首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3737篇
  免费   464篇
  国内免费   259篇
化学   298篇
晶体学   7篇
力学   492篇
综合类   42篇
数学   986篇
物理学   604篇
无线电   2031篇
  2024年   31篇
  2023年   73篇
  2022年   111篇
  2021年   139篇
  2020年   147篇
  2019年   111篇
  2018年   86篇
  2017年   132篇
  2016年   148篇
  2015年   151篇
  2014年   249篇
  2013年   288篇
  2012年   249篇
  2011年   264篇
  2010年   196篇
  2009年   204篇
  2008年   227篇
  2007年   239篇
  2006年   209篇
  2005年   163篇
  2004年   149篇
  2003年   120篇
  2002年   104篇
  2001年   116篇
  2000年   87篇
  1999年   61篇
  1998年   71篇
  1997年   46篇
  1996年   55篇
  1995年   42篇
  1994年   28篇
  1993年   31篇
  1992年   31篇
  1991年   13篇
  1990年   12篇
  1989年   7篇
  1988年   8篇
  1987年   5篇
  1986年   7篇
  1985年   4篇
  1984年   7篇
  1982年   9篇
  1980年   4篇
  1979年   2篇
  1978年   4篇
  1976年   3篇
  1975年   2篇
  1973年   5篇
  1970年   2篇
  1969年   2篇
排序方式: 共有4460条查询结果,搜索用时 9 毫秒
101.
在已有的众多准等熵加载技术中,磁驱动准等熵加载技术具有准等熵程度高、压力范围大、实验材料种类多、效费比高等特点。利用中物院流体物理研究所建成的磁驱动准等熵压缩和高速飞片实验装置CQ-1.5(最高加载压力为50GPa),成功开展了45钢的准等熵压缩实验,对装置的主要参数进行了介绍;利用激光干涉测试系统DPS获得了45钢飞片的自由面速度历史,通过反积分处理给出了材料准等熵压缩的p-V关系。通过分析实验数据,获得了45钢3种形式的等熵方程的参数。实验获得的最高等熵压力为47.5GPa。  相似文献   
102.
综合自动测试系统集成策略   总被引:5,自引:0,他引:5  
从应用需求的角度来描述现代军用自动测试系统的组成与发展 ,并对自动测试系统的集成过程加以描述 ,从而讨论现阶段我国军用综合自动测试系统集成的策略。  相似文献   
103.
本文描述了ESD的基本概念,介绍了电力电子集成电路的ESD保护方法和技术。最后,指出了在版图设计中应注意的一些问题。  相似文献   
104.
史波  王红  马学强 《信息技术》2007,31(4):92-94
在开放的Internet平台上,通过对各节点上的服务进行集成以构建新应用系统成为一种重要的软件开发方法。其中,服务集成技术是关键技术之一。传统的集成构架对Internet这个开放平台上的服务集成的支持存在不足,主要表现在对可组合、可重用、可配置及可移动的支持不够。现利用Agent的移动性和封装性,采用基于移动Agent技术的集成方法,提出了一个统一的Agent集成框架及其支撑技术,有效支持了服务的封装和运行。  相似文献   
105.
Design and fabrication of Schottky barrier diodes (SBD) with a commercial standard 0.35μm CMOS process are described.In order to reduce the series resistor of Schottky contact,interdigitating the fingers of schottky diode layout is adopted.The I-V,C-V,and S parameter are measured.The parameters of realized SBD such as the saturation current,breakdown voltage,and the Schottky barrier height are given.The SPICE simulation model of the realized SBDs is given.  相似文献   
106.
Extending fixed‐grid time integration schemes for unsteady CFD applications to moving grids, while formally preserving their numerical stability and time accuracy properties, is a nontrivial task. A general computational framework for constructing stability‐preserving ALE extensions of Eulerian multistep time integration schemes can be found in the literature. A complementary framework for designing accuracy‐preserving ALE extensions of such schemes is also available. However, the application of neither of these two computational frameworks to a multistage method such as a Runge–Kutta (RK) scheme is straightforward. Yet, the RK methods are an important family of explicit and implicit schemes for the approximation of solutions of ordinary differential equations in general and a popular one in CFD applications. This paper presents a methodology for filling this gap. It also applies it to the design of ALE extensions of fixed‐grid explicit and implicit second‐order time‐accurate RK (RK2) methods. To this end, it presents the discrete geometric conservation law associated with ALE RK2 schemes and a method for enforcing it. It also proves, in the context of the nonlinear scalar conservation law, that satisfying this discrete geometric conservation law is a necessary and sufficient condition for a proposed ALE extension of an RK2 scheme to preserve on moving grids the nonlinear stability properties of its fixed‐grid counterpart. All theoretical findings reported in this paper are illustrated with the ALE solution of inviscid and viscous unsteady, nonlinear flow problems associated with vibrations of the AGARD Wing 445.6. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
107.
《Microelectronics Reliability》2014,54(9-10):1953-1958
The effects of silicon etching using the Bosch process and LPCVD oxide deposition on the performance of open TSVs are analyzed through simulation. Using an in-house process simulator, a structure is generated which contains scalloped sidewalls as a result of the Bosch etch process. During the LPCVD deposition step, oxide is expected to be thinner at the trench bottom when compared to the top; however, additional localized thinning is observed around each scallop. The scalloped structure is compared to a structure where the etching step is not performed, but rather a flat trench profile is assumed. Both structures are imported into a finite element tool in order to analyze the effects of processing on device performance. The scalloped structure is shown to have an increased resistance and capacitance when compared to the flat TSV. Additionally, the scalloped TSV does not perform as well at high frequencies, where the signal loss is shown to increase. However, the scallops allow the TSV to respond better to an applied stress. This is due to the scallops’ enhanced range of motion and displacement, meaning they can compensate for the stress along the entire sidewall and not only on the TSV top, as in the flat structure.  相似文献   
108.
郭珍军  徐柳 《电信科学》2012,28(3):122-125
系统阐述了我国两化融合的本质、发展规律、阶段特征、实现途径,总结了两化融合在我国的实践和发展,最后提出了若干政策建议。通过理论研究和总结,为践行具有中国特色的两化融合之路提供借鉴和参考。  相似文献   
109.
The approach for the integration over a region covered by zero‐flux surface is described. This approach based on the surface triangulation technique is efficiently realized in a newly developed program TWOE . The elaborated method is tested on several atomic properties including the source function. TWOE results are compared with those produced by using well‐known existing programs. Absolute errors in computed atomic properties are shown to range usually from 10?6 to 10?5 au. The demonstrative examples prove that present realization has perfect convergence of atomic properties with increasing size of angular grid and allows to obtain highly accurate data even in the most difficult cases. It is believed that the developed program can be bridgehead that allows to implement atomic partitioning of any desired molecular property with high accuracy. © 2012 Wiley Periodicals, Inc.  相似文献   
110.
《Microelectronics Reliability》2014,54(9-10):1959-1962
Managing the emerging internal mechanical stress in chips, particularly if they are 3D stacked, is a key task to maintain performance and reliability of microelectronic products. Hence, a strong need of a physics-based simulation methodology emerges. This physics-based simulation, however, requires material parameters with high accuracy. A full-chip analysis can then be performed, balancing the need for local resolution and computing time. The key for an efficient simulation of a 3D stacked IC is a comprehensive database with material properties for multiple scales of the affected materials. Therefore, effective “composite-type” material data for several regions of interest are needed. Advanced techniques to measure FEA- and design-relevant properties such as adhesion properties and effective CTE values are presented.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号