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831.
建立了一种可同时对醛、酮糖进行精确定性和定量分析的方法。以肌醇作为内标,用80%乙醇超声提取,利用醋酸酐和HMDS+TMCS(1:3)进行差异衍生,在EI源下用SIM模式进行GC/MS分析。结果表明:11种标准单糖在1—4mg/L范围内线性良好;仪器检出限:醛糖在8.15—22.4μg/L之间;酮糖为2.32μg/L和3.47μg/L;高、中、低3个量的平均回收率在73.0%-95.7%,相对标准偏差在3.1%-10.0%。对枸杞游离单糖进行测定,各单糖含量分别在0.26—368.6mg/g。该方法弥补了以前单糖分析中的缺陷,对既含有醛糖又含有酮糖的样品可同时进行精确的定性定量分析。 相似文献
832.
The microwave-assisted acid-digestion for the determination of metals in coal by ICP-AES was investigated, especially focusing on the necessity of adding HF. By testing five certified reference materials, BCR-180, BCR-040, NIST-1632b, NIST-1632c, and SARM-20, it was found that the two-stage digestion without HF (HNO3 + H2O2 was used) was very effective for the pretreatment of ICP-AES measurement. Both major metals (Al, Ca, Fe, and Mg) and minor or trace metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) in coal gave good recoveries for their certified or reference values. The possibility of ‘HF-memory effect’ was cancelled by the use of a set of vessels which had been never contacted with HF. Twenty-four Japanese standard coals (SS coals) were analyzed by the present method, and the concentrations of major metals measured by the present method provided very high accordance with those from the authentic JIS (Japanese Industrial Standard) method. 相似文献
833.
In the previous paper(Ⅲ), the following equation of solvent effect in organic chemistry was suggested:
Ei=a﹒Ai(1-Va﹒VAi)+d﹒Di(1-Vd﹒VDi)+E0
Where Ei is a physical or chemical property of the substrate in the solvent i and E0 is that in n-hexane. Ai and Di are constants of electron acception and donation effect of the solvent i respectively. VAi and VDi are constants of electron acception and donation space effect of the solvent i respectively, a and d are the sensitivities of E of the substrate vs the change of Ai and Di. Va and Vd are the constants of electron acception and donation space effect of the substrate respectively. In IR spectra E could be substituted by the wavenumber(ν). Ai and VAi have been established for 18 organic solvents (n-C6H14, n-C7H16, cyclohexane, CCl4, Ph-Me, ClCH:CCl2, Et2O, CHCl3, C6H6, CH2Cl2, ClCH2CH2Cl, Ph-NO2, THF, 1,4-dioxane, Et-NO2. MeCO2Et, Me-NO2, Me-CN).
In this paper Di and VDi have been established for these solvents. The equation also has been tested by the νC-X(X=Cl, Br) of five alkylhalides (t-BuCl, n-C5H11Cl, t-BuBr, Et-Br, EtC(H)BrMe) and νC=O of three carboxyl compounds (t-BuCOMe, Me2CO, MHB) and seven organotin compounds [(Ph2MeSiCH2)3SnO2C-C6H4-X-p(X=H-, CH3-, CH3O-, NO2-, F-. Cl-, I-)].
The relationship (ν=ρ﹒σ+ν0) between νC=O of organotin compounds and Hammett constants(σ) of the substituted groups in different solvents was studied and a relationship betweenρ and Ai, VAi, Di, VDi of the solvents was found. 相似文献
Ei=a﹒Ai(1-Va﹒VAi)+d﹒Di(1-Vd﹒VDi)+E0
Where Ei is a physical or chemical property of the substrate in the solvent i and E0 is that in n-hexane. Ai and Di are constants of electron acception and donation effect of the solvent i respectively. VAi and VDi are constants of electron acception and donation space effect of the solvent i respectively, a and d are the sensitivities of E of the substrate vs the change of Ai and Di. Va and Vd are the constants of electron acception and donation space effect of the substrate respectively. In IR spectra E could be substituted by the wavenumber(ν). Ai and VAi have been established for 18 organic solvents (n-C6H14, n-C7H16, cyclohexane, CCl4, Ph-Me, ClCH:CCl2, Et2O, CHCl3, C6H6, CH2Cl2, ClCH2CH2Cl, Ph-NO2, THF, 1,4-dioxane, Et-NO2. MeCO2Et, Me-NO2, Me-CN).
In this paper Di and VDi have been established for these solvents. The equation also has been tested by the νC-X(X=Cl, Br) of five alkylhalides (t-BuCl, n-C5H11Cl, t-BuBr, Et-Br, EtC(H)BrMe) and νC=O of three carboxyl compounds (t-BuCOMe, Me2CO, MHB) and seven organotin compounds [(Ph2MeSiCH2)3SnO2C-C6H4-X-p(X=H-, CH3-, CH3O-, NO2-, F-. Cl-, I-)].
The relationship (ν=ρ﹒σ+ν0) between νC=O of organotin compounds and Hammett constants(σ) of the substituted groups in different solvents was studied and a relationship betweenρ and Ai, VAi, Di, VDi of the solvents was found. 相似文献
834.
本文以多种聚醚为软段,二异氰酸酯(MDI和TDI)为硬段,合成了多嵌段聚醚聚氨酯,以此聚氨酯为基材,与NaH及1,3-丙碳酸内酯反应,进一步合成了一系列不同离子化程度的阴离子型碳化聚氨酯离聚物,用交流阻抗谱仪测定了样品的阻抗谱,由此计算出样品的离子电导率。研究结果表明其他条件相同时,以聚乙二醇(PEG)为软段的样品具有较高的离子电导率;以聚环氧丙烷(PPO)为软段的样品次之,以聚四氢呋喃(PTMO)为软段的样品最低,对于离子化程度不同的聚氨酯离聚物以金属离子和烷氧单元之比为0.05时导电性能最好。阳离子为Li+和Na+的样品具有相近的离子电导率。 相似文献
835.
离子色谱柱切换技术同时测定食品中的多种成分 总被引:2,自引:0,他引:2
采用离子色谱柱切换技术同时测定了保留性质差别较大的有机酸以及不同价态的无机阴离子。由于柱切换基本不影响色谱基线,该法有较高的灵敏度。同时测定了食品中的乙酸,山梨酸、苯甲酸、糖精、氯离子和磷酸根。 相似文献
836.
Two novel sesquiterpene dimers, compounds 1 and 2 , were isolated from the rhizome of Ligularia virgaurea, together with the six known sesquiterpenoids 3 – 8 . Their structures were established by physico‐chemical and spectroscopic methods, especially by means of 1D‐ and 2D‐NMR as well as HR‐MS analyses. A mechanism based on a classical Diels–Alder cyclization is proposed for the formation of the dimer 1 from the precursors 8 and the quinone form of 6 (Scheme). 相似文献
837.
Ning Zhang Qing-Cheng Kong Zhen-Zhen Chen Ke-Hua Xu Bo Tang 《Mikrochimica acta》2007,158(1-2):165-171
A sensitive catalytic kinetic spectrofluorimetric approach for determining ng mL−1 levels of rhodium is presented, and the possible mechanism of the catalytic reaction was investigated. The determination
is based on the catalytic property of rhodium to enhance the reaction of o-vanillin salicylhydrazone (OVSH) with potassium
bromate in a water-ethanol medium at pH 4.80 and 45 °C. The presence of β-cyclodextrin (β-CD) obviously sensitized the assay
due to its high inclusion ability towards OVSH. Under optimized experimental conditions, fluorescence measurements of the
β-CD-rhodium-KBrO3-OVSH catalytic kinetic reaction system were carried out in its fluorescent band centered at λex = 333 nm and λem = 476 nm, respectively. The calibration graph was linear over the concentration range of 0.47–100 ng mL−1 with a detection limit of 0.14 ng mL−1. The effect of interferences was discussed, and the results show that the extraction method can be used to separate rhodium
from interference species such as iridium. The proposed method, applied to several synthetic mixtures containing rhodium mixed
with varying amounts of metal salts, produced satisfactory results. 相似文献
838.
The interaction between anionic surfactants and polyvinylpyrrolidone (PVP) are investigated using 13C NMR, ESR spectroscopy and surface tension measurements at the air/water interface. The behavior of single-chained surfactant,
sodium dodecyl sulphonate (AS), is compared with that of the double-chained surfactant, sodium bis(2-ethylhexyl) phosphate
(NaDEHP). The results showed that a surfactant–polymer complex of “necklace and head structure” is formed in AS aqueous solutions
in the presence of PVP due to the hydrophobic interaction between PVP and AS. The AS micelles nucleate on the polymer hydrophobic
sites, and the mobility of the AS head groups is not affected. But, for NaDEHP surfactant, it was found that PVP is little
effective in influencing the monomer–micelle equilibrium and no surfactant– polymer complex formed in the NaDEHP aqueous solution.
Received: 8 May 1996 Accepted: 14 August 1997 相似文献
839.
100公里以上的大气分子离子主要为NO~+。它的辐射特点及它与电子、原子或分子的相互作用,对于理解大气的化学过程具有特别重要的意义。为了研究这些过程,确定NO~+分子离子基态及其各个激发态的分子势能函数是非常重要的。精确的X~1Σ~+,A~1Ⅱ和a~3∑~+势能曲线已发表;基于光电子谱的研究发现了NO~+的其它激发态,但对于这些激发态的研究尤其是势能函数的研究不多。本文研究并导出NO~+的基态和10个激发态的势能函数。 相似文献
840.