全文获取类型
收费全文 | 55292篇 |
免费 | 8705篇 |
国内免费 | 5536篇 |
专业分类
电工技术 | 5088篇 |
技术理论 | 2篇 |
综合类 | 4438篇 |
化学工业 | 1865篇 |
金属工艺 | 1036篇 |
机械仪表 | 3840篇 |
建筑科学 | 1989篇 |
矿业工程 | 975篇 |
能源动力 | 673篇 |
轻工业 | 4354篇 |
水利工程 | 437篇 |
石油天然气 | 1031篇 |
武器工业 | 801篇 |
无线电 | 11878篇 |
一般工业技术 | 3366篇 |
冶金工业 | 730篇 |
原子能技术 | 505篇 |
自动化技术 | 26525篇 |
出版年
2024年 | 549篇 |
2023年 | 1546篇 |
2022年 | 2490篇 |
2021年 | 2696篇 |
2020年 | 2643篇 |
2019年 | 2077篇 |
2018年 | 1783篇 |
2017年 | 2321篇 |
2016年 | 2445篇 |
2015年 | 2782篇 |
2014年 | 4301篇 |
2013年 | 3675篇 |
2012年 | 4359篇 |
2011年 | 4737篇 |
2010年 | 3548篇 |
2009年 | 3522篇 |
2008年 | 3659篇 |
2007年 | 3963篇 |
2006年 | 3251篇 |
2005年 | 2780篇 |
2004年 | 2133篇 |
2003年 | 1787篇 |
2002年 | 1341篇 |
2001年 | 955篇 |
2000年 | 775篇 |
1999年 | 655篇 |
1998年 | 512篇 |
1997年 | 411篇 |
1996年 | 359篇 |
1995年 | 280篇 |
1994年 | 203篇 |
1993年 | 170篇 |
1992年 | 148篇 |
1991年 | 132篇 |
1990年 | 97篇 |
1989年 | 57篇 |
1988年 | 63篇 |
1987年 | 37篇 |
1986年 | 47篇 |
1985年 | 42篇 |
1984年 | 40篇 |
1983年 | 32篇 |
1982年 | 23篇 |
1981年 | 27篇 |
1980年 | 21篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 4篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
采用具有水平对称轴的横向各向同性(HTI)模型研究裂缝性油气藏,P波振幅随炮检距和方位角变化(AVOA),表现出较强的方位各向异性特征。本文基于Ruger提出的HTI介质模型的P波反射系数公式,利用由基准测线和另外两条与之呈45°、90°测线的P波反射系数的相对差异估算裂缝方位;同时引入小生境遗传算法,对基准测线和与之呈90°测线的P波反射系数差进行反演,得到了较高精度的纵、横波波速比和Thomsen各向异性参数。 相似文献
72.
在简单介绍高程系统的基础上,对影响GPS高程精度的几何水准联测误差、卫星分布不对称、星历误差、多路径误差等因素逐一进行了分析,并提出了相应的改进措施。同时,还对高程拟合使用的稳健估计方法进行了探讨。 相似文献
73.
In a change detection paradigm, a target object in a natural scene either rotated in depth, was replaced by another object token, or remained the same. Change detection performance was reliably higher when a target postcue allowed participants to restrict retrieval and comparison processes to the target object (Experiment 1). Change detection performance remained excellent when the target object was not attended at change (Experiment 2) and when a concurrent verbal working memory load minimized the possibility of verbal encoding. (Experiment 3). Together, these data demonstrate that visual representations accumulate in memory from attended objects as the eyes and attention are oriented within a scene and that change blindness derives, at least in part, from retrieval and comparison failure. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
75.
Summary This paper proposes a self-stabilizing protocol which circulates a token on a connected network in nondeterministic depth-first-search order, rooted at a special node. Starting with any initial state in which the network may have no token at all or more than one token, the protocol eventually makes the system stabilize in states having exactly one circulating token. With a slight modification to the protocol —by removing nondeterminism in the search — a depth-first-search tree on the network can be constructed. The proposed protocol runs on systems that allow parallel operations.
Shing-Tsaan Huang was born in Taiwan on September 4, 1949. He got his Ph.D. degree in 1985 from Department of Computer Science, University of Maryland at College Park. Before he pursued his Ph.D. degree, he had worked several years in the computer industry in Taiwan. Professor Huang is currently the chairman of the Department of Computer Science, Tsing Hua University, Taiwan, Republic of China. His research interests include interconnection networks, operating systems and distributed computing. He is a senior member of the IEEE Computer Society and a member of the Association for Computing Machinery.
Nian-Shing Chen was born in Taiwan on October 21, 1961. He received his Ph.D. degree in computer science from National Tsing Hua University in 1990. Dr. Chen is currently an associate professor with the Department of Information Management at Sun Yat-Sen University of Taiwan. His research interests include distributed systems, computer networks, computer viruses and expert systems. He is a member of IEEE and Phi Tau Phi honorary society.This research is supported by National Science Council of the Republic of China under the contract NSC81-0408-E-007-05 and NSC82-0408-E-007-027 相似文献
76.
In this paper, a new real-time sensor system has been developed to detect chatter in milling operations. In the developed sensor system, a pattern recognition technique based on an unsupervised neural network using the adaptive resonance theory (ART) is adopted for detection of milling chatter. The features on the cutting force spectrum are fed into the sensor system to classify the milling process with or without chatter. The experimental results indicate that the proposed sensor system can accurately detect milling chatter regardless of the variation in cutting conditions. 相似文献
77.
Akira Ishizaki Kazuhiko Takasaki Shoji Shimomura Kouichi Masaki Kanji Kitazawa 《Electrical Engineering in Japan》1996,116(5):128-137
Although brushless resolvers have been used widely as angular position transducers, they are expensive due to their intricate construction, involving a rotary transformer to supply the exciting coils wound on the rotor poles with the current. It is shown theoretically in this paper that the resolver without rotary transformer or brushes can be realized by simple construction, which consists of the stator core with both 4-poles exciting windings and 2-poles output ones and the rotor core carrying no windings. In this resolver the rotor core has minimum gap at one side and a maximum gap at another side of the diameter. It is characterized by an outer surface form that makes the fluctuation part of gap permeance very in proportion to cos θ, where θ represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the aforementioned gap permeance variation is also shown. It has been confirmed not only by simulation but also experiment that the 2-phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy. 相似文献
78.
形态学边缘检测的新算法及其应用 总被引:3,自引:0,他引:3
刘岚岚 《红外与毫米波学报》1998,17(5):386-390
提出了一种基于数学形态学的边缘检测的所算法,该算法具有简便和灵活可编程控制等优点,比原来主算法更国完善,在实际应用中有着很好的前景,并给出了实验结果。 相似文献
79.
陈明志 《数字社区&智能家居》2006,1(12):159-160
本文对数字图像中几种具有代表性的边缘检测算子进行了理论分析,并通过VC编程实验,对各种算法进行实现,通过比较得出了各自的优缺点和适用范围。 相似文献
80.
陈希武 《中国计量学院学报》1992,(1)
本文提出并研制成补偿式光纤F-P干涉仪信号处理系统,提出了用来测量微小位移信号的三种方法及电路,即透射峰时间间隔测量法、光脉冲基波幅度测量法(精密整流法)、鉴相法。测试结果表明:时间间隔测量法,它的最大灵敏度达到0.26纳米/微秒;精密整流法,最大灵敏度为2.38纳米/伏特。 相似文献