全文获取类型
收费全文 | 29041篇 |
免费 | 1589篇 |
国内免费 | 1427篇 |
专业分类
电工技术 | 1276篇 |
技术理论 | 4篇 |
综合类 | 1862篇 |
化学工业 | 2034篇 |
金属工艺 | 791篇 |
机械仪表 | 2803篇 |
建筑科学 | 2595篇 |
矿业工程 | 453篇 |
能源动力 | 1401篇 |
轻工业 | 666篇 |
水利工程 | 524篇 |
石油天然气 | 540篇 |
武器工业 | 198篇 |
无线电 | 2242篇 |
一般工业技术 | 2373篇 |
冶金工业 | 469篇 |
原子能技术 | 269篇 |
自动化技术 | 11557篇 |
出版年
2024年 | 39篇 |
2023年 | 198篇 |
2022年 | 294篇 |
2021年 | 425篇 |
2020年 | 434篇 |
2019年 | 434篇 |
2018年 | 486篇 |
2017年 | 581篇 |
2016年 | 702篇 |
2015年 | 791篇 |
2014年 | 1450篇 |
2013年 | 1928篇 |
2012年 | 1616篇 |
2011年 | 2169篇 |
2010年 | 1554篇 |
2009年 | 1571篇 |
2008年 | 1680篇 |
2007年 | 1938篇 |
2006年 | 1872篇 |
2005年 | 1687篇 |
2004年 | 1440篇 |
2003年 | 1413篇 |
2002年 | 1251篇 |
2001年 | 890篇 |
2000年 | 754篇 |
1999年 | 718篇 |
1998年 | 649篇 |
1997年 | 509篇 |
1996年 | 514篇 |
1995年 | 361篇 |
1994年 | 316篇 |
1993年 | 262篇 |
1992年 | 227篇 |
1991年 | 190篇 |
1990年 | 98篇 |
1989年 | 116篇 |
1988年 | 90篇 |
1987年 | 67篇 |
1986年 | 36篇 |
1985年 | 66篇 |
1984年 | 55篇 |
1983年 | 57篇 |
1982年 | 33篇 |
1981年 | 22篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1975年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
101.
一种数字电视条件接收系统的设计与实现 总被引:2,自引:2,他引:0
为支撑业务的安全开展,有线数字电视系统需提供一个安全可靠的加密系统,即条件接收系统。条件接收系统是对数字电视节目进行加密,以实现有线电视运营商对用户进行管理和收费。本文介绍了一种数字电视系统中的条件接收系统实现方案。 相似文献
102.
This study focuses on numerical simulation of ductile failure in the Co binder phase of WC–Co hardmetal. The growth of edge cracks under mode I loading is considered. A computational micromechanics approach is taken where the Co binder ligaments are explicitly represented in finite element models. An embedding technique is employed. Crystal plasticity theory is used to represent plastic deformation in the Co ligaments. Crack propagation in the binder is simulated using an element removal technique based on a modified Rice and Tracey model for ductile void growth, and fracture resistance curves are generated. Parameter studies are performed for variations in microstructrual parameters such as numbers of Co ligaments ahead of the crack tip and local Co volume fraction. The importance of thermal residual stresses and finite element mesh density are also investigated. 相似文献
103.
Gülü Insel Derin Orhon Peter A Vanrolleghem 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(4):437-445
Hydrolysis mechanism plays a dominant role in the delicate balance of electron donor/electron acceptor ratios in BNR and EBPR systems as an important carbon source. In this study, the surface‐saturation‐type hydrolysis kinetics was investigated based on respirometric measurements, within the context of the theoretical and the practical identifiability of mathematical models. The identifiable parameters of a selected model were derived from respirograms. In addition, the information from the experiments was evaluated on the basis of Optimal Experimental Design (OED) methodology for different initial conditions of the batch respirometric experiment. © 2003 Society of Chemical Industry 相似文献
104.
随着广播电视技术的不断发展 ,模拟信号传输向数字信号传输的转换已成为必然。介绍模数转换系统中放大器的性能、关键技术 ,并就放大器的选择作详细探讨。 相似文献
105.
Decision support for AIDS control programmes in Eastern Africa 总被引:1,自引:1,他引:0
Steffen Fleßa 《OR Spectrum》2003,25(2):265-291
The Acquired Immune Deficiency Syndrome (AIDS) constitutes the worst hazard to health care systems in Eastern Africa. Misallocation
of scarce resources of AIDS Control Programmes will unavoidably lead to additional infections and casualties. The following
paper discusses a system dynamics model which allows to assess the impact of different interventions on a pattern population
in Eastern Africa. It becomes obvious that short- and long-term consequences of these programmes differ significantly. The
optimal allocation of resources, therefore, is highly complex and calls for decision support systems to sustain AIDS control
programmes. 相似文献
106.
针对地市级电视台的业务特点和需求,设计了基于网络的非线性编辑系统,并对系统工作流程、方案设计、拓扑结构、网络性能、系统管理要求进行了分析,提出了具体实现方法. 相似文献
107.
M. R. JOYCE K. K. LEE S. SYNGELLAKIS P. A. S. REED 《Fatigue & Fracture of Engineering Materials & Structures》2004,27(11):1025-1036
Complex multi‐phase Al–Sn–Si alloys are commonly employed in the manufacture of small automotive plain bearings. The fundamental fatigue initiation behaviour of this class of alloys is currently not well understood. A range of analytical techniques were applied to investigate preferential initiation site location and to attempt to identify critical microstructural features. It was apparent from experimental studies that points of fatigue crack initiation are associated with the Si secondary phase. Using tessellation approaches and subsequently both adaptive numerical modelling and micro‐scale finite element modelling allowed the identification of features affecting the probability that a given Si phase would initiate a fatigue crack. 相似文献
108.
非线性编辑实验室的构建与实验教学 总被引:2,自引:2,他引:0
以计算机为操作平台的非线性编辑系统广泛应用于电视节目的制作 ,学校相关专业开设非线性编辑课程也需要配置非线性编辑系统作为学生实验用机。主要介绍一种学生实验用非线性编辑系统及实验室的配置方案以及该非线性编辑系统在实验教学中的性能特征。 相似文献
109.
机群监控系统可有效的提高大型机群的可管理性和可用性。本文提出了一种基于JAVA RMI技术的机群监控系统模型,并给出其实现方法。该系统具有开发快速、可跨平台、易于扩展等特性。 相似文献
110.
The efficient, economical and often elegant transformation from a design schema to an embodied design solution containing real components is essential for the commercial success of a product. More often the ability of the designer to explore an optimum solution is severely frustrated by the analytically intensive and time-consuming aspects of embodying a concept. This paper presents a computer based system-modelling tool that is to be used by designers during the transformation of a concept to an embodied solution particularly to deal with standard components. This environment provides for the representation of conceptual schemas and subsequent embodiment from computer based component selection modules. These selection modules encompass the full range of electronic representations for standard mechanical components. The strategy for representing a mechanical system, its included components and their associated representations is discussed. The process of constructing a system model, specifying the desired performance characteristics and system resolution are also described. 相似文献