全文获取类型
收费全文 | 4983篇 |
免费 | 772篇 |
国内免费 | 574篇 |
学科分类
数理化 | 6329篇 |
出版年
2024年 | 8篇 |
2023年 | 72篇 |
2022年 | 107篇 |
2021年 | 151篇 |
2020年 | 220篇 |
2019年 | 167篇 |
2018年 | 141篇 |
2017年 | 166篇 |
2016年 | 227篇 |
2015年 | 174篇 |
2014年 | 258篇 |
2013年 | 380篇 |
2012年 | 228篇 |
2011年 | 238篇 |
2010年 | 224篇 |
2009年 | 286篇 |
2008年 | 304篇 |
2007年 | 334篇 |
2006年 | 285篇 |
2005年 | 253篇 |
2004年 | 261篇 |
2003年 | 231篇 |
2002年 | 223篇 |
2001年 | 195篇 |
2000年 | 178篇 |
1999年 | 183篇 |
1998年 | 143篇 |
1997年 | 128篇 |
1996年 | 106篇 |
1995年 | 91篇 |
1994年 | 71篇 |
1993年 | 47篇 |
1992年 | 37篇 |
1991年 | 38篇 |
1990年 | 35篇 |
1989年 | 29篇 |
1988年 | 26篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1971年 | 4篇 |
1957年 | 5篇 |
排序方式: 共有6329条查询结果,搜索用时 15 毫秒
81.
82.
Charging of the surface of an oxide caused by the adsorption of hydrogen ions and ions of inert 1:1 electrolyte was investigated by using grand canonical Monte Carlo simulation technique. In particular, adsorption isotherms of protons as well as of ions of the electrolyte together with the resulting charge density of the surface were obtained for different system parameters. Also, the effect of the surface energetic heterogeneity and the concentration of the background electrolyte on the isotherms and the charge density curves was examined. Furthermore, lateral interactions in the mixed adsorbed phase were taken into account in the modeling of the system behavior. The obtained results, in general, suggest that the three factors mentioned above may have substantial influence on the charging mechanism at the liquid/oxide interface. 相似文献
83.
杨力平 《应用数学学报(英文版)》1994,10(3):233-251
FREEBOUNDARYPROBLEMARISINGFROMEVAPORATIONFROMPOROUSMEDIUMYANGLIPING(杨力平)(DepartmentofAppliedMathematics,TsinghuaUniversity,Be... 相似文献
84.
The line search method incorporating the Wolfe conditions is modified to ensure that a descent algorithm terminates in a finite number of steps at an approximate stationary point where the second-order conditions of optimality are satisfied. A simple procedure based on conjugate directions is proposed to determine directions of negative curvature. 相似文献
85.
In this paper, a model of translation gateway is proposed. The communications between IPv4 network and IPv6 network are realized by using the Microsoft intermediate driver technology in environment of Windows 2000. 相似文献
86.
对用Talbot效应及云纹干涉法测试镜面反射体曲率和斜率的灵敏度进行了分析,同时给出了由于光栅稀密对测试的影响和相应的解释。这对从事这项工作或工程上利用此技术测试物体曲率和斜率提供了一个可行的方案。 相似文献
87.
牛顿环实验中的误差分析 总被引:2,自引:0,他引:2
本文对牛顿环测透镜曲率半径实验中引起误差的各种原因进行分析讨论,指出了误差的主要来源及比较完善可行的处理方法。 相似文献
88.
A numerical technique is developed for the simulation of free surface flows and interfaces. This technique combines the strength on the finite element method (FEM) in calculating the field variables for a deforming boundary and the versatility of the volume-of-fluid (VOF) technique in advection of the fluid interfaces. The advantage of the VOF technique is that it allows the simulation of interfaces with large deformations, including surface merging and breaking. However, its disadantage is that is solving the flow equations, it cannot resolve interfaces smaller than the cell size, since information on the subgrid scale is lost. Therefore the accuracy of the interface reconstruction and the treatment of the boundary conditions (i.e. viscous stresses and surface tension forces) become grid-size-dependent. On the other hand, the FEM with deforming interface mesh allows accurate implementation of the boundary conditions, but it cannot handle large surface deformations occurring in breaking and merging of liquid regions. Combining the two methods into a hybrid FEM-VOF method eliminates the major shortcomings of both. The outcome is a technique which can handle large surface deformations with accurate treatment of the boundary conditions. For illustration, two computational examples are presented, namely the instability and break-up of a capillary jet and the coalescence collision of two liquid drops. 相似文献
89.
Tamara Elzein Virginie Kreim Achraf Ghorbal Sophie Bistac 《Journal of Polymer Science.Polymer Physics》2006,44(22):3272-3281
Friction‐deposited layers of atactic polystyrene (PS) on inert and OH‐grafted gold substrates were the subject of this study to establish a relationship between the friction process and the resulting anisotropy of the transferred polymer chains. We show, by using polarization‐modulation infrared reflection‐absorption spectroscopy that the deposited PS chains involve an anisotropy in which PS main backbone is rather perpendicular to the friction support, fact that is surprising when compared with the majority of polymers where the anisotropy is along the sliding direction. Moreover, our calculation of the orientation angles revealed that PS chains are more perpendicular in the transferred layers than in spin‐coated films. This particular anisotropy is probably due to a parallel reorientation of the phenyl ring on the friction support whatever the surface chemistry is. On the other hand, this study was useful to rectify the assignment of infrared bands unclearly reported in the literature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3272–3281, 2006 相似文献
90.
akir Aydoan Mustafa Salam Abdulmecit Türüt 《Journal of Polymer Science.Polymer Physics》2006,44(11):1572-1579
The polypyrrole/p‐InP structure has been fabricated by the electrochemical polymerization of the organic polypyrrole onto the p‐InP substrate. The current–voltage (I–V), capacitance–voltage (C–V), and capacitance–frequency (C–f) characteristics of the PPy/p‐InP structure have been determined at room temperature. The structure showed nonideal I–V behavior with the ideality factor and the barrier height 1.48 and 0.69 eV respectively. C–f measurements of the structure have been carried out using the Schottky capacitance spectroscopy technique and it has been seen that there is a good agreement between the experimental and theoretical values. Also, it has been seen that capacitance almost show a plateau up to a certain value of frequency, after which, the capacitance decreases. The higher values of capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the p‐InP that can follow the a.c. signal. The interface state density Nss and relaxation time τ of the structure were determined from C–f characteristics. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1572–1579, 2006 相似文献