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1.
Amphiphilic aroma molecules, representatives of fragrance molecules, are introduced as dynamic volatile surfactants. Surface tension of their aqueous solutions proves to be a sensitive and revealing quantity, used for assessment of the adsorption-evaporation behavior both under equilibrium conditions and in regimes of no instantaneous equilibrium. Such volatile amphiphiles are characterized by fast adsorption from bulk solution at an air-water interface, on a timescale of tens of microseconds, and exhibit synergetic effect in mixtures with conventional micellar-forming surfactants. Their ability to evaporate from the interface on a time scale of minutes suggests their applications as “temporal” dynamic cosurfactants in technologies involving fast formation of new surfaces. Current challenges concern evaluation of specific material parameters of volatile aroma surfactants in order to enable their selection for targeted applications.  相似文献   
2.
Self-assembly is a versatile bottom-up approach for fabricating novel supramolecular materials with well-defined nano- or micro-structures associated with functionalities. The oil-water interface provides an ideal venue for molecular and colloidal self-assembly. This paper gives an overview of various self-assembled materials, including nanoparticles, polymers, proteins, and lipids, at the oil-water interface. Focus has been given to fundamental principles and strategies for engineering the self-assembly process, such as control of pH, ionic strength and use of external fields, to achieve complex soft materials with desired functionalities, such as nanoparticle surfactants, structured liquids, and proteinosomes. It has been shown that self-assembly at the oil-water interface holds great promise for developing well-structured complex materials useful for many research and industrial applications.  相似文献   
3.
以柴油为基液、溴化十六烷三甲基铵(Cetyltrimethyl Ammonium Bromide,CTAB)为助溶剂,通过两步法配制CNT(Carbon Nanotubc)、CeO2及Co3O4纳米燃油。采用悬滴法测量柴油与纳米燃油的表面张力,探究纳米物质种类、粒径、质量分数及温度对纳米燃油表面张力的影响。研究发现,在纳米燃油液滴气液界面层内,纳米粒子与柴油分子之间的吸引力使液固分子体系总体的内聚力增强,因而表面张力增大;纳米燃油的表面张力随着粒子质量分数增加而增强,但随着温度升高而线性下降。大粒径的纳米粒子表面电荷密度降低,对表面电子束缚减小,电子游离所产生的与柴油分子之间的极化静电相吸作用更强,使液粒之间的范德华力增强,表面张力增大。在相同质量分数的条件下,非金属CNT的密度较小,纳米燃油中的粒子数目较多,此外其得电子能力更强,极易使周围柴油分子极化形成静电吸引,液粒间范德华力增强,因此CNT纳米燃油的表面张力最大;同为金属氧化物,Co3O4的分子量大于CeO2而表现出较低的分子极性,其与基液燃油分子间的静电作用力也较弱,因而Co3O4纳米燃油的表面张力较低。本文测量了多种纳米燃油的表面张力,探讨了不同物质种类、浓度、尺寸的纳米介质及环境温度对燃油表面张力的影响,为纳米燃油在发动机缸内的液滴破碎与着火燃烧过程提供了重要的基础数据和理论支持。  相似文献   
4.
In this review, the experimental set-up and functional characteristics of single-wavelength and broad-band femtosecond upconversion spectrophotofluorometers developed in our laboratory are described. We discuss applications of this technique to biophysical problems, such as ultrafast fluorescence quenching and solvation dynamics of tryptophan, peptides, proteins, reduced nicotinamide adenine dinucleotide (NADH), and nucleic acids. In the tryptophan dynamics field, especially for proteins, two types of solvation dynamics on different time scales have been well explored: ~1 ps for bulk water, and tens of picoseconds for “biological water”, a term that combines effects of water and macromolecule dynamics. In addition, some proteins also show quasi-static self-quenching (QSSQ) phenomena. Interestingly, in our more recent work, we also find that similar mixtures of quenching and solvation dynamics occur for the metabolic cofactor NADH. In this review, we add a brief overview of the emerging development of fluorescent RNA aptamers and their potential application to live cell imaging, while noting how ultrafast measurement may speed their optimization.  相似文献   
5.
基于ARX系统辨识模型的钢绞线张拉力识别*   总被引:1,自引:0,他引:1       下载免费PDF全文
钢绞线是预应力结构和大跨索承体系桥梁的核心受力构件,其实际保有应力值将决定结构的承载能力和耐久性。以钢绞线超声导波传播过程为独立系统,外在激励和数据采集为系统的输入和输出,通过ARX系统辨识方法分析钢绞线张拉力引起的系统模型参数变化,并以模型参数为特征向量,构建张拉力识别指标。实验结果表明该识别指标具有良好的单调线性变化规律,确定系数达到0.964;传感器布置在钢绞线端面和侧面具有相似的规律性,相对而言,端面布置传感器识别指标的敏感性和线性规律更好;重复加卸载过程,识别指标线性拟合斜率比较稳定,受钢绞线应力加载路径影响较小。  相似文献   
6.
Ali Dogan 《哲学杂志》2019,99(15):1825-1848
The surface tensions of ternary and quaternary systems of Sn-based Pb-free solder alloys have been calculated using geometric models, such as Muggianu, Kohler, Chou’s general solution model (GSM), Toop, Guggenheim, ideal Butler and Butler models. It is observed from the calculation carried out in the present work that Sb and Bi contents decrease the surface tension of the solder alloys Sn-Zn-Sb-Bi. It is inferred from the statistical analysis that the best agreement between the experimental results and the corresponding calculated values of the surface tensions is generally observed in GSM and Muggianu models among the geometric models. Whereas Muggianu model is the most appropriate. Relatively good agreements have been observed between models considered in this study and experimental data.  相似文献   
7.
We consider the motion of a two-dimensional interface between air (above) and an irrotational, incompressible, inviscid, infinitely deep water (below), with surface tension present. We propose a new way to reduce the original problem into an equivalent quasilinear system which is related to the interface's tangent angle and a quantity related to the difference of tangential velocities of the interface in the Lagrangian and the arc-length coordinates. The new way is relatively simple because it involves only taking differentiation and the real and the imaginary parts. Then if assuming that waves are periodic, we establish a priori energy inequality.  相似文献   
8.
It is possible to obtain (excess) interfacial entropies from the temperature dependence of some characteristic surface parameter. Such excess entropies contain much valuable information. Their studies lead to deeper insight into the interfacial properties. In some cases, quite unexpected results are obtained. In the present paper, we shall consider three illustrations: (1) the surface excess entropy of the electrical double layer on silver iodide, (2) the surface excess entropy of the interface between air and electrolyte solutions and (3) the surface excess entropy of Langmuir polymeric monolayers. Their analysis starts with defining this characteristic parameter and measuring its temperature dependence, followed by a brief thermodynamic analysis to obtain the sought entropy.Given the generality of this methodology, its applicability is likely to be extended to a variety of other interfacial properties, in particular when competition between electric and non-electric forces plays a role as in self-assembly, hydrophobic bonding and polyelectrolytes.  相似文献   
9.
PMMA膨胀环动态拉伸碎裂实验研究   总被引:4,自引:1,他引:3  
在强动载作用下, 脆性材料的碎裂问题是一个重要的研究课题, 而脆性材料在冲击拉伸载荷下的力学行为的实验研究相对较匮乏. 提出了一种动态拉伸断(碎)裂的液压膨胀环实验技术, 可用于准脆性/脆性材料的动态拉伸. 利用该技术对有机玻璃(PMMA)圆环试件进行了不同膨胀速度下的动态碎裂实验研究. 从回收碎片的断口形貌和碎片内部残余裂纹观察可知试件的破碎由环向拉伸应力造成, 碎片断口处发出的稀疏波会将周围的拉伸应力卸载, 从而抑制其他裂纹的进一步发展. 利用超高速相机记录了试件的膨胀碎裂过程, 利用DISAR激光速度干涉仪获得了试件外表面粒子的径向膨胀速度历史, 通过试件上的应变片获得了试件的应变历史和断裂应变. 实验结果表明: 在拉伸应变率150~500s-1范围, 材料的动态断裂应变低于准静态加载下的断裂应变, 体现出“动脆”现象; 随着加载应变率的提高, PMMA 材料的碎片尺寸减小; 无量纲化的PMMA圆环的平均碎片尺寸介于韧性碎裂模型和脆性碎裂模型的预测数值之间, 反映出材料的准脆性特性.   相似文献   
10.
首先,对均布力作用下悬链线理论进行了深入分析研究,推导出求解水平张力单参数和双参数形式的隐含超越方程,在算法上验证了两种方程的等价性。对于悬链线固有的广义倾角、曲率半径、约束反力和水平张力的嵌入关系等给出了具有新意的表达公式。然后,建立了水平悬链线在对称集中力作用下的平衡方程,对于不同垂向集中力作用下水平张力的变化情况和最大垂直距离差所在水平位置随集中力的变化等进行了非线性计算。本文在理论构建和分析方面具有创新性,在理论探索和工程应用上具有重要意义。  相似文献   
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