全文获取类型
收费全文 | 23604篇 |
免费 | 2825篇 |
国内免费 | 1915篇 |
专业分类
电工技术 | 1832篇 |
综合类 | 1792篇 |
化学工业 | 5134篇 |
金属工艺 | 2046篇 |
机械仪表 | 2066篇 |
建筑科学 | 1019篇 |
矿业工程 | 683篇 |
能源动力 | 865篇 |
轻工业 | 1353篇 |
水利工程 | 282篇 |
石油天然气 | 529篇 |
武器工业 | 229篇 |
无线电 | 2614篇 |
一般工业技术 | 3731篇 |
冶金工业 | 1180篇 |
原子能技术 | 1416篇 |
自动化技术 | 1573篇 |
出版年
2024年 | 100篇 |
2023年 | 385篇 |
2022年 | 619篇 |
2021年 | 796篇 |
2020年 | 917篇 |
2019年 | 856篇 |
2018年 | 850篇 |
2017年 | 1017篇 |
2016年 | 962篇 |
2015年 | 921篇 |
2014年 | 1304篇 |
2013年 | 1408篇 |
2012年 | 1686篇 |
2011年 | 1764篇 |
2010年 | 1253篇 |
2009年 | 1258篇 |
2008年 | 1155篇 |
2007年 | 1532篇 |
2006年 | 1415篇 |
2005年 | 1161篇 |
2004年 | 1054篇 |
2003年 | 972篇 |
2002年 | 835篇 |
2001年 | 691篇 |
2000年 | 593篇 |
1999年 | 452篇 |
1998年 | 370篇 |
1997年 | 316篇 |
1996年 | 296篇 |
1995年 | 228篇 |
1994年 | 238篇 |
1993年 | 149篇 |
1992年 | 162篇 |
1991年 | 116篇 |
1990年 | 97篇 |
1989年 | 75篇 |
1988年 | 76篇 |
1987年 | 52篇 |
1986年 | 55篇 |
1985年 | 34篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1978年 | 6篇 |
1974年 | 5篇 |
1963年 | 4篇 |
1959年 | 11篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Decentralized adaptive coordinated control of multiple robot arms without using a force sensor 总被引:1,自引:0,他引:1
Haruhisa Kawasaki Author Vitae Satoshi Ueki Author Vitae Author Vitae 《Automatica》2006,42(3):481-488
This paper presents a distributed adaptive coordinated control method for multiple robot arms grasping a common object. The cases of rigid contact and rolling contact are analyzed. In the proposed controller, the dynamic parameters of both object and robot arms are estimated adaptively. The desired motions of the robot arms are generated by an estimated object reference model. The control method requires only the measurements of the positions and velocities of the object and robot arms, but not the measurements of forces and moments at contact points. The asymptotic convergence of trajectory is proven by the Lyapunov-like Lemma. Experiments involving two robot arms handling a common object are shown. 相似文献
52.
D. Wang J. S. Jiang W. H. Zhang 《International journal for numerical methods in engineering》2004,61(10):1584-1602
In this paper, the position optimization of simple supports is implemented to maximize the fundamental frequency of a beam or plate structure. Both elastic and rigid supports are taken into account. First, the frequency sensitivity with respect to the movement of a simple support is derived using the discrete method. By means of the shape functions of the finite element method, closed‐form sensitivity formulations are developed straightforwardly. Then, a heuristic approach, called evolutionary shift method, is presented for optimizing support positions with a fixed grid mesh scheme. Based on the design sensitivity analysis, the support with the highest efficiency is shifted in priority along the elementary edges with the interval (step) of the elementary size. To facilitate the convergence of the process, the interpolation technique is employed to evaluate the solution more accurately. Finally, three numerical examples are presented to demonstrate the validity of the sensitivity analysis and the effectiveness of the optimization method. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
53.
Friendship affects individual and organizational well-being through direct relations, social positions, and complex network structures. In this study, the authors use longitudinal data from 2 groups of master's of business administration students to increase understanding of how friendship networks develop. The authors propose and test a dynamic model in which attribute similarity facilitates dyadic friendship ties, as well as similar network centrality and social position; early friendship increases later similarity in structural position and centrality; and early structural similarity enhances the likelihood of future friendship. Findings largely supported the model, demonstrating how homophily and early social contacts can jointly shape maturing friendship networks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
连铸钢坯质量的原位统计分布分析研究 总被引:14,自引:0,他引:14
采用原位统计分布分析技术得到与样品原位置相对应的数以万计原始信号并对其进行系统解析,实现不同质量连铸钢坯试样的疏松度、均匀度以及夹杂物含量的定量表征。准确计算了连铸钢坯试样疏松度、碳元素的最大偏析度。提出铸坯各原位置成分含量的权重比率方法用以表征材料的均匀度,并提供了统计分布允许差范围内(C0±R)所占权重比率以及权重比率为95%置信度时,中位值置信扩展率(K)等2种判断模式。该方法以测量信息的原始性、原位性及统计性为特征,反映了连铸钢坯较大尺度范围内各化学组成及其形态的定量统计分布规律。采用上述方法可以 相似文献
55.
端电压比较法直接寻找无刷直流电动机换相点及其斩波调速 总被引:4,自引:0,他引:4
提供了一种利用端电压比较结合软件算法直接寻找直流无刷无位置传感器电动机换相点的方案,解决了直流无刷无位置传感器电动机控制的关键问题-转子位置检测,并以单片机PIC16C72为核心构成先进的数字控制系统,实现了软件斩波调速。 相似文献
56.
采用水力模型研究方法 ,针对马钢 2 0t转炉进行溅渣护炉冷态模拟试验 ,得出最佳工艺参数为 :枪位 1680mm ,氮气流量为 110 0 0m3/h ,大流渣量 ,渣粘度适中。此外 ,在满足炼钢生产的条件下 ,采用夹角为 13°的喷头溅渣效果好 相似文献
57.
Effect of Rare Earth Element Cerium on Mechanical Properties and Morphology of TiN Coating Prepared by Arc Ion Plating 总被引:7,自引:0,他引:7
TiN coatings were deposited on polished substrates of W18Cr4V high speed steel by means of vacuum arc ion plating. The effect of cerium on adhesion between TiN coating and substrate was studied. The microstructures and composition of TiN coatings were also investigated by means of scanning electron microscope (SEM), Auger electron spectroscopy (AES), and X-ray diffraction (XRD) technique. It was found that cerium is an effective modifying agent and the addition of suitable amount of cerium to TiN coatings can produce relatively excellent properties such as micro-hardness, wear resistance, oxidation resistance and porosity. The experimental results show that the added cerium in TiN coatings makesa contribution to form the preferred direction along with a (111 ) or (222) close packed face, which may be one of the reasons that improves some properties mentioned above. 相似文献
58.
A remarkable nonlinearity has been observed for electric transport in K-TCNQ (potassium tetracyanoquinodimethane) quasi-one-dimensional
conductor. The negative differential resistance region appears afterV
m (turn over voltage), beyond which voltage goes down with increase of current. A possible mechanism is discussed in terms
of dynamics of charged solitons and domain walls in one-dimensional molecular stacks of these types of crystals. 相似文献
59.
聚苯醚磺酸锂/共聚醚复合物的离子导电性研究 总被引:1,自引:0,他引:1
合成了3种不同磺化度的聚苯醚磺酸锂(SPPOLi)与P(MEO16-AM)/SPPOLi复合物。研究了复合物的离子导电性与磺化度,组成比及增塑剂含量的关系。含40%(mass)增塑剂的复合物具有单离子导电特征,锂离子迁移数高达0.97,室温电导率达2×10-5S/cm。 相似文献
60.
A. Andreev L. Prahov M. Gabrovska A. Eliyas V. Ivanova 《Applied catalysis. B, Environmental》1996,8(4):365-373
The catalytic activity of a wide range of transition metal oxides in oxidation of sulphide ions by air in aqueous medium was studied. Some specific features of the reaction mechanism on some of the studied oxides were considered. The transition metal oxides are promising catalysts for practical application. Some of these oxides will allow the preparation of catalysts possessing activity comparable to that of the cobalt phthalocyanine based catalysts, popular in industrial practice. 相似文献