全文获取类型
收费全文 | 67714篇 |
免费 | 4292篇 |
国内免费 | 1671篇 |
专业分类
电工技术 | 2297篇 |
技术理论 | 2篇 |
综合类 | 2639篇 |
化学工业 | 12397篇 |
金属工艺 | 1977篇 |
机械仪表 | 2418篇 |
建筑科学 | 4408篇 |
矿业工程 | 740篇 |
能源动力 | 1655篇 |
轻工业 | 6347篇 |
水利工程 | 957篇 |
石油天然气 | 1470篇 |
武器工业 | 243篇 |
无线电 | 6974篇 |
一般工业技术 | 9883篇 |
冶金工业 | 7513篇 |
原子能技术 | 580篇 |
自动化技术 | 11177篇 |
出版年
2024年 | 167篇 |
2023年 | 727篇 |
2022年 | 1360篇 |
2021年 | 1862篇 |
2020年 | 1414篇 |
2019年 | 1306篇 |
2018年 | 1615篇 |
2017年 | 1642篇 |
2016年 | 1834篇 |
2015年 | 2046篇 |
2014年 | 2707篇 |
2013年 | 4063篇 |
2012年 | 4081篇 |
2011年 | 4694篇 |
2010年 | 3918篇 |
2009年 | 3769篇 |
2008年 | 4176篇 |
2007年 | 3997篇 |
2006年 | 3501篇 |
2005年 | 2992篇 |
2004年 | 2399篇 |
2003年 | 2021篇 |
2002年 | 1962篇 |
2001年 | 1436篇 |
2000年 | 1317篇 |
1999年 | 1197篇 |
1998年 | 1347篇 |
1997年 | 1002篇 |
1996年 | 901篇 |
1995年 | 818篇 |
1994年 | 693篇 |
1993年 | 691篇 |
1992年 | 556篇 |
1991年 | 376篇 |
1990年 | 440篇 |
1989年 | 429篇 |
1988年 | 353篇 |
1987年 | 361篇 |
1986年 | 340篇 |
1985年 | 380篇 |
1984年 | 299篇 |
1983年 | 284篇 |
1982年 | 283篇 |
1981年 | 249篇 |
1980年 | 210篇 |
1979年 | 209篇 |
1978年 | 186篇 |
1977年 | 161篇 |
1976年 | 176篇 |
1975年 | 153篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
The paper deals with a physical model for the calculation of the strip temperature in a hot rolling mill. Beside the heat transfer from the strip to the environment in the different mill sections a sub‐model for the material properties of steel including phase transitions is introduced. For the application in a process automation system an online adaptation of the model to the current state of the mill is indispensable. The adaptation is explained in detail. 相似文献
62.
63.
Analysis and synthesis of on-chip spiral inductors 总被引:3,自引:0,他引:3
This paper presents a physically based compact model for estimating high-frequency performance of spiral inductors. The model accurately accounts for skin and proximity effects in the metal conductors as well as eddy current losses in the substrate. The model shows excellent agreement with measured data mostly within 10% across a variety of inductor geometries and substrate dopings up to 20 GHz. A web-based spiral inductor synthesis and analysis tool COILS, which makes use of the compact models, is presented. An optimization algorithm using binary searches speeds up the synthesis of inductor designs. 相似文献
64.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
65.
A sensor-driven control model and a minimum effort control algorithm in terms of time and energy expended during the execution of a movement strategy are described and validated for a multijointed cooperating robotic manipulator. Considering smooth, human-like (anthropomorphic) movements, using joint motion profiles achievable in real time as well as sensory information from all joints, and evaluating the total work expended by each manipulator joint during the execution of a movement strategy, a minimum effort motion trajectory is synthesized to precisely and efficiently position the robotic arm end-effector. This sensor-based approach significantly reduces the computational requirements for such cooperative motion. The minimum effort control algorithm generates several human-like arm movement strategies and selects the best strategy on the basis of expendable effort. The algorithm has an inherent basis to deal with obstacles in an efficient way. Detailed examples are described from the simulation studies. © 1994 John Wiley & Sons, Inc. 相似文献
66.
Performance model of interactive video-on-demand systems 总被引:5,自引:0,他引:5
Li V.O.K. Wanjiun Liao Xiaoxin Qiu Wong E.W.M. 《Selected Areas in Communications, IEEE Journal on》1996,14(6):1099-1109
An interactive video-on-demand (VoD) system allows users to access video services, such as movies, electronic encyclopedia, interactive games, and educational videos from video servers on a broadband network. This paper develops a performance evaluation tool for the system design. In particular, a user activity model is developed to describe the usage of system resources, i.e., network bandwidth and video server usage, by a user as it interacts with the service. In addition, we allow batching of user requests, and the effect of such batching is captured in a batching model. Our proposed queueing model integrates both the user activity and the batching model. This model can be used to determine the requirements of network bandwidth and video server and, hence, the trade-off in communication and storage costs for different system resource configurations 相似文献
67.
Multimode parameter extraction for multiconductor transmissionlines via single-pass FDTD and signal-processing techniques 总被引:1,自引:0,他引:1
Yuanxun Wang Hao Ling 《Microwave Theory and Techniques》1998,46(1):89-96
We present two approaches to extract the broadband multimode parameters of guided wave structures from a single-pass finite-difference time-domain (FDTD) simulation. They include a two-dimensional (2-D) Fourier transform (FT) algorithm and a super-resolution estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm. Comparison is made to show the superiority of the super-resolution approach. As a typical application, a three-line coupled microstrip structure is studied. After a single-pass FDTD simulation, broadband multimode parameters such as propagation constants, modal-field templates, and modal impedances are extracted and verified against published data obtained by the spectral-domain method. The main feature of this parameter-extraction methodology is that it decouples the computational electromagnetics engine (in this case, the FDTD simulator) from the post-processing parameter-extraction algorithm, thus providing more flexibility and connectivity among the various simulation tools 相似文献
68.
HS Wong 《Canadian Metallurgical Quarterly》1997,38(11):459-464
69.
GIS技术与微机制图 总被引:1,自引:0,他引:1
地理信息系统(GIS)随着信息社会的发展愈发显示出强大的生命力。本文简要叙述GIS的重要作用及其发展进程中涌出出来的四个设计模型,总结了运用GIS国产软件平台MAPGIS制作遥感地质构造解译图的工作步骤和技术方法。 相似文献
70.
A genetic algorithm for multiple molecular sequence alignment 总被引:1,自引:0,他引:1
MOTIVATION: Multiple molecular sequence alignment is among the most important and most challenging tasks in computational biology. The currently used alignment techniques are characterized by great computational complexity, which prevents their wider use. This research is aimed at developing a new technique for efficient multiple sequence alignment. APPROACH: The new method is based on genetic algorithms. Genetic algorithms are stochastic approaches for efficient and robust searching. By converting biomolecular sequence alignment into a problem of searching for optimal or near-optimal points in an 'alignment space', a genetic algorithm can be used to find good alignments very efficiently. RESULTS: Experiments on real data sets have shown that the average computing time of this technique may be two or three orders lower than that of a technique based on pairwise dynamic programming, while the alignment qualities are very similar. AVAILABILITY: A C program on UNIX has been written to implement the technique. It is available on request from the authors. 相似文献