全文获取类型
收费全文 | 18185篇 |
免费 | 2941篇 |
国内免费 | 4585篇 |
专业分类
化学 | 14751篇 |
晶体学 | 355篇 |
力学 | 937篇 |
综合类 | 384篇 |
数学 | 2618篇 |
物理学 | 6666篇 |
出版年
2024年 | 30篇 |
2023年 | 142篇 |
2022年 | 476篇 |
2021年 | 466篇 |
2020年 | 501篇 |
2019年 | 595篇 |
2018年 | 519篇 |
2017年 | 628篇 |
2016年 | 687篇 |
2015年 | 878篇 |
2014年 | 1002篇 |
2013年 | 1387篇 |
2012年 | 1528篇 |
2011年 | 1534篇 |
2010年 | 1304篇 |
2009年 | 1369篇 |
2008年 | 1547篇 |
2007年 | 1369篇 |
2006年 | 1233篇 |
2005年 | 1226篇 |
2004年 | 1013篇 |
2003年 | 770篇 |
2002年 | 882篇 |
2001年 | 835篇 |
2000年 | 801篇 |
1999年 | 447篇 |
1998年 | 347篇 |
1997年 | 289篇 |
1996年 | 220篇 |
1995年 | 196篇 |
1994年 | 185篇 |
1993年 | 159篇 |
1992年 | 151篇 |
1991年 | 116篇 |
1990年 | 138篇 |
1989年 | 94篇 |
1988年 | 101篇 |
1987年 | 80篇 |
1986年 | 70篇 |
1985年 | 37篇 |
1984年 | 38篇 |
1983年 | 48篇 |
1982年 | 46篇 |
1981年 | 41篇 |
1980年 | 26篇 |
1979年 | 18篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1964年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
According to a multiphase mixture theory, we have mathematically developed a multiphysical model with chemoelectromechanical coupling considerations, termed the multieffect‐coupling electric‐stimulus (MECe) model, to simulate the responsive behavior of electric‐sensitive hydrogels immersed in a bath solution under an externally applied electric field. For solutions of the MECe model consisting of coupled nonlinear partial differential governing equations, a meshless Hermite–Cloud method with a hierarchical iteration technique has been used for a one‐dimensional steady‐state analysis of a hydrogel strip. The computed results are compared with the experimental data, and there is very good agreement. Simulations within the domains of both hydrogels and surrounding solutions also present distributions of the ionic concentrations and electric potential as well as the hydrogel displacement. The effects of various physical parameters on the response behavior of electric‐stimulus responsive hydrogels are discussed in detail. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1514–1531, 2004 相似文献
4.
从激光推进的要求出发,阐述了用于激光推进的高功率激光器的选择原则,即激光器必须满足:(1)高的平均功率和峰值功率;(2)高的单脉冲能量;(3)高的重复频率;(4)优良的大气传输特性。主要分析了目前YAG固体激光器、自由电子激光器和TEA脉冲CO2激光器的特点,通过上述4个方面性能的比较,认为在目前水平下,TEA脉冲CO2激光器是进行激光推进的首选强激光源,其优点表现在:功率可达10kW量级,单脉冲能量可达0.5~1kJ,重复频率为20~40Hz;激光波长处于大气传输窗口,对大气变化不敏感;工作物质快速流动,不存在热透镜效应和破坏阈值;相关光学元件易于制造;光束质量较好;运行成本低。 相似文献
5.
We report on a new type of Fano effect, named as Andreev-Fano effect, in a hybrid normal-metal/supeeconductor (N/S) interferometer embedded with a quantum dot. Compared with the conventional Fano effect, AndreevFano effect has some new features related to the characteristics of Andreev reflection. In the Iinear response regime, the line shape is the square of the conventional Fano shape, while in the nonlinear transport, a sharp resonant structure is superposed on an expanded interference pattern, which is qualitatively different from the conventional Fano effect. The phase dependence of the hybrid N/S interferometer is also distinguished from those of all-N or all-S interferometers. 相似文献
6.
In this paper, we discuss the local and global existence ofweak solutions for some hyperbolicparabolic systems modellingchemotaxis. 相似文献
7.
8.
We report viscometric data collected in a Couette rheometry on dilute, single‐solvent polystyrene (PS)/dioctyl phthalate (DOP) solutions over a variety of polymer molecular weights (5.5 × 105 ≤ Mw ≤ 3.0 × 106 Da) and system temperatures (288 K ≤ T ≤ 318 K). In view of the essential viscometric features, the current data may be classified into three categories: The first concerns all the investigated solutions at low shear rates, where the solution properties are found to agree excellently with the Zimm model predictions. The second includes all sample solutions, except for high‐molecular‐weight PS samples (Mw ≥ 2.0 × 106 Da), where excellent time–temperature superposition is observed for the steady‐state polymer viscosity at constant polymer molecular weights. No similar superposition applies at a constant temperature but varied polymer molecular weights, however. The third appears to be characteristic of dilute high‐molecular‐weight polymer solutions, for which the effects of temperature on the viscosity curve are further complicated at high shear rates. The implications concerning the relative importance of hydrodynamic interactions, segmental interactions, and chain extensibility with increasing polymer molecular weight, system temperature, and shear rate are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 787–794, 2006 相似文献
9.
10.
In this paper, a projection method is presented for solving the flow problems in domains with moving boundaries. In order to track the movement of the domain boundaries, arbitrary‐Lagrangian–Eulerian (ALE) co‐ordinates are used. The unsteady incompressible Navier–Stokes equations on the ALE co‐ordinates are solved by using a projection method developed in this paper. This projection method is based on the Bell's Godunov‐projection method. However, substantial changes are made so that this algorithm is capable of solving the ALE form of incompressible Navier–Stokes equations. Multi‐block structured grids are used to discretize the flow domains. The grid velocity is not explicitly computed; instead the volume change is used to account for the effect of grid movement. A new method is also proposed to compute the freestream capturing metrics so that the geometric conservation law (GCL) can be satisfied exactly in this algorithm. This projection method is also parallelized so that the state of the art high performance computers can be used to match the computation cost associated with the moving grid calculations. Several test cases are solved to verify the performance of this moving‐grid projection method. Copyright © 2004 John Wiley Sons, Ltd. 相似文献