全文获取类型
收费全文 | 89478篇 |
免费 | 5079篇 |
国内免费 | 1164篇 |
专业分类
电工技术 | 2306篇 |
技术理论 | 4篇 |
综合类 | 1644篇 |
化学工业 | 16342篇 |
金属工艺 | 3571篇 |
机械仪表 | 4702篇 |
建筑科学 | 2880篇 |
矿业工程 | 801篇 |
能源动力 | 3282篇 |
轻工业 | 6186篇 |
水利工程 | 688篇 |
石油天然气 | 1207篇 |
武器工业 | 147篇 |
无线电 | 15058篇 |
一般工业技术 | 15887篇 |
冶金工业 | 8336篇 |
原子能技术 | 1000篇 |
自动化技术 | 11680篇 |
出版年
2023年 | 919篇 |
2022年 | 1396篇 |
2021年 | 2542篇 |
2020年 | 1874篇 |
2019年 | 1776篇 |
2018年 | 2186篇 |
2017年 | 2211篇 |
2016年 | 2472篇 |
2015年 | 2328篇 |
2014年 | 3382篇 |
2013年 | 5520篇 |
2012年 | 5080篇 |
2011年 | 6131篇 |
2010年 | 4739篇 |
2009年 | 4943篇 |
2008年 | 4704篇 |
2007年 | 4114篇 |
2006年 | 3741篇 |
2005年 | 3138篇 |
2004年 | 2886篇 |
2003年 | 2860篇 |
2002年 | 2998篇 |
2001年 | 2435篇 |
2000年 | 1990篇 |
1999年 | 1856篇 |
1998年 | 3099篇 |
1997年 | 2064篇 |
1996年 | 1745篇 |
1995年 | 1403篇 |
1994年 | 1104篇 |
1993年 | 994篇 |
1992年 | 734篇 |
1991年 | 706篇 |
1990年 | 635篇 |
1989年 | 598篇 |
1988年 | 488篇 |
1987年 | 419篇 |
1986年 | 375篇 |
1985年 | 361篇 |
1984年 | 305篇 |
1983年 | 225篇 |
1982年 | 222篇 |
1981年 | 188篇 |
1980年 | 206篇 |
1979年 | 150篇 |
1978年 | 153篇 |
1977年 | 179篇 |
1976年 | 234篇 |
1975年 | 121篇 |
1974年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
991.
An adaptive fuzzy decentralized backstepping output-feedback control approach is proposed for a class of nonlinear large-scale systems with completely unknown functions,the interconnections mismatched in control inputs,and without the measurements of the states.Fuzzy logic systems are employed to approximate the unknown nonlinear functions,and an adaptive high-gain observer is developed to estimate the unmeasured states.Using the designed high-gain observer,and combining the fuzzy adaptive control theory with backstepping approach,an adaptive fuzzy decentralized backstepping output-feedback control scheme is developed.It is proved that the proposed control approach can guarantee that all the signals of the closed-loop system are semi-globally uniformly ultimately bounded(SUUB),and that the observer errors and the tracking errors converge to a small neighborhood of the origin by appropriate choice of the design parameters.Finally,a simulation example is provided to show the eectiveness of the proposed approach. 相似文献
992.
进行IT投资风险预警的基础是对IT投资风险域进行分析;文章提出了基于IT投资目标、信息化生命周期以及企业架构的IT投资风险域的三维框架,并引入贝叶斯网络的原理建立预警机制。最后,在此基础上进行了IT投资风险预警的案例分析。 相似文献
993.
994.
We propose a model structure with a double-layer hidden Markov model (HMM) to recognise driving intention and predict driving behaviour. The upper-layer multi-dimensional discrete HMM (MDHMM) in the double-layer HMM represents driving intention in a combined working case, constructed according to the driving behaviours in certain single working cases in the lower-layer multi-dimensional Gaussian HMM (MGHMM). The driving behaviours are recognised by manoeuvring the signals of the driver and vehicle state information, and the recognised results are sent to the upper-layer HMM to recognise driving intentions. Also, driving behaviours in the near future are predicted using the likelihood-maximum method. A real-time driving simulator test on the combined working cases showed that the double-layer HMM can recognise driving intention and predict driving behaviour accurately and efficiently. As a result, the model provides the basis for pre-warning and intervention of danger and improving comfort performance. 相似文献
995.
Wu Li Yann-Hang Lee Wei-Tek Tsai Jingjing Xu Young-Sung Son Jun-Hee Park Kyung-Duk Moon 《Service Oriented Computing and Applications》2012,6(1):65-79
A smart home usually has a variety of devices or home appliance, instead of designing software for a specific home, this paper
proposes a service-oriented framework with a set of ontology systems to support service and device publishing, discovery of
devices and their services, composition of control software using existing control services that wrap devices, deployment,
and execution of the composed service in an computing environment, monitoring the execution, and recovery from device failure.
The ontology systems specify semantic information about devices, services, and workflows used in various smart home, and users
can compose and recompose services for their specific needs. New devices, workflows, and services can be added into ontology.
Most of the steps in this process can be automated including code generation. For example, service composition will be carried
out in three steps: abstract workflow design, function construction, and device discovery, and different codes can be generated
for different computing platforms such as Java and Open Services Gateway initiative environments. In this way, a variety of
smart home can be constructed rapidly using the framework by discovery and composition using existing services and workflows.
This paper illustrates this framework using a media control example to illustrate the ontology, discovery, composition, deployment,
execution, monitoring, and recovery. 相似文献
996.
Guanling Lee Sheng-Lung Peng Yi-Chun Chen Jia-Sin Huang 《Peer-to-Peer Networking and Applications》2012,5(4):340-349
Accompanying the growth of the Internet, computers throughout the world can connect to each other and exchange information, increasing the convenience and efficiency of information-based work. The advent of data-sharing applications, such as Napster and Gnutella, has made peer-to-peer (P2P) systems popular for widespread exchange of resources and voluminous information between millions of users. In recent years, research issues associated with P2P systems have been discussed widely. To resolve the file-availability problem and improve the workload, a method called the Distributed Hash Table (DHT) has been proposed. However, DHT-based systems in structured architectures cannot support efficient queries, such as a similarity query, range query, and partial-match query, due to the characteristics of the hash function. This study presents a novel scheme that supports filename partial-matches in structured P2P systems. The proposed approach supports complex queries and guarantees result quality. Experimental results demonstrate the effectiveness of the proposed approach. 相似文献
997.
998.
999.
1000.
Alexander Gatch Dimitry Gorsky Zy Biesinger Eric Bruestle Kelley Lee Curt Karboski Meredith L. Bartron Tyler Wagner 《Journal of Great Lakes research》2021,47(2):486-493
Restoration of a wild-produced lake trout Salvelinus namaycush population in Lake Ontario has not been successful despite the adult population often meeting or exceeding restoration targets. Lack of high-quality spawning habitat in Lake Ontario is suggested as one impediment to recruitment of wild lake trout, although the quantity and location of spawning habitat is poorly understood. If high-quality spawning habitat is limited in Lake Ontario, lake trout may be using uncommon spawning locations such as rivers. Anecdotal angler accounts point to the Niagara River as a lake trout spawning location. To better understand the potential of the Niagara River as a spawning location, egg and juvenile fish collections were conducted 12–14 river kilometers from the mouth of the Niagara River from 2010 to 2012; and mature female lake trout with surgically implanted acoustic tags were monitored from 2015 to 2019. Genetic analyses confirmed 60% of collected eggs and 93% of collected post-hatch juvenile fish in the Niagara River were lake trout. Tagged female lake trout returned to the Niagara River over consecutive years during the spawning season. The short duration of lake trout presence in the river (mean = 56 days/year) suggests female lake trout use the Niagara River primarily for spawning. Diversity in spawning locations may provide lake trout population’s resilience against environmental variability through a portfolio effect. Improved identification of riverine spawning locations, including their overall contribution to wild recruitment, may be a useful tool for managers to restore a wild-produced population of lake trout in Lake Ontario. 相似文献