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61.
能源和环境危机是当今社会面临的两大关键课题,利用太阳光驱动化学反应、将太阳能转化为化学能是解决上述问题的重要措施。通过光催化分解水是直接利用太阳能生产氢燃料的有效策略。光催化水分解过程可以分为三个基元步骤:光吸收、电荷分离与迁移、以及表面氧化还原反应。助催化剂可有效提高电荷分离效率、提供反应活性位点并抑制催化剂光腐蚀的发生,进而提高水分解效率。助催化剂也可以通过活化水分子以提高表面氧化还原动力学,进而提升整体光催化反应的太阳能转换效率。本文综述了助催化剂在光催化反应中的重要作用以及目前常用的助催化剂类型,详细说明了在光催化全解水过程中双助催化剂体系的构建及作用机理,并根据限制全解水的关键因素提出了新型助催化剂的设计策略。 相似文献
62.
One-dimensional ordered water molecules entering and exiting from a carbon nanotube with an appropriate radius are studied
with molecular dynamics simulations. It can be found that a water molecule near the nanotube end is more likely to be expelled
from the nanotube if its dipole is almost perpendicular to the nanotube axis. The key to this observation is that those water
molecules are closer to the wall of the nanotube away from the equilibrium position of the Lennar-Jones (LJ) potential. Thus,
the interaction energy for those water molecules is relatively high. There are two particular structures of the perpendicular
water molecule depending on the dipole direction of the adjacent water molecule in the nanotube. Although the probabilities
of these structures are quite small, their contributions to the net flux across the nanotube end are approximately equal to
the predominant structures. The present findings further show the possibility of controlling the water flow by regulating
the dipole directions of the water molecules inside the nanochannels. 相似文献
63.
Two polymorphs of the inclusion compound [(n-C4H9)4N]+·(C13H9O3)-·H2O havebeen prepared and characterized by X-ray crystallography. Polymorph 1: triclinic P 1 , a =13.4982(2), b = 13.5743(2), c = 17.1996(2) , α = 67.045(1), β = 77.845(1), γ = 88.762(1)°, V =2830.43(7)3, Z = 4, R = 0.0491, wR = 0.1276; Polymorph 2: tetragonal P43, a = b = 13.53690(1) , c = 30.8491(8) , V = 5653.02(16)3, Z = 8, R = 0.0448, wR = 0.0984. In these two crystalstructures, the hydrogen-bonded ribbons built of 4,4 -dihydroxybenzophenone (DHBP, C13H10O3)anions and water molecules are orderly arranged to generate two-dimensional host layers, withtetrabutylammonium cations contained between the layers to form the sandwich-like inclusioncompounds. The structures of 1 and 2, which exist as two polymorphs, both display the similarpacking pattern and hydrogen-bond linking model. 相似文献
64.
采用密度泛函理论B3LYP方法, 在B3LYP/6-311++G(2d,2p)//B3LYP/6-311++G(d,p)基组水平上对乙醇-水分子团簇(C2H5OH(H2O)n (n=1-9))的各种性质进行研究, 如: 优化的几何构型、结构参数、氢键、结合能、平均氢键强度、自然键轨道(NBO)电荷分布、团簇的生长规律等. 结果表明, 从二维(2-D)环状结构到三维(3-D)笼状结构的过渡出现在n=5的乙醇-水分子团簇中. 此外, 利用团簇结合能的二阶差分、形成能、能隙等性质, 发现在n=6时乙醇-水分子团簇的最低能量结构稳定性较好, 可能为幻数结构. 最后, 为了进一步探讨氢键本质, 将C2H5OH(H2O)n (n=2-9)最低能量结构的各种性质与纯水分子团簇(H2O)n (n=3-10)比较, 结果表明前者与后者中的水分子之间氢键相似. 相似文献
65.
66.
A new cadmium(N) compound, {[ CdLu-(4,4'-dps) ]2(H2O)2]'(4'abs )2(H2O)2n 1 (4,4'-dps = 4,4'-dipyridylsulfide, 4-abs = deprotonated 4-amino benzenesulfonic acid), has been synthesized and structurally characterized. It belongs to the orthorhombic system, space group Pbcn with a = 19.950(3), b = 10.6381(13), c = 18.055(2)A, V= 3831.8(8) A3, Z = 4, C32H36CdN6010S4, Mr = 905.31, F(000) = 1848, μ= 0.850 mm^-1, Dc = 1.569 Mg/m^3, the final R = 0.0238 and wR = 0.0589 for 3080 observed reflections with I 〉 2σ(I). Complex I is a one-dimensional linear chain coordination polymer and the repeat unit is comprised of doubly charged cadmium complex cation, uncoordinated 4-aminobenzene sulfonate anions and water molecules. The cadmium(H) ion adopts a six-coordinate distorted octahedral geometry. Complex 1 is stabilized and linked into a three-dimensional layered structure through intermolecular O-H…O and N-H…O hydrogen bonds together with electrostatic force. The cyclic voltammograms and fluorescence spectrum of 1 were also measured. It shows one irreversible redox process and emits a very strong and sharp fluorescent band at about 341 nm. 相似文献
67.
68.
The compound (H3IDC)(Prz)0.5(H2O) (H3IDC = imidazole-4,5-dicarboxylate, Prz = piperazine) has been prepared from a hydrothermal approach and was characterized by IR analysis and X-ray diffraction. Its crystal structure consists of discrete 4,5-imidazole-dicarboxylate, H2O and piperazine molecules. The whole structural motif was assembled by three different non-covalent interactions of O-H…O, N-H…O and π-π stacking, which play an important role in packing the molecules. Interestingly, the connections between imidazole-4,5-dicarboxylate molecule and water molecule result in a helical polymeric chain. Crystal data for compound 1: monoclinic system, space group P21/c, a = 6.4600(13), b = 19.910(4), c = 6.9123(14) A^°, β = 94.26(3)°, V= 886.6(3) A^°^3, Z= 4, C7H10O5N3, Mr = 216.18. 相似文献
69.
A novel coordination polymer of [Zn(4-CPOA)(Phen)(H2O)]n (C21H16N2O6Zn,1,4-CPOA = 4-carboxylato-phenoxyacetate dianion and Phen = 1,10-phenanthroline) has been synthesized and characterized by elemental analysis,IR,TG,PL and single-crystal X-ray diffraction. The crystal crystallizes in the triclinic system,space group of P1 with a = 9.622(3),b = 9.631(3),c = 11.526(4)A,α = 67.719(5),β = 71.203(5),γ = 83.552(6)o,V = 935.5(5) A^3,Z = 2,Dc = 1.625 g/cm^3,μ = 1.357 mm^-1 and F(000) = 468. The Zn(II) ion is surrounded by three carboxylate O atoms from two different 4-CPOA groups,two N atoms from the Phen ligand and one water molecule,forming a distorted octahedral coordination configuration. The Zn(II) ions were alternately interlinked by carboxylate groups of 4-CPOA with chelating bisbidentate and monodentate modes into a one-dimensional zigzag chain having an intrachain distance of ca. 9.631(1) . Under the direction of supramolecular recognition and attraction,the adjacent chains yield a double-stranded chain through π-π stacking between the phen ligands,which was further expanded into a 2-D framework via strong C–H–π interaction (ca. 2.95(1) ) between the 4-CPOA ligands and into a 3-D supramolecular network by strong hydrogen bond between terminal water molecule and carboxyl group. TG/DTG shows that its chain skeleton is thermally stable up to 419 oC and the blue fluorescent emission of the complex was determined at 471 nm in a solid state with its long decay lifetime of 1.83 ns. 相似文献
70.
用分子动力学模拟的方法揭示了结构水分子在糖原合成酶激酶-3β(GSK-3β)中的作用. 如果没有结构水, ATP嘌呤环的结合位置将发生偏移以填补结构水留下的空间; ATP结合口袋中的氢键网络将被破坏, 保守残基Lys85与ATP的磷酸根侧链只能形成一个保守氢键, 无法维持磷酸根转移所需的线性关系; 由于失去了氢键网络的稳定作用, Glu97和Lys85会向远离ATP的方向移动, 并导致Arg96的侧链发生偏转, 使Arg96无法保持与Arg180和Lys205之间正常的相对位置, 最终影响GSK-3β与底物的结合. 相似文献