全文获取类型
收费全文 | 111035篇 |
免费 | 5865篇 |
国内免费 | 3527篇 |
专业分类
电工技术 | 4134篇 |
技术理论 | 10篇 |
综合类 | 4120篇 |
化学工业 | 18489篇 |
金属工艺 | 6770篇 |
机械仪表 | 5655篇 |
建筑科学 | 6791篇 |
矿业工程 | 2154篇 |
能源动力 | 3453篇 |
轻工业 | 6479篇 |
水利工程 | 1454篇 |
石油天然气 | 5734篇 |
武器工业 | 534篇 |
无线电 | 12098篇 |
一般工业技术 | 19223篇 |
冶金工业 | 10693篇 |
原子能技术 | 1559篇 |
自动化技术 | 11077篇 |
出版年
2023年 | 1192篇 |
2022年 | 2065篇 |
2021年 | 2846篇 |
2020年 | 2265篇 |
2019年 | 2117篇 |
2018年 | 2570篇 |
2017年 | 2856篇 |
2016年 | 2719篇 |
2015年 | 3157篇 |
2014年 | 4033篇 |
2013年 | 6204篇 |
2012年 | 5641篇 |
2011年 | 6343篇 |
2010年 | 5370篇 |
2009年 | 5455篇 |
2008年 | 5221篇 |
2007年 | 5358篇 |
2006年 | 5178篇 |
2005年 | 4521篇 |
2004年 | 3431篇 |
2003年 | 3051篇 |
2002年 | 2972篇 |
2001年 | 2842篇 |
2000年 | 2682篇 |
1999年 | 3004篇 |
1998年 | 3877篇 |
1997年 | 3110篇 |
1996年 | 2828篇 |
1995年 | 2046篇 |
1994年 | 1770篇 |
1993年 | 1477篇 |
1992年 | 1135篇 |
1991年 | 1007篇 |
1990年 | 844篇 |
1989年 | 737篇 |
1988年 | 602篇 |
1987年 | 547篇 |
1986年 | 468篇 |
1985年 | 457篇 |
1984年 | 342篇 |
1983年 | 336篇 |
1982年 | 341篇 |
1981年 | 318篇 |
1980年 | 363篇 |
1979年 | 346篇 |
1978年 | 295篇 |
1977年 | 415篇 |
1976年 | 630篇 |
1975年 | 308篇 |
1973年 | 311篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
Ya. Z. Gaft 《Chemical and Petroleum Engineering》2006,42(9-10):576-581
Characteristics and design diagrams of pump shaft seals, their reliability and leak-tightness indices, and comparative analysis of cost of leak-tightening are given. 相似文献
142.
ZnO-based varistor samples were prepared by the direct mixing of the constituent phases (DMCP) and sintering at 1100 °C for 2 h. The influence of the starting powder mixture's composition – the amounts of the pre-reacted varistor compounds and their composition – and its preparation, either with or without mechano-chemical activation (MCA), on the microstructure, phase composition and electrical characteristics of the varistor samples was studied. It showed that MCA improved the density and microstructural homogeneity of the varistor samples. MCA strongly affected the grain growth: it enhanced the nucleation of inversion boundaries (IBs) in the ZnO grains and the IBs-induced grain-growth mechanism resulted in uniform grain growth and hence a microstructure with smaller ZnO grains and a narrower grain size distribution. The final phase composition of the samples prepared by the DMCP method mainly depended on the presence of varistor dopants that can prevent the formation of the pyrochlore phase, especially Cr2O3, while MCA can affect it mostly by providing a homogeneous distribution of those dopants. The DMCP varistor samples prepared with MCA had much better current–voltage characteristics than the samples of the same composition prepared from unactivated powders. 相似文献
143.
144.
Software plays an increasingly important role in modern safety-critical systems. Although, research has been done to integrate software into the classical probabilistic risk assessment (PRA) framework, current PRA practice overwhelmingly neglects the contribution of software to system risk. Dynamic probabilistic risk assessment (DPRA) is considered to be the next generation of PRA techniques. DPRA is a set of methods and techniques in which simulation models that represent the behavior of the elements of a system are exercised in order to identify risks and vulnerabilities of the system. The fact remains, however, that modeling software for use in the DPRA framework is also quite complex and very little has been done to address the question directly and comprehensively. This paper develops a methodology to integrate software contributions in the DPRA environment. The framework includes a software representation, and an approach to incorporate the software representation into the DPRA environment SimPRA. The software representation is based on multi-level objects and the paper also proposes a framework to simulate the multi-level objects in the simulation-based DPRA environment. This is a new methodology to address the state explosion problem in the DPRA environment. This study is the first systematic effort to integrate software risk contributions into DPRA environments. 相似文献
145.
The purpose of this study is to apply continuum damage mechanics – introduced through the concept of fabric tensors – to composite materials within the framework of the theory of elasticity. A directional data model of damage mechanics for composite materials will be developed using fabric tensors. The introduction of fabric tensors into the analysis of damage of composite materials will allow for an enhanced and better understood physical meaning of damage. The micromechanical approach will be used here to relate the damage effect through fabric tensors to the behavior of composite materials. In this approach, damage mechanics is introduced separately to the constituents of the composite material through different constituents’ damage effect tensors. The damaged properties of the composite system as a whole can then be obtained by proper homogenization of the damaged properties of the constituents.
The derivation of a generalized formulation of damage evolution will be shown here in a mathematically consistent manner that is based on sound thermodynamic principles. Numerical examples will be presented to show applicability. In addition, damage evolution for the one-dimensional tension case is also illustrated. 相似文献
146.
Anumberoflanthanideternarycomplexescon tainingheterocyclicamineshavebeenreportedsince1960 [1] .Inrecentyearsmuchattentionhasbeenpaidtoquaternarycomplexesoflanthanidesbecauseofin terestingstructure ,coordinationmode ,competitionre actionandproperty[2~ 9] .ESRcane… 相似文献
147.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献
148.
149.
150.
国内3G网络共享问题之研究 总被引:2,自引:0,他引:2
随着国内3G时代的来临,3G网络共享问题越来越受到人们的关注。本文结合国内移动通信的现状,着重分析了3G网络共享的模式及经济效益,论述了3G网络共享的相应策略。 相似文献