全文获取类型
收费全文 | 13184篇 |
免费 | 1685篇 |
国内免费 | 1198篇 |
专业分类
化学 | 4157篇 |
晶体学 | 464篇 |
力学 | 458篇 |
综合类 | 72篇 |
数学 | 2302篇 |
物理学 | 5106篇 |
无线电 | 3508篇 |
出版年
2024年 | 24篇 |
2023年 | 148篇 |
2022年 | 220篇 |
2021年 | 365篇 |
2020年 | 395篇 |
2019年 | 375篇 |
2018年 | 276篇 |
2017年 | 405篇 |
2016年 | 454篇 |
2015年 | 475篇 |
2014年 | 602篇 |
2013年 | 924篇 |
2012年 | 683篇 |
2011年 | 898篇 |
2010年 | 691篇 |
2009年 | 835篇 |
2008年 | 840篇 |
2007年 | 930篇 |
2006年 | 798篇 |
2005年 | 614篇 |
2004年 | 578篇 |
2003年 | 523篇 |
2002年 | 503篇 |
2001年 | 441篇 |
2000年 | 437篇 |
1999年 | 343篇 |
1998年 | 326篇 |
1997年 | 246篇 |
1996年 | 222篇 |
1995年 | 222篇 |
1994年 | 181篇 |
1993年 | 108篇 |
1992年 | 132篇 |
1991年 | 95篇 |
1990年 | 94篇 |
1989年 | 80篇 |
1988年 | 52篇 |
1987年 | 72篇 |
1986年 | 40篇 |
1985年 | 86篇 |
1984年 | 54篇 |
1983年 | 38篇 |
1982年 | 52篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 33篇 |
1978年 | 17篇 |
1977年 | 25篇 |
1976年 | 19篇 |
1975年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
121.
本文提出了一种快速远场近似(FAFFA)加速的混合物理光学矩量法(POMM),利用FAFFA加速计算矩阵方程中的矩阵矢量积,明显提高了计算效率.对物体表面上的远场组之间的耦合作用推导出了一组简洁的计算公式,并分析了计算复杂度.复杂金属组合体上线天线输入导纳、互导纳和方向性图的计算结果与文献结果一致.利用该方法分析计算了一个舰船模型上线天线的电磁特性.数值结果表明了这种方法的正确性和工程应用中的有效性. 相似文献
122.
The nature of hydrologic parameters in reservoir management models is uncertain. In mathematical programming models the uncertainties are dealt with either indirectly (sensitivity analysis of a deterministic model) or directly by applying a chance-constrained type of formulation or some of the stochastic programming techniques (LP and DP based models). Various approaches are reviewed in the paper. Moran's theory of storage is an alternative stochastic modelling approach to mathematical programming techniques. The basis of the approach and its application is presented. Reliability programming is a stochastic technique based on the chance-constrained approach, where the reliabilities of the chance constraints are considered as extra decision variables in the model. The problem of random event treatment in the reservoir management model formulation using reliability programming is addressed in this paper. 相似文献
123.
S. A. Savkov 《Fluid Dynamics》2003,38(3):501-506
A dependence of the heat transfer between coaxial cylinders on the energy accommodation coefficient is obtained. The known methods of solving a kinetic equation are compared. 相似文献
124.
125.
126.
查健江 《光纤与电缆及其应用技术》2004,1(4):14-19
人们对光纤生产过程中外汽相沉积(OVD)工艺的沉积机理的研究已经有好多年,但实际生产过程中,很多因素都会影响沉积速率和效率。为此我们通过试验,研究了决定沉积速率和沉积效率的主要因素,如预制棒表面温度、SiCl4流量和SiO2颗粒的温度等。 相似文献
127.
J.-Q. Shen H.-Y. Zhu P. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):305-313
There exist a number of typical and interesting systems and/or models, which possess three-generator Lie-algebraic structure,
in atomic physics, quantum optics, nuclear physics and laser physics. The well-known fact that all simple 3-generator algebras
are either isomorphic to the algebra sl (2, C) or to one of its real forms enables us to treat these time-dependent quantum systems in a unified way. By making use of
both the Lewis-Riesenfeld invariant theory and the invariant-related unitary transformation formulation, the present paper
obtains exact solutions of the time-dependent Schr?dinger equations governing various three-generator Lie-algebraic quantum
systems. For some quantum systems whose time-dependent Hamiltonians have no quasialgebraic structures, it is shown that the exact solutions can also be obtained by working in a
sub-Hilbert-space corresponding to a particular eigenvalue of the conserved generator (i.e., the time-independent invariant that commutes with the time-dependent Hamiltonian). The topological property of geometric phase factors and its adiabatic limit in time-dependent systems is briefly
discussed.
Received 6 July 2002 / Received in final form 21 October 2002 Published online 11 February 2003 相似文献
128.
利用现代教育理论,结合物理实验的教学实际,探讨和研究了探索性物理实验的双重教育功能.通过具体的探索性物理实验案例,验证了探索性物理实验具有激发学生的兴趣、发展学生的探索精神和唤起教师创造性的双重教育功能. 相似文献
129.
H. Fan A. Wright J. Gabaldon A. Rodriguez C.J. Brinker Y.‐B. Jiang 《Advanced functional materials》2006,16(7)
The synthesis of three‐dimensionally ordered, transparent gold‐nanocrystal (NC)/silica superlattice thin films using the self‐assembly (by spin‐coating) of water‐soluble gold nanocrystal micelles and soluble silica is reported by Fan and co‐workers on p. 891. The robust, 3D NC/silica superlattice films are of interest for the development of collective optical and electronic phenomena, and, importantly, for the integration of NC arrays into device architectures. Nanocrystals and their ordered arrays hold many important applications in fields such as catalysis, surface‐enhanced Raman spectroscopy based sensors, memory storage, and electronic and optical nanodevices. Herein, a simple and general method to synthesize ordered, three‐dimensional, transparent gold nanocrystal/silica superlattice thin films by self‐assembly of gold nanocrystal micelles with silica or organosilsesquioxane by spin‐coating is reported. The self‐assembly process is conducted under acidic sol–gel conditions (ca. pH 2), ensuring spin‐solution homogeneity and stability and facilitating the formation of ordered and transparent gold nanocrystal/silica films. The monodisperse nanocrystals are organized within inorganic host matrices as a face‐centered cubic mesostructure, and characterized by transmission electron spectroscopy and X‐ray diffraction. 相似文献
130.
介绍了电泳技术制备YBCO高温超导厚膜的实验方法和YBCO高温超导厚膜的电学性质测量 ,讨论了在学生小型科研实验或设计实验中开展此实验的学时安排、注意事项和实验内容的扩展 . 相似文献