全文获取类型
收费全文 | 112718篇 |
免费 | 15513篇 |
国内免费 | 10377篇 |
专业分类
电工技术 | 20433篇 |
技术理论 | 11篇 |
综合类 | 12215篇 |
化学工业 | 4385篇 |
金属工艺 | 2080篇 |
机械仪表 | 5570篇 |
建筑科学 | 4384篇 |
矿业工程 | 2635篇 |
能源动力 | 4866篇 |
轻工业 | 1539篇 |
水利工程 | 2397篇 |
石油天然气 | 2539篇 |
武器工业 | 1029篇 |
无线电 | 21849篇 |
一般工业技术 | 4970篇 |
冶金工业 | 1934篇 |
原子能技术 | 353篇 |
自动化技术 | 45419篇 |
出版年
2024年 | 949篇 |
2023年 | 2530篇 |
2022年 | 4682篇 |
2021年 | 5173篇 |
2020年 | 5224篇 |
2019年 | 3837篇 |
2018年 | 3188篇 |
2017年 | 3835篇 |
2016年 | 3961篇 |
2015年 | 4484篇 |
2014年 | 7641篇 |
2013年 | 6661篇 |
2012年 | 8580篇 |
2011年 | 9039篇 |
2010年 | 6866篇 |
2009年 | 7257篇 |
2008年 | 7351篇 |
2007年 | 8103篇 |
2006年 | 6783篇 |
2005年 | 6020篇 |
2004年 | 4985篇 |
2003年 | 4372篇 |
2002年 | 3454篇 |
2001年 | 2981篇 |
2000年 | 2404篇 |
1999年 | 1950篇 |
1998年 | 1407篇 |
1997年 | 1158篇 |
1996年 | 943篇 |
1995年 | 734篇 |
1994年 | 563篇 |
1993年 | 389篇 |
1992年 | 259篇 |
1991年 | 186篇 |
1990年 | 144篇 |
1989年 | 120篇 |
1988年 | 71篇 |
1987年 | 44篇 |
1986年 | 42篇 |
1985年 | 54篇 |
1984年 | 38篇 |
1983年 | 32篇 |
1982年 | 36篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1959年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
在CATV系统网络工程设计中,技术指标的分配产关键问题。本文介绍了石家庄市在系统设计时采用的符合实际的设计程序,并对系统前端,传输及用户网各部分技术指标的确定,计算与分配方法,指标的核算等作了较详细地阐述,以供同行参考。 相似文献
102.
新建微波干线电路采用高质量的数字微波设备是广电部科技工作会议的精神之一。本文介绍了江苏苏南数字微波线路,并从方案确定、技术实现、设备选型等方面进行分析比较,从而得到一个合理的整体方案。本文还着重阐述了数字传输的关键设备-编码器的现状与发展趋势,提出广播电视专用网多功能应用的设想。 相似文献
103.
104.
This paper analyses the collaborative design ofa high-technology product, a neuromagnetometerused in the analysis of the activity of thehuman cortex. The producer, Neuromag Company istrying to transform the device from a basicresearch instrument into a means of clinicalpractice. This transition is analyzed as asimultaneous evolution of the product,producer-user network and user activities. Thenetwork is analyzed as a network of activitysystems. Each activity has a historicallyformed object and a motive of its own, as wellas a system of cultural means and expertise. Weuse these to explain and understand theinterests and points of view of the actors inrelation to the product and the contradictionsof the producer-user network. It is suggestedthat the emerging user needs of collectiveactors must be analyzed at three levels. At thefirst level, the use value of the product, itscapacity of solving the vital problems andchallenges of developing user activities, ischaracterized. The second-level analysisconcerns the creation and development of thenecessary complementary tools and services thatmake the implementation and use of the productpossible. This task presupposes collaborationbetween several communities of the innovationnetwork. The third level is the situatedpractical use of the product. In ourexperience, it is advantageous that researcherscontribute with their data to a dialogue inwhich the user needs are articulated. 相似文献
105.
人工神经网络及其应用 总被引:8,自引:2,他引:6
本文首首先介绍了人工神经网络的源泉一体神经网络的主要基本内容,然后简要论述了人工神经网络的主要内容,进程和问题,人工神经网的应用。 相似文献
106.
A Method of Combined SHPB Technique and BP Neural Network to Study Impact Response of Materials 总被引:2,自引:0,他引:2
Abstract: A new method combining the split Hopkinson pressure bar (SHPB) technique with the back-propagation (BP) neural network program is proposed. By this method, the treated strain wave signals become smooth with less noises induced by the transverse inertia. Moreover, the dynamic rate-dependent constitutive behaviour of materials can be identified, without any pre-assumption of a constitutive model. It is found that by taking the experimentally measured data of strain, strain rate and time as 'input' and the corresponding data of stress as 'output' of the BP neural network, the dynamic constitutive behaviour with internal damage or phase transformation evolution is easy to be identified, where the time could represent either the internal damage evolution or phase transformation process accompanied with the deformation process. It is emphasised that the data learnt by the BP neural network must include both loading and unloading processes, if the whole loading and unloading response is to be correctly predicted. The comparisons between the predictions and experimental results are in good agreement for both polyamide (PA) polymer (as an example of nonlinear viscoelastic materials) and Ti–Ni alloy (as an example of superelastic materials with stress-induced phase transformation). 相似文献
107.
108.
本文设计了一种应用于油气藏永久性实时动态监测系统。该系统用光纤Bragg光栅(FBG)传感器作为井下永久性传感器,测量目的层的温度、压力等参数的模拟信号;在井口建立数据采集处理系统,将模拟信号解调成数字信号;通过GPRS无线移动通信网络传输到监测中心的数据库服务器上,并以Web形式发布到Internet网络上,同时提供移动用户浏览接口,且当数据异常时可以发送报警短消息。该系统实现了油气藏的远程实时动态监测,可以为油藏管理人员和技术人员及时、准确地做出决策提供可靠依据。 相似文献
109.
110.
Eiichi Haginomori Kenji Yoshimura Shunichi Kobayashi Sadanori Kaneko Takeshi Yokota Masayuki Ishikawa 《Electrical Engineering in Japan》1994,114(4):50-61
To cope with the high rate of increase of power demand in the main industrialized districts in Japan, 550-kV transmission systems covering the districts have been reinforced, with most of the main power plants connected directly to these systems. Through 550-/300-kV substations, the majority of power to the districts is supplied by 300-kV systems. To limit the excess short-circuit capacity in the 300-kV systems, they tend to be reconstructed as so-called radial networks. In radial networks with high short-circuit capacity and relatively small number of transmission lines connected to the substation busbars, the rate of rise of TRV can be far higher than standard value. This paper analyzes the transient recovery voltages (TRV) in such extra-high-voltage radial networks in Japan, together with the relevant stresses to circuit-breakers during fault clearings. Future system conditions have also been introduced. As the typical rate of rise of the TRV values, more than twice that of today's standard ones are probable. 相似文献