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91.
Iodine-mediated 5-endo-dig cyclization of propargylic esters 2 at room temperature proceeded smoothly to give highly functionalized indolizines 3 in excellent yields. A pyridine group was employed as a nucleophilic partner in this facile process for the first time. 相似文献
92.
The iodides can be oxidated to iodine by O_2 in air because of their lower redox potential. In an acidic solution, this reaction can be accelerated by ultraviolet light. Because the iodine yielded from potassium iodide by light irradiating solution can react with other oxidizer components, the iodine is constantly consumed. When it arrives the terminal points of the reaction, the iodine appears. According to the reaction time of the iodine appearing the quantities of the components are determined. And the terminal points can be pointed out by the blue of the iodine-starch or potentiometric 相似文献
93.
94.
Doppler Global Velocimetry (DGV) is a whole-field measurement technique which has attracted significant interest from the fluid-flow research community since its introduction in 1991. Practical implementations of the methodology have focused on two principal laser light sources: the argon ion laser, applied to steady state or slowly varying flows; and the pulsed neodymium YAG laser for the measurement of instantaneous velocity fields. However, the emphasis in the published literature has been very much on research using the argon laser. This paper reports the application of a Q-switched, injection-seeded neodymium YAG laser to the proven Oxford DGV system, and the use of this combination in a short duration unsteady high-speed flow. The pertinent characteristics of the apparatus are described, and the impact of these on the integrity of the resulting velocity measurements is presented. Adaptations to the commercial laser system that make it suitable for application to the measurement of transient high-speed flows are described. Finally, the application of this system to a short duration unsteady flow is described. This application is based on the flow found in a new type of transdermal drug delivery device, where particles of the drug material are projected at high speed through the skin. Whole-field velocities are recorded, and values as high as 800 m/s are evident. 相似文献
95.
分光光度法测定土壤中碘的方法改进 总被引:2,自引:0,他引:2
对碳酸钠-氧化锌熔矿,分光光度法测定土壤样品中碘含量的方法进行改进,在不经过超级恒温水浴的情况下,对熔样温度、试剂用量的选择、比色温度等实验条件进行优化。改进后的方法经过国家一级标准物质分析验证,准确度ΔlgC0.05,相对标准偏差(RSD)10%,结果准确可靠,完全满足地球化学调查样品中对碘的质量要求,更加适合批量生产。 相似文献
96.
Pentafluorophenyliodine(III) Compounds. 4 [1] Aryl(pentafluorophenyl)iodoniumtetrafluoroborates: General Method of Synthesis, Typical Properties, and Structural Features Aryl(pentafluorophenyl)iodoniumtetrafluoroborates [Ar′Ar″I][BF4] (Ar′ = C6F5, Ar″ = C6H5, o‐C6H4F, m‐C6H4F, p‐C6H4F, 2,6‐C6H3F2, 3,5‐C6H3F2, 2,4,6‐C6H2F3, 3,4,5‐C6H2F3, C6F5) are prepared in good yields and high purity by the reaction of C6F5IF2 with Ar″BF2 in CH2Cl2. This convenient method can be applied generally to many iodonium compounds. Thermal and spectroscopic properties (1H, 13C, 19F NMR, IR, Raman) are reported and discussed. The solid state structures of six iodonium compounds show significant cation‐anion interactions which result in two different arrangements: a dimer with a 8‐membered ring or polymers with infinite zigzag chains. Ab initio calculations on prototypes of aryliodonium cations show relations between the kind of the aryl group (C6H5 vs. C6F5) and structural parameters as well as charges. By means of 19F NMR the σI‐ and σR‐constants of the [C6F5I]+‐substituent are determined. 相似文献
97.
Alexander J. Blake Robert O. Gould Wan-Sheung Li Vito Lippolis Simon Parsons Christian Radek Martin Schrder 《Angewandte Chemie (International ed. in English)》1998,37(3):293-296
The cations [Pd 2 Cl 2 L] 2+ and [KL 2 ′ + (L = [18]aneN2S4, L′ =[15]aneO5) have been used as templates for the synthesis of unique three-dimensional polyiodide networks. The metal cations in [Pd2Cl2L]1.5I5(I3)2 are linked into infinite chains by pairwise hydrogen bonding; the resulting cationic polymers run through channels formed by the extended polyiodide network. [KL2′]I9 shows a three-dimensional network of puckered cubic cages of I9− ions whose cavities are occupied by the metal cations (section from the structure shown on the right). 相似文献
98.
Nils Wiberg Harald Auer Heinrich Nth Jrg Knizek Kurt Polborn 《Angewandte Chemie (International ed. in English)》1998,37(20):2869-2872
The red-orange tetrasilacyclobutene 1 (R*=SitBu3) is formed quantitatively by the reaction of tetrasilatetrahedrane 2 and iodine. Surprisingly, water and methanol do not react with 1 with addition to the Si−Si double bond, but instead with replacement of the silicon-bound iodine atoms with oxygen or the methoxy group, respectively. The substitutions possibly proceed by dissociative activation via intermediate 3 . 相似文献
99.
100.
Crystal Structures of TMEDA Adducts and of Salts with Protonated TMEDA Molecules The reaction of TMEDA with two equivalents of [BH3(SMe2)] in toluene at 20 °C gives the adduct [TMEDA(BH3)2] ( 1 ). A similar reaction of pyrrolidine with [BH3(SMe2)] in a molar ratio of 1:1 leads to the adduct [pyrrolidine(BH3)] ( 2 ). TMEDA can be introduced into the coordination sphere of In3+ by the treatment of InI3 with TMEDA in toluene to give the complex [InI(TMEDA)] ( 3 ). The salt [HTMEDA]I ( 4 ), containing a mono‐protonated TMEDA molecule, is the result of the reprotonation of [NH4]I and TMEDA in toluene at 20 °C. The salts [H2TMEDA]—[InCl4(TMEDA)]2 ( 5 ) and [H2TMEDA][InCl5(THF)] ( 6 ) are formed in the reaction mixtures TMEDA/toluene/InCl3/HCl and TMEDA/toluene/THF/InCl3/HCl, respectively, whereupon 6 was characterized more closely. Crystals of [In5I6(OH)(TMEDA)4]I·2, 5toluene ( 7 ·2.5toluene) can be obtained after treatment of InI3 with non‐dried TMEDA; 4 was identifed as by‐product. 1 — 7 ·2.5toluene were partially investigated by NMR methods and vibrational spectroscopy. In all cases a characterization by single crystal X‐ray diffraction was performed. According to this, all nitrogen atoms in 1 and 2 are coordinated by BH3 groups leading to a distorted tetrahedral environment at the nitrogen and the boron atoms. In 3 a distorted trigonal‐bipyramidal coordination sphere at the In3+ is present. The apical positions are occupied by I3 and N3. Strong N‐H···N bridges, running along [001] is the feature in 4 ; the I—‐Ions are not involved into the system of H‐bridges. A ion triple, [H2TMEDA][InCl4(TMEDA)]2, hold together by bifurcated H‐bridges is the dominating structural motif in 5 , whereas alternation bifurcated and linear H‐bridges, leading zu a zig‐zag chain along [100], is the build‐up principle of 6 . In 7 ·2.5toluene a complex In5O8 skeleton was formed, consisting of a virtual corner‐connected doubled heterocubane. At every heterocubane a corner, occupied by a metal ion, is missing. The coordination spheres of the In atoms of the complex cation are completed by TMEDA molecules and iodide ions. 相似文献