全文获取类型
收费全文 | 30374篇 |
免费 | 5810篇 |
国内免费 | 1583篇 |
专业分类
电工技术 | 3374篇 |
技术理论 | 2篇 |
综合类 | 2168篇 |
化学工业 | 2306篇 |
金属工艺 | 10547篇 |
机械仪表 | 3066篇 |
建筑科学 | 1442篇 |
矿业工程 | 452篇 |
能源动力 | 1091篇 |
轻工业 | 459篇 |
水利工程 | 273篇 |
石油天然气 | 1428篇 |
武器工业 | 281篇 |
无线电 | 2414篇 |
一般工业技术 | 4169篇 |
冶金工业 | 980篇 |
原子能技术 | 211篇 |
自动化技术 | 3104篇 |
出版年
2024年 | 119篇 |
2023年 | 574篇 |
2022年 | 849篇 |
2021年 | 1023篇 |
2020年 | 1227篇 |
2019年 | 1160篇 |
2018年 | 1092篇 |
2017年 | 1488篇 |
2016年 | 1498篇 |
2015年 | 1399篇 |
2014年 | 2062篇 |
2013年 | 2400篇 |
2012年 | 2206篇 |
2011年 | 2358篇 |
2010年 | 1772篇 |
2009年 | 1656篇 |
2008年 | 1564篇 |
2007年 | 2065篇 |
2006年 | 1974篇 |
2005年 | 1580篇 |
2004年 | 1420篇 |
2003年 | 1147篇 |
2002年 | 975篇 |
2001年 | 828篇 |
2000年 | 690篇 |
1999年 | 536篇 |
1998年 | 407篇 |
1997年 | 390篇 |
1996年 | 330篇 |
1995年 | 245篇 |
1994年 | 196篇 |
1993年 | 125篇 |
1992年 | 100篇 |
1991年 | 91篇 |
1990年 | 64篇 |
1989年 | 71篇 |
1988年 | 28篇 |
1987年 | 18篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
81.
How to Control Robots Interacting with Dynamic Environment 总被引:7,自引:0,他引:7
Miomir Vukobratović 《Journal of Intelligent and Robotic Systems》1997,19(2):119-152
The goal of this paper is to shed light on the control problem of constrained robot motion from the aspect of the dynamical nature of the environment with which the robot is in contact. Therefore, the criticism of traditional hybrid control which allows position/force feedback loops to split into independent control with respect to position and force, is not the main point we want to make. Reference to the papers written by the founders of hybrid control and their numerous followers served only to better understand the reason and motivation for suggesting a different approach to control of robots interacting with environment.The paper has a predominantly review character, based on recently published work. It also contains some new, unpublished results in the framework of the unified approach to the position/force control of robots, proposed by the present author and his co-workers. By pointing to the possibility of introducing an environment dynamics in the contact tasks of the machining type, the author emphasizes that the proposed dynamically interactive control can be applied to a completely different class of tasks, in which a contact is made between the system (constructions or structure) and very specific kinds of dynamic environments. 相似文献
82.
An investigation of pore cracking in titanium welds 总被引:1,自引:0,他引:1
T. Khaled 《Journal of Materials Engineering and Performance》1994,3(1):21-36
Two welded Ti-6A1-4V pressure vessels leaked prematurely in service. The leaks were caused by cracks emanating from weld porosity.
The cracks originated during fabrication, with subsequent growth in service leading to the formation of the leak paths. Pore
cracking is thought to be caused by a mechanism that involves both sustained-load and cyclic contributions, with the former
being the more prominent. It is shown that the tendency for cracking is influenced by pore position and that pore size is
not a deciding factor in that regard. The factors that govern pore cracking are discussed, and the possible role of interstitial
embrittlement is assessed. 相似文献
83.
含钇奥氏体基堆焊焊条堆焊层研究 总被引:1,自引:0,他引:1
针对高温、磨损、热疲劳工况下服役零件的失效,研制了一种含稀土元素钇的奥氏体基沉淀强化型堆焊焊条,并对堆焊层组织与性能进行了较系统的研究。 相似文献
84.
N. JostJ. Karger-Kocsis 《Polymer》2002,43(4):1383-1389
Curing kinetics of a vinylester-urethane hybrid (VEUH) resin consisting of vinylester resin (VE) diluted in styrene and novolac type polyisocyanate (NPI) have been studied by differential scanning calorimetry (DSC). As VEUH is crosslinked via free radical polymerisation between the vinyl functions of styrene and VE, and polyaddition reaction between the secondary -OH groups of VE and -NCO of NPI, it was necessary to study these reactions separately. This was achieved by studying the curing with and without incorporating the NPI. The curing reaction was monitored by measuring the heat of reaction under isothermal and dynamic temperature conditions. Models describing the curing were developed, which are in good agreement with the experiments. A comparison between the curing of the VEUH and the VE resin without NPI leads to the conclusion that the curing of the VEUH as accessed by DSC is dominated by the radical polymerisation of styrene with VE although the two reactions are not time separated. 相似文献
85.
86.
87.
本文通过焊接试验对奥氏体不锈钢绕带容器环板与绕带焊接工艺进行了研究分析,并得出了合理的焊接方法和工艺参数。 相似文献
88.
提出一种将同步相量测量单元(PMU)的直接电压相量量测变换为间接支路电流量测,并与监控与数据采集(SCADA)量测量一起进行混合迭代的非线性状态估计方法。对构造等效电流修正量而带来的间接量测误差进行了详细和定量的分析,并对该混合估计算法的精度进行了定性分析和定量计算。理论分析和算例表明,该方法可以获得较高的估计精度,在收敛次数和滤波效果上也有所改进。 相似文献
89.
P. Ravirajan S.A. Haque J.R. Durrant D.D.C. Bradley J. Nelson 《Advanced functional materials》2005,15(4):609-618
We report a study of the effects of polymer optoelectronic properties on the performance of photovoltaic devices consisting of nanocrystalline TiO2 and a conjugated polymer. Three different poly(2‐methoxy‐5‐(2′‐ethylhexoxy)‐1,4‐phenylenevinylene) (MEH‐PPV)‐based polymers and a fluorene–bithiophene copolymer are compared. We use photoluminescence quenching, time‐of‐flight mobility measurements, and optical spectroscopy to characterize the exciton‐transport, charge‐transport, and light‐harvesting properties, respectively, of the polymers, and correlate these material properties with photovoltaic‐device performance. We find that photocurrent is primarily limited by the photogeneration rate and by the quality of the interfaces, rather than by hole transport in the polymer. We have also studied the photovoltaic performance of these TiO2/polymer devices as a function of the fabrication route and device design. Including a dip‐coating step before spin‐coating the polymer leads to excellent polymer penetration into highly structured TiO2 networks, as was confirmed through transient optical measurements of the photoinduced charge‐transfer yield and recombination kinetics. Device performance is further improved for all material combinations studied, by introducing a layer of poly(ethylene dioxythiophene) (PEDOT) doped with poly(styrene sulfonic acid) (PSS) under the top contact. Optimized devices incorporating the additional dip‐coated and PEDOT:PSS layers produced a short‐circuit current density of about 1 mA cm–2, a fill factor of 0.50, and an open‐circuit voltage of 0.86 V under simulated AM 1.5 illumination (100 mW cm–2, 1 sun). The corresponding power conversion efficiency under 1 sun was ≥ 0.4 %. 相似文献
90.
自动焊技术在涩宁兰输气管道X70钢试验段上的应用 总被引:6,自引:0,他引:6
通过涩宁兰输气管道X70钢试验段的施工,进一步探索和完善自动焊接技术在高强钢管道焊接中的应用。文章介绍了该试验段施工的焊接设备、焊材和焊接工艺,可为同类焊接工程提供借鉴。 相似文献