全文获取类型
收费全文 | 73060篇 |
免费 | 6663篇 |
国内免费 | 3620篇 |
专业分类
电工技术 | 4553篇 |
技术理论 | 7篇 |
综合类 | 5577篇 |
化学工业 | 11978篇 |
金属工艺 | 3694篇 |
机械仪表 | 4537篇 |
建筑科学 | 6514篇 |
矿业工程 | 1848篇 |
能源动力 | 1944篇 |
轻工业 | 7195篇 |
水利工程 | 1439篇 |
石油天然气 | 3345篇 |
武器工业 | 631篇 |
无线电 | 8362篇 |
一般工业技术 | 8015篇 |
冶金工业 | 2874篇 |
原子能技术 | 944篇 |
自动化技术 | 9886篇 |
出版年
2024年 | 352篇 |
2023年 | 1231篇 |
2022年 | 2274篇 |
2021年 | 3085篇 |
2020年 | 2295篇 |
2019年 | 1871篇 |
2018年 | 2108篇 |
2017年 | 2358篇 |
2016年 | 2186篇 |
2015年 | 2898篇 |
2014年 | 3720篇 |
2013年 | 4421篇 |
2012年 | 5050篇 |
2011年 | 5437篇 |
2010年 | 4927篇 |
2009年 | 4724篇 |
2008年 | 4621篇 |
2007年 | 4268篇 |
2006年 | 4081篇 |
2005年 | 3481篇 |
2004年 | 2385篇 |
2003年 | 1976篇 |
2002年 | 1925篇 |
2001年 | 1662篇 |
2000年 | 1534篇 |
1999年 | 1586篇 |
1998年 | 1214篇 |
1997年 | 1065篇 |
1996年 | 981篇 |
1995年 | 830篇 |
1994年 | 641篇 |
1993年 | 457篇 |
1992年 | 378篇 |
1991年 | 271篇 |
1990年 | 196篇 |
1989年 | 186篇 |
1988年 | 150篇 |
1987年 | 88篇 |
1986年 | 93篇 |
1985年 | 48篇 |
1984年 | 36篇 |
1983年 | 27篇 |
1982年 | 23篇 |
1981年 | 23篇 |
1980年 | 28篇 |
1979年 | 18篇 |
1976年 | 7篇 |
1962年 | 43篇 |
1961年 | 39篇 |
1960年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
随着计算机网络技术的发展,远程教学系统的结构发生了重大的变化,逐步由原来的客户机/服务器(C/S)结构转变为基于Internet的浏览器/服务器(B/S)结构。本文提出了基于CORBA技术的B/S结构系统模型。分析了其运行过程,并与传统的结构进行了比较,指明了其优越性。在本文的结尾。指出了使用这种技术的一个具体例子。 相似文献
62.
声波测井换能器的激发响应由换能器振动时所表现出来的动态阻抗和激发电路参数决定。而换能器的动态(阻抗)参数随压电晶体及其装配方式(力学边界条件)改变。为了测量换能器动态参数的影响,采用声波测井仪器常用的压电晶体和升压变压器,通过改变激发脉冲宽度和直流电压进行了实验,结果发现:在换能器两端的瞬态响应中,一共有三个二阶网络响应,分别对应于不同的频率。最低的一个影响声波测井波形的基线、与换能器主频接近的一个决定激发效率以及电路与压电晶体之间的匹配关系,是激发电路设计中比较关键的,其参数可以通过导纳圆测量仪器得到。 相似文献
63.
64.
房家贵 《石油化工设备技术》2006,27(1):1-5
文章介绍了近年来在催化裂化装置上应用的新设备、新技术,如BY型旋风分离器、BSX型旋分式三级旋风分离器、上下拱型三级旋风分离器、下拱型三级旋风分离器、SHS“自蔓延”技术、SWY外取热器、BWJ型喷嘴、自流浇注料、Actehem高耐磨衬里、弓形钢丝纤维、侧拉环锚固钉、分体可拆人孔等的结构特点及实际应用情况。 相似文献
65.
66.
B.‐J. Fang Y.‐J. Shan H.‐Q. Xu H.‐S. Luo Z.‐W. Yin 《Advanced functional materials》2004,14(2):169-173
Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT91/9) single crystals were grown by two methods: from solution using PbO as a self‐fluxing agent (SC method) and directly from the melt without fluxing (MC method). In both growth methods, an allomeric Pb[(Mg1/3‐Nb2/3)0.69Ti0.31]O3 (PMNT69/31) single crystal was used as a seed. X‐ray diffraction patterns of ground crystals showed that phase‐pure perovskite PZNT91/9 single crystals were successfully fabricated by the above two methods. The composition of the crystals obtained by both the SC and MC methods was analyzed using X‐ray fluorescence, which confirmed that the crystal composition is close to the nominal value, although volatilization of PbO and segregation during crystal growth are inevitable. The MC PZNT91/9 crystals exhibit excellent piezoelectric properties, with the piezoelectric constant, d33, in the range of 1800–2200 pC N–1. This value is comparable to that of the SC crystals. However, the MC crystals show an abnormal dielectric behavior. In contrast with the SC crystals, in the MC crystals a much broader dielectric peak appears in the dielectric response curves, accompanied by a much lower peak temperature of around 105 °C. Furthermore, frequency dispersion is apparent over a much wider temperature range (even more apparent than in pure relaxors), where a large, i.e., about 70 °C, full width at half maximum (FWHM) for the dielectric peaks is observed in the dielectric response. It is speculated that such an unusual phenomenon correlates with defects, microinhomogeneities, and polar regions in the as‐grown MC crystals. The origins of this abnormality have not been interpreted in detail until now. However, optical observation of the domain structure confirms that both the SC and MC crystals possess complex structural states. 相似文献
67.
68.
A decision support system for interactive decision making - Part II: analysis and output interpretation 总被引:2,自引:0,他引:2
Liping Fang K.W. Hipel D.M. Kilgour Xiaoyong Peng 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2003,33(1):56-66
For pt.I see ibid., p.42-55 (2003). The development of a comprehensive decision support system, GMCR II, for the systematic study of real-world interactive decision problems is presented. The companion paper (Part I), discusses how GMCR II elicits, stores, and manages conflict models; here (Part II), the focus is on GMCR IIs analysis and output interpretation subsystems. Specifically, this paper describes the powerful and efficient analysis engine contained in GMCR II, its informative output presentation and interpretation facilities, and a number of follow-up analyses. Furthermore, an illustrative case study is used to demonstrate how GMCR II can be conveniently applied in practice. 相似文献
69.
W. Wang J. Dai J. Tang D.-T. Jiang Y. Chen J. Fang J. He W. Zhou L. Spinu 《Journal of Superconductivity》2003,16(1):155-157
Ball-milling method was applied to dissolve Fe into titanium dioxide (TiO2). X-ray diffraction indicated the starting anatase changed to a rutile-type structure with oxygen deficiency after ball milling. Transmission electron microscopy and X-ray absorption experiments were conducted to examine the possible existence of magnetic impurities in the ball-milled powders after they were leached in HCl solutions. Temperature dependence of the resistivity shows semiconducting behavior and the magnetic hysteresis loops at 5 and 300 K exhibit ferromagnetic characteristics. Fe-doped TiO2 films were also prepared by pulsed laser deposition. The magnetic properties of the films are discussed. 相似文献
70.
Field Static Load Test on Kao-Ping-Hsi Cable-Stayed Bridge 总被引:1,自引:0,他引:1
Field load testing is an effective method for understanding the behavior and fundamental characteristics of a cable-stayed bridge. This paper presents the results of field static load tests on the Kao-Ping-Hsi cable-stayed bridge, the longest cable-stayed bridge in Taiwan, before it was open to traffic. A total of 40 loading cases, including the unit and distributed bending and torsion loading effects, were conducted to investigate the bridge behavior. The atmospheric temperature effect on the variations of the main girder deflections was also monitored. The results of static load testing include the main girder deflections, the flexural strains of the prestressed concrete girder, and the variations of the cable forces. A three-dimensional finite-element model was developed. The results show that the bridge under the planned load test conditions has linear superposition characteristics and the analytical model shows a very good agreement with the bridge responses. Further discussion of deflection and cable forces of the design specifications for a cable-stayed bridge is also presented. 相似文献