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691.
TS-1分子筛的合成Ⅰ.29Si和1H NMR研究正硅酸乙酯的水解 总被引:2,自引:0,他引:2
利用29Si和1H NMR方法研究了TS-1分子筛合成过程中正硅酸乙酯(TEOS)的水解行为.1H NMR结果表明,TEOS在四丙基氢氧化铵(TPAOH)溶液中的水解速度快于在四乙基氢氧化铵(TEAOH)中的水解速度.TEOS水解后的29Si NMR谱显示,TEOS在TPAOH中水解产生的聚合硅酸根物种的分布与在TEAOH中的类似,都存在着单体、二聚、三聚及环聚等硅酸根物种的平衡,但TEOS-TEAOH体系中低聚硅酸根物种的浓度明显大于TEOS-TPAOH中的浓度.向水解后的样品中添加水,可促使多聚硅酸根物种转化为低聚物种.大量异丙醇的加入将导致单聚和二聚硅酸根物种的高聚.钛酸四丁酯加入到TEOS-TPAOH水解体系中得到的29Si NMR结果明显不同于TEOS-TEAOH水解体系. 相似文献
692.
Ariel Sluszny Michael S. Silverstein Shifi Kababya Asher Schmidt Moshe Narkis 《Journal of polymer science. Part A, Polymer chemistry》2001,39(1):8-22
Novel semi‐IPN (interpenetrating polymer networks) were synthesized through vinyl silane modification of unplasticized poly(vinyl chloride) (PVC) films using relatively low temperatures, relatively high vinyl silane contents, and several different processing routes. A free‐radical initiator was used to promote reaction of the vinyl groups, and an aqueous acetic acid solution was used to promote the methoxysilane hydrolysis and condensation (HC) reactions for siloxane crosslink formation. A gel consisting of silane alone was formed prior to the HC process, indicating the formation of a semi‐IPN. The gel content following the HC process far exceeded the silane content, indicating a significant amount of PVC was entrapped by the silane network. This conclusion is supported by the homogeneous molecular structure and morphology of the films. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 8–22, 2001 相似文献
693.
Neutral Rearrangement between Boryl and Silyl Groups in B-Halogenosubstituted Boryl-bis(silyl)hydroxylamines Dihalogenboranes, RBX2, react with lithiated N,O-Bis(trimethylsilyl)hydroxylamine to give B-halogeno-borylhydroxylamines RB(X)ON(SiMe3)2: X = F, R = Trip (Trip = 2,4,6-triisopropylphenyl) ( I a ), N(SiMe3)2 ( I b ), N(CHMe2)2 ( I c ), N(SiMe3)Dip (Dip = 2,6-diisopropylphenyl) ( I d ) and X = Cl, R = N(SiMe3)2 ( I e ). Depending upon the substituents on the boron atom a dyotropic rearrangement can be effected which transforms the compounds I a , I b und I e into the isomeric borylhydroxylamines RB(X)N(SiMe3)OSiMe3 II a , II b and II e . The compounds are characterized by their m. s. and n. m. r. (1H, 11B, 13C, 19F, 29Si) spectra and by elemental analyses. 相似文献
694.
MFI沸石上对二甲苯的热脱附 总被引:4,自引:0,他引:4
MFI沸石(ZS-5型)的骨架结构内含十氧元环的二维孔道[‘],孔容积0.18cm‘·g-‘,硅沸石(Silicallte-1)是骨架中不合铝的ZSM-5.’‘StMASNMR话可揭示沸石的结构对称性、硅铝比和局部缺陷[习.Nagy等人间提出St-OH缺陷在含铅量高时形成.Woolery等门则认为出OH完全是由于骨架内包藏的桂的存在而产生,并随铝合量降低而增大.ZSM-5、硅沸石的结构特征和对二甲苯(Px)的性质决定了Px在ZSM-5上的吸附特性·本文用’‘StMASNLDEL表征硅沸石及不同含铅量的H、Na型ZSM-5的结构,并用*W**G巾TA分析吸附于… 相似文献
695.
Chelate Complexes LM/n of Transition Metals with Phosphinoimidic Amidato Ligands R2P(NR′)2– (= L) Reaction of LLi with metal halides or metal halide complexes affords chelate complexes LM/n (L = R2P(NR′)2–; M = Cr+++, Co++, Ni++, Zn++). With the bulky ligand t-Bu2P(NSiMe3)2– and Ni(PPh3)2Cl2 or Ni(dme)Br2 (dme = dimethoxyethane) only halide bridged chelates [LNiHal]2 (Hal = Cl, Br) containing tetrahedral chromophors NiN2Hal2 were obtained. Main objects of investigation were the bischelates L2Ni 2 . 2 a (R = i-Pr, R′ = Me) and 2 c (R = Ph, R′ = Et) are planar, 2 b (R = i-Pr, R′ = Et) and 2 d–g (R, R′ = i-Pr, i-Pr; Ph, i-Pr; Et, SiMe3; Ph, SiMe3) tetrahedral. In solutions of 2 b and 2 c a conformational equilibrium planar (diamagnetic) tetrahedral (paramagnetic) exists that is shifted to the right with increasing temperature and is dominated by the tetrahedral ( 2 b ) or planar conformer ( 2 c ) at room temperature. As is the case with the isovalence electronic compounds [R2P(S)NR′]2Ni small substituents R′ apparently favour the planar state and in contrast to some complexes [R2P(O)NR′]2Ni no paramagnetic planar species 2 have yet been observed. These findings that are derived from the results of magnetic measurements and of UV/VIS as well as NMR spectroscopy are confirmed by crystal structure determinations: 2 a was found to be planar (orthorhombic; a = 3382.8(11), b = 1124.0(4), c = 8874(3); P21212; Z = 6), and 2 g to be tetrahedral (monocline; a = 1268.4(2), b = 1806.8(2), c = 1971.6(2), P21/n; Z = 4). The bite angle NNiN of the chelate ligand in 2 a (ca. 77°) is similar to those in paramagnetic planar complexes [R2P(O)NR′]2Ni (NNiO 74–77°) and shows that a small chelate bite does not necessarily imply paramagnetism of planar Ni(II) complexes. 相似文献
696.
697.