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101.
We combined scanning tunneling microscopy and density functional theory to establish the structure-functionality relationship for nanometer-sized defects on TiO2(1 1 0). Three-angstrom high topographically distinct dots are ascribed to stoichiometric TiO2 nanoclusters with low coordination numbers. The under-coordinated O atoms of the nanocluster, with surface O atoms, provide exceptionally strong binding sites for Au nanoparticles. Our atomistic model elucidates a number of characteristics salient to low temperature CO oxidation by Au nanoparticles. 相似文献
102.
Results on the paper's theme are reviewed. Attention is focused mainly on the use of transients of current and open-circuit potential for elucidating changes in the structure of the electrical double layer (EDL) caused by the CO adsorption. It is shown that the high binding energy of CO with surfaces of platinum metals leads to a strong suppression of the total differential capacitance of the electrode, the recharge of the surface, the displacement of strongly adsorbed atoms formed during the adsorption of ions with a total charge transfer, and to other alterations in the EDL plates facing both solution and metal. The importance of allowing for double-layer effects when solving problems of electrocatalysis on platinum metals is emphasized. 相似文献
103.
F
A1:Ag+ color center at the low coordination (100) and (110) surface sites of KCl and KBr thin films play an important role in providing
tunable laser oscillation and adsorbatesubstrate interactions. Double-well potentials at this site are investigated using
ab initio molecular electronic structure calculations. The calculated Stokes shifted (optical transition bands), opticaloptical
conversion efficiencies, the probability of orientational destruction, exciton (energy) transfer and Glasner-Tompkins empirical
rule suggest that laser light generation is sensitive to (i) the lattice anion, (ii) the coordination number of surface ions,
and (iii) the choice of the basis set centered on the anion vacancy. The adsorbate-substrate interactions were found to be
dependent on the electronegativity of the adatom and on the lattice anion. Optimised geometries and the coadsorption of CO
and (F, Cl, Br, I) on KCl and KBr (100) crystals are presented. Calculated chemisorption energies for CO on the (halogen atom/defect
free sites of KCl and KBr (100) crystals) showed that the coadsorption of halogen atom tends to block other adsorbate-substrate
interactions at the nearest neighbour sites. Thus if halogen atom coverage increases, the CO prefers to be adsorbed on the
K+ site of the KCl and KBr (100) surfaces and on KBr relative to KCl.
相似文献
104.
We have studied the structural behavior of lead monoxide (PbO) as a function of pressure via angular dispersive X-ray diffraction employing two different pressure transmitting media that were quasi-hydrostatic (N2) and non-hydrostatic (MgO), respectively. Besides litharge (-PbO) and massicot (β-PbO), which are both stable at ambient pressure, there is an orthorhombic γ-PbO phase which appears upon application of pressure to -PbO. We have found that the orthorhombic γ-PbO phase is favored by shear stress under non-hydrostatic conditions. -PbO shows strong anisotropy in compressibility. The a-axis is rather incompressible with a linear stiffness coefficient of Ka0=540(30) GPa whereas the c-axis stiffness is Kc0=25(1) GPa. The bulk modulus of -PbO is K0=23.1(3) GPa and its derivative . 相似文献
105.
Salim Derrouiche 《Applied Surface Science》2007,253(13):5894-5898
The heats of adsorption at several coverages of the linear and bridged CO species (denoted L and B, respectively) adsorbed on the Pt0 sites of the 2.9 wt% Pt/10% K/Al2O3 catalyst are determined using the Adsorption Equilibrium Infrared spectroscopy method. The addition of K on 2.9% Pt/Al2O3 modifies significantly the adsorption of CO on the Pt particles: (a) the ratio L/B is decreased from 8.4 to 1, (b) a new adsorbed CO species is detected with an IR band at 1763 cm−1, (c) the heats of adsorption of L and B CO species are significantly altered and the positions of their IR bands are shifted. The heats of adsorption of L CO species are decreased: i.e. 206 and 105 kJ/mol at low coverages on Pt/Al2O3 and Pt/K/Al2O3 respectively. Two B CO species denoted B1 and B2, with different heats of adsorption are observed on Pt/K/Al2O3. The heats of adsorption of B2 CO species (major B CO species) are significantly larger than those measured in the absence of K: i.e. 94 and 160 kJ/mol at low coverages on Pt/Al2O3 and Pt/K/Al2O3 respectively, whereas those of B1 CO species (minor species) are similar: 90 kJ/mol at low coverages. These values are consistent with the qualitative High Resolution Electron Energy Loss Spectrometry literature data on Pt(1 1 1) modified by potassium. 相似文献
106.
Taketoshi Matsumoto Patricia Nickut Kazuya Watanabe Tatsuya Tsukuda Katharina Al-Shamery 《Surface science》2007,601(22):5226-5231
Reduction of oxidized gold nanoclusters by exposures to foreign gases and irradiation of UV photons has been investigated using X-ray photoelectron spectroscopy. Gold nanoclusters with narrow size distributions protected by alkanethiolate ligands were deposited on a TiO2(1 1 0) surface with dip coating. Oxygen plasma etching was used for removal of alkanethiolate ligands and oxidization of gold clusters. The oxidized gold clusters were exposed to CO, C2H2, C2H4, H2, and hydrogen atoms. Although, C2H4 and H2 did not show any indications of reduction of oxidized gold clusters, CO, C2H2, and hydrogen atoms reduced the oxides on gold cluster surfaces. Among them, hydrogen atoms were most effective for reduction. Irradiation of UV photons around 400 nm could also reduce the oxidized gold clusters. The photochemical reduction mechanism was proposed as follows. The photo-reduction was initiated by electronic excitation of gold clusters and oxygen atoms activated reacted with carbon atoms at the surfaces of gold clusters. Carbon species were likely absorbed in gold clusters or remained at the boundaries between gold clusters when gold clusters agglomerated during oxygen plasma exposures. As the photochemical reduction progressed, carbon atoms segregated to the surfaces of gold clusters. 相似文献
107.
The adsorption of CO on epitaxially grown Pt films of variable thickness has been studied using infrared-absorption spectroscopy, scanning tunnelling microscopy and thermal desorption spectroscopy. Depending on the number of pseudomorphic Pt layers (NPt = 1-4) the internal and external CO stretching modes (νC-O and νPt-CO, respectively) display characteristic frequency shifts due to the vanishing influence of the underlying Ru(0 0 0 1) substrate and Pt/Ru interface. For thicker layers (NPt ? 5) when this influence has become negligible, the compressive stress within the Pt film is gradually relieved, leading to a dislocation network. The structural heterogeneity during the ongoing relaxation process of the Pt film is reflected in the νC-O line shape; no line broadening is observed for either pseudomorphic or very thick films (NPt ? 15). For NPt ? 3 the adsorption of CO on Pt/Ru(0 0 0 1) films closely resembles CO on Pt(1 1 1), with residual deviations in line position and desorption temperatures gradually converging to zero. 相似文献
108.
Zhenhua Li Ying Song Pa Du Xinbin Ma Baowei Wang Genhui Xu 《Reaction Kinetics and Catalysis Letters》2001,73(1):135-142
The kinetics of hydrolysis of tetrahydrozoline hydrochloride in aqueous solution at 353, 363 and 368 K in the pH-range from
2.00 to 12.20 has been investigated. The decomposition products have been investigated by HPLC.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
109.
H2和CO在间二甲苯中的溶解度和体积传质系数的研究 总被引:5,自引:1,他引:4
使用IL搅拌釜,在温度80~160℃,压力0.5~5.0MPa范围内,实测了H2和CO在间二甲苯中的溶解度和体积传质系数。结果表明,两者均随温度和压力的升高而增大。实验结果与工于正规溶液理论Prausnitz-Shair法计算的气体溶解度比较相符。在相同温度、压力条件下,CO的溶解度和体积传质系数比H2大。相同温度、压力下不同液相介质中H2和CO的体积传质系数排序如下:(kLa)MEF〉(kLa) 相似文献
110.
研究了水/ 甲苯乳化液中二苯并噻吩( 硫芴) 在分散型钼酸、磷钼酸和四硫钼酸铵催化剂存在下的加氢脱硫反应. 反应在高压釜中于340 ℃及三种不同的气氛即H2 ,H2/H2 O和CO/H2O(CO 和H2O 经水煤气转换反应( WGSR) 产生原位氢) 的存在下进行. 用GC和GCMS鉴定、分析了气体和液体产物的组成. 结果表明: 对硫芴的加氢脱硫反应,在分散型四硫钼酸铵催化剂存在下,原位产生的氢的效果仅比加入的氢气稍好,而在分散型钼酸和磷钼酸催化剂存在下,原位产生的氢远比加入的氢气有效. 实验结果还表明: 硫化氢能显著提高分散型钼酸和磷钼酸催化剂的加氢脱硫活性,但在分散型四硫钼酸铵催化剂存在下,硫化氢能促进加氢反应而抑制氢解反应. 一氧化碳和水均选择性地抑制氢解反应. 相似文献