全文获取类型
收费全文 | 11563篇 |
免费 | 1389篇 |
国内免费 | 474篇 |
专业分类
化学 | 6065篇 |
晶体学 | 552篇 |
力学 | 399篇 |
综合类 | 61篇 |
数学 | 942篇 |
物理学 | 5407篇 |
出版年
2024年 | 6篇 |
2023年 | 68篇 |
2022年 | 124篇 |
2021年 | 183篇 |
2020年 | 239篇 |
2019年 | 230篇 |
2018年 | 217篇 |
2017年 | 233篇 |
2016年 | 414篇 |
2015年 | 368篇 |
2014年 | 480篇 |
2013年 | 961篇 |
2012年 | 564篇 |
2011年 | 744篇 |
2010年 | 676篇 |
2009年 | 775篇 |
2008年 | 778篇 |
2007年 | 897篇 |
2006年 | 831篇 |
2005年 | 616篇 |
2004年 | 637篇 |
2003年 | 537篇 |
2002年 | 455篇 |
2001年 | 377篇 |
2000年 | 337篇 |
1999年 | 273篇 |
1998年 | 255篇 |
1997年 | 189篇 |
1996年 | 154篇 |
1995年 | 146篇 |
1994年 | 142篇 |
1993年 | 92篇 |
1992年 | 82篇 |
1991年 | 55篇 |
1990年 | 46篇 |
1989年 | 41篇 |
1988年 | 41篇 |
1987年 | 21篇 |
1986年 | 24篇 |
1985年 | 23篇 |
1984年 | 20篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1969年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
101.
Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) are employed to investigate the effects of nickel on the crystallization of the amorphous Zr70Cu20Ni10 alloy. We have found that the crystallization process of the amorphous Zr70Cu20Ni10 alloy is strongly influenced by the addition of nickel. Addition of 10 at% Ni to the Zr70Cu30 amorphous alloy makes the crystallization process proceed from a single-stage mode to a double-stage mode. The activation energy for crystallization of the amorphous Zr70Cu20Ni10 alloy is calculated to be about 388kJ·mol-1 on the basis of the Kissinger equation. The effects of nickel on the crystallization of the amorphous Zr70Cu20Ni10 alloy are discussed in terms of the genetics of metals. 相似文献
102.
103.
矩孔金属光栅矢量模式理论的数值计算 总被引:1,自引:0,他引:1
根据矩孔金属光栅的矢量模式理论,计算了不同入射方向,波长及偏振态情况下衍射场的分布,研究了不同光栅结构对衍射效率,偏振态变化的影响;同时,根据实际需要,加工制作了一批不同深度的矩孔光栅样品,进行了实验测量,并将计算值与实验值进行了比较,两者基本相符。 相似文献
104.
陈仙辉Department of Physics Structure Research Laboratory University of Science Technology of China Hefei PRC) 钱逸泰 陈祖耀 林春 《中国科学B辑(英文版)》1994,(2)
In this paper, the phase-formation mechanism of Bi-based superconductors was systematically investigated by using high-temperature X-ray diffraction, differential thermal analysis (DTA) and crystallization of amorphous state. The transformations among Bi-based 2201, 2212 and 2223 phases were observed, and the intergrown phenomenon of the 2201, 2212 and 2223 phases was explained. It was proposed that there exist a composition equilibrium between 2212 phase and Ca2CuO3 and a competition of thermody-namic stability among Ca2CuO3, 2212 and 2223 phases. This is why it is difficult to prepare the 2223 phase. After Pb was doped in Bi-Sr-Ca-Cu-O system, Ca2CuO3 phase in the Bi-Sr-Ca-Cu-O system was replaced by Ca2PbO4, so that the composition equilibrium and competition of thermodynamic stability mentioned above were avoided. 相似文献
105.
A. Waksberg 《International Journal of Infrared and Millimeter Waves》2002,23(9):1327-1335
Coupling losses have been calculated for laser resonators with unequal apertures and extended Fresnel Numbers. This was done using both, diffraction theory and a simple linear model.A close form expression was derived to calculate coupling losses with reasonable accuracies for a limited range of paramters. This should help in the preliminary design of hole coupling laser resonators. 相似文献
106.
Yang Lingxia Ge Debiao Wei Bing 《International Journal of Infrared and Millimeter Waves》2003,24(11):1893-1897
A modified formulation for fringe component of diffraction coefficient is implemented to TD-EEC method. An example of diffraction by perfectly conducting plate is used to illustrate our scheme. Comparing with the FDTD results we observe that the improved expression for fringe component is more accurate than that of Michaeli's formulation. This high frequency time domain technique is available for treating the bistatic scattering problems for millimeter waves. 相似文献
107.
动态模糊随机信息处理的数学方法 总被引:1,自引:1,他引:0
本文系统地概述了我们近年来提出的动态模糊随机信息处理的数学方法,内容包括模糊随机变量、模糊随机过程和模糊随机微分方程的基本解法等方面的基本概念、基本定义和某些重要的定理,以及动态系统的模糊随机响应与可靠性分析的方法等。这些方法是为我们研究工程实际问题的需要逐步发展起来的,对于处理某些类型的问题简便实用。 相似文献
108.
109.
二元光学波面变形器件的研究 总被引:4,自引:0,他引:4
基于计算全息原理设计了二元光学波面变形器件,一块二元光学器件的衍射效率比计算全息可提高4倍,高斯波面整形需要二块整形光学器件,二元光学器件的激光利用率比计算全息提高16倍,而且制做工艺简单. 相似文献
110.
Manju Rajeswaran Thomas N. Blanton David R. Whitcomb Nicholas Zumbulyadis Brian J. Antalek Scott T. Misture 《Journal of solid state chemistry》2006,179(4):1053-1059
In continuation of our interest in solid-state structures of silver complexes of photographic importance, the structure for silver benzotriazole (AgBZT), has now been obtained. The preferred method for solving crystal structures is via single-crystal X-ray diffraction (XRD). However, for some materials, growing single crystals of appropriate size and quality is often difficult or even impossible. AgBZT is an example of such a silver complex with poor solubility. The usual routes to preparing single crystals using recrystallization from a cooperating solvent resulted in polycrystalline powder samples. We propose a crystal structure for AgBZT, solved from synchrotron X-ray powder diffraction data, using a direct-space Monte Carlo simulated annealing approach. AgBZT crystals are monoclinic, (P21/c), with unit cell dimensions, a=14.8052(3) Å, b=3.7498(4) Å, c=12.3495(12) Å, and β=114.200(6)°. The AgBZT complex is constructed from all three of the Benzotriazole (BZT) nitrogens bonding to a separate silver atom. As a consequence of this bonding mode, the structure is a highly cross-linked, coordination polymer. 相似文献