全文获取类型
收费全文 | 5316篇 |
免费 | 824篇 |
国内免费 | 811篇 |
专业分类
化学 | 2574篇 |
晶体学 | 35篇 |
力学 | 892篇 |
综合类 | 65篇 |
数学 | 612篇 |
物理学 | 2773篇 |
出版年
2024年 | 10篇 |
2023年 | 60篇 |
2022年 | 139篇 |
2021年 | 153篇 |
2020年 | 163篇 |
2019年 | 166篇 |
2018年 | 180篇 |
2017年 | 190篇 |
2016年 | 252篇 |
2015年 | 230篇 |
2014年 | 313篇 |
2013年 | 483篇 |
2012年 | 323篇 |
2011年 | 359篇 |
2010年 | 310篇 |
2009年 | 324篇 |
2008年 | 334篇 |
2007年 | 326篇 |
2006年 | 331篇 |
2005年 | 284篇 |
2004年 | 265篇 |
2003年 | 216篇 |
2002年 | 209篇 |
2001年 | 167篇 |
2000年 | 154篇 |
1999年 | 155篇 |
1998年 | 147篇 |
1997年 | 123篇 |
1996年 | 90篇 |
1995年 | 92篇 |
1994年 | 81篇 |
1993年 | 47篇 |
1992年 | 48篇 |
1991年 | 36篇 |
1990年 | 19篇 |
1989年 | 29篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1982年 | 18篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1973年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有6951条查询结果,搜索用时 0 毫秒
101.
与传统网格法相比, 光滑粒子流体动力学方法不能直接施加壁面边界条件, 这就限制了该方法在工程中的应用.为此, 本文基于Galerkin加权余量法并结合传统排斥力方法, 推导出一种新的排斥力公式来施加壁面边界条件.该方法不含未知参数, 能在不减小边界粒子尺寸的情形下有效地防止流体粒子穿透壁面, 同时可避免邻近边界的流体粒子的速度及压力振荡. 分别通过静止液柱算例、液柱坍塌算例、容器中液体静止算例及溃坝算 例来验证本文方法的有效性, 并与传统边界处理方法进行对比, 结果表明: 本文方法克服了传统方法存在的缺陷, 是一种有效的固壁边界处理方法.
关键词:
光滑粒子流体动力学法
固壁边界
排斥力
加权余量法 相似文献
102.
103.
104.
具有超顺磁性和荧光特性的CdTe@Fe_3O_4/P(NIPAM-co-AA)多功能复合微球是以P(NIPAMco-AA)为模板制备而成.首先,采用溶胀法使模板微球带有磁性;其次,辅助TEOS和APTES两种化学试剂实现对Fe_3O_4/P(NIPAM-co-AA)微球表面的氨基功能化;最后,携带氨基的磁性微球与巯基乙酸修饰的CdTe量子点通过酰胺缩合反应,将量子点键合到磁性微球表面上,最终获得单分散的磁性荧光高分子复合微球.分别采用扫描电子显微镜、透射电子显微镜、倒置荧光显微成像系统、荧光分光光度计以及振动样品磁强计等方法对所获复合材料的结构与性能进行了表征.结果表明:复合微球单分散性良好,平均粒径约为30μm,饱和磁化强度可达5.4emu/g,具有良好的超顺磁性和较高的荧光发光效率.该材料将磁性、荧光结合到微米级高分子共聚物上,不仅解决了纳米粒子分离和处理的困难,而且奠定了多功能材料在生物标记、荧光成像等诸多领域潜在的应用基础. 相似文献
105.
106.
107.
Mesoporous silica coatings were synthesized on dense liquid silica-coated magnetite particles using cetyl-trimethyl-ammonium chloride (CTAC) as molecular templates, followed by sol-gel process. A specific surface area of the synthesized particles as high as 150 m2/g was obtained. After functionalization with mercapto-propyl-trimethoxy-silane (MPTS) through silanation reaction, the particles exhibited high affinity of mercury in aqueous solutions. Atomic force microscopy (AFM), zeta potential measurement, thermal gravimetric analysis (TGA), analytical transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS) were used to characterize the synthesis processes, surface functionalization, and mercury adsorption on the synthesized magnetite particles. The loading capacity of the particles for mercury was determined to be as high as 14 mg/g at pH 2. A unique feature of strong magnetism of the synthesized nanocomposite particles makes the subsequent separation of the magnetic sorbents from complex multiphase suspensions convenient and effective. 相似文献
108.
Let be the first return time to of sums of increments given by a functional of a stationary Markov chain. We determine the asymptotic behavior of the survival probability, for an explicit constant . Our analysis is based on a connection between the survival probability and the running maximum of the time-reversed process, and relies on a functional central limit theorem for Markov chains. As applications, we recover known clustering results for the 3-color cyclic cellular automaton and the Greenberg–Hastings model, and we prove a new clustering result for the 3-color firefly cellular automaton. 相似文献
109.
An analysis is performed to study the free convection of a dusty‐gas flow along a semi‐infinite isothermal vertical cylinder. The governing equations of the flow problem are transformed into non‐dimensional form and the resulting nonlinear, coupled parabolic partial differential equations have been solved numerically using an implicit finite difference scheme of Crank–Nicholson type. The flow variables such as gas–velocity, dust‐particle velocity and temperature, shearing stress and heat transfer coefficients are calculated numerically for various parameters occurring in the problem. It is observed that due to the presence of dust particles, the gas velocity is found to decrease. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
110.
We present a formalism to describe collisional correlations responsible for thermalization effects in finite quantum systems. The approach consists in a stochastic extension of time dependent mean field theory. Correlations are treated in time dependent perturbation theory and loss of coherence is assumed at some time intervals allowing a stochastic reduction of the correlated dynamics in terms of a stochastic ensemble of time dependent mean-fields. This theory was formulated long ago in terms of density matrices but never applied in practical cases because of its complexity. We propose here a reformulation of the theory in terms of wave functions and use a simplified 1D model of cluster and molecules allowing to test the theory in a schematic but realistic manner. We illustrate the performance in terms of several observables, in particular global moments of the density matrix and single particle entropy built on occupation numbers. The occupation numbers remain fixed in time dependent mean-field propagation and change when evaluating the correlations, then taking fractional values. They converge asymptotically towards Fermi distributions which is a clear indication of thermalization. 相似文献