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71.
J. Meyer 《Fresenius' Journal of Analytical Chemistry》1967,231(4):241-252
Zusammenfassung Es wird ein Verfahren zur Spurenbestimmung in Reinstsilber und Reinstsilberverbindungen beschrieben, das besonders für Routineanalysen geeignet ist. Das Verfahren beruht auf der hochselektiven Abtrennung des Matrixelementes von sämtlichen elektropositiveren Begleitspuren durch Reduktion mit Ameisensäure aus salpetersaurer Lösung, wobei das Silber als Amalgam abgeschieden wird. In der Spurenanreicherungslösung werden die für die Reinheitskontrolle von Silber und dessen Verbindungen wichtigsten Begleitelemente Pb, Cu, Cd, Zn amalgamvoltammetrisch, Tl, Ga, In, Fe, Ni, Mn flammenspektrometrisch und As photometrisch bestimmt. Die relativen Standardabweichungen liegen zwischen 2 und 13%, die Nachweisgrenzen zwischen 10–6 und 10–5%. Die prinzipiellen Möglichkeiten der Bestimmung weiterer Elemente sowie der Anwendung anderer Bestimmungsmethoden werden erörtert.über bisher bekannte Verfahren zur Spurenbestimmung in Silber wird berichtet.
Summary A method for the determination of trace amounts of metallic impurities in high-purity silver and silver salts is described. The procedure is based on an extremely selective separation of the silver matrix from all accompanying trace elements more electropositive than silver. The silver is separated by reducing a nitric acid solution of the sample with formic acid and depositing the silver as an amalgam. In the solution containing the enriched traces the elements being most important for the purity control of silver and its salts are detected voltammetrically (Pb, Cu, Cd, Zn), flame-spectrometrically (Tl, Ga, In, Fe, Ni, Mn) and photometrically (As). The relative standard deviations for the different elements were found to be between 0.02 and 0.13, the limits of detection between 10–6 and 10–5%. The possibilities to detect further elements and to apply other determination methods are pointed out.Previously known procedures for detecting trace amounts of impurities in silver are reported.相似文献
72.
Gerd Meyer 《无机化学与普通化学杂志》1981,478(7):39-51
Indium Sesquichloride, In2Cl3: a Pseudobinary, Mixed-valence Indium(I) Hexachloroindate(III) Colorless In2Cl3, obtained by reduction of InCl3 with metallic In, according to In[InIIICl6] a pseudobinary, mixed-valence indium(I) hexachloroindate(III), crystallizes orthorhombic (Pnma, Z = 32) with a = 1261.4(3), b = 2523.8(5), c = 1456.2(2) pm (Guinier-Simon data), Vm(In2Cl3) = 87.3 cm3 × mol?1. InIII occupies octahedral holes separated from each other (d?(InIII? Cl) = 251 pm). Coordination numbers of 7 to 11 are observed for InI (d?(InI? Cl) = 329–359 pm). In2Cl3 is isotypic with α-Tl2Cl3. 相似文献
73.
Victor E. Meyer 《Journal of polymer science. Part A, Polymer chemistry》1967,5(6):1289-1296
From the conversion–composition data of Gruber and Elias, the reactivity ratios of styrene (M1) and methyl methacrylate (M2) were calculated to be r1 = 0.55 ± 0.02 and r2 = 0.58 ± 0.06 at 90°C. The least-squares method was then used on these and literature values at other temperatures to obtain the Arrhenius expressions: In r1 = 0.04736 – (235.45/T), and ln r2 = 0.1183 – (285.36/T). Using literature values for the homopolymerization steps, A11 = 2.2 × 107l./mole-sec., E11 = 7.8 kcal./mole, and A22 = 0.51 × 107 l./mole-sec.?1, E22 = 6.3 kcal./mole, activation energies and frequency factors were then calculated for the cross-polymerization steps: A12 = 2.1 × 107 l./mole-sec., E12 = 7.3 kcal./mole, and A21 = 0.45 × 107 l./mole-sec., E21 = 5.7 kcal./mole. 相似文献
74.
75.
Crystalline samples of La3Ni2B2N3 were synthesized using solid state metathesis reactions from combinations of La, LaCl3, NiCl2 together with Li3BN2. The structure was determined by single crystal X‐ray diffraction (I4/mmm (No. 139), a = 372.95(2) pm, c = 2056.3(2) pm, R1 = 0.027, wR2 = 0.062) and confirmed earlier results from neutron powder diffraction. La3Ni2B2N3 contains BN units capping square planar Ni layers. Isolated nitrogen atoms reside in La6 octahedra. Magnetic measurements on several bulk samples exhibit superconductivity at temperatures below 14.6 K. 相似文献
76.
Cyclic Silicic Acid Derivatives By reaction of SiCl4 with oxygen at elevated temperatures a number of chlorsiloxanes consisting of more or less fused rings can be prepared of which those components of low molecular weight can be separated by combining distillation and crystallization. Methyl and ethyl esters of silicic acids are obtained by reaction with methyl or ethyl nitrite, resp. The compounds are characterized by silicon n.m.r. and mass spectroscopy. 相似文献
77.
Metalation of mesitylene with butyllithium in hexane in the presence of tetramethylethylenediamine yields mono-, di- and trilithiated benzylic compounds (1–5), characterized as their silylated derivatives. Dilithiation occurred partly at the same but preferentially at different methyls. The symmetrical tris-1,3,5-(lithiomethylene)benzene was the main product. Similar metalation occurred with m-xylene. o-Xylene gave also dilithiated products, but at a slower rate, and p-xylene gave slowly and exclusively the gem-dilithio-derivative.The results were explained by greater stabilization of polylithio derivatives with charges all on the starred carbons of the conjugated system, rather than those with charges uniformly dispersed on all carbons. CNDO/2 calculations of the energy of the anions account only partially for the order of stability of most of the studied compounds, but a good correlation between this experimental order and the energies of the lithium compounds was found. 相似文献
78.
A. Zschunke H. Meyer I. Heidlas B. Messbauer B. Walther H.-D. Schdler B. Thomas 《无机化学与普通化学杂志》1983,504(9):117-127
31P and 195Pt N.M.R. Investigations on Diplatinum (I) Complexes of the Type [Pt2(μ-SPR2)2L2] (L = PR3, PhP(OPh)2, P(OPh)3, CNR) 31P-, 195Pt-chemical shifts and 195Pt–31P- resp. 31P–31P-coupling constants of a series of doubly bridged diplatinum(I) complexes are reported. 31P-coordination chemical shifts of the terminal ligands of complexes of type [Pt2(μ-SPR2)2(P′R3′)2] and some of the various coupling constants are strongly influenced by the π-acceptor strength of these ligands. J(195Pt–195Pt) is found to change the sign among the series of complexes investigated. Thermal singlett triplet exitation giving rise to the paramagnetism of these complexes observed by preliminary EPR-measurements and confirmed by EHT-calculations is deduced from the large values of 2J(P–P′) and 3J(P′P′) as well as the unusually high temperature dependence of some coupling constants and other NMR features. The chemical stability of the doubly bridged core, the coordination shifts of the bridging phosphorus atoms and EHT-calculations suggest a view of aromaticity of the [Pt2(μ-SPR2)2](M–M) unit of these complexes. 相似文献
79.
N-Deacetylcolchiceine ( 7 ), readily available from colchicine ( 1 ), was converted into N-trifluoroacetyl-deacetylcolchiceine ( 8 ). Methylation of 8 with methyl iodide in the presence of potassium carbonate afforded a mixture of N-trifluoroacetyl-demecolcine ( 10 ) and its isomer 11 . The mixture of 10 and 11 was detrifluoroacetylated and separated by chromatography to afford demecolcine ( 2 ) and isodemecolcine ( 12 ). A more practical route to 2 started with 8 , and gave N-trifluoroacetyl-deacetylcolchicine ( 13 ) and its isomer 14 after O-methylation with diazomethane. N-Methylation of 13 and 14 with methyl iodide and potassium carbonate afforded 10 and 11 . The overall yield in the conversion of colchicine ( 1 ) into demecolcine ( 2 ) via 7, 8 and 13 was 55%. 相似文献
80.
The electron density difference in a NaSCN crystal is set up from the ab initio densities of Na+ and SCN? ions and compared to the experimental counterpart based on X-ray diffraction measurements. Numerical integration over the electron density difference is executed around the Na+ ion. The atomic charge (+0.20e) derived in this way is in good agreement with the analogous experimental charge (+0.27e) The low experimental value cannot therefore be taken as an indication for a predominantly non-ionic structure of NaSCN and similar sodium salts 相似文献