全文获取类型
收费全文 | 2640篇 |
免费 | 311篇 |
国内免费 | 289篇 |
专业分类
化学 | 1434篇 |
晶体学 | 20篇 |
力学 | 88篇 |
综合类 | 5篇 |
数学 | 342篇 |
物理学 | 669篇 |
无线电 | 682篇 |
出版年
2024年 | 5篇 |
2023年 | 63篇 |
2022年 | 72篇 |
2021年 | 105篇 |
2020年 | 124篇 |
2019年 | 97篇 |
2018年 | 77篇 |
2017年 | 89篇 |
2016年 | 111篇 |
2015年 | 117篇 |
2014年 | 122篇 |
2013年 | 179篇 |
2012年 | 186篇 |
2011年 | 204篇 |
2010年 | 131篇 |
2009年 | 145篇 |
2008年 | 179篇 |
2007年 | 144篇 |
2006年 | 128篇 |
2005年 | 132篇 |
2004年 | 67篇 |
2003年 | 57篇 |
2002年 | 57篇 |
2001年 | 64篇 |
2000年 | 60篇 |
1999年 | 52篇 |
1998年 | 40篇 |
1997年 | 41篇 |
1996年 | 50篇 |
1995年 | 48篇 |
1994年 | 45篇 |
1993年 | 35篇 |
1992年 | 29篇 |
1991年 | 39篇 |
1990年 | 26篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1968年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有3240条查询结果,搜索用时 442 毫秒
21.
Inexact Newton methods for the nonlinear complementarity problem 总被引:2,自引:0,他引:2
Jong-Shi Pang 《Mathematical Programming》1986,36(1):54-71
An exact Newton method for solving a nonlinear complementarity problem consists of solving a sequence of linear complementarity
subproblems. For problems of large size, solving the subproblems exactly can be very expensive. In this paper we study inexact
Newton methods for solving the nonlinear, complementarity problem. In such an inexact method, the subproblems are solved only
up to a certain degree of accuracy. The necessary accuracies that are needed to preserve the nice features of the exact Newton
method are established and analyzed. We also discuss some extensions as well as an application.
This research was based on work supported by the National Science Foundation under grant ECS-8407240. 相似文献
22.
Introduction and Applications of a Generalized Intermediate Entangled State Representation 下载免费PDF全文
We introduce a generalized intermediate entangled state representation |β〉Λ to study the energy spectrum of an electron in a uniform magnetic field and a harmonic potential through algebraic calculatiOn. We find that the degeneracy of the energy levels is disappeared due to the existence of the additional potential. We make it clear that the eigenfunction is just the expression of eigenvector, defined in n Fock space, in |β〉Λ representation. 相似文献
23.
Excessive intermetallic compound (IMC) growth in solder joints will significantly decrease the reliability of the joints.
IMC growth is known to be influenced by numerous factors during the component fabrication process and in service. It is reported
that, other than temperature and holding time, stress can also influence the IMC growth behavior. However, no existing method
can be used to study the effect of stress state on IMC growth in a controlled manner. This paper presents a novel method to
study the effect of stress on interfacial IMC growth between Sn-Ag-Cu solder and a Cu substrate coated with electroless Ni
immersion Au (ENIG). A C-ring was used and in-plane bending induced tensile and compressive stresses were applied by tightening
the C-ring. Results revealed that in-plane compressive stress led to faster IMC growth as compared with in-plane tensile stress. 相似文献
24.
A new nondestructive testing (NDT) technique, which is based on Electronic Speckle Pattern Interferometry (ESPI) and digital image processing with quasi phase shift and gradient technique, is presented. A simple phase reduction algorithm is developed, which replaced an accurate phase shifter. Compared with other phase shift techniques, this method is insensitive to environmental vibration and air disturbance, has visible procedures and results allows the object to move slowly during the inspection procedure, does not need phase unwrapping, and has a quick image processing speed. As an application, this NDT technique is used to detect defects in composite materials and the resulting deformation phase gradient image shows a better visual effect than normal ESPI. 相似文献
25.
26.
CuO—ZnO/Al2O3—TiO2催化剂中TiO2的结构和电子效应 总被引:6,自引:0,他引:6
采用XPS,XRD,TPR,TPD和指标反应等方法研究了TiO_2在负载型CuO-ZnO/Al_2O_3-TiO_2催化剂中所起的作用.发现TiO_2起双重作用,即结构效应和电子效应,TiO_2的结构效应主要表现为它改善了CuO在载体上的分布.TiO_2的电子效应表现为它对Cu~0具有吸电子的作用,从而削弱了Cu和S之间的吸附力,使S容易脱除.另外,部分还原形成的Ti~(3+)具有促进CuS中的Cu~(2+)还原为Cu~0的能力,TiO_2的上述效应的综合结果使催化剂的抗硫中毒性能大大增强. 相似文献
27.
用TEM研究了(NR SBR)/PE共混体系经动、静态硫化后的形态结构及其与力学性能的关系。未硫化和静态硫化体系的形态结构与其组成有关,均以含量大的组份为连续相;对动态硫化体系,当(NR=SBR)/PE<70/30时,均以PE为连续相,其性能主要依赖于构成连续相组份的性质。 动态硫化体系的T_g值低于静态体系,随PE组份含量的增加变化不大,而静态硫化体系的T_g值则随PE含量增加向高温方向迁移。用DSC测得动态硫化体系的结晶度比静态体系的大。前者的应力-应变性能也低于后者。 相似文献
28.
29.
30.