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81.
蔡若冰 《广东微量元素科学》1995,2(12):28-33
探讨了血清、头发中Cu、Zn及Cu/Zn比值对肺癌、肝癌及胃肠道肿瘤的诊断价值,检测了171例样品,并与156名健康者进行对比研究.结果显示血清和头发Cu、Cu/Zn可作为恶性肿瘤的筛选指标,发Cu、Cu/Zn有助于肺癌临床分期,血清Cu有助于肝癌诊断和预示进展程度,而Cu/Zn可能对胃肠道肿瘤的诊断和预后更有用. 相似文献
82.
Summary Rare earth elements 1,3,5-benzenetricarboxylates were prepared as solids of the general formula Ln(C9H3O6)·nH2O, where n=6 for La-Dy and n=4 for Ho-Lu,Y. Their solubilities in water at 293 K are of the order 10-4-10-6 mol dm-3. The IR spectra of the complexes indicate that the carboxylate groups are bridging and bidentate chelates. Hydrated 1,3,5-benzenetricarboxylates
lose water molecules during heating in one step (La-Tb), two steps (Y, Ho-Tm) or three steps (Dy, Yb, Lu). The anhydrous complexes
are stable up to 573-742 K and decompose to oxides (Ce-Lu) at higher temperatures. 相似文献
83.
本工作通过比较端视与侧视ICP的分析性能,研究了端视ICP系统对稀土元素的分析特性。高频发生器输出功率与载气流量对端视与侧视ICP激发特性的影响没有明显差异,取光方式的不同是二者分析性能差异的根本原因。端视ICP由于取光时避开了产生连续背景的环形热区和截取了整个中心通道的光谱,其背景减小,谱线强度增强,获得较好的测定下限。对14种稀土元素测定下限的比较表明:端视ICP比铡视ICP下降10-30倍。 相似文献
84.
用原子捕获技术提高火焰原子吸收光谱法的灵敏度 总被引:1,自引:0,他引:1
采用简易的石英原子捕获器,使Cu,Ag,Au,Zn,Cd,Pb,Sb,Bi等易挥发元素在空气-乙炔火焰原子吸收光谱法中的灵敏度提高了3~5倍,并有较好的精密度,相对标准偏差在1%左右,方法中用此技术测定了标准物质中Pb、Cd的含量,获得了满意的结果,它较之石墨炉原子吸收光地具有快速,简便的特点,具有较大的实用价值。 相似文献
85.
吕明松 《广东微量元素科学》1997,4(7):52-54
以临床典型病案为例,探讨了中医中药传统理论和现代微量元素研究的关系,重点讨论了向量元素锌、宏量元素钙与高血压、风湿症的病因病机和治疗关系。 相似文献
86.
计算了43种不对称变色酸双偶氮膦酸型显色剂的Am拓扑指数,并将其与结构选择性因子相结合,用于偶氮类显色剂结构与铈显色反应对比度的相关性研究,讨论了显色剂结构对拓扑指数有译比度的影响。 相似文献
87.
Compounds A3M5 (A = alkaline earth, M = triel/tetrel): A Case Study on Structural and Electronic Factors Stabilizing Polar Intermetallics Starting from the non electron precise binary compounds Ca3Ga5/Sr3In5 (Hf3Ni2Si3 type) and Ba3Al5 at one hand and Ba3Pb5 (Pu3Pd5 type) at the other hand, a series of new ternary intermetallics of the general formula A3M5 (A: alkaline earth, M: triel/tetrel) has been synthesized, structurally characterized and studied by band structure calculations. The chemical substitution of M in A3M5 allows, via the continous variation of the radius ratio (rA:rM) and the valence electron number (VE/M) the detection of the geometrically and electronically determined stability ranges of the three structure types formed by the binary compounds. At values of rA:rM between 1.30 and 1.52 in the triel rich region of A3M′xM″5?x the Hf3Ni2Si3 type (orthorhombic, space group Cmcm) is formed: In Ca3Ga5 up to 1.8 Ga can be substituted by Al, in Sr3In5 similar amount of In can be replaced by either Al or Ga. The mixed trielide Sr3Al2.6Ga2.4 (a = 468.4(1), b = 1132.5(1), c = 1570.0(2) pm, R1 = 0.0261) can be obtained, although both corresponding binary phases are not known. At larger values of the ratio rA/rM as in Ba3Al3Ga2 (Ba3Al5 type, hexagonal, space group P63/mmc, a = 598.9(1), c = 1456.0(3) pm, R1 = 0.0353) layers of condensed M5 building blocks with Al‐Al partial bonds are formed. Substituting one In position in Sr3In5 against Pb results in the isotypic, but electron precise Zintl compound Sr3In4Pb (a = 506.1(1), b = 1191.8(3), c = 1650.2(4) pm, R1 = 0.0286), where the Fermi level in shifted into a distinct minimum of the density of states. Conversely, at the tetrele rich end of the series A3InxPb5?x, characterized by compounds of the Pu3Pd5 type (orthorhombic, space group Cmcm) with almost isolated nido clusters M5, a minimum of the DOS can be reached, if Pb is partially substituted by In (A3InxPb5?x with A = Sr/Ba: x = 0.7/0.6; a = 1084.6(2)/1118.6(2), b = 867.1(2)/904.4(1), c = 1104.8(2)/1133.9(2) pm, R1 = 0.0394/0.0434). 相似文献
88.
Thomas Müller 《Silicon Chemistry》2007,3(3-4):123-130
Quantum mechanical calculations at the B3LYP/6-311+G(d,p) and MP2/6-311+G(d,p) level of theory reveal that higher congeners
of the aromatic imidazolium ion, e.g. 2-E-imidazolium ions (E = Si, Ge, Sn), adopt either planar or pyramidal structures,
depending on the substituent R
2 attached to the element and on the group 14 element itsself. In the case of 2-silaimidazolium ions chemically significant
energy differences in favour of non-planar cations are predicted only for strongly σ-electron withdrawing substituents R
2 such as F or CF3. The pyramidalization computed for the germanium and tin analogues are however significant for all investigated substituents
R
2 and are accompanied by a substantial stabilization compared to the corresponding planar structures. A detailed bonding analysis
reveals that the non-planar cations are best described as complexes of monovalent group 14 element cations R
2E+ with the diazabutadiene ligand. 相似文献
89.
Darío Gmez Marina Dos Santos Fabin Fujiwara Griselda Polla Julieta Marrero Laura Dawidowski Patricia Smichowski 《Microchemical Journal》2007,85(2):276-284
A study was undertaken to evaluate the distribution of Al, As, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn in fly ashes collected in the electrostatic precipitator of a thermal power plant in San Nicolás (Argentina). Five samples were collected during one week of operation. For the fractionation, the scheme applied consisted in extracting the elements in four fractions namely (i) soluble and exchangeable elements; (ii) carbonates, oxides and reducible elements; (iii) bound to sulfidic metals; and (iv) residual elements. Metals and metalloids at μg g− 1 level were determined in each fraction by inductively coupled plasma optical emission spectrometry (ICP OES). For validation, a standard reference material (SRM 1633 coal fly ash) from NIST was subjected to the same chemical sequential extraction procedure that the samples. X-ray diffraction powder (XRD) analysis and scanning electron microscopy (SEM) were used to characterize the major minerals present in the matrix. Total analyte concentration (in μg g− 1) varied from 10.6 for Pb to 17,622 for Al. Minimum and maximum concentrations (in μg g− 1) found in individual samples in the four fractions were: Al, 92.7–9668; As, < 0.3–143; Cr, 2.0–10.4; Cu, < 0.2–35.6; Fe, < 0.3–4992; Mn, < 0.1–128; Ni, < 0.3–139; Pb, < 0.5–9.1; Ti, < 0.3–2243; V, 17.0–112.9; and Zn, < 0.1–68.2. The leachability of the 11 elements under study proved to be different. Low percentages of Al (1%), V (7%) and Cr (8%) were detected in the most bioavailable fraction. Arsenic was found to be most abundant in the non-silicate phase, represented by the second and third fractions, while Cr, Fe, Ni, Pb and Zn were mostly associated to the residual fraction. 相似文献
90.
Amitava Choudhury Larisa A. Polyakova Ingo Hartenbach Thomas Schleid Peter K. Dorhout 《无机化学与普通化学杂志》2006,632(15):2395-2401
Four related quaternary compounds containing rare‐earth metals have been synthesized employing the molten flux method and metathesis. The reactions of Eu and Rb2S5 with Si and Ge in evacuated fused silica ampoules at 725 °C for 150 h yielded RbEuSiS4 ( I ) and RbEuGeS4 ( II ), respectively. On the other hand, a reaction between CeCl3 and K4Ge4Se10 at 650 °C for 148 h has yielded KCeGeSe4 ( III ) and KPrSiSe4( IV ) was obtained by the reaction of elemental Pr, Si and Se in KCl flux at 850 °C for 168 h. Crystal data for these compounds are as follows: I , orthorhombic, space group P212121 (#19), a = 6.392(1), b = 6.634(2), c = 17.001(3) Å, α = β = γ = 90°, Z = 4; II , monoclinic, space group P21/m (#11), a = 6.498(2), b = 6.689(3), c = 8.964(3) Å, β = 108.647(6)°, Z = 2; III , monoclinic, space group P21 (#4), a = 6.852(2), b = 7.025(2), c = 9.017(3) Å, β = 108.116(2)°, Z = 2; IV , monoclinic, space group P21 (#4), a = 6.736(2), b = 6.943(2), c = 8.990(1) Å, β = 108.262(2)°, Z = 2. The crystal structures of I ‐ IV contain two‐dimensional corrugated anionic layers of the general formula, [LnEQ4]? (Ln = Ce, Pr, Eu; E = Si, Ge and Q = S, Se) alternately piled upon layers of alkali cations. In addition to structural elucidation, Raman and UV‐visible spectroscopy, and magnetic measurements for compound III (KCeGeSe4) are also discussed. 相似文献