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   98850篇
  免费   8517篇
  国内免费   4493篇
电工技术   5779篇
技术理论   12篇
综合类   6433篇
化学工业   16498篇
金属工艺   5442篇
机械仪表   6380篇
建筑科学   8426篇
矿业工程   3087篇
能源动力   3075篇
轻工业   6400篇
水利工程   1810篇
石油天然气   5648篇
武器工业   812篇
无线电   11648篇
一般工业技术   12100篇
冶金工业   4686篇
原子能技术   1072篇
自动化技术   12552篇
  2024年   390篇
  2023年   1653篇
  2022年   2966篇
  2021年   4004篇
  2020年   3098篇
  2019年   2664篇
  2018年   2898篇
  2017年   3281篇
  2016年   2919篇
  2015年   3968篇
  2014年   4872篇
  2013年   5800篇
  2012年   6481篇
  2011年   6628篇
  2010年   5870篇
  2009年   5493篇
  2008年   5431篇
  2007年   5251篇
  2006年   5357篇
  2005年   4578篇
  2004年   3257篇
  2003年   2996篇
  2002年   3065篇
  2001年   2802篇
  2000年   2403篇
  1999年   2488篇
  1998年   2061篇
  1997年   1695篇
  1996年   1616篇
  1995年   1243篇
  1994年   1146篇
  1993年   825篇
  1992年   627篇
  1991年   500篇
  1990年   369篇
  1989年   294篇
  1988年   273篇
  1987年   177篇
  1986年   124篇
  1985年   92篇
  1984年   46篇
  1983年   42篇
  1982年   45篇
  1981年   30篇
  1980年   19篇
  1979年   11篇
  1975年   1篇
  1973年   1篇
  1959年   6篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
《Frame》总第46期向读者展示了许多有意思的想法和创意的细节下面是从中摘选出来的设计和空间方案他们都运用到了我们身边很熟悉的元素,在这里“腐朽”一下化神奇了。[编者按]  相似文献   
52.
A 3-D Enlarged Cell Technique (ECT) for the Conformal FDTD Method   总被引:1,自引:0,他引:1  
In this paper, we present an enlarged cell technique (ECT) to avoid the time step reduction encountered in the conformal finite-difference time-domain (CFDTD) method due to small irregular cells truncated by metallic boundaries. We focus our efforts on the discussion of the accuracy and stability of the ECT and its comparison with other conformal methods, especially the one called the uniformly stable conformal (USC) method. We also provide a simplified ECT, which is much easier to implement. In the ECT, a stability criterion is first constructed to identify instable irregular cells, i.e., those having so small an area to cause instability. Those instable cells are then enlarged into their adjacent cells to obtain a large, stable area. Careful treatment is performed on the communication between the intruding and intruded cells in terms of electromotive force by keeping the total electromotive force conservative. This technique is verified by several 3-D numerical experiments. Results show that the ECT is second-order accurate and numerically stable at the regular Courant time step limit.  相似文献   
53.
珀金埃尔默公司新推出的Clarus 600型GC和GCMS采用全新柱温箱设计,能够缩短每次分析循环的时间,在有限的时间内可以完成更多的分析测试,从而提高分析效率和仪器的投资回报率。特别适合于需要大批量分析检测的实验室和需要测定挥发性有机物的分析工作。  相似文献   
54.
55.
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   
56.
Anumberoflanthanideternarycomplexescon tainingheterocyclicamineshavebeenreportedsince1960 [1] .Inrecentyearsmuchattentionhasbeenpaidtoquaternarycomplexesoflanthanidesbecauseofin terestingstructure ,coordinationmode ,competitionre actionandproperty[2~ 9] .ESRcane…  相似文献   
57.
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   
58.
基于嵌入式Linux的远程数据采集系统   总被引:3,自引:0,他引:3  
以嵌入式微控制器为核心,将传感器网络收集来的数据通过无线电发射机发送到远程接收机,从而实现远程数据采集.系统的优势是充分利用了短波无线链路资源,适合于工作在无人区等场合.以ARM7为控制器,功耗小,性能稳定,维护方便;通信方式采用串口通信,连接线少,实现相对简单.系统设计主要应用嵌入式μCLinux系统设计、无线电发射、调制解调器等方面的知识,文中给出了调制解调器拨号协议、系统原理和软件流程等.  相似文献   
59.
设计了一种适合在低电源电压下工作的前馈型输入级放大结构,在全摆幅的动态工作范围内,输入级跨导保持不变,采用负载电流补偿以保证增益近似恒定,输出采用前馈型AB类输结构,实现全摆幅输出。  相似文献   
60.
详细介绍了 宏蜂窝传播模 型校正的基本操作流程 结果分析及注意事项 对工程 ,人员了解和开展模型校正工作有一定的指导作用 。  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