全文获取类型
收费全文 | 248篇 |
免费 | 3篇 |
专业分类
化学 | 188篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 23篇 |
物理学 | 33篇 |
出版年
2017年 | 6篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 4篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1970年 | 6篇 |
1969年 | 3篇 |
1968年 | 10篇 |
1967年 | 5篇 |
1966年 | 3篇 |
1965年 | 4篇 |
1964年 | 3篇 |
1963年 | 3篇 |
1962年 | 4篇 |
1961年 | 3篇 |
1959年 | 2篇 |
1958年 | 5篇 |
1957年 | 2篇 |
1956年 | 6篇 |
1955年 | 5篇 |
1954年 | 4篇 |
1953年 | 7篇 |
1952年 | 3篇 |
1951年 | 6篇 |
1949年 | 2篇 |
排序方式: 共有251条查询结果,搜索用时 15 毫秒
181.
182.
A. Warwick R. Chapman J.L. Durell J.N. Mo J.A. Kuehner P. Skensved 《Nuclear Physics A》1981,356(1):33-47
Angular distributions of α-particles from the reaction 209Bi(t, α)208Pb (ground state) have been measured at bombarding energies Et = 8.5 MeV and Et = 9.0 MeV. Zero-range (ZR) DWBA analyses of the data are used to determine the radial extent of the wave function of the orbit in which the transferred proton is bound in 209Bi. The applicability of the sub-Coulomb ZR DWBA treatment is investigated by comparison of ZR and exact finite-range DWBA calculations. A value of the (t, α) normalization constant of (20.8 ± 3.1) × 104 MeV2 · fm3, based on forward dispersion relations, has been obtained from this comparison. The asymptotic amplitude of the wave function is measured directly and the rms radius is extracted via a Woods-Saxon model. A value of √〈r2〉 = 6.10?0.08+0.12 fm, corresponding to a point proton and to a local Woods-Saxon potential, is obtained. The rms radius and radial wave function of the proton are compared with the results of electron scattering and muonic atom data on targets of 209Bi and 208Pb and with the results of Hartree-Fock calculations. 相似文献
183.
184.
A simple and rapid semi-micro gravimetric procedure for the determination of carbon dioxide (0.005-60%) in coal, rocks and minerals is described. Particular advantages include small sample weights (0.25-1.0 g), high precision (relative standard deviation 0.01%) and improved speed of analyses (20 min). The apparatus is designed as a simple vertical layout to minimize bench space requirements and utilizes commercially available components to reduce the number of joints and rubber tubing connections. The low swept volume (165ml) gives good sensitivity and reduced analysis time, and the scavenging train ensures removal of water, halogens and gaseous sulphur compounds. 相似文献
185.
The preparation and structures of a variety of oxonium ion tetrachloroaurate(III) salts isolated from aqua regia are reported. The new compounds are [(H(5)O(2))(2)(12-crown-4)(2)][AuCl(4)](2) (1), [(H(7)O(3))(15-crown-5)][AuCl(4)] (2), [(H(5)O(2))(benzo-15-crown-5)(2)][AuCl(4)] (3), [(H(3)O)(18-crown-6)][AuCl(4)] (4), [(H(5)O(2))(dibenzo-24-crown-8)][AuCl(4)] (5), [(H(5)O(2))(4-nitrobenzo-15-crown-5)(2)][AuCl(4)] (6), [(H(3)O)(4-nitrobenzo-18-crown-6)][AuCl(4)] (7), [(H(11)O(5))(tetrachlorodibenzo-18-crown-6)(2)][AuCl(4)] (8), and [(H(7)O(3))(dinitrodibenzo-30-crown-10)][AuCl(4)] (9). A significant correlation between the degree of proton hydration and crown ether size is observed. Aryl crown ethers are nitrated in concentrated aqua regia, but nonnitrated products may be obtained in a dilute solution of aqua regia by reaction with aqueous HAuCl(4). 相似文献
186.
Zhou Q Hambley TW Kennedy BJ Lay PA Turner P Warwick B Biffin JR Regtop HL 《Inorganic chemistry》2000,39(17):3742-3748
The syntheses and spectral and structural characterizations of Zn(II) indomethacin [1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid = IndoH] complexes, as different solvent adducts, have been studied. The complexes are unusual in that both monomeric and dimeric complexes are formed and that this is the first example of the same carboxylato ligand binding via both carboxylate oxygen atoms in monomeric and dimeric Zn(II) complexes. The crystal structures of Zn-Indo complexes with N,N-dimethylacetamide (DMA), pyridine (Py), 1-methyl-2-pyrrolidinone (NMP), EtOH, and MeOH as solvent ligands, [Zn2(Indo)4(DMA)2].2DMA, 1, [Zn2(Indo)4(Py)2].2H2O, 2b, [Zn2(Indo)4(NMP)2], 3, cis-[Zn(Indo)2(EtOH)2], 4, and cis-[Zn(Indo)2(MeOH)2], 5, were determined. Complexes 1, 2b, and 3 crystallize in the triclinic space group P1 (No. 2): a = 13.628(2) A, b = 17.462(2) A, c = 11.078(1) A, alpha = 99.49(1) degrees, beta = 108.13(1) degrees, gamma = 110.10(1) degrees for 1; a = 13.347(3) A, b = 16.499(5) A, c = 10.857(1) A, alpha = 99.48(2) degrees, beta = 108.25(2) degrees, gamma = 106.24(2) degrees for 2; a = 14.143(3) A, b = 14.521(2) A, c = 11.558(2) A, alpha = 109.07(1) degrees, beta = 90.80(2) degrees, gamma = 116.40(1) degrees for 3. The three complexes exhibit dinuclear paddle-wheel structures with a Zn...Zn distance of 2.9686(6) A, Zn-ORCOO distances of 2.035(2)-2.060(2) A, and a Zn-ODMA distance of 1.989(2) A in 1, a Zn...Zn distance of 2.969(1) A, Zn-ORCOO distances of 2.020(3)-2.049(3) A, and a Zn-NPy distance of 2.036(3) A in 2, and a Zn...Zn distance of 2.934(1) A, Zn-ORCOO distances of 2.009(3)-2.051(3) A, and a Zn-ONMP distance of 1.986(3) A in 3. In these cases, the zinc ions are offset along the z direction such that the L-Zn...Zn-L moiety is nonlinear, unlike the Cu analogues. Each Zn has a square-pyramidal geometry bridged by four carboxylato ligands in the basal plane with the solvent ligands containing an O- or N-donor atom at the apex. Complexes 4 and 5 are isostructural, with space group C2/c (No. 15). For 4, a = 30.080(2) A, b = 5.3638(6) A, c = 24.739(2) A, beta = 90.342(7) degrees, and for 5, a = 29.419(2) A, b = 5.320(2) A, c = 24.461(2) A, beta = 90.840(4) degrees. The Zn resides on a 2-fold axis and the complexes have a distorted cis octahedral structure with Zn-ORCOO bond lengths of 2.183(3) and 2.169(3) A, a Zn-OEtOH bond length of 2.015(3) A in 4, Zn-ORCOO bond lengths of 2.195(2) and 2.151(2) A, and a Zn-OMeOH bond length of 2.022(3) A in 5. 相似文献
187.
Mouayed Q. Al-Abachi R. Belcher S.L. Bogdanski Alan Townshend 《Analytica chimica acta》1977,92(2):293-300
Formaldehyde (2–750 μg), acetaldehyde (0.05–1.0 μg) and acetone (0.4–3.5 smg) can be determined in aqueous solution (? 17.5 ml) by MECA. Sodium sulphite solution (5 ml, 500 p.p.m. S) and 1.5 ml of l M phosphoric acid are added and the delayed S2 emission from the sulphite addition compound in 5 ml of the solution is measured in a MECA cavity; a hydrogen-nitrogen flame is used. Mixtures of formaldehyde and acetone can be determined simultaneously on the basis of the resolved MECA peaks of their sulphite addition compounds, after evaporation of the excess of sulphite from the cavity. 相似文献
188.
An atomic absorption spectrophotometric procedure for the determination of 0.005 to 0.20% iron in a phosphoric acid solution of tungsten carbide is described. The method is rapid, preliminary separations are not required and the results obtained have been compared with those obtained by X-ray fluorescence. 相似文献
189.
Some metal halides (Mn, Co, Ni, Pb and possibly Fe) emit metal(I) halide spectra from the MECA cavity in hydrogen-nitrogen-air flames, in contrast to their behaviour in conventional aspiration flame systems. However, the emission intensity is too weak to provide sensitive analytical applications. Indium halides give intense emissions by either the MECA or aspiration method. Halogenated organic compounds give intense CH and C2 emissions. Cadmium halides give only an intense atomic emission. Sensitive methods for halides, indium, cadmium and organic compounds are thus possible. Mercury (II) halides and metal fluorides give no measurable emission in the cavity method. 相似文献
190.
Summary Phenylmercury (II) derivatives of chloride, bromide, iodide, sulphide and thiocyanate are obtained by treating aqueous acidic anion solutions with aqueous phenylmercury (II) nitrate, and are readily extractable into various organic solvents. Thermogravimetric and gas chroamtography analyses show their potential usefulness for the determination of the halides, notably chloride, at the sub-microgram level after a solvent extraction step. The gas chromatographic resolution obtainable between individual phenylmercurials also indicates the possibilities for simultaneous determination of these anions. 相似文献