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991.
992.
F Xu L X Sun Z C Tan J G Liang T Zhang 《Journal of Thermal Analysis and Calorimetry》2006,83(1):187-191
Molar heat capacities
of acetaminophen were precisely measured with a small sample precision automated
adiabatic calorimeter over the temperature range from 80 to 330 K. A solid-solid
transition at 149.96 K was found from the Cp,m-T curve. The polynomial functions of Cp,.m(J
K-1 mol-1) vs. T were established
on the heat capacity measurements by means of the least square fitting method.
Thermal decomposition
processes of acetaminophen have been studied by thermogravimetry. And the
thermal decomposition kinetics parameters, such as activation energy E, pre-exponential factor A
and reaction order n, were calculated by
TG-DTG techniques with the Freeman-Carroll method, Kissinger method
and Ozawa method. Accordingly the thermal decomposition kinetics equation
of acetaminophen is expressed as: dα/dt=2.67·107e-89630/RT(1-α)0.23.
The process of fusion has been investigated through
DSC. The melting point, molar enthalpy and entropy of fusion are to be (441.89±0.04)
K, 26.49±0.44 kJ mol-1 and 59.80±1.01
J K-1 mol-1,
respectively. 相似文献
993.
994.
995.
新型酰乙基葡甲胺树脂的合成及吸硼性能 总被引:1,自引:0,他引:1
采用一步法, 用氯乙酰化聚苯乙烯树脂(PS-Acyl-Cl)与葡甲胺反应制得一种同时含有α-酰乙基胺和邻羟基双官能团的新型酰乙基葡甲胺树脂, 考察了溶液pH值、 温度、 初始浓度和吸附时间对酰乙基葡甲胺树脂吸附硼的影响. 结果表明, 在实验浓度范围内, 该树脂对硼的吸附符合Langmuir方程, 最大吸附量约为28.1 mg/g干树脂, 优于氯甲基树脂制得的硼特效树脂. 表明α-酰乙基胺和邻羟基双官能团对硼有双重或协同吸附作用. 该树脂在pH=6.0时对硼的吸附量最大; 温度对树脂吸附的影响不大; 树脂解吸率大于96%; 树脂重复使用5次后吸附量基本不变. 动力学研究结果表明, 吸附过程为液膜扩散控制过程. 相似文献
996.
电分析化学学会组织的特邀报告(电化学与材料)组有:(1)A Bralter-Toth等,微电极的傅里叶转换伏安法——原理与应用;(2)N Kim,单壁碳纳米管的扫描电化学显微术;(3)P J Kalesza等,高效率生物电催化集成系统的研发与特性鉴定;(4)B J Marguis等,暴露在可变物理性能的贵金属纳米材料下,进行塔电池的改变的衰减功函数的电化学分析;(5)A Karomerich等,可能应用于神经刺激与传感的、导电聚合物改性的电极;(6)Y SSingh等,活体伏安法的长期稳定性与准确性的因素——碳纤维微电极涂层;(7)J G Roberts等,碳纤维微电极电化学预处理引起的表面改变的研究;(8)A Polpke等,碳纳米管阵列的提高功能化的处理。 相似文献
997.
利用聚电解质对多壁碳纳米管(MWNT)的表面进行修饰,能有效改善碳纳米管在溶剂中的分散性.首先将经硝酸氧化的碳纳米管与二甲亚砜和乙二醇反应,得到羟基修饰的碳纳米管.然后利用羟基与α-溴异丁酰溴(或α-氯丙酰氯)的酯化反应,在碳纳米管的表面引入了原子转移自由基聚合(atom transfer radical polymerization,ATRP)引发基团,引发丙烯酸叔丁酯(tBA)或4-乙烯基吡啶(4VP)聚合,通过投料比的改变,得到接入量不同的聚合物修饰的碳纳米管.利用热重分析(TGA)和红外对聚合物修饰的碳纳米管进行表征.将聚合物修饰的碳纳米管进行水解(或季胺化),制备得到在水溶液中良好分散的聚电解质修饰的碳纳米管. 相似文献
998.
Characterization and Three-dimensional Structural Modeling of Humic Acid via Molecular Mechanics and Molecular Dynamic Simulation 总被引:2,自引:0,他引:2
The humic acid(HA) sample obtained from the alluvial soil was characterized by elemental composition, pyrolysis gas chromatography-mass spectrometry(Py-GC-MS) and solid-state 13C nuclear magnetic resonance (13C NMR) spectroscopy. There is high fat content and a few nitrogen-containing functional groups in HA. Py-GC-MS demonstrates the characterization and structural identification of HA. One long list of identified pyrolysis products was proposed for the construction of conceptual model of HA. Solid-state 13C NMR data indicate there are higher values of alkyl-C, O-alkyl-C and aryl-C in HA. The elemental composition, structural carbon distribution and L3C NMR spectroscopy of simulated HA are consistent with those of experimental HA. HyperChem was used to simulate the three-dimensional molecular structure of the monomer, which was optimized by the molecular mechanics of the optimized potential for liquid simulations(OPLS) force field and molecular dynamics simulation to get the stable and balanced conformation. The deprotonation process study depicts that the degree of ionization of HA gets deeper, while the electronegativity of HA and the energy of van der Waals(vdW) increase. Moreover, the 3D structure of humic acid with -4 charges is the most stable. The deprotonation process is an endothermic process. 相似文献
999.
采用盐酸回流法和氨水沉淀法合成了氧化铝载体,并通过络合真空浸渍法制备了不同来源氧化铝负载的Pt-Sn-K/γ-Al2O3催化剂。利用N2物理吸附、CO脉冲吸附、H2程序升温还原、NH3程序升温脱附、热重等手段对Pt-Sn-K/γ-Al2O3催化剂进行了表征,以异丁烷脱氢为探针反应研究了氧化铝载体对该催化剂脱氢性能的影响。结果表明,与由盐酸回流法合成的载体制备的催化剂相比,采用氨水沉淀法合成的氧化铝载体制备的Pt-Sn-K/γ-Al2O3催化剂表面具有较小的Pt颗粒和较弱的酸性分布,其脱氢活性及异丁烯选择性更优。14 d的连续运行数据显示,由氨水沉淀合成的载体制备的催化剂,其抗积炭能力更强,反应后催化剂的积炭石墨化程度更低,因而具有更好的稳定性;在该催化剂上,异丁烷初始转化率为56.67%,14 d后仍能达到34.71%,异丁烯初始选择性为80%,7 d后维持在94%左右。 相似文献
1000.
Chitosan, a naturally abundant biopolymer, has widely been studied for metal adsorption from various aqueous solutions, but the extension of chitosan as an adsorbent to remove humic substances from water has seldom been explored. In this study, chitosan was coated on the surface of polyethyleneterephthalate (PET) granules through a dip and phase inversion process and was examined for humic acid removal in a series of batch adsorption experiments. Scanning electron microscopic (SEM) images showed that the PET granules were uniformly covered with a layer of chitosan and the chitosan layer possessed numerous open pores on the surface. Zeta potential study indicated that the chitosan-coated granules had positive zeta potentials at pH < 6.6 and negative zeta potentials at pH > 6.6. Adsorption of humic acid onto the chitosan-coated granules was found to be strongly pH-dependent. Significant amounts of humic acid were adsorbed under acidic and neutral pH conditions, but the adsorption capacity was reduced remarkably with increasing solution pH values. The adsorption isothermal data under various initial humic acid concentrations (at the same solution pH value) can be adequately modeled by the Langmuir and Freundlich models. X-ray photoelectron spectroscopy (XPS) revealed that the amino groups of the chitosan layer were protonated due to humic acid adsorption, suggesting the formation of organic complex between the protonated amino groups and humic acid. Kinetic study indicated that the adsorption process was transport-limited at low solution pH values, but became both transport- and attachment-limited at high solution pH values. 相似文献