentation of 1 with Fusarium lini also produced metabolites 2 and 4, while the fermentation with Trichothecium roseum afforded metabolite 3. The structures of transformed products were determined by spectroscopic methods. 相似文献
202.
Manganese Oxide Nanoparticles/Reduced Graphene Oxide as Novel Electrochemical Platform for Immobilization of FAD and its Application as Highly Sensitive Persulfate Sensor 下载免费PDF全文
In this study, manganese oxide nanoparticles/reduced graphene oxide(MnOxNPs/rGO) was used as support for strong immobilization of flavin adenine dinucleotide(FAD). A thin film of rGO cast on the electrode surface, followed by performing electrodeposition of MnOxNPs at applied constant potential of +1.4 V vs. Ag/AgCl for 200 s. Finally, FAD was electrodeposited onto the rGO/MnOxNPs film by potential cycling between 1.0 to ?1.0 V in solution containing 1 mg ml?1 FAD. Electrochemical properties and catalytic activity of GCE/rGO‐MnOxNPs/FAD toward persulfate (S2O82?) reduction was investigated. Under optimized condition, the concentration calibration range, detection limit, and sensitivity were 0.1 μM–2 mM, 90 nM and 125.8 nA/μM, respectively, using hydrodynamic amperometry technique. 相似文献
203.
204.
Ahmad VU Iqbal S Kousar F Bader S Arshad S Tareen RB 《Chemical & pharmaceutical bulletin》2005,53(9):1126-1130
Phytochemicals investigation of the whole plant of Zygophyllum atriplicoides resulted in the isolation of two new triterpenoidal saponins together with a known compound. The structure of the new compounds atriplicosaponin A (1) and atriplicosaponin B (2) were established as 3-O-[alpha-D-glucopyranosyl-(1-->2)-beta-D-xylopyranosyl]-hederagenin and 27 alpha-hydroxyurs-12-ene-3-O-[beta-D-glucopyranosyl(1-->4)(2-O-sulpho)-beta-D-quinovopyranoside] and known compound was identified as 3-O-[beta-D-glucopyranosyl]-beta-sitosterol. The structure elucidations of the compounds were based primarily on 1D and 2D-NMR analysis, including COSY, HMBC and HMQC correlations. 相似文献
205.
206.
Coordination complexes of modified hydrazine are prepared with Ni(II), Cu(II), and Zn(II) metal ions. The ligand is synthesized by removing the methoxy moiety of methyl anthranilate with nitrogen of hydrazine hydrate, creating new coordination site. The coordination complexes are synthesized by reacting the ABH ligand with dehydrated M(II) [Cu2+, Zn2+ and Ni2+] bromide in an inert environment. The structures of the coordination complexes are elucidated basing on the physical measurements including elemental analysis, NMR, IR, UV–Vis spectra, magnetic and conductance measurements. These results reflect the M(ABH)Br2 composition of the corresponding complexes. Thermal studies show the Irving William trend for the stability of complexes. Antibacterial activities and antifungal studies are also carried out in order to investigate the biological activity upon complexation. 相似文献
207.
Protonation of the highly reactive 1:1 intermediate produced in the reaction between alkyl or aryl isocyanides and electron-deficient acetylenic esters with 3,6-dihydroxypyridazine, leads to a vinylisonitrilium cation, which undergoes an addition reaction with the conjugate base of the 3,6-dihydroxypyridazine to produce dialkyl 3-(alkyl or arylamino)-5,8-dioxo-5,8-dihydro-1H-pyrazolo[1,2-a]pyridazine-1,2-dicarboxylates in good yields at room temperature. 相似文献
208.
AbstractA nonlinear general rate model (GRM) of liquid chromatography is formulated to analyze the influence of temperature variations on the dynamics of multi-component mixtures in a thermally insulated liquid chromatographic reactor. The mathematical model is formed by a system of nonlinear convection–diffusion reaction partial differential equations (PDEs) coupled with nonlinear algebraic equations for reactions and isotherms. The model equations are solved numerically by applying a semi-discrete high-resolution finite volume scheme (HR-FVS). Several numerical case studies are conducted for two different types of reactions to demonstrate the influence of heat transfer on the retention time, separation, and reaction. It was found that the enthalpies of adsorption and reaction significantly influence the reactor performance. The ratio of density time heat capacity of solid and liquid phases significantly influences the magnitude and velocity of concentration and thermal waves. The results obtained could be very helpful for further developments in non-isothermal reactive chromatography and provide a deeper insight into the sensitivity of chromatographic reactor operating under non-isothermal conditions. 相似文献
209.
Mass spectrometric imaging of brain tissue by time‐of‐flight secondary ion mass spectrometry – How do polyatomic primary beams C60+, Ar2000+, water‐doped Ar2000+ and (H2O)6000+ compare? 下载免费PDF全文
210.